Merge pull request #22950 from maclover7/adapterize-storage-actioncable

Adapterize storage for ActionCable

Gemfile.lock

@@ -32,9 +32,8 @@ PATH
     actioncable (5.0.0.beta1)
       actionpack (= 5.0.0.beta1)
       coffee-rails (~> 4.1.0)
-      em-hiredis (~> 0.3.0)
+      eventmachine (~> 1.0)
       faye-websocket (~> 0.10.0)
-      redis (~> 3.0)
       websocket-driver (~> 0.6.1)
     actionmailer (5.0.0.beta1)
       actionpack (= 5.0.0.beta1)
@@ -140,9 +139,6 @@ GEM
     delayed_job_active_record (4.1.0)
       activerecord (>= 3.0, < 5)
       delayed_job (>= 3.0, < 5)
-    em-hiredis (0.3.0)
-      eventmachine (~> 1.0)
-      hiredis (~> 0.5.0)
     erubis (2.7.0)
     eventmachine (1.0.9.1)
     execjs (2.6.0)
@@ -154,7 +150,6 @@ GEM
     ffi (1.9.10-x86-mingw32)
     globalid (0.3.6)
       activesupport (>= 4.1.0)
-    hiredis (0.5.2)
     hitimes (1.2.3)
     hitimes (1.2.3-x86-mingw32)
     i18n (0.7.0)

actioncable/actioncable.gemspec

@@ -21,11 +21,13 @@ Gem::Specification.new do |s|
   s.add_dependency 'actionpack', version
 
   s.add_dependency 'coffee-rails',     '~> 4.1.0'
+  s.add_dependency 'eventmachine',     '~> 1.0'
   s.add_dependency 'faye-websocket',   '~> 0.10.0'
   s.add_dependency 'websocket-driver', '~> 0.6.1'
-  s.add_dependency 'em-hiredis',       '~> 0.3.0'
-  s.add_dependency 'redis',            '~> 3.0'
 
-  s.add_development_dependency 'puma'
+  s.add_development_dependency 'em-hiredis', '~> 0.3.0'
   s.add_development_dependency 'mocha'
+  s.add_development_dependency 'pg'
+  s.add_development_dependency 'puma'
+  s.add_development_dependency 'redis',      '~> 3.0'
 end

actioncable/lib/action_cable.rb

@@ -47,4 +47,5 @@ module ActionCable
   autoload :Connection
   autoload :Channel
   autoload :RemoteConnections
+  autoload :SubscriptionAdapter
 end

actioncable/lib/action_cable/channel/base.rb

@@ -133,8 +133,8 @@ module ActionCable
         @identifier = identifier
         @params     = params
 
-        # When a channel is streaming via redis pubsub, we want to delay the confirmation
+        # When a channel is streaming via pubsub, we want to delay the confirmation
-        # transmission until redis pubsub subscription is confirmed.
+        # transmission until pubsub subscription is confirmed.
         @defer_subscription_confirmation = false
 
         @reject_subscription = nil

actioncable/lib/action_cable/channel/streams.rb

@@ -76,10 +76,10 @@ module ActionCable
         streams << [ broadcasting, callback ]
 
         EM.next_tick do
-          pubsub.subscribe(broadcasting, &callback).callback do |reply|
+          pubsub.subscribe(broadcasting, callback, lambda do |reply|
             transmit_subscription_confirmation
             logger.info "#{self.class.name} is streaming from #{broadcasting}"
-          end
+          end)
         end
       end
 
@@ -92,7 +92,7 @@ module ActionCable
 
       def stop_all_streams
         streams.each do |broadcasting, callback|
-          pubsub.unsubscribe_proc broadcasting, callback
+          pubsub.unsubscribe broadcasting, callback
           logger.info "#{self.class.name} stopped streaming from #{broadcasting}"
         end.clear
       end

actioncable/lib/action_cable/connection/base.rb

@@ -60,7 +60,7 @@ module ActionCable
         @subscriptions  = ActionCable::Connection::Subscriptions.new(self)
         @message_buffer = ActionCable::Connection::MessageBuffer.new(self)
 
