librdkafka
The Apache Kafka C/C++ client library
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CONFIGURATION.md File Reference

Detailed Description

Global configuration properties

Property C/P Range Default Description
builtin.features * gzip, snappy, ssl, sasl, regex, lz4 Indicates the builtin features for this build of librdkafka. An application can either query this value or attempt to set it with its list of required features to check for library support.
*Type: CSV flags*
client.id * rdkafka Client identifier.
*Type: string*
metadata.broker.list * Initial list of brokers as a CSV list of broker host or host:port. The application may also use rd_kafka_brokers_add() to add brokers during runtime.
*Type: string*
bootstrap.servers * Alias for metadata.broker.list
message.max.bytes * 1000 .. 1000000000 1000000 Maximum transmit message size.
*Type: integer*
message.copy.max.bytes * 0 .. 1000000000 65535 Maximum size for message to be copied to buffer. Messages larger than this will be passed by reference (zero-copy) at the expense of larger iovecs.
*Type: integer*
receive.message.max.bytes * 1000 .. 1000000000 100000000 Maximum receive message size. This is a safety precaution to avoid memory exhaustion in case of protocol hickups. The value should be at least fetch.message.max.bytes * number of partitions consumed from + messaging overhead (e.g. 200000 bytes).
*Type: integer*
max.in.flight.requests.per.connection * 1 .. 1000000 1000000 Maximum number of in-flight requests the client will send. This setting applies per broker connection.
*Type: integer*
max.in.flight * Alias for max.in.flight.requests.per.connection
metadata.request.timeout.ms * 10 .. 900000 60000 Non-topic request timeout in milliseconds. This is for metadata requests, etc.
*Type: integer*
topic.metadata.refresh.interval.ms * -1 .. 3600000 300000 Topic metadata refresh interval in milliseconds. The metadata is automatically refreshed on error and connect. Use -1 to disable the intervalled refresh.
*Type: integer*
metadata.max.age.ms * 1 .. 86400000 -1 Metadata cache max age. Defaults to metadata.refresh.interval.ms * 3
*Type: integer*
topic.metadata.refresh.fast.interval.ms * 1 .. 60000 250 When a topic looses its leader a new metadata request will be enqueued with this initial interval, exponentially increasing until the topic metadata has been refreshed. This is used to recover quickly from transitioning leader brokers.
*Type: integer*
topic.metadata.refresh.fast.cnt * 0 .. 1000 10 Deprecated: No longer used.
*Type: integer*
topic.metadata.refresh.sparse * true, false true Sparse metadata requests (consumes less network bandwidth)
*Type: boolean*
topic.blacklist * Topic blacklist, a comma-separated list of regular expressions for matching topic names that should be ignored in broker metadata information as if the topics did not exist.
*Type: pattern list*
debug * generic, broker, topic, metadata, queue, msg, protocol, cgrp, security, fetch, feature, all A comma-separated list of debug contexts to enable. Debugging the Producer: broker,topic,msg. Consumer: cgrp,topic,fetch
*Type: CSV flags*
socket.timeout.ms * 10 .. 300000 60000 Timeout for network requests.
*Type: integer*
socket.blocking.max.ms * 1 .. 60000 1000 Maximum time a broker socket operation may block. A lower value improves responsiveness at the expense of slightly higher CPU usage. Deprecated
*Type: integer*
socket.send.buffer.bytes * 0 .. 100000000 0 Broker socket send buffer size. System default is used if 0.
*Type: integer*
socket.receive.buffer.bytes * 0 .. 100000000 0 Broker socket receive buffer size. System default is used if 0.
*Type: integer*
socket.keepalive.enable * true, false false Enable TCP keep-alives (SO_KEEPALIVE) on broker sockets
*Type: boolean*
socket.nagle.disable * true, false false Disable the Nagle algorithm (TCP_NODELAY).
*Type: boolean*
socket.max.fails * 0 .. 1000000 3 Disconnect from broker when this number of send failures (e.g., timed out requests) is reached. Disable with 0. NOTE: The connection is automatically re-established.
*Type: integer*
broker.address.ttl * 0 .. 86400000 1000 How long to cache the broker address resolving results (milliseconds).
*Type: integer*
broker.address.family * any, v4, v6 any Allowed broker IP address families: any, v4, v6
*Type: enum value*
reconnect.backoff.jitter.ms * 0 .. 3600000 500 Throttle broker reconnection attempts by this value +-50%.
