omkafka: write to Apache Kafka

Module Name: omkafka
Author: Rainer Gerhards <>
Available since: v8.7.0

The omkafka plug-in implements an Apache Kafka producer, permitting rsyslog to write data to Kafka.

Configuration Parameters

Module Parameters

Currently none.

Action Parameters

Note that omkafka supports some Array-type parameters. While the parameter name can only be set once, it is possible to set multiple values with that single parameter.

For example, to select “snappy” compression, you can use

action(type="omkafka" topic="mytopic" confParam="compression.codec=snappy")

which is equivalent to

action(type="omkafka" topic="mytopic" confParam=["compression.codec=snappy"])

To specify multiple values, just use the bracket notation and create a comma-delimited list of values as shown here:

action(type="omkafka" topic="mytopic"
broker [brokers]

Type: Array

Default: “localhost:9092”

Specifies the broker(s) to use.

topic [topicName]


Specifies the topic to produce to.

key [key]

Default: none

Kafka key to be used for all messages.

dynatopic [boolean]

Default: off

If set, the topic parameter becomes a template for which topic to produce messages to. The cache is cleared on HUP.

dynatopic.cachesize [positiveInteger]

Default: 50

If set, defines the number of topics that will be kept in the dynatopic cache. [boolean]

Default: off

librdkafka provides an automatic partitioning function that will evenly split the produced messages into all partitions configured for that topic.

To use, set”on”. This is instead of specifying the number of partitions on the producer side, where it would be easier to change the kafka configuration on the cluster for number of partitions/topic vs on every machine talking to Kafka via rsyslog.

If set, it will override any other partitioning scheme configured.

partitions.number [positiveInteger]

Default: none

If set, specifies how many partitions exists and activates load-balancing among them. Messages are distributed more or less evenly between the partitions. Note that the number specified must be correct. Otherwise, some errors may occur or some partitions may never receive data.

partitions.usedFixed [positiveInteger]

Default: none

If set, specifies the partition to which data is produced. All data goes to this partition, no other partition is ever involved for this action.

errorFile [filename]

Default: none

If set, messages that could not be sent and caused an error messages are written to the file specified. This file is in JSON format, with a single record being written for each message in error. The entry contains the full message, as well as Kafka error number and reason string.

The idea behind the error file is that the admin can periodically run a script that reads the error file and reacts on it. Note that the error file is kept open from when the first error occured up until rsyslog is terminated or received a HUP signal.

confParam [parameter]

Type: Array

Default: none

Permits to specify Kafka options. Rather than offering a myriad of config settings to match the Kafka parameters, we provide this setting here as a vehicle to set any Kafka parameter. This has the big advantage that Kafka parameters that come up in new releases can immediately be used.

Note that we use librdkafka for the Kafka connection, so the parameters are actually those that librdkafka supports. As of our understanding, this is a superset of the native Kafka parameters.

topicConfParam [parameter]

Type: Array

Default: none

In essence the same as confParam, but for the Kafka topic.

template [templateName]

Default: template set via “template” module parameter

Sets the template to be used for this action.

closeTimeout [positiveInteger]

Default: 2000

Sets the time to wait in ms (milliseconds) for draining messages submitted to kafka-handle (provided by librdkafka) before closing it.

The maximum value of closeTimeout used across all omkafka action instances is used as librdkafka unload-timeout while unloading the module (for shutdown, for instance).

resubmitOnFailure [boolean]

Default: off

Available since: 8.28.0

If enabled, failed messages will be resubmit automatically when kafka is able to send messages again. To prevent message loss, this option should be enabled.

keepFailedMessages [boolean]

Default: off

Available since: 8.28.0

If enabled, failed messages will be saved and loaded on shutdown/startup and resend after startup if the kafka server is able to receive messages again. This setting requires resubmitOnFailure to be enabled as well.

failedMsgFile [filename]

Default: none

Available since: 8.28.0

Filename where the failed messages should be stored into. Needs to be set when keepFailedMessages is enabled, otherwise failed messages won’t be saved.

Caveats/Known Bugs

  • currently none


To be added, see intro to action parameters.