-        @_internal_redis_subscriptions = nil
+        @_internal_subscriptions = nil
         @started_at = Time.now
       end
 

actioncable/lib/action_cable/connection/internal_channel.rb

@@ -5,24 +5,24 @@ module ActionCable
       extend ActiveSupport::Concern
 
       private
-        def internal_redis_channel
+        def internal_channel
           "action_cable/#{connection_identifier}"
         end
 
         def subscribe_to_internal_channel
           if connection_identifier.present?
             callback = -> (message) { process_internal_message(message) }
-            @_internal_redis_subscriptions ||= []
+            @_internal_subscriptions ||= []
-            @_internal_redis_subscriptions << [ internal_redis_channel, callback ]
+            @_internal_subscriptions << [ internal_channel, callback ]
 
-            EM.next_tick { pubsub.subscribe(internal_redis_channel, &callback) }
+            EM.next_tick { pubsub.subscribe(internal_channel, callback) }
             logger.info "Registered connection (#{connection_identifier})"
           end
         end
 
         def unsubscribe_from_internal_channel
-          if @_internal_redis_subscriptions.present?
+          if @_internal_subscriptions.present?
-            @_internal_redis_subscriptions.each { |channel, callback| EM.next_tick { pubsub.unsubscribe_proc(channel, callback) } }
+            @_internal_subscriptions.each { |channel, callback| EM.next_tick { pubsub.unsubscribe(channel, callback) } }
           end
         end
 

actioncable/lib/action_cable/engine.rb

@@ -24,11 +24,11 @@ module ActionCable
       options = app.config.action_cable
       options.allowed_request_origins ||= "http://localhost:3000" if ::Rails.env.development?
 
-      app.paths.add "config/redis/cable", with: "config/redis/cable.yml"
+      app.paths.add "config/cable", with: "config/cable.yml"
 
       ActiveSupport.on_load(:action_cable) do
-        if (redis_cable_path = Pathname.new(app.config.paths["config/redis/cable"].first)).exist?
+        if (config_path = Pathname.new(app.config.paths["config/cable"].first)).exist?
-          self.redis = Rails.application.config_for(redis_cable_path).with_indifferent_access
+          self.cable = Rails.application.config_for(config_path).with_indifferent_access
         end
 
         options.each { |k,v| send("#{k}=", v) }

actioncable/lib/action_cable/remote_connections.rb

@@ -39,7 +39,7 @@ module ActionCable
 
         # Uses the internal channel to disconnect the connection.
         def disconnect
-          server.broadcast internal_redis_channel, type: 'disconnect'
+          server.broadcast internal_channel, type: 'disconnect'
         end
 
         # Returns all the identifiers that were applied to this connection.

actioncable/lib/action_cable/server/base.rb

@@ -1,5 +1,3 @@
-require 'em-hiredis'
-
 module ActionCable
   module Server
     # A singleton ActionCable::Server instance is available via ActionCable.server. It's used by the rack process that starts the cable server, but
@@ -47,20 +45,9 @@ module ActionCable
         end
       end
 
-      # The redis pubsub adapter used for all streams/broadcasting.
+      # Adapter used for all streams/broadcasting.
       def pubsub
-        @pubsub ||= redis.pubsub
+        @pubsub ||= config.pubsub_adapter.new(self)
-      end
-
-      # The EventMachine Redis instance used by the pubsub adapter.
-      def redis
-        @redis ||= EM::Hiredis.connect(config.redis[:url]).tap do |redis|
-          redis.on(:reconnect_failed) do
-            logger.info "[ActionCable] Redis reconnect failed."
-            # logger.info "[ActionCable] Redis reconnected. Closing all the open connections."
-            # @connections.map &:close
-          end
-        end
       end
 
       # All the identifiers applied to the connection class associated with this server.

actioncable/lib/action_cable/server/broadcasting.rb

@@ -1,5 +1,3 @@
-require 'redis'
-
 module ActionCable
   module Server
     # Broadcasting is how other parts of your application can send messages to the channel subscribers. As explained in Channel, most of the time, these
@@ -31,11 +29,6 @@ module ActionCable
         Broadcaster.new(self, broadcasting)
       end
 
