Chapter 2. Configuring a Streams for Apache Kafka deployment

Configure your Streams for Apache Kafka deployment using custom resources. Streams for Apache Kafka provides example configuration files, which can serve as a starting point when building your own Kafka component configuration for deployment.

Note

Labels applied to a custom resource are also applied to the OpenShift resources making up its cluster. This provides a convenient mechanism for resources to be labeled as required.

Monitoring a Streams for Apache Kafka deployment

You can use Prometheus and Grafana to monitor your Streams for Apache Kafka deployment. For more information, see Introducing metrics to Kafka.

2.1. Kafka cluster configuration

This section describes how to configure a Kafka deployment in your AMQ Streams cluster. A Kafka cluster is deployed with a ZooKeeper cluster. The deployment can also include the Topic Operator and User Operator, which manage Kafka topics and users.

You configure Kafka using the Kafka resource. Configuration options are also available for ZooKeeper and the Entity Operator within the Kafka resource. The Entity Operator comprises the Topic Operator and User Operator.

The full schema of the Kafka resource is described in the Section 13.2.1, “Kafka schema reference”. For more information about Apache Kafka, see the Apache Kafka documentation.

Listener configuration

You configure listeners for connecting clients to Kafka brokers. For more information on configuring listeners for connecting brokers, see Listener configuration.

Authorizing access to Kafka

You can configure your Kafka cluster to allow or decline actions executed by users. For more information, see Securing access to Kafka brokers.

Managing TLS certificates

When deploying Kafka, the Cluster Operator automatically sets up and renews TLS certificates to enable encryption and authentication within your cluster. If required, you can manually renew the cluster and client CA certificates before their renewal period ends. You can also replace the keys used by the cluster and client CA certificates. For more information, see Renewing CA certificates manually and Replacing private keys.

2.1.1. Configuring Kafka

Use the properties of the Kafka resource to configure your Kafka deployment.

As well as configuring Kafka, you can add configuration for ZooKeeper and the AMQ Streams Operators. Common configuration properties, such as logging and healthchecks, are configured independently for each component.

This procedure shows only some of the possible configuration options, but those that are particularly important include:

  • Resource requests (CPU / Memory)
  • JVM options for maximum and minimum memory allocation
  • Listeners (and authentication of clients)
  • Authentication
  • Storage
  • Rack awareness
  • Metrics
  • Cruise Control for cluster rebalancing

Kafka versions

The inter.broker.protocol.version property for the Kafka config must be the version supported by the specified Kafka version (spec.kafka.version). The property represents the version of Kafka protocol used in a Kafka cluster.

From Kafka 3.0.0, when the inter.broker.protocol.version is set to 3.0 or higher, the log.message.format.version option is ignored and doesn’t need to be set.

An update to the inter.broker.protocol.version is required when upgrading your Kafka version. For more information, see Upgrading Kafka.

Prerequisites

  • An OpenShift cluster
  • A running Cluster Operator

See the Deploying and Upgrading AMQ Streams on OpenShift guide for instructions on deploying a:

Procedure

  1. Edit the spec properties for the Kafka resource.

    The properties you can configure are shown in this example configuration:

    apiVersion: kafka.strimzi.io/v1beta2
    kind: Kafka
    metadata:
      name: my-cluster
    spec:
      kafka:
        replicas: 3 1
        version: 3.1.0 2
        logging: 3
          type: inline
          loggers:
            kafka.root.logger.level: "INFO"
        resources: 4
          requests:
            memory: 64Gi
            cpu: "8"
          limits:
            memory: 64Gi
            cpu: "12"
        readinessProbe: 5
          initialDelaySeconds: 15
          timeoutSeconds: 5
        livenessProbe:
          initialDelaySeconds: 15
          timeoutSeconds: 5
        jvmOptions: 6
          -Xms: 8192m
          -Xmx: 8192m
        image: my-org/my-image:latest 7
        listeners: 8
          - name: plain 9
            port: 9092 10
            type: internal 11
            tls: false 12
            configuration:
              useServiceDnsDomain: true 13
          - name: tls
            port: 9093
            type: internal
            tls: true
            authentication: 14
              type: tls
          - name: external 15
            port: 9094
            type: route
            tls: true
            configuration:
              brokerCertChainAndKey: 16
                secretName: my-secret
                certificate: my-certificate.crt
                key: my-key.key
        authorization: 17
          type: simple
        config: 18
          auto.create.topics.enable: "false"
          offsets.topic.replication.factor: 3
          transaction.state.log.replication.factor: 3
          transaction.state.log.min.isr: 2
          default.replication.factor: 3
          min.insync.replicas: 2
          inter.broker.protocol.version: "3.1"
          ssl.cipher.suites: "TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384" 19
          ssl.enabled.protocols: "TLSv1.2"
          ssl.protocol: "TLSv1.2"
        storage: 20
          type: persistent-claim 21
          size: 10000Gi 22
        rack: 23
          topologyKey: topology.kubernetes.io/zone
        metricsConfig: 24
          type: jmxPrometheusExporter
          valueFrom:
            configMapKeyRef: 25
              name: my-config-map
              key: my-key
        # ...
      zookeeper: 26
        replicas: 3 27
        logging: 28
          type: inline
          loggers:
            zookeeper.root.logger: "INFO"
        resources:
          requests:
            memory: 8Gi
            cpu: "2"
          limits:
            memory: 8Gi
            cpu: "2"
        jvmOptions:
          -Xms: 4096m
          -Xmx: 4096m
        storage:
          type: persistent-claim
          size: 1000Gi
        metricsConfig:
          # ...
      entityOperator: 29
        tlsSidecar: 30
          resources:
            requests:
              cpu: 200m
              memory: 64Mi
            limits:
              cpu: 500m
              memory: 128Mi
        topicOperator:
          watchedNamespace: my-topic-namespace
          reconciliationIntervalSeconds: 60
          logging: 31
            type: inline
            loggers:
              rootLogger.level: "INFO"
          resources:
            requests:
              memory: 512Mi
              cpu: "1"
            limits:
              memory: 512Mi
              cpu: "1"
        userOperator:
          watchedNamespace: my-topic-namespace
          reconciliationIntervalSeconds: 60
          logging: 32
            type: inline
            loggers:
              rootLogger.level: INFO
          resources:
            requests:
              memory: 512Mi
              cpu: "1"
            limits:
              memory: 512Mi
              cpu: "1"
      kafkaExporter: 33
        # ...
      cruiseControl: 34
        # ...
        tlsSidecar: 35
        # ...
    1
    The number of replica nodes. If your cluster already has topics defined, you can scale clusters.
    2
    Kafka version, which can be changed to a supported version by following the upgrade procedure.
    3
    Specified Kafka loggers and log levels added directly (inline) or indirectly (external) through a ConfigMap. A custom ConfigMap must be placed under the log4j.properties key. For the Kafka kafka.root.logger.level logger, you can set the log level to INFO, ERROR, WARN, TRACE, DEBUG, FATAL or OFF.
    4
    Requests for reservation of supported resources, currently cpu and memory, and limits to specify the maximum resources that can be consumed.
    5
    Healthchecks to know when to restart a container (liveness) and when a container can accept traffic (readiness).
    6
    JVM configuration options to optimize performance for the Virtual Machine (VM) running Kafka.
    7
    ADVANCED OPTION: Container image configuration, which is recommended only in special situations.
    8
    Listeners configure how clients connect to the Kafka cluster via bootstrap addresses. Listeners are configured as internal or external listeners for connection from inside or outside the OpenShift cluster.
    9
    Name to identify the listener. Must be unique within the Kafka cluster.
    10
    Port number used by the listener inside Kafka. The port number has to be unique within a given Kafka cluster. Allowed port numbers are 9092 and higher with the exception of ports 9404 and 9999, which are already used for Prometheus and JMX. Depending on the listener type, the port number might not be the same as the port number that connects Kafka clients.
    11
    Listener type specified as internal, or for external listeners, as route, loadbalancer, nodeport or ingress.
    12
    Enables TLS encryption for each listener. Default is false. TLS encryption is not required for route listeners.
    13
    Defines whether the fully-qualified DNS names including the cluster service suffix (usually .cluster.local) are assigned.
    14
    15
    16
    Optional configuration for a Kafka listener certificate managed by an external Certificate Authority. The brokerCertChainAndKey specifies a Secret that contains a server certificate and a private key. You can configure Kafka listener certificates on any listener with enabled TLS encryption.
    17
    Authorization enables simple, OAUTH 2.0, or OPA authorization on the Kafka broker. Simple authorization uses the AclAuthorizer Kafka plugin.
    18
    19
    20
    Storage is configured as ephemeral, persistent-claim or jbod.
    21
    22
    Persistent storage has additional configuration options, such as a storage id and class for dynamic volume provisioning.
    23
    Rack awareness is configured to spread replicas across different racks. A topologykey must match the label of a cluster node.
    24
    Prometheus metrics enabled. In this example, metrics are configured for the Prometheus JMX Exporter (the default metrics exporter).
    25
    Prometheus rules for exporting metrics to a Grafana dashboard through the Prometheus JMX Exporter, which are enabled by referencing a ConfigMap containing configuration for the Prometheus JMX exporter. You can enable metrics without further configuration using a reference to a ConfigMap containing an empty file under metricsConfig.valueFrom.configMapKeyRef.key.
    26
    ZooKeeper-specific configuration, which contains properties similar to the Kafka configuration.
    27
    The number of ZooKeeper nodes. ZooKeeper clusters or ensembles usually run with an odd number of nodes, typically three, five, or seven. The majority of nodes must be available in order to maintain an effective quorum. If the ZooKeeper cluster loses its quorum, it will stop responding to clients and the Kafka brokers will stop working. Having a stable and highly available ZooKeeper cluster is crucial for AMQ Streams.
    28
    29
    30
    Entity Operator TLS sidecar configuration. Entity Operator uses the TLS sidecar for secure communication with ZooKeeper.
    31
    Specified Topic Operator loggers and log levels. This example uses inline logging.
    32
    33
    Kafka Exporter configuration. Kafka Exporter is an optional component for extracting metrics data from Kafka brokers, in particular consumer lag data.
    34
    Optional configuration for Cruise Control, which is used to rebalance the Kafka cluster.
    35
    Cruise Control TLS sidecar configuration. Cruise Control uses the TLS sidecar for secure communication with ZooKeeper.
  2. Create or update the resource:

    oc apply -f <kafka_configuration_file>

2.1.2. Configuring the Entity Operator

The Entity Operator is responsible for managing Kafka-related entities in a running Kafka cluster.

The Entity Operator comprises the:

  • Topic Operator to manage Kafka topics
  • User Operator to manage Kafka users

Through Kafka resource configuration, the Cluster Operator can deploy the Entity Operator, including one or both operators, when deploying a Kafka cluster.

Note

When deployed, the Entity Operator contains the operators according to the deployment configuration.

The operators are automatically configured to manage the topics and users of the Kafka cluster.

2.1.2.1. Entity Operator configuration properties

Use the entityOperator property in Kafka.spec to configure the Entity Operator.

The entityOperator property supports several sub-properties:

  • tlsSidecar
  • topicOperator
  • userOperator
  • template

The tlsSidecar property contains the configuration of the TLS sidecar container, which is used to communicate with ZooKeeper.

The template property contains the configuration of the Entity Operator pod, such as labels, annotations, affinity, and tolerations. For more information on configuring templates, see Section 2.6, “Customizing OpenShift resources”.

The topicOperator property contains the configuration of the Topic Operator. When this option is missing, the Entity Operator is deployed without the Topic Operator.

The userOperator property contains the configuration of the User Operator. When this option is missing, the Entity Operator is deployed without the User Operator.

For more information on the properties used to configure the Entity Operator, see the EntityUserOperatorSpec schema reference.

Example of basic configuration enabling both operators

apiVersion: kafka.strimzi.io/v1beta2
kind: Kafka
metadata:
  name: my-cluster
spec:
  kafka:
    # ...
  zookeeper:
    # ...
  entityOperator:
    topicOperator: {}
    userOperator: {}

If an empty object ({}) is used for the topicOperator and userOperator, all properties use their default values.

When both topicOperator and userOperator properties are missing, the Entity Operator is not deployed.

2.1.2.2. Topic Operator configuration properties

Topic Operator deployment can be configured using additional options inside the topicOperator object. The following properties are supported:

watchedNamespace
The OpenShift namespace in which the topic operator watches for KafkaTopics. Default is the namespace where the Kafka cluster is deployed.
reconciliationIntervalSeconds
The interval between periodic reconciliations in seconds. Default 120.
zookeeperSessionTimeoutSeconds
The ZooKeeper session timeout in seconds. Default 18.
topicMetadataMaxAttempts
The number of attempts at getting topic metadata from Kafka. The time between each attempt is defined as an exponential back-off. Consider increasing this value when topic creation might take more time due to the number of partitions or replicas. Default 6.
image
The image property can be used to configure the container image which will be used. For more details about configuring custom container images, see Section 13.1.6, “image.
resources
The resources property configures the amount of resources allocated to the Topic Operator. For more details about resource request and limit configuration, see Section 13.1.5, “resources.
logging
The logging property configures the logging of the Topic Operator. For more details, see Section 13.2.45.1, “logging.

Example Topic Operator configuration

apiVersion: kafka.strimzi.io/v1beta2
kind: Kafka
metadata:
  name: my-cluster
spec:
  kafka:
    # ...
  zookeeper:
    # ...
  entityOperator:
    # ...
    topicOperator:
      watchedNamespace: my-topic-namespace
      reconciliationIntervalSeconds: 60
    # ...

2.1.2.3. User Operator configuration properties

User Operator deployment can be configured using additional options inside the userOperator object. The following properties are supported:

watchedNamespace
The OpenShift namespace in which the user operator watches for KafkaUsers. Default is the namespace where the Kafka cluster is deployed.
reconciliationIntervalSeconds
The interval between periodic reconciliations in seconds. Default 120.
image
The image property can be used to configure the container image which will be used. For more details about configuring custom container images, see Section 13.1.6, “image.
resources
The resources property configures the amount of resources allocated to the User Operator. For more details about resource request and limit configuration, see Section 13.1.5, “resources.
logging
The logging property configures the logging of the User Operator. For more details, see Section 13.2.45.1, “logging.
secretPrefix
The secretPrefix property adds a prefix to the name of all Secrets created from the KafkaUser resource. For example, STRIMZI_SECRET_PREFIX=kafka- would prefix all Secret names with kafka-. So a KafkaUser named my-user would create a Secret named kafka-my-user.

Example User Operator configuration

apiVersion: kafka.strimzi.io/v1beta2
kind: Kafka
metadata:
  name: my-cluster
spec:
  kafka:
    # ...
  zookeeper:
    # ...
  entityOperator:
    # ...
    userOperator:
      watchedNamespace: my-user-namespace
      reconciliationIntervalSeconds: 60
    # ...

2.1.3. Kafka and ZooKeeper storage types

As stateful applications, Kafka and ZooKeeper need to store data on disk. AMQ Streams supports three storage types for this data:

  • Ephemeral
  • Persistent
  • JBOD storage
Note

JBOD storage is supported only for Kafka, not for ZooKeeper.

When configuring a Kafka resource, you can specify the type of storage used by the Kafka broker and its corresponding ZooKeeper node. You configure the storage type using the storage property in the following resources:

  • Kafka.spec.kafka
  • Kafka.spec.zookeeper

The storage type is configured in the type field.

Refer to the schema reference for more information on storage configuration properties:

Warning

The storage type cannot be changed after a Kafka cluster is deployed.

2.1.3.1. Data storage considerations

An efficient data storage infrastructure is essential to the optimal performance of AMQ Streams.

Block storage is required. File storage, such as NFS, does not work with Kafka.

Choose from one of the following options for your block storage:

Note

AMQ Streams does not require OpenShift raw block volumes.

2.1.3.1.1. File systems

Kafka uses a file system for storing messages. AMQ Streams is compatible with the XFS and ext4 file systems, which are commonly used with Kafka. Consider the underlying architecture and requirements of your deployment when choosing and setting up your file system.

For more information, refer to Filesystem Selection in the Kafka documentation.

2.1.3.1.2. Apache Kafka and ZooKeeper storage

Use separate disks for Apache Kafka and ZooKeeper.

Three types of data storage are supported:

  • Ephemeral (Recommended for development only)
  • Persistent
  • JBOD (Just a Bunch of Disks, suitable for Kafka only)

For more information, see Kafka and ZooKeeper storage.

Solid-state drives (SSDs), though not essential, can improve the performance of Kafka in large clusters where data is sent to and received from multiple topics asynchronously. SSDs are particularly effective with ZooKeeper, which requires fast, low latency data access.

Note

You do not need to provision replicated storage because Kafka and ZooKeeper both have built-in data replication.

2.1.3.2. Ephemeral storage

Ephemeral storage uses emptyDir volumes to store data. To use ephemeral storage, set the type field to ephemeral.

Important

emptyDir volumes are not persistent and the data stored in them is lost when the pod is restarted. After the new pod is started, it must recover all data from the other nodes of the cluster. Ephemeral storage is not suitable for use with single-node ZooKeeper clusters or for Kafka topics with a replication factor of 1. This configuration will cause data loss.

An example of Ephemeral storage

apiVersion: kafka.strimzi.io/v1beta2
kind: Kafka
metadata:
  name: my-cluster
spec:
  kafka:
    # ...
    storage:
      type: ephemeral
    # ...
  zookeeper:
    # ...
    storage:
      type: ephemeral
    # ...

2.1.3.2.1. Log directories

The ephemeral volume is used by the Kafka brokers as log directories mounted into the following path:

/var/lib/kafka/data/kafka-logIDX

Where IDX is the Kafka broker pod index. For example /var/lib/kafka/data/kafka-log0.

2.1.3.3. Persistent storage

Persistent storage uses Persistent Volume Claims to provision persistent volumes for storing data. Persistent Volume Claims can be used to provision volumes of many different types, depending on the Storage Class which will provision the volume. The data types which can be used with persistent volume claims include many types of SAN storage as well as Local persistent volumes.

To use persistent storage, the type has to be set to persistent-claim. Persistent storage supports additional configuration options:

id (optional)
Storage identification number. This option is mandatory for storage volumes defined in a JBOD storage declaration. Default is 0.
size (required)
Defines the size of the persistent volume claim, for example, "1000Gi".
class (optional)
The OpenShift Storage Class to use for dynamic volume provisioning.
selector (optional)
Allows selecting a specific persistent volume to use. It contains key:value pairs representing labels for selecting such a volume.
deleteClaim (optional)
Boolean value which specifies if the Persistent Volume Claim has to be deleted when the cluster is undeployed. Default is false.
Warning

Increasing the size of persistent volumes in an existing AMQ Streams cluster is only supported in OpenShift versions that support persistent volume resizing. The persistent volume to be resized must use a storage class that supports volume expansion. For other versions of OpenShift and storage classes which do not support volume expansion, you must decide the necessary storage size before deploying the cluster. Decreasing the size of existing persistent volumes is not possible.

