Appendix G. Kafka Streams configuration parameters

application.id

Type: string
Importance: high

An identifier for the stream processing application. Must be unique within the Kafka cluster. It is used as 1) the default client-id prefix, 2) the group-id for membership management, 3) the changelog topic prefix.

bootstrap.servers

Type: list
Importance: high

A list of host/port pairs to use for establishing the initial connection to the Kafka cluster. The client will make use of all servers irrespective of which servers are specified here for bootstrapping—this list only impacts the initial hosts used to discover the full set of servers. This list should be in the form host1:port1,host2:port2,…​. Since these servers are just used for the initial connection to discover the full cluster membership (which may change dynamically), this list need not contain the full set of servers (you may want more than one, though, in case a server is down).

replication.factor

Type: int
Default: 1
Importance: high

The replication factor for change log topics and repartition topics created by the stream processing application.

state.dir

Type: string
Default: /tmp/kafka-streams
Importance: high

Directory location for state store.

cache.max.bytes.buffering

Type: long
Default: 10485760
Valid Values: [0,…​]
Importance: medium

Maximum number of memory bytes to be used for buffering across all threads.

client.id

Type: string
Default: ""
Importance: medium

An ID prefix string used for the client IDs of internal consumer, producer and restore-consumer, with pattern '<client.id>-StreamThread-<threadSequenceNumber>-<consumer|producer|restore-consumer>'.

default.deserialization.exception.handler

Type: class
Default: org.apache.kafka.streams.errors.LogAndFailExceptionHandler
Importance: medium

Exception handling class that implements the org.apache.kafka.streams.errors.DeserializationExceptionHandler interface.

default.key.serde

Type: class
Default: org.apache.kafka.common.serialization.Serdes$ByteArraySerde
Importance: medium

Default serializer / deserializer class for key that implements the org.apache.kafka.common.serialization.Serde interface. Note when windowed serde class is used, one needs to set the inner serde class that implements the org.apache.kafka.common.serialization.Serde interface via 'default.windowed.key.serde.inner' or 'default.windowed.value.serde.inner' as well.

default.production.exception.handler

Type: class
Default: org.apache.kafka.streams.errors.DefaultProductionExceptionHandler
Importance: medium

Exception handling class that implements the org.apache.kafka.streams.errors.ProductionExceptionHandler interface.

default.timestamp.extractor

Type: class
Default: org.apache.kafka.streams.processor.FailOnInvalidTimestamp
Importance: medium

Default timestamp extractor class that implements the org.apache.kafka.streams.processor.TimestampExtractor interface.

default.value.serde

Type: class
Default: org.apache.kafka.common.serialization.Serdes$ByteArraySerde
Importance: medium

Default serializer / deserializer class for value that implements the org.apache.kafka.common.serialization.Serde interface. Note when windowed serde class is used, one needs to set the inner serde class that implements the org.apache.kafka.common.serialization.Serde interface via 'default.windowed.key.serde.inner' or 'default.windowed.value.serde.inner' as well.

num.standby.replicas

Type: int
Default: 0
Importance: medium

The number of standby replicas for each task.

num.stream.threads

Type: int
Default: 1
Importance: medium

The number of threads to execute stream processing.

processing.guarantee

Type: string
Default: at_least_once
Valid Values: [at_least_once, exactly_once]
Importance: medium

The processing guarantee that should be used. Possible values are at_least_once (default) and exactly_once. Note that exactly-once processing requires a cluster of at least three brokers by default what is the recommended setting for production; for development you can change this, by adjusting broker setting transaction.state.log.replication.factor.

security.protocol

Type: string
Default: PLAINTEXT
Importance: medium

Protocol used to communicate with brokers. Valid values are: PLAINTEXT, SSL, SASL_PLAINTEXT, SASL_SSL.

topology.optimization

Type: string
Default: none
Valid Values: [none, all]
Importance: medium

A configuration telling Kafka Streams if it should optimize the topology, disabled by default.

application.server

Type: string
Default: ""
Importance: low

A host:port pair pointing to an embedded user defined endpoint that can be used for discovering the locations of state stores within a single KafkaStreams application.

buffered.records.per.partition

Type: int
Default: 1000
Importance: low

The maximum number of records to buffer per partition.

commit.interval.ms

Type: long
Default: 30000
Importance: low

The frequency with which to save the position of the processor. (Note, if 'processing.guarantee' is set to 'exactly_once', the default value is 100, otherwise the default value is 30000.

