Configuration

• 1: Configuration

1 - Configuration

Kafka uses key-value pairs in the property file format for configuration. These values can be supplied either from a file or programmatically.

Broker Configs

The essential configurations are the following:

• broker.id
• log.dirs
• zookeeper.connect Topic-level configurations and defaults are discussed in more detail below.

  Name	Description	Type	Default	Valid Values	Importance
  zookeeper.connect	Zookeeper host string	string			high
  advertised.host.name	DEPRECATED: only used when `advertised.listeners` or `listeners` are not set. Use `advertised.listeners` instead. Hostname to publish to ZooKeeper for clients to use. In IaaS environments, this may need to be different from the interface to which the broker binds. If this is not set, it will use the value for `host.name` if configured. Otherwise it will use the value returned from java.net.InetAddress.getCanonicalHostName().	string	null		high
  advertised.listeners	Listeners to publish to ZooKeeper for clients to use, if different than the listeners above. In IaaS environments, this may need to be different from the interface to which the broker binds. If this is not set, the value for `listeners` will be used.	string	null		high
  advertised.port	DEPRECATED: only used when `advertised.listeners` or `listeners` are not set. Use `advertised.listeners` instead. The port to publish to ZooKeeper for clients to use. In IaaS environments, this may need to be different from the port to which the broker binds. If this is not set, it will publish the same port that the broker binds to.	int	null		high
  auto.create.topics.enable	Enable auto creation of topic on the server	boolean	true		high
  auto.leader.rebalance.enable	Enables auto leader balancing. A background thread checks and triggers leader balance if required at regular intervals	boolean	true		high
  background.threads	The number of threads to use for various background processing tasks	int	10	[1,...]	high
  broker.id	The broker id for this server. If unset, a unique broker id will be generated.To avoid conflicts between zookeeper generated broker id's and user configured broker id's, generated broker ids start from reserved.broker.max.id + 1.	int	-1		high
  compression.type	Specify the final compression type for a given topic. This configuration accepts the standard compression codecs ('gzip', 'snappy', 'lz4'). It additionally accepts 'uncompressed' which is equivalent to no compression; and 'producer' which means retain the original compression codec set by the producer.	string	producer		high
  delete.topic.enable	Enables delete topic. Delete topic through the admin tool will have no effect if this config is turned off	boolean	false		high
  host.name	DEPRECATED: only used when `listeners` is not set. Use `listeners` instead. hostname of broker. If this is set, it will only bind to this address. If this is not set, it will bind to all interfaces	string	""		high
  leader.imbalance.check.interval.seconds	The frequency with which the partition rebalance check is triggered by the controller	long	300		high
  leader.imbalance.per.broker.percentage	The ratio of leader imbalance allowed per broker. The controller would trigger a leader balance if it goes above this value per broker. The value is specified in percentage.	int	10		high
  listeners	Listener List - Comma-separated list of URIs we will listen on and the listener names. If the listener name is not a security protocol, listener.security.protocol.map must also be set. Specify hostname as 0.0.0.0 to bind to all interfaces. Leave hostname empty to bind to default interface. Examples of legal listener lists: PLAINTEXT://myhost:9092,SSL://:9091 CLIENT://0.0.0.0:9092,REPLICATION://localhost:9093	string	null		high
  log.dir	The directory in which the log data is kept (supplemental for log.dirs property)	string	/tmp/kafka-logs		high
  log.dirs	The directories in which the log data is kept. If not set, the value in log.dir is used	string	null		high
  log.flush.interval.messages	The number of messages accumulated on a log partition before messages are flushed to disk	long	9223372036854775807	[1,...]	high
  log.flush.interval.ms	The maximum time in ms that a message in any topic is kept in memory before flushed to disk. If not set, the value in log.flush.scheduler.interval.ms is used	long	null		high
  log.flush.offset.checkpoint.interval.ms	The frequency with which we update the persistent record of the last flush which acts as the log recovery point	int	60000	[0,...]	high
  log.flush.scheduler.interval.ms	The frequency in ms that the log flusher checks whether any log needs to be flushed to disk	long	9223372036854775807		high
  log.flush.start.offset.checkpoint.interval.ms	The frequency with which we update the persistent record of log start offset	int	60000	[0,...]	high
  log.retention.bytes	The maximum size of the log before deleting it	long	-1		high
