1 files changed, 101 insertions, 0 deletions
diff --git a/actioncable/lib/action_cable/storage_adapter/postgresql.rb b/actioncable/lib/action_cable/storage_adapter/postgresql.rb
new file mode 100644
index 0000000000..1d8460e2ea
--- /dev/null
+++ b/actioncable/lib/action_cable/storage_adapter/postgresql.rb
@@ -0,0 +1,101 @@
+require 'thread'
+
+begin
+  require 'pg'
+rescue Gem::LoadError => e
+  raise Gem::LoadError, "You are trying to use the PostgreSQL ActionCable adapter, but do not have the proper gems installed. Add `gem 'pg'` to your Gemfile (and ensure its version is at the minimum required by ActionCable)."
+end
+
+module ActionCable
+  module StorageAdapter
+    class PostgreSQL < Base
+      # The storage instance used for broadcasting. Not intended for direct user use.
+      def broadcast(channel, payload)
+        with_connection do |pg_conn|
+          pg_conn.exec("NOTIFY #{channel}, '#{payload}'")
+        end
+      end
+
+      def subscribe(channel, callback, success_callback = nil)
+        listener.subscribe_to(channel, callback, success_callback)
+      end
+
+      def unsubscribe(channel, callback)
+        listener.unsubscribe_to(channel, callback)
+      end
+
+      def with_connection(&block) # :nodoc:
+        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
+
+          yield pg_conn
+        end
+      end
+
+      private
+        def listener
+          @listener ||= Listener.new(self)
+        end
+
+        class Listener
+          def initialize(adapter)
+            @adapter = adapter
+            @subscribers = Hash.new { |h,k| h[k] = [] }
+            @sync = Mutex.new
+            @queue = Queue.new
+
+            Thread.new do
+              Thread.current.abort_on_exception = true
+              listen
+            end
+          end
+
+          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
+
+          def subscribe_to(channel, callback, success_callback)
+            @sync.synchronize do
+              if @subscribers[channel].empty?
+                @queue.push([:listen, channel, success_callback])
+              end
+
+              @subscribers[channel] << callback
+            end
+          end
+
+          def unsubscribe_to(channel, callback)
+            @sync.synchronize do
+              @subscribers[channel].delete(callback)
+
+              if @subscribers[channel].empty?
+                @queue.push([:unlisten, channel])
+              end
+            end
+          end
+        end
+    end
+  end
+end