From 78ff63ee4191758940ae8e0efaa5f9915af0a788 Mon Sep 17 00:00:00 2001
From: Matthew Draper <matthew@trebex.net>
Date: Thu, 14 Jan 2016 16:11:02 +1030
Subject: Listener no longer needs to be a singleton

We now only create one adapter instance for the server, so it can hold
the listener. This in turn allows the listener to get the PG connection
from the adapter, which will be a good place to allow more flexible
configuration.
---
 .../lib/action_cable/storage_adapter/postgres.rb   | 110 +++++++++++----------
 1 file changed, 58 insertions(+), 52 deletions(-)

(limited to 'actioncable/lib')

diff --git a/actioncable/lib/action_cable/storage_adapter/postgres.rb b/actioncable/lib/action_cable/storage_adapter/postgres.rb
index 119ea787d7..5d874533be 100644
--- a/actioncable/lib/action_cable/storage_adapter/postgres.rb
+++ b/actioncable/lib/action_cable/storage_adapter/postgres.rb
@@ -5,85 +5,91 @@ module ActionCable
     class Postgres < Base
       # The storage instance used for broadcasting. Not intended for direct user use.
       def broadcast(channel, payload)
-        ActiveRecord::Base.connection_pool.with_connection do |ar_conn|
-          pg_conn = ar_conn.raw_connection
-
-          unless pg_conn.is_a?(PG::Connection)
-            raise 'ActiveRecord database must be Postgres in order to use the Postgres ActionCable storage adapter'
-          end
-
+        with_connection do |pg_conn|
           pg_conn.exec("NOTIFY #{channel}, '#{payload}'")
         end
       end
 
-      def subscribe(channel, message_callback, success_callback = nil)
-        Listener.instance.subscribe_to(channel, message_callback, success_callback)
+      def subscribe(channel, callback, success_callback = nil)
+        listener.subscribe_to(channel, callback, success_callback)
       end
 
-      def unsubscribe(channel, message_callback)
-        Listener.instance.unsubscribe_to(channel, message_callback)
+      def unsubscribe(channel, callback)
+        listener.unsubscribe_to(channel, callback)
       end
 
-      class Listener
-        include Singleton
+      def with_connection(&block) # :nodoc:
+        ActiveRecord::Base.connection_pool.with_connection do |ar_conn|
+          pg_conn = ar_conn.raw_connection
 
-        attr_accessor :subscribers
+          unless pg_conn.is_a?(PG::Connection)
+            raise 'ActiveRecord database must be Postgres in order to use the Postgres ActionCable storage adapter'
+          end
 
-        def initialize
-          @subscribers = Hash.new {|h,k| h[k] = [] }
-          @sync = Mutex.new
-          @queue = Queue.new
+          yield pg_conn
+        end
+      end
 
-          Thread.new do
-            Thread.current.abort_on_exception = true
-            listen
-          end
+      private
+        def listener
+          @listener ||= Listener.new(self)
         end
 
-        def listen
-          ActiveRecord::Base.connection_pool.with_connection do |ar_conn|
-            pg_conn = ar_conn.raw_connection
+        class Listener
+          def initialize(adapter)
+            @adapter = adapter
+            @subscribers = Hash.new { |h,k| h[k] = [] }
+            @sync = Mutex.new
+            @queue = Queue.new
 
-            loop do
-              until @queue.empty?
-                value = @queue.pop(true)
-                if value.first == :listen
-                  pg_conn.exec("LISTEN #{value[1]}")
-                  ::EM.next_tick(&value[2]) if value[2]
-                elsif value.first == :unlisten
-                  pg_conn.exec("UNLISTEN #{value[1]}")
-                end
-              end
+            Thread.new do
+              Thread.current.abort_on_exception = true
+              listen
+            end
+          end
 
-              pg_conn.wait_for_notify(1) do |chan, pid, message|
-                @subscribers[chan].each do |callback|
-                  ::EM.next_tick { callback.call(message) }
+          def listen
+            @adapter.with_connection do |pg_conn|
+              loop do
+                until @queue.empty?
+                  value = @queue.pop(true)
+                  if value.first == :listen
+                    pg_conn.exec("LISTEN #{value[1]}")
+                    ::EM.next_tick(&value[2]) if value[2]
+                  elsif value.first == :unlisten
+                    pg_conn.exec("UNLISTEN #{value[1]}")
+                  end
+
+                  pg_conn.wait_for_notify(1) do |chan, pid, message|
+                    @subscribers[chan].each do |callback|
+                      ::EM.next_tick { callback.call(message) }
+                    end
+                  end
                 end
               end
             end
           end
-        end
 
-        def subscribe_to(channel, callback, success_callback)
-          @sync.synchronize do
-            if @subscribers[channel].empty?
-              @queue.push([:listen, channel, success_callback])
-            end
+          def subscribe_to(channel, callback, success_callback)
+            @sync.synchronize do
+              if @subscribers[channel].empty?
+                @queue.push([:listen, channel, success_callback])
+              end
 
-            @subscribers[channel] << callback
+              @subscribers[channel] << callback
+            end
           end
-        end
 
-        def unsubscribe_to(channel, callback)
-          @sync.synchronize do
-            @subscribers[channel].delete(callback)
+          def unsubscribe_to(channel, callback)
+            @sync.synchronize do
+              @subscribers[channel].delete(callback)
 
-            if @subscribers[channel].empty?
-              @queue.push([:unlisten, channel])
+              if @subscribers[channel].empty?
+                @queue.push([:unlisten, channel])
+              end
             end
           end
         end
-      end
     end
   end
 end
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