Synchronize the lazy setters in Server

They're all at risk of races on the first requests.

1 files changed, 16 insertions, 7 deletions

diff --git a/actioncable/lib/action_cable/server/base.rb b/actioncable/lib/action_cable/server/base.rb
index b00abd208c..fe48c112df 100644
--- a/actioncable/lib/action_cable/server/base.rb
+++ b/actioncable/lib/action_cable/server/base.rb
@@ -1,3 +1,5 @@
+require 'thread'
+
 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
@@ -13,7 +15,12 @@ module ActionCable
       def self.logger; config.logger; end
       delegate :logger, to: :config
 
+      attr_reader :mutex
+
       def initialize
+        @mutex = Mutex.new
+
+        @remote_connections = @stream_event_loop = @worker_pool = @channel_classes = @pubsub = nil
       end
 
       # Called by rack to setup the server.
@@ -29,29 +36,31 @@ module ActionCable
 
       # Gateway to RemoteConnections. See that class for details.
       def remote_connections
-        @remote_connections ||= RemoteConnections.new(self)
+        @remote_connections || @mutex.synchronize { @remote_connections ||= RemoteConnections.new(self) }
       end
 
       def stream_event_loop
-        @stream_event_loop ||= ActionCable::Connection::StreamEventLoop.new
+        @stream_event_loop || @mutex.synchronize { @stream_event_loop ||= ActionCable::Connection::StreamEventLoop.new }
       end
 
       # The thread worker pool for handling all the connection work on this server. Default size is set by config.worker_pool_size.
       def worker_pool
-        @worker_pool ||= ActionCable::Server::Worker.new(max_size: config.worker_pool_size)
+        @worker_pool || @mutex.synchronize { @worker_pool ||= ActionCable::Server::Worker.new(max_size: config.worker_pool_size) }
       end
 
       # Requires and returns a hash of all the channel class constants keyed by name.
       def channel_classes
-        @channel_classes ||= begin
-          config.channel_paths.each { |channel_path| require channel_path }
-          config.channel_class_names.each_with_object({}) { |name, hash| hash[name] = name.constantize }
+        @channel_classes || @mutex.synchronize do
+          @channel_classes ||= begin
+            config.channel_paths.each { |channel_path| require channel_path }
+            config.channel_class_names.each_with_object({}) { |name, hash| hash[name] = name.constantize }
+          end
         end
       end
 
       # Adapter used for all streams/broadcasting.
       def pubsub
-        @pubsub ||= config.pubsub_adapter.new(self)
+        @pubsub || @mutex.synchronize { @pubsub ||= config.pubsub_adapter.new(self) }
       end
 
       # All the identifiers applied to the connection class associated with this server.