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Chapter 4. Knative CLI

4.1. Installing the Knative CLI

The Knative (kn) CLI does not have its own login mechanism. To log in to the cluster, you must install the OpenShift (oc) CLI and use the oc login command. Installation options for the CLIs may vary depending on your operating system.

For more information on installing the oc CLI for your operating system and logging in with oc, see the OpenShift CLI getting started documentation.

OpenShift Serverless cannot be installed using the Knative (kn) CLI. A cluster administrator must install the OpenShift Serverless Operator and set up the Knative components, as described in the Installing the OpenShift Serverless Operator documentation.

Important

If you try to use an older version of the Knative (kn) CLI with a newer OpenShift Serverless release, the API is not found and an error occurs.

For example, if you use the 1.16.0 release of the Knative (kn) CLI, which uses version 0.22.0, with the 1.17.0 OpenShift Serverless release, which uses the 0.23.0 versions of the Knative Serving and Knative Eventing APIs, the CLI does not work because it continues to look for the outdated 0.22.0 API versions.

Ensure that you are using the latest Knative (kn) CLI version for your OpenShift Serverless release to avoid issues.

4.1.1. Installing the Knative CLI using the OpenShift Container Platform web console

Using the OpenShift Container Platform web console provides a streamlined and intuitive user interface to install the Knative (kn) CLI. After the OpenShift Serverless Operator is installed, you will see a link to download the Knative (kn) CLI for Linux (amd64, s390x, ppc64le), macOS, or Windows from the Command Line Tools page in the OpenShift Container Platform web console.

Prerequisites

  • You have logged in to the OpenShift Container Platform web console.
  • The OpenShift Serverless Operator is installed on your OpenShift Container Platform cluster.

    Important

    If libc is not available, you might see the following error when you run CLI commands:

    $ kn: No such file or directory

Procedure

  1. Download the Knative (kn) CLI from the Command Line Tools page. You can access the Command Line Tools page by clicking the question circle icon in the top right corner of the web console and selecting Command Line Tools in the list.
  2. Unpack the archive:

    $ tar -xf <file>
  3. Move the kn binary to a directory on your PATH.
  4. To check your PATH, run:

    $ echo $PATH

4.1.2. Installing the Knative CLI for Linux by using an RPM package manager

For Red Hat Enterprise Linux (RHEL), you can install the Knative (kn) CLI as an RPM by using a package manager, such as yum or dnf. This allows the Knative CLI version to be automatically managed by the system. For example, using a command like dnf upgrade upgrades all packages, including kn, if a new version is available.

Prerequisites

  • You have an active OpenShift Container Platform subscription on your Red Hat account.

Procedure

  1. Register with Red Hat Subscription Manager:

    # subscription-manager register
  2. Pull the latest subscription data:

    # subscription-manager refresh
  3. Attach the subscription to the registered system:

    # subscription-manager attach --pool=<pool_id> 1
    1
    Pool ID for an active OpenShift Container Platform subscription
  4. Enable the repositories required by the Knative (kn) CLI:

    • Linux (x86_64, amd64)

      # subscription-manager repos --enable="openshift-serverless-1-for-rhel-8-x86_64-rpms"
    • Linux on IBM Z and LinuxONE (s390x)

      # subscription-manager repos --enable="openshift-serverless-1-for-rhel-8-s390x-rpms"
    • Linux on IBM Power (ppc64le)

      # subscription-manager repos --enable="openshift-serverless-1-for-rhel-8-ppc64le-rpms"
  5. Install the Knative (kn) CLI as an RPM by using a package manager:

    Example yum command

    # yum install openshift-serverless-clients

4.1.3. Installing the Knative CLI for Linux

If you are using a Linux distribution that does not have RPM or another package manager installed, you can install the Knative (kn) CLI as a binary file. To do this, you must download and unpack a tar.gz archive and add the binary to a directory on your PATH.

Prerequisites

  • If you are not using RHEL or Fedora, ensure that libc is installed in a directory on your library path.

    Important

    If libc is not available, you might see the following error when you run CLI commands:

    $ kn: No such file or directory

Procedure

  1. Download the relevant Knative (kn) CLI tar.gz archive:

  2. Unpack the archive:

    $ tar -xf <filename>
  3. Move the kn binary to a directory on your PATH.
  4. To check your PATH, run:

    $ echo $PATH

4.1.4. Installing the Knative CLI for macOS

If you are using macOS, you can install the Knative (kn) CLI as a binary file. To do this, you must download and unpack a tar.gz archive and add the binary to a directory on your PATH.

Procedure

  1. Download the Knative (kn) CLI tar.gz archive.
  2. Unpack and extract the archive.
  3. Move the kn binary to a directory on your PATH.
  4. To check your PATH, open a terminal window and run:

    $ echo $PATH

4.1.5. Installing the Knative CLI for Windows

If you are using Windows, you can install the Knative (kn) CLI as a binary file. To do this, you must download and unpack a ZIP archive and add the binary to a directory on your PATH.

Procedure

  1. Download the Knative (kn) CLI ZIP archive.
  2. Extract the archive with a ZIP program.
  3. Move the kn binary to a directory on your PATH.
  4. To check your PATH, open the command prompt and run the command:

    C:\> path

4.2. Configuring the Knative CLI

You can customize your Knative (kn) CLI setup by creating a config.yaml configuration file. You can provide this configuration by using the --config flag, otherwise the configuration is picked up from a default location. The default configuration location conforms to the XDG Base Directory Specification, and is different for UNIX systems and Windows systems.

For UNIX systems:

  • If the XDG_CONFIG_HOME environment variable is set, the default configuration location that the Knative (kn) CLI looks for is $XDG_CONFIG_HOME/kn.
  • If the XDG_CONFIG_HOME environment variable is not set, the Knative (kn) CLI looks for the configuration in the home directory of the user at $HOME/.config/kn/config.yaml.

For Windows systems, the default Knative (kn) CLI configuration location is %APPDATA%\kn.

