Symptoms
High CPU usage for sa-learn and spamtrain processes in the Plesk server.
Cause
Since the sa-learn script is used by spamassassin to learn the specific properties of spam from a folder that supposedly contains only spam emails.
CPU usage of the sa-learn process depends on the number of emails in mailboxes and their size. In turn, if the number of emails is huge - CPU over usage is expected.
Resolution
To work around the issue, use one of the following solutions:
Create a wrapper script that will launch sa-learn with low priority:
-
Connect to the server using SSH.
-
Use nice or ionice utilities to decrease the priority of
sa-updatefrom the cron tasks. -
Create a wrapper file which will execute
sa-learnwith the lowest CPU priority:# cp -a /usr/bin/sa-learn{,.orig}
# echo "/bin/nice 19 /usr/bin/perl -T -w /usr/bin/sa-learn.orig $@" > /usr/bin/sa-learn
# chmod +x /usr/bin/sa-learnNote: In Debian based OS the correct path is
/usr/bin/nice
Lower the priority of the currently running processes:
Set the lowest priority to the currently running sa-learn processes execute the following:
# ps auxwf | grep -v grep | grep sa-learn | awk {'print $2'} | xargs -i renice 19 {}
Note: Process priority values range from -20 to 19. A process with the nice value of -20 is considered to be on top of the priority. And a process with nice value of 19 is considered to be low on the priority list.
Disable the sa-update functionality:
Disable the sa-update execution by moving 60sa-update and spamassassin files from /etc/cron.daily to a different location:
# mv /etc/cron.daily/60sa-update /root