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	Dynamic Update Mode
  zookeeper.connect	Zookeeper host string	string			high	read-only
  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	read-only
  advertised.listeners	Listeners to publish to ZooKeeper for clients to use, if different than the `listeners` config property. 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. Unlike `listeners` it is not valid to advertise the 0.0.0.0 meta-address.	string	null		high	per-broker
  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	read-only
  auto.create.topics.enable	Enable auto creation of topic on the server	boolean	true		high	read-only
  auto.leader.rebalance.enable	Enables auto leader balancing. A background thread checks and triggers leader balance if required at regular intervals	boolean	true		high	read-only
  background.threads	The number of threads to use for various background processing tasks	int	10	[1,...]	high	cluster-wide
  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	read-only
  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	cluster-wide
  delete.topic.enable	Enables delete topic. Delete topic through the admin tool will have no effect if this config is turned off	boolean	true		high	read-only
  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	read-only
  leader.imbalance.check.interval.seconds	The frequency with which the partition rebalance check is triggered by the controller	long	300		high	read-only
  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	read-only
  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	per-broker
  log.dir	The directory in which the log data is kept (supplemental for log.dirs property)	string	/tmp/kafka-logs		high	read-only
  log.dirs	The directories in which the log data is kept. If not set, the value in log.dir is used	string	null		high	read-only
  log.flush.interval.messages	The number of messages accumulated on a log partition before messages are flushed to disk	long	9223372036854775807	[1,...]	high	cluster-wide
  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	cluster-wide
  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	read-only
  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	read-only
  log.flush.start.offset.checkpoint.interval.ms	The frequency with which we update the persistent record of log start offset	int	60000	[0,...]	high	read-only
  log.retention.bytes	The maximum size of the log before deleting it	long	-1		high	cluster-wide
  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	read-only
  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	read-only
  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	cluster-wide
  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	read-only
  log.roll.jitter.hours	The maximum jitter to subtract from logRollTimeMillis (in hours), secondary to log.roll.jitter.ms property	int	0	[0,...]	high	read-only
  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	cluster-wide
  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	cluster-wide
  log.segment.bytes	The maximum size of a single log file	int	1073741824	[14,...]	high	cluster-wide
  log.segment.delete.delay.ms	The amount of time to wait before deleting a file from the filesystem	long	60000	[0,...]	high	cluster-wide
  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	cluster-wide
  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	cluster-wide
  num.io.threads	The number of threads that the server uses for processing requests, which may include disk I/O	int	8	[1,...]	high	cluster-wide
  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	cluster-wide
  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	cluster-wide
  num.replica.alter.log.dirs.threads	The number of threads that can move replicas between log directories, which may include disk I/O	int	null		high	read-only
  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	cluster-wide
  offset.metadata.max.bytes	The maximum size for a metadata entry associated with an offset commit	int	4096		high	read-only
  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	read-only
  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	read-only
  offsets.load.buffer.size	Batch size for reading from the offsets segments when loading offsets into the cache (soft-limit, overridden if records are too large).	int	5242880	[1,...]	high	read-only
  offsets.retention.check.interval.ms	Frequency at which to check for stale offsets	long	600000	[1,...]	high	read-only
  offsets.retention.minutes	Offsets older than this retention period will be discarded	int	10080	[1,...]	high	read-only
  offsets.topic.compression.codec	Compression codec for the offsets topic - compression may be used to achieve "atomic" commits	int	0		high	read-only
  offsets.topic.num.partitions	The number of partitions for the offset commit topic (should not change after deployment)	int	50	[1,...]	high	read-only
