1 files changed, 26 insertions, 6 deletions
diff --git a/actioncable/lib/action_cable/server/base.rb b/actioncable/lib/action_cable/server/base.rb
index c3b64299e3..717a60fe4f 100644
--- a/actioncable/lib/action_cable/server/base.rb
+++ b/actioncable/lib/action_cable/server/base.rb
@@ -1,4 +1,4 @@
-require 'thread'
+require 'monitor'
 
 module ActionCable
   module Server
@@ -18,8 +18,8 @@ module ActionCable
       attr_reader :mutex
 
       def initialize
-        @mutex = Mutex.new
-        @remote_connections = @stream_event_loop = @worker_pool = @channel_classes = @pubsub = nil
+        @mutex = Monitor.new
+        @remote_connections = @event_loop = @worker_pool = @channel_classes = @pubsub = nil
       end
 
       # Called by Rack to setup the server.
@@ -33,16 +33,36 @@ module ActionCable
         remote_connections.where(identifiers).disconnect
       end
 
+      def restart
+        connections.each(&:close)
+
+        @mutex.synchronize do
+          worker_pool.halt if @worker_pool
+
+          @worker_pool = nil
+        end
+      end
+
       # Gateway to RemoteConnections. See that class for details.
       def remote_connections
         @remote_connections || @mutex.synchronize { @remote_connections ||= RemoteConnections.new(self) }
       end
 
-      def stream_event_loop
-        @stream_event_loop || @mutex.synchronize { @stream_event_loop ||= ActionCable::Connection::StreamEventLoop.new }
+      def event_loop
+        @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 database connection pool and block while they wait for other workers to release their connections. Use a smaller worker pool or a larger
+      # database connection pool instead.
       def worker_pool
         @worker_pool || @mutex.synchronize { @worker_pool ||= ActionCable::Server::Worker.new(max_size: config.worker_pool_size) }
       end