Merge pull request #27577 from maclover7/jm-fix-27547

Action Cable owns database connection, not Active Record

actioncable/lib/action_cable/subscription_adapter/postgresql.rb

@@ -14,7 +14,7 @@ module ActionCable
       end
 
       def broadcast(channel, payload)
-        with_connection do |pg_conn|
+        with_broadcast_connection do |pg_conn|
           pg_conn.exec("NOTIFY #{pg_conn.escape_identifier(channel_identifier(channel))}, '#{pg_conn.escape_string(payload)}'")
         end
       end
@@ -31,14 +31,24 @@ module ActionCable
         listener.shutdown
       end
 
-      def with_connection(&block) # :nodoc:
+      def with_subscriptions_connection(&block) # :nodoc:
+        ar_conn = ActiveRecord::Base.connection_pool.checkout.tap do |conn|
+          # Action Cable is taking ownership over this database connection, and
+          # will perform the necessary cleanup tasks
+          ActiveRecord::Base.connection_pool.remove(conn)
+        end
+        pg_conn = ar_conn.raw_connection
+
+        verify!(pg_conn)
+        yield pg_conn
+      ensure
+        ar_conn.disconnect!
+      end
+
+      def with_broadcast_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 "The Active Record database must be PostgreSQL in order to use the PostgreSQL Action Cable storage adapter"
-          end
-
+          verify!(pg_conn)
           yield pg_conn
         end
       end
@@ -52,6 +62,12 @@ module ActionCable
           @listener || @server.mutex.synchronize { @listener ||= Listener.new(self, @server.event_loop) }
         end
 
+        def verify!(pg_conn)
+          unless pg_conn.is_a?(PG::Connection)
+            raise "The Active Record database must be PostgreSQL in order to use the PostgreSQL Action Cable storage adapter"
+          end
+        end
+
         class Listener < SubscriberMap
           def initialize(adapter, event_loop)
             super()
@@ -67,7 +83,7 @@ module ActionCable
           end
 
           def listen
-            @adapter.with_connection do |pg_conn|
+            @adapter.with_subscriptions_connection do |pg_conn|
               catch :shutdown do
                 loop do
                   until @queue.empty?

actioncable/test/subscription_adapter/postgresql_test.rb

@@ -39,4 +39,27 @@ class PostgresqlAdapterTest < ActionCable::TestCase
   def cable_config
     { adapter: "postgresql" }
   end
+
+  def test_clear_active_record_connections_adapter_still_works
+    server = ActionCable::Server::Base.new
+    server.config.cable = cable_config.with_indifferent_access
+    server.config.logger = Logger.new(StringIO.new).tap { |l| l.level = Logger::UNKNOWN }
+
+    adapter_klass = Class.new(server.config.pubsub_adapter) do
+      def active?
+        !@listener.nil?
+      end
+    end
+
+    adapter = adapter_klass.new(server)
+
+    subscribe_as_queue("channel", adapter) do |queue|
+      adapter.broadcast("channel", "hello world")
+      assert_equal "hello world", queue.pop
+    end
+
+    ActiveRecord::Base.clear_reloadable_connections!
+
+    assert adapter.active?
+  end
 end