mongodb.service dies after running some hours in Ubuntu-CodePudding

I have used mongodb(v3.6.8) for my server(Ubuntu 20.04), it works well for years. Recently,it be killed and failed to restart by systemd after running some days. I restart sysemd, it works for a few hours and dies again. Refer to systemd status:

$ systemctl status mongodb
● mongodb.service - An object/document-oriented database
     Loaded: loaded (/lib/systemd/system/mongodb.service; enabled; vendor preset: enabled)
     Active: failed (Result: signal) since Sat 2022-05-14 22:15:09 UTC; 5h 51min ago
       Docs: man:mongod(1)
    Process: 2463713 ExecStart=/usr/bin/mongod --unixSocketPrefix=${SOCKETPATH} --config ${CONF} $DAEMON_OPTS (code=killed, signal=KILL)
   Main PID: 2463713 (code=killed, signal=KILL)

Anyone know how to solve the problem?

Update log:

$ sudo journalctl -u mongodb.service
-- Logs begin at Wed 2022-05-11 06:03:08 UTC, end at Sun 2022-05-15 04:55:05 UTC. --
May 14 13:01:23 localhost systemd[1]: mongodb.service: Main process exited, code=killed, status=9/KILL
May 14 13:01:23 localhost systemd[1]: mongodb.service: Failed with result 'signal'.
May 14 17:29:35 localhost systemd[1]: Started An object/document-oriented database.
May 14 22:15:09 localhost systemd[1]: mongodb.service: Main process exited, code=killed, status=9/KILL
May 14 22:15:09 localhost systemd[1]: mongodb.service: Failed with result 'signal'.
May 15 04:10:53 localhost systemd[1]: Started An object/document-oriented database.

update: cmd "dmesg -T" show the reason is out of memory.

[Sat May 14 22:15:05 2022] Out of memory: Killed process 2463713 (mongod) total-vm:2486640kB, anon-rss:1133764kB, file-rss:0kB, shmem-rss:0kB, UID:112 pgtables:3240kB oom_score_adj:0

CodePudding user response：

using dmesg -T show the reason why system kill mongodb(updated in qeustion section), it's because "ot ouf memory". Mongodb consumes 2486640kB while my server is 16 GB, so mongodb does not consume too high memory.

The failure is because other programs take too much memory, it's not mongodb problem

CodePudding user response：

You may need to reduce the wiredTiger cacheSizeGB to avoid the mongod to be conisdered high ram consumer and killed unexpectedly by the OS... Considering you have only 16GB RAM , in case you havent set this option it will allocate half of your RAM(8GB) in your mongod.conf file , you can reduce it as follow:

storage:
  wiredTiger:
    engineConfig:
      cacheSizeGB: 4

Afcourse reducing this cache size can impact excution time of your queries...