Kafka output plugin allows to ingest your records into an Apache Kafka service. This plugin use the official librdkafka C library (built-in dependency)

Configuration Parameters

Specify data format, options available: json, msgpack.
Optional key to store the message
If set, the value of Message_Key_Field in the record will indicate the message key. If not set nor found in the record, Message_Key will be used (if set).
Set the key to store the record timestamp
'iso8601' or 'double'
Single of multiple list of Kafka Brokers, e.g:,
Single entry or list of topics separated by comma (,) that Fluent Bit will use to send messages to Kafka. If only one topic is set, that one will be used for all records. Instead if multiple topics exists, the one set in the record by Topic_Key will be used.
If multiple Topics exists, the value of Topic_Key in the record will indicate the topic to use. E.g: if Topic_Key is router and the record is {"key1": 123, "router": "route_2"}, Fluent Bit will use topic route_2. Note that if the value of Topic_Key is not present in Topics, then by default the first topic in the Topics list will indicate the topic to be used.
adds unknown topics (found in Topic_Key) to Topics. So in Topics only a default topic needs to be configured
Fluent Bit queues data into rdkafka library, if for some reason the underlying library cannot flush the records the queue might fills up blocking new addition of records. The queue_full_retries option set the number of local retries to enqueue the data. The default value is 10 times, the interval between each retry is 1 second. Setting the queue_full_retries value to 0 set's an unlimited number of retries.
{property} can be any librdkafka properties
Setting rdkafka.log.connection.close to false and rdkafka.request.required.acks to 1 are examples of recommended settings of librdfkafka properties.

Getting Started

In order to insert records into Apache Kafka, you can run the plugin from the command line or through the configuration file:

Command Line

The kafka plugin, can read the parameters from the command line in two ways, through the -p argument (property), e.g:
$ fluent-bit -i cpu -o kafka -p brokers= -p topics=test

Configuration File

In your main configuration file append the following Input & Output sections:
Name cpu
Name kafka
Match *
Topics test

Avro Support

Fluent-bit comes with support for avro encoding for the out_kafka plugin. Avro support is optional and must be activated at build-time by using a build def with cmake: -DFLB_AVRO_ENCODER=On such as in the following example which activates:
  • out_kafka with avro encoding
  • fluent-bit's prometheus
  • metrics via an embedded http endpoint
  • debugging support
  • builds the test suites

Kafka Configuration File with Avro Encoding

This is example fluent-bit config tails kubernetes logs, decorates the log lines with kubernetes metadata via the kubernetes filter, and then sends the fully decorated log lines to a kafka broker encoded with a specific avro schema.
Name tail
Tag kube.*
Alias some-alias
Path /logdir/*.log
DB /dbdir/some.db
Skip_Long_Lines On
Refresh_Interval 10
Parser some-parser
Name kubernetes
Match kube.*
Kube_URL https://some_kube_api:443
Kube_CA_File /certs/ca.crt
Kube_Token_File /tokens/token
Kube_Tag_Prefix kube.var.log.containers.
Merge_Log On
Merge_Log_Key log_processed
Name kafka
Match *
Topics test
Schema_str {"name":"avro_logging","type":"record","fields":[{"name":"timestamp","type":"string"},{"name":"stream","type":"string"},{"name":"log","type":"string"},{"name":"kubernetes","type":{"name":"krec","type":"record","fields":[{"name":"pod_name","type":"string"},{"name":"namespace_name","type":"string"},{"name":"pod_id","type":"string"},{"name":"labels","type":{"type":"map","values":"string"}},{"name":"annotations","type":{"type":"map","values":"string"}},{"name":"host","type":"string"},{"name":"container_name","type":"string"},{"name":"docker_id","type":"string"},{"name":"container_hash","type":"string"},{"name":"container_image","type":"string"}]}},{"name":"cluster_name","type":"string"},{"name":"fabric","type":"string"}]}
Schema_id some_schema_id
rdkafka.client.id some_client_id
rdkafka.debug All
rdkafka.enable.ssl.certificate.verification true
rdkafka.ssl.certificate.location /certs/some.cert
rdkafka.ssl.key.location /certs/some.key
rdkafka.ssl.ca.location /certs/some-bundle.crt
rdkafka.security.protocol ssl
rdkafka.request.required.acks 1
rdkafka.log.connection.close false
Format avro
rdkafka.log_level 7
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Configuration Parameters
Getting Started
Command Line
Configuration File
Avro Support