Example configuration file

plugins:
  path-lookup: true 1
  directory: ~/.config/kn/plugins 2
eventing:
  sink-mappings: 3
  - prefix: svc 4
    group: core 5
    version: v1 6
    resource: services 7

1
Specifies whether the Knative (kn) CLI should look for plug-ins in the PATH environment variable. This is a boolean configuration option. The default value is false.
2
Specifies the directory where the Knative (kn) CLI looks for plug-ins. The default path depends on the operating system, as described previously. This can be any directory that is visible to the user.
3
The sink-mappings spec defines the Kubernetes addressable resource that is used when you use the --sink flag with a Knative (kn) CLI command.
4
The prefix you want to use to describe your sink. svc for a service, channel, and broker are predefined prefixes for the Knative (kn) CLI.
5
The API group of the Kubernetes resource.
6
The version of the Kubernetes resource.
7
The plural name of the Kubernetes resource type. For example, services or brokers.

4.3. Knative CLI plug-ins

The Knative (kn) CLI supports the use of plug-ins, which enable you to extend the functionality of your kn installation by adding custom commands and other shared commands that are not part of the core distribution. Knative (kn) CLI plug-ins are used in the same way as the main kn functionality.

Currently, Red Hat supports the kn-source-kafka plug-in and the kn-event plug-in.

Important

The kn-event plug-in is a Technology Preview feature only. Technology Preview features are not supported with Red Hat production service level agreements (SLAs) and might not be functionally complete. Red Hat does not recommend using them in production. These features provide early access to upcoming product features, enabling customers to test functionality and provide feedback during the development process.

For more information about the support scope of Red Hat Technology Preview features, see https://access.redhat.com/support/offerings/techpreview/.

4.3.1. Building events by using the kn-event plug-in

You can use the builder-like interface of the kn event build command to build an event. You can then send that event at a later time or use it in another context.

Prerequisites

  • You have installed the Knative (kn) CLI.

Procedure

  • Build an event:

    $ kn event build --field <field-name>=<value> --type <type-name> --id <id> --output <format>

    where:

    • The --field flag adds data to the event as a field-value pair. You can use it multiple times.
    • The --type flag enables you to specify a string that designates the type of the event.
    • The --id flag specifies the ID of the event.
    • You can use the json or yaml arguments with the --output flag to change the output format of the event.

      All of these flags are optional.

      Building a simple event

      $ kn event build -o yaml

      Resultant event in the YAML format

      data: {}
      datacontenttype: application/json
      id: 81a402a2-9c29-4c27-b8ed-246a253c9e58
      source: kn-event/v0.4.0
      specversion: "1.0"
      time: "2021-10-15T10:42:57.713226203Z"
      type: dev.knative.cli.plugin.event.generic

      Building a sample transaction event

      $ kn event build \
          --field operation.type=local-wire-transfer \
          --field operation.amount=2345.40 \
          --field operation.from=87656231 \
          --field operation.to=2344121 \
          --field automated=true \
          --field signature='FGzCPLvYWdEgsdpb3qXkaVp7Da0=' \
          --type org.example.bank.bar \
          --id $(head -c 10 < /dev/urandom | base64 -w 0) \
          --output json

      Resultant event in the JSON format

      {
        "specversion": "1.0",
        "id": "RjtL8UH66X+UJg==",
        "source": "kn-event/v0.4.0",
        "type": "org.example.bank.bar",
        "datacontenttype": "application/json",
        "time": "2021-10-15T10:43:23.113187943Z",
        "data": {
          "automated": true,
          "operation": {
            "amount": "2345.40",
            "from": 87656231,
            "to": 2344121,
            "type": "local-wire-transfer"
          },
          "signature": "FGzCPLvYWdEgsdpb3qXkaVp7Da0="
        }
      }

4.3.2. Sending events by using the kn-event plug-in

You can use the kn event send command to send an event. The events can be sent either to publicly available addresses or to addressable resources inside a cluster, such as Kubernetes services, as well as Knative services, brokers, and channels. The command uses the same builder-like interface as the kn event build command.

Prerequisites

  • You have installed the Knative (kn) CLI.

Procedure

  • Send an event:

    $ kn event send --field <field-name>=<value> --type <type-name> --id <id> --to-url <url> --to <cluster-resource> --namespace <namespace>

    where:

    • The --field flag adds data to the event as a field-value pair. You can use it multiple times.
    • The --type flag enables you to specify a string that designates the type of the event.
    • The --id flag specifies the ID of the event.
    • If you are sending the event to a publicly accessible destination, specify the URL using the --to-url flag.
    • If you are sending the event to an in-cluster Kubernetes resource, specify the destination using the --to flag.

      • Specify the Kubernetes resource using the <Kind>:<ApiVersion>:<name> format.
    • The --namespace flag specifies the namespace. If omitted, the namespace is taken from the current context.

      All of these flags are optional, except for the destination specification, for which you need to use either --to-url or --to.

      The following example shows sending an event to a URL:

      Example command

      $ kn event send \
          --field player.id=6354aa60-ddb1-452e-8c13-24893667de20 \
          --field player.game=2345 \
          --field points=456 \
          --type org.example.gaming.foo \
          --to-url http://ce-api.foo.example.com/

      The following example shows sending an event to an in-cluster resource:

      Example command

      $ kn event send \
          --type org.example.kn.ping \
          --id $(uuidgen) \
          --field event.type=test \
          --field event.data=98765 \
          --to Service:serving.knative.dev/v1:event-display

4.4. Knative Serving CLI commands

You can use the following kn CLI commands to complete Knative Serving tasks on the cluster.

4.4.1. kn service commands

You can use the following commands to create and manage Knative services.

4.4.1.1. Creating serverless applications by using the Knative CLI

Using the kn CLI to create serverless applications provides a more streamlined and intuitive user interface over modifying YAML files directly. You can use the kn service create command to create a basic serverless application using the kn CLI.

Prerequisites

  • OpenShift Serverless Operator and Knative Serving are installed on your cluster.
  • You have installed the kn CLI.
  • You have created a project or have access to a project with the appropriate roles and permissions to create applications and other workloads in OpenShift Container Platform.

