Class: Karafka::Routing::ConsumerGroup

Inherits:
Object
  • Object
show all
Defined in:
lib/karafka/routing/consumer_group.rb

Overview

Note:

A single consumer group represents Kafka consumer group, but it may not match 1:1 with subscription groups. There can be more subscription groups than consumer groups

Object used to describe a single consumer group that is going to subscribe to given topics It is a part of Karafka’s DSL

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(name) ⇒ ConsumerGroup

Returns a new instance of ConsumerGroup.

Parameters:

  • name (String, Symbol) —

    raw name of this consumer group. Raw means, that it does not yet have an application client_id namespace, this will be added here by default. We add it to make a multi-system development easier for people that don’t use kafka and don’t understand the concept of consumer groups.



23
24
25
26
27
28
29
30
 
# File 'lib/karafka/routing/consumer_group.rb', line 23

def initialize(name)
  @name = name.to_s
  @id = Karafka::App.config.consumer_mapper.call(name)
  @topics = Topics.new([])
  # Initialize the subscription group so there's always a value for it, since even if not
  # defined directly, a subscription group will be created
  @current_subscription_group_id = SubscriptionGroup.id
end

Instance Attribute Details

#current_subscription_group_id ⇒ Object

This is a “virtual” attribute that is not building subscription groups. It allows us to store the “current” subscription group defined in the routing This subscription group id is then injected into topics, so we can compute the subscription groups



17
18
19
 
# File 'lib/karafka/routing/consumer_group.rb', line 17

def current_subscription_group_id
  @current_subscription_group_id
end

#id ⇒ Object (readonly)

Returns the value of attribute id.



11
12
13
 
# File 'lib/karafka/routing/consumer_group.rb', line 11

def id
  @id
end

#name ⇒ Object (readonly)

Returns the value of attribute name.



11
12
13
 
# File 'lib/karafka/routing/consumer_group.rb', line 11

def name
  @name
end

#topics ⇒ Object (readonly)

Returns the value of attribute topics.



11
12
13
 
# File 'lib/karafka/routing/consumer_group.rb', line 11

def topics
  @topics
end

Instance Method Details

#active? ⇒ Boolean

Returns true if this consumer group should be active in our current process.

Returns:

  • (Boolean) —

    true if this consumer group should be active in our current process



33
34
35
36
37
38
 
# File 'lib/karafka/routing/consumer_group.rb', line 33

def active?
  cgs = Karafka::App.config.internal.routing.active.consumer_groups

  # When empty it means no groups were specified, hence all should be used
  cgs.empty? || cgs.include?(name)
end

#subscription_group=(name = SubscriptionGroup.id, &block) ⇒ Object

Assigns the current subscription group id based on the defined one and allows for further topic definition

Parameters:

  • name (String, Symbol) (defaults to: SubscriptionGroup.id) —

    name of the current subscription group

  • block (Proc) —

    block that may include topics definitions



58
59
60
61
62
63
64
65
66
67
68
 
# File 'lib/karafka/routing/consumer_group.rb', line 58

def subscription_group=(name = SubscriptionGroup.id, &block)
  # We cast it here, so the routing supports symbol based but that's anyhow later on
  # validated as a string
  @current_subscription_group_id = name

  Proxy.new(self, &block)

  # We need to reset the current subscription group after it is used, so it won't leak
  # outside to other topics that would be defined without a defined subscription group
  @current_subscription_group_id = SubscriptionGroup.id
end

#subscription_groups ⇒ Array<Routing::SubscriptionGroup>

Returns all the subscription groups build based on the consumer group topics.

Returns:



72
73
74
75
76
77
78
79
 
# File 'lib/karafka/routing/consumer_group.rb', line 72

def subscription_groups
  @subscription_groups ||= App
                           .config
                           .internal
                           .routing
                           .subscription_groups_builder
                           .call(topics)
end

#to_h ⇒ Hash

Hashed version of consumer group that can be used for validation purposes topics inside of it.

Returns:

  • (Hash) —

    hash with consumer group attributes including serialized to hash



84
85
86
87
88
89
 
# File 'lib/karafka/routing/consumer_group.rb', line 84

def to_h
  {
    topics: topics.map(&:to_h),
    id: id
  }.freeze
end

#topic=(name, &block) ⇒ Karafka::Routing::Topic

Builds a topic representation inside of a current consumer group route

Parameters:

  • name (String, Symbol) —

    name of topic to which we want to subscribe

  • block (Proc) —

    block that we want to evaluate in the topic context

Returns:



44
45
46
47
48
49
50
51
52
 
# File 'lib/karafka/routing/consumer_group.rb', line 44

def topic=(name, &block)
  topic = Topic.new(name, self)
  @topics << Proxy.new(topic, &block).target
  built_topic = @topics.last
  # We overwrite it conditionally in case it was not set by the user inline in the topic
  # block definition
  built_topic.subscription_group ||= current_subscription_group_id
  built_topic
end