  log.retention.hours	The number of hours to keep a log file before deleting it (in hours), tertiary to log.retention.ms property	int	168		high
  log.retention.minutes	The number of minutes to keep a log file before deleting it (in minutes), secondary to log.retention.ms property. If not set, the value in log.retention.hours is used	int	null		high
  log.retention.ms	The number of milliseconds to keep a log file before deleting it (in milliseconds), If not set, the value in log.retention.minutes is used	long	null		high
  log.roll.hours	The maximum time before a new log segment is rolled out (in hours), secondary to log.roll.ms property	int	168	[1,...]	high
  log.roll.jitter.hours	The maximum jitter to subtract from logRollTimeMillis (in hours), secondary to log.roll.jitter.ms property	int	0	[0,...]	high
  log.roll.jitter.ms	The maximum jitter to subtract from logRollTimeMillis (in milliseconds). If not set, the value in log.roll.jitter.hours is used	long	null		high
  log.roll.ms	The maximum time before a new log segment is rolled out (in milliseconds). If not set, the value in log.roll.hours is used	long	null		high
  log.segment.bytes	The maximum size of a single log file	int	1073741824	[14,...]	high
  log.segment.delete.delay.ms	The amount of time to wait before deleting a file from the filesystem	long	60000	[0,...]	high
  message.max.bytes	The largest record batch size allowed by Kafka. If this is increased and there are consumers older than 0.10.2, the consumers' fetch size must also be increased so that the they can fetch record batches this large. In the latest message format version, records are always grouped into batches for efficiency. In previous message format versions, uncompressed records are not grouped into batches and this limit only applies to a single record in that case. This can be set per topic with the topic level max.message.bytes config.	int	1000012	[0,...]	high
  min.insync.replicas	When a producer sets acks to "all" (or "-1"), min.insync.replicas specifies the minimum number of replicas that must acknowledge a write for the write to be considered successful. If this minimum cannot be met, then the producer will raise an exception (either NotEnoughReplicas or NotEnoughReplicasAfterAppend). When used together, min.insync.replicas and acks allow you to enforce greater durability guarantees. A typical scenario would be to create a topic with a replication factor of 3, set min.insync.replicas to 2, and produce with acks of "all". This will ensure that the producer raises an exception if a majority of replicas do not receive a write.	int	1	[1,...]	high
  num.io.threads	The number of threads that the server uses for processing requests, which may include disk I/O	int	8	[1,...]	high
  num.network.threads	The number of threads that the server uses for receiving requests from the network and sending responses to the network	int	3	[1,...]	high
  num.recovery.threads.per.data.dir	The number of threads per data directory to be used for log recovery at startup and flushing at shutdown	int	1	[1,...]	high
  num.replica.fetchers	Number of fetcher threads used to replicate messages from a source broker. Increasing this value can increase the degree of I/O parallelism in the follower broker.	int	1		high
  offset.metadata.max.bytes	The maximum size for a metadata entry associated with an offset commit	int	4096		high
  offsets.commit.required.acks	The required acks before the commit can be accepted. In general, the default (-1) should not be overridden	short	-1		high
  offsets.commit.timeout.ms	Offset commit will be delayed until all replicas for the offsets topic receive the commit or this timeout is reached. This is similar to the producer request timeout.	int	5000	[1,...]	high
  offsets.load.buffer.size	Batch size for reading from the offsets segments when loading offsets into the cache.	int	5242880	[1,...]	high
  offsets.retention.check.interval.ms	Frequency at which to check for stale offsets	long	600000	[1,...]	high
  offsets.retention.minutes	Log retention window in minutes for offsets topic	int	1440	[1,...]	high
  offsets.topic.compression.codec	Compression codec for the offsets topic - compression may be used to achieve "atomic" commits	int	0		high
  offsets.topic.num.partitions	The number of partitions for the offset commit topic (should not change after deployment)	int	50	[1,...]	high
  offsets.topic.replication.factor	The replication factor for the offsets topic (set higher to ensure availability). Internal topic creation will fail until the cluster size meets this replication factor requirement.	short	3	[1,...]	high
  offsets.topic.segment.bytes	The offsets topic segment bytes should be kept relatively small in order to facilitate faster log compaction and cache loads	int	104857600	[1,...]	high
  port	DEPRECATED: only used when `listeners` is not set. Use `listeners` instead. the port to listen and accept connections on	int	9092		high
  queued.max.requests	The number of queued requests allowed before blocking the network threads	int	500	[1,...]	high
