Kafka

The Kafka input plugin allows subscribing to one or more Kafka topics to collect messages from an Apache Kafka service. This plugin uses the official librdkafka C library (built-in dependency).

Configuration Parameters

Key	Description	default
brokers	Single or multiple list of Kafka Brokers, e.g: 192.168.1.3:9092, 192.168.1.4:9092.
topics	Single entry or list of topics separated by comma (,) that Fluent Bit will subscribe to.
format	Serialization format of the messages. If set to "json", the payload will be parsed as json.	none
client_id	Client id passed to librdkafka.
group_id	Group id passed to librdkafka.	fluent-bit
poll_ms	Kafka brokers polling interval in milliseconds.	500
Buffer_Max_Size	Specify the maximum size of buffer per cycle to poll kafka messages from subscribed topics. To increase throughput, specify larger size.	4M
rdkafka.{property}	{property} can be any librdkafka properties
threaded	Indicates whether to run this input in its own thread.	false

Getting Started

In order to subscribe/collect messages from Apache Kafka, you can run the plugin from the command line or through the configuration file:

Command Line

The kafka plugin can read parameters through the -p argument (property), e.g:

$ fluent-bit -i kafka -o stdout -p brokers=192.168.1.3:9092 -p topics=some-topic

Configuration File

In your main configuration file append the following Input & Output sections:

[INPUT]
    Name        kafka
    Brokers     192.168.1.3:9092
    Topics      some-topic
    poll_ms     100

[OUTPUT]
    Name        stdout

Example of using kafka input/output plugins

The Fluent Bit source repository contains a full example of using Fluent Bit to process Kafka records:

[INPUT]
    Name kafka
    brokers kafka-broker:9092
    topics fb-source
    poll_ms 100
    format json

[FILTER]
    Name    lua
    Match   *
    script  kafka.lua
    call    modify_kafka_message

[OUTPUT]
    Name kafka
    brokers kafka-broker:9092
    topics fb-sink

The above will connect to the broker listening on kafka-broker:9092 and subscribe to the fb-source topic, polling for new messages every 100 milliseconds.

Since the payload will be in json format, we ask the plugin to automatically parse the payload with format json.

Every message received is then processed with kafka.lua and sent back to the fb-sink topic of the same broker.

The example can be executed locally with make start in the examples/kafka_filter directory (docker/compose is used).