Procedure

  • Create a Knative service:

    $ kn service create <service-name> --image <image> --tag <tag-value>

    Where:

    • --image is the URI of the image for the application.
    • --tag is an optional flag that can be used to add a tag to the initial revision that is created with the service.

      Example command

      $ kn service create event-display \
          --image quay.io/openshift-knative/knative-eventing-sources-event-display:latest

      Example output

      Creating service 'event-display' in namespace 'default':
      
        0.271s The Route is still working to reflect the latest desired specification.
        0.580s Configuration "event-display" is waiting for a Revision to become ready.
        3.857s ...
        3.861s Ingress has not yet been reconciled.
        4.270s Ready to serve.
      
      Service 'event-display' created with latest revision 'event-display-bxshg-1' and URL:
      http://event-display-default.apps-crc.testing

4.4.1.2. Updating serverless applications by using the Knative CLI

You can use the kn service update command for interactive sessions on the command line as you build up a service incrementally. In contrast to the kn service apply command, when using the kn service update command you only have to specify the changes that you want to update, rather than the full configuration for the Knative service.

Example commands

  • Update a service by adding a new environment variable:

    $ kn service update <service_name> --env <key>=<value>
  • Update a service by adding a new port:

    $ kn service update <service_name> --port 80
  • Update a service by adding new request and limit parameters:

    $ kn service update <service_name> --request cpu=500m --limit memory=1024Mi --limit cpu=1000m
  • Assign the latest tag to a revision:

    $ kn service update <service_name> --tag <revision_name>=latest
  • Update a tag from testing to staging for the latest READY revision of a service:

    $ kn service update <service_name> --untag testing --tag @latest=staging
  • Add the test tag to a revision that receives 10% of traffic, and send the rest of the traffic to the latest READY revision of a service:

    $ kn service update <service_name> --tag <revision_name>=test --traffic test=10,@latest=90

4.4.1.3. Applying service declarations

You can declaratively configure a Knative service by using the kn service apply command. If the service does not exist it is created, otherwise the existing service is updated with the options that have been changed.

The kn service apply command is especially useful for shell scripts or in a continuous integration pipeline, where users typically want to fully specify the state of the service in a single command to declare the target state.

When using kn service apply you must provide the full configuration for the Knative service. This is different from the kn service update command, which only requires you to specify in the command the options that you want to update.

Example commands

  • Create a service:

    $ kn service apply <service_name> --image <image>
  • Add an environment variable to a service:

    $ kn service apply <service_name> --image <image> --env <key>=<value>
  • Read the service declaration from a JSON or YAML file:

    $ kn service apply <service_name> -f <filename>

4.4.1.4. Describing serverless applications by using the Knative CLI

You can describe a Knative service by using the kn service describe command.

Example commands

  • Describe a service:

    $ kn service describe --verbose <service_name>

    The --verbose flag is optional but can be included to provide a more detailed description. The difference between a regular and verbose output is shown in the following examples:

    Example output without --verbose flag

    Name:       hello
    Namespace:  default
    Age:        2m
    URL:        http://hello-default.apps.ocp.example.com
    
    Revisions:
      100%  @latest (hello-00001) [1] (2m)
            Image:  docker.io/openshift/hello-openshift (pinned to aaea76)
    
    Conditions:
      OK TYPE                   AGE REASON
      ++ Ready                   1m
      ++ ConfigurationsReady     1m
      ++ RoutesReady             1m

    Example output with --verbose flag

    Name:         hello
    Namespace:    default
    Annotations:  serving.knative.dev/creator=system:admin
                  serving.knative.dev/lastModifier=system:admin
    Age:          3m
    URL:          http://hello-default.apps.ocp.example.com
    Cluster:      http://hello.default.svc.cluster.local
    
    Revisions:
      100%  @latest (hello-00001) [1] (3m)
            Image:  docker.io/openshift/hello-openshift (pinned to aaea76)
            Env:    RESPONSE=Hello Serverless!
    
    Conditions:
      OK TYPE                   AGE REASON
      ++ Ready                   3m
      ++ ConfigurationsReady     3m
      ++ RoutesReady             3m

  • Describe a service in YAML format:

    $ kn service describe <service_name> -o yaml
  • Describe a service in JSON format:

    $ kn service describe <service_name> -o json
  • Print the service URL only:

    $ kn service describe <service_name> -o url

4.4.2. About the Knative CLI offline mode

When you execute kn service commands, the changes immediately propagate to the cluster. However, as an alternative, you can execute kn service commands in offline mode. When you create a service in offline mode, no changes happen on the cluster, and instead the service descriptor file is created on your local machine.

Important

The offline mode of the Knative CLI is a Technology Preview feature only. Technology Preview features are not supported with Red Hat production service level agreements (SLAs) and might not be functionally complete. Red Hat does not recommend using them in production. These features provide early access to upcoming product features, enabling customers to test functionality and provide feedback during the development process.

For more information about the support scope of Red Hat Technology Preview features, see https://access.redhat.com/support/offerings/techpreview/.

After the descriptor file is created, you can manually modify it and track it in a version control system. You can also propagate changes to the cluster by using the kn service create -f, kn service apply -f, or oc apply -f commands on the descriptor files.

The offline mode has several uses:

  • You can manually modify the descriptor file before using it to make changes on the cluster.
  • You can locally track the descriptor file of a service in a version control system. This enables you to reuse the descriptor file in places other than the target cluster, for example in continuous integration (CI) pipelines, development environments, or demos.
  • You can examine the created descriptor files to learn about Knative services. In particular, you can see how the resulting service is influenced by the different arguments passed to the kn command.

The offline mode has its advantages: it is fast, and does not require a connection to the cluster. However, offline mode lacks server-side validation. Consequently, you cannot, for example, verify that the service name is unique or that the specified image can be pulled.

4.4.2.1. Creating a service using offline mode

You can execute kn service commands in offline mode, so that no changes happen on the cluster, and instead the service descriptor file is created on your local machine. After the descriptor file is created, you can modify the file before propagating changes to the cluster.

