A singleton ActionCable::Server instance is available via ActionCable.server. It's used by the Rack process that starts the Action Cable server, but is also used by the user to reach the RemoteConnections object, which is used for finding and disconnecting connections across all servers.
Also, this is the server instance used for broadcasting. See Broadcasting for more information.
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[R] | mutex |
Called by Rack to setup the server.
All of the identifiers applied to the connection class associated with this server.
Disconnect all the connections identified by `identifiers` on this server or any others via RemoteConnections.
Adapter used for all streams/broadcasting.
Gateway to RemoteConnections. See that class for details.
# File actioncable/lib/action_cable/server/base.rb, line 36 def restart connections.each(&:close) @mutex.synchronize do # Shutdown the worker pool @worker_pool.halt if @worker_pool @worker_pool = nil # Shutdown the pub/sub adapter @pubsub.shutdown if @pubsub @pubsub = nil end end
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.