3 files changed, 22 insertions, 11 deletions
diff --git a/actioncable/lib/action_cable/server/base.rb b/actioncable/lib/action_cable/server/base.rb
index 778f5ffeed..b1a0e11631 100644
--- a/actioncable/lib/action_cable/server/base.rb
+++ b/actioncable/lib/action_cable/server/base.rb
@@ -52,7 +52,17 @@ module ActionCable
         @event_loop || @mutex.synchronize { @event_loop ||= config.event_loop_class.new }
       end
 
-      # The thread worker pool for handling all the connection work on this server. Default size is set by config.worker_pool_size.
+      # The worker pool is where we run connection callbacks and channel actions. We do as little as possible on the server's main thread.
+      # The worker pool is an executor service that's backed by a pool of threads working from a task queue. The thread pool size maxes out
+      # at 4 worker threads by default. Tune the size yourself with config.action_cable.worker_pool_size.
+      #
+      # Using Active Record, Redis, etc within your channel actions means you'll get a separate connection from each thread in the worker pool.
+      # Plan your deployment accordingly: 5 servers each running 5 Puma workers each running an 8-thread worker pool means at least 200 database
+      # connections.
+      #
+      # Also, ensure that your database connection pool size is as least as large as your worker pool size. Otherwise, workers may oversubscribe
+      # the db connection pool and block while they wait for other workers to release their connections. Use a smaller worker pool or a larger
+      # db connection pool instead.
       def worker_pool
         @worker_pool || @mutex.synchronize { @worker_pool ||= ActionCable::Server::Worker.new(max_size: config.worker_pool_size) }
       end
diff --git a/actioncable/lib/action_cable/server/broadcasting.rb b/actioncable/lib/action_cable/server/broadcasting.rb
index 98025f27f2..8f93564113 100644
--- a/actioncable/lib/action_cable/server/broadcasting.rb
+++ b/actioncable/lib/action_cable/server/broadcasting.rb
@@ -19,27 +19,28 @@ module ActionCable
     #       new Notification data['title'], body: data['body']
     module Broadcasting
       # Broadcast a hash directly to a named <tt>broadcasting</tt>. This will later be JSON encoded.
-      def broadcast(broadcasting, message)
-        broadcaster_for(broadcasting).broadcast(message)
+      def broadcast(broadcasting, message, coder: ActiveSupport::JSON)
+        broadcaster_for(broadcasting, coder: coder).broadcast(message)
       end
 
       # Returns a broadcaster for a named <tt>broadcasting</tt> that can be reused. Useful when you have an object that
       # may need multiple spots to transmit to a specific broadcasting over and over.
-      def broadcaster_for(broadcasting)
-        Broadcaster.new(self, String(broadcasting))
+      def broadcaster_for(broadcasting, coder: ActiveSupport::JSON)
+        Broadcaster.new(self, String(broadcasting), coder: coder)
       end
 
       private
         class Broadcaster
-          attr_reader :server, :broadcasting
+          attr_reader :server, :broadcasting, :coder
 
-          def initialize(server, broadcasting)
-            @server, @broadcasting = server, broadcasting
+          def initialize(server, broadcasting, coder:)
+            @server, @broadcasting, @coder = server, broadcasting, coder
           end
 
           def broadcast(message)
-            server.logger.info "[ActionCable] Broadcasting to #{broadcasting}: #{message}"
-            server.pubsub.broadcast broadcasting, ActiveSupport::JSON.encode(message)
+            server.logger.info "[ActionCable] Broadcasting to #{broadcasting}: #{message.inspect}"
+            encoded = coder ? coder.encode(message) : message
+            server.pubsub.broadcast broadcasting, encoded
           end
         end
     end
diff --git a/actioncable/lib/action_cable/server/configuration.rb b/actioncable/lib/action_cable/server/configuration.rb
index 5fe71caed2..0bb378cf03 100644
--- a/actioncable/lib/action_cable/server/configuration.rb
+++ b/actioncable/lib/action_cable/server/configuration.rb
@@ -14,7 +14,7 @@ module ActionCable
         @log_tags = []
 
         @connection_class = ActionCable::Connection::Base
-        @worker_pool_size = 100
+        @worker_pool_size = 4
 
         @disable_request_forgery_protection = false
       end