Important

The offline mode of the Knative CLI is a Technology Preview feature only. Technology Preview features are not supported with Red Hat production service level agreements (SLAs) and might not be functionally complete. Red Hat does not recommend using them in production. These features provide early access to upcoming product features, enabling customers to test functionality and provide feedback during the development process.

For more information about the support scope of Red Hat Technology Preview features, see https://access.redhat.com/support/offerings/techpreview/.

Prerequisites

  • OpenShift Serverless Operator and Knative Serving are installed on your cluster.
  • You have installed the Knative (kn) CLI.

Procedure

  1. In offline mode, create a local Knative service descriptor file:

    $ kn service create event-display \
        --image quay.io/openshift-knative/knative-eventing-sources-event-display:latest \
        --target ./ \
        --namespace test

    Example output

    Service 'event-display' created in namespace 'test'.

    • The --target ./ flag enables offline mode and specifies ./ as the directory for storing the new directory tree.

      If you do not specify an existing directory, but use a filename, such as --target my-service.yaml, then no directory tree is created. Instead, only the service descriptor file my-service.yaml is created in the current directory.

      The filename can have the .yaml, .yml, or .json extension. Choosing .json creates the service descriptor file in the JSON format.

    • The --namespace test option places the new service in the test namespace.

      If you do not use --namespace, and you are logged in to an OpenShift Container Platform cluster, the descriptor file is created in the current namespace. Otherwise, the descriptor file is created in the default namespace.

  2. Examine the created directory structure:

    $ tree ./

    Example output

    ./
    └── test
        └── ksvc
            └── event-display.yaml
    
    2 directories, 1 file

    • The current ./ directory specified with --target contains the new test/ directory that is named after the specified namespace.
    • The test/ directory contains the ksvc directory, named after the resource type.
    • The ksvc directory contains the descriptor file event-display.yaml, named according to the specified service name.
  3. Examine the generated service descriptor file:

    $ cat test/ksvc/event-display.yaml

    Example output

    apiVersion: serving.knative.dev/v1
    kind: Service
    metadata:
      creationTimestamp: null
      name: event-display
      namespace: test
    spec:
      template:
        metadata:
          annotations:
            client.knative.dev/user-image: quay.io/openshift-knative/knative-eventing-sources-event-display:latest
          creationTimestamp: null
        spec:
          containers:
          - image: quay.io/openshift-knative/knative-eventing-sources-event-display:latest
            name: ""
            resources: {}
    status: {}

  4. List information about the new service:

    $ kn service describe event-display --target ./ --namespace test

    Example output

    Name:       event-display
    Namespace:  test
    Age:
    URL:
    
    Revisions:
    
    Conditions:
      OK TYPE    AGE REASON

    • The --target ./ option specifies the root directory for the directory structure containing namespace subdirectories.

      Alternatively, you can directly specify a YAML or JSON filename with the --target option. The accepted file extensions are .yaml, .yml, and .json.

    • The --namespace option specifies the namespace, which communicates to kn the subdirectory that contains the necessary service descriptor file.

      If you do not use --namespace, and you are logged in to an OpenShift Container Platform cluster, kn searches for the service in the subdirectory that is named after the current namespace. Otherwise, kn searches in the default/ subdirectory.

  5. Use the service descriptor file to create the service on the cluster:

    $ kn service create -f test/ksvc/event-display.yaml

    Example output

    Creating service 'event-display' in namespace 'test':
    
      0.058s The Route is still working to reflect the latest desired specification.
      0.098s ...
      0.168s Configuration "event-display" is waiting for a Revision to become ready.
     23.377s ...
     23.419s Ingress has not yet been reconciled.
     23.534s Waiting for load balancer to be ready
     23.723s Ready to serve.
    
    Service 'event-display' created to latest revision 'event-display-00001' is available at URL:
    http://event-display-test.apps.example.com

4.4.3. kn container commands

You can use the following commands to create and manage multiple containers in a Knative service spec.

4.4.3.1. Knative client multi-container support

You can use the kn container add command to print YAML container spec to standard output. This command is useful for multi-container use cases because it can be used along with other standard kn flags to create definitions.

The kn container add command accepts all container-related flags that are supported for use with the kn service create command. The kn container add command can also be chained by using UNIX pipes (|) to create multiple container definitions at once.

Example commands
  • Add a container from an image and print it to standard output:

    $ kn container add <container_name> --image <image_uri>

    Example command

    $ kn container add sidecar --image docker.io/example/sidecar

    Example output

    containers:
    - image: docker.io/example/sidecar
      name: sidecar
      resources: {}

  • Chain two kn container add commands together, and then pass them to a kn service create command to create a Knative service with two containers:

    $ kn container add <first_container_name> --image <image_uri> | \
    kn container add <second_container_name> --image <image_uri> | \
    kn service create <service_name> --image <image_uri> --extra-containers -

    --extra-containers - specifies a special case where kn reads the pipe input instead of a YAML file.

    Example command

    $ kn container add sidecar --image docker.io/example/sidecar:first | \
    kn container add second --image docker.io/example/sidecar:second | \
    kn service create my-service --image docker.io/example/my-app:latest --extra-containers -

    The --extra-containers flag can also accept a path to a YAML file:

    $ kn service create <service_name> --image <image_uri> --extra-containers <filename>

    Example command

    $ kn service create my-service --image docker.io/example/my-app:latest --extra-containers my-extra-containers.yaml

4.4.4. kn domain commands

You can use the following commands to create and manage domain mappings.

4.4.4.1. Creating a custom domain mapping by using the Knative CLI

You can use the kn CLI to create a DomainMapping custom resource (CR) that maps to an Addressable target CR, such as a Knative service or a Knative route.

The --ref flag specifies an Addressable target CR for domain mapping.

If a prefix is not provided when using the --ref flag, it is assumed that the target is a Knative service in the current namespace. The examples in the following procedure show the prefixes for mapping to a Knative service or a Knative route.