  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	read-only
  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	read-only
  port	DEPRECATED: only used when `listeners` is not set. Use `listeners` instead. the port to listen and accept connections on	int	9092		high	read-only
  queued.max.requests	The number of queued requests allowed before blocking the network threads	int	500	[1,...]	high	read-only
  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	read-only
  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	read-only
  replica.fetch.min.bytes	Minimum bytes expected for each fetch response. If not enough bytes, wait up to replicaMaxWaitTimeMs	int	1		high	read-only
  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	read-only
  replica.high.watermark.checkpoint.interval.ms	The frequency with which the high watermark is saved out to disk	long	5000		high	read-only
  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	read-only
  replica.socket.receive.buffer.bytes	The socket receive buffer for network requests	int	65536		high	read-only
  replica.socket.timeout.ms	The socket timeout for network requests. Its value should be at least replica.fetch.wait.max.ms	int	30000		high	read-only
  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	read-only
  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	read-only
  socket.request.max.bytes	The maximum number of bytes in a socket request	int	104857600	[1,...]	high	read-only
  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	read-only
  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	read-only
  transaction.state.log.load.buffer.size	Batch size for reading from the transaction log segments when loading producer ids and transactions into the cache (soft-limit, overridden if records are too large).	int	5242880	[1,...]	high	read-only
  transaction.state.log.min.isr	Overridden min.insync.replicas config for the transaction topic.	int	2	[1,...]	high	read-only
  transaction.state.log.num.partitions	The number of partitions for the transaction topic (should not change after deployment).	int	50	[1,...]	high	read-only
  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	read-only
  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	read-only
  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	read-only
  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	cluster-wide
  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	read-only
  zookeeper.max.in.flight.requests	The maximum number of unacknowledged requests the client will send to Zookeeper before blocking.	int	10	[1,...]	high	read-only
  zookeeper.session.timeout.ms	Zookeeper session timeout	int	6000		high	read-only
  zookeeper.set.acl	Set client to use secure ACLs	boolean	false		high	read-only
  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	read-only
  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	read-only
  connections.max.idle.ms	Idle connections timeout: the server socket processor threads close the connections that idle more than this	long	600000		medium	read-only
  controlled.shutdown.enable	Enable controlled shutdown of the server	boolean	true		medium	read-only
  controlled.shutdown.max.retries	Controlled shutdown can fail for multiple reasons. This determines the number of retries when such failure happens	int	3		medium	read-only
  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	read-only
  controller.socket.timeout.ms	The socket timeout for controller-to-broker channels	int	30000		medium	read-only
  default.replication.factor	default replication factors for automatically created topics	int	1		medium	read-only
  delegation.token.expiry.time.ms	The token validity time in seconds before the token needs to be renewed. Default value 1 day.	long	86400000	[1,...]	medium	read-only
  delegation.token.master.key	Master/secret key to generate and verify delegation tokens. Same key must be configured across all the brokers. If the key is not set or set to empty string, brokers will disable the delegation token support.	password	null		medium	read-only
  delegation.token.max.lifetime.ms	The token has a maximum lifetime beyond which it cannot be renewed anymore. Default value 7 days.	long	604800000	[1,...]	medium	read-only
  delete.records.purgatory.purge.interval.requests	The purge interval (in number of requests) of the delete records request purgatory	int	1		medium	read-only
  fetch.purgatory.purge.interval.requests	The purge interval (in number of requests) of the fetch request purgatory	int	1000		medium	read-only
  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	read-only
  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	read-only
  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	read-only
  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	read-only
