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Cron assists some of Moodle's modules to perform tasks on a scheduled basis. For example, the cron process might tell Moodle to check all discussion forums so it can mail out copies of new posts to people who have subscribed to that forum.  
{{Installing Moodle}}
The Moodle 'cron' process is a PHP script (part of the standard Moodle installation) that must be run regularly in the background.  The Moodle cron script runs different tasks at differently scheduled intervals.


The primary Moodle script that does all this is located in the admin directory, and is called cron.php. However, it can not tell itself to run, so you need to set up a mechanism where this script is run regularly (eg every five or ten minutes). This provides a "heartbeat" so that the script can perform functions at periods defined by each module. This kind of regular mechanism is known as a '''cron service'''. The service can be part of a webhost or can be something run from a different server or computer.
'''IMPORTANT: Do not skip setting up the cron process on your server for your Moodle. Your site will not work properly without it'''


==Overview of cron==
A special program (typically called - not surprisingly - 'cron') is used to run the Moodle cron script at a regular interval.  The Moodle cron script runs tasks include sending mail, updating Moodle reports, RSS feeds, activity completions, posting forum messages and other tasks. Since different tasks have different schedules, not every task will run in Moodle when the cron script is triggered.
===Script overview===


The cron.php script looks through the mdl_modules table (assuming the default table prefix is mdl_) in the Moodle database for modules scheduled to have their cron functions run; it then looks in each such module directory for a function called module-name_cron in the lib.php file and runs it.  It also looks through the mdl_block table for blocks scheduled for their cron methods (object functions) to be run; it then, for each such block, runs the cron method for a new object associated with that block (I'm omitting details for the benefit of non-programmers; programmers can read admin/cron.php for themselves). These files (the lib.php files and the files where the block classes are defined) can contain cleanup functions, email functions or anything that needs to be run on a regular basis. For example, cron will trigger the system to create the backups of courses at the time specified in the administration settings. It also triggers any messaging module or forum email notifications, but not all functions are called each time the cron runs. Some functions, such as unenrolling students who have not logged in or deleting old copies of log files, are only run occasionally. The cron.php file has a section which will randomly call these core tasks approximately 1 in 5 times the cron runs.
The cron program (that runs the Moodle script) is a core part of Unix based systems (including Linux and OSX) being used to run all manner of time-dependent services. On Windows the simplest solution is to create a task in the Windows Task Scheduler and set it to run at regular intervals. On shared hosting, you should find the documentation (or ask support) how cron is configured.  


===Invocation===
Essentially, the task involves adding a single command to the list of cron activities on your system. On Unix based systems this list is a file called a 'crontab' which all users have.   
There are now (1.9) a number of options with respect to how one can invoke cron.php. First off, one can password the invocation of cron.php via its URL. This means whether one calls the script via a browser through an application like wget or curl, or via your own code to the web daemon, the script will not run unless the password is provided, and this would be transmitted in clear text.


You can also now bar invocation by URL be selecting cronclionly. This sets Moodle so that cron.php cannot be invoked by the Moodle URL. See the illustration below. (Menu: Security/Site Policies)
== General discussion ==


[[Image:Moodelcronadmin.png]]
See the later sections for your server type; this section contains some general background information.  


While this is identified as CLI (command line interface) this is a bit misleading in that it does not mean that you have to be sitting at a shell account entering the command. If you enable this switch you can invoke cron.php through any set of batch or script files you wish,  but it must be invoked via its correct location in the operating systems file structure.  This can be especially frustrating for those not used to scripting in that environment is not typically provided.
There are essentially two steps to implementing cron:
# identifying the correct command to run
# finding the right place on your system to put the command


===Cron service location and timing===
=== Working out the Moodle cron command ===
Note that the machine performing the cron '''does not need to be the same machine that is running Moodle'''. For example, if you have a limited web hosting service that does not have a cron service, then you might choose to run cron on another server or on your home computer. All that matters is that the cron.php file is called regularly.