  quota.consumer.default	DEPRECATED: Used only when dynamic default quotas are not configured for or in Zookeeper. Any consumer distinguished by clientId/consumer group will get throttled if it fetches more bytes than this value per-second	long	9223372036854775807	[1,...]	high
  quota.producer.default	DEPRECATED: Used only when dynamic default quotas are not configured for , or in Zookeeper. Any producer distinguished by clientId will get throttled if it produces more bytes than this value per-second	long	9223372036854775807	[1,...]	high
  replica.fetch.min.bytes	Minimum bytes expected for each fetch response. If not enough bytes, wait up to replicaMaxWaitTimeMs	int	1		high
  replica.fetch.wait.max.ms	max wait time for each fetcher request issued by follower replicas. This value should always be less than the replica.lag.time.max.ms at all times to prevent frequent shrinking of ISR for low throughput topics	int	500		high
  replica.high.watermark.checkpoint.interval.ms	The frequency with which the high watermark is saved out to disk	long	5000		high
  replica.lag.time.max.ms	If a follower hasn't sent any fetch requests or hasn't consumed up to the leaders log end offset for at least this time, the leader will remove the follower from isr	long	10000		high
  replica.socket.receive.buffer.bytes	The socket receive buffer for network requests	int	65536		high
  replica.socket.timeout.ms	The socket timeout for network requests. Its value should be at least replica.fetch.wait.max.ms	int	30000		high
  request.timeout.ms	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.	int	30000		high
  socket.receive.buffer.bytes	The SO_RCVBUF buffer of the socket sever sockets. If the value is -1, the OS default will be used.	int	102400		high
  socket.request.max.bytes	The maximum number of bytes in a socket request	int	104857600	[1,...]	high
  socket.send.buffer.bytes	The SO_SNDBUF buffer of the socket sever sockets. If the value is -1, the OS default will be used.	int	102400		high
  transaction.max.timeout.ms	The maximum allowed timeout for transactions. If a client’s requested transaction time exceed this, then the broker will return an error in InitProducerIdRequest. This prevents a client from too large of a timeout, which can stall consumers reading from topics included in the transaction.	int	900000	[1,...]	high
  transaction.state.log.load.buffer.size	Batch size for reading from the transaction log segments when loading producer ids and transactions into the cache.	int	5242880	[1,...]	high
  transaction.state.log.min.isr	Overridden min.insync.replicas config for the transaction topic.	int	2	[1,...]	high
  transaction.state.log.num.partitions	The number of partitions for the transaction topic (should not change after deployment).	int	50	[1,...]	high
  transaction.state.log.replication.factor	The replication factor for the transaction topic (set higher to ensure availability). Internal topic creation will fail until the cluster size meets this replication factor requirement.	short	3	[1,...]	high
  transaction.state.log.segment.bytes	The transaction topic segment bytes should be kept relatively small in order to facilitate faster log compaction and cache loads	int	104857600	[1,...]	high
  transactional.id.expiration.ms	The maximum amount of time in ms that the transaction coordinator will wait before proactively expire a producer's transactional id without receiving any transaction status updates from it.	int	604800000	[1,...]	high
  unclean.leader.election.enable	Indicates whether to enable replicas not in the ISR set to be elected as leader as a last resort, even though doing so may result in data loss	boolean	false		high
  zookeeper.connection.timeout.ms	The max time that the client waits to establish a connection to zookeeper. If not set, the value in zookeeper.session.timeout.ms is used	int	null		high
  zookeeper.session.timeout.ms	Zookeeper session timeout	int	6000		high
  zookeeper.set.acl	Set client to use secure ACLs	boolean	false		high
  broker.id.generation.enable	Enable automatic broker id generation on the server. When enabled the value configured for reserved.broker.max.id should be reviewed.	boolean	true		medium
  broker.rack	Rack of the broker. This will be used in rack aware replication assignment for fault tolerance. Examples: `RACK1`, `us-east-1d`	string	null		medium
  connections.max.idle.ms	Idle connections timeout: the server socket processor threads close the connections that idle more than this	long	600000		medium
  controlled.shutdown.enable	Enable controlled shutdown of the server	boolean	true		medium
  controlled.shutdown.max.retries	Controlled shutdown can fail for multiple reasons. This determines the number of retries when such failure happens	int	3		medium
  controlled.shutdown.retry.backoff.ms	Before each retry, the system needs time to recover from the state that caused the previous failure (Controller fail over, replica lag etc). This config determines the amount of time to wait before retrying.	long	5000		medium