  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	2.0-IV1		medium	read-only
  log.cleaner.backoff.ms	The amount of time to sleep when there are no logs to clean	long	15000	[0,...]	medium	cluster-wide
  log.cleaner.dedupe.buffer.size	The total memory used for log deduplication across all cleaner threads	long	134217728		medium	cluster-wide
  log.cleaner.delete.retention.ms	How long are delete records retained?	long	86400000		medium	cluster-wide
  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	read-only
  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	cluster-wide
  log.cleaner.io.buffer.size	The total memory used for log cleaner I/O buffers across all cleaner threads	int	524288	[0,...]	medium	cluster-wide
  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	cluster-wide
  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	cluster-wide
  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	cluster-wide
  log.cleaner.threads	The number of background threads to use for log cleaning	int	1	[0,...]	medium	cluster-wide
  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	cluster-wide
  log.index.interval.bytes	The interval with which we add an entry to the offset index	int	4096	[0,...]	medium	cluster-wide
  log.index.size.max.bytes	The maximum size in bytes of the offset index	int	10485760	[4,...]	medium	cluster-wide
  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	2.0-IV1		medium	read-only
  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	cluster-wide
  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	cluster-wide
  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	cluster-wide
  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	read-only
  max.connections.per.ip	The maximum number of connections we allow from each ip address. This can be set to 0 if there are overrides configured using max.connections.per.ip.overrides property	int	2147483647	[0,...]	medium	read-only
  max.connections.per.ip.overrides	A comma-separated list of per-ip or hostname overrides to the default maximum number of connections. An example value is "hostName:100,127.0.0.1:200"	string	""		medium	read-only
  max.incremental.fetch.session.cache.slots	The maximum number of incremental fetch sessions that we will maintain.	int	1000	[0,...]	medium	read-only
  num.partitions	The default number of log partitions per topic	int	1	[1,...]	medium	read-only
  password.encoder.old.secret	The old secret that was used for encoding dynamically configured passwords. This is required only when the secret is updated. If specified, all dynamically encoded passwords are decoded using this old secret and re-encoded using password.encoder.secret when broker starts up.	password	null		medium	read-only
  password.encoder.secret	The secret used for encoding dynamically configured passwords for this broker.	password	null		medium	read-only
  principal.builder.class	The fully qualified name of a class that implements the KafkaPrincipalBuilder interface, which is used to build the KafkaPrincipal object used during authorization. This config also supports the deprecated PrincipalBuilder interface which was previously used for client authentication over SSL. If no principal builder is defined, the default behavior depends on the security protocol in use. For SSL authentication, the principal name will be the distinguished name from the client certificate if one is provided; otherwise, if client authentication is not required, the principal name will be ANONYMOUS. For SASL authentication, the principal will be derived using the rules defined by sasl.kerberos.principal.to.local.rules if GSSAPI is in use, and the SASL authentication ID for other mechanisms. For PLAINTEXT, the principal will be ANONYMOUS.	class	null		medium	per-broker
  producer.purgatory.purge.interval.requests	The purge interval (in number of requests) of the producer request purgatory	int	1000		medium	read-only
  queued.max.request.bytes	The number of queued bytes allowed before no more requests are read	long	-1		medium	read-only
  replica.fetch.backoff.ms	The amount of time to sleep when fetch partition error occurs.	int	1000	[0,...]	medium	read-only
  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	read-only
  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	read-only
  reserved.broker.max.id	Max number that can be used for a broker.id	int	1000	[0,...]	medium	read-only
  sasl.client.callback.handler.class	The fully qualified name of a SASL client callback handler class that implements the AuthenticateCallbackHandler interface.	class	null		medium	read-only
  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	per-broker
  sasl.jaas.config	JAAS login context parameters for SASL connections in the format used by JAAS configuration files. JAAS configuration file format is described here. The format for the value is: 'loginModuleClass controlFlag (optionName=optionValue)*;'. For brokers, the config must be prefixed with listener prefix and SASL mechanism name in lower-case. For example, listener.name.sasl_ssl.scram-sha-256.sasl.jaas.config=com.example.ScramLoginModule required;	password	null		medium	per-broker