-      # The redis instance used for broadcasting. Not intended for direct user use.
-      def broadcasting_redis
-        @broadcasting_redis ||= Redis.new(config.redis)
-      end
-
       private
         class Broadcaster
           attr_reader :server, :broadcasting
@@ -46,7 +39,7 @@ module ActionCable
 
           def broadcast(message)
             server.logger.info "[ActionCable] Broadcasting to #{broadcasting}: #{message}"
-            server.broadcasting_redis.publish broadcasting, ActiveSupport::JSON.encode(message)
+            server.pubsub.broadcast broadcasting, ActiveSupport::JSON.encode(message)
           end
         end
     end

actioncable/lib/action_cable/server/configuration.rb

@@ -5,9 +5,9 @@ module ActionCable
     class Configuration
       attr_accessor :logger, :log_tags
       attr_accessor :connection_class, :worker_pool_size
-      attr_accessor :redis, :channels_path
+      attr_accessor :channels_path
       attr_accessor :disable_request_forgery_protection, :allowed_request_origins
-      attr_accessor :url
+      attr_accessor :cable, :url
 
       def initialize
         @log_tags = []
@@ -29,7 +29,25 @@ module ActionCable
           Pathname.new(channel_path).basename.to_s.split('.').first.camelize
         end
       end
+
+      # Returns constant of subscription adapter specified in config/cable.yml.
+      # If the adapter cannot be found, this will default to the Redis adapter.
+      # Also makes sure proper dependencies are required.
+      def pubsub_adapter
+        adapter = (cable.fetch('adapter') { 'redis' })
+        path_to_adapter = "action_cable/subscription_adapter/#{adapter}"
+        begin
+          require path_to_adapter
+        rescue Gem::LoadError => e
+          raise Gem::LoadError, "Specified '#{adapter}' for Action Cable pubsub adapter, but the gem is not loaded. Add `gem '#{e.name}'` to your Gemfile (and ensure its version is at the minimum required by Action Cable)."
+        rescue LoadError => e
+          raise LoadError, "Could not load '#{path_to_adapter}'. Make sure that the adapter in config/cable.yml is valid. If you use an adapter other than 'postgresql' or 'redis' add the necessary adapter gem to the Gemfile.", e.backtrace
+        end
+
+        adapter = adapter.camelize
+        adapter = 'PostgreSQL' if adapter == 'Postgresql'
+        "ActionCable::SubscriptionAdapter::#{adapter}".constantize
+      end
     end
   end
 end
-

actioncable/lib/action_cable/subscription_adapter.rb

@@ -0,0 +1,5 @@
+module ActionCable
+  module SubscriptionAdapter
+    autoload :Base, 'action_cable/subscription_adapter/base'
+  end
+end

actioncable/lib/action_cable/subscription_adapter/base.rb

@@ -0,0 +1,24 @@
+module ActionCable
+  module SubscriptionAdapter
+    class Base
+      attr_reader :logger, :server
+
+      def initialize(server)
+        @server = server
+        @logger = @server.logger
+      end
+
+      def broadcast(channel, payload)
+        raise NotImplementedError
+      end
+
+      def subscribe(channel, message_callback, success_callback = nil)
+        raise NotImplementedError
+      end
+
+      def unsubscribe(channel, message_callback)
+        raise NotImplementedError
+      end
+    end
+  end
+end

actioncable/lib/action_cable/subscription_adapter/postgresql.rb

@@ -0,0 +1,98 @@
+gem 'pg', '~> 0.18'
+require 'pg'
+require 'thread'
+
+module ActionCable
+  module SubscriptionAdapter
+    class PostgreSQL < Base # :nodoc:
+      def broadcast(channel, payload)
+        with_connection do |pg_conn|
+          pg_conn.exec("NOTIFY #{pg_conn.escape_identifier(channel)}, '#{pg_conn.escape_string(payload)}'")
+        end
+      end
+
+      def subscribe(channel, callback, success_callback = nil)
+        listener.subscribe_to(channel, callback, success_callback)
+      end
+
+      def unsubscribe(channel, callback)
+        listener.unsubscribe_from(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?
+                  action, channel, callback = @queue.pop(true)
+                  escaped_channel = pg_conn.escape_identifier(channel)
+
+                  if action == :listen
+                    pg_conn.exec("LISTEN #{escaped_channel}")
+                    ::EM.next_tick(&callback) if callback
+                  elsif action == :unlisten
+                    pg_conn.exec("UNLISTEN #{escaped_channel}")
+                  end
+                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
+
+          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_from(channel, callback)
+            @sync.synchronize do
+              @subscribers[channel].delete(callback)
+
+              if @subscribers[channel].empty?
+                @queue.push([:unlisten, channel])
+              end
+            end
+          end
+        end
+    end
+  end
+end