  controller.socket.timeout.ms	The socket timeout for controller-to-broker channels	int	30000		medium
  default.replication.factor	default replication factors for automatically created topics	int	1		medium
  delete.records.purgatory.purge.interval.requests	The purge interval (in number of requests) of the delete records request purgatory	int	1		medium
  fetch.purgatory.purge.interval.requests	The purge interval (in number of requests) of the fetch request purgatory	int	1000		medium
  group.initial.rebalance.delay.ms	The amount of time the group coordinator will wait for more consumers to join a new group before performing the first rebalance. A longer delay means potentially fewer rebalances, but increases the time until processing begins.	int	3000		medium
  group.max.session.timeout.ms	The maximum allowed session timeout for registered consumers. Longer timeouts give consumers more time to process messages in between heartbeats at the cost of a longer time to detect failures.	int	300000		medium
  group.min.session.timeout.ms	The minimum allowed session timeout for registered consumers. Shorter timeouts result in quicker failure detection at the cost of more frequent consumer heartbeating, which can overwhelm broker resources.	int	6000		medium
  inter.broker.listener.name	Name of listener used for communication between brokers. If this is unset, the listener name is defined by security.inter.broker.protocol. It is an error to set this and security.inter.broker.protocol properties at the same time.	string	null		medium
  inter.broker.protocol.version	Specify which version of the inter-broker protocol will be used. This is typically bumped after all brokers were upgraded to a new version. Example of some valid values are: 0.8.0, 0.8.1, 0.8.1.1, 0.8.2, 0.8.2.0, 0.8.2.1, 0.9.0.0, 0.9.0.1 Check ApiVersion for the full list.	string	0.11.0-IV2		medium
  log.cleaner.backoff.ms	The amount of time to sleep when there are no logs to clean	long	15000	[0,...]	medium
  log.cleaner.dedupe.buffer.size	The total memory used for log deduplication across all cleaner threads	long	134217728		medium
  log.cleaner.delete.retention.ms	How long are delete records retained?	long	86400000		medium
  log.cleaner.enable	Enable the log cleaner process to run on the server. Should be enabled if using any topics with a cleanup.policy=compact including the internal offsets topic. If disabled those topics will not be compacted and continually grow in size.	boolean	true		medium
  log.cleaner.io.buffer.load.factor	Log cleaner dedupe buffer load factor. The percentage full the dedupe buffer can become. A higher value will allow more log to be cleaned at once but will lead to more hash collisions	double	0.9		medium
  log.cleaner.io.buffer.size	The total memory used for log cleaner I/O buffers across all cleaner threads	int	524288	[0,...]	medium
  log.cleaner.io.max.bytes.per.second	The log cleaner will be throttled so that the sum of its read and write i/o will be less than this value on average	double	1.7976931348623157E308		medium
  log.cleaner.min.cleanable.ratio	The minimum ratio of dirty log to total log for a log to eligible for cleaning	double	0.5		medium
  log.cleaner.min.compaction.lag.ms	The minimum time a message will remain uncompacted in the log. Only applicable for logs that are being compacted.	long	0		medium
  log.cleaner.threads	The number of background threads to use for log cleaning	int	1	[0,...]	medium
  log.cleanup.policy	The default cleanup policy for segments beyond the retention window. A comma separated list of valid policies. Valid policies are: "delete" and "compact"	list	delete	[compact, delete]	medium
  log.index.interval.bytes	The interval with which we add an entry to the offset index	int	4096	[0,...]	medium
  log.index.size.max.bytes	The maximum size in bytes of the offset index	int	10485760	[4,...]	medium
  log.message.format.version	Specify the message format version the broker will use to append messages to the logs. The value should be a valid ApiVersion. Some examples are: 0.8.2, 0.9.0.0, 0.10.0, check ApiVersion for more details. By setting a particular message format version, the user is certifying that all the existing messages on disk are smaller or equal than the specified version. Setting this value incorrectly will cause consumers with older versions to break as they will receive messages with a format that they don't understand.	string	0.11.0-IV2		medium
  log.message.timestamp.difference.max.ms	The maximum difference allowed between the timestamp when a broker receives a message and the timestamp specified in the message. If log.message.timestamp.type=CreateTime, a message will be rejected if the difference in timestamp exceeds this threshold. This configuration is ignored if log.message.timestamp.type=LogAppendTime.The maximum timestamp difference allowed should be no greater than log.retention.ms to avoid unnecessarily frequent log rolling.	long	9223372036854775807		medium
