How do I know if I am running Puma in cluster mode?

Question

There's no explicit option for it in the config-- how can I know whether my Puma instance is running in cluster mode or not?

Answer 1

If Puma is running in cluster mode, you should see

[12345] Puma starting in cluster mode...

Where "12345" is the process ID of the master Puma process that forks to create workers.

You can also run ps x | grep puma and check the output-- it may look similar to the following:

user@computer$ ps x | grep puma
12315 pts/2    Sl+    0:03 puma 2.11.3 (tcp://0.0.0.0:3000) [rails]
12386 pts/2    Sl+    0:00 puma: cluster worker 0: 12315 [rails]
12391 pts/2    Sl+    0:00 puma: cluster worker 1: 12315 [rails]