discourse/vendor/backports/notification.rb

369 lines
11 KiB
Ruby

module ActiveSupport
remove_const :Notifications
end
module ActiveSupport
module Notifications
# Instrumentors are stored in a thread local.
class Instrumenter
attr_reader :id
def initialize(notifier)
@id = unique_id
@notifier = notifier
end
# Instrument the given block by measuring the time taken to execute it
# and publish it. Notice that events get sent even if an error occurs
# in the passed-in block
def instrument(name, payload={})
@notifier.start(name, @id, payload)
begin
yield
rescue Exception => e
payload[:exception] = [e.class.name, e.message]
raise e
ensure
@notifier.finish(name, @id, payload)
end
end
private
def unique_id
SecureRandom.hex(10)
end
end
class Event
attr_reader :name, :time, :end, :transaction_id, :payload, :duration
def initialize(name, start, ending, transaction_id, payload)
@name = name
@payload = payload.dup
@time = start
@transaction_id = transaction_id
@end = ending
@duration = 1000.0 * (@end - @time)
end
def parent_of?(event)
start = (time - event.time) * 1000
start <= 0 && (start + duration >= event.duration)
end
end
end
end
module ActiveSupport
module Notifications
# This is a default queue implementation that ships with Notifications.
# It just pushes events to all registered log subscribers.
class Fanout
def initialize
@subscribers = []
@listeners_for = {}
end
def subscribe(pattern = nil, block = Proc.new)
subscriber = Subscribers.new pattern, block
@subscribers << subscriber
@listeners_for.clear
subscriber
end
def unsubscribe(subscriber)
@subscribers.reject! { |s| s.matches?(subscriber) }
@listeners_for.clear
end
def start(name, id, payload)
listeners_for(name).each { |s| s.start(name, id, payload) }
end
def finish(name, id, payload)
listeners_for(name).each { |s| s.finish(name, id, payload) }
end
def publish(name, *args)
listeners_for(name).each { |s| s.publish(name, *args) }
end
def listeners_for(name)
@listeners_for[name] ||= @subscribers.select { |s| s.subscribed_to?(name) }
end
def listening?(name)
listeners_for(name).any?
end
# This is a sync queue, so there is no waiting.
def wait
end
module Subscribers # :nodoc:
def self.new(pattern, listener)
if listener.respond_to?(:call)
subscriber = Timed.new pattern, listener
else
subscriber = Evented.new pattern, listener
end
unless pattern
AllMessages.new(subscriber)
else
subscriber
end
end
class Evented #:nodoc:
def initialize(pattern, delegate)
@pattern = pattern
@delegate = delegate
end
def start(name, id, payload)
@delegate.start name, id, payload
end
def finish(name, id, payload)
@delegate.finish name, id, payload
end
def subscribed_to?(name)
@pattern === name.to_s
end
def matches?(subscriber_or_name)
self === subscriber_or_name ||
@pattern && @pattern === subscriber_or_name
end
end
class Timed < Evented
def initialize(pattern, delegate)
@timestack = Hash.new { |h,id|
h[id] = Hash.new { |ids,name| ids[name] = [] }
}
super
end
def publish(name, *args)
@delegate.call name, *args
end
def start(name, id, payload)
@timestack[id][name].push Time.now
end
def finish(name, id, payload)
started = @timestack[id][name].pop
@delegate.call(name, started, Time.now, id, payload)
end
end
class AllMessages # :nodoc:
def initialize(delegate)
@delegate = delegate
end
def start(name, id, payload)
@delegate.start name, id, payload
end
def finish(name, id, payload)
@delegate.finish name, id, payload
end
def publish(name, *args)
@delegate.publish name, *args
end
def subscribed_to?(name)
true
end
alias :matches? :===
end
end
end
end
end
module ActiveSupport
# = Notifications
#
# <tt>ActiveSupport::Notifications</tt> 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 subscriber. For instance, let's store all "render" events in an array:
#
# events = []
#
# ActiveSupport::Notifications.subscribe("render") do |*args|
# events << ActiveSupport::Notifications::Event.new(*args)
# end
#
# 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.duration # => 10 (in milliseconds)
# event.payload # => { :extra => :information }
#
# The block in the <tt>subscribe</tt> 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.
#
# If an exception happens during that particular instrumentation the payload will
# have a key <tt>:exception</tt> 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 <tt>ActiveSupport::Notifications::Event</tt>
# is able to take the arguments as they come and provide an object-oriented
# interface to that data.
#
# It is also possible to pass an object as the second parameter passed to the
# <tt>subscribe</tt> method instead of a block:
#
# module ActionController
# class PageRequest
# def call(name, started, finished, unique_id, payload)
# Rails.logger.debug ["notification:", name, started, finished, unique_id, payload].join(" ")
# end
# end
# end
#
# ActiveSupport::Notifications.subscribe('process_action.action_controller', ActionController::PageRequest.new)
#
# resulting in the following output within the logs including a hash with the payload:
#
# notification: process_action.action_controller 2012-04-13 01:08:35 +0300 2012-04-13 01:08:35 +0300 af358ed7fab884532ec7 {
# :controller=>"Devise::SessionsController",
# :action=>"new",
# :params=>{"action"=>"new", "controller"=>"devise/sessions"},
# :format=>:html,
# :method=>"GET",
# :path=>"/login/sign_in",
# :status=>200,
# :view_runtime=>279.3080806732178,
# :db_runtime=>40.053
# }
#
# 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 <tt>subscribe</tt>, 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.
#
# WARNING: The instrumentation framework is designed for long-running subscribers,
# use this feature sparingly because it wipes some internal caches and that has
# a negative impact on performance.
#
# === 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.
#
module Notifications
@instrumenters = Hash.new { |h,k| h[k] = notifier.listening?(k) }
class << self
attr_accessor :notifier
def publish(name, *args)
notifier.publish(name, *args)
end
def instrument(name, payload = {})
if @instrumenters[name]
instrumenter.instrument(name, payload) { yield payload if block_given? }
else
yield payload if block_given?
end
end
def subscribe(*args, &block)
notifier.subscribe(*args, &block).tap do
@instrumenters.clear
end
end
def subscribed(callback, *args, &block)
subscriber = subscribe(*args, &callback)
yield
ensure
unsubscribe(subscriber)
end
def unsubscribe(args)
notifier.unsubscribe(args)
@instrumenters.clear
end
def instrumenter
Thread.current[:"instrumentation_#{notifier.object_id}"] ||= Instrumenter.new(notifier)
end
end
self.notifier = Fanout.new
end
end