connections.max.idle.ms

Type: long
Default: 540000
Importance: low

Close idle connections after the number of milliseconds specified by this config.

metadata.max.age.ms

Type: long
Default: 300000
Valid Values: [0,…​]
Importance: low

The period of time in milliseconds after which we force a refresh of metadata even if we haven’t seen any partition leadership changes to proactively discover any new brokers or partitions.

metric.reporters

Type: list
Default: ""
Importance: low

A list of classes to use as metrics reporters. Implementing the org.apache.kafka.common.metrics.MetricsReporter interface allows plugging in classes that will be notified of new metric creation. The JmxReporter is always included to register JMX statistics.

metrics.num.samples

Type: int
Default: 2
Valid Values: [1,…​]
Importance: low

The number of samples maintained to compute metrics.

metrics.recording.level

Type: string
Default: INFO
Valid Values: [INFO, DEBUG]
Importance: low

The highest recording level for metrics.

metrics.sample.window.ms

Type: long
Default: 30000
Valid Values: [0,…​]
Importance: low

The window of time a metrics sample is computed over.

partition.grouper

Type: class
Default: org.apache.kafka.streams.processor.DefaultPartitionGrouper
Importance: low

Partition grouper class that implements the org.apache.kafka.streams.processor.PartitionGrouper interface.

poll.ms

Type: long
Default: 100
Importance: low

The amount of time in milliseconds to block waiting for input.

receive.buffer.bytes

Type: int
Default: 32768
Valid Values: [0,…​]
Importance: low

The size of the TCP receive buffer (SO_RCVBUF) to use when reading data. If the value is -1, the OS default will be used.

reconnect.backoff.max.ms

Type: long
Default: 1000
Valid Values: [0,…​]
Importance: low

The maximum amount of time in milliseconds to wait when reconnecting to a broker that has repeatedly failed to connect. If provided, the backoff per host will increase exponentially for each consecutive connection failure, up to this maximum. After calculating the backoff increase, 20% random jitter is added to avoid connection storms.

reconnect.backoff.ms

Type: long
Default: 50
Valid Values: [0,…​]
Importance: low

The base amount of time to wait before attempting to reconnect to a given host. This avoids repeatedly connecting to a host in a tight loop. This backoff applies to all connection attempts by the client to a broker.

request.timeout.ms

Type: int
Default: 40000
Valid Values: [0,…​]
Importance: low

The configuration controls the maximum amount of time the client will wait for the response of a request. If the response is not received before the timeout elapses the client will resend the request if necessary or fail the request if retries are exhausted.

retries

Type: int
Default: 0
Valid Values: [0,…​,2147483647]
Importance: low

Setting a value greater than zero will cause the client to resend any request that fails with a potentially transient error.

retry.backoff.ms

Type: long
Default: 100
Valid Values: [0,…​]
Importance: low

The amount of time to wait before attempting to retry a failed request to a given topic partition. This avoids repeatedly sending requests in a tight loop under some failure scenarios.

rocksdb.config.setter

Type: class
Default: null
Importance: low

A Rocks DB config setter class or class name that implements the org.apache.kafka.streams.state.RocksDBConfigSetter interface.

send.buffer.bytes

Type: int
Default: 131072
Valid Values: [0,…​]
Importance: low

The size of the TCP send buffer (SO_SNDBUF) to use when sending data. If the value is -1, the OS default will be used.

state.cleanup.delay.ms

Type: long
Default: 600000
Importance: low

The amount of time in milliseconds to wait before deleting state when a partition has migrated. Only state directories that have not been modified for at least state.cleanup.delay.ms will be removed.

upgrade.from

Type: string
Default: null
Valid Values: [null, 0.10.0, 0.10.1, 0.10.2, 0.11.0, 1.0, 1.1]
Importance: low

Allows upgrading from versions 0.10.0/0.10.1/0.10.2/0.11.0/1.0/1.1 to version 1.2 (or newer) in a backward compatible way. When upgrading from 1.2 to a newer version it is not required to specify this config.Default is null. Accepted values are "0.10.0", "0.10.1", "0.10.2", "0.11.0", "1.0", "1.1" (for upgrading from the corresponding old version).

windowstore.changelog.additional.retention.ms

Type: long
Default: 86400000
Importance: low

Added to a windows maintainMs to ensure data is not deleted from the log prematurely. Allows for clock drift. Default is 1 day.