diff options
Diffstat (limited to 'activesupport/lib/active_support/notifications.rb')
| -rw-r--r-- | activesupport/lib/active_support/notifications.rb | 101 |
1 files changed, 87 insertions, 14 deletions
diff --git a/activesupport/lib/active_support/notifications.rb b/activesupport/lib/active_support/notifications.rb index b5a70d5933..f549d2fff3 100644 --- a/activesupport/lib/active_support/notifications.rb +++ b/activesupport/lib/active_support/notifications.rb @@ -1,36 +1,102 @@ module ActiveSupport - # Notifications provides an instrumentation API for Ruby. To instrument an - # action in Ruby you just need to do: + # = Notifications # - # ActiveSupport::Notifications.instrument(:render, :extra => :information) do + # +ActiveSupport::Notifications+ provides an instrumentation API for Ruby. + # + # == Instrumenters + # + # To instrument an event you just need to do: + # + # ActiveSupport::Notifications.instrument("render", :extra => :information) do # render :text => "Foo" # end # + # That executes the block first and notifies all subscribers once done. + # + # In the example above "render" is the name of the event, and the rest is called + # the _payload_. The payload is a mechanism that allows instrumenters to pass + # extra information to subscribers. Payloads consist of a hash whose contents + # are arbitrary and generally depend on the event. + # + # == Subscribers + # # You can consume those events and the information they provide by registering - # a log subscriber. For instance, let's store all instrumented events in an array: + # a subscriber. For instance, let's store all "render" events in an array: # - # @events = [] + # events = [] # - # ActiveSupport::Notifications.subscribe do |*args| - # @events << ActiveSupport::Notifications::Event.new(*args) + # ActiveSupport::Notifications.subscribe("render") do |*args| + # events << ActiveSupport::Notifications::Event.new(*args) # end # - # ActiveSupport::Notifications.instrument(:render, :extra => :information) do + # That code returns right away, you are just subscribing to "render" events. + # The block will be called asynchronously whenever someone instruments "render": + # + # ActiveSupport::Notifications.instrument("render", :extra => :information) do # render :text => "Foo" # end # - # event = @events.first - # event.name # => :render + # event = events.first + # event.name # => "render" # event.duration # => 10 (in milliseconds) # event.payload # => { :extra => :information } # - # When subscribing to Notifications, you can pass a pattern, to only consume - # events that match the pattern: + # The block in the +subscribe+ call gets the name of the event, start + # timestamp, end timestamp, a string with a unique identifier for that event + # (something like "535801666f04d0298cd6"), and a hash with the payload, in + # that order. # - # ActiveSupport::Notifications.subscribe(/render/) do |event| - # @render_events << event + # If an exception happens during that particular instrumentation the payload will + # have a key +:exception+ with an array of two elements as value: a string with + # the name of the exception class, and the exception message. + # + # As the previous example depicts, the class +ActiveSupport::Notifications::Event+ + # is able to take the arguments as they come and provide an object-oriented + # interface to that data. + # + # You can also subscribe to all events whose name matches a certain regexp: + # + # ActiveSupport::Notifications.subscribe(/render/) do |*args| + # ... # end # + # and even pass no argument to +subscribe+, in which case you are subscribing + # to all events. + # + # == Temporary Subscriptions + # + # Sometimes you do not want to subscribe to an event for the entire life of + # the application. There are two ways to unsubscribe. + # + # === Subscribe While a Block Runs + # + # You can subscribe to some event temporarily while some block runs. For + # example, in + # + # callback = lambda {|*args| ... } + # ActiveSupport::Notifications.subscribed(callback, "sql.active_record") do + # ... + # end + # + # the callback will be called for all "sql.active_record" events instrumented + # during the execution of the block. The callback is unsubscribed automatically + # after that. + # + # === Manual Unsubscription + # + # The +subscribe+ method returns a subscriber object: + # + # subscriber = ActiveSupport::Notifications.subscribe("render") do |*args| + # ... + # end + # + # To prevent that block from being called anymore, just unsubscribe passing + # that reference: + # + # ActiveSupport::Notifications.unsubscribe(subscriber) + # + # == Default Queue + # # Notifications ships with a queue implementation that consumes and publish events # to log subscribers in a thread. You can use any queue implementation you want. # @@ -62,6 +128,13 @@ module ActiveSupport end end + def subscribed(callback, *args, &block) + subscriber = subscribe(*args, &callback) + yield + ensure + unsubscribe(subscriber) + end + def unsubscribe(args) notifier.unsubscribe(args) @instrumenters.clear |