  log.message.timestamp.type	Define whether the timestamp in the message is message create time or log append time. The value should be either `CreateTime` or `LogAppendTime`	string	CreateTime	[CreateTime, LogAppendTime]	medium
  log.preallocate	Should pre allocate file when create new segment? If you are using Kafka on Windows, you probably need to set it to true.	boolean	false		medium
  log.retention.check.interval.ms	The frequency in milliseconds that the log cleaner checks whether any log is eligible for deletion	long	300000	[1,...]	medium
  max.connections.per.ip	The maximum number of connections we allow from each ip address	int	2147483647	[1,...]	medium
  max.connections.per.ip.overrides	Per-ip or hostname overrides to the default maximum number of connections	string	""		medium
  num.partitions	The default number of log partitions per topic	int	1	[1,...]	medium
  principal.builder.class	The fully qualified name of a class that implements the PrincipalBuilder interface, which is currently used to build the Principal for connections with the SSL SecurityProtocol.	class	org.apache.kafka.common.security.auth.DefaultPrincipalBuilder		medium
  producer.purgatory.purge.interval.requests	The purge interval (in number of requests) of the producer request purgatory	int	1000		medium
  replica.fetch.backoff.ms	The amount of time to sleep when fetch partition error occurs.	int	1000	[0,...]	medium
  replica.fetch.max.bytes	The number of bytes of messages to attempt to fetch for each partition. This is not an absolute maximum, if the first record batch in the first non-empty partition of the fetch is larger than this value, the record batch will still be returned to ensure that progress can be made. The maximum record batch size accepted by the broker is defined via message.max.bytes (broker config) or max.message.bytes (topic config).	int	1048576	[0,...]	medium
  replica.fetch.response.max.bytes	Maximum bytes expected for the entire fetch response. Records are fetched in batches, and if the first record batch in the first non-empty partition of the fetch is larger than this value, the record batch will still be returned to ensure that progress can be made. As such, this is not an absolute maximum. The maximum record batch size accepted by the broker is defined via message.max.bytes (broker config) or max.message.bytes (topic config).	int	10485760	[0,...]	medium
  reserved.broker.max.id	Max number that can be used for a broker.id	int	1000	[0,...]	medium
  sasl.enabled.mechanisms	The list of SASL mechanisms enabled in the Kafka server. The list may contain any mechanism for which a security provider is available. Only GSSAPI is enabled by default.	list	GSSAPI		medium
  sasl.kerberos.kinit.cmd	Kerberos kinit command path.	string	/usr/bin/kinit		medium
  sasl.kerberos.min.time.before.relogin	Login thread sleep time between refresh attempts.	long	60000		medium
  sasl.kerberos.principal.to.local.rules	A list of rules for mapping from principal names to short names (typically operating system usernames). The rules are evaluated in order and the first rule that matches a principal name is used to map it to a short name. Any later rules in the list are ignored. By default, principal names of the form {username}/{hostname}@{REALM} are mapped to {username}. For more details on the format please see security authorization and acls.	list	DEFAULT		medium
  sasl.kerberos.service.name	The Kerberos principal name that Kafka runs as. This can be defined either in Kafka's JAAS config or in Kafka's config.	string	null		medium
  sasl.kerberos.ticket.renew.jitter	Percentage of random jitter added to the renewal time.	double	0.05		medium
  sasl.kerberos.ticket.renew.window.factor	Login thread will sleep until the specified window factor of time from last refresh to ticket's expiry has been reached, at which time it will try to renew the ticket.	double	0.8		medium
  sasl.mechanism.inter.broker.protocol	SASL mechanism used for inter-broker communication. Default is GSSAPI.	string	GSSAPI		medium
  security.inter.broker.protocol	Security protocol used to communicate between brokers. Valid values are: PLAINTEXT, SSL, SASL_PLAINTEXT, SASL_SSL. It is an error to set this and inter.broker.listener.name properties at the same time.	string	PLAINTEXT		medium
  ssl.cipher.suites	A list of cipher suites. This is a named combination of authentication, encryption, MAC and key exchange algorithm used to negotiate the security settings for a network connection using TLS or SSL network protocol. By default all the available cipher suites are supported.	list	null		medium
  ssl.client.auth	Configures kafka broker to request client authentication. The following settings are common: ssl.client.auth=required If set to required client authentication is required. ssl.client.auth=requested This means client authentication is optional. unlike requested , if this option is set client can choose not to provide authentication information about itself ssl.client.auth=none This means client authentication is not needed.	string	none	[required, requested, none]	medium