Example fragment of persistent storage configuration with 1000Gi size

# ...
storage:
  type: persistent-claim
  size: 1000Gi
# ...

The following example demonstrates the use of a storage class.

Example fragment of persistent storage configuration with specific Storage Class

# ...
storage:
  type: persistent-claim
  size: 1Gi
  class: my-storage-class
# ...

Finally, a selector can be used to select a specific labeled persistent volume to provide needed features such as an SSD.

Example fragment of persistent storage configuration with selector

# ...
storage:
  type: persistent-claim
  size: 1Gi
  selector:
    hdd-type: ssd
  deleteClaim: true
# ...

2.1.3.3.1. Storage class overrides

You can specify a different storage class for one or more Kafka brokers or ZooKeeper nodes, instead of using the default storage class. This is useful if, for example, storage classes are restricted to different availability zones or data centers. You can use the overrides field for this purpose.

In this example, the default storage class is named my-storage-class:

Example AMQ Streams cluster using storage class overrides

apiVersion: kafka.strimzi.io/v1beta2
kind: Kafka
metadata:
  labels:
    app: my-cluster
  name: my-cluster
  namespace: myproject
spec:
  # ...
  kafka:
    replicas: 3
    storage:
      deleteClaim: true
      size: 100Gi
      type: persistent-claim
      class: my-storage-class
      overrides:
        - broker: 0
          class: my-storage-class-zone-1a
        - broker: 1
          class: my-storage-class-zone-1b
        - broker: 2
          class: my-storage-class-zone-1c
  # ...
  zookeeper:
    replicas: 3
    storage:
      deleteClaim: true
      size: 100Gi
      type: persistent-claim
      class: my-storage-class
      overrides:
        - broker: 0
          class: my-storage-class-zone-1a
        - broker: 1
          class: my-storage-class-zone-1b
        - broker: 2
          class: my-storage-class-zone-1c
  # ...

As a result of the configured overrides property, the volumes use the following storage classes:

  • The persistent volumes of ZooKeeper node 0 will use my-storage-class-zone-1a.
  • The persistent volumes of ZooKeeper node 1 will use my-storage-class-zone-1b.
  • The persistent volumes of ZooKeeepr node 2 will use my-storage-class-zone-1c.
  • The persistent volumes of Kafka broker 0 will use my-storage-class-zone-1a.
  • The persistent volumes of Kafka broker 1 will use my-storage-class-zone-1b.
  • The persistent volumes of Kafka broker 2 will use my-storage-class-zone-1c.

The overrides property is currently used only to override storage class configurations. Overriding other storage configuration fields is not currently supported. Other fields from the storage configuration are currently not supported.

2.1.3.3.2. Persistent Volume Claim naming

When persistent storage is used, it creates Persistent Volume Claims with the following names:

data-cluster-name-kafka-idx
Persistent Volume Claim for the volume used for storing data for the Kafka broker pod idx.
data-cluster-name-zookeeper-idx
Persistent Volume Claim for the volume used for storing data for the ZooKeeper node pod idx.
2.1.3.3.3. Log directories

The persistent volume is used by the Kafka brokers as log directories mounted into the following path:

/var/lib/kafka/data/kafka-logIDX

Where IDX is the Kafka broker pod index. For example /var/lib/kafka/data/kafka-log0.

2.1.3.4. Resizing persistent volumes

You can provision increased storage capacity by increasing the size of the persistent volumes used by an existing AMQ Streams cluster. Resizing persistent volumes is supported in clusters that use either a single persistent volume or multiple persistent volumes in a JBOD storage configuration.

Note

You can increase but not decrease the size of persistent volumes. Decreasing the size of persistent volumes is not currently supported in OpenShift.

Prerequisites

  • An OpenShift cluster with support for volume resizing.
  • The Cluster Operator is running.
  • A Kafka cluster using persistent volumes created using a storage class that supports volume expansion.

Procedure

  1. In a Kafka resource, increase the size of the persistent volume allocated to the Kafka cluster, the ZooKeeper cluster, or both.

    • To increase the volume size allocated to the Kafka cluster, edit the spec.kafka.storage property.
    • To increase the volume size allocated to the ZooKeeper cluster, edit the spec.zookeeper.storage property.

      For example, to increase the volume size from 1000Gi to 2000Gi:

      apiVersion: kafka.strimzi.io/v1beta2
      kind: Kafka
      metadata:
        name: my-cluster
      spec:
        kafka:
          # ...
          storage:
            type: persistent-claim
            size: 2000Gi
            class: my-storage-class
          # ...
        zookeeper:
          # ...
  2. Create or update the resource:

    oc apply -f <kafka_configuration_file>

    OpenShift increases the capacity of the selected persistent volumes in response to a request from the Cluster Operator. When the resizing is complete, the Cluster Operator restarts all pods that use the resized persistent volumes. This happens automatically.

Additional resources

2.1.3.5. JBOD storage overview

You can configure AMQ Streams to use JBOD, a data storage configuration of multiple disks or volumes. JBOD is one approach to providing increased data storage for Kafka brokers. It can also improve performance.

A JBOD configuration is described by one or more volumes, each of which can be either ephemeral or persistent. The rules and constraints for JBOD volume declarations are the same as those for ephemeral and persistent storage. For example, you cannot decrease the size of a persistent storage volume after it has been provisioned, or you cannot change the value of sizeLimit when type=ephemeral.

2.1.3.5.1. JBOD configuration

To use JBOD with AMQ Streams, the storage type must be set to jbod. The volumes property allows you to describe the disks that make up your JBOD storage array or configuration. The following fragment shows an example JBOD configuration:

# ...
storage:
  type: jbod
  volumes:
  - id: 0
    type: persistent-claim
    size: 100Gi
    deleteClaim: false
  - id: 1
    type: persistent-claim
    size: 100Gi
    deleteClaim: false
# ...

The ids cannot be changed once the JBOD volumes are created.

Users can add or remove volumes from the JBOD configuration.

2.1.3.5.2. JBOD and Persistent Volume Claims

When persistent storage is used to declare JBOD volumes, the naming scheme of the resulting Persistent Volume Claims is as follows:

data-id-cluster-name-kafka-idx
Where id is the ID of the volume used for storing data for Kafka broker pod idx.
2.1.3.5.3. Log directories

The JBOD volumes will be used by the Kafka brokers as log directories mounted into the following path:

/var/lib/kafka/data-id/kafka-log_idx_
Where id is the ID of the volume used for storing data for Kafka broker pod idx. For example /var/lib/kafka/data-0/kafka-log0.

2.1.3.6. Adding volumes to JBOD storage

This procedure describes how to add volumes to a Kafka cluster configured to use JBOD storage. It cannot be applied to Kafka clusters configured to use any other storage type.

Note

When adding a new volume under an id which was already used in the past and removed, you have to make sure that the previously used PersistentVolumeClaims have been deleted.

Prerequisites

  • An OpenShift cluster
  • A running Cluster Operator
  • A Kafka cluster with JBOD storage

Procedure

  1. Edit the spec.kafka.storage.volumes property in the Kafka resource. Add the new volumes to the volumes array. For example, add the new volume with id 2:

    apiVersion: kafka.strimzi.io/v1beta2
    kind: Kafka
    metadata:
      name: my-cluster
    spec:
      kafka:
        # ...
        storage:
          type: jbod
          volumes:
          - id: 0
            type: persistent-claim
            size: 100Gi
            deleteClaim: false
          - id: 1
            type: persistent-claim
            size: 100Gi
            deleteClaim: false
          - id: 2
            type: persistent-claim
            size: 100Gi
            deleteClaim: false
        # ...
      zookeeper:
        # ...
  2. Create or update the resource:

    oc apply -f <kafka_configuration_file>
  3. Create new topics or reassign existing partitions to the new disks.

Additional resources

For more information about reassigning topics, see Section 2.1.4.2, “Partition reassignment tool”.

2.1.3.7. Removing volumes from JBOD storage

This procedure describes how to remove volumes from Kafka cluster configured to use JBOD storage. It cannot be applied to Kafka clusters configured to use any other storage type. The JBOD storage always has to contain at least one volume.

Important

To avoid data loss, you have to move all partitions before removing the volumes.

Prerequisites

  • An OpenShift cluster
  • A running Cluster Operator
  • A Kafka cluster with JBOD storage with two or more volumes

Procedure

  1. Reassign all partitions from the disks which are you going to remove. Any data in partitions still assigned to the disks which are going to be removed might be lost.
  2. Edit the spec.kafka.storage.volumes property in the Kafka resource. Remove one or more volumes from the volumes array. For example, remove the volumes with ids 1 and 2:

    apiVersion: kafka.strimzi.io/v1beta2
    kind: Kafka
    metadata:
      name: my-cluster
    spec:
      kafka:
        # ...
        storage:
          type: jbod
          volumes:
          - id: 0
            type: persistent-claim
            size: 100Gi
            deleteClaim: false
        # ...
      zookeeper:
        # ...
  3. Create or update the resource:

    oc apply -f <kafka_configuration_file>

Additional resources

For more information about reassigning topics, see Section 2.1.4.2, “Partition reassignment tool”.

2.1.4. Scaling clusters

Scale Kafka clusters by adding or removing brokers. If a cluster already has topics defined, you also have to reassign partitions.

You use the kafka-reassign-partitions.sh tool to reassign partitions. The tool uses a reassignment JSON file that specifies the topics to reassign.

You can generate a reassignment JSON file or create a file manually if you want to move specific partitions.

2.1.4.1. Broker scaling configuration

You configure the Kafka.spec.kafka.replicas configuration to add or reduce the number of brokers.

Broker addition

The primary way of increasing throughput for a topic is to increase the number of partitions for that topic. That works because the extra partitions allow the load of the topic to be shared between the different brokers in the cluster. However, in situations where every broker is constrained by a particular resource (typically I/O) using more partitions will not result in increased throughput. Instead, you need to add brokers to the cluster.

When you add an extra broker to the cluster, Kafka does not assign any partitions to it automatically. You must decide which partitions to reassign from the existing brokers to the new broker.

Once the partitions have been redistributed between all the brokers, the resource utilization of each broker is reduced.

Broker removal

If you are using StatefulSets to manage broker pods, you cannot remove any pod from the cluster. You can only remove one or more of the highest numbered pods from the cluster. For example, in a cluster of 12 brokers the pods are named cluster-name-kafka-0 up to cluster-name-kafka-11. If you decide to scale down by one broker, the cluster-name-kafka-11 will be removed.

Before you remove a broker from a cluster, ensure that it is not assigned to any partitions. You should also decide which of the remaining brokers will be responsible for each of the partitions on the broker being decommissioned. Once the broker has no assigned partitions, you can scale the cluster down safely.

2.1.4.2. Partition reassignment tool

The Topic Operator does not currently support reassigning replicas to different brokers, so it is necessary to connect directly to broker pods to reassign replicas to brokers.

Within a broker pod, the kafka-reassign-partitions.sh tool allows you to reassign partitions to different brokers.

It has three different modes:

--generate
Takes a set of topics and brokers and generates a reassignment JSON file which will result in the partitions of those topics being assigned to those brokers. Because this operates on whole topics, it cannot be used when you only want to reassign some partitions of some topics.
--execute
Takes a reassignment JSON file and applies it to the partitions and brokers in the cluster. Brokers that gain partitions as a result become followers of the partition leader. For a given partition, once the new broker has caught up and joined the ISR (in-sync replicas) the old broker will stop being a follower and will delete its replica.
--verify
Using the same reassignment JSON file as the --execute step, --verify checks whether all the partitions in the file have been moved to their intended brokers. If the reassignment is complete, --verify also removes any traffic throttles (--throttle) that are in effect. Unless removed, throttles will continue to affect the cluster even after the reassignment has finished.

It is only possible to have one reassignment running in a cluster at any given time, and it is not possible to cancel a running reassignment. If you need to cancel a reassignment, wait for it to complete and then perform another reassignment to revert the effects of the first reassignment. The kafka-reassign-partitions.sh will print the reassignment JSON for this reversion as part of its output. Very large reassignments should be broken down into a number of smaller reassignments in case there is a need to stop in-progress reassignment.

2.1.4.2.1. Partition reassignment JSON file

The reassignment JSON file has a specific structure:

{
  "version": 1,
  "partitions": [
    <PartitionObjects>
  ]
}

Where <PartitionObjects> is a comma-separated list of objects like:

{
  "topic": <TopicName>,
  "partition": <Partition>,
  "replicas": [ <AssignedBrokerIds> ]
}
Note

Although Kafka also supports a "log_dirs" property this should not be used in AMQ Streams.

The following is an example reassignment JSON file that assigns partition 4 of topic topic-a to brokers 2, 4 and 7, and partition 2 of topic topic-b to brokers 1, 5 and 7:

Example partition reassignment file

{
  "version": 1,
  "partitions": [
    {
      "topic": "topic-a",
      "partition": 4,
      "replicas": [2,4,7]
    },
    {
      "topic": "topic-b",
      "partition": 2,
      "replicas": [1,5,7]
    }
  ]
}

Partitions not included in the JSON are not changed.

2.1.4.2.2. Partition reassignment between JBOD volumes

When using JBOD storage in your Kafka cluster, you can choose to reassign the partitions between specific volumes and their log directories (each volume has a single log directory). To reassign a partition to a specific volume, add the log_dirs option to <PartitionObjects> in the reassignment JSON file.

{
  "topic": <TopicName>,
  "partition": <Partition>,
  "replicas": [ <AssignedBrokerIds> ],
  "log_dirs": [ <AssignedLogDirs> ]
}

The log_dirs object should contain the same number of log directories as the number of replicas specified in the replicas object. The value should be either an absolute path to the log directory, or the any keyword.

Example partition reassignment file specifying log directories

{
      "topic": "topic-a",
      "partition": 4,
      "replicas": [2,4,7].
      "log_dirs": [ "/var/lib/kafka/data-0/kafka-log2", "/var/lib/kafka/data-0/kafka-log4", "/var/lib/kafka/data-0/kafka-log7" ]
}

Partition reassignment throttles

Partition reassignment can be a slow process because it involves transferring large amounts of data between brokers. To avoid a detrimental impact on clients, you can throttle the reassignment process. Use the --throttle parameter with the kafka-reassign-partitions.sh tool to throttle a reassignment. You specify a maximum threshold in bytes per second for the movement of partitions between brokers. For example, --throttle 5000000 sets a maximum threshold for moving partitions of 50 MBps.

Throttling might cause the reassignment to take longer to complete.

  • If the throttle is too low, the newly assigned brokers will not be able to keep up with records being published and the reassignment will never complete.
  • If the throttle is too high, clients will be impacted.

For example, for producers, this could manifest as higher than normal latency waiting for acknowledgment. For consumers, this could manifest as a drop in throughput caused by higher latency between polls.

2.1.4.3. Generating reassignment JSON files

This procedure describes how to generate a reassignment JSON file. Use the reassignment file with the kafka-reassign-partitions.sh tool to reassign partitions after scaling a Kafka cluster.

The steps describe a secure reassignment process that uses TLS. You’ll need a Kafka cluster that uses TLS encryption and authentication.

Prerequisites

  • You have a running Cluster Operator.
  • You have a running Kafka cluster based on a Kafka resource configured with internal TLS authentication and encryption.

    Kafka configuration with TLS

    apiVersion: kafka.strimzi.io/v1beta2
    kind: Kafka
    metadata:
      name: my-cluster
    spec:
      kafka:
        # ...
        listeners:
          # ...
          - name: tls
            port: 9093
            type: internal
            tls: true 1
            authentication:
              type: tls 2
        # ...

    1
    Enables TLS encryption for the internal listener.
    2
    Listener authentication mechanism specified as mutual TLS.
  • The running Kafka cluster contains a set of topics and partitions to reassign.

    Example topic configuration for my-topic

    apiVersion: kafka.strimzi.io/v1beta2
    kind: KafkaTopic
    metadata:
      name: my-topic
      labels:
        strimzi.io/cluster: my-cluster
    spec:
      partitions: 10
      replicas: 3
      config:
        retention.ms: 7200000
        segment.bytes: 1073741824
        # ...

  • You have a KafkaUser configured with ACL rules that specify permission to produce and consume topics from the Kafka brokers.

    Example Kafka user configuration with ACL rules to allow operations on my-topic and my-cluster

    apiVersion: kafka.strimzi.io/v1beta2
    kind: KafkaUser
    metadata:
      name: my-user
      labels:
        strimzi.io/cluster: my-cluster
    spec:
      authentication: 1
        type: tls
      authorization:
        type: simple 2
        acls:
          - resource:
              type: topic
              name: my-topic
              patternType: literal
            operation: Write
            host: "*"
          - resource:
              type: topic
              name: my-topic
              patternType: literal
            operation: Create
            host: "*"
          - resource:
              type: topic
              name: my-topic
              patternType: literal
            operation: Describe
            host: "*"
          - resource:
              type: cluster
              name: my-cluster
              patternType: literal
            operation: Alter
            host: "*"
          # ...
      # ...

    1
    User authentication mechanism defined as mutual tls.
    2
    Simple authorization and accompanying list of ACL rules.
    Note

    Permission for a Describe operation is required as a minimum for TLS access to a topic.

Procedure

  1. Extract the cluster CA certificate and password from the <cluster_name>-cluster-ca-cert Secret of the Kafka cluster.

    oc get secret <cluster_name>-cluster-ca-cert -o jsonpath='{.data.ca\.p12}' | base64 -d > ca.p12
    oc get secret <cluster_name>-cluster-ca-cert -o jsonpath='{.data.ca\.password}' | base64 -d > ca.password

    Replace <cluster_name> with the name of the Kafka cluster. When you deploy Kafka using the Kafka resource, a Secret with the cluster CA certificate is created with the Kafka cluster name (<cluster_name>-cluster-ca-cert). For example, my-cluster-cluster-ca-cert.

  2. Run a new interactive pod container using the AMQ Streams Kafka image to connect to a running Kafka broker.

    oc run --restart=Never --image=registry.redhat.io/amq7/amq-streams-kafka-31-rhel8:2.1.0 <interactive_pod_name> -- /bin/sh -c "sleep 3600"

    Replace <interactive_pod_name> with the name of the pod.