The load of this script is not very high, so 5 minutes is usually reasonable, but if you're worried about it you can reduce the time period to something like 15 minutes or even 30 minutes. It's best not to make the time period too long, as delaying mail-outs can slow down activity within the course. Remember that mail-outs also wait for the editing time to expire before being queued for sending.
Moodle has two different ways to deploy cron which use different scripts within the Moodle install. These are as follows...
# The CLI (command line interpreter) script. This will be at the path <pre>/path/to/moodle/admin/cli/cron.php</pre> If in doubt, this is the correct script to use. This needs to be run by a 'PHP CLI' program on your computer. So the final command may look something like <pre>/usr/bin/php /path/to/moodle/admin/cli/cron.php</pre> You can (and should) try this on your command line to see if it works.
# The web based script. This needs to be run from a web browser and will be accessed via a web url something like '''http://your.moodle.site/admin/cron.php'''. You can find command line based web browser (e.g. wget) so the final command may look like <pre>/usr/bin/wget http://your.moodle.site/admin/cron.php</pre> This has the advantage that it can be run from *anywhere*. If you can't get cron to work on your machine it can be run somewhere else.


===Testing cron and manual trigger===


First, test that the script works by running it directly from your browser: ''<nowiki>http://example.com/moodle/admin/cron.php</nowiki>''
=== Finding the right place to put the command ===


If cron is called from the command line by any user logged in to your Moodle it will create a temporary admin environment in order to run and then log the user out. You can disable command line running of cron by disabling the appropriate section in the cron.php file.
This really does depend on the system you are using and you should find and read the documentation for your platform or hosting. In most cases getting the Moodle cron to run consists of establishing the correct command (above) and then adding it, and the time to run the command, to some sort of file. This might be either through a specific user interface or by editing the file directly.


Now, you need to set up some of way of running the script automatically and regularly.
If using the CLI version you also need to make sure that the cron process is run as the correct user. This is not an issue with the web version.  


==Managing Cron on Windows systems==
Example... installing cron on Ubuntu/Debian Linux. Assuming logged in as root..


There are two different ways for setting-up Moodle cron.php on Windows systems:
''use the crontab command to open a crontab editor window for the www-data user. This is the user that Apache (the web server) runs as on Debian based systems''
<pre>
$ crontab -u www-data -e
</pre>
''This will open an editor window. To run the cli cron script every 15 minutes, add the line:''
<pre>
*/15 * * * * /usr/bin/php  /path/to/moodle/admin/cli/cron.php >/dev/null
</pre>
NOTE: the final '''>/dev/null''' sends all the output to the 'bin' and stops you getting an email every 15 minutes.


