Appendix E. Admin Client configuration parameters

NameDescriptionTypeDefaultValid ValuesImportance

bootstrap.servers

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).

list

  

high

ssl.key.password

The password of the private key in the key store file. This is optional for client.

password

null

 

high

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

 

high

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

 

high

ssl.truststore.location

The location of the trust store file.

string

null

 

high

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

 

high

client.id

An id string to pass to the server when making requests. The purpose of this is to be able to track the source of requests beyond just ip/port by allowing a logical application name to be included in server-side request logging.

string

""

 

medium

connections.max.idle.ms

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

long

300000

 

medium

receive.buffer.bytes

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.

int

65536

[-1,…​]

medium

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

120000

[0,…​]

medium

sasl.client.callback.handler.class

The fully qualified name of a SASL client callback handler class that implements the AuthenticateCallbackHandler interface.

class

null

 

medium

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

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.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

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

sasl.mechanism

SASL mechanism used for client connections. This may be any mechanism for which a security provider is available. GSSAPI is the default mechanism.

string

GSSAPI

 

medium

security.protocol

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

string

PLAINTEXT

 

medium

send.buffer.bytes

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.

int

131072

[-1,…​]

medium

ssl.enabled.protocols

The list of protocols enabled for SSL connections.

list

TLSv1.2,TLSv1.1,TLSv1

 

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.truststore.type

The file format of the trust store file.

string

JKS

 

medium

metadata.max.age.ms

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.

long

300000

[0,…​]

low

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

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

[INFO, DEBUG]

low

metrics.sample.window.ms

The window of time a metrics sample is computed over.

long

30000

[0,…​]

low

reconnect.backoff.max.ms

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.

long

1000

[0,…​]

low

reconnect.backoff.ms

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.

long

50

[0,…​]

low

retries

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

int

5

[0,…​]

low

retry.backoff.ms

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

long

100

[0,…​]

low

sasl.kerberos.kinit.cmd

Kerberos kinit command path.

string

/usr/bin/kinit

 

low

sasl.kerberos.min.time.before.relogin

Login thread sleep time between refresh attempts.

long

60000

 

low

sasl.kerberos.ticket.renew.jitter

Percentage of random jitter added to the renewal time.

double

0.05

 

low

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

 

low

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

[0,…​,3600]

low

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

[0,…​,900]

low

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

[0.5,…​,1.0]

low

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

[0.0,…​,0.25]

low

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

 

low

ssl.endpoint.identification.algorithm

The endpoint identification algorithm to validate server hostname using server certificate.

string

https

 

low

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

 

low

ssl.secure.random.implementation

The SecureRandom PRNG implementation to use for SSL cryptography operations.

string

null

 

low

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

 

low