How to Reduce High CPU Usage for "sa-learn" and "spamtrain" Processes in Plesk

If you're experiencing high CPU usage on your Plesk server due to the "sa-learn" or "spamtrain" processes, this guide will help you understand and manage the resource demands of these processes effectively.

What is Plesk?

Plesk is a popular web hosting control panel that provides a suite of tools to manage websites, domains, email, and various services, including spam control. Plesk helps automate these tasks, allowing you to control your server with ease.

Understanding "sa-learn" and "spamtrain"

The sa-learn script is part of SpamAssassin, a tool used to filter and categorize spam. The script trains SpamAssassin by learning patterns in emails marked as spam. If your server has a large volume of emails, "sa-learn" may consume high CPU resources.

Key Terms

• SpamAssassin: An open-source email filtering system used to identify and categorize spam emails based on learned patterns.
• CPU Priority: A setting that defines how much processing power a task should be allocated. Lowering the priority reduces the CPU load for certain processes.

Solution Overview

To manage high CPU usage from "sa-learn," try one of the following methods. Important: Please test all changes in a staging or test environment first and consult the latest documentation to confirm compatibility.

Option 1: Create a Wrapper Script to Lower Process Priority

1. Connect to your server via SSH.
2. Copy the current "sa-learn" script to create a backup:

   cp -a /usr/bin/sa-learn{,.orig}

3. Create a wrapper script that launches "sa-learn" with reduced CPU priority:

   echo "/bin/nice -n 19 /usr/bin/perl -T -w /usr/bin/sa-learn.orig \$@" > /usr/bin/sa-learn

4. Set executable permissions for the wrapper script:

   chmod +x /usr/bin/sa-learn

Note: On Debian-based operating systems, the correct path for the nice command is /usr/bin/nice.

Option 2: Lower Priority of Current "sa-learn" Processes

1. Set the lowest priority (19) for any currently running "sa-learn" processes by running:

   ps auxwf | grep -v grep | grep sa-learn | awk {'print $2'} | xargs -i renice 19 {}

Explanation: In process priorities, values range from -20 to 19, with -20 being the highest and 19 the lowest. Reducing "sa-learn" to 19 lowers its CPU demands.

Option 3: Disable "sa-update" for SpamAssassin

To prevent the "sa-update" process from running automatically, you can disable its cron job:

1. Move the cron files for "sa-update" and "spamassassin" to a different location to disable them:

   mv /etc/cron.daily/60sa-update /root

Important Considerations

• Always test changes in a controlled environment before applying them to a production server.
• Consult the Plesk documentation for the latest version-specific commands and best practices.