  3. Copy the cluster CA certificate to the interactive pod container.

    oc cp ca.p12 <interactive_pod_name>:/tmp
  4. Extract the user CA certificate and password from the Secret of the Kafka user that has permission to access the Kafka brokers.

    oc get secret <kafka_user> -o jsonpath='{.data.user\.p12}' | base64 -d > user.p12
    oc get secret <kafka_user> -o jsonpath='{.data.user\.password}' | base64 -d > user.password

    Replace <kafka_user> with the name of the Kafka user. When you create a Kafka user using the KafkaUser resource, a Secret with the user CA certificate is created with the Kafka user name. For example, my-user.

  5. Copy the user CA certificate to the interactive pod container.

    oc cp user.p12 <interactive_pod_name>:/tmp

    The CA certificates allow the interactive pod container to connect to the Kafka broker using TLS.

  6. Create a config.properties file to specify the truststore and keystore used to authenticate connection to the Kafka cluster.

    Use the certificates and passwords you extracted in the previous steps.

    bootstrap.servers=<kafka_cluster_name>-kafka-bootstrap:9093 1
    security.protocol=SSL 2
    ssl.truststore.location=/tmp/ca.p12 3
    ssl.truststore.password=<truststore_password> 4
    ssl.keystore.location=/tmp/user.p12 5
    ssl.keystore.password=<keystore_password> 6
    1
    The bootstrap server address to connect to the Kafka cluster. Use your own Kafka cluster name to replace <kafka_cluster_name>.
    2
    The security protocol option when using TLS for encryption.
    3
    The truststore location contains the public key certificate (ca.p12) for the Kafka cluster.
    4
    The password (ca.password) for accessing the truststore.
    5
    The keystore location contains the public key certificate (user.p12) for the Kafka user.
    6
    The password (user.password) for accessing the keystore.
  7. Copy the config.properties file to the interactive pod container.

    oc cp config.properties <interactive_pod_name>:/tmp/config.properties
  8. Prepare a JSON file named topics.json that specifies the topics to move.

    Specify topic names as a comma-separated list.

    Example JSON file to reassign all the partitions of topic-a and topic-b

    {
      "version": 1,
      "topics": [
        { "topic": "topic-a"},
        { "topic": "topic-b"}
      ]
    }

  9. Copy the topics.json file to the interactive pod container.

    oc cp topics.json <interactive_pod_name>:/tmp/topics.json
  10. Start a shell process in the interactive pod container.

    oc exec -n <namespace> -ti <interactive_pod_name> /bin/bash

    Replace <namespace> with the OpenShift namespace where the pod is running.

  11. Use the kafka-reassign-partitions.sh command to generate the reassignment JSON.

    Example command to move all the partitions of topic-a and topic-b to brokers 0, 1 and 2

    bin/kafka-reassign-partitions.sh --bootstrap-server my-cluster-kafka-bootstrap:9093 \
      --command-config /tmp/config.properties \
      --topics-to-move-json-file /tmp/topics.json \
      --broker-list 0,1,2 \
      --generate

2.1.4.4. Scaling up a Kafka cluster

Use a reassignment file to increase the number of brokers in a Kafka cluster.

The reassignment file should describe how partitions are reassigned to brokers in the enlarged Kafka cluster.

This procedure describes a secure scaling process that uses TLS. You’ll need a Kafka cluster that uses TLS encryption and authentication.

Prerequisites

  • You have a running Kafka cluster based on a Kafka resource configured with internal TLS authentication and encryption.
  • You have generated a reassignment JSON file named reassignment.json.
  • You are running an interactive pod container that is connected to the running Kafka broker.
  • You are connected as a KafkaUser configured with ACL rules that specify permission to manage the Kafka cluster and its topics.

See Generating reassignment JSON files.

Procedure

  1. Add as many new brokers as you need by increasing the Kafka.spec.kafka.replicas configuration option.
  2. Verify that the new broker pods have started.
  3. If you haven’t done so, run an interactive pod container to generate a reassignment JSON file named reassignment.json.
  4. Copy the reassignment.json file to the interactive pod container.

    oc cp reassignment.json <interactive_pod_name>:/tmp/reassignment.json

    Replace <interactive_pod_name> with the name of the pod.

  5. Start a shell process in the interactive pod container.

    oc exec -n <namespace> -ti <interactive_pod_name> /bin/bash

    Replace <namespace> with the OpenShift namespace where the pod is running.

  6. Run the partition reassignment using the kafka-reassign-partitions.sh script from the interactive pod container.

    bin/kafka-reassign-partitions.sh --bootstrap-server
     <cluster_name>-kafka-bootstrap:9093 \
     --command-config /tmp/config.properties \
     --reassignment-json-file /tmp/reassignment.json \
     --execute

    Replace <cluster_name> with the name of your Kafka cluster. For example, my-cluster-kafka-bootstrap:9093

    If you are going to throttle replication, you can also pass the --throttle option with an inter-broker throttled rate in bytes per second. For example:

    bin/kafka-reassign-partitions.sh --bootstrap-server
      <cluster_name>-kafka-bootstrap:9093 \
      --command-config /tmp/config.properties \
      --reassignment-json-file /tmp/reassignment.json \
      --throttle 5000000 \
      --execute

    This command will print out two reassignment JSON objects. The first records the current assignment for the partitions being moved. You should save this to a local file (not a file in the pod) in case you need to revert the reassignment later on. The second JSON object is the target reassignment you have passed in your reassignment JSON file.

    If you need to change the throttle during reassignment, you can use the same command with a different throttled rate. For example:

    bin/kafka-reassign-partitions.sh --bootstrap-server
      <cluster_name>-kafka-bootstrap:9093 \
      --command-config /tmp/config.properties \
      --reassignment-json-file /tmp/reassignment.json \
      --throttle 10000000 \
      --execute
  7. Verify that the reassignment has completed using the kafka-reassign-partitions.sh command line tool from any of the broker pods. This is the same command as the previous step, but with the --verify option instead of the --execute option.

    bin/kafka-reassign-partitions.sh --bootstrap-server
      <cluster_name>-kafka-bootstrap:9093 \
      --command-config /tmp/config.properties \
      --reassignment-json-file /tmp/reassignment.json \
      --verify

    The reassignment has finished when the --verify command reports that each of the partitions being moved has completed successfully. This final --verify will also have the effect of removing any reassignment throttles.

  8. You can now delete the revert file if you saved the JSON for reverting the assignment to their original brokers.

2.1.4.5. Scaling down a Kafka cluster

Use a reassignment file to decrease the number of brokers in a Kafka cluster.

The reassignment file must describe how partitions are reassigned to the remaining brokers in the Kafka cluster. Brokers in the highest numbered pods are removed first.

This procedure describes a secure scaling process that uses TLS. You’ll need a Kafka cluster that uses TLS encryption and authentication.

Prerequisites

  • You have a running Kafka cluster based on a Kafka resource configured with internal TLS authentication and encryption.
  • You have generated a reassignment JSON file named reassignment.json.
  • You are running an interactive pod container that is connected to the running Kafka broker.
  • You are connected as a KafkaUser configured with ACL rules that specify permission to manage the Kafka cluster and its topics.

See Generating reassignment JSON files.

Procedure

  1. If you haven’t done so, run an interactive pod container to generate a reassignment JSON file named reassignment.json.
  2. Copy the reassignment.json file to the interactive pod container.

    oc cp reassignment.json <interactive_pod_name>:/tmp/reassignment.json

    Replace <interactive_pod_name> with the name of the pod.

  3. Start a shell process in the interactive pod container.

    oc exec -n <namespace> -ti <interactive_pod_name> /bin/bash

    Replace <namespace> with the OpenShift namespace where the pod is running.

  4. Run the partition reassignment using the kafka-reassign-partitions.sh script from the interactive pod container.

    bin/kafka-reassign-partitions.sh --bootstrap-server
     <cluster_name>-kafka-bootstrap:9093 \
     --command-config /tmp/config.properties \
     --reassignment-json-file /tmp/reassignment.json \
     --execute

    Replace <cluster_name> with the name of your Kafka cluster. For example, my-cluster-kafka-bootstrap:9093

    If you are going to throttle replication, you can also pass the --throttle option with an inter-broker throttled rate in bytes per second. For example:

    bin/kafka-reassign-partitions.sh --bootstrap-server
      <cluster_name>-kafka-bootstrap:9093 \
      --command-config /tmp/config.properties \
      --reassignment-json-file /tmp/reassignment.json \
      --throttle 5000000 \
      --execute

    This command will print out two reassignment JSON objects. The first records the current assignment for the partitions being moved. You should save this to a local file (not a file in the pod) in case you need to revert the reassignment later on. The second JSON object is the target reassignment you have passed in your reassignment JSON file.

    If you need to change the throttle during reassignment, you can use the same command with a different throttled rate. For example:

    bin/kafka-reassign-partitions.sh --bootstrap-server
      <cluster_name>-kafka-bootstrap:9093 \
      --command-config /tmp/config.properties \
      --reassignment-json-file /tmp/reassignment.json \
      --throttle 10000000 \
      --execute
  5. Verify that the reassignment has completed using the kafka-reassign-partitions.sh command line tool from any of the broker pods. This is the same command as the previous step, but with the --verify option instead of the --execute option.

    bin/kafka-reassign-partitions.sh --bootstrap-server
      <cluster_name>-kafka-bootstrap:9093 \
      --command-config /tmp/config.properties \
      --reassignment-json-file /tmp/reassignment.json \
      --verify

    The reassignment has finished when the --verify command reports that each of the partitions being moved has completed successfully. This final --verify will also have the effect of removing any reassignment throttles.

  6. You can now delete the revert file if you saved the JSON for reverting the assignment to their original brokers.
  7. When all the partition reassignments have finished, the brokers being removed should not have responsibility for any of the partitions in the cluster. You can verify this by checking that the broker’s data log directory does not contain any live partition logs. If the log directory on the broker contains a directory that does not match the extended regular expression \.[a-z0-9]-delete$, the broker still has live partitions and should not be stopped.

    You can check this by executing the command:

    oc exec my-cluster-kafka-0 -c kafka -it -- \
      /bin/bash -c \
      "ls -l /var/lib/kafka/kafka-log_<n>_ | grep -E '^d' | grep -vE '[a-zA-Z0-9.-]+\.[a-z0-9]+-delete$'"

    where n is the number of the pods being deleted.

    If the above command prints any output then the broker still has live partitions. In this case, either the reassignment has not finished or the reassignment JSON file was incorrect.

  8. When you have confirmed that the broker has no live partitions, you can edit the Kafka.spec.kafka.replicas property of your Kafka resource to reduce the number of brokers.

2.1.5. Maintenance time windows for rolling updates

Maintenance time windows allow you to schedule certain rolling updates of your Kafka and ZooKeeper clusters to start at a convenient time.

2.1.5.1. Maintenance time windows overview

In most cases, the Cluster Operator only updates your Kafka or ZooKeeper clusters in response to changes to the corresponding Kafka resource. This enables you to plan when to apply changes to a Kafka resource to minimize the impact on Kafka client applications.

However, some updates to your Kafka and ZooKeeper clusters can happen without any corresponding change to the Kafka resource. For example, the Cluster Operator will need to perform a rolling restart if a CA (Certificate Authority) certificate that it manages is close to expiry.

While a rolling restart of the pods should not affect availability of the service (assuming correct broker and topic configurations), it could affect performance of the Kafka client applications. Maintenance time windows allow you to schedule such spontaneous rolling updates of your Kafka and ZooKeeper clusters to start at a convenient time. If maintenance time windows are not configured for a cluster then it is possible that such spontaneous rolling updates will happen at an inconvenient time, such as during a predictable period of high load.

2.1.5.2. Maintenance time window definition

You configure maintenance time windows by entering an array of strings in the Kafka.spec.maintenanceTimeWindows property. Each string is a cron expression interpreted as being in UTC (Coordinated Universal Time, which for practical purposes is the same as Greenwich Mean Time).

The following example configures a single maintenance time window that starts at midnight and ends at 01:59am (UTC), on Sundays, Mondays, Tuesdays, Wednesdays, and Thursdays:

# ...
maintenanceTimeWindows:
  - "* * 0-1 ? * SUN,MON,TUE,WED,THU *"
# ...

In practice, maintenance windows should be set in conjunction with the Kafka.spec.clusterCa.renewalDays and Kafka.spec.clientsCa.renewalDays properties of the Kafka resource, to ensure that the necessary CA certificate renewal can be completed in the configured maintenance time windows.

Note

AMQ Streams does not schedule maintenance operations exactly according to the given windows. Instead, for each reconciliation, it checks whether a maintenance window is currently "open". This means that the start of maintenance operations within a given time window can be delayed by up to the Cluster Operator reconciliation interval. Maintenance time windows must therefore be at least this long.

Additional resources

2.1.5.3. Configuring a maintenance time window

You can configure a maintenance time window for rolling updates triggered by supported processes.

Prerequisites

  • An OpenShift cluster.
  • The Cluster Operator is running.

Procedure

  1. Add or edit the maintenanceTimeWindows property in the Kafka resource. For example to allow maintenance between 0800 and 1059 and between 1400 and 1559 you would set the maintenanceTimeWindows as shown below:

    apiVersion: kafka.strimzi.io/v1beta2
    kind: Kafka
    metadata:
      name: my-cluster
    spec:
      kafka:
        # ...
      zookeeper:
        # ...
      maintenanceTimeWindows:
        - "* * 8-10 * * ?"
        - "* * 14-15 * * ?"
  2. Create or update the resource:

    oc apply -f <kafka_configuration_file>

Additional resources

Performing rolling updates:

2.1.6. Connecting to ZooKeeper from a terminal

Most Kafka CLI tools can connect directly to Kafka, so under normal circumstances you should not need to connect to ZooKeeper. ZooKeeper services are secured with encryption and authentication and are not intended to be used by external applications that are not part of AMQ Streams.

However, if you want to use Kafka CLI tools that require a connection to ZooKeeper, you can use a terminal inside a ZooKeeper container and connect to localhost:12181 as the ZooKeeper address.

Prerequisites

  • An OpenShift cluster is available.
  • A Kafka cluster is running.
  • The Cluster Operator is running.

Procedure

  1. Open the terminal using the OpenShift console or run the exec command from your CLI.

    For example:

    oc exec -ti my-cluster-zookeeper-0 -- bin/kafka-topics.sh --list --zookeeper localhost:12181

    Be sure to use localhost:12181.

    You can now run Kafka commands to ZooKeeper.

2.1.7. Deleting Kafka nodes manually

This procedure describes how to delete an existing Kafka node by using an OpenShift annotation. Deleting a Kafka node consists of deleting both the Pod on which the Kafka broker is running and the related PersistentVolumeClaim (if the cluster was deployed with persistent storage). After deletion, the Pod and its related PersistentVolumeClaim are recreated automatically.

Warning

Deleting a PersistentVolumeClaim can cause permanent data loss. The following procedure should only be performed if you have encountered storage issues.

Prerequisites

See the Deploying and Upgrading AMQ Streams on OpenShift guide for instructions on running a:

Procedure

  1. Find the name of the Pod that you want to delete.

    Kafka broker pods are named <cluster-name>-kafka-<index>, where <index> starts at zero and ends at the total number of replicas minus one. For example, my-cluster-kafka-0.

  2. Annotate the Pod resource in OpenShift.

    Use oc annotate:

    oc annotate pod cluster-name-kafka-index strimzi.io/delete-pod-and-pvc=true
  3. Wait for the next reconciliation, when the annotated pod with the underlying persistent volume claim will be deleted and then recreated.

2.1.8. Deleting ZooKeeper nodes manually

This procedure describes how to delete an existing ZooKeeper node by using an OpenShift annotation. Deleting a ZooKeeper node consists of deleting both the Pod on which ZooKeeper is running and the related PersistentVolumeClaim (if the cluster was deployed with persistent storage). After deletion, the Pod and its related PersistentVolumeClaim are recreated automatically.

Warning

Deleting a PersistentVolumeClaim can cause permanent data loss. The following procedure should only be performed if you have encountered storage issues.

Prerequisites

See the Deploying and Upgrading AMQ Streams on OpenShift guide for instructions on running a:

Procedure

  1. Find the name of the Pod that you want to delete.

    ZooKeeper pods are named <cluster-name>-zookeeper-<index>, where <index> starts at zero and ends at the total number of replicas minus one. For example, my-cluster-zookeeper-0.

  2. Annotate the Pod resource in OpenShift.

    Use oc annotate:

    oc annotate pod cluster-name-zookeeper-index strimzi.io/delete-pod-and-pvc=true
  3. Wait for the next reconciliation, when the annotated pod with the underlying persistent volume claim will be deleted and then recreated.

2.1.9. List of Kafka cluster resources

The following resources are created by the Cluster Operator in the OpenShift cluster:

Shared resources

cluster-name-cluster-ca
Secret with the Cluster CA private key used to encrypt the cluster communication.
cluster-name-cluster-ca-cert
Secret with the Cluster CA public key. This key can be used to verify the identity of the Kafka brokers.
cluster-name-clients-ca
Secret with the Clients CA private key used to sign user certificates
cluster-name-clients-ca-cert
Secret with the Clients CA public key. This key can be used to verify the identity of the Kafka users.
cluster-name-cluster-operator-certs
Secret with Cluster operators keys for communication with Kafka and ZooKeeper.

ZooKeeper nodes

cluster-name-zookeeper

Name given to the following ZooKeeper resources:

  • StatefulSet or StrimziPodSet (if the UseStrimziPodSets feature gate is enabled) for managing the ZooKeeper node pods.
  • Service account used by the ZooKeeper nodes.
  • PodDisruptionBudget configured for the ZooKeeper nodes.
cluster-name-zookeeper-idx
Pods created by the ZooKeeper StatefulSet or StrimziPodSet.
cluster-name-zookeeper-nodes
Headless Service needed to have DNS resolve the ZooKeeper pods IP addresses directly.
cluster-name-zookeeper-client
Service used by Kafka brokers to connect to ZooKeeper nodes as clients.
cluster-name-zookeeper-config
ConfigMap that contains the ZooKeeper ancillary configuration, and is mounted as a volume by the ZooKeeper node pods.
cluster-name-zookeeper-nodes
Secret with ZooKeeper node keys.
cluster-name-network-policy-zookeeper
Network policy managing access to the ZooKeeper services.
data-cluster-name-zookeeper-idx
Persistent Volume Claim for the volume used for storing data for the ZooKeeper node pod idx. This resource will be created only if persistent storage is selected for provisioning persistent volumes to store data.

