/
fanout.rb
446 lines (375 loc) · 12.5 KB
/
fanout.rb
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# frozen_string_literal: true
require "concurrent/map"
require "set"
require "active_support/core_ext/object/try"
module ActiveSupport
module Notifications
class InstrumentationSubscriberError < RuntimeError
attr_reader :exceptions
def initialize(exceptions)
@exceptions = exceptions
exception_class_names = exceptions.map { |e| e.class.name }
super "Exception(s) occurred within instrumentation subscribers: #{exception_class_names.join(', ')}"
end
end
module FanoutIteration # :nodoc:
private
def iterate_guarding_exceptions(collection)
exceptions = nil
collection.each do |s|
yield s
rescue Exception => e
exceptions ||= []
exceptions << e
end
if exceptions
exceptions = exceptions.flat_map do |exception|
exception.is_a?(InstrumentationSubscriberError) ? exception.exceptions : [exception]
end
if exceptions.size == 1
raise exceptions.first
else
raise InstrumentationSubscriberError.new(exceptions), cause: exceptions.first
end
end
collection
end
end
# This is a default queue implementation that ships with Notifications.
# It just pushes events to all registered log subscribers.
#
# This class is thread safe. All methods are reentrant.
class Fanout
def initialize
@mutex = Mutex.new
@string_subscribers = Concurrent::Map.new { |h, k| h.compute_if_absent(k) { [] } }
@other_subscribers = []
@all_listeners_for = Concurrent::Map.new
@groups_for = Concurrent::Map.new
@silenceable_groups_for = Concurrent::Map.new
end
def inspect # :nodoc:
total_patterns = @string_subscribers.size + @other_subscribers.size
"#<#{self.class} (#{total_patterns} patterns)>"
end
def subscribe(pattern = nil, callable = nil, monotonic: false, &block)
subscriber = Subscribers.new(pattern, callable || block, monotonic)
@mutex.synchronize do
case pattern
when String
@string_subscribers[pattern] << subscriber
clear_cache(pattern)
when NilClass, Regexp
@other_subscribers << subscriber
clear_cache
else
raise ArgumentError, "pattern must be specified as a String, Regexp or empty"
end
end
subscriber
end
def unsubscribe(subscriber_or_name)
@mutex.synchronize do
case subscriber_or_name
when String
@string_subscribers[subscriber_or_name].clear
clear_cache(subscriber_or_name)
@other_subscribers.each { |sub| sub.unsubscribe!(subscriber_or_name) }
else
pattern = subscriber_or_name.try(:pattern)
if String === pattern
@string_subscribers[pattern].delete(subscriber_or_name)
clear_cache(pattern)
else
@other_subscribers.delete(subscriber_or_name)
clear_cache
end
end
end
end
def clear_cache(key = nil) # :nodoc:
if key
@all_listeners_for.delete(key)
@groups_for.delete(key)
@silenceable_groups_for.delete(key)
else
@all_listeners_for.clear
@groups_for.clear
@silenceable_groups_for.clear
end
end
class BaseGroup # :nodoc:
include FanoutIteration
def initialize(listeners, name, id, payload)
@listeners = listeners
end
def each(&block)
iterate_guarding_exceptions(@listeners, &block)
end
end
class BaseTimeGroup < BaseGroup # :nodoc:
def start(name, id, payload)
@start_time = now
end
def finish(name, id, payload)
stop_time = now
each do |listener|
listener.call(name, @start_time, stop_time, id, payload)
end
end
end
class MonotonicTimedGroup < BaseTimeGroup # :nodoc:
private
def now
Process.clock_gettime(Process::CLOCK_MONOTONIC)
end
end
class TimedGroup < BaseTimeGroup # :nodoc:
private
def now
Time.now
end
end
class EventedGroup < BaseGroup # :nodoc:
def start(name, id, payload)
each do |s|
s.start(name, id, payload)
end
end
def finish(name, id, payload)
each do |s|
s.finish(name, id, payload)
end
end
end
class EventObjectGroup < BaseGroup # :nodoc:
def start(name, id, payload)
@event = build_event(name, id, payload)
@event.start!
end
def finish(name, id, payload)
@event.payload = payload
@event.finish!
each do |s|
s.call(@event)
end
end
private
def build_event(name, id, payload)
ActiveSupport::Notifications::Event.new name, nil, nil, id, payload
end
end
def groups_for(name) # :nodoc:
groups = @groups_for.compute_if_absent(name) do
all_listeners_for(name).reject(&:silenceable).group_by(&:group_class).transform_values do |s|
s.map(&:delegate)
end
end
silenceable_groups = @silenceable_groups_for.compute_if_absent(name) do
all_listeners_for(name).select(&:silenceable).group_by(&:group_class).transform_values do |s|
s.map(&:delegate)
end
end
unless silenceable_groups.empty?
groups = groups.dup
silenceable_groups.each do |group_class, subscriptions|
active_subscriptions = subscriptions.reject { |s| s.silenced?(name) }
unless active_subscriptions.empty?
