Article ID: 125881, created on Jun 15, 2015, last review on Aug 31, 2016

  • Applies to:
  • Plesk 12.5 for Linux
  • Plesk 12.0 for Linux
  • Plesk 11.0 for Linux
  • Plesk 11.5 for Linux


Watchdog reports that the webserver has been restarted:

The Web Server (Apache) service on host is down.
The problem was discovered on Oct 29, 2013 03:00.

There are the following errors in Apache logs - /var/log/apache2/error.logon Debian/Ubuntu,/var/log/httpd/error_log` on CentOS:

    [CET Oct 29 15:00:08] GENERIC: error receiving data -- Resource temporarily unavailable
    [CET Oct 29 15:00:08] 'apache' failed protocol test [generic] at INET[].
    [CET Oct 29 15:00:08] 'apache' trying to restart
    [CET Oct 29 15:00:08] 'apache' stop: /opt/psa/admin/bin/websrvmng
    [CET Oct 29 15:00:11] 'apache' start: /opt/psa/admin/bin/websrvmng

    [Wed Oct 30 14:51:53 2013] [error] [client X.X.X.X] script '/var/www/vhosts/default/htdocs/wp-login.php' not found or unable to stat
    [Wed Oct 30 15:04:37 2013] [error] [client X.X.X.X] File does not exist: /var/www/vhosts/default/htdocs/sitemap.xml

Watchdog /usr/local/psa/var/modules/watchdog/log/monit.logcontains the error:

    [CET Oct 29 15:00:08] 'apache' failed protocol test [generic] at INET[].


Timeout limit is exceeded. The error from watchdog log means that the service did not respond to watchdog control message during the timeout configured in watchdog settings. This does not mean that Apache was down, that can also be confirmed by the Apache error log (there are no restarts at the time when the message was logged in Watchdog logs).


This issue is fixed in Plesk 12.5: Plesk tunes limits automatically for Apache and Nginx depending on domains count.

For Plesk 12.0, the following workaround can be applied.

Note: this workaround works only with Nginx version 1.9.2 or later.

  1. Increase the timeout for Apache service to 20 seconds in watchdog settings -/opt/psa/etc/modules/watchdog/monitrc on Debian/Ubuntu, /usr/local/psa/etc/modules/watchdog/monitrc on CentOS:

    # Apache
    check process apache
            with pidfile "/var/run/"
            start = "/opt/psa/admin/bin/websrvmng --start"
            stop = "/opt/psa/admin/bin/websrvmng --stop"
            if failed host X.X.X.Xport 80 send "GET / HTTP/1.1\r\nHost: X.X.X.X\r\n\r\n" expect "HTTP/1\.[01x] [1-4][0-9]{2} .*\r\n" with timeout 20 seconds then restart
            if 5 restarts within 5 cycles then timeout
            every 1 cycles
            mode active
  2. Add the following into -/etc/nginx/ulimit.global_params - Debian/Ubuntu, etc/sysconfig/nginx - CentOS:

    NGINX_ULIMIT=“-n 4096”
  3. Add the below string into /etc/nginx/ulimit.global_params:

    worker_rlimit_nofile 4096;

Search Words

GENERIC: error receiving data -- Resource temporarily unavailable


Apache Timeout

The Web Server (Apache) service on host is down.


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