Prerequisites

  • The OpenShift Serverless Operator and Knative Serving are installed on your cluster.
  • You have created a Knative service or route, and control a custom domain that you want to map to that CR.

    Note

    Your custom domain must point to the DNS of the OpenShift Container Platform cluster.

  • You have installed the kn CLI tool.
  • You have created a project or have access to a project with the appropriate roles and permissions to create applications and other workloads in OpenShift Container Platform.

Procedure

  • Map a domain to a CR in the current namespace:

    $ kn domain create <domain_mapping_name> --ref <target_name>

    Example command

    $ kn domain create example.com --ref example-service

  • Map a domain to a Knative service in a specified namespace:

    $ kn domain create <domain_mapping_name> --ref <ksvc:service_name:service_namespace>

    Example command

    $ kn domain create example.com --ref ksvc:example-service:example-namespace

  • Map a domain to a Knative route:

    $ kn domain create <domain_mapping_name> --ref <kroute:route_name>

    Example command

    $ kn domain create example.com --ref kroute:example-route

4.4.4.2. Managing custom domain mappings by using the Knative CLI

After you have created a DomainMapping custom resource (CR), you can list existing CRs, view information about an existing CR, update CRs, or delete CRs by using the kn CLI.

Prerequisites

  • The OpenShift Serverless Operator and Knative Serving are installed on your cluster.
  • You have created at least one DomainMapping CR.
  • You have installed the kn CLI tool.
  • You have created a project or have access to a project with the appropriate roles and permissions to create applications and other workloads in OpenShift Container Platform.

Procedure

  • List existing DomainMapping CRs:

    $ kn domain list -n <domain_mapping_namespace>
  • View details of an existing DomainMapping CR:

    $ kn domain describe <domain_mapping_name>
  • Update a DomainMapping CR to point to a new target:

    $ kn domain update --ref <target>
  • Delete a DomainMapping CR:

    $ kn domain delete <domain_mapping_name>

4.5. Knative Eventing CLI commands

You can use the following Knative (kn) CLI commands to complete Knative Eventing tasks on the cluster.

4.5.1. kn source commands

You can use the following commands to list, create, and manage Knative event sources.

4.5.1.1. Listing available event source types by using the Knative CLI

Using the kn CLI provides a streamlined and intuitive user interface to view available event source types on your cluster. You can list event source types that can be created and used on your cluster by using the kn source list-types CLI command.

Prerequisites

  • The OpenShift Serverless Operator and Knative Eventing are installed on the cluster.
  • You have installed the Knative (kn) CLI.

Procedure

  1. List the available event source types in the terminal:

    $ kn source list-types

    Example output

    TYPE              NAME                                            DESCRIPTION
    ApiServerSource   apiserversources.sources.knative.dev            Watch and send Kubernetes API events to a sink
    PingSource        pingsources.sources.knative.dev                 Periodically send ping events to a sink
    SinkBinding       sinkbindings.sources.knative.dev                Binding for connecting a PodSpecable to a sink

  2. Optional: You can also list the available event source types in YAML format:

    $ kn source list-types -o yaml

4.5.1.2. Knative CLI sink flag

When you create an event source by using the Knative (kn) CLI, you can specify a sink where events are sent to from that resource by using the --sink flag. The sink can be any addressable or callable resource that can receive incoming events from other resources.

The following example creates a sink binding that uses a service, http://event-display.svc.cluster.local, as the sink:

Example command using the sink flag

$ kn source binding create bind-heartbeat \
  --namespace sinkbinding-example \
  --subject "Job:batch/v1:app=heartbeat-cron" \
  --sink http://event-display.svc.cluster.local \ 1
  --ce-override "sink=bound"

1
svc in http://event-display.svc.cluster.local determines that the sink is a Knative service. Other default sink prefixes include channel, and broker.

4.5.1.3. Creating and managing container sources by using the Knative CLI

You can use the kn source container commands to create and manage container sources by using the kn CLI. Using the kn CLI to create event sources provides a more streamlined and intuitive user interface than modifying YAML files directly.

Create a container source

$ kn source container create <container_source_name> --image <image_uri> --sink <sink>

Delete a container source

$ kn source container delete <container_source_name>

Describe a container source

$ kn source container describe <container_source_name>

List existing container sources

$ kn source container list

List existing container sources in YAML format

$ kn source container list -o yaml

Update a container source

This command updates the image URI for an existing container source:

$ kn source container update <container_source_name> --image <image_uri>

4.5.1.4. Creating an API server source by using the Knative CLI

You can use the kn source apiserver create command to create an API server source by using the kn CLI. Using the kn CLI to create an API server source provides a more streamlined and intuitive user interface than modifying YAML files directly.

Prerequisites

  • The OpenShift Serverless Operator and Knative Eventing are installed on the cluster.
  • You have created a project or have access to a project with the appropriate roles and permissions to create applications and other workloads in OpenShift Container Platform.
  • You have installed the OpenShift (oc) CLI.
  • You have installed the Knative (kn) CLI.
Procedure

If you want to re-use an existing service account, you can modify your existing ServiceAccount resource to include the required permissions instead of creating a new resource.

