All sites are down: nginx worker process is shutting down

Symptoms

• All sites are down;
• Manual restart of nginx resolves the issue;
• The following messages appear after executing of service nginx status command:

  # service nginx status
  . . .
  nginx: worker process is shutting down

• Server running as a container of a Virtuozzo host node;
• Output of dmesg command shows a number of OOM (Out of memory) entries:

  # dmesg
  Out of memory in UB 425: OOM killed process 17660 (nginx) score 27 vm:326900kB, rss:97620kB, swap:189992kB
  Out of memory in UB 425: OOM killed process 17662 (nginx) score 27 vm:326900kB, rss:102428kB, swap:185184kB
  . . .

• 'failcnt' value is not equal 0

  # cat /proc/user_beancounters
  resource held maxheld barrier limit failcnt
  . . .
  physpages 1677634 2621726 0 2621440 1600

Cause

A command for nginx shutdown process comes from the Virtuozhost node due to the fact that nginx consumes a lot of memory resources.

Resolution

Contact host provider to increase the amount of memory allocated to the server.