Kafka brokers

cluster-name-kafka

Name given to the following Kafka resources:

  • StatefulSet or StrimziPodSet (if the UseStrimziPodSets feature gate is enabled) for managing the Kafka broker pods.
  • Service account used by the Kafka pods.
  • PodDisruptionBudget configured for the Kafka brokers.
cluster-name-kafka-idx
Pods created by the Kafka StatefulSet or StrimziPodSet.
cluster-name-kafka-brokers
Service needed to have DNS resolve the Kafka broker pods IP addresses directly.
cluster-name-kafka-bootstrap
Service can be used as bootstrap servers for Kafka clients connecting from within the OpenShift cluster.
cluster-name-kafka-external-bootstrap
Bootstrap service for clients connecting from outside the OpenShift cluster. This resource is created only when an external listener is enabled. The old service name will be used for backwards compatibility when the listener name is external and port is 9094.
cluster-name-kafka-pod-id
Service used to route traffic from outside the OpenShift cluster to individual pods. This resource is created only when an external listener is enabled. The old service name will be used for backwards compatibility when the listener name is external and port is 9094.
cluster-name-kafka-external-bootstrap
Bootstrap route for clients connecting from outside the OpenShift cluster. This resource is created only when an external listener is enabled and set to type route. The old route name will be used for backwards compatibility when the listener name is external and port is 9094.
cluster-name-kafka-pod-id
Route for traffic from outside the OpenShift cluster to individual pods. This resource is created only when an external listener is enabled and set to type route. The old route name will be used for backwards compatibility when the listener name is external and port is 9094.
cluster-name-kafka-listener-name-bootstrap
Bootstrap service for clients connecting from outside the OpenShift cluster. This resource is created only when an external listener is enabled. The new service name will be used for all other external listeners.
cluster-name-kafka-listener-name-pod-id
Service used to route traffic from outside the OpenShift cluster to individual pods. This resource is created only when an external listener is enabled. The new service name will be used for all other external listeners.
cluster-name-kafka-listener-name-bootstrap
Bootstrap route for clients connecting from outside the OpenShift cluster. This resource is created only when an external listener is enabled and set to type route. The new route name will be used for all other external listeners.
cluster-name-kafka-listener-name-pod-id
Route for traffic from outside the OpenShift cluster to individual pods. This resource is created only when an external listener is enabled and set to type route. The new route name will be used for all other external listeners.
cluster-name-kafka-config
ConfigMap which contains the Kafka ancillary configuration and is mounted as a volume by the Kafka broker pods.
cluster-name-kafka-brokers
Secret with Kafka broker keys.
cluster-name-network-policy-kafka
Network policy managing access to the Kafka services.
strimzi-namespace-name-cluster-name-kafka-init
Cluster role binding used by the Kafka brokers.
cluster-name-jmx
Secret with JMX username and password used to secure the Kafka broker port. This resource is created only when JMX is enabled in Kafka.
data-cluster-name-kafka-idx
Persistent Volume Claim for the volume used for storing data for the Kafka broker pod idx. This resource is created only if persistent storage is selected for provisioning persistent volumes to store data.
data-id-cluster-name-kafka-idx
Persistent Volume Claim for the volume id used for storing data for the Kafka broker pod idx. This resource is created only if persistent storage is selected for JBOD volumes when provisioning persistent volumes to store data.

Entity Operator

These resources are only created if the Entity Operator is deployed using the Cluster Operator.

cluster-name-entity-operator

Name given to the following Entity Operator resources:

  • Deployment with Topic and User Operators.
  • Service account used by the Entity Operator.
cluster-name-entity-operator-random-string
Pod created by the Entity Operator deployment.
cluster-name-entity-topic-operator-config
ConfigMap with ancillary configuration for Topic Operators.
cluster-name-entity-user-operator-config
ConfigMap with ancillary configuration for User Operators.
cluster-name-entity-topic-operator-certs
Secret with Topic Operator keys for communication with Kafka and ZooKeeper.
cluster-name-entity-user-operator-certs
Secret with User Operator keys for communication with Kafka and ZooKeeper.
strimzi-cluster-name-entity-topic-operator
Role binding used by the Entity Topic Operator.
strimzi-cluster-name-entity-user-operator
Role binding used by the Entity User Operator.

Kafka Exporter

These resources are only created if the Kafka Exporter is deployed using the Cluster Operator.

cluster-name-kafka-exporter

Name given to the following Kafka Exporter resources:

  • Deployment with Kafka Exporter.
  • Service used to collect consumer lag metrics.
  • Service account used by the Kafka Exporter.
cluster-name-kafka-exporter-random-string
Pod created by the Kafka Exporter deployment.

Cruise Control

These resources are only created if Cruise Control was deployed using the Cluster Operator.

cluster-name-cruise-control

Name given to the following Cruise Control resources:

  • Deployment with Cruise Control.
  • Service used to communicate with Cruise Control.
  • Service account used by the Cruise Control.
cluster-name-cruise-control-random-string
Pod created by the Cruise Control deployment.
cluster-name-cruise-control-config
ConfigMap that contains the Cruise Control ancillary configuration, and is mounted as a volume by the Cruise Control pods.
cluster-name-cruise-control-certs
Secret with Cruise Control keys for communication with Kafka and ZooKeeper.
cluster-name-network-policy-cruise-control
Network policy managing access to the Cruise Control service.

2.2. Kafka Connect cluster configuration

This section describes how to configure a Kafka Connect deployment in your AMQ Streams cluster.

Kafka Connect is an integration toolkit for streaming data between Kafka brokers and other systems using connector plugins. Kafka Connect provides a framework for integrating Kafka with an external data source or target, such as a database, for import or export of data using connectors. Connectors are plugins that provide the connection configuration needed. The full schema of the KafkaConnect resource is described in Section 13.2.59, “KafkaConnect schema reference”.

For more information on deploying connector plugins, see Extending Kafka Connect with connector plug-ins.

2.2.1. Configuring Kafka Connect

Use Kafka Connect to set up external data connections to your Kafka cluster. Use the properties of the KafkaConnect resource to configure your Kafka Connect deployment.

KafkaConnector configuration

KafkaConnector resources allow you to create and manage connector instances for Kafka Connect in an OpenShift-native way.

In your Kafka Connect configuration, you enable KafkaConnectors for a Kafka Connect cluster by adding the strimzi.io/use-connector-resources annotation. You can also add a build configuration so that AMQ Streams automatically builds a container image with the connector plugins you require for your data connections. External configuration for Kafka Connect connectors is specified through the externalConfiguration property.

To manage connectors, you can use the Kafka Connect REST API, or use KafkaConnector custom resources. KafkaConnector resources must be deployed to the same namespace as the Kafka Connect cluster they link to. For more information on using these methods to create, reconfigure, or delete connectors, see Creating and managing connectors.

Connector configuration is passed to Kafka Connect as part of an HTTP request and stored within Kafka itself. ConfigMaps and Secrets are standard OpenShift resources used for storing configurations and confidential data. You can use ConfigMaps and Secrets to configure certain elements of a connector. You can then reference the configuration values in HTTP REST commands, which keeps the configuration separate and more secure, if needed. This method applies especially to confidential data, such as usernames, passwords, or certificates.

Prerequisites

  • An OpenShift cluster
  • A running Cluster Operator

See the Deploying and Upgrading AMQ Streams on OpenShift guide for instructions on running a:

Procedure

  1. Edit the spec properties of the KafkaConnect resource.

    The properties you can configure are shown in this example configuration:

    apiVersion: kafka.strimzi.io/v1beta2
    kind: KafkaConnect 1
    metadata:
      name: my-connect-cluster
      annotations:
        strimzi.io/use-connector-resources: "true" 2
    spec:
      replicas: 3 3
      authentication: 4
        type: tls
        certificateAndKey:
          certificate: source.crt
          key: source.key
          secretName: my-user-source
      bootstrapServers: my-cluster-kafka-bootstrap:9092 5
      tls: 6
        trustedCertificates:
          - secretName: my-cluster-cluster-cert
            certificate: ca.crt
          - secretName: my-cluster-cluster-cert
            certificate: ca2.crt
      config: 7
        group.id: my-connect-cluster
        offset.storage.topic: my-connect-cluster-offsets
        config.storage.topic: my-connect-cluster-configs
        status.storage.topic: my-connect-cluster-status
        key.converter: org.apache.kafka.connect.json.JsonConverter
        value.converter: org.apache.kafka.connect.json.JsonConverter
        key.converter.schemas.enable: true
        value.converter.schemas.enable: true
        config.storage.replication.factor: 3
        offset.storage.replication.factor: 3
        status.storage.replication.factor: 3
      build: 8
        output: 9
          type: docker
          image: my-registry.io/my-org/my-connect-cluster:latest
          pushSecret: my-registry-credentials
        plugins: 10
          - name: debezium-postgres-connector
            artifacts:
              - type: tgz
                url: https://repo1.maven.org/maven2/io/debezium/debezium-connector-postgres/1.3.1.Final/debezium-connector-postgres-1.3.1.Final-plugin.tar.gz
                sha512sum: 962a12151bdf9a5a30627eebac739955a4fd95a08d373b86bdcea2b4d0c27dd6e1edd5cb548045e115e33a9e69b1b2a352bee24df035a0447cb820077af00c03
          - name: camel-telegram
            artifacts:
              - type: tgz
                url: https://repo.maven.apache.org/maven2/org/apache/camel/kafkaconnector/camel-telegram-kafka-connector/0.7.0/camel-telegram-kafka-connector-0.7.0-package.tar.gz
                sha512sum: a9b1ac63e3284bea7836d7d24d84208c49cdf5600070e6bd1535de654f6920b74ad950d51733e8020bf4187870699819f54ef5859c7846ee4081507f48873479
      externalConfiguration: 11
        env:
          - name: AWS_ACCESS_KEY_ID
            valueFrom:
              secretKeyRef:
                name: aws-creds
                key: awsAccessKey
          - name: AWS_SECRET_ACCESS_KEY
            valueFrom:
              secretKeyRef:
                name: aws-creds
                key: awsSecretAccessKey
      resources: 12
        requests:
          cpu: "1"
          memory: 2Gi
        limits:
          cpu: "2"
          memory: 2Gi
      logging: 13
        type: inline
        loggers:
          log4j.rootLogger: "INFO"
      readinessProbe: 14
        initialDelaySeconds: 15
        timeoutSeconds: 5
      livenessProbe:
        initialDelaySeconds: 15
        timeoutSeconds: 5
      metricsConfig: 15
        type: jmxPrometheusExporter
        valueFrom:
          configMapKeyRef:
            name: my-config-map
            key: my-key
      jvmOptions: 16
        "-Xmx": "1g"
        "-Xms": "1g"
      image: my-org/my-image:latest 17
      rack:
        topologyKey: topology.kubernetes.io/zone 18
      template: 19
        pod:
          affinity:
            podAntiAffinity:
              requiredDuringSchedulingIgnoredDuringExecution:
                - labelSelector:
                    matchExpressions:
                      - key: application
                        operator: In
                        values:
                          - postgresql
                          - mongodb
                  topologyKey: "kubernetes.io/hostname"
        connectContainer: 20
          env:
            - name: JAEGER_SERVICE_NAME
              value: my-jaeger-service
            - name: JAEGER_AGENT_HOST
              value: jaeger-agent-name
            - name: JAEGER_AGENT_PORT
              value: "6831"
    1
    Use KafkaConnect.
    2
    Enables KafkaConnectors for the Kafka Connect cluster.
    3
    The number of replica nodes for the workers that run tasks.
    4
    Authentication for the Kafka Connect cluster, using the TLS mechanism, as shown here, using OAuth bearer tokens, or a SASL-based SCRAM-SHA-256/SCRAM-SHA-512 or PLAIN mechanism. By default, Kafka Connect connects to Kafka brokers using a plain text connection.
    5
    Bootstrap server for connection to the Kafka Connect cluster.
    6
    TLS encryption with key names under which TLS certificates are stored in X.509 format for the cluster. If certificates are stored in the same secret, it can be listed multiple times.
    7
    Kafka Connect configuration of workers (not connectors). Standard Apache Kafka configuration may be provided, restricted to those properties not managed directly by AMQ Streams.
    8
    Build configuration properties for building a container image with connector plugins automatically.
    9
    (Required) Configuration of the container registry where new images are pushed.
    10
    (Required) List of connector plugins and their artifacts to add to the new container image. Each plugin must be configured with at least one artifact.
    11
    External configuration for Kafka connectors using environment variables, as shown here, or volumes. You can also use configuration provider plugins to load configuration values from external sources.
    12
    Requests for reservation of supported resources, currently cpu and memory, and limits to specify the maximum resources that can be consumed.
    13
    Specified Kafka Connect loggers and log levels added directly (inline) or indirectly (external) through a ConfigMap. A custom ConfigMap must be placed under the log4j.properties or log4j2.properties key. For the Kafka Connect log4j.rootLogger logger, you can set the log level to INFO, ERROR, WARN, TRACE, DEBUG, FATAL or OFF.
    14
    Healthchecks to know when to restart a container (liveness) and when a container can accept traffic (readiness).
    15
    Prometheus metrics, which are enabled by referencing a ConfigMap containing configuration for the Prometheus JMX exporter in this example. You can enable metrics without further configuration using a reference to a ConfigMap containing an empty file under metricsConfig.valueFrom.configMapKeyRef.key.
    16
    JVM configuration options to optimize performance for the Virtual Machine (VM) running Kafka Connect.
    17
    ADVANCED OPTION: Container image configuration, which is recommended only in special situations.
    18
    Rack awareness is configured to spread replicas across different racks. A topologykey must match the label of a cluster node.
    19
    Template customization. Here a pod is scheduled with anti-affinity, so the pod is not scheduled on nodes with the same hostname.
    20
    Environment variables are also set for distributed tracing using Jaeger.
  2. Create or update the resource:

    oc apply -f KAFKA-CONNECT-CONFIG-FILE
  3. If authorization is enabled for Kafka Connect, configure Kafka Connect users to enable access to the Kafka Connect consumer group and topics.

2.2.2. Kafka Connect configuration for multiple instances

If you are running multiple instances of Kafka Connect, you have to change the default configuration of the following config properties:

apiVersion: kafka.strimzi.io/v1beta2
kind: KafkaConnect
metadata:
  name: my-connect
spec:
  # ...
  config:
    group.id: connect-cluster 1
    offset.storage.topic: connect-cluster-offsets 2
    config.storage.topic: connect-cluster-configs 3
    status.storage.topic: connect-cluster-status  4
    # ...
# ...
1
The Kafka Connect cluster ID within Kafka.
2
Kafka topic that stores connector offsets.
3
Kafka topic that stores connector and task status configurations.
4
Kafka topic that stores connector and task status updates.
Note

Values for the three topics must be the same for all Kafka Connect instances with the same group.id.

Unless you change the default settings, each Kafka Connect instance connecting to the same Kafka cluster is deployed with the same values. What happens, in effect, is all instances are coupled to run in a cluster and use the same topics.

If multiple Kafka Connect clusters try to use the same topics, Kafka Connect will not work as expected and generate errors.

If you wish to run multiple Kafka Connect instances, change the values of these properties for each instance.

2.2.3. Configuring Kafka Connect user authorization

This procedure describes how to authorize user access to Kafka Connect.

When any type of authorization is being used in Kafka, a Kafka Connect user requires read/write access rights to the consumer group and the internal topics of Kafka Connect.

The properties for the consumer group and internal topics are automatically configured by AMQ Streams, or they can be specified explicitly in the spec of the KafkaConnect resource.

Example configuration properties in the KafkaConnect resource

apiVersion: kafka.strimzi.io/v1beta2
kind: KafkaConnect
metadata:
  name: my-connect
spec:
  # ...
  config:
    group.id: my-connect-cluster 1
    offset.storage.topic: my-connect-cluster-offsets 2
    config.storage.topic: my-connect-cluster-configs 3
    status.storage.topic: my-connect-cluster-status 4
    # ...
  # ...

1
The Kafka Connect cluster ID within Kafka.
2
Kafka topic that stores connector offsets.
3
Kafka topic that stores connector and task status configurations.
4
Kafka topic that stores connector and task status updates.

This procedure shows how access is provided when simple authorization is being used.

Simple authorization uses ACL rules, handled by the Kafka AclAuthorizer plugin, to provide the right level of access. For more information on configuring a KafkaUser resource to use simple authorization, see the AclRule schema reference.

Note

The default values for the consumer group and topics will differ when running multiple instances.

Prerequisites

  • An OpenShift cluster
  • A running Cluster Operator

Procedure

  1. Edit the authorization property in the KafkaUser resource to provide access rights to the user.

    In the following example, access rights are configured for the Kafka Connect topics and consumer group using literal name values:

    PropertyName

    offset.storage.topic

    connect-cluster-offsets

    status.storage.topic

    connect-cluster-status

    config.storage.topic

    connect-cluster-configs

    group

    connect-cluster

    apiVersion: kafka.strimzi.io/v1beta2
    kind: KafkaUser
    metadata:
      name: my-user
      labels:
        strimzi.io/cluster: my-cluster
    spec:
      # ...
      authorization:
        type: simple
        acls:
          # access to offset.storage.topic
          - resource:
              type: topic
              name: connect-cluster-offsets
              patternType: literal
            operation: Write
            host: "*"
          - resource:
              type: topic
              name: connect-cluster-offsets
              patternType: literal
            operation: Create
            host: "*"
          - resource:
              type: topic
              name: connect-cluster-offsets
              patternType: literal
            operation: Describe
            host: "*"
          - resource:
              type: topic
              name: connect-cluster-offsets
              patternType: literal
            operation: Read
            host: "*"
          # access to status.storage.topic
          - resource:
              type: topic
              name: connect-cluster-status
              patternType: literal
            operation: Write
            host: "*"
          - resource:
              type: topic
              name: connect-cluster-status
              patternType: literal
            operation: Create
            host: "*"
          - resource:
              type: topic
              name: connect-cluster-status
              patternType: literal
            operation: Describe
            host: "*"
          - resource:
              type: topic
              name: connect-cluster-status
              patternType: literal
            operation: Read
            host: "*"
          # access to config.storage.topic
          - resource:
              type: topic
              name: connect-cluster-configs
              patternType: literal
            operation: Write
            host: "*"
          - resource:
              type: topic
              name: connect-cluster-configs
              patternType: literal
            operation: Create
            host: "*"
          - resource:
              type: topic
              name: connect-cluster-configs
              patternType: literal
            operation: Describe
            host: "*"
          - resource:
              type: topic
              name: connect-cluster-configs
              patternType: literal
            operation: Read
            host: "*"
          # consumer group
          - resource:
              type: group
              name: connect-cluster
              patternType: literal
            operation: Read
            host: "*"
  2. Create or update the resource.

    oc apply -f KAFKA-USER-CONFIG-FILE

2.2.4. List of Kafka Connect cluster resources

The following resources are created by the Cluster Operator in the OpenShift cluster:

connect-cluster-name-connect
Deployment which is in charge to create the Kafka Connect worker node pods.
connect-cluster-name-connect-api
Service which exposes the REST interface for managing the Kafka Connect cluster.
connect-cluster-name-config
ConfigMap which contains the Kafka Connect ancillary configuration and is mounted as a volume by the Kafka broker pods.
connect-cluster-name-connect
Pod Disruption Budget configured for the Kafka Connect worker nodes.