  sasl.kerberos.kinit.cmd	Kerberos kinit command path.	string	/usr/bin/kinit		medium	per-broker
  sasl.kerberos.min.time.before.relogin	Login thread sleep time between refresh attempts.	long	60000		medium	per-broker
  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. Note that this configuration is ignored if an extension of KafkaPrincipalBuilder is provided by the principal.builder.class configuration.	list	DEFAULT		medium	per-broker
  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	per-broker
  sasl.kerberos.ticket.renew.jitter	Percentage of random jitter added to the renewal time.	double	0.05		medium	per-broker
  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	per-broker
  sasl.login.callback.handler.class	The fully qualified name of a SASL login callback handler class that implements the AuthenticateCallbackHandler interface. For brokers, login callback handler config must be prefixed with listener prefix and SASL mechanism name in lower-case. For example, listener.name.sasl_ssl.scram-sha-256.sasl.login.callback.handler.class=com.example.CustomScramLoginCallbackHandler	class	null		medium	read-only
  sasl.login.class	The fully qualified name of a class that implements the Login interface. For brokers, login config must be prefixed with listener prefix and SASL mechanism name in lower-case. For example, listener.name.sasl_ssl.scram-sha-256.sasl.login.class=com.example.CustomScramLogin	class	null		medium	read-only
  sasl.login.refresh.buffer.seconds	The amount of buffer time before credential expiration to maintain when refreshing a credential, in seconds. If a refresh would otherwise occur closer to expiration than the number of buffer seconds then the refresh will be moved up to maintain as much of the buffer time as possible. Legal values are between 0 and 3600 (1 hour); a default value of 300 (5 minutes) is used if no value is specified. This value and sasl.login.refresh.min.period.seconds are both ignored if their sum exceeds the remaining lifetime of a credential. Currently applies only to OAUTHBEARER.	short	300		medium	per-broker
  sasl.login.refresh.min.period.seconds	The desired minimum time for the login refresh thread to wait before refreshing a credential, in seconds. Legal values are between 0 and 900 (15 minutes); a default value of 60 (1 minute) is used if no value is specified. This value and sasl.login.refresh.buffer.seconds are both ignored if their sum exceeds the remaining lifetime of a credential. Currently applies only to OAUTHBEARER.	short	60		medium	per-broker
  sasl.login.refresh.window.factor	Login refresh thread will sleep until the specified window factor relative to the credential's lifetime has been reached, at which time it will try to refresh the credential. Legal values are between 0.5 (50%) and 1.0 (100%) inclusive; a default value of 0.8 (80%) is used if no value is specified. Currently applies only to OAUTHBEARER.	double	0.8		medium	per-broker
  sasl.login.refresh.window.jitter	The maximum amount of random jitter relative to the credential's lifetime that is added to the login refresh thread's sleep time. Legal values are between 0 and 0.25 (25%) inclusive; a default value of 0.05 (5%) is used if no value is specified. Currently applies only to OAUTHBEARER.	double	0.05		medium	per-broker
  sasl.mechanism.inter.broker.protocol	SASL mechanism used for inter-broker communication. Default is GSSAPI.	string	GSSAPI		medium	per-broker
  sasl.server.callback.handler.class	The fully qualified name of a SASL server callback handler class that implements the AuthenticateCallbackHandler interface. Server callback handlers must be prefixed with listener prefix and SASL mechanism name in lower-case. For example, listener.name.sasl_ssl.plain.sasl.server.callback.handler.class=com.example.CustomPlainCallbackHandler.	class	null		medium	read-only
  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	read-only
  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	""		medium	per-broker
  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	per-broker
  ssl.enabled.protocols	The list of protocols enabled for SSL connections.	list	TLSv1.2,TLSv1.1,TLSv1		medium	per-broker
  ssl.key.password	The password of the private key in the key store file. This is optional for client.	password	null		medium	per-broker
  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	per-broker
  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	per-broker
  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	per-broker
  ssl.keystore.type	The file format of the key store file. This is optional for client.	string	JKS		medium	per-broker
