cron.php leads to a very high cpu usage

cron.php leads to a very high cpu usage

by hugo joe -
Number of replies: 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
Attachment top.png
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In reply to hugo joe

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

by Emma Richardson -
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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?

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In reply to hugo joe

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

by Emma Richardson -
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And forgive me the stupid question but you don't actually have path/to written in the actual cron script, right?!!

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In reply to hugo joe

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

by Frederic Nevers -

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

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In reply to hugo joe

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

by Simon Story -

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.

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In reply to Simon Story

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

by hugo joe -

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?

Attachment cron ~_2012-07-30_12-51-18.png
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In reply to hugo joe

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

by Visvanath Ratnaweera -
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Hi

The cron.php output definitely has clues to the problem, if one could read it!

Yet another reason to paste the text into the message.
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In reply to hugo joe

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

by Floyd Saner -

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

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In reply to Floyd Saner

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

by Paul Vaughan -

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.)

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In reply to hugo joe

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

by Andrea Bicciolo -

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.

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In reply to hugo joe

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

by hugo joe -

ThanksYes

I am on vication and hard to connect to server. I will check it and report the result.

Best Regards.

Hugo

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