Apache service goes down frequently on a Plesk for Linux Server: AH00484: server reached MaxRequestWorkers setting

Symptoms

• Apache constantly goes down with the error below:

  server reached MaxRequestWorkers setting, consider raising the MaxRequestWorkers setting

• At the same time the MaxRequestWorkers value was increased but this does not solve the problem.

• There is high number of CLOSE_WAIT Apache connections on the server as on the following example:

  # netstat -tanp | grep httpd | awk '{print $6}' | sort | uniq -c | sort -n
  ..................
  1700 CLOSE_WAIT

• In an attempt to strace any of the CLOSE_WAIT connection processes only one domain, example.com is shown.

• Websites can be inaccessible with the error below in domain log file:

  (70007)The timeout specified has expired

Cause

Issue with a website code causing high CLOSE_WAIT connections.

Resolution

1. Log into Plesk.
2. Suspend the domain example.com.
3. Restart Apache and PHP handler that is used for example.com domain via Tools & Settings > Services Management.

Then and before enabling the domain again it is required to review the website code with its Developer or in case example.com is a WordPress instance, try to disable the plugins one by one until the culprit of this behavior is found.