  1. Create a service account, role, and role binding for the event source as a YAML file:

    apiVersion: v1
    kind: ServiceAccount
    metadata:
      name: events-sa
      namespace: default 1
    
    ---
    apiVersion: rbac.authorization.k8s.io/v1
    kind: Role
    metadata:
      name: event-watcher
      namespace: default 2
    rules:
      - apiGroups:
          - ""
        resources:
          - events
        verbs:
          - get
          - list
          - watch
    
    ---
    apiVersion: rbac.authorization.k8s.io/v1
    kind: RoleBinding
    metadata:
      name: k8s-ra-event-watcher
      namespace: default 3
    roleRef:
      apiGroup: rbac.authorization.k8s.io
      kind: Role
      name: event-watcher
    subjects:
      - kind: ServiceAccount
        name: events-sa
        namespace: default 4
    1 2 3 4
    Change this namespace to the namespace that you have selected for installing the event source.
  2. Apply the YAML file:

    $ oc apply -f <filename>
  3. Create an API server source that has an event sink. In the following example, the sink is a broker:

    $ kn source apiserver create <event_source_name> --sink broker:<broker_name> --resource "event:v1" --service-account <service_account_name> --mode Resource
  4. To check that the API server source is set up correctly, create a Knative service that dumps incoming messages to its log:

    $ kn service create <service_name> --image quay.io/openshift-knative/knative-eventing-sources-event-display:latest
  5. If you used a broker as an event sink, create a trigger to filter events from the default broker to the service:

    $ kn trigger create <trigger_name> --sink ksvc:<service_name>
  6. Create events by launching a pod in the default namespace:

    $ oc create deployment hello-node --image quay.io/openshift-knative/knative-eventing-sources-event-display:latest
  7. Check that the controller is mapped correctly by inspecting the output generated by the following command:

    $ kn source apiserver describe <source_name>

    Example output

    Name:                mysource
    Namespace:           default
    Annotations:         sources.knative.dev/creator=developer, sources.knative.dev/lastModifier=developer
    Age:                 3m
    ServiceAccountName:  events-sa
    Mode:                Resource
    Sink:
      Name:       default
      Namespace:  default
      Kind:       Broker (eventing.knative.dev/v1)
    Resources:
      Kind:        event (v1)
      Controller:  false
    Conditions:
      OK TYPE                     AGE REASON
      ++ Ready                     3m
      ++ Deployed                  3m
      ++ SinkProvided              3m
      ++ SufficientPermissions     3m
      ++ EventTypesProvided        3m

Verification

You can verify that the Kubernetes events were sent to Knative by looking at the message dumper function logs.

  1. Get the pods:

    $ oc get pods
  2. View the message dumper function logs for the pods:

    $ oc logs $(oc get pod -o name | grep event-display) -c user-container

    Example output

    ☁️  cloudevents.Event
    Validation: valid
    Context Attributes,
      specversion: 1.0
      type: dev.knative.apiserver.resource.update
      datacontenttype: application/json
      ...
    Data,
      {
        "apiVersion": "v1",
        "involvedObject": {
          "apiVersion": "v1",
          "fieldPath": "spec.containers{hello-node}",
          "kind": "Pod",
          "name": "hello-node",
          "namespace": "default",
           .....
        },
        "kind": "Event",
        "message": "Started container",
        "metadata": {
          "name": "hello-node.159d7608e3a3572c",
          "namespace": "default",
          ....
        },
        "reason": "Started",
        ...
      }

Deleting the API server source

  1. Delete the trigger:

    $ kn trigger delete <trigger_name>
  2. Delete the event source:

    $ kn source apiserver delete <source_name>
  3. Delete the service account, cluster role, and cluster binding:

    $ oc delete -f authentication.yaml

4.5.1.5. Creating a ping source by using the Knative CLI

You can use the kn source ping create command to create a ping source by using the kn CLI. Using the kn CLI to create event sources provides a more streamlined and intuitive user interface than modifying YAML files directly.

Prerequisites

  • The OpenShift Serverless Operator, Knative Serving and Knative Eventing are installed on the cluster.
  • You have installed the Knative (kn) CLI.
  • You have created a project or have access to a project with the appropriate roles and permissions to create applications and other workloads in OpenShift Container Platform.
  • Optional: If you want to use the verification steps for this procedure, install the OpenShift (oc) CLI.

Procedure

  1. To verify that the ping source is working, create a simple Knative service that dumps incoming messages to the service logs:

    $ kn service create event-display \
        --image quay.io/openshift-knative/knative-eventing-sources-event-display:latest
  2. For each set of ping events that you want to request, create a ping source in the same namespace as the event consumer:

    $ kn source ping create test-ping-source \
        --schedule "*/2 * * * *" \
        --data '{"message": "Hello world!"}' \
        --sink ksvc:event-display
  3. Check that the controller is mapped correctly by entering the following command and inspecting the output:

    $ kn source ping describe test-ping-source

    Example output

    Name:         test-ping-source
    Namespace:    default
    Annotations:  sources.knative.dev/creator=developer, sources.knative.dev/lastModifier=developer
    Age:          15s
    Schedule:     */2 * * * *
    Data:         {"message": "Hello world!"}
    
    Sink:
      Name:       event-display
      Namespace:  default
      Resource:   Service (serving.knative.dev/v1)
    
    Conditions:
      OK TYPE                 AGE REASON
      ++ Ready                 8s
      ++ Deployed              8s
      ++ SinkProvided         15s
      ++ ValidSchedule        15s
      ++ EventTypeProvided    15s
      ++ ResourcesCorrect     15s

Verification

You can verify that the Kubernetes events were sent to the Knative event sink by looking at the logs of the sink pod.

By default, Knative services terminate their pods if no traffic is received within a 60 second period. The example shown in this guide creates a ping source that sends a message every 2 minutes, so each message should be observed in a newly created pod.

  1. Watch for new pods created:

    $ watch oc get pods
  2. Cancel watching the pods using Ctrl+C, then look at the logs of the created pod:

    $ oc logs $(oc get pod -o name | grep event-display) -c user-container

    Example output

    ☁️  cloudevents.Event
    Validation: valid
    Context Attributes,
      specversion: 1.0
      type: dev.knative.sources.ping
      source: /apis/v1/namespaces/default/pingsources/test-ping-source
      id: 99e4f4f6-08ff-4bff-acf1-47f61ded68c9
      time: 2020-04-07T16:16:00.000601161Z
      datacontenttype: application/json
    Data,
      {
        "message": "Hello world!"
      }

Deleting the ping source

  • Delete the ping source:

    $ kn delete pingsources.sources.knative.dev <ping_source_name>

4.5.1.6. Creating a Kafka event source by using the Knative CLI

You can use the kn source kafka create command to create a Kafka source by using the kn CLI. Using the kn CLI to create event sources provides a more streamlined and intuitive user interface than modifying YAML files directly.

