Configuration

Karafka contains multiple configuration options. To keep everything organized, all the configuration options were divided into two groups:

karafka options - options directly related to the Karafka framework and its components.
librdkafka options - options related to librdkafka

To apply all those configuration options, you need to use the #setup method from the Karafka::App class:

class KarafkaApp < Karafka::App
  setup do |config|
    config.client_id = 'my_application'
    # librdkafka configuration options need to be set as symbol values
    config.kafka = {
      'bootstrap.servers': '127.0.0.1:9092'
    }
  end
end

Note: Karafka allows you to redefine some of the settings per each topic, which means that you can have a specific custom configuration that might differ from the default one configured at the app level. This allows you for example, to connect to multiple Kafka clusters.

Karafka configuration options

A list of all the karafka configuration options with their details and defaults can be found here.

librdkafka driver configuration options

A list of all the configuration options related to librdkafka with their details and defaults can be found here.

External components configurators

For additional setup and/or configuration tasks, you can use the app.initialized event hook. It is executed once per process, right after all the framework components are ready (including those dynamically built). It can be used, for example, to configure some external components that need to be based on Karafka internal settings.

class KarafkaApp < Karafka::App
  # Setup and other things...

  # Once everything is loaded and done, assign Karafka app logger as a MyComponent logger
  # @note This example does not use config details, but you can use all the config values
  #   to setup your external components
  monitor.subscribe('app.initialized') do
    MyComponent::Logging.logger = Karafka::App.logger
  end
end

# Or if you prefer, you can do it from the outside of the app
Karafka.monitor.subscribe('app.initialized') do
  MyComponent::Logging.logger = Karafka::App.logger
end

Environment variables settings

There are several env settings you can use:

ENV name	Default	Description
KARAFKA_ENV	development	In what mode this application should boot (production/development/test/etc)
KARAFKA_BOOT_FILE	app_root/karafka.rb	Path to a file that contains Karafka app configuration and booting procedures