2.2.5. Integrating with Debezium for change data capture

Red Hat Debezium is a distributed change data capture platform. It captures row-level changes in databases, creates change event records, and streams the records to Kafka topics. Debezium is built on Apache Kafka. You can deploy and integrate Debezium with AMQ Streams. Following a deployment of AMQ Streams, you deploy Debezium as a connector configuration through Kafka Connect. Debezium passes change event records to AMQ Streams on OpenShift. Applications can read these change event streams and access the change events in the order in which they occurred.

Debezium has multiple uses, including:

  • Data replication
  • Updating caches and search indexes
  • Simplifying monolithic applications
  • Data integration
  • Enabling streaming queries

To capture database changes, deploy Kafka Connect with a Debezium database connector. You configure a KafkaConnector resource to define the connector instance.

For more information on deploying Debezium with AMQ Streams, refer to the product documentation. The Debezium documentation includes a Getting Started with Debezium guide that guides you through the process of setting up the services and connector required to view change event records for database updates.

2.3. Kafka MirrorMaker cluster configuration

This chapter describes how to configure a Kafka MirrorMaker deployment in your AMQ Streams cluster to replicate data between Kafka clusters.

You can use AMQ Streams with MirrorMaker or MirrorMaker 2.0. MirrorMaker 2.0 is the latest version, and offers a more efficient way to mirror data between Kafka clusters.

If you are using MirrorMaker, you configure the KafkaMirrorMaker resource.

Important

Kafka MirrorMaker 1 (referred to as just MirrorMaker in the documentation) has been deprecated in Apache Kafka 3.0.0 and will be removed in Apache Kafka 4.0.0. As a result, the KafkaMirrorMaker custom resource which is used to deploy Kafka MirrorMaker 1 has been deprecated in AMQ Streams as well. The KafkaMirrorMaker resource will be removed from AMQ Streams when we adopt Apache Kafka 4.0.0. As a replacement, use the KafkaMirrorMaker2 custom resource with the IdentityReplicationPolicy.

The following procedure shows how the resource is configured:

The full schema of the KafkaMirrorMaker resource is described in the KafkaMirrorMaker schema reference.

2.3.1. Configuring Kafka MirrorMaker

Use the properties of the KafkaMirrorMaker resource to configure your Kafka MirrorMaker deployment.

You can configure access control for producers and consumers using TLS or SASL authentication. This procedure shows a configuration that uses TLS encryption and authentication on the consumer and producer side.

Prerequisites

  • See the Deploying and Upgrading AMQ Streams on OpenShift guide for instructions on running a:

  • Source and target Kafka clusters must be available

Procedure

  1. Edit the spec properties for the KafkaMirrorMaker resource.

    The properties you can configure are shown in this example configuration:

    apiVersion: kafka.strimzi.io/v1beta2
    kind: KafkaMirrorMaker
    metadata:
      name: my-mirror-maker
    spec:
      replicas: 3 1
      consumer:
        bootstrapServers: my-source-cluster-kafka-bootstrap:9092 2
        groupId: "my-group" 3
        numStreams: 2 4
        offsetCommitInterval: 120000 5
        tls: 6
          trustedCertificates:
          - secretName: my-source-cluster-ca-cert
            certificate: ca.crt
        authentication: 7
          type: tls
          certificateAndKey:
            secretName: my-source-secret
            certificate: public.crt
            key: private.key
        config: 8
          max.poll.records: 100
          receive.buffer.bytes: 32768
          ssl.cipher.suites: "TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384" 9
          ssl.enabled.protocols: "TLSv1.2"
          ssl.protocol: "TLSv1.2"
          ssl.endpoint.identification.algorithm: HTTPS 10
      producer:
        bootstrapServers: my-target-cluster-kafka-bootstrap:9092
        abortOnSendFailure: false 11
        tls:
          trustedCertificates:
          - secretName: my-target-cluster-ca-cert
            certificate: ca.crt
        authentication:
          type: tls
          certificateAndKey:
            secretName: my-target-secret
            certificate: public.crt
            key: private.key
        config:
          compression.type: gzip
          batch.size: 8192
          ssl.cipher.suites: "TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384" 12
          ssl.enabled.protocols: "TLSv1.2"
          ssl.protocol: "TLSv1.2"
          ssl.endpoint.identification.algorithm: HTTPS 13
      include: "my-topic|other-topic" 14
      resources: 15
        requests:
          cpu: "1"
          memory: 2Gi
        limits:
          cpu: "2"
          memory: 2Gi
      logging: 16
        type: inline
        loggers:
          mirrormaker.root.logger: "INFO"
      readinessProbe: 17
        initialDelaySeconds: 15
        timeoutSeconds: 5
      livenessProbe:
        initialDelaySeconds: 15
        timeoutSeconds: 5
      metricsConfig: 18
       type: jmxPrometheusExporter
       valueFrom:
         configMapKeyRef:
           name: my-config-map
           key: my-key
      jvmOptions: 19
        "-Xmx": "1g"
        "-Xms": "1g"
      image: my-org/my-image:latest 20
      template: 21
        pod:
          affinity:
            podAntiAffinity:
              requiredDuringSchedulingIgnoredDuringExecution:
                - labelSelector:
                    matchExpressions:
                      - key: application
                        operator: In
                        values:
                          - postgresql
                          - mongodb
                  topologyKey: "kubernetes.io/hostname"
        connectContainer: 22
          env:
            - name: JAEGER_SERVICE_NAME
              value: my-jaeger-service
            - name: JAEGER_AGENT_HOST
              value: jaeger-agent-name
            - name: JAEGER_AGENT_PORT
              value: "6831"
      tracing: 23
        type: jaeger
    1
    2
    Bootstrap servers for consumer and producer.
    3
    4
    5
    6
    TLS encryption with key names under which TLS certificates are stored in X.509 format for consumer or producer. If certificates are stored in the same secret, it can be listed multiple times.
    7
    Authentication for consumer or producer, using the TLS mechanism, as shown here, using OAuth bearer tokens, or a SASL-based SCRAM-SHA-256/SCRAM-SHA-512 or PLAIN mechanism.
    8
    Kafka configuration options for consumer and producer.
    9
    SSL properties for external listeners to run with a specific cipher suite for a TLS version.
    10
    Hostname verification is enabled by setting to HTTPS. An empty string disables the verification.
    11
    If the abortOnSendFailure property is set to true, Kafka MirrorMaker will exit and the container will restart following a send failure for a message.
    12
    SSL properties for external listeners to run with a specific cipher suite for a TLS version.
    13
    Hostname verification is enabled by setting to HTTPS. An empty string disables the verification.
    14
    A included topics mirrored from source to target Kafka cluster.
    15
    Requests for reservation of supported resources, currently cpu and memory, and limits to specify the maximum resources that can be consumed.
    16
    Specified loggers and log levels added directly (inline) or indirectly (external) through a ConfigMap. A custom ConfigMap must be placed under the log4j.properties or log4j2.properties key. MirrorMaker has a single logger called mirrormaker.root.logger. You can set the log level to INFO, ERROR, WARN, TRACE, DEBUG, FATAL or OFF.
    17
    Healthchecks to know when to restart a container (liveness) and when a container can accept traffic (readiness).
    18
    Prometheus metrics, which are enabled by referencing a ConfigMap containing configuration for the Prometheus JMX exporter in this example. You can enable metrics without further configuration using a reference to a ConfigMap containing an empty file under metricsConfig.valueFrom.configMapKeyRef.key.
    19
    JVM configuration options to optimize performance for the Virtual Machine (VM) running Kafka MirrorMaker.
    20
    ADVANCED OPTION: Container image configuration, which is recommended only in special situations.
    21
    Template customization. Here a pod is scheduled with anti-affinity, so the pod is not scheduled on nodes with the same hostname.
    22
    Environment variables are also set for distributed tracing using Jaeger.
    23
    Warning

    With the abortOnSendFailure property set to false, the producer attempts to send the next message in a topic. The original message might be lost, as there is no attempt to resend a failed message.

  2. Create or update the resource:

    oc apply -f <your-file>

2.3.2. List of Kafka MirrorMaker cluster resources

The following resources are created by the Cluster Operator in the OpenShift cluster:

<mirror-maker-name>-mirror-maker
Deployment which is responsible for creating the Kafka MirrorMaker pods.
<mirror-maker-name>-config
ConfigMap which contains ancillary configuration for the Kafka MirrorMaker, and is mounted as a volume by the Kafka broker pods.
<mirror-maker-name>-mirror-maker
Pod Disruption Budget configured for the Kafka MirrorMaker worker nodes.

2.4. Kafka MirrorMaker 2.0 cluster configuration

This section describes how to configure a Kafka MirrorMaker 2.0 deployment in your AMQ Streams cluster.

MirrorMaker 2.0 is used to replicate data between two or more active Kafka clusters, within or across data centers.

Data replication across clusters supports scenarios that require:

  • Recovery of data in the event of a system failure
  • Aggregation of data for analysis
  • Restriction of data access to a specific cluster
  • Provision of data at a specific location to improve latency

If you are using MirrorMaker 2.0, you configure the KafkaMirrorMaker2 resource. The full schema of the KafkaMirrorMaker2 resource is described in the KafkaMirrorMaker2 schema reference.

MirrorMaker 2.0 introduces an entirely new way of replicating data between clusters.

As a result, the resource configuration differs from the previous version of MirrorMaker. If you choose to use MirrorMaker 2.0, there is currently no legacy support, so any resources must be manually converted into the new format.

2.4.1. MirrorMaker 2.0 data replication

MirrorMaker 2.0 consumes messages from a source Kafka cluster and writes them to a target Kafka cluster.

MirrorMaker 2.0 uses:

  • Source cluster configuration to consume data from the source cluster
  • Target cluster configuration to output data to the target cluster

MirrorMaker 2.0 is based on the Kafka Connect framework, connectors managing the transfer of data between clusters. A MirrorMaker 2.0 MirrorSourceConnector replicates topics from a source cluster to a target cluster.

The process of mirroring data from one cluster to another cluster is asynchronous. The recommended pattern is for messages to be produced locally alongside the source Kafka cluster, then consumed remotely close to the target Kafka cluster.

MirrorMaker 2.0 can be used with more than one source cluster.

Figure 2.1. Replication across two clusters

MirrorMaker 2.0 replication

By default, a check for new topics in the source cluster is made every 10 minutes. You can change the frequency by adding refresh.topics.interval.seconds to the source connector configuration. However, increasing the frequency of the operation might affect overall performance.

2.4.2. Cluster configuration

You can use MirrorMaker 2.0 in active/passive or active/active cluster configurations.

  • In an active/active configuration, both clusters are active and provide the same data simultaneously, which is useful if you want to make the same data available locally in different geographical locations.
  • In an active/passive configuration, the data from an active cluster is replicated in a passive cluster, which remains on standby, for example, for data recovery in the event of system failure.

The expectation is that producers and consumers connect to active clusters only.

A MirrorMaker 2.0 cluster is required at each target destination.

2.4.2.1. Bidirectional replication (active/active)

The MirrorMaker 2.0 architecture supports bidirectional replication in an active/active cluster configuration.

Each cluster replicates the data of the other cluster using the concept of source and remote topics. As the same topics are stored in each cluster, remote topics are automatically renamed by MirrorMaker 2.0 to represent the source cluster. The name of the originating cluster is prepended to the name of the topic.

Figure 2.2. Topic renaming

MirrorMaker 2.0 bidirectional architecture

By flagging the originating cluster, topics are not replicated back to that cluster.

The concept of replication through remote topics is useful when configuring an architecture that requires data aggregation. Consumers can subscribe to source and remote topics within the same cluster, without the need for a separate aggregation cluster.

2.4.2.2. Unidirectional replication (active/passive)

The MirrorMaker 2.0 architecture supports unidirectional replication in an active/passive cluster configuration.

You can use an active/passive cluster configuration to make backups or migrate data to another cluster. In this situation, you might not want automatic renaming of remote topics.

You can override automatic renaming by adding IdentityReplicationPolicy to the source connector configuration. With this configuration applied, topics retain their original names.

2.4.2.3. Topic configuration synchronization

Topic configuration is automatically synchronized between source and target clusters. By synchronizing configuration properties, the need for rebalancing is reduced.

2.4.2.4. Data integrity

MirrorMaker 2.0 monitors source topics and propagates any configuration changes to remote topics, checking for and creating missing partitions. Only MirrorMaker 2.0 can write to remote topics.

2.4.2.5. Offset tracking

MirrorMaker 2.0 tracks offsets for consumer groups using internal topics.

  • The offset-syncs topic maps the source and target offsets for replicated topic partitions from record metadata
  • The checkpoints topic maps the last committed offset in the source and target cluster for replicated topic partitions in each consumer group

Offsets for the checkpoints topic are tracked at predetermined intervals through configuration. Both topics enable replication to be fully restored from the correct offset position on failover.

MirrorMaker 2.0 uses its MirrorCheckpointConnector to emit checkpoints for offset tracking.

The location of the offset-syncs topic is the source cluster by default. You can use the offset-syncs.topic.location connector configuration to change this to the target cluster. You need read/write access to the cluster that contains the topic. Using the target cluster as the location of the offset-syncs topic allows you to use MirrorMaker 2.0 even if you have only read access to the source cluster.

2.4.2.6. Synchronizing consumer group offsets

The __consumer_offsets topic stores information on committed offsets, for each consumer group. Offset synchronization periodically transfers the consumer offsets for the consumer groups of a source cluster into the consumer offsets topic of a target cluster.

Offset synchronization is particularly useful in an active/passive configuration. If the active cluster goes down, consumer applications can switch to the passive (standby) cluster and pick up from the last transferred offset position.

To use topic offset synchronization, enable the synchronization by adding sync.group.offsets.enabled to the checkpoint connector configuration, and setting the property to true. Synchronization is disabled by default.

When using the IdentityReplicationPolicy in the source connector, it also has to be configured in the checkpoint connector configuration. This ensures that the mirrored consumer offsets will be applied for the correct topics.

The consumer offsets are only synchronized for consumer groups that are not active in the target cluster.

If enabled, the synchronization of offsets from the source cluster is made periodically. You can change the frequency by adding sync.group.offsets.interval.seconds and emit.checkpoints.interval.seconds to the checkpoint connector configuration. The properties specify the frequency in seconds that the consumer group offsets are synchronized, and the frequency of checkpoints emitted for offset tracking. The default for both properties is 60 seconds. You can also change the frequency of checks for new consumer groups using the refresh.groups.interval.seconds property, which is performed every 10 minutes by default.

Because the synchronization is time-based, any switchover by consumers to a passive cluster will likely result in some duplication of messages.

2.4.2.7. Connectivity checks

A heartbeat internal topic checks connectivity between clusters.

The heartbeat topic is replicated from the source cluster.

Target clusters use the topic to check:

  • The connector managing connectivity between clusters is running
  • The source cluster is available

MirrorMaker 2.0 uses its MirrorHeartbeatConnector to emit heartbeats that perform these checks.

2.4.3. Connector configuration

Use Mirrormaker 2.0 connector configuration for the internal connectors that orchestrate the synchronization of data between Kafka clusters.

The following table describes connector properties and the connectors you configure to use them.

Table 2.1. MirrorMaker 2.0 connector configuration properties

PropertysourceConnectorcheckpointConnectorheartbeatConnector
admin.timeout.ms
Timeout for admin tasks, such as detecting new topics. Default is 60000 (1 minute).

replication.policy.class
Policy to define the remote topic naming convention. Default is org.apache.kafka.connect.mirror.DefaultReplicationPolicy.

replication.policy.separator
The separator used for topic naming in the target cluster. Default is . (dot). It is only used when the replication.policy.class is the DefaultReplicationPolicy.

consumer.poll.timeout.ms
Timeout when polling the source cluster. Default is 1000 (1 second).

 
offset-syncs.topic.location
The location of the offset-syncs topic, which can be the source (default) or target cluster.

 
topic.filter.class
Topic filter to select the topics to replicate. Default is org.apache.kafka.connect.mirror.DefaultTopicFilter.

 
config.property.filter.class
Topic filter to select the topic configuration properties to replicate. Default is org.apache.kafka.connect.mirror.DefaultConfigPropertyFilter.

  
config.properties.exclude
Topic configuration properties that should not be replicated. Supports comma-separated property names and regular expressions.

  
offset.lag.max
Maximum allowable (out-of-sync) offset lag before a remote partition is synchronized. Default is 100.

  
offset-syncs.topic.replication.factor
Replication factor for the internal offset-syncs topic. Default is 3.

  
refresh.topics.enabled
Enables check for new topics and partitions. Default is true.

  
refresh.topics.interval.seconds
Frequency of topic refresh. Default is 600 (10 minutes).

  
replication.factor
The replication factor for new topics. Default is 2.

  
sync.topic.acls.enabled
Enables synchronization of ACLs from the source cluster. Default is true. Not compatible with the User Operator.

  
sync.topic.acls.interval.seconds
Frequency of ACL synchronization. Default is 600 (10 minutes).

  
sync.topic.configs.enabled
Enables synchronization of topic configuration from the source cluster. Default is true.

  
sync.topic.configs.interval.seconds
Frequency of topic configuration synchronization. Default 600 (10 minutes).

  
checkpoints.topic.replication.factor
Replication factor for the internal checkpoints topic. Default is 3.
 

 
emit.checkpoints.enabled
Enables synchronization of consumer offsets to the target cluster. Default is true.
 

 
emit.checkpoints.interval.seconds
Frequency of consumer offset synchronization. Default is 60 (1 minute).
 

 
group.filter.class
Group filter to select the consumer groups to replicate. Default is org.apache.kafka.connect.mirror.DefaultGroupFilter.
 

 
refresh.groups.enabled
Enables check for new consumer groups. Default is true.
 

 
refresh.groups.interval.seconds
Frequency of consumer group refresh. Default is 600 (10 minutes).
 

 
sync.group.offsets.enabled
Enables synchronization of consumer group offsets to the target cluster __consumer_offsets topic. Default is false.
 

 
sync.group.offsets.interval.seconds
Frequency of consumer group offset synchronization. Default is 60 (1 minute).
 

 
emit.heartbeats.enabled
Enables connectivity checks on the target cluster. Default is true.
  

emit.heartbeats.interval.seconds
Frequency of connectivity checks. Default is 1 (1 second).
  

heartbeats.topic.replication.factor
Replication factor for the internal heartbeats topic. Default is 3.
  