Prerequisites

  • The OpenShift Serverless Operator, Knative Eventing, Knative Serving, and the KnativeKafka custom resource (CR) are installed on your cluster.
  • You have created a project or have access to a project with the appropriate roles and permissions to create applications and other workloads in OpenShift Container Platform.
  • You have access to a Red Hat AMQ Streams (Kafka) cluster that produces the Kafka messages you want to import.
  • You have installed the Knative (kn) CLI.
  • Optional: You have installed the OpenShift (oc) CLI if you want to use the verification steps in this procedure.

Procedure

  1. To verify that the Kafka event source is working, create a Knative service that dumps incoming events into the service logs:

    $ kn service create event-display \
        --image quay.io/openshift-knative/knative-eventing-sources-event-display
  2. Create a KafkaSource CR:

    $ kn source kafka create <kafka_source_name> \
        --servers <cluster_kafka_bootstrap>.kafka.svc:9092 \
        --topics <topic_name> --consumergroup my-consumer-group \
        --sink event-display
    Note

    Replace the placeholder values in this command with values for your source name, bootstrap servers, and topics.

    The --servers, --topics, and --consumergroup options specify the connection parameters to the Kafka cluster. The --consumergroup option is optional.

  3. Optional: View details about the KafkaSource CR you created:

    $ kn source kafka describe <kafka_source_name>

    Example output

    Name:              example-kafka-source
    Namespace:         kafka
    Age:               1h
    BootstrapServers:  example-cluster-kafka-bootstrap.kafka.svc:9092
    Topics:            example-topic
    ConsumerGroup:     example-consumer-group
    
    Sink:
      Name:       event-display
      Namespace:  default
      Resource:   Service (serving.knative.dev/v1)
    
    Conditions:
      OK TYPE            AGE REASON
      ++ Ready            1h
      ++ Deployed         1h
      ++ SinkProvided     1h

Verification steps

  1. Trigger the Kafka instance to send a message to the topic:

    $ oc -n kafka run kafka-producer \
        -ti --image=quay.io/strimzi/kafka:latest-kafka-2.7.0 --rm=true \
        --restart=Never -- bin/kafka-console-producer.sh \
        --broker-list <cluster_kafka_bootstrap>:9092 --topic my-topic

    Enter the message in the prompt. This command assumes that:

    • The Kafka cluster is installed in the kafka namespace.
    • The KafkaSource object has been configured to use the my-topic topic.
  2. Verify that the message arrived by viewing the logs:

    $ oc logs $(oc get pod -o name | grep event-display) -c user-container

    Example output

    ☁️  cloudevents.Event
    Validation: valid
    Context Attributes,
      specversion: 1.0
      type: dev.knative.kafka.event
      source: /apis/v1/namespaces/default/kafkasources/example-kafka-source#example-topic
      subject: partition:46#0
      id: partition:46/offset:0
      time: 2021-03-10T11:21:49.4Z
    Extensions,
      traceparent: 00-161ff3815727d8755848ec01c866d1cd-7ff3916c44334678-00
    Data,
      Hello!

4.6. Functions commands

4.6.1. Creating functions

You can create a basic serverless function using the kn CLI.

You can specify the path, runtime, template, and repository with the template as flags on the command line, or use the -c flag to start the interactive experience in the terminal.

Prerequisites

  • The OpenShift Serverless Operator and Knative Serving are installed on the cluster.
  • You have installed the kn CLI.

Procedure

  • Create a function project:

    $ kn func create -r <repository> -l <runtime> -t <template> <path>
    • Supported runtimes include node, go, python, quarkus, and typescript.
    • Supported templates include http and events.

      Example command

      $ kn func create -l typescript -t events examplefunc

      Example output

      Project path:  /home/user/demo/examplefunc
      Function name: examplefunc
      Runtime:       typescript
      Template:      events
      Writing events to /home/user/demo/examplefunc

    • Alternatively, you can specify a repository that contains a custom template.

      Example command

      $ kn func create -r https://github.com/boson-project/templates/ -l node -t hello-world examplefunc

      Example output

      Project path:  /home/user/demo/examplefunc
      Function name: examplefunc
      Runtime:       node
      Template:      hello-world
      Writing events to /home/user/demo/examplefunc

4.6.2. Building functions

Before you can run a function, you must build the function project by using the kn func build command. This command creates an OCI container image that can be run locally on your computer or on an OpenShift Container Platform cluster. The build command uses the function project name and the image registry name to construct a fully qualified image name for your function.

The OpenShift Container Registry is used by default as the image registry for storing function images. You can override this by using the -r flag:

Example build command

$ kn func build -r quay.io/username

Example output

Building function image
Function image has been built, image: quay.io/username/example-function:latest

To learn more about kn func build command options, you can use the help command:

Build help command

$ kn func help build

4.6.3. Deploying functions

You can deploy a function to your cluster as a Knative service by using the kn func deploy command. If the targeted function is already deployed, it is updated with a new container image that is pushed to a container image registry, and the Knative service is updated.

Prerequisites

  • The OpenShift Serverless Operator and Knative Serving are installed on the cluster.
  • You have installed the Knative (kn) CLI.
  • You have created a project or have access to a project with the appropriate roles and permissions to create applications and other workloads in OpenShift Container Platform.
  • You must have already created and initialized the function that you want to deploy.

Procedure

  • Deploy a function:

    $ kn func deploy [-n <namespace> -p <path> -i <image>]

    Example output

    Function deployed at: http://func.example.com

    • If no namespace is specified, the function is deployed in the current namespace.
    • The function is deployed from the current directory, unless a path is specified.
    • The Knative service name is derived from the project name, and cannot be changed using this command.

4.6.4. Listing existing functions

You can list existing functions by using kn func list. If you want to list functions that have been deployed as Knative services, you can also use kn service list.

