class ActiveSupport::Notifications::Fanout

This class is thread safe. All methods are reentrant.
It just pushes events to all registered log subscribers.
This is a default queue implementation that ships with Notifications.

def finish(name, id, payload, listeners = listeners_for(name)) 

def finish(name, id, payload, listeners = listeners_for(name))
  listeners.each { |s| s.finish(name, id, payload) }
end

def initialize 

def initialize
  @string_subscribers = Hash.new { |h, k| h[k] = [] }
  @other_subscribers = []
  @listeners_for = Concurrent::Map.new
  super
end

def listeners_for(name) 

def listeners_for(name)
  # this is correctly done double-checked locking (Concurrent::Map's lookups have volatile semantics)
  @listeners_for[name] || synchronize do
    # use synchronisation when accessing @subscribers
    @listeners_for[name] ||=
      @string_subscribers[name] + @other_subscribers.select { |s| s.subscribed_to?(name) }
  end
end

def listening?(name) 

def listening?(name)
  listeners_for(name).any?
end

def publish(name, *args) 

def publish(name, *args)
  listeners_for(name).each { |s| s.publish(name, *args) }
end

def start(name, id, payload) 

def start(name, id, payload)
  listeners_for(name).each { |s| s.start(name, id, payload) }
end

def subscribe(pattern = nil, callable = nil, &block) 

def subscribe(pattern = nil, callable = nil, &block)
  subscriber = Subscribers.new(pattern, callable || block)
  synchronize do
    if String === pattern
      @string_subscribers[pattern] << subscriber
      @listeners_for.delete(pattern)
    else
      @other_subscribers << subscriber
      @listeners_for.clear
    end
  end
  subscriber
end

def unsubscribe(subscriber_or_name) 

def unsubscribe(subscriber_or_name)
  synchronize do
    case subscriber_or_name
    when String
      @string_subscribers[subscriber_or_name].clear
      @listeners_for.delete(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)
        @listeners_for.delete(pattern)
      else
        @other_subscribers.delete(subscriber_or_name)
        @listeners_for.clear
      end
    end
  end
end

def wait

This is a sync queue, so there is no waiting. 
def wait
end