*Type: integer*
statistics.interval.ms * 0 .. 86400000 0 librdkafka statistics emit interval. The application also needs to register a stats callback using rd_kafka_conf_set_stats_cb(). The granularity is 1000ms. A value of 0 disables statistics.
*Type: integer*
enabled_events * 0 .. 2147483647 0 See rd_kafka_conf_set_events()
*Type: integer*
error_cb * Error callback (set with rd_kafka_conf_set_error_cb())
*Type: pointer*
throttle_cb * Throttle callback (set with rd_kafka_conf_set_throttle_cb())
*Type: pointer*
stats_cb * Statistics callback (set with rd_kafka_conf_set_stats_cb())
*Type: pointer*
log_cb * Log callback (set with rd_kafka_conf_set_log_cb())
*Type: pointer*
log_level * 0 .. 7 6 Logging level (syslog(3) levels)
*Type: integer*
log.queue * true, false false Disable spontaneous log_cb from internal librdkafka threads, instead enqueue log messages on queue set with rd_kafka_set_log_queue() and serve log callbacks or events through the standard poll APIs. NOTE: Log messages will linger in a temporary queue until the log queue has been set.
*Type: boolean*
log.thread.name * true, false true Print internal thread name in log messages (useful for debugging librdkafka internals)
*Type: boolean*
log.connection.close * true, false true Log broker disconnects. It might be useful to turn this off when interacting with 0.9 brokers with an aggressive connection.max.idle.ms value.
*Type: boolean*
socket_cb * Socket creation callback to provide race-free CLOEXEC
*Type: pointer*
connect_cb * Socket connect callback
*Type: pointer*
closesocket_cb * Socket close callback
*Type: pointer*
open_cb * File open callback to provide race-free CLOEXEC
*Type: pointer*
opaque * Application opaque (set with rd_kafka_conf_set_opaque())
*Type: pointer*
default_topic_conf * Default topic configuration for automatically subscribed topics
*Type: pointer*
internal.termination.signal * 0 .. 128 0 Signal that librdkafka will use to quickly terminate on rd_kafka_destroy(). If this signal is not set then there will be a delay before rd_kafka_wait_destroyed() returns true as internal threads are timing out their system calls. If this signal is set however the delay will be minimal. The application should mask this signal as an internal signal handler is installed.
*Type: integer*
api.version.request * true, false false Request broker's supported API versions to adjust functionality to available protocol features. If set to false the fallback version broker.version.fallback will be used. NOTE: Depends on broker version >=0.10.0. If the request is not supported by (an older) broker the broker.version.fallback fallback is used.
*Type: boolean*
api.version.fallback.ms * 0 .. 604800000 1200000 Dictates how long the broker.version.fallback fallback is used in the case the ApiVersionRequest fails. NOTE: The ApiVersionRequest is only issued when a new connection to the broker is made (such as after an upgrade).
*Type: integer*
broker.version.fallback * 0.9.0 Older broker versions (<0.10.0) provides no way for a client to query for supported protocol features (ApiVersionRequest, see api.version.request) making it impossible for the client to know what features it may use. As a workaround a user may set this property to the expected broker version and the client will automatically adjust its feature set accordingly if the ApiVersionRequest fails (or is disabled). The fallback broker version will be used for api.version.fallback.ms. Valid values are: 0.9.0, 0.8.2, 0.8.1, 0.8.0.
*Type: string*
security.protocol * plaintext, ssl, sasl_plaintext, sasl_ssl plaintext Protocol used to communicate with brokers.
*Type: enum value*
ssl.cipher.suites * A cipher suite 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. See manual page for ciphers(1) and `SSL_CTX_set_cipher_list(3).
*Type: string*
ssl.key.location * Path to client's private key (PEM) used for authentication.
*Type: string*
ssl.key.password * Private key passphrase
*Type: string*
ssl.certificate.location * Path to client's public key (PEM) used for authentication.
*Type: string*
ssl.ca.location * File or directory path to CA certificate(s) for verifying the broker's key.
*Type: string*
ssl.crl.location * Path to CRL for verifying broker's certificate validity.
*Type: string*
sasl.mechanisms * GSSAPI SASL mechanism to use for authentication. Supported: GSSAPI, PLAIN. NOTE: Despite the name only one mechanism must be configured.
*Type: string*
sasl.kerberos.service.name * kafka Kerberos principal name that Kafka runs as.
*Type: string*
sasl.kerberos.principal * kafkaclient This client's Kerberos principal name.
