Class: ActiveSupport::Subscriber

Inherits:
Object
  • Object
show all
Defined in:
activesupport/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 Active Record subscriber responsible for collecting statistics about queries:

module ActiveRecord
  class StatsSubscriber < ActiveSupport::Subscriber
    def sql(event)
      Statsd.timing("sql.#{event.payload[:name]}", event.duration)
    end
  end
end

And it’s finally registered as:

ActiveRecord::StatsSubscriber.attach_to :active_record

Since we need to know all instance methods before attaching the log subscriber, the line above should be called after your subscriber definition.

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

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize ⇒ Subscriber

Returns a new instance of Subscriber.



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# File 'activesupport/lib/active_support/subscriber.rb', line 48

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

Class Method Details

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

Attach the subscriber to a namespace.



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# File 'activesupport/lib/active_support/subscriber.rb', line 33

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

  subscriber.public_methods(false).each do |event|
    next if %w{ start finish }.include?(event.to_s)

    notifier.subscribe("#{event}.#{namespace}", subscriber)
  end
end

.subscribers ⇒ Object 



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# File 'activesupport/lib/active_support/subscriber.rb', line 43

def subscribers
  @@subscribers ||= []
end

Instance Method Details

#finish(name, id, payload) ⇒ Object 



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# File 'activesupport/lib/active_support/subscriber.rb', line 61

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

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

#start(name, id, payload) ⇒ Object 



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

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

  event_stack.push e
end