  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	per-broker
  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	per-broker
  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	per-broker
  ssl.truststore.location	The location of the trust store file.	string	null		medium	per-broker
  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	per-broker
  ssl.truststore.type	The file format of the trust store file.	string	JKS		medium	per-broker
  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	read-only
  alter.log.dirs.replication.quota.window.num	The number of samples to retain in memory for alter log dirs replication quotas	int	11	[1,...]	low	read-only
  alter.log.dirs.replication.quota.window.size.seconds	The time span of each sample for alter log dirs replication quotas	int	1	[1,...]	low	read-only
  authorizer.class.name	The authorizer class that should be used for authorization	string	""		low	read-only
  client.quota.callback.class	The fully qualified name of a class that implements the ClientQuotaCallback interface, which is used to determine quota limits applied to client requests. By default, , or quotas stored in ZooKeeper are applied. For any given request, the most specific quota that matches the user principal of the session and the client-id of the request is applied.	class	null		low	read-only
  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	read-only
  delegation.token.expiry.check.interval.ms	Scan interval to remove expired delegation tokens.	long	3600000	[1,...]	low	read-only
  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, internal and external traffic can be separated even if SSL is required for both. Concretely, the user 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. Different security (SSL and SASL) settings can be configured for each listener by adding a normalised prefix (the listener name is lowercased) to the config name. For example, to set a different keystore for the INTERNAL listener, a config with name `listener.name.internal.ssl.keystore.location` would be set. If the config for the listener name is not set, the config will fallback to the generic config (i.e. `ssl.keystore.location`).	string	PLAINTEXT:PLAINTEXT,SSL:SSL,SASL_PLAINTEXT:SASL_PLAINTEXT,SASL_SSL:SASL_SSL		low	per-broker
  log.message.downconversion.enable	This configuration controls whether down-conversion of message formats is enabled to satisfy consume requests. When set to false, broker will not perform down-conversion for consumers expecting an older message format. The broker responds with UNSUPPORTED_VERSION error for consume requests from such older clients. This configurationdoes not apply to any message format conversion that might be required for replication to followers.	boolean	true		low	cluster-wide
  metric.reporters	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.	list	""		low	cluster-wide
  metrics.num.samples	The number of samples maintained to compute metrics.	int	2	[1,...]	low	read-only
  metrics.recording.level	The highest recording level for metrics.	string	INFO		low	read-only
  metrics.sample.window.ms	The window of time a metrics sample is computed over.	long	30000	[1,...]	low	read-only
  password.encoder.cipher.algorithm	The Cipher algorithm used for encoding dynamically configured passwords.	string	AES/CBC/PKCS5Padding		low	read-only
  password.encoder.iterations	The iteration count used for encoding dynamically configured passwords.	int	4096	[1024,...]	low	read-only
  password.encoder.key.length	The key length used for encoding dynamically configured passwords.	int	128	[8,...]	low	read-only
  password.encoder.keyfactory.algorithm	The SecretKeyFactory algorithm used for encoding dynamically configured passwords. Default is PBKDF2WithHmacSHA512 if available and PBKDF2WithHmacSHA1 otherwise.	string	null		low	read-only
  quota.window.num	The number of samples to retain in memory for client quotas	int	11	[1,...]	low	read-only
  quota.window.size.seconds	The time span of each sample for client quotas	int	1	[1,...]	low	read-only
  replication.quota.window.num	The number of samples to retain in memory for replication quotas	int	11	[1,...]	low	read-only
  replication.quota.window.size.seconds	The time span of each sample for replication quotas	int	1	[1,...]	low	read-only
  ssl.endpoint.identification.algorithm	The endpoint identification algorithm to validate server hostname using server certificate.	string	https		low	per-broker
  ssl.secure.random.implementation	The SecureRandom PRNG implementation to use for SSL cryptography operations.	string	null		low	per-broker
  transaction.abort.timed.out.transaction.cleanup.interval.ms	The interval at which to rollback transactions that have timed out	int	60000	[1,...]	low	read-only
  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	read-only
  zookeeper.sync.time.ms	How far a ZK follower can be behind a ZK leader	int	2000		low	read-only