*Type: string*
sasl.kerberos.kinit.cmd * kinit -S "%{sasl.kerberos.service.name}/%{broker.name}" -k -t "%{sasl.kerberos.keytab}" %{sasl.kerberos.principal} Full kerberos kinit command string, %{config.prop.name} is replaced by corresponding config object value, %{broker.name} returns the broker's hostname.
*Type: string*
sasl.kerberos.keytab * Path to Kerberos keytab file. Uses system default if not set.**NOTE**: This is not automatically used but must be added to the template in sasl.kerberos.kinit.cmd as ... -t %{sasl.kerberos.keytab}.
*Type: string*
sasl.kerberos.min.time.before.relogin * 1 .. 86400000 60000 Minimum time in milliseconds between key refresh attempts.
*Type: integer*
sasl.username * SASL username for use with the PLAIN mechanism
*Type: string*
sasl.password * SASL password for use with the PLAIN mechanism
*Type: string*
group.id * Client group id string. All clients sharing the same group.id belong to the same group.
*Type: string*
partition.assignment.strategy * range,roundrobin Name of partition assignment strategy to use when elected group leader assigns partitions to group members.
*Type: string*
session.timeout.ms * 1 .. 3600000 30000 Client group session and failure detection timeout.
*Type: integer*
heartbeat.interval.ms * 1 .. 3600000 1000 Group session keepalive heartbeat interval.
*Type: integer*
group.protocol.type * consumer Group protocol type
*Type: string*
coordinator.query.interval.ms * 1 .. 3600000 600000 How often to query for the current client group coordinator. If the currently assigned coordinator is down the configured query interval will be divided by ten to more quickly recover in case of coordinator reassignment.
*Type: integer*
enable.auto.commit C true, false true Automatically and periodically commit offsets in the background.
*Type: boolean*
auto.commit.interval.ms C 0 .. 86400000 5000 The frequency in milliseconds that the consumer offsets are committed (written) to offset storage. (0 = disable). This setting is used by the high-level consumer.
*Type: integer*
enable.auto.offset.store C true, false true Automatically store offset of last message provided to application.
*Type: boolean*
queued.min.messages C 1 .. 10000000 100000 Minimum number of messages per topic+partition in the local consumer queue.
*Type: integer*
queued.max.messages.kbytes C 1 .. 1000000000 1000000 Maximum number of kilobytes per topic+partition in the local consumer queue. This value may be overshot by fetch.message.max.bytes.
*Type: integer*
fetch.wait.max.ms C 0 .. 300000 100 Maximum time the broker may wait to fill the response with fetch.min.bytes.
*Type: integer*
fetch.message.max.bytes C 1 .. 1000000000 1048576 Initial maximum number of bytes per topic+partition to request when fetching messages from the broker. If the client encounters a message larger than this value it will gradually try to increase it until the entire message can be fetched.
*Type: integer*
max.partition.fetch.bytes C Alias for fetch.message.max.bytes
fetch.min.bytes C 1 .. 100000000 1 Minimum number of bytes the broker responds with. If fetch.wait.max.ms expires the accumulated data will be sent to the client regardless of this setting.
*Type: integer*
fetch.error.backoff.ms C 0 .. 300000 500 How long to postpone the next fetch request for a topic+partition in case of a fetch error.
*Type: integer*
offset.store.method C none, file, broker broker Offset commit store method: 'file' - local file store (offset.store.path, et.al), 'broker' - broker commit store (requires Apache Kafka 0.8.2 or later on the broker).
*Type: enum value*
consume_cb C Message consume callback (set with rd_kafka_conf_set_consume_cb())
*Type: pointer*
rebalance_cb C Called after consumer group has been rebalanced (set with rd_kafka_conf_set_rebalance_cb())
*Type: pointer*
offset_commit_cb C Offset commit result propagation callback. (set with rd_kafka_conf_set_offset_commit_cb())
*Type: pointer*
enable.partition.eof C true, false true Emit RD_KAFKA_RESP_ERR__PARTITION_EOF event whenever the consumer reaches the end of a partition.
*Type: boolean*
check.crcs C true, false false Verify CRC32 of consumed messages, ensuring no on-the-wire or on-disk corruption to the messages occurred. This check comes at slightly increased CPU usage.
*Type: boolean*
queue.buffering.max.messages P 1 .. 10000000 100000 Maximum number of messages allowed on the producer queue.
*Type: integer*
queue.buffering.max.kbytes P 1 .. 2097151 4000000 Maximum total message size sum allowed on the producer queue.