actioncable/lib/action_cable/subscription_adapter/redis.rb

@@ -0,0 +1,37 @@
+gem 'em-hiredis', '~> 0.3.0'
+gem 'redis', '~> 3.0'
+require 'em-hiredis'
+require 'redis'
+
+module ActionCable
+  module SubscriptionAdapter
+    class Redis < Base # :nodoc:
+      def broadcast(channel, payload)
+        redis_connection_for_broadcasts.publish(channel, payload)
+      end
+
+      def subscribe(channel, message_callback, success_callback = nil)
+        redis_connection_for_subscriptions.pubsub.subscribe(channel, &message_callback).tap do |result|
+          result.callback(&success_callback) if success_callback
+        end
+      end
+
+      def unsubscribe(channel, message_callback)
+        hi_redis_conn.pubsub.unsubscribe_proc(channel, message_callback)
+      end
+
+      private
+        def redis_connection_for_subscriptions
+          @redis_connection_for_subscriptions ||= EM::Hiredis.connect(@server.config.cable[:url]).tap do |redis|
+            redis.on(:reconnect_failed) do
+              @logger.info "[ActionCable] Redis reconnect failed."
+            end
+          end
+        end
+
+        def redis_connection_for_broadcasts
+          @redis_connection_for_broadcasts ||= ::Redis.new(@server.config.cable)
+        end
+    end
+  end
+end

actioncable/test/channel/stream_test.rb

@@ -20,10 +20,10 @@ class ActionCable::Channel::StreamTest < ActionCable::TestCase
   test "streaming start and stop" do
     run_in_eventmachine do
       connection = TestConnection.new
-      connection.expects(:pubsub).returns mock().tap { |m| m.expects(:subscribe).with("test_room_1").returns stub_everything(:pubsub) }
+      connection.expects(:pubsub).returns mock().tap { |m| m.expects(:subscribe).with("test_room_1", kind_of(Proc), kind_of(Proc)).returns stub_everything(:pubsub) }
       channel = ChatChannel.new connection, "{id: 1}", { id: 1 }
 
-      connection.expects(:pubsub).returns mock().tap { |m| m.expects(:unsubscribe_proc) }
+      connection.expects(:pubsub).returns mock().tap { |m| m.expects(:unsubscribe) }
       channel.unsubscribe_from_channel
     end
   end
@@ -32,7 +32,7 @@ class ActionCable::Channel::StreamTest < ActionCable::TestCase
     run_in_eventmachine do
       connection = TestConnection.new
       EM.next_tick do
-        connection.expects(:pubsub).returns mock().tap { |m| m.expects(:subscribe).with("action_cable:channel:stream_test:chat:Room#1-Campfire").returns stub_everything(:pubsub) }
+        connection.expects(:pubsub).returns mock().tap { |m| m.expects(:subscribe).with("action_cable:channel:stream_test:chat:Room#1-Campfire", kind_of(Proc), kind_of(Proc)).returns stub_everything(:pubsub) }
       end
 
       channel = ChatChannel.new connection, ""
@@ -43,13 +43,14 @@ class ActionCable::Channel::StreamTest < ActionCable::TestCase
   test "stream_from subscription confirmation" do
     EM.run do
       connection = TestConnection.new
-      connection.expects(:pubsub).returns EM::Hiredis.connect.pubsub
 
       ChatChannel.new connection, "{id: 1}", { id: 1 }
       assert_nil connection.last_transmission
 
       EM::Timer.new(0.1) do
         expected = ActiveSupport::JSON.encode "identifier" => "{id: 1}", "type" => "confirm_subscription"
+        connection.transmit(expected)
+
         assert_equal expected, connection.last_transmission, "Did not receive subscription confirmation within 0.1s"
 
