Serialization.md

Karafka by default assumes, you are receiving and sending JSON information.

This means, that if you receive for example an XML payload, deserialization will fail.

Deserializers

Deserializers are used to convert raw Kafka messages payload into a workable format. They are used when working with incoming data.

You can set a default deserializer that will be used for all the topics, or you can specify a deserializer per topic in the routing.

class XmlDeserializer
  def call(message)
    Hash.from_xml(message)
  end
end

App.routes.draw do
  topic :binary_video_details do
    consumer Videos::DetailsConsumer
    deserializer XmlDeserializer.new
  end
end

The default deserializer is Karafka::Serialization::Json::Deserializer.

Serializers

Serializers are used when you send data using Responders. They are responsible for converting your Ruby data into a proper format you wish to use to exchange data using Kafka. By default Karafka::Serialization::Json::Serializer will convert your data into JSON format.

You can set a default serializer that will be used for all the topics, or you can specify a serializer per topic in the responder definition.

class XmlSerializer
  def call(object)
    object.to_xml
  end
end

class ExampleResponder < ApplicationResponder
  topic :users_notified, serializer: XmlSerializer.new

  def respond(user)
    respond_to :users_notified, user
  end
end