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

Updating Broker Configs

From Kafka version 1.1 onwards, some of the broker configs can be updated without restarting the broker. See the Dynamic Update Mode column in Broker Configs for the update mode of each broker config.

• read-only: Requires a broker restart for update
• per-broker: May be updated dynamically for each broker
• cluster-wide: May be updated dynamically as a cluster-wide default. May also be updated as a per-broker value for testing.

To alter the current broker configs for broker id 0 (for example, the number of log cleaner threads):

  > bin/kafka-configs.sh --bootstrap-server localhost:9092 --entity-type brokers --entity-name 0 --alter --add-config log.cleaner.threads=2

To describe the current dynamic broker configs for broker id 0:

  > bin/kafka-configs.sh --bootstrap-server localhost:9092 --entity-type brokers --entity-name 0 --describe

To delete a config override and revert to the statically configured or default value for broker id 0 (for example, the number of log cleaner threads):

  > bin/kafka-configs.sh --bootstrap-server localhost:9092 --entity-type brokers --entity-name 0 --alter --delete-config log.cleaner.threads

Some configs may be configured as a cluster-wide default to maintain consistent values across the whole cluster. All brokers in the cluster will process the cluster default update. For example, to update log cleaner threads on all brokers:

  > bin/kafka-configs.sh --bootstrap-server localhost:9092 --entity-type brokers --entity-default --alter --add-config log.cleaner.threads=2

To describe the currently configured dynamic cluster-wide default configs:

  > bin/kafka-configs.sh --bootstrap-server localhost:9092 --entity-type brokers --entity-default --describe

All configs that are configurable at cluster level may also be configured at per-broker level (e.g. for testing). If a config value is defined at different levels, the following order of precedence is used:

• Dynamic per-broker config stored in ZooKeeper
• Dynamic cluster-wide default config stored in ZooKeeper
• Static broker config from server.properties
• Kafka default, see broker configs

Updating Password Configs Dynamically

Password config values that are dynamically updated are encrypted before storing in ZooKeeper. The broker config password.encoder.secret must be configured in server.properties to enable dynamic update of password configs. The secret may be different on different brokers.

The secret used for password encoding may be rotated with a rolling restart of brokers. The old secret used for encoding passwords currently in ZooKeeper must be provided in the static broker config password.encoder.old.secret and the new secret must be provided in password.encoder.secret. All dynamic password configs stored in ZooKeeper will be re-encoded with the new secret when the broker starts up.

In Kafka 1.1.x, all dynamically updated password configs must be provided in every alter request when updating configs using kafka-configs.sh even if the password config is not being altered. This constraint will be removed in a future release.

Updating Password Configs in ZooKeeper Before Starting Brokers

From Kafka 2.0.0 onwards, kafka-configs.sh enables dynamic broker configs to be updated using ZooKeeper before starting brokers for bootstrapping. This enables all password configs to be stored in encrypted form, avoiding the need for clear passwords in server.properties. The broker config password.encoder.secret must also be specified if any password configs are included in the alter command. Additional encryption parameters may also be specified. Password encoder configs will not be persisted in ZooKeeper. For example, to store SSL key password for listener INTERNAL on broker 0:

  > bin/kafka-configs.sh --zookeeper localhost:2181 --entity-type brokers --entity-name 0 --alter --add-config
    'listener.name.internal.ssl.key.password=key-password,password.encoder.secret=secret,password.encoder.iterations=8192'

The configuration listener.name.internal.ssl.key.password will be persisted in ZooKeeper in encrypted form using the provided encoder configs. The encoder secret and iterations are not persisted in ZooKeeper.

Updating SSL Keystore of an Existing Listener

Brokers may be configured with SSL keystores with short validity periods to reduce the risk of compromised certificates. Keystores may be updated dynamically without restarting the broker. The config name must be prefixed with the listener prefix listener.name.{listenerName}. so that only the keystore config of a specific listener is updated. The following configs may be updated in a single alter request at per-broker level:

• ssl.keystore.type
• ssl.keystore.location
• ssl.keystore.password
• ssl.key.password

If the listener is the inter-broker listener, the update is allowed only if the new keystore is trusted by the truststore configured for that listener. For other listeners, no trust validation is performed on the keystore by the broker. Certificates must be signed by the same certificate authority that signed the old certificate to avoid any client authentication failures.