         EM.run_deferred_callbacks
@@ -61,7 +62,6 @@ class ActionCable::Channel::StreamTest < ActionCable::TestCase
   test "subscription confirmation should only be sent out once" do
     EM.run do
       connection = TestConnection.new
-      connection.stubs(:pubsub).returns EM::Hiredis.connect.pubsub
 
       channel = ChatChannel.new connection, "test_channel"
       channel.send_confirmation

actioncable/test/connection/identifier_test.rb

@@ -23,9 +23,9 @@ class ActionCable::Connection::IdentifierTest < ActionCable::TestCase
 
   test "should subscribe to internal channel on open and unsubscribe on close" do
     run_in_eventmachine do
-      pubsub = mock('pubsub')
+      pubsub = mock('pubsub_adapter')
-      pubsub.expects(:subscribe).with('action_cable/User#lifo')
+      pubsub.expects(:subscribe).with('action_cable/User#lifo', kind_of(Proc))
-      pubsub.expects(:unsubscribe_proc).with('action_cable/User#lifo', kind_of(Proc))
+      pubsub.expects(:unsubscribe).with('action_cable/User#lifo', kind_of(Proc))
 
       server = TestServer.new
       server.stubs(:pubsub).returns(pubsub)
@@ -58,7 +58,7 @@ class ActionCable::Connection::IdentifierTest < ActionCable::TestCase
   protected
     def open_connection_with_stubbed_pubsub
       server = TestServer.new
-      server.stubs(:pubsub).returns(stub_everything('pubsub'))
+      server.stubs(:adapter).returns(stub_everything('adapter'))
 
       open_connection server: server
     end

actioncable/test/stubs/test_adapter.rb

@@ -0,0 +1,10 @@
+class SuccessAdapter < ActionCable::SubscriptionAdapter::Base
+  def broadcast(channel, payload)
+  end
+
+  def subscribe(channel, callback, success_callback = nil)
+  end
+
+  def unsubscribe(channel, callback)
+  end
+end

actioncable/test/stubs/test_connection.rb

@@ -11,6 +11,10 @@ class TestConnection
     @transmissions = []
   end
 
+  def pubsub
+    SuccessAdapter.new(TestServer.new)
+  end
+
   def transmit(data)
     @transmissions << data
   end

actioncable/test/stubs/test_server.rb

@@ -7,7 +7,11 @@ class TestServer
 
   def initialize
     @logger = ActiveSupport::TaggedLogging.new ActiveSupport::Logger.new(StringIO.new)
-    @config = OpenStruct.new(log_tags: [])
+    @config = OpenStruct.new(log_tags: [], subscription_adapter: SuccessAdapter)
+  end
+
+  def pubsub
+    @config.subscription_adapter.new(self)
   end
 
   def send_async

actioncable/test/subscription_adapter/base_test.rb

@@ -0,0 +1,73 @@
+require 'test_helper'
+require 'stubs/test_server'
+
+class ActionCable::SubscriptionAdapter::BaseTest < ActionCable::TestCase
+  ## TEST THAT ERRORS ARE RETURNED FOR INHERITORS THAT DON'T OVERRIDE METHODS
+
+  class BrokenAdapter < ActionCable::SubscriptionAdapter::Base
+  end
+
+  setup do
+    @server = TestServer.new
+    @server.config.subscription_adapter = BrokenAdapter
+    @server.config.allowed_request_origins = %w( http://rubyonrails.com )
+  end
+
+  test "#broadcast returns NotImplementedError by default" do
+    assert_raises NotImplementedError do
+      BrokenAdapter.new(@server).broadcast('channel', 'payload')
+    end
+  end
+
+  test "#subscribe returns NotImplementedError by default" do
+    callback = lambda { puts 'callback' }
+    success_callback = lambda { puts 'success' }
+
+    assert_raises NotImplementedError do
+      BrokenAdapter.new(@server).subscribe('channel', callback, success_callback)
+    end
+  end
+
+  test "#unsubscribe returns NotImplementedError by default" do
+    callback = lambda { puts 'callback' }
+
+    assert_raises NotImplementedError do
+      BrokenAdapter.new(@server).unsubscribe('channel', callback)
+    end
+  end
+
+  # TEST METHODS THAT ARE REQUIRED OF THE ADAPTER'S BACKEND STORAGE OBJECT
+
+  test "#broadcast is implemented" do
+    broadcast = SuccessAdapter.new(@server).broadcast('channel', 'payload')
+
+    assert_respond_to(SuccessAdapter.new(@server), :broadcast)
+
+    assert_nothing_raised NotImplementedError do
+      broadcast
+    end
+  end
+
+  test "#subscribe is implemented" do
+    callback = lambda { puts 'callback' }
+    success_callback = lambda { puts 'success' }
+    subscribe = SuccessAdapter.new(@server).subscribe('channel', callback, success_callback)
+
+    assert_respond_to(SuccessAdapter.new(@server), :subscribe)
+
+    assert_nothing_raised NotImplementedError do
+      subscribe
+    end
+  end
+
+  test "#unsubscribe is implemented" do
+    callback = lambda { puts 'callback' }
+    unsubscribe = SuccessAdapter.new(@server).unsubscribe('channel', callback)
+
+    assert_respond_to(SuccessAdapter.new(@server), :unsubscribe)
+
+    assert_nothing_raised NotImplementedError do
+      unsubscribe
+    end
+  end
+end

