class Karafka::Routing::Topic

It is a part of Karafka’s DSL
It belongs to a consumer group as from 0.6 all the topics can work in the same consumer group
Topic stores all the details on how we should interact with Kafka given topic

def build

example for Sidekiq
everywhere except Karafka server command, those would not be initialized on time - for
not yet specified. This is need to be done (cannot be lazy loaded on first use) because
Initializes default values for all the options that support defaults if their values are 
def build
  Karafka::AttributesMap.topic.each { |attr| send(attr) }
  consumer&.topic = self
  self
end

def initialize(name, consumer_group)

Parameters:
  • consumer_group (Karafka::Routing::ConsumerGroup) -- owning consumer group of this topic
  • name (String, Symbol) -- of a topic on which we want to listen 
def initialize(name, consumer_group)
  @name = name.to_s
  @consumer_group = consumer_group
  @attributes = {}
  # @note We use identifier related to the consumer group that owns a topic, because from
  #   Karafka 0.6 we can handle multiple Kafka instances with the same process and we can
  #   have same topic name across mutliple Kafkas
  @id = "#{consumer_group.id}_#{@name}"
end

def responder

Returns:
  • (Class, nil) - Class (not an instance) of a responder that should respond from 
def responder
  @responder ||= Karafka::Responders::Builder.new(consumer).build
end

def to_h

Other tags:
    Note: - This is being used when we validate the consumer_group and its topics

Returns:
  • (Hash) - hash with all the topic attributes 
def to_h
  map = Karafka::AttributesMap.topic.map do |attribute|
    [attribute, public_send(attribute)]
  end
  Hash[map].merge!(
    id: id,
    consumer: consumer
  )
end