Updating SSL Truststore of an Existing Listener

Broker truststores may be updated dynamically without restarting the broker to add or remove certificates. Updated truststore will be used to authenticate new client connections. The config name must be prefixed with the listener prefix listener.name.{listenerName}. so that only the truststore config of a specific listener is updated. The following configs may be updated in a single alter request at per-broker level:

• ssl.truststore.type
• ssl.truststore.location
• ssl.truststore.password

If the listener is the inter-broker listener, the update is allowed only if the existing keystore for that listener is trusted by the new truststore. For other listeners, no trust validation is performed by the broker before the update. Removal of CA certificates used to sign client certificates from the new truststore can lead to client authentication failures.

Updating Default Topic Configuration

Default topic configuration options used by brokers may be updated without broker restart. The configs are applied to topics without a topic config override for the equivalent per-topic config. One or more of these configs may be overridden at cluster-default level used by all brokers.

• log.segment.bytes
• log.roll.ms
• log.roll.hours
• log.roll.jitter.ms
• log.roll.jitter.hours
• log.index.size.max.bytes
• log.flush.interval.messages
• log.flush.interval.ms
• log.retention.bytes
• log.retention.ms
• log.retention.minutes
• log.retention.hours
• log.index.interval.bytes
• log.cleaner.delete.retention.ms
• log.cleaner.min.compaction.lag.ms
• log.cleaner.min.cleanable.ratio
• log.cleanup.policy
• log.segment.delete.delay.ms
• unclean.leader.election.enable
• min.insync.replicas
• max.message.bytes
• compression.type
• log.preallocate
• log.message.timestamp.type
• log.message.timestamp.difference.max.ms

From Kafka version 2.0.0 onwards, unclean leader election is automatically enabled by the controller when the config unclean.leader.election.enable is dynamically updated. In Kafka version 1.1.x, changes to unclean.leader.election.enable take effect only when a new controller is elected. Controller re-election may be forced by running:

  > bin/zookeeper-shell.sh localhost
  rmr /controller

Updating Log Cleaner Configs

Log cleaner configs may be updated dynamically at cluster-default level used by all brokers. The changes take effect on the next iteration of log cleaning. One or more of these configs may be updated:

• log.cleaner.threads
• log.cleaner.io.max.bytes.per.second
• log.cleaner.dedupe.buffer.size
• log.cleaner.io.buffer.size
• log.cleaner.io.buffer.load.factor
• log.cleaner.backoff.ms

Updating Thread Configs

The size of various thread pools used by the broker may be updated dynamically at cluster-default level used by all brokers. Updates are restricted to the range currentSize / 2 to currentSize * 2 to ensure that config updates are handled gracefully.

• num.network.threads
• num.io.threads
• num.replica.fetchers
• num.recovery.threads.per.data.dir
• log.cleaner.threads
• background.threads

Adding and Removing Listeners

Listeners may be added or removed dynamically. When a new listener is added, security configs of the listener must be provided as listener configs with the listener prefix listener.name.{listenerName}.. If the new listener uses SASL, the JAAS configuration of the listener must be provided using the JAAS configuration property sasl.jaas.config with the listener and mechanism prefix. See JAAS configuration for Kafka brokers for details.

In Kafka version 1.1.x, the listener used by the inter-broker listener may not be updated dynamically. To update the inter-broker listener to a new listener, the new listener may be added on all brokers without restarting the broker. A rolling restart is then required to update inter.broker.listener.name.

In addition to all the security configs of new listeners, the following configs may be updated dynamically at per-broker level:

• listeners
• advertised.listeners
• listener.security.protocol.map

Inter-broker listener must be configured using the static broker configuration inter.broker.listener.name or inter.broker.security.protocol.