Class: ActiveSupport::Subscriber
Relationships & Source Files | |
Extension / Inclusion / Inheritance Descendants | |
Subclasses:
ActionController::LogSubscriber, ActionMailer::LogSubscriber, ActionView::LogSubscriber, ActiveRecord::LogSubscriber, LogSubscriber, ActiveJob::Logging::LogSubscriber, Rails::Rack::Logger
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Inherits: | Object |
Defined in: | activesupport/lib/active_support/subscriber.rb |
Overview
Subscriber
is an object set to consume 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.
Class Method Summary
-
.attach_to(namespace, subscriber = new, notifier = ActiveSupport::Notifications)
Attach the subscriber to a namespace.
-
.method_added(event)
Adds event subscribers for all new methods added to the class.
- .new ⇒ Subscriber constructor
- .subscribers
Instance Method Summary
Constructor Details
.new ⇒ Subscriber
# File 'activesupport/lib/active_support/subscriber.rb', line 79
def initialize @queue_key = [self.class.name, object_id].join "-" @patterns = [] super end
Class Method Details
.attach_to(namespace, subscriber = new, notifier = ActiveSupport::Notifications)
Attach the subscriber to a namespace.
# File 'activesupport/lib/active_support/subscriber.rb', line 33
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)
Adds event subscribers for all new methods added to the class.
# File 'activesupport/lib/active_support/subscriber.rb', line 47
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
[ GitHub ]# File 'activesupport/lib/active_support/subscriber.rb', line 56
def subscribers @@subscribers ||= [] end
Instance Method Details
#finish(name, id, payload)
[ GitHub ]# File 'activesupport/lib/active_support/subscriber.rb', line 93
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)
[ GitHub ]# File 'activesupport/lib/active_support/subscriber.rb', line 85
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