  ssl.enabled.protocols	The list of protocols enabled for SSL connections.	list	TLSv1.2,TLSv1.1,TLSv1		medium
  ssl.key.password	The password of the private key in the key store file. This is optional for client.	password	null		medium
  ssl.keymanager.algorithm	The algorithm used by key manager factory for SSL connections. Default value is the key manager factory algorithm configured for the Java Virtual Machine.	string	SunX509		medium
  ssl.keystore.location	The location of the key store file. This is optional for client and can be used for two-way authentication for client.	string	null		medium
  ssl.keystore.password	The store password for the key store file. This is optional for client and only needed if ssl.keystore.location is configured.	password	null		medium
  ssl.keystore.type	The file format of the key store file. This is optional for client.	string	JKS		medium
  ssl.protocol	The SSL protocol used to generate the SSLContext. Default setting is TLS, which is fine for most cases. Allowed values in recent JVMs are TLS, TLSv1.1 and TLSv1.2. SSL, SSLv2 and SSLv3 may be supported in older JVMs, but their usage is discouraged due to known security vulnerabilities.	string	TLS		medium
  ssl.provider	The name of the security provider used for SSL connections. Default value is the default security provider of the JVM.	string	null		medium
  ssl.trustmanager.algorithm	The algorithm used by trust manager factory for SSL connections. Default value is the trust manager factory algorithm configured for the Java Virtual Machine.	string	PKIX		medium
  ssl.truststore.location	The location of the trust store file.	string	null		medium
  ssl.truststore.password	The password for the trust store file. If a password is not set access to the truststore is still available, but integrity checking is disabled.	password	null		medium
  ssl.truststore.type	The file format of the trust store file.	string	JKS		medium
  alter.config.policy.class.name	The alter configs policy class that should be used for validation. The class should implement the org.apache.kafka.server.policy.AlterConfigPolicy interface.	class	null		low
  authorizer.class.name	The authorizer class that should be used for authorization	string	""		low
  create.topic.policy.class.name	The create topic policy class that should be used for validation. The class should implement the org.apache.kafka.server.policy.CreateTopicPolicy interface.	class	null		low
  listener.security.protocol.map	Map between listener names and security protocols. This must be defined for the same security protocol to be usable in more than one port or IP. For example, we can separate internal and external traffic even if SSL is required for both. Concretely, we could define listeners with names INTERNAL and EXTERNAL and this property as: `INTERNAL:SSL,EXTERNAL:SSL`. As shown, key and value are separated by a colon and map entries are separated by commas. Each listener name should only appear once in the map.	string	SSL:SSL,SASL_PLAINTEXT:SASL_PLAINTEXT,TRACE:TRACE,SASL_SSL:SASL_SSL,PLAINTEXT:PLAINTEXT		low
  metric.reporters	A list of classes to use as metrics reporters. Implementing the MetricReporter interface allows plugging in classes that will be notified of new metric creation. The JmxReporter is always included to register JMX statistics.	list	""		low
  metrics.num.samples	The number of samples maintained to compute metrics.	int	2	[1,...]	low
  metrics.recording.level	The highest recording level for metrics.	string	INFO		low
  metrics.sample.window.ms	The window of time a metrics sample is computed over.	long	30000	[1,...]	low
  quota.window.num	The number of samples to retain in memory for client quotas	int	11	[1,...]	low
  quota.window.size.seconds	The time span of each sample for client quotas	int	1	[1,...]	low
  replication.quota.window.num	The number of samples to retain in memory for replication quotas	int	11	[1,...]	low
  replication.quota.window.size.seconds	The time span of each sample for replication quotas	int	1	[1,...]	low
  ssl.endpoint.identification.algorithm	The endpoint identification algorithm to validate server hostname using server certificate.	string	null		low
  ssl.secure.random.implementation	The SecureRandom PRNG implementation to use for SSL cryptography operations.	string	null		low
  transaction.abort.timed.out.transaction.cleanup.interval.ms	The interval at which to rollback transactions that have timed out	int	60000	[1,...]	low
  transaction.remove.expired.transaction.cleanup.interval.ms	The interval at which to remove transactions that have expired due to transactional.id.expiration.ms passing	int	3600000	[1,...]	low
  zookeeper.sync.time.ms	How far a ZK follower can be behind a ZK leader	int	2000		low