groups[group_class] = (groups[group_class] || []) + active_subscriptions
end
end
end
groups
end
# A +Handle+ is used to record the start and finish time of event.
#
# Both #start and #finish must each be called exactly once.
#
# Where possible, it's best to use the block form: ActiveSupport::Notifications.instrument.
# +Handle+ is a low-level API intended for cases where the block form can't be used.
#
# handle = ActiveSupport::Notifications.instrumenter.build_handle("my.event", {})
# begin
# handle.start
# # work to be instrumented
# ensure
# handle.finish
# end
class Handle
include FanoutIteration
def initialize(notifier, name, id, payload) # :nodoc:
@name = name
@id = id
@payload = payload
@groups = notifier.groups_for(name).map do |group_klass, grouped_listeners|
group_klass.new(grouped_listeners, name, id, payload)
end
@state = :initialized
end
def start
ensure_state! :initialized
@state = :started
iterate_guarding_exceptions(@groups) do |group|
group.start(@name, @id, @payload)
end
end
def finish
finish_with_values(@name, @id, @payload)
end
def finish_with_values(name, id, payload) # :nodoc:
ensure_state! :started
@state = :finished
iterate_guarding_exceptions(@groups) do |group|
group.finish(name, id, payload)
end
end
private
def ensure_state!(expected)
if @state != expected
raise ArgumentError, "expected state to be #{expected.inspect} but was #{@state.inspect}"
end
end
end
include FanoutIteration
def build_handle(name, id, payload)
Handle.new(self, name, id, payload)
end
def start(name, id, payload)
handle_stack = (IsolatedExecutionState[:_fanout_handle_stack] ||= [])
handle = build_handle(name, id, payload)
handle_stack << handle
handle.start
end
def finish(name, id, payload, listeners = nil)
handle_stack = IsolatedExecutionState[:_fanout_handle_stack]
handle = handle_stack.pop
handle.finish_with_values(name, id, payload)
end
def publish(name, *args)
iterate_guarding_exceptions(listeners_for(name)) { |s| s.publish(name, *args) }
end
def publish_event(event)
iterate_guarding_exceptions(listeners_for(event.name)) { |s| s.publish_event(event) }
end
def all_listeners_for(name)
# this is correctly done double-checked locking (Concurrent::Map's lookups have volatile semantics)
@all_listeners_for[name] || @mutex.synchronize do
# use synchronisation when accessing @subscribers
@all_listeners_for[name] ||=
@string_subscribers[name] + @other_subscribers.select { |s| s.subscribed_to?(name) }
end
end
def listeners_for(name)
all_listeners_for(name).reject { |s| s.silenced?(name) }
end
def listening?(name)
all_listeners_for(name).any? { |s| !s.silenced?(name) }
end
# This is a sync queue, so there is no waiting.
def wait
end
module Subscribers # :nodoc:
def self.new(pattern, listener, monotonic)
subscriber_class = monotonic ? MonotonicTimed : Timed
if listener.respond_to?(:start) && listener.respond_to?(:finish)
subscriber_class = Evented
else
# Doing this to detect a single argument block or callable
# like `proc { |x| }` vs `proc { |*x| }`, `proc { |**x| }`,
# or `proc { |x, **y| }`
procish = listener.respond_to?(:parameters) ? listener : listener.method(:call)
if procish.arity == 1 && procish.parameters.length == 1
subscriber_class = EventObject
end
end
subscriber_class.new(pattern, listener)
end
class Matcher # :nodoc:
attr_reader :pattern, :exclusions
def self.wrap(pattern)
if String === pattern
pattern
elsif pattern.nil?
AllMessages.new
else
new(pattern)
end
end
def initialize(pattern)
@pattern = pattern
@exclusions = Set.new
end
def unsubscribe!(name)
exclusions << -name if pattern === name
end
def ===(name)
pattern === name && !exclusions.include?(name)
end
class AllMessages
def ===(name)
true
end
def unsubscribe!(*)
false
end
end
end
class Evented # :nodoc:
attr_reader :pattern, :delegate, :silenceable
def initialize(pattern, delegate)
@pattern = Matcher.wrap(pattern)
@delegate = delegate
@silenceable = delegate.respond_to?(:silenced?)
@can_publish = delegate.respond_to?(:publish)
@can_publish_event = delegate.respond_to?(:publish_event)
end
def group_class
EventedGroup
end
def publish(name, *args)
if @can_publish
@delegate.publish name, *args
end
end
def publish_event(event)
if @can_publish_event
@delegate.publish_event event
else
publish(event.name, event.time, event.end, event.transaction_id, event.payload)
end
end
def silenced?(name)
@silenceable && @delegate.silenced?(name)
end
def subscribed_to?(name)
pattern === name
end
def unsubscribe!(name)
pattern.unsubscribe!(name)
end
end
class Timed < Evented # :nodoc:
def group_class
TimedGroup
end
def publish(name, *args)
@delegate.call name, *args
end
end
class MonotonicTimed < Timed # :nodoc:
def group_class
MonotonicTimedGroup
end
end
class EventObject < Evented
def group_class
EventObjectGroup
end
def publish_event(event)
@delegate.call event
end
end
end
end
end
end