2.4.4. Specifying a maximum number of tasks

Connectors create the tasks that are responsible for moving data in and out of Kafka. Each connector comprises one or more tasks that are distributed across a group of worker pods that run the tasks.

Tasks run in parallel. Workers are assigned one or more tasks. A single task is handled by one worker pod, so you don’t need more worker pods than tasks. If there are more tasks than workers, workers handle multiple tasks.

You can specify the maximum number of connector tasks in your MirrorMaker configuration using the tasksMax property. Without specifying a maximum number of tasks, the default setting is a single task. If the infrastructure supports the processing overhead, increasing the number of tasks can improve throughput.

tasksMax configuration for a MirrorMaker connector

apiVersion: kafka.strimzi.io/v1beta2
kind: KafkaMirrorMaker2
metadata:
  name: my-mirror-maker2
spec:
  # ...
  mirrors:
  - sourceCluster: "my-cluster-source"
    targetCluster: "my-cluster-target"
    sourceConnector:
      tasksMax: 10
  # ...

For the source connector, the maximum number of tasks possible is one for each partition being replicated from the source cluster. For the checkpoint connector, the maximum number of tasks possible is one for each group being replicated from the source cluster. The number of tasks that are started for these connectors is the lower value between the maximum number of possible tasks and the value for tasksMax.

The heartbeat connector always uses a single task.

2.4.5. Handling high volumes of messages

If your MirrorMaker 2.0 deployment is going to be handling a high volume of messages, you might need to adjust its configuration to support it.

The flush pipeline for data replication is source topic → (Kafka Connect) source message queue → producer buffer → target topic. An offset flush timeout period (offset.flush.timeout.ms) is the time to wait for the producer buffer (producer.buffer.memory) to flush and offset data to be committed. Try to avoid a situation where a large producer buffer and an insufficient offset flush timeout period causes a failed to flush or failed to commit offsets type of error.

This type of error means that there are too many messages in the producer buffer, so they can’t all be flushed before the offset flush timeout is reached.

If you are getting this type of error, try the following configuration changes:

  • Decreasing the default value in bytes of the producer.buffer.memory
  • Increasing the default value in milliseconds of the offset.flush.timeout.ms

The changes should help to keep the underlying Kafka Connect queue of outstanding messages at a manageable size. You might need to adjust the values to have the desired effect.

If these configuration changes don’t resolve the error, you can try increasing the number of tasks that run in parallel by doing the following.

  • Increasing the number of tasks using the tasksMax property
  • Increasing the number of nodes for the workers that run tasks using the replicas property

Example MirrorMaker 2.0 configuration for handling high volumes of messages

apiVersion: kafka.strimzi.io/v1beta2
kind: KafkaMirrorMaker2
metadata:
  name: my-mirror-maker2
spec:
  version: 3.1.0
  replicas: 5
  connectCluster: "my-cluster-target"
  clusters:
  - alias: "my-cluster-source"
    bootstrapServers: my-cluster-source-kafka-bootstrap:9092
  - alias: "my-cluster-target"
    config:
      offset.flush.timeout.ms: 10000
      producer.buffer.memory: 8388608
    bootstrapServers: my-cluster-target-kafka-bootstrap:9092
  mirrors:
  - sourceCluster: "my-cluster-source"
    targetCluster: "my-cluster-target"
    sourceConnector:
      tasksMax: 10

2.4.5.1. Checking the message flow

If you are using Prometheus and Grafana to monitor your deployment, you can check the MirrorMaker 2.0 message flow. The example MirrorMaker 2.0 Grafana dashboard provided with AMQ Streams shows the following metrics related to the flush pipeline.

  • The number of messages in Kafka Connect’s outstanding messages queue
  • The available bytes of the producer buffer
  • The offset commit timeout in milliseconds

You can use these metrics to gauge whether or not you need to tune your configuration based on the volume of messages.

Additional resources

2.4.6. ACL rules synchronization

ACL access to remote topics is possible if you are not using the User Operator.

If AclAuthorizer is being used, without the User Operator, ACL rules that manage access to brokers also apply to remote topics. Users that can read a source topic can read its remote equivalent.

Note

OAuth 2.0 authorization does not support access to remote topics in this way.

2.4.7. Configuring Kafka MirrorMaker 2.0

Use the properties of the KafkaMirrorMaker2 resource to configure your Kafka MirrorMaker 2.0 deployment. Use MirrorMaker 2.0 to synchronize data between Kafka clusters

The configuration must specify:

  • Each Kafka cluster
  • Connection information for each cluster, including TLS authentication
  • The replication flow and direction

    • Cluster to cluster
    • Topic to topic
Note

The previous version of MirrorMaker continues to be supported. If you wish to use the resources configured for the previous version, they must be updated to the format supported by MirrorMaker 2.0.

MirrorMaker 2.0 provides default configuration values for properties such as replication factors. A minimal configuration, with defaults left unchanged, would be something like this example:

Minimal configuration for MirrorMaker 2.0

apiVersion: kafka.strimzi.io/v1beta2
kind: KafkaMirrorMaker2
metadata:
  name: my-mirror-maker2
spec:
  version: 3.1.0
  connectCluster: "my-cluster-target"
  clusters:
  - alias: "my-cluster-source"
    bootstrapServers: my-cluster-source-kafka-bootstrap:9092
  - alias: "my-cluster-target"
    bootstrapServers: my-cluster-target-kafka-bootstrap:9092
  mirrors:
  - sourceCluster: "my-cluster-source"
    targetCluster: "my-cluster-target"
    sourceConnector: {}

You can configure access control for source and target clusters using TLS or SASL authentication. This procedure shows a configuration that uses TLS encryption and authentication for the source and target cluster.

Prerequisites

  • AMQ Streams is running
  • Source and target Kafka clusters are available

Procedure

  1. Edit the spec properties for the KafkaMirrorMaker2 resource.

    The properties you can configure are shown in this example configuration:

    apiVersion: kafka.strimzi.io/v1beta2
    kind: KafkaMirrorMaker2
    metadata:
      name: my-mirror-maker2
    spec:
      version: 3.1.0 1
      replicas: 3 2
      connectCluster: "my-cluster-target" 3
      clusters: 4
      - alias: "my-cluster-source" 5
        authentication: 6
          certificateAndKey:
            certificate: source.crt
            key: source.key
            secretName: my-user-source
          type: tls
        bootstrapServers: my-cluster-source-kafka-bootstrap:9092 7
        tls: 8
          trustedCertificates:
          - certificate: ca.crt
            secretName: my-cluster-source-cluster-ca-cert
      - alias: "my-cluster-target" 9
        authentication: 10
          certificateAndKey:
            certificate: target.crt
            key: target.key
            secretName: my-user-target
          type: tls
        bootstrapServers: my-cluster-target-kafka-bootstrap:9092 11
        config: 12
          config.storage.replication.factor: 1
          offset.storage.replication.factor: 1
          status.storage.replication.factor: 1
          ssl.cipher.suites: "TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384" 13
          ssl.enabled.protocols: "TLSv1.2"
          ssl.protocol: "TLSv1.2"
          ssl.endpoint.identification.algorithm: HTTPS 14
        tls: 15
          trustedCertificates:
          - certificate: ca.crt
            secretName: my-cluster-target-cluster-ca-cert
      mirrors: 16
      - sourceCluster: "my-cluster-source" 17
        targetCluster: "my-cluster-target" 18
        sourceConnector: 19
          tasksMax: 10 20
          config:
            replication.factor: 1 21
            offset-syncs.topic.replication.factor: 1 22
            sync.topic.acls.enabled: "false" 23
            refresh.topics.interval.seconds: 60 24
            replication.policy.separator: "" 25
            replication.policy.class: "org.apache.kafka.connect.mirror.IdentityReplicationPolicy" 26
        heartbeatConnector: 27
          config:
            heartbeats.topic.replication.factor: 1 28
        checkpointConnector: 29
          config:
            checkpoints.topic.replication.factor: 1 30
            refresh.groups.interval.seconds: 600 31
            sync.group.offsets.enabled: true 32
            sync.group.offsets.interval.seconds: 60 33
            emit.checkpoints.interval.seconds: 60 34
            replication.policy.class: "org.apache.kafka.connect.mirror.IdentityReplicationPolicy"
        topicsPattern: ".*" 35
        groupsPattern: "group1|group2|group3" 36
      resources: 37
        requests:
          cpu: "1"
          memory: 2Gi
        limits:
          cpu: "2"
          memory: 2Gi
      logging: 38
        type: inline
        loggers:
          connect.root.logger.level: "INFO"
      readinessProbe: 39
        initialDelaySeconds: 15
        timeoutSeconds: 5
      livenessProbe:
        initialDelaySeconds: 15
        timeoutSeconds: 5
      jvmOptions: 40
        "-Xmx": "1g"
        "-Xms": "1g"
      image: my-org/my-image:latest 41
      template: 42
        pod:
          affinity:
            podAntiAffinity:
              requiredDuringSchedulingIgnoredDuringExecution:
                - labelSelector:
                    matchExpressions:
                      - key: application
                        operator: In
                        values:
                          - postgresql
                          - mongodb
                  topologyKey: "kubernetes.io/hostname"
        connectContainer: 43
          env:
            - name: JAEGER_SERVICE_NAME
              value: my-jaeger-service
            - name: JAEGER_AGENT_HOST
              value: jaeger-agent-name
            - name: JAEGER_AGENT_PORT
              value: "6831"
      tracing:
        type: jaeger 44
      externalConfiguration: 45
        env:
          - name: AWS_ACCESS_KEY_ID
            valueFrom:
              secretKeyRef:
                name: aws-creds
                key: awsAccessKey
          - name: AWS_SECRET_ACCESS_KEY
            valueFrom:
              secretKeyRef:
                name: aws-creds
                key: awsSecretAccessKey
    1
    The Kafka Connect and Mirror Maker 2.0 version, which will always be the same.
    2
    The number of replica nodes for the workers that run tasks.
    3
    Kafka cluster alias for Kafka Connect, which must specify the target Kafka cluster. The Kafka cluster is used by Kafka Connect for its internal topics.
    4
    Specification for the Kafka clusters being synchronized.
    5
    Cluster alias for the source Kafka cluster.
    6
    Authentication for the source cluster, using the TLS mechanism, as shown here, using OAuth bearer tokens, or a SASL-based SCRAM-SHA-256/SCRAM-SHA-512 or PLAIN mechanism.
    7
    Bootstrap server for connection to the source Kafka cluster.
    8
    TLS encryption with key names under which TLS certificates are stored in X.509 format for the source Kafka cluster. If certificates are stored in the same secret, it can be listed multiple times.
    9
    Cluster alias for the target Kafka cluster.
    10
    Authentication for the target Kafka cluster is configured in the same way as for the source Kafka cluster.
    11
    Bootstrap server for connection to the target Kafka cluster.
    12
    Kafka Connect configuration. Standard Apache Kafka configuration may be provided, restricted to those properties not managed directly by AMQ Streams.
    13
    SSL properties for external listeners to run with a specific cipher suite for a TLS version.
    14
    Hostname verification is enabled by setting to HTTPS. An empty string disables the verification.
    15
    TLS encryption for the target Kafka cluster is configured in the same way as for the source Kafka cluster.
    16
    17
    Cluster alias for the source cluster used by the MirrorMaker 2.0 connectors.
    18
    Cluster alias for the target cluster used by the MirrorMaker 2.0 connectors.
    19
    Configuration for the MirrorSourceConnector that creates remote topics. The config overrides the default configuration options.
    20
    The maximum number of tasks that the connector may create. Tasks handle the data replication and run in parallel. If the infrastructure supports the processing overhead, increasing this value can improve throughput. Kafka Connect distributes the tasks between members of the cluster. If there are more tasks than workers, workers are assigned multiple tasks. For sink connectors, aim to have one task for each topic partition consumed. For source connectors, the number of tasks that can run in parallel may also depend on the external system. The connector creates fewer than the maximum number of tasks if it cannot achieve the parallelism.
    21
    Replication factor for mirrored topics created at the target cluster.
    22
    Replication factor for the MirrorSourceConnector offset-syncs internal topic that maps the offsets of the source and target clusters.
    23
    When ACL rules synchronization is enabled, ACLs are applied to synchronized topics. The default is true. This feature is not compatible with the User Operator. If you are using the User Operator, set this property to false.
    24
    Optional setting to change the frequency of checks for new topics. The default is for a check every 10 minutes.
    25
    Defines the separator used for the renaming of remote topics.
    26
    Adds a policy that overrides the automatic renaming of remote topics. Instead of prepending the name with the name of the source cluster, the topic retains its original name. This optional setting is useful for active/passive backups and data migration. To configure topic offset synchronization, this property must also be set for the checkpointConnector.config.
    27
    Configuration for the MirrorHeartbeatConnector that performs connectivity checks. The config overrides the default configuration options.
    28
    Replication factor for the heartbeat topic created at the target cluster.
    29
    Configuration for the MirrorCheckpointConnector that tracks offsets. The config overrides the default configuration options.
    30
    Replication factor for the checkpoints topic created at the target cluster.
    31
    Optional setting to change the frequency of checks for new consumer groups. The default is for a check every 10 minutes.
    32
    Optional setting to synchronize consumer group offsets, which is useful for recovery in an active/passive configuration. Synchronization is not enabled by default.
    33
    If the synchronization of consumer group offsets is enabled, you can adjust the frequency of the synchronization.
    34
    Adjusts the frequency of checks for offset tracking. If you change the frequency of offset synchronization, you might also need to adjust the frequency of these checks.
    35
    Topic replication from the source cluster defined as regular expression patterns. Here we request all topics.
    36
    Consumer group replication from the source cluster defined as regular expression patterns. Here we request three consumer groups by name. You can use comma-separated lists.
    37
    Requests for reservation of supported resources, currently cpu and memory, and limits to specify the maximum resources that can be consumed.
    38
    Specified Kafka Connect loggers and log levels added directly (inline) or indirectly (external) through a ConfigMap. A custom ConfigMap must be placed under the log4j.properties or log4j2.properties key. For the Kafka Connect log4j.rootLogger logger, you can set the log level to INFO, ERROR, WARN, TRACE, DEBUG, FATAL or OFF.
    39
    Healthchecks to know when to restart a container (liveness) and when a container can accept traffic (readiness).
    40
    JVM configuration options to optimize performance for the Virtual Machine (VM) running Kafka MirrorMaker.
    41
    ADVANCED OPTION: Container image configuration, which is recommended only in special situations.
    42
    Template customization. Here a pod is scheduled with anti-affinity, so the pod is not scheduled on nodes with the same hostname.
    43
    Environment variables are also set for distributed tracing using Jaeger.
    44
    45
    External configuration for an OpenShift Secret mounted to Kafka MirrorMaker as an environment variable. You can also use configuration provider plugins to load configuration values from external sources.
  2. Create or update the resource:

    oc apply -f MIRRORMAKER-CONFIGURATION-FILE

2.4.8. Securing a Kafka MirrorMaker 2.0 deployment

This procedure describes in outline the configuration required to secure a MirrorMaker 2.0 deployment.

You need separate configuration for the source Kafka cluster and the target Kafka cluster. You also need separate user configuration to provide the credentials required for MirrorMaker to connect to the source and target Kafka clusters.

For the Kafka clusters, you specify internal listeners for secure connections within an OpenShift cluster and external listeners for connections outside the OpenShift cluster.

You can configure authentication and authorization mechanisms. The security options implemented for the source and target Kafka clusters must be compatible with the security options implemented for MirrorMaker 2.0.

After you have created the cluster and user authentication credentials, you specify them in your MirrorMaker configuration for secure connections.

Note

In this procedure, the certificates generated by the Cluster Operator are used, but you can replace them by installing your own certificates. You can also configure your listener to use a Kafka listener certificate managed by an external Certificate Authority.

Before you start

Before starting this procedure, take a look at the example configuration files provided by AMQ Streams. They include examples for securing a deployment of MirrorMaker 2.0 using TLS or SCRAM-SHA-512 authentication. The examples specify internal listeners for connecting within an OpenShift cluster.

The examples also show the ACLs needed by MirrorMaker 2.0 to allow operations on the source and target Kafka clusters.

Prerequisites

  • AMQ Streams is running
  • Separate namespaces for source and target clusters

The procedure assumes that the source and target Kafka clusters are installed to separate namespaces If you want to use the Topic Operator, you’ll need to do this. The Topic Operator only watches a single cluster in a specified namespace.

By separating the clusters into namespaces, you will need to copy the cluster secrets so they can be accessed outside the namespace. You need to reference the secrets in the MirrorMaker configuration.

Procedure

  1. Configure two Kafka resources, one to secure the source Kafka cluster and one to secure the target Kafka cluster.

    You can add listener configuration for authentication and enable authorization.

    In this example, an internal listener is configured for a Kafka cluster with TLS encryption and authentication. Kafka simple authorization is enabled.

    Example source Kafka cluster configuration with TLS authentication

    apiVersion: kafka.strimzi.io/v1beta2
    kind: Kafka
    metadata:
      name: my-source-cluster
    spec:
      kafka:
        version: 3.1.0
        replicas: 1
        listeners:
          - name: tls
            port: 9093
            type: internal
            tls: true
            authentication:
              type: tls
        authorization:
          type: simple
        config:
          offsets.topic.replication.factor: 1
          transaction.state.log.replication.factor: 1
          transaction.state.log.min.isr: 1
          default.replication.factor: 1
          min.insync.replicas: 1
          inter.broker.protocol.version: "3.1"
        storage:
          type: jbod
          volumes:
          - id: 0
            type: persistent-claim
            size: 100Gi
            deleteClaim: false
      zookeeper:
        replicas: 1
        storage:
          type: persistent-claim
          size: 100Gi
          deleteClaim: false
      entityOperator:
        topicOperator: {}
        userOperator: {}

    Example target Kafka cluster configuration with TLS authentication

    apiVersion: kafka.strimzi.io/v1beta2
    kind: Kafka
    metadata:
      name: my-target-cluster
    spec:
      kafka:
        version: 3.1.0
        replicas: 1
        listeners:
          - name: tls
            port: 9093
            type: internal
            tls: true
            authentication:
              type: tls
        authorization:
          type: simple
        config:
          offsets.topic.replication.factor: 1
          transaction.state.log.replication.factor: 1
          transaction.state.log.min.isr: 1
          default.replication.factor: 1
          min.insync.replicas: 1
          inter.broker.protocol.version: "3.1"
        storage:
          type: jbod
          volumes:
            - id: 0
              type: persistent-claim
              size: 100Gi
              deleteClaim: false
      zookeeper:
        replicas: 1
        storage:
          type: persistent-claim
          size: 100Gi
          deleteClaim: false
      entityOperator:
        topicOperator: {}
        userOperator: {}

  2. Create or update the Kafka resources in separate namespaces.

    oc apply -f <kafka_configuration_file> -n <namespace>

    The Cluster Operator creates the listeners and sets up the cluster and client certificate authority (CA) certificates to enable authentication within the Kafka cluster.