*Use the '''Moodle Cron package'''. The simplest way is to use this little package [http://download.moodle.org/download.php/sourceforge/MoodleCron-Setup.exe MoodleCron-Setup.exe], which makes this whole thing very easy by installing a small Windows service. Run it and forget about it! :-)
== Setting up cron on your system ==
*Use a '''Scheduled Task'''. If you prefer to use the built-in Windows Scheduler or are having trouble with moodle-cron-for-windows package, you can use wget for windows or php from the command line and setup a scheduled task. Just follow these steps:
** Choose either the '''php.exe/php-win.exe (command line binary)''' or '''wget'''
Choose the information for your server type:
::The php.exe or php-win.exe binary (for PHP version 5 or later) is installed in your php folder (e.g. c:\php) will give you better performance when running the cron script.
::If you want to use wget, download a compiled version of wget for windows from the native GNU Win32 ports (http://unxutils.sourceforge.net/), from Heiko Herold's wget for windows page (http://xoomer.virgilio.it/hherold/) or Bart Puype's wget for windows page (http://users.ugent.be/~bpuype/wget/). If you use Heiko Herold's package, copy all of the .DLL files to your C:\Windows\system32 directory. Copy the wget.exe file to c:\windows (this makes sure wget is always in the search path).
:* Setup a '''Scheduled Task'''.
:: - Go to Start >> Control Panel >> Scheduled Tasks >> Add Scheduled Task.
:: - Click "Next" to start the wizard:
:: - Click in the "Browse..." button and browse to c:\php\php.exe or c:\windows\wget.exe and click "Open"
:: - Type "Moodle Cron" as the name of the task and select "Daily" as the schedule. Click "Next".
:: - Select "12:00 AM" as the start time, perform the task "Every Day" and choose today's date as the starting date. Click "Next".
:: - Enter the username and password of the user the task will run under (it doesn't have to be a priviledged account at all). Make sure you type the password correctly. Click "Next".
:: - Mark the checkbox titled "Open advanced properties for this task when I click Finish" and click "Finish".
:: - In the new dialog box, type the following in the "Run:" text box: <pre>c:\windows\wget.exe -q -O NUL http://my.moodle.site/moodle/admin/cron.php</pre> or <pre>c:\php\php-win.exe -f c:\moodle\admin\cron.php</pre> Replace "c:\moodle" with the path to your moodle directory or "my.moode.site" with the name of your site.<br><br>
:: - Click on the "Schedule" tab and there in the "Advanced..." button.
:: - Mark the "Repeat task" checkbox and set "Every:" to 5 minutes, and set "Until:" to "Duration" and type "23" hours and "59" minutes.
:: - Click "OK" and you are done.
* '''Test your scheduled task'''. You can test that your scheduled task can run successfully by clicking it with the right button and chosing "Run". If everything is correctly setup, you will briefly see a DOS command window while wget/php executes and fetches the cron page and then it disappears. If you refresh the scheduled tasks folder, you will see the ''Last Run Time column'' (in detailed folder view) reflects the current time, and that the Last Result column displays "0x0" (everything went OK). If either of these is different, then you should recheck your setup.
* '''Logging cron output'''. You may want to log the output of the cron script as it executes, in case you see the job is producing errors, backups are not being completed or users are experiencing delays in receiving forum emails. To do this, adjust the command so that it uses the php.exe and stores the output in a file called (for example c:\moodle\admin\cron.log). Here is an example of the php.exe command:
<pre>c:\php\php.exe -f c:\moodle\admin\cron.php > c:\moodle\admin\cron.log</pre>


==Managing cron on web hosting services==
*[[Cron with Unix or Linux]]- Cron services on various UNIX and Linux flavored operating systems.
*[[Cron with Windows OS]] - Cron services in Windows
*''Apple OSX'' - use the built-in 'crontab' service which is exactly the same as [[Cron with Unix or Linux]]. However, you might want to do it the 'Apple way' using launchd - see [[Cron with MAC OS X]]
*[[Cron with web hosting services]]- Cron services in various web hosting examples.


Your web-based control panel may have a web page that allows you to set up a cron service process.
Here are some more instructions for specific hosts (please check that these are up to date):


===CPanel cron service===
*[[Cron on 1and1 shared servers]]
If you are using CPanel, login then look for "Advanced" category towards the bottom of the page. Click on Cron Jobs -> Advanced (Unix style). Enter the following for the cron to run every 30 minutes.


Email address for output: emailaddress@mydomain.con
== Using third party cron service ==
  Minute:*/30
   
Hour:*
Besides using cron hosted on your own server, you may use third party cron service (usually called webcron):
Day:*
Month:*
Weekday:*
<nowiki>Command: wget -q -O /dev/null http://www.mydomain.com/moodle/admin/cron.php</nowiki>


Click Commit Changes. Check your email for the output.  
*[https://www.easycron.com EasyCron] - A webcron service provider that eliminates the need of crontab or other task schedulers to set cron job.


[[Image:Cpanel-cron-setup.JPG]]
=== Cron settings in Moodle ===


===Other systems cron service===
There are settings within Moodle that control aspects of cron operation:
For other systems, look for a button called "Cron jobs". In there you can put the same sort of Unix commands as listed below.


*[[Cron settings]] - Moodle cron process password and CLI settings


If you don't have permissions to run the 'wget' command on the server, you can use this php command:
===Remote cron===
Using the 'web based' version of cron it is perfectly ok to place the cron process on a different machine to the Moodle server. For example, the cron service on a Unix server can invoke the cron web 'page' on a Windows based Moodle server.


