restartsrv_dovecot causes high loads

[microeuropa]

Hello,

I'm having an issue on some servers, but one in special where restartsrv_dovecot will cause
server high loads and can even hung the machine with load averages of 400+...

top - 11:38:24 up 12 days, 17:20, 6 users, load average: 19.43, 19.20, 10.93
Tasks: 640 total, 3 running, 634 sleeping, 0 stopped, 3 zombie
%Cpu(s): 11.8 us, 3.8 sy, 0.4 ni, 71.4 id, 12.5 wa, 0.0 hi, 0.0 si, 0.0 st
MiB Mem : 5958.5 total, 307.8 free, 2595.2 used, 3055.5 buff/cache
MiB Swap: 5776.0 total, 5617.2 free, 158.8 used. 2774.4 avail Mem

PID PPID TIME+ %CPU %MEM USER PR NI S VIRT RES UID COMMAND
28708 28502 0:09.19 100.0 0.2 root 20 0 R 47.4m 11.6m 0 /usr/local/cpanel/scripts/restartsrv_dovecot

This is the result of a top command... you can see that is running for 9 minutes and almost at 100% cpu usage!!!

a pstree showed me the running processes for dovecot

|-dovecot-+-anvil
| |-auth
| |-config
| |-378*[imap]
| |-2*[imap-login]
| |-lmtp
| |-log
| |-pop3
| |-2*[pop3-login]
| `-quota-status

anyone experienced the same issue?

Cheers,
Hugo Ferreira

 

[cPanelLauren]

Hi @microeuropa

That's showing 378 IMAP logins which tells me when you're restarting dovecot every time 378 new processes are spawned to log back into user mailboxes. How many email users do you have on the system? Does the load drop after some time?

 

[microeuropa]

Hello,

It gets really high during restartsrv_dovecot but after tends to get down. Even in high load hours
keeps between 0.8 and 1.5 load average that is great. But every time restartsrv_dovecot it goes
to 30, 50, 80, 100, 150 load average... why does this happens?

Cheers,
Hugo Ferreira

 

[cPanelLauren]

Hi @microeuropa

My assumption on this is that when you restart dovecot not only does the process need to restart but all of those connections need to be re-established. This is just a guess though you might see some insights as to what's occurring to cause the load watching top or the processes started after the restart.