Procedure

  • List existing functions:

    $ kn func list [-n <namespace> -p <path>]

    Example output

    NAME           NAMESPACE  RUNTIME  URL                                                                                      READY
    example-function  default    node     http://example-function.default.apps.ci-ln-g9f36hb-d5d6b.origin-ci-int-aws.dev.rhcloud.com  True

  • List functions deployed as Knative services:

    $ kn service list -n <namespace>

    Example output

    NAME            URL                                                                                       LATEST                AGE   CONDITIONS   READY   REASON
    example-function   http://example-function.default.apps.ci-ln-g9f36hb-d5d6b.origin-ci-int-aws.dev.rhcloud.com   example-function-gzl4c   16m   3 OK / 3     True

4.6.5. Describing a function

The kn func info command prints information about a deployed function, such as the function name, image, namespace, Knative service information, route information, and event subscriptions.

Procedure

  • Describe a function:

    $ kn func info [-f <format> -n <namespace> -p <path>]

    Example command

    $ kn func info -p function/example-function

    Example output

    Function name:
      example-function
    Function is built in image:
      docker.io/user/example-function:latest
    Function is deployed as Knative Service:
      example-function
    Function is deployed in namespace:
      default
    Routes:
      http://example-function.default.apps.ci-ln-g9f36hb-d5d6b.origin-ci-int-aws.dev.rhcloud.com

4.6.6. Invoking a deployed function with a test event

You can use the kn func invoke CLI command to send a test request to invoke a function either locally or on your OpenShift Container Platform cluster. This command can be used to test that a function is working and able to receive events correctly.

Example command

$ kn func invoke

The kn func invoke command executes on the local directory by default, and assumes that this directory is a function project.

4.6.6.1. kn func invoke optional parameters

You can specify optional parameters for the request by using the following kn func invoke CLI command flags.

FlagsDescription

-t, --target

Specifies the target instance of the invoked function, for example, local or remote or https://staging.example.com/. The default target is local.

-f, --format

Specifies the format of the message, for example, cloudevent or http.

--id

Specifies a unique string identifier for the request.

-n, --namespace

Specifies the namespace on the cluster.

--source

Specifies sender name for the request. This corresponds to the CloudEvent source attribute.

--type

Specifies the type of request, for example, boson.fn. This corresponds to the CloudEvent type attribute.

--data

Specifies content for the request. For CloudEvent requests, this is the CloudEvent data attribute.

--file

Specifies path to a local file containing data to be sent.

--content-type

Specifies the MIME content type for the request.

-p, --path

Specifies path to the project directory.

-c, --confirm

Enables prompting to interactively confirm all options.

-v, --verbose

Enables printing verbose output.

-h, --help

Prints information on usage of kn func invoke.

4.6.6.1.1. Main parameters

The following parameters define the main properties of the kn func invoke command:

Event target (-t, --target)
The target instance of the invoked function. Accepts the local value for a locally deployed function, the remote value for a remotely deployed function, or a URL for a function deployed to an arbitrary endpoint. If a target is not specified, it defaults to local.
Event message format (-f, --format)
The message format for the event, such as http or cloudevent. This defaults to the format of the template that was used when creating the function.
Event type (--type)
The type of event that is sent. You can find information about the type parameter that is set in the documentation for each event producer. For example, the API server source might set the type parameter of produced events as dev.knative.apiserver.resource.update.
Event source (--source)
The unique event source that produced the event. This might be a URI for the event source, for example https://10.96.0.1/, or the name of the event source.
Event ID (--id)
A random, unique ID that is created by the event producer.
Event data (--data)

Allows you to specify a data value for the event sent by the kn func invoke command. For example, you can specify a --data value such as "Hello World" so that the event contains this data string. By default, no data is included in the events created by kn func invoke.

Note

Functions that have been deployed to a cluster can respond to events from an existing event source that provides values for properties such as source and type. These events often have a data value in JSON format, which captures the domain specific context of the event. By using the CLI flags noted in this document, developers can simulate those events for local testing.

You can also send event data using the --file flag to provide a local file containing data for the event. In this case, specify the content type using --content-type.

Data content type (--content-type)
If you are using the --data flag to add data for events, you can use the --content-type flag to specify what type of data is carried by the event. In the previous example, the data is plain text, so you might specify kn func invoke --data "Hello world!" --content-type "text/plain".
4.6.6.1.2. Example commands

This is the general invocation of the kn func invoke command:

$ kn func invoke --type <event_type> --source <event_source> --data <event_data> --content-type <content_type> --id <event_ID> --format <format> --namespace <namespace>

For example, to send a "Hello world!" event, you can run:

$ kn func invoke --type ping --source example-ping --data "Hello world!" --content-type "text/plain" --id example-ID --format http --namespace my-ns
4.6.6.1.2.1. Specifying the file with data

To specify the file on disk that contains the event data, use the --file and --content-type flags:

$ kn func invoke --file <path> --content-type <content-type>

For example, to send JSON data stored in the test.json file, use this command:

$ kn func invoke --file ./test.json --content-type application/json
4.6.6.1.2.2. Specifying the function project

You can specify a path to the function project by using the --path flag:

$ kn func invoke --path <path_to_function>

For example, to use the function project located in the ./example/example-function directory, use this command:

$ kn func invoke --path ./example/example-function
4.6.6.1.2.3. Specifying where the target function is deployed

By default, kn func invoke targets the local deployment of the function:

$ kn func invoke

To use a different deployment, use the --target flag:

$ kn func invoke --target <target>

For example, to use the function deployed on the cluster, use the --target remote flag:

$ kn func invoke --target remote

To use the function deployed at an arbitrary URL, use the --target <URL> flag:

$ kn func invoke --target "https://my-event-broker.example.com"

You can explicitly target the local deployment. In this case, if the function is not running locally, the command fails:

$ kn func invoke --target local

4.6.7. Deleting a function

You can delete a function from your cluster by using the kn func delete command.

Procedure

  • Delete a function:

    $ kn func delete [<function_name> -n <namespace> -p <path>]
    • If the name or path of the function to delete is not specified, the current directory is searched for a func.yaml file that is used to determine the function to delete.
    • If the namespace is not specified, it defaults to the namespace value in the func.yaml file.