Appendix G. Kafka Streams configuration parameters

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.

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).

Type: int
Default: 1
Importance: high

The replication factor for change log topics and repartition topics created by the stream processing application. If your broker cluster is on version 2.4 or newer, you can set -1 to use the broker default replication factor.

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

Directory location for state store. This path must be unique for each streams instance sharing the same underlying filesystem.

Type: long
Default: 10000
Valid Values: [0,…​]
Importance: medium

The maximum acceptable lag (number of offsets to catch up) for a client to be considered caught-up for an active task.Should correspond to a recovery time of well under a minute for a given workload. Must be at least 0.

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

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

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>'.

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

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

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.

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

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

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.

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.

Type: class
Default: null
Importance: medium

Default serializer / deserializer for the inner class of a windowed key. Must implement the org.apache.kafka.common.serialization.Serde interface.

Type: class
Default: null
Importance: medium

Default serializer / deserializer for the inner class of a windowed value. Must implement the org.apache.kafka.common.serialization.Serde interface.

Type: long
Default: 0
Importance: medium

Maximum amount of time in milliseconds a stream task will stay idle when not all of its partition buffers contain records, to avoid potential out-of-order record processing across multiple input streams.

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

The maximum number of warmup replicas (extra standbys beyond the configured num.standbys) that can be assigned at once for the purpose of keeping the task available on one instance while it is warming up on another instance it has been reassigned to. Used to throttle how much extra broker traffic and cluster state can be used for high availability. Must be at least 1.

Type: int
Default: 0
Importance: medium

The number of standby replicas for each task.

Type: int
Default: 1
Importance: medium

The number of threads to execute stream processing.

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

The processing guarantee that should be used. Possible values are at_least_once (default), exactly_once (requires brokers version 0.11.0 or higher), and exactly_once_beta (requires brokers version 2.5 or higher). 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 and transaction.state.log.min.isr.

Type: string
Default: PLAINTEXT
Importance: medium

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

Type: long
Default: 300000 (5 minutes)
Valid Values: [0,…​]
Importance: medium

The maximum amount of time in milliseconds a task might stall due to internal errors and retries until an error is raised. For a timeout of 0ms, a task would raise an error for the first internal error. For any timeout larger than 0ms, a task will retry at least once before an error is raised.

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

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

Type: string
Default: ""
Importance: low

A host:port pair pointing to a user-defined endpoint that can be used for state store discovery and interactive queries on this KafkaStreams instance.

Type: int
Default: 1000
Importance: low

Maximum number of records to buffer per partition.

Type: string
Default: latest
Valid Values: [0.10.0-2.4, latest]
Importance: low

Version of the built-in metrics to use.

Type: long
Default: 30000 (30 seconds)
Valid Values: [0,…​]
Importance: low

The frequency in milliseconds 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.

Type: long
Default: 540000 (9 minutes)
Importance: low

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

Type: long
Default: 300000 (5 minutes)
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.

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.

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

The number of samples maintained to compute metrics.

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

The highest recording level for metrics.

Type: long
Default: 30000 (30 seconds)
Valid Values: [0,…​]
Importance: low

The window of time a metrics sample is computed over.

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

Partition grouper class that implements the org.apache.kafka.streams.processor.PartitionGrouper interface. WARNING: This config is deprecated and will be removed in 3.0.0 release.

Type: long
Default: 100
Importance: low

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

Type: long
Default: 600000 (10 minutes)
Valid Values: [60000,…​]
Importance: low

The maximum time in milliseconds to wait before triggering a rebalance to probe for warmup replicas that have finished warming up and are ready to become active. Probing rebalances will continue to be triggered until the assignment is balanced. Must be at least 1 minute.

Type: int
Default: 32768 (32 kibibytes)
Valid Values: [-1,…​]
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.

Type: long
Default: 1000 (1 second)
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.

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.

Type: int
Default: 40000 (40 seconds)
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.

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. It is recommended to set the value to either zero or MAX_VALUE and use corresponding timeout parameters to control how long a client should retry a request.

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.

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.

Type: int
Default: 131072 (128 kibibytes)
Valid Values: [-1,…​]
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.

Type: long
Default: 600000 (10 minutes)
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.

Type: string
Default: null
Valid Values: [null, 0.10.0, 0.10.1, 0.10.2, 0.11.0, 1.0, 1.1, 2.0, 2.1, 2.2, 2.3]
Importance: low

Allows upgrading in a backward compatible way. This is needed when upgrading from [0.10.0, 1.1] to 2.0+, or when upgrading from [2.0, 2.3] to 2.4+. When upgrading from 2.4 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", "2.0", "2.1", "2.2", "2.3" (for upgrading from the corresponding old version).

Type: long
Default: null
Importance: low

Sets window size for the deserializer in order to calculate window end times.

Type: long
Default: 86400000 (1 day)
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.