Class: ActiveSupport::Subscriber
- 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.
We can detach a subscriber as well:
ActiveRecord::StatsSubscriber.detach_from(:active_record)
Direct Known Subclasses
Instance Attribute Summary collapse
-
#patterns ⇒ Object
readonly
:nodoc:.
Class Method Summary collapse
-
.attach_to(namespace, subscriber = new, notifier = ActiveSupport::Notifications) ⇒ Object
Attach the subscriber to a namespace.
-
.detach_from(namespace, notifier = ActiveSupport::Notifications) ⇒ Object
Detach the subscriber from a namespace.
-
.method_added(event) ⇒ Object
Adds event subscribers for all new methods added to the class.
- .subscribers ⇒ Object
Instance Method Summary collapse
- #finish(name, id, payload) ⇒ Object
-
#initialize ⇒ Subscriber
constructor
A new instance of Subscriber.
- #start(name, id, payload) ⇒ Object
Constructor Details
#initialize ⇒ Subscriber
Returns a new instance of Subscriber.
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# File 'lib/active_support/subscriber.rb', line 124 def initialize @queue_key = [self.class.name, object_id].join "-" @patterns = {} super end |
Instance Attribute Details
#patterns ⇒ Object (readonly)
:nodoc:
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# File 'lib/active_support/subscriber.rb', line 122 def patterns @patterns end |
Class Method Details
.attach_to(namespace, subscriber = new, notifier = ActiveSupport::Notifications) ⇒ Object
Attach the subscriber to a namespace.
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# File 'lib/active_support/subscriber.rb', line 34 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 |
.detach_from(namespace, notifier = ActiveSupport::Notifications) ⇒ Object
Detach the subscriber from a namespace.
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# File 'lib/active_support/subscriber.rb', line 48 def detach_from(namespace, notifier = ActiveSupport::Notifications) @namespace = namespace @subscriber = find_attached_subscriber @notifier = notifier return unless subscriber subscribers.delete(subscriber) # Remove event subscribers of all existing methods on the class. subscriber.public_methods(false).each do |event| remove_event_subscriber(event) end # Reset notifier so that event subscribers will not add for new methods added to the class. @notifier = nil end |
.method_added(event) ⇒ Object
Adds event subscribers for all new methods added to the class.
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# File 'lib/active_support/subscriber.rb', line 67 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
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# File 'lib/active_support/subscriber.rb', line 76 def subscribers @@subscribers ||= [] end |
Instance Method Details
#finish(name, id, payload) ⇒ Object
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# File 'lib/active_support/subscriber.rb', line 139 def finish(name, id, payload) event = event_stack.pop event.finish! event.payload.merge!(payload) method = name.split(".").first send(method, event) end |
#start(name, id, payload) ⇒ Object
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# File 'lib/active_support/subscriber.rb', line 130 def start(name, id, payload) event = ActiveSupport::Notifications::Event.new(name, nil, nil, id, payload) event.start! parent = event_stack.last parent << event if parent event_stack.push event end |