    The certificates are created in the secret <cluster_name>-cluster-ca-cert.

  3. Configure two KafkaUser resources, one for a user of the source Kafka cluster and one for a user of the target Kafka cluster.

    1. Configure the same authentication and authorization types as the corresponding source and target Kafka cluster. For example, if you used tls authentication and simple authorization type in the Kafka configuration for the source Kafka cluster, use the same in the KafkaUser configuration.
    2. Configure the ACLs needed by MirrorMaker 2.0 to allow operations on the source and target Kafka clusters.

      The ACLs are used by the internal MirrorMaker connectors, and by the underlying Kafka Connect framework.

    Example source user configuration for TLS client authentication

    apiVersion: kafka.strimzi.io/v1beta2
    kind: KafkaUser
    metadata:
      name: my-source-user
      labels:
        strimzi.io/cluster: my-source-cluster
    spec:
      authentication:
        type: tls
      authorization:
        type: simple
        acls:
          # MirrorSourceConnector
          - resource: # Not needed if offset-syncs.topic.location=target
              type: topic
              name: mm2-offset-syncs.my-target-cluster.internal
            operation: Create
          - resource: # Not needed if offset-syncs.topic.location=target
              type: topic
              name: mm2-offset-syncs.my-target-cluster.internal
            operation: DescribeConfigs
          - resource: # Not needed if offset-syncs.topic.location=target
              type: topic
              name: mm2-offset-syncs.my-target-cluster.internal
            operation: Write
          - resource: # Needed for every topic which is mirrored
              type: topic
              name: "*"
            operation: Read
          - resource: # Needed for every topic which is mirrored
              type: topic
              name: "*"
            operation: DescribeConfigs
          # MirrorCheckpointConnector
          - resource:
              type: cluster
            operation: Describe
          - resource: # Needed for every group for which offsets are synced
              type: group
              name: "*"
            operation: Describe
          - resource: # Not needed if offset-syncs.topic.location=target
              type: topic
              name: mm2-offset-syncs.my-target-cluster.internal
            operation: Read

    Example target user configuration for TLS client authentication

    apiVersion: kafka.strimzi.io/v1beta2
    kind: KafkaUser
    metadata:
      name: my-target-user
      labels:
        strimzi.io/cluster: my-target-cluster
    spec:
      authentication:
        type: tls
      authorization:
        type: simple
        acls:
          # Underlying Kafka Connect internal topics to store configuration, offsets, or status
          - resource:
              type: group
              name: mirrormaker2-cluster
            operation: Read
          - resource:
              type: topic
              name: mirrormaker2-cluster-configs
            operation: Read
          - resource:
              type: topic
              name: mirrormaker2-cluster-configs
            operation: Describe
          - resource:
              type: topic
              name: mirrormaker2-cluster-configs
            operation: DescribeConfigs
          - resource:
              type: topic
              name: mirrormaker2-cluster-configs
            operation: Write
          - resource:
              type: topic
              name: mirrormaker2-cluster-configs
            operation: Create
          - resource:
              type: topic
              name: mirrormaker2-cluster-status
            operation: Read
          - resource:
              type: topic
              name: mirrormaker2-cluster-status
            operation: Describe
          - resource:
              type: topic
              name: mirrormaker2-cluster-status
            operation: DescribeConfigs
          - resource:
              type: topic
              name: mirrormaker2-cluster-status
            operation: Write
          - resource:
              type: topic
              name: mirrormaker2-cluster-status
            operation: Create
          - resource:
              type: topic
              name: mirrormaker2-cluster-offsets
            operation: Read
          - resource:
              type: topic
              name: mirrormaker2-cluster-offsets
            operation: Write
          - resource:
              type: topic
              name: mirrormaker2-cluster-offsets
            operation: Describe
          - resource:
              type: topic
              name: mirrormaker2-cluster-offsets
            operation: DescribeConfigs
          - resource:
              type: topic
              name: mirrormaker2-cluster-offsets
            operation: Create
          # MirrorSourceConnector
          - resource: # Needed for every topic which is mirrored
              type: topic
              name: "*"
            operation: Create
          - resource: # Needed for every topic which is mirrored
              type: topic
              name: "*"
            operation: Alter
          - resource: # Needed for every topic which is mirrored
              type: topic
              name: "*"
            operation: AlterConfigs
          - resource: # Needed for every topic which is mirrored
              type: topic
              name: "*"
            operation: Write
          # MirrorCheckpointConnector
          - resource:
              type: cluster
            operation: Describe
          - resource:
              type: topic
              name: my-source-cluster.checkpoints.internal
            operation: Create
          - resource:
              type: topic
              name: my-source-cluster.checkpoints.internal
            operation: Describe
          - resource:
              type: topic
              name: my-source-cluster.checkpoints.internal
            operation: Write
          - resource: # Needed for every group for which the offset is synced
              type: group
              name: "*"
            operation: Read
          - resource: # Needed for every group for which the offset is synced
              type: group
              name: "*"
            operation: Describe
          - resource: # Needed for every topic which is mirrored
              type: topic
              name: "*"
            operation: Read
          # MirrorHeartbeatConnector
          - resource:
              type: topic
              name: heartbeats
            operation: Create
          - resource:
              type: topic
              name: heartbeats
            operation: Describe
          - resource:
              type: topic
              name: heartbeats
            operation: Write

    Note

    You can use a certificate issued outside the User Operator by setting type to tls-external. For more information, see User authentication.

  4. Create or update a KafkaUser resource in each of the namespaces you created for the source and target Kafka clusters.

    oc apply -f <kafka_user_configuration_file> -n <namespace>

    The User Operator creates the users representing the client (MirrorMaker), and the security credentials used for client authentication, based on the chosen authentication type.

    The User Operator creates a new secret with the same name as the KafkaUser resource. The secret contains a private and public key for TLS client authentication. The public key is contained in a user certificate, which is signed by the client Certificate Authority (CA).

  5. Configure a KafkaMirrorMaker2 resource with the authentication details to connect to the source and target Kafka clusters.

    Example MirrorMaker 2.0 configuration with TLS authentication

    apiVersion: kafka.strimzi.io/v1beta2
    kind: KafkaMirrorMaker2
    metadata:
      name: my-mirror-maker-2
    spec:
      version: 3.1.0
      replicas: 1
      connectCluster: "my-target-cluster"
      clusters:
        - alias: "my-source-cluster"
          bootstrapServers: my-source-cluster-kafka-bootstrap:9093
          tls: 1
            trustedCertificates:
              - secretName: my-source-cluster-cluster-ca-cert
                certificate: ca.crt
          authentication: 2
            type: tls
            certificateAndKey:
              secretName: my-source-user
              certificate: user.crt
              key: user.key
        - alias: "my-target-cluster"
          bootstrapServers: my-target-cluster-kafka-bootstrap:9093
          tls: 3
            trustedCertificates:
              - secretName: my-target-cluster-cluster-ca-cert
                certificate: ca.crt
          authentication: 4
            type: tls
            certificateAndKey:
              secretName: my-target-user
              certificate: user.crt
              key: user.key
          config:
            # -1 means it will use the default replication factor configured in the broker
            config.storage.replication.factor: -1
            offset.storage.replication.factor: -1
            status.storage.replication.factor: -1
      mirrors:
        - sourceCluster: "my-source-cluster"
          targetCluster: "my-target-cluster"
          sourceConnector:
            config:
              replication.factor: 1
              offset-syncs.topic.replication.factor: 1
              sync.topic.acls.enabled: "false"
          heartbeatConnector:
            config:
              heartbeats.topic.replication.factor: 1
          checkpointConnector:
            config:
              checkpoints.topic.replication.factor: 1
              sync.group.offsets.enabled: "true"
          topicsPattern: ".*"
          groupsPattern: ".*"

    1
    The TLS certificates for the source Kafka cluster. If they are in a separate namespace, copy the cluster secrets from the namespace of the Kafka cluster.
    2
    The user authentication for accessing the source Kafka cluster using the TLS mechanism.
    3
    The TLS certificates for the target Kafka cluster.
    4
    The user authentication for accessing the target Kafka cluster.
  6. Create or update the KafkaMirrorMaker2 resource in the same namespace as the target Kafka cluster.

    oc apply -f <mirrormaker2_configuration_file> -n <namespace_of_target_cluster>

2.4.9. Performing a restart of a Kafka MirrorMaker 2.0 connector

This procedure describes how to manually trigger a restart of a Kafka MirrorMaker 2.0 connector by using an OpenShift annotation.

Prerequisites

  • The Cluster Operator is running.

Procedure

  1. Find the name of the KafkaMirrorMaker2 custom resource that controls the Kafka MirrorMaker 2.0 connector you want to restart:

    oc get KafkaMirrorMaker2
  2. Find the name of the Kafka MirrorMaker 2.0 connector to be restarted from the KafkaMirrorMaker2 custom resource.

    oc describe KafkaMirrorMaker2 KAFKAMIRRORMAKER-2-NAME
  3. To restart the connector, annotate the KafkaMirrorMaker2 resource in OpenShift. In this example, oc annotate restarts a connector named my-source->my-target.MirrorSourceConnector:

    oc annotate KafkaMirrorMaker2 KAFKAMIRRORMAKER-2-NAME "strimzi.io/restart-connector=my-source->my-target.MirrorSourceConnector"
  4. Wait for the next reconciliation to occur (every two minutes by default).

    The Kafka MirrorMaker 2.0 connector is restarted, as long as the annotation was detected by the reconciliation process. When the restart request is accepted, the annotation is removed from the KafkaMirrorMaker2 custom resource.

2.4.10. Performing a restart of a Kafka MirrorMaker 2.0 connector task

This procedure describes how to manually trigger a restart of a Kafka MirrorMaker 2.0 connector task by using an OpenShift annotation.

Prerequisites

  • The Cluster Operator is running.

Procedure

  1. Find the name of the KafkaMirrorMaker2 custom resource that controls the Kafka MirrorMaker 2.0 connector you want to restart:

    oc get KafkaMirrorMaker2
  2. Find the name of the Kafka MirrorMaker 2.0 connector and the ID of the task to be restarted from the KafkaMirrorMaker2 custom resource. Task IDs are non-negative integers, starting from 0.

    oc describe KafkaMirrorMaker2 KAFKAMIRRORMAKER-2-NAME
  3. To restart the connector task, annotate the KafkaMirrorMaker2 resource in OpenShift. In this example, oc annotate restarts task 0 of a connector named my-source->my-target.MirrorSourceConnector:

    oc annotate KafkaMirrorMaker2 KAFKAMIRRORMAKER-2-NAME "strimzi.io/restart-connector-task=my-source->my-target.MirrorSourceConnector:0"
  4. Wait for the next reconciliation to occur (every two minutes by default).

    The Kafka MirrorMaker 2.0 connector task is restarted, as long as the annotation was detected by the reconciliation process. When the restart task request is accepted, the annotation is removed from the KafkaMirrorMaker2 custom resource.

2.5. Kafka Bridge cluster configuration

This section describes how to configure a Kafka Bridge deployment in your AMQ Streams cluster.

Kafka Bridge provides an API for integrating HTTP-based clients with a Kafka cluster.

If you are using the Kafka Bridge, you configure the KafkaBridge resource.

The full schema of the KafkaBridge resource is described in Section 13.2.112, “KafkaBridge schema reference”.

2.5.1. Configuring the Kafka Bridge

Use the Kafka Bridge to make HTTP-based requests to the Kafka cluster.

Use the properties of the KafkaBridge resource to configure your Kafka Bridge deployment.

In order to prevent issues arising when client consumer requests are processed by different Kafka Bridge instances, address-based routing must be employed to ensure that requests are routed to the right Kafka Bridge instance. Additionally, each independent Kafka Bridge instance must have a replica. A Kafka Bridge instance has its own state which is not shared with another instances.

Prerequisites

  • An OpenShift cluster
  • A running Cluster Operator

See the Deploying and Upgrading AMQ Streams on OpenShift guide for instructions on running a:

Procedure

  1. Edit the spec properties for the KafkaBridge resource.

    The properties you can configure are shown in this example configuration:

    apiVersion: kafka.strimzi.io/v1beta2
    kind: KafkaBridge
    metadata:
      name: my-bridge
    spec:
      replicas: 3 1
      bootstrapServers: <cluster_name>-cluster-kafka-bootstrap:9092 2
      tls: 3
        trustedCertificates:
          - secretName: my-cluster-cluster-cert
            certificate: ca.crt
          - secretName: my-cluster-cluster-cert
            certificate: ca2.crt
      authentication: 4
        type: tls
        certificateAndKey:
          secretName: my-secret
          certificate: public.crt
          key: private.key
      http: 5
        port: 8080
        cors: 6
          allowedOrigins: "https://strimzi.io"
          allowedMethods: "GET,POST,PUT,DELETE,OPTIONS,PATCH"
      consumer: 7
        config:
          auto.offset.reset: earliest
      producer: 8
        config:
          delivery.timeout.ms: 300000
      resources: 9
        requests:
          cpu: "1"
          memory: 2Gi
        limits:
          cpu: "2"
          memory: 2Gi
      logging: 10
        type: inline
        loggers:
          logger.bridge.level: "INFO"
          # enabling DEBUG just for send operation
          logger.send.name: "http.openapi.operation.send"
          logger.send.level: "DEBUG"
      jvmOptions: 11
        "-Xmx": "1g"
        "-Xms": "1g"
      readinessProbe: 12
        initialDelaySeconds: 15
        timeoutSeconds: 5
      livenessProbe:
        initialDelaySeconds: 15
        timeoutSeconds: 5
      image: my-org/my-image:latest 13
      template: 14
        pod:
          affinity:
            podAntiAffinity:
              requiredDuringSchedulingIgnoredDuringExecution:
                - labelSelector:
                    matchExpressions:
                      - key: application
                        operator: In
                        values:
                          - postgresql
                          - mongodb
                  topologyKey: "kubernetes.io/hostname"
        bridgeContainer: 15
          env:
            - name: JAEGER_SERVICE_NAME
              value: my-jaeger-service
            - name: JAEGER_AGENT_HOST
              value: jaeger-agent-name
            - name: JAEGER_AGENT_PORT
              value: "6831"
    1
    2
    Bootstrap server for connection to the target Kafka cluster. Use the name of the Kafka cluster as the <cluster_name>.
    3
    TLS encryption with key names under which TLS certificates are stored in X.509 format for the source Kafka cluster. If certificates are stored in the same secret, it can be listed multiple times.
    4
    Authentication for the Kafka Bridge cluster, using the TLS mechanism, as shown here, using OAuth bearer tokens, or a SASL-based SCRAM-SHA-256/SCRAM-SHA-512 or PLAIN mechanism. By default, the Kafka Bridge connects to Kafka brokers without authentication.
    5
    HTTP access to Kafka brokers.
    6
    CORS access specifying selected resources and access methods. Additional HTTP headers in requests describe the origins that are permitted access to the Kafka cluster.
    7
    8
    9
    Requests for reservation of supported resources, currently cpu and memory, and limits to specify the maximum resources that can be consumed.
    10
    Specified Kafka Bridge loggers and log levels added directly (inline) or indirectly (external) through a ConfigMap. A custom ConfigMap must be placed under the log4j.properties or log4j2.properties key. For the Kafka Bridge loggers, you can set the log level to INFO, ERROR, WARN, TRACE, DEBUG, FATAL or OFF.
    11
    JVM configuration options to optimize performance for the Virtual Machine (VM) running the Kafka Bridge.
    12
    Healthchecks to know when to restart a container (liveness) and when a container can accept traffic (readiness).
    13
    Optional: Container image configuration, which is recommended only in special situations.
    14
    Template customization. Here a pod is scheduled with anti-affinity, so the pod is not scheduled on nodes with the same hostname.
    15
    Environment variables are also set for distributed tracing using Jaeger.
  2. Create or update the resource:

    oc apply -f KAFKA-BRIDGE-CONFIG-FILE

2.5.2. List of Kafka Bridge cluster resources

The following resources are created by the Cluster Operator in the OpenShift cluster:

bridge-cluster-name-bridge
Deployment which is in charge to create the Kafka Bridge worker node pods.
bridge-cluster-name-bridge-service
Service which exposes the REST interface of the Kafka Bridge cluster.
bridge-cluster-name-bridge-config
ConfigMap which contains the Kafka Bridge ancillary configuration and is mounted as a volume by the Kafka broker pods.
bridge-cluster-name-bridge
Pod Disruption Budget configured for the Kafka Bridge worker nodes.

2.6. Customizing OpenShift resources

An AMQ Streams deployment creates OpenShift resources, such as Deployments, StatefulSets, Pods, and Services. These resources are managed by AMQ Streams operators. Only the operator that is responsible for managing a particular OpenShift resource can change that resource. If you try to manually change an operator-managed OpenShift resource, the operator will revert your changes back.

Changing an operator-managed OpenShift resource can be useful if you want to perform certain tasks, such as:

  • Adding custom labels or annotations that control how Pods are treated by Istio or other services
  • Managing how Loadbalancer-type Services are created by the cluster

You can make the changes using the template property in the AMQ Streams custom resources. The template property is supported in the following resources. The API reference provides more details about the customizable fields.

In the following example, the template property is used to modify the labels in a Kafka broker’s pod.

Example template customization

apiVersion: kafka.strimzi.io/v1beta2
kind: Kafka
metadata:
  name: my-cluster
  labels:
    app: my-cluster
spec:
  kafka:
    # ...
    template:
      pod:
        metadata:
          labels:
            mylabel: myvalue
    # ...