*Type: integer*
queue.buffering.max.ms P 0 .. 900000 1000 Maximum time, in milliseconds, for buffering data on the producer queue.
*Type: integer*
message.send.max.retries P 0 .. 10000000 2 How many times to retry sending a failing MessageSet. Note: retrying may cause reordering.
*Type: integer*
retries P Alias for message.send.max.retries
retry.backoff.ms P 1 .. 300000 100 The backoff time in milliseconds before retrying a message send.
*Type: integer*
compression.codec P none, gzip, snappy, lz4 none compression codec to use for compressing message sets. This is the default value for all topics, may be overriden by the topic configuration property compression.codec.
*Type: enum value*
batch.num.messages P 1 .. 1000000 10000 Maximum number of messages batched in one MessageSet. The total MessageSet size is also limited by message.max.bytes.
*Type: integer*
delivery.report.only.error P true, false false Only provide delivery reports for failed messages.
*Type: boolean*
dr_cb P Delivery report callback (set with rd_kafka_conf_set_dr_cb())
*Type: pointer*
dr_msg_cb P Delivery report callback (set with rd_kafka_conf_set_dr_msg_cb())
*Type: pointer*

Topic configuration properties

Property C/P Range Default Description
request.required.acks P -1 .. 1000 1 This field indicates how many acknowledgements the leader broker must receive from ISR brokers before responding to the request: 0=Broker does not send any response/ack to client, 1=Only the leader broker will need to ack the message, *-1* or all=broker will block until message is committed by all in sync replicas (ISRs) or broker's in.sync.replicas setting before sending response.
*Type: integer*
acks P Alias for request.required.acks
request.timeout.ms P 1 .. 900000 5000 The ack timeout of the producer request in milliseconds. This value is only enforced by the broker and relies on request.required.acks being != 0.
*Type: integer*
message.timeout.ms P 0 .. 900000 300000 Local message timeout. This value is only enforced locally and limits the time a produced message waits for successful delivery. A time of 0 is infinite.
*Type: integer*
produce.offset.report P true, false false Report offset of produced message back to application. The application must be use the dr_msg_cb to retrieve the offset from rd_kafka_message_t.offset.
*Type: boolean*
partitioner_cb P Partitioner callback (set with rd_kafka_topic_conf_set_partitioner_cb())
*Type: pointer*
opaque * Application opaque (set with rd_kafka_topic_conf_set_opaque())
*Type: pointer*
compression.codec P none, gzip, snappy, lz4, inherit inherit Compression codec to use for compressing message sets.
*Type: enum value*
auto.commit.enable C true, false true If true, periodically commit offset of the last message handed to the application. This committed offset will be used when the process restarts to pick up where it left off. If false, the application will have to call rd_kafka_offset_store() to store an offset (optional). NOTE: This property should only be used with the simple legacy consumer, when using the high-level KafkaConsumer the global enable.auto.commit property must be used instead. NOTE: There is currently no zookeeper integration, offsets will be written to broker or local file according to offset.store.method.
*Type: boolean*
enable.auto.commit C Alias for auto.commit.enable
auto.commit.interval.ms C 10 .. 86400000 60000 The frequency in milliseconds that the consumer offsets are committed (written) to offset storage. This setting is used by the low-level legacy consumer.
*Type: integer*
auto.offset.reset C smallest, earliest, beginning, largest, latest, end, error largest Action to take when there is no initial offset in offset store or the desired offset is out of range: 'smallest','earliest' - automatically reset the offset to the smallest offset, 'largest','latest' - automatically reset the offset to the largest offset, 'error' - trigger an error which is retrieved by consuming messages and checking 'message->err'.
*Type: enum value*
offset.store.path C . Path to local file for storing offsets. If the path is a directory a filename will be automatically generated in that directory based on the topic and partition.
*Type: string*
offset.store.sync.interval.ms C -1 .. 86400000 -1 fsync() interval for the offset file, in milliseconds. Use -1 to disable syncing, and 0 for immediate sync after each write.
*Type: integer*
offset.store.method C file, broker broker Offset commit store method: 'file' - local file store (offset.store.path, et.al), 'broker' - broker commit store (requires "group.id" to be configured and Apache Kafka 0.8.2 or later on the broker.).
*Type: enum value*
consume.callback.max.messages C 0 .. 1000000 0 Maximum number of messages to dispatch in one rd_kafka_consume_callback*() call (0 = unlimited)
*Type: integer*

C/P legend: C = Consumer, P = Producer, * = both