More details about broker configuration can be found in the scala class kafka.server.KafkaConfig.

Topic-level configuration Configurations pertinent to topics have both a global default as well an optional per-topic override. If no per-topic configuration is given the global default is used. The override can be set at topic creation time by giving one or more --config options. This example creates a topic named my-topic with a custom max message size and flush rate:

** > bin/kafka-topics.sh --zookeeper localhost:2181 --create --topic my-topic --partitions 1
        --replication-factor 1 --config max.message.bytes=64000 --config flush.messages=1**

Overrides can also be changed or set later using the alter topic command. This example updates the max message size for my-topic :

** > bin/kafka-topics.sh --zookeeper localhost:2181 --alter --topic my-topic
    --config max.message.bytes=128000**

To remove an override you can do

** > bin/kafka-topics.sh --zookeeper localhost:2181 --alter --topic my-topic
    --deleteConfig max.message.bytes**

Producer Configs

Below is the configuration of the Java producer:

For those interested in the legacy Scala producer configs, information can be found here.

Consumer Configs

We introduce both the old 0.8 consumer configs and the new consumer configs respectively below.

Old Consumer Configs

The essential old consumer configurations are the following:

• group.id
• zookeeper.connect

  Property	Default	Description
  group.id		A string that uniquely identifies the group of consumer processes to which this consumer belongs. By setting the same group id multiple processes indicate that they are all part of the same consumer group.
  zookeeper.connect		Specifies the ZooKeeper connection string in the form hostname:port where host and port are the host and port of a ZooKeeper server. To allow connecting through other ZooKeeper nodes when that ZooKeeper machine is down you can also specify multiple hosts in the form hostname1:port1,hostname2:port2,hostname3:port3. The server may also have a ZooKeeper chroot path as part of it’s ZooKeeper connection string which puts its data under some path in the global ZooKeeper namespace. If so the consumer should use the same chroot path in its connection string. For example to give a chroot path of /chroot/path you would give the connection string as hostname1:port1,hostname2:port2,hostname3:port3/chroot/path.
  consumer.id	null	Generated automatically if not set.
  socket.timeout.ms	30 * 1000	The socket timeout for network requests. The actual timeout set will be max.fetch.wait + socket.timeout.ms.
  socket.receive.buffer.bytes	64 * 1024	The socket receive buffer for network requests
  fetch.message.max.bytes	1024 * 1024	The number of byes of messages to attempt to fetch for each topic-partition in each fetch request. These bytes will be read into memory for each partition, so this helps control the memory used by the consumer. The fetch request size must be at least as large as the maximum message size the server allows or else it is possible for the producer to send messages larger than the consumer can fetch.
  num.consumer.fetchers	1	The number fetcher threads used to fetch data.
  auto.commit.enable	true	If true, periodically commit to ZooKeeper the offset of messages already fetched by the consumer. This committed offset will be used when the process fails as the position from which the new consumer will begin.
  auto.commit.interval.ms	60 * 1000	The frequency in ms that the consumer offsets are committed to zookeeper.
  queued.max.message.chunks	2	Max number of message chunks buffered for consumption. Each chunk can be up to fetch.message.max.bytes.
  rebalance.max.retries	4	When a new consumer joins a consumer group the set of consumers attempt to “rebalance” the load to assign partitions to each consumer. If the set of consumers changes while this assignment is taking place the rebalance will fail and retry. This setting controls the maximum number of attempts before giving up.
  fetch.min.bytes	1	The minimum amount of data the server should return for a fetch request. If insufficient data is available the request will wait for that much data to accumulate before answering the request.
  fetch.wait.max.ms	100	The maximum amount of time the server will block before answering the fetch request if there isn’t sufficient data to immediately satisfy fetch.min.bytes
  rebalance.backoff.ms	2000	Backoff time between retries during rebalance. If not set explicitly, the value in zookeeper.sync.time.ms is used.
  refresh.leader.backoff.ms	200	Backoff time to wait before trying to determine the leader of a partition that has just lost its leader.
  auto.offset.reset	largest	What to do when there is no initial offset in ZooKeeper or if an offset is out of range:

• smallest : automatically reset the offset to the smallest offset
• largest : automatically reset the offset to the largest offset
• anything else: throw exception to the consumer
  consumer.timeout.ms | -1 | Throw a timeout exception to the consumer if no message is available for consumption after the specified interval
  exclude.internal.topics | true | Whether messages from internal topics (such as offsets) should be exposed to the consumer.
  client.id | group id value | The client id is a user-specified string sent in each request to help trace calls. It should logically identify the application making the request.
  zookeeper.session.timeout.ms | 6000 | ZooKeeper session timeout. If the consumer fails to heartbeat to ZooKeeper for this period of time it is considered dead and a rebalance will occur.
  zookeeper.connection.timeout.ms | 6000 | The max time that the client waits while establishing a connection to zookeeper.
  zookeeper.sync.time.ms | 2000 | How far a ZK follower can be behind a ZK leader
  offsets.storage | zookeeper | Select where offsets should be stored (zookeeper or kafka).
  offsets.channel.backoff.ms | 1000 | The backoff period when reconnecting the offsets channel or retrying failed offset fetch/commit requests.
  offsets.channel.socket.timeout.ms | 10000 | Socket timeout when reading responses for offset fetch/commit requests. This timeout is also used for ConsumerMetadata requests that are used to query for the offset manager.
  offsets.commit.max.retries | 5 | Retry the offset commit up to this many times on failure. This retry count only applies to offset commits during shut-down. It does not apply to commits originating from the auto-commit thread. It also does not apply to attempts to query for the offset coordinator before committing offsets. i.e., if a consumer metadata request fails for any reason, it will be retried and that retry does not count toward this limit.
  dual.commit.enabled | true | If you are using “kafka” as offsets.storage, you can dual commit offsets to ZooKeeper (in addition to Kafka). This is required during migration from zookeeper-based offset storage to kafka-based offset storage. With respect to any given consumer group, it is safe to turn this off after all instances within that group have been migrated to the new version that commits offsets to the broker (instead of directly to ZooKeeper).
  partition.assignment.strategy | range | Select between the “range” or “roundrobin” strategy for assigning partitions to consumer streams.The round-robin partition assignor lays out all the available partitions and all the available consumer threads. It then proceeds to do a round-robin assignment from partition to consumer thread. If the subscriptions of all consumer instances are identical, then the partitions will be uniformly distributed. (i.e., the partition ownership counts will be within a delta of exactly one across all consumer threads.) Round-robin assignment is permitted only if: (a) Every topic has the same number of streams within a consumer instance (b) The set of subscribed topics is identical for every consumer instance within the group. Range partitioning works on a per-topic basis. For each topic, we lay out the available partitions in numeric order and the consumer threads in lexicographic order. We then divide the number of partitions by the total number of consumer streams (threads) to determine the number of partitions to assign to each consumer. If it does not evenly divide, then the first few consumers will have one extra partition.

More details about consumer configuration can be found in the scala class kafka.consumer.ConsumerConfig.

New Consumer Configs

Since 0.9.0.0 we have been working on a replacement for our existing simple and high-level consumers. The code is considered beta quality. Below is the configuration for the new consumer:

Kafka Connect Configs