/usr/local/bin/php -q /real/path/to/script/admin/cron.php
==Running cron for several Moodle servers==
* If both your servers are web servers, and they jointly serve one Moodle instance (in some sort of a cluster), then only one server should run the Moodle cron job.


For example:  
* If those two web servers run different Moodle instances, then each Moodle instance needs a cron job. (Even a single Apache web server can run different Moodle instances on different domains by using its virtual hosts capability [https://httpd.apache.org/docs/2.2/vhosts/index.html https://httpd.apache.org/docs/2.2/vhosts/index.html].)


/usr/local/bin/php -q /home/username/public_html/moodle/admin/cron.php
* If you mean this setup, [https://moodle.org/mod/forum/discuss.php?d=238005 https://moodle.org/mod/forum/discuss.php?d=238005], then it is _one_ web server and _one_ Moodle instance. Then one cron job is the right answer.


If you don't know what is the real path of your Moodle folder you can use the PHP command realpath.
* See [https://moodle.org/mod/forum/discuss.php?d=242499 this forum thread].
 
Another alternative, if you do not have permission to run the 'wget' command, may be to use a curl command.
 
For example:
 
curl --silent --compressed http://mydomain.com/moodle/admin/cron.php
 
==Using a cron command line in Unix==
 
There are different command line programs you can use to call the page from the command line. Not all of them may be available on a given server.
 
For example, you can use a Unix utility like 'wget':
 
wget -q -O /dev/null <nowiki>http://example.com/moodle/admin/cron.php</nowiki>
 
Note in this example that the output is thrown away (to /dev/null).
 
A number of users of Moodle have found that 'wget' sometimes fails. Especially if you have trouble with email digests not being sent on a daily basis to all users, an alternative command that solves the problem is:
 
php <nowiki>http://example.com/moodle/admin/cron.php</nowiki>
 
The same thing using lynx:
 
lynx -dump <nowiki>http://example.com/moodle/admin/cron.php</nowiki> > /dev/null
 
Note in this example that the output is thrown away (to /dev/null).
 
Alternatively, you can use a standalone version of PHP, compiled to be run on the command line. The disadvantage is that you need to have access to a command-line version of php. The advantage is that your web server logs aren't filled with constant requests to cron.php and you can run at a lower I/O and CPU priority.
 
/opt/bin/php /web/moodle/admin/cron.php
 
Example command to run at lower priority:
 
  ionice -c3 -p$$;nice -n 10 /usr/bin/php /moodle/admin/cron.php > /dev/null
 
===Using the crontab program on Unix===
 
All that Cpanel does is provide a web interface to a Unix utility known as crontab. If you have a command line, you can set up crontab yourself using the command:
 
crontab -e
 
and then adding one of the above commands like:
 
*/30 * * * * wget -q -O /dev/null <nowiki>http://example.com/moodle/admin/cron.php</nowiki>
 
The first five entries are the times to run values, followed by the command to run. The asterisk is a wildcard, indicating any time. The above example means run the command ''wget -q -O /dev/null...'' every 30 minutes (*/30), every hour (*), every day of the month (*), every month (*), every day of the week (*).
 
The "O" of "-O" is the capital letter not zero, and refers the output file destination, in this case "/dev/null" which is a black hole and discards the output. If you want to see the output of your cron.php then enter its url in your browser.
 
* [http://linuxweblog.com/node/24 A basic crontab tutorial]
* [http://www.freebsd.org/cgi/man.cgi?query=crontab&apropos=0&sektion=5&manpath=FreeBSD+6.0-RELEASE+and+Ports&format=html Online version of the man page]
 
For '''beginners''', "EDITOR=nano crontab -e" will allow you to edit the crontab using the [http://www.nano-editor.org/dist/v1.2/faq.html nano] editor. Ubuntu defaults to using the nano editor.
 
Usually, the "crontab -e" command will put you into the 'vi' editor. You enter "insert mode" by pressing "i", then type in the line as above, then exit insert mode by pressing ESC. You save and exit by typing ":wq", or quit without saving using ":q!" (without the quotes). Here is an [http://www.unix-manuals.com/tutorials/vi/vi-in-10-1.html intro] to the 'vi' editor.


