Class: ActiveSupport::Subscriber

Inherits:
Object
  • Object
show all
Defined in:
lib/active_support/subscriber.rb

Overview

ActiveSupport::Subscriber is an object set to consume ActiveSupport::Notifications. The subscriber dispatches notifications to a registered object based on its given namespace.

An example would be an Active Record subscriber responsible for collecting statistics about queries:

module ActiveRecord
  class StatsSubscriber < ActiveSupport::Subscriber
    attach_to :active_record

    def sql(event)
      Statsd.timing("sql.#{event.payload[:name]}", event.duration)
    end
  end
end

After configured, whenever a “sql.active_record” notification is published, it will properly dispatch the event (ActiveSupport::Notifications::Event) to the sql method.

Direct Known Subclasses

LogSubscriber

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize ⇒ Subscriber

Returns a new instance of Subscriber.



80
81
82
83
84
 
# File 'lib/active_support/subscriber.rb', line 80

def initialize
  @queue_key = [self.class.name, object_id].join "-"
  @patterns  = []
  super
end

Instance Attribute Details

#patterns ⇒ Object (readonly)

:nodoc:



78
79
80
 
# File 'lib/active_support/subscriber.rb', line 78

def patterns
  @patterns
end

Class Method Details

.attach_to(namespace, subscriber = new, notifier = ActiveSupport::Notifications) ⇒ Object

Attach the subscriber to a namespace.



30
31
32
33
34
35
36
37
38
39
40
41
 
# File 'lib/active_support/subscriber.rb', line 30

def attach_to(namespace, subscriber = new, notifier = ActiveSupport::Notifications)
  @namespace  = namespace
  @subscriber = subscriber
  @notifier   = notifier

  subscribers << subscriber

  # Add event subscribers for all existing methods on the class.
  subscriber.public_methods(false).each do |event|
    add_event_subscriber(event)
  end
end

.method_added(event) ⇒ Object

Adds event subscribers for all new methods added to the class.



44
45
46
47
48
49
50
51
 
# File 'lib/active_support/subscriber.rb', line 44

def method_added(event)
  # Only public methods are added as subscribers, and only if a notifier
  # has been set up. This means that subscribers will only be set up for
  # classes that call #attach_to.
  if public_method_defined?(event) && notifier
    add_event_subscriber(event)
  end
end

.subscribers ⇒ Object 



53
54
55
 
# File 'lib/active_support/subscriber.rb', line 53

def subscribers
  @@subscribers ||= []
end

Instance Method Details

#finish(name, id, payload) ⇒ Object 



94
95
96
97
98
99
100
101
102
 
# File 'lib/active_support/subscriber.rb', line 94

def finish(name, id, payload)
  finished  = now
  event     = event_stack.pop
  event.end = finished
  event.payload.merge!(payload)

  method = name.split(".".freeze).first
  send(method, event)
end

#start(name, id, payload) ⇒ Object 



86
87
88
89
90
91
92
 
# File 'lib/active_support/subscriber.rb', line 86

def start(name, id, payload)
  e = ActiveSupport::Notifications::Event.new(name, now, nil, id, payload)
  parent = event_stack.last
  parent << e if parent

  event_stack.push e
end