2.6.1. Customizing the image pull policy

AMQ Streams allows you to customize the image pull policy for containers in all pods deployed by the Cluster Operator. The image pull policy is configured using the environment variable STRIMZI_IMAGE_PULL_POLICY in the Cluster Operator deployment. The STRIMZI_IMAGE_PULL_POLICY environment variable can be set to three different values:

Always
Container images are pulled from the registry every time the pod is started or restarted.
IfNotPresent
Container images are pulled from the registry only when they were not pulled before.
Never
Container images are never pulled from the registry.

The image pull policy can be currently customized only for all Kafka, Kafka Connect, and Kafka MirrorMaker clusters at once. Changing the policy will result in a rolling update of all your Kafka, Kafka Connect, and Kafka MirrorMaker clusters.

Additional resources

2.6.2. Applying a termination grace period

Apply a termination grace period to give a Kafka cluster enough time to shut down cleanly.

Specify the time using the terminationGracePeriodSeconds property. Add the property to the template.pod configuration of the Kafka custom resource.

The time you add will depend on the size of your Kafka cluster. The OpenShift default for the termination grace period is 30 seconds. If you observe that your clusters are not shutting down cleanly, you can increase the termination grace period.

A termination grace period is applied every time a pod is restarted. The period begins when OpenShift sends a term (termination) signal to the processes running in the pod. The period should reflect the amount of time required to transfer the processes of the terminating pod to another pod before they are stopped. After the period ends, a kill signal stops any processes still running in the pod.

The following example adds a termination grace period of 120 seconds to the Kafka custom resource. You can also specify the configuration in the custom resources of other Kafka components.

Example termination grace period configuration

apiVersion: kafka.strimzi.io/v1beta2
kind: Kafka
metadata:
  name: my-cluster
spec:
  kafka:
    # ...
    template:
      pod:
        terminationGracePeriodSeconds: 120
        # ...
    # ...

2.7. Configuring pod scheduling

When two applications are scheduled to the same OpenShift node, both applications might use the same resources like disk I/O and impact performance. That can lead to performance degradation. Scheduling Kafka pods in a way that avoids sharing nodes with other critical workloads, using the right nodes or dedicated a set of nodes only for Kafka are the best ways how to avoid such problems.

2.7.1. Specifying affinity, tolerations, and topology spread constraints

Use affinity, tolerations and topology spread constraints to schedule the pods of kafka resources onto nodes. Affinity, tolerations and topology spread constraints are configured using the affinity, tolerations, and topologySpreadConstraint properties in following resources:

  • Kafka.spec.kafka.template.pod
  • Kafka.spec.zookeeper.template.pod
  • Kafka.spec.entityOperator.template.pod
  • KafkaConnect.spec.template.pod
  • KafkaBridge.spec.template.pod
  • KafkaMirrorMaker.spec.template.pod
  • KafkaMirrorMaker2.spec.template.pod

The format of the affinity, tolerations, and topologySpreadConstraint properties follows the OpenShift specification. The affinity configuration can include different types of affinity:

  • Pod affinity and anti-affinity
  • Node affinity
Note

On OpenShift 1.16 and 1.17, the support for topologySpreadConstraint is disabled by default. In order to use topologySpreadConstraint, you have to enable the EvenPodsSpread feature gate in Kubernetes API server and scheduler.

2.7.1.1. Use pod anti-affinity to avoid critical applications sharing nodes

Use pod anti-affinity to ensure that critical applications are never scheduled on the same disk. When running a Kafka cluster, it is recommended to use pod anti-affinity to ensure that the Kafka brokers do not share nodes with other workloads, such as databases.

2.7.1.2. Use node affinity to schedule workloads onto specific nodes

The OpenShift cluster usually consists of many different types of worker nodes. Some are optimized for CPU heavy workloads, some for memory, while other might be optimized for storage (fast local SSDs) or network. Using different nodes helps to optimize both costs and performance. To achieve the best possible performance, it is important to allow scheduling of AMQ Streams components to use the right nodes.

OpenShift uses node affinity to schedule workloads onto specific nodes. Node affinity allows you to create a scheduling constraint for the node on which the pod will be scheduled. The constraint is specified as a label selector. You can specify the label using either the built-in node label like beta.kubernetes.io/instance-type or custom labels to select the right node.

2.7.1.3. Use node affinity and tolerations for dedicated nodes

Use taints to create dedicated nodes, then schedule Kafka pods on the dedicated nodes by configuring node affinity and tolerations.

Cluster administrators can mark selected OpenShift nodes as tainted. Nodes with taints are excluded from regular scheduling and normal pods will not be scheduled to run on them. Only services which can tolerate the taint set on the node can be scheduled on it. The only other services running on such nodes will be system services such as log collectors or software defined networks.

Running Kafka and its components on dedicated nodes can have many advantages. There will be no other applications running on the same nodes which could cause disturbance or consume the resources needed for Kafka. That can lead to improved performance and stability.

2.7.2. Configuring pod anti-affinity to schedule each Kafka broker on a different worker node

Many Kafka brokers or ZooKeeper nodes can run on the same OpenShift worker node. If the worker node fails, they will all become unavailable at the same time. To improve reliability, you can use podAntiAffinity configuration to schedule each Kafka broker or ZooKeeper node on a different OpenShift worker node.

Prerequisites

  • An OpenShift cluster
  • A running Cluster Operator

Procedure

  1. Edit the affinity property in the resource specifying the cluster deployment. To make sure that no worker nodes are shared by Kafka brokers or ZooKeeper nodes, use the strimzi.io/name label. Set the topologyKey to kubernetes.io/hostname to specify that the selected pods are not scheduled on nodes with the same hostname. This will still allow the same worker node to be shared by a single Kafka broker and a single ZooKeeper node. For example:

    apiVersion: kafka.strimzi.io/v1beta2
    kind: Kafka
    spec:
      kafka:
        # ...
        template:
          pod:
            affinity:
              podAntiAffinity:
                requiredDuringSchedulingIgnoredDuringExecution:
                  - labelSelector:
                      matchExpressions:
                        - key: strimzi.io/name
                          operator: In
                          values:
                            - CLUSTER-NAME-kafka
                    topologyKey: "kubernetes.io/hostname"
        # ...
      zookeeper:
        # ...
        template:
          pod:
            affinity:
              podAntiAffinity:
                requiredDuringSchedulingIgnoredDuringExecution:
                  - labelSelector:
                      matchExpressions:
                        - key: strimzi.io/name
                          operator: In
                          values:
                            - CLUSTER-NAME-zookeeper
                    topologyKey: "kubernetes.io/hostname"
        # ...

    Where CLUSTER-NAME is the name of your Kafka custom resource.

  2. If you even want to make sure that a Kafka broker and ZooKeeper node do not share the same worker node, use the strimzi.io/cluster label. For example:

    apiVersion: kafka.strimzi.io/v1beta2
    kind: Kafka
    spec:
      kafka:
        # ...
        template:
          pod:
            affinity:
              podAntiAffinity:
                requiredDuringSchedulingIgnoredDuringExecution:
                  - labelSelector:
                      matchExpressions:
                        - key: strimzi.io/cluster
                          operator: In
                          values:
                            - CLUSTER-NAME
                    topologyKey: "kubernetes.io/hostname"
        # ...
      zookeeper:
        # ...
        template:
          pod:
            affinity:
              podAntiAffinity:
                requiredDuringSchedulingIgnoredDuringExecution:
                  - labelSelector:
                      matchExpressions:
                        - key: strimzi.io/cluster
                          operator: In
                          values:
                            - CLUSTER-NAME
                    topologyKey: "kubernetes.io/hostname"
        # ...

    Where CLUSTER-NAME is the name of your Kafka custom resource.

  3. Create or update the resource.

    oc apply -f <kafka_configuration_file>

2.7.3. Configuring pod anti-affinity in Kafka components

Pod anti-affinity configuration helps with the stability and performance of Kafka brokers. By using podAntiAffinity, OpenShift will not schedule Kafka brokers on the same nodes as other workloads. Typically, you want to avoid Kafka running on the same worker node as other network or storage intensive applications such as databases, storage or other messaging platforms.

Prerequisites

  • An OpenShift cluster
  • A running Cluster Operator

Procedure

  1. Edit the affinity property in the resource specifying the cluster deployment. Use labels to specify the pods which should not be scheduled on the same nodes. The topologyKey should be set to kubernetes.io/hostname to specify that the selected pods should not be scheduled on nodes with the same hostname. For example:

    apiVersion: kafka.strimzi.io/v1beta2
    kind: Kafka
    spec:
      kafka:
        # ...
        template:
          pod:
            affinity:
              podAntiAffinity:
                requiredDuringSchedulingIgnoredDuringExecution:
                  - labelSelector:
                      matchExpressions:
                        - key: application
                          operator: In
                          values:
                            - postgresql
                            - mongodb
                    topologyKey: "kubernetes.io/hostname"
        # ...
      zookeeper:
        # ...
  2. Create or update the resource.

    This can be done using oc apply:

    oc apply -f <kafka_configuration_file>

2.7.4. Configuring node affinity in Kafka components

Prerequisites

  • An OpenShift cluster
  • A running Cluster Operator

Procedure

  1. Label the nodes where AMQ Streams components should be scheduled.

    This can be done using oc label:

    oc label node NAME-OF-NODE node-type=fast-network

    Alternatively, some of the existing labels might be reused.

  2. Edit the affinity property in the resource specifying the cluster deployment. For example:

    apiVersion: kafka.strimzi.io/v1beta2
    kind: Kafka
    spec:
      kafka:
        # ...
        template:
          pod:
            affinity:
              nodeAffinity:
                requiredDuringSchedulingIgnoredDuringExecution:
                  nodeSelectorTerms:
                    - matchExpressions:
                      - key: node-type
                        operator: In
                        values:
                        - fast-network
        # ...
      zookeeper:
        # ...
  3. Create or update the resource.

    This can be done using oc apply:

    oc apply -f <kafka_configuration_file>

2.7.5. Setting up dedicated nodes and scheduling pods on them

Prerequisites

  • An OpenShift cluster
  • A running Cluster Operator

Procedure

  1. Select the nodes which should be used as dedicated.
  2. Make sure there are no workloads scheduled on these nodes.
  3. Set the taints on the selected nodes:

    This can be done using oc adm taint:

    oc adm taint node NAME-OF-NODE dedicated=Kafka:NoSchedule
  4. Additionally, add a label to the selected nodes as well.

    This can be done using oc label:

    oc label node NAME-OF-NODE dedicated=Kafka
  5. Edit the affinity and tolerations properties in the resource specifying the cluster deployment.

    For example:

    apiVersion: kafka.strimzi.io/v1beta2
    kind: Kafka
    spec:
      kafka:
        # ...
        template:
          pod:
            tolerations:
              - key: "dedicated"
                operator: "Equal"
                value: "Kafka"
                effect: "NoSchedule"
            affinity:
              nodeAffinity:
                requiredDuringSchedulingIgnoredDuringExecution:
                  nodeSelectorTerms:
                  - matchExpressions:
                    - key: dedicated
                      operator: In
                      values:
                      - Kafka
        # ...
      zookeeper:
        # ...
  6. Create or update the resource.

    This can be done using oc apply:

    oc apply -f <kafka_configuration_file>

2.8. Logging configuration

Configure logging levels in the custom resources of Kafka components and AMQ Streams Operators. You can specify the logging levels directly in the spec.logging property of the custom resource. Or you can define the logging properties in a ConfigMap that’s referenced in the custom resource using the configMapKeyRef property.

The advantages of using a ConfigMap are that the logging properties are maintained in one place and are accessible to more than one resource. You can also reuse the ConfigMap for more than one resource. If you are using a ConfigMap to specify loggers for AMQ Streams Operators, you can also append the logging specification to add filters.

You specify a logging type in your logging specification:

  • inline when specifying logging levels directly
  • external when referencing a ConfigMap

Example inline logging configuration

spec:
  # ...
  logging:
    type: inline
    loggers:
      kafka.root.logger.level: "INFO"

Example external logging configuration

spec:
  # ...
  logging:
    type: external
    valueFrom:
      configMapKeyRef:
        name: my-config-map
        key: my-config-map-key

Values for the name and key of the ConfigMap are mandatory. Default logging is used if the name or key is not set.

2.8.1. Logging options for Kafka components and operators

For more information on configuring logging for specific Kafka components or operators, see the following sections.

2.8.2. Creating a ConfigMap for logging

To use a ConfigMap to define logging properties, you create the ConfigMap and then reference it as part of the logging definition in the spec of a resource.

The ConfigMap must contain the appropriate logging configuration.

  • log4j.properties for Kafka components, ZooKeeper, and the Kafka Bridge
  • log4j2.properties for the Topic Operator and User Operator

The configuration must be placed under these properties.

In this procedure a ConfigMap defines a root logger for a Kafka resource.

Procedure

  1. Create the ConfigMap.

    You can create the ConfigMap as a YAML file or from a properties file.

    ConfigMap example with a root logger definition for Kafka:

    kind: ConfigMap
    apiVersion: v1
    metadata:
      name: logging-configmap
    data:
      log4j.properties:
        kafka.root.logger.level="INFO"

    If you are using a properties file, specify the file at the command line:

    oc create configmap logging-configmap --from-file=log4j.properties

    The properties file defines the logging configuration:

    # Define the logger
    kafka.root.logger.level="INFO"
    # ...
  2. Define external logging in the spec of the resource, setting the logging.valueFrom.configMapKeyRef.name to the name of the ConfigMap and logging.valueFrom.configMapKeyRef.key to the key in this ConfigMap.

    spec:
      # ...
      logging:
        type: external
        valueFrom:
          configMapKeyRef:
            name: logging-configmap
            key: log4j.properties
  3. Create or update the resource.

    oc apply -f <kafka_configuration_file>

2.8.3. Adding logging filters to Operators

If you are using a ConfigMap to configure the (log4j2) logging levels for AMQ Streams Operators, you can also define logging filters to limit what’s returned in the log.

Logging filters are useful when you have a large number of logging messages. Suppose you set the log level for the logger as DEBUG (rootLogger.level="DEBUG"). Logging filters reduce the number of logs returned for the logger at that level, so you can focus on a specific resource. When the filter is set, only log messages matching the filter are logged.

Filters use markers to specify what to include in the log. You specify a kind, namespace and name for the marker. For example, if a Kafka cluster is failing, you can isolate the logs by specifying the kind as Kafka, and use the namespace and name of the failing cluster.

This example shows a marker filter for a Kafka cluster named my-kafka-cluster.

Basic logging filter configuration

rootLogger.level="INFO"
appender.console.filter.filter1.type=MarkerFilter 1
appender.console.filter.filter1.onMatch=ACCEPT 2
appender.console.filter.filter1.onMismatch=DENY 3
appender.console.filter.filter1.marker=Kafka(my-namespace/my-kafka-cluster) 4

1
The MarkerFilter type compares a specified marker for filtering.
2
The onMatch property accepts the log if the marker matches.
3
The onMismatch property rejects the log if the marker does not match.
4
The marker used for filtering is in the format KIND(NAMESPACE/NAME-OF-RESOURCE).

You can create one or more filters. Here, the log is filtered for two Kafka clusters.

Multiple logging filter configuration

appender.console.filter.filter1.type=MarkerFilter
appender.console.filter.filter1.onMatch=ACCEPT
appender.console.filter.filter1.onMismatch=DENY
appender.console.filter.filter1.marker=Kafka(my-namespace/my-kafka-cluster-1)
appender.console.filter.filter2.type=MarkerFilter
appender.console.filter.filter2.onMatch=ACCEPT
appender.console.filter.filter2.onMismatch=DENY
appender.console.filter.filter2.marker=Kafka(my-namespace/my-kafka-cluster-2)

Adding filters to the Cluster Operator

To add filters to the Cluster Operator, update its logging ConfigMap YAML file (install/cluster-operator/050-ConfigMap-strimzi-cluster-operator.yaml).

Procedure

  1. Update the 050-ConfigMap-strimzi-cluster-operator.yaml file to add the filter properties to the ConfigMap.

    In this example, the filter properties return logs only for the my-kafka-cluster Kafka cluster:

    kind: ConfigMap
    apiVersion: v1
    metadata:
      name: strimzi-cluster-operator
    data:
      log4j2.properties:
        #...
        appender.console.filter.filter1.type=MarkerFilter
        appender.console.filter.filter1.onMatch=ACCEPT
        appender.console.filter.filter1.onMismatch=DENY
        appender.console.filter.filter1.marker=Kafka(my-namespace/my-kafka-cluster)

    Alternatively, edit the ConfigMap directly:

    oc edit configmap strimzi-cluster-operator
  2. If you updated the YAML file instead of editing the ConfigMap directly, apply the changes by deploying the ConfigMap:

    oc create -f install/cluster-operator/050-ConfigMap-strimzi-cluster-operator.yaml

Adding filters to the Topic Operator or User Operator

To add filters to the Topic Operator or User Operator, create or edit a logging ConfigMap.

In this procedure a logging ConfigMap is created with filters for the Topic Operator. The same approach is used for the User Operator.

Procedure

  1. Create the ConfigMap.

    You can create the ConfigMap as a YAML file or from a properties file.

    In this example, the filter properties return logs only for the my-topic topic:

    kind: ConfigMap
    apiVersion: v1
    metadata:
      name: logging-configmap
    data:
      log4j2.properties:
        rootLogger.level="INFO"
        appender.console.filter.filter1.type=MarkerFilter
        appender.console.filter.filter1.onMatch=ACCEPT
        appender.console.filter.filter1.onMismatch=DENY
        appender.console.filter.filter1.marker=KafkaTopic(my-namespace/my-topic)

    If you are using a properties file, specify the file at the command line:

    oc create configmap logging-configmap --from-file=log4j2.properties

    The properties file defines the logging configuration:

    # Define the logger
    rootLogger.level="INFO"
    # Set the filters
    appender.console.filter.filter1.type=MarkerFilter
    appender.console.filter.filter1.onMatch=ACCEPT
    appender.console.filter.filter1.onMismatch=DENY
    appender.console.filter.filter1.marker=KafkaTopic(my-namespace/my-topic)
    # ...
  2. Define external logging in the spec of the resource, setting the logging.valueFrom.configMapKeyRef.name to the name of the ConfigMap and logging.valueFrom.configMapKeyRef.key to the key in this ConfigMap.

    For the Topic Operator, logging is specified in the topicOperator configuration of the Kafka resource.

    spec:
      # ...
      entityOperator:
        topicOperator:
          logging:
            type: external
            valueFrom:
              configMapKeyRef:
                name: logging-configmap
                key: log4j2.properties
  3. Apply the changes by deploying the Cluster Operator:
create -f install/cluster-operator -n my-cluster-operator-namespace