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 . 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).

ssl.key.password

The password of the private key in the key store file orthe PEM key specified in `ssl.keystore.key’. This is required for clients only if two-way authentication is configured.

ssl.keystore.certificate.chain

Certificate chain in the format specified by ‘ssl.keystore.type’. Default SSL engine factory supports only PEM format with a list of X.509 certificates

ssl.keystore.key

Private key in the format specified by ‘ssl.keystore.type’. Default SSL engine factory supports only PEM format with PKCS#8 keys. If the key is encrypted, key password must be specified using ‘ssl.key.password’

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.

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. Key store password is not supported for PEM format.

ssl.truststore.certificates

Trusted certificates in the format specified by ‘ssl.truststore.type’. Default SSL engine factory supports only PEM format with X.509 certificates.

ssl.truststore.location

The location of the trust store file.

ssl.truststore.password

The password for the trust store file. If a password is not set, trust store file configured will still be used, but integrity checking is disabled. Trust store password is not supported for PEM format.

client.dns.lookup

Controls how the client uses DNS lookups. If set to use_all_dns_ips, connect to each returned IP address in sequence until a successful connection is established. After a disconnection, the next IP is used. Once all IPs have been used once, the client resolves the IP(s) from the hostname again (both the JVM and the OS cache DNS name lookups, however). If set to , resolve each bootstrap address into a list of canonical names. After the bootstrap phase, this behaves the same as use_all_dns_ips.

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.

connections.max.idle.ms

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

default.api.timeout.ms

Specifies the timeout (in milliseconds) for client APIs. This configuration is used as the default timeout for all client operations that do not specify a parameter.

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.

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.

sasl.client.callback.handler.class

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

sasl.jaas.config

JAAS login context parameters for SASL connections in the format used by JAAS configuration files. JAAS configuration file format is described . 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;

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

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

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

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

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.

The maximum amount of time the client will wait for the socket connection to be established. The connection setup timeout will increase exponentially for each consecutive connection failure up to this maximum. To avoid connection storms, a randomization factor of 0.2 will be applied to the timeout resulting in a random range between 20% below and 20% above the computed value.

The amount of time the client will wait for the socket connection to be established. If the connection is not built before the timeout elapses, clients will close the socket channel.

The list of protocols enabled for SSL connections. The default is ‘TLSv1.2,TLSv1.3’ when running with Java 11 or newer, ‘TLSv1.2’ otherwise. With the default value for Java 11, clients and servers will prefer TLSv1.3 if both support it and fallback to TLSv1.2 otherwise (assuming both support at least TLSv1.2). This default should be fine for most cases. Also see the config documentation for `ssl.protocol`.

The file format of the key store file. This is optional for client.

The SSL protocol used to generate the SSLContext. The default is ‘TLSv1.3’ when running with Java 11 or newer, ‘TLSv1.2’ otherwise. This value should be fine for most use cases. Allowed values in recent JVMs are ‘TLSv1.2’ and ‘TLSv1.3’. ‘TLS’, ‘TLSv1.1’, ‘SSL’, ‘SSLv2’ and ‘SSLv3’ may be supported in older JVMs, but their usage is discouraged due to known security vulnerabilities. With the default value for this config and ‘ssl.enabled.protocols’, clients will downgrade to ‘TLSv1.2’ if the server does not support ‘TLSv1.3’. If this config is set to ‘TLSv1.2’, clients will not use ‘TLSv1.3’ even if it is one of the values in ssl.enabled.protocols and the server only supports ‘TLSv1.3’.

The name of the security provider used for SSL connections. Default value is the default security provider of the JVM.

The file format of the trust store file.

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.

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

The number of samples maintained to compute metrics.

The highest recording level for metrics.

The window of time a metrics sample is computed over.

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.

Setting a value greater than zero will cause the client to resend any request that fails with a potentially transient error. It is recommended to set the value to either zero or `MAX_VALUE` and use corresponding timeout parameters to control how long a client should retry a request.

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.

Kerberos kinit command path.

Login thread sleep time between refresh attempts.

Percentage of random jitter added to the renewal time.

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.

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.

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.

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.

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.

A list of configurable creator classes each returning a provider implementing security algorithms. These classes should implement the org.apache.kafka.common.security.auth.SecurityProviderCreator interface.

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.

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

The class of type org.apache.kafka.common.security.auth.SslEngineFactory to provide SSLEngine objects. Default value is org.apache.kafka.common.security.ssl.DefaultSslEngineFactory

The algorithm used by key manager factory for SSL connections. Default value is the key manager factory algorithm configured for the Java Virtual Machine.

The SecureRandom PRNG implementation to use for SSL cryptography operations.