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require 'thread'
require 'active_support/core_ext/module/delegation'
require 'active_support/core_ext/module/attribute_accessors'
require 'active_support/secure_random'
module ActiveSupport
# Notifications provides an instrumentation API for Ruby. To instrument an
# action in Ruby you just need to do:
#
# ActiveSupport::Notifications.instrument(:render, :extra => :information) do
# render :text => "Foo"
# end
#
# You can consume those events and the information they provide by registering
# a subscriber. For instance, let's store all instrumented events in an array:
#
# @events = []
#
# ActiveSupport::Notifications.subscribe do |*args|
# @events << ActiveSupport::Notifications::Event.new(*args)
# end
#
# ActiveSupport::Notifications.instrument(:render, :extra => :information) do
# render :text => "Foo"
# end
#
# event = @events.first
# event.name #=> :render
# event.duration #=> 10 (in miliseconds)
# event.result #=> "Foo"
# event.payload #=> { :extra => :information }
#
# When subscribing to Notifications, you can pass a pattern, to only consume
# events that match the pattern:
#
# ActiveSupport::Notifications.subscribe(/render/) do |event|
# @render_events << event
# end
#
# Notifications ships with a queue implementation that consumes and publish events
# to subscribers in a thread. You can use any queue implementation you want.
#
module Notifications
mattr_accessor :queue
class << self
delegate :instrument, :transaction_id, :transaction, :to => :instrumenter
def instrumenter
Thread.current[:notifications_instrumeter] ||= Instrumenter.new(publisher)
end
def publisher
@publisher ||= Publisher.new(queue)
end
def subscribe(pattern=nil, &block)
Subscriber.new(queue).bind(pattern).subscribe(&block)
end
end
class Instrumenter
def initialize(publisher)
@publisher = publisher
@id = random_id
end
def transaction
@id, old_id = random_id, @id
yield
ensure
@id = old_id
end
def transaction_id
@id
end
def instrument(name, payload={})
time = Time.now
result = yield if block_given?
ensure
@publisher.publish(name, time, Time.now, result, @id, payload)
end
private
def random_id
SecureRandom.hex(10)
end
end
class Publisher
def initialize(queue)
@queue = queue
end
def publish(*args)
@queue.publish(*args)
end
end
class Subscriber
def initialize(queue)
@queue = queue
end
def bind(pattern)
@pattern = pattern
self
end
def subscribe
@queue.subscribe(@pattern) do |*args|
yield *args
end
end
end
class Event
attr_reader :name, :time, :end, :transaction_id, :result, :payload
def initialize(name, start, ending, result, transaction_id, payload)
@name = name
@payload = payload.dup
@time = start
@transaction_id = transaction_id
@end = ending
@result = result
end
def duration
@duration ||= 1000.0 * (@end - @time)
end
def parent_of?(event)
start = (self.time - event.time) * 1000
start <= 0 && (start + duration >= event.duration)
end
end
# This is a default queue implementation that ships with Notifications. It
# consumes events in a thread and publish them to all registered subscribers.
#
class LittleFanout
def initialize
@listeners = []
@stream = Queue.new
Thread.new { consume }
end
def publish(*args)
@stream.push(args)
end
def subscribe(pattern=nil, &block)
@listeners << Listener.new(pattern, &block)
end
def consume
while args = @stream.shift
@listeners.each { |l| l.publish(*args) }
end
end
class Listener
# attr_reader :thread
def initialize(pattern, &block)
@pattern = pattern
@subscriber = block
@queue = Queue.new
Thread.new { consume }
end
def publish(name, *args)
if !@pattern || @pattern === name.to_s
@queue << args.unshift(name)
end
end
def consume
while args = @queue.shift
@subscriber.call(*args)
end
end
end
end
end
Notifications.queue = Notifications::LittleFanout.new
end
|
