cron.php leads to a very high cpu usage

cron.php leads to a very high cpu usage

על ידי hugo joe בתאריך
מספר תגובות: 10

I set the cron in Debian as this:

*/15 * * * * /usr/bin/php  /path/to/moodle/admin/cli/cron.php >/dev/null
But it leads to a  very high cpu usage(96%). (ref to attachment)

When I disable the cron, all go back to normal.

Any suggestion?

Best Regards.

Hugo
צרופה top.png
ממוצע דרוגים: -
בתגובה ל: hugo joe

Re: cron.php leads to a very high cpu usage

על ידי Emma Richardson בתאריך
תמונה של Documentation writers תמונה של Particularly helpful Moodlers תמונה של Plugin developers

Cron does tend to spike the cpu but with the exception of when it is running backups, it should only take a few seconds to run.  Do you have Cron running anything else other than the Moodle scripts?

בתגובה ל: hugo joe

Re: cron.php leads to a very high cpu usage

על ידי Frederic Nevers בתאריך

Hi Hugo, 

my guess is automated backup that it causing the high CPU usage. Try to disable it, restart cron and see what happens.

Cheers, 
Fred

בתגובה ל: hugo joe

Re: cron.php leads to a very high cpu usage

על ידי Simon Story בתאריך

You could run the cron the the foreground and see where it spending all it's time.

You can run it in the foreground by doing

$ sudo su www-data

$ /usr/bin/php /path/to/moodle/admin/cli/cron.php

Obviously replace that last bit with where your cron.php actually is..

And see what happens.

בתגובה ל: Simon Story

Re: cron.php leads to a very high cpu usage

על ידי hugo joe בתאריך

I run "/usr/bin/php /path/to/moodle/admin/cli/cron.php", it stops during "Processing module function quiz_cron ...".

Maybe is it  the problem?

צרופה cron ~_2012-07-30_12-51-18.png
בתגובה ל: hugo joe

Re: cron.php leads to a very high cpu usage

על ידי Floyd Saner בתאריך

Hugo,

Emma's about the path is very important.  Use your web server browser to find the exact path to your Moodle directory.  If Moodle is installed as a subdirectory in your home directory, then you should use:

*/15 * * * * /usr/bin/php  /home/moodle/admin/cli/cron.php >/dev/null

There are other commands you can use.  If you have CPanel, search for cron and enter the following in the command line (use your real web address for Moodle). For example, if your Moodle installation is located at http://www.hugo.com/moodle then your cron command should be 

wget -q -O /dev/null http://www.hugo.com/moodle/admin/cli/cron.php

בתגובה ל: Floyd Saner

Re: cron.php leads to a very high cpu usage

על ידי Paul Vaughan בתאריך

Instead of redirecting cron's output to /dev/null, why not redirect it to (for example) /tmp/moodlecron.log ?

You'll see exactly what cron is up to. (And you won't get overrun with log files, as the file will be overwritten each time cron runs.)

בתגובה ל: hugo joe

Re: cron.php leads to a very high cpu usage

על ידי Andrea Bicciolo בתאריך

Looks like cron processes run on top of each other. You could also try the following:

  • run Moodle cron CLI script from within a shell script. Before invoking Moodle cron, the shell script could check if another Moodle cron process is still running, and if yes just exit.
  • assign to Moodle cron a lower priority using nice, such as "nice /usr/bin/php ...."

I'd also follow the suggestion in the thread about keeping cron execution log, at least for a given number of runs, so it is possible to check what happened during cron processing.