==See also==
==See also==
* [http://www.coursebit.net/moodle-cron-job/ All About the Moodle Cron Job]
* [http://en.wikipedia.org/wiki/Cron Wikipedia article on cron function]


Using Moodle forum discussions:
Using Moodle forum discussions:
Line 149: Line 88:
*[http://moodle.org/mod/forum/discuss.php?d=97684 Cronjob Question]
*[http://moodle.org/mod/forum/discuss.php?d=97684 Cronjob Question]
*[http://moodle.org/mod/forum/discuss.php?d=97457 Slow cron : avoiding simultaneous cron]
*[http://moodle.org/mod/forum/discuss.php?d=97457 Slow cron : avoiding simultaneous cron]
 
*[http://moodle.org/mod/forum/discuss.php?d=117168 Visibility of cron.php]
[[Category:Installation]]
*[http://moodle.org/mod/forum/discuss.php?d=139263#p609060 How to log the output of a Scheduled Task on Windows] - this discussion explains a nice trick that can be very useful when you are experiencing problems with your Windows Scheduled Task and you need to log the output of the Scheduled Task to a log file.


[[es:Cron]]
[[es:Cron]]
[[fr:Cron]]
[[fr:Cron]]
[[nl:Cron]]
[[sk:Cron]]
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[[ja:Cron]]
[[ja:Cron]]

Latest revision as of 21:16, 13 October 2014

The Moodle 'cron' process is a PHP script (part of the standard Moodle installation) that must be run regularly in the background. The Moodle cron script runs different tasks at differently scheduled intervals.

IMPORTANT: Do not skip setting up the cron process on your server for your Moodle. Your site will not work properly without it

A special program (typically called - not surprisingly - 'cron') is used to run the Moodle cron script at a regular interval. The Moodle cron script runs tasks include sending mail, updating Moodle reports, RSS feeds, activity completions, posting forum messages and other tasks. Since different tasks have different schedules, not every task will run in Moodle when the cron script is triggered.

The cron program (that runs the Moodle script) is a core part of Unix based systems (including Linux and OSX) being used to run all manner of time-dependent services. On Windows the simplest solution is to create a task in the Windows Task Scheduler and set it to run at regular intervals. On shared hosting, you should find the documentation (or ask support) how cron is configured.

Essentially, the task involves adding a single command to the list of cron activities on your system. On Unix based systems this list is a file called a 'crontab' which all users have.

General discussion

See the later sections for your server type; this section contains some general background information.

There are essentially two steps to implementing cron:

  1. identifying the correct command to run
  2. finding the right place on your system to put the command

Working out the Moodle cron command

Moodle has two different ways to deploy cron which use different scripts within the Moodle install. These are as follows...

  1. The CLI (command line interpreter) script. This will be at the path
    /path/to/moodle/admin/cli/cron.php
    If in doubt, this is the correct script to use. This needs to be run by a 'PHP CLI' program on your computer. So the final command may look something like
    /usr/bin/php /path/to/moodle/admin/cli/cron.php
    You can (and should) try this on your command line to see if it works.
  2. The web based script. This needs to be run from a web browser and will be accessed via a web url something like http://your.moodle.site/admin/cron.php. You can find command line based web browser (e.g. wget) so the final command may look like
    /usr/bin/wget http://your.moodle.site/admin/cron.php
    This has the advantage that it can be run from *anywhere*. If you can't get cron to work on your machine it can be run somewhere else.


Finding the right place to put the command

This really does depend on the system you are using and you should find and read the documentation for your platform or hosting. In most cases getting the Moodle cron to run consists of establishing the correct command (above) and then adding it, and the time to run the command, to some sort of file. This might be either through a specific user interface or by editing the file directly.

If using the CLI version you also need to make sure that the cron process is run as the correct user. This is not an issue with the web version.

Example... installing cron on Ubuntu/Debian Linux. Assuming logged in as root..

use the