在 Ruby on Rails v5.2 和 Puma v4 中，在 logrotate 时重新启动 puma 后，不必要的工人继续存在

Question

We are uses Ruby on Rails v5.2 and Puma v4, rotating the Rails application log with logrotate, and restarting puma when it is rotated.

We uses puma restart with pumactl phased-restart , but we used to send SIGUSR1 signal to restart it.

Specifically, it is the following code.

test -s $pid && kill -USR1 "$(cat /path/to/app/tmp/pids/puma.pid)"

Refs: https://github.com/puma/puma/blob/master/docs/restart.md

Although puma restarts without any problem for a while, after several restarts, unnecessary workers will be left as shown below. In the following, there are two worker 7s. Perhaps pid = 15241 seems to be an unnecessary worker.

$ ps aux | grep [p]uma
username     10096 22.8  3.0 3357088 1012940 ?     Sl   13:01   1:12 puma: cluster worker 0: 14749 [app]
username     10135 26.6  3.0 3562476 1016716 ?     Sl   13:01   1:22 puma: cluster worker 1: 14749 [app]
username     10196 17.9  3.4 3688000 1145328 ?     Sl   13:01   0:54 puma: cluster worker 2: 14749 [app]
username     10243 15.6  3.9 3753452 1287424 ?     Sl   13:01   0:46 puma: cluster worker 3: 14749 [app]
username     10325 16.8  3.6 3758280 1189004 ?     Sl   13:01   0:48 puma: cluster worker 4: 14749 [app]
username     10381 15.9  3.1 3423564 1034904 ?     Sl   13:01   0:45 puma: cluster worker 5: 14749 [app]
username     10420 16.6  3.2 3689844 1070112 ?     Sl   13:01   0:46 puma: cluster worker 6: 14749 [app]
username     10464 21.9  2.6 3155296 888148 ?      Sl   13:01   0:59 puma: cluster worker 7: 14749 [app]
username     14749  0.0  0.0 216884 20340 ?        Sl    7月19   0:56 puma 4.0.0 (tcp://0.0.0.0:9292) [app]
username     15241 60.7  9.2 5273704 3049272 ?     Sl   11:02  75:20 puma: cluster worker 7: 14749 [app]

My question is, I would like to know how to restart puma without leaving unnecessary workers.

Or I would like to know if there is a way to find out what each worker is doing to find out why this is the case.

Or, please tell me if there is a way to put in logs etc and check the situation after the fact.

The main usage version is as follows.

• Ruby: 2.4.2
• Ruby on Rails: 5.2.2.1
• Puma: 4.0.0

As mentioned above, puma restarts are performed by pumactl phased-restart , but the situation was the same by sending SIGUSR1 signal.

Answer 1

Puma's phased-restart is a rolling restart. Each worker is restarted one by one. The other thing, is that the command returns before the workers have been restarted.

I also use phased-restart , but I don't have logrotated restart Puma, but instead just have it copytruncate the log files. It allows the file descriptors to remain the same. Now, maybe there are unforeseen problems with my approach, but I haven't seen any issues yet.

Example logrotate config:

/path/to/rails/app/shared/log/*.log {
  compress
  copytruncate
  daily
  dateext
  dateformat .%Y%m%d
  dateyesterday
  delaycompress
  missingok
  notifempty
  rotate 36
  su app_user app_user
}