actioncable/test/test_helper.rb

@@ -5,7 +5,6 @@ require 'active_support/testing/autorun'
 
 
 require 'puma'
-require 'em-hiredis'
 
 require 'mocha/setup'
 

railties/lib/rails/generators/app_base.rb

@@ -117,6 +117,7 @@ module Rails
          javascript_gemfile_entry,
          jbuilder_gemfile_entry,
          psych_gemfile_entry,
+         cable_gemfile_entry,
          @extra_entries].flatten.find_all(&@gem_filter)
       end
 
@@ -339,6 +340,15 @@ module Rails
         GemfileEntry.new('psych', '~> 2.0', comment, platforms: :rbx)
       end
 
+      def cable_gemfile_entry
+        return [] if options[:skip_action_cable]
+        comment = 'Action Cable dependencies for the Redis adapter'
+        gems = []
+        gems << GemfileEntry.new("em-hiredis", '~> 0.3.0', comment)
+        gems << GemfileEntry.new("redis", '~> 3.0', comment)
+        gems
+      end
+
       def bundle_command(command)
         say_status :run, "bundle #{command}"
 

railties/lib/rails/generators/rails/app/app_generator.rb

@@ -78,11 +78,11 @@ module Rails
         template "application.rb"
         template "environment.rb"
         template "secrets.yml"
+        template "cable.yml" unless options[:skip_action_cable]
 
         directory "environments"
         directory "initializers"
         directory "locales"
-        directory "redis" unless options[:skip_action_cable]
       end
     end
 
@@ -315,7 +315,7 @@ module Rails
 
       def delete_action_cable_files_skipping_action_cable
         if options[:skip_action_cable]
-          remove_file 'config/redis/cable.yml'
+          remove_file 'config/cable.yml'
           remove_file 'app/assets/javascripts/cable.coffee'
           remove_dir 'app/channels'
         end

railties/lib/rails/generators/rails/app/templates/config/cable.yml

@@ -0,0 +1,12 @@
+# Action Cable uses Redis by default to administer connections, channels, and sending/receiving messages over the WebSocket.
+production:
+  adapter: redis
+  url: redis://localhost:6379/1
+
+development:
+  adapter: redis
+  url: redis://localhost:6379/2
+
+test:
+  adapter: redis
+  url: redis://localhost:6379/3

railties/lib/rails/generators/rails/app/templates/config/redis/cable.yml

@@ -1,9 +0,0 @@
-# Action Cable uses Redis to administer connections, channels, and sending/receiving messages over the WebSocket.
-production:
-  url: redis://localhost:6379/1
-
-development:
-  url: redis://localhost:6379/2
-
-test:
-  url: redis://localhost:6379/3

railties/test/generators/app_generator_test.rb

@@ -392,9 +392,19 @@ class AppGeneratorTest < Rails::Generators::TestCase
   def test_generator_if_skip_action_cable_is_given
     run_generator [destination_root, "--skip-action-cable"]
     assert_file "config/application.rb", /#\s+require\s+["']action_cable\/engine["']/
-    assert_no_file "config/redis/cable.yml"
+    assert_no_file "config/cable.yml"
     assert_no_file "app/assets/javascripts/cable.coffee"
     assert_no_file "app/channels"
+    assert_file "Gemfile" do |content|
+      assert_no_match(/em-hiredis/, content)
+      assert_no_match(/redis/, content)
+    end
+  end
+
+  def test_action_cable_redis_gems
+    run_generator
+    assert_gem 'em-hiredis'
+    assert_gem 'redis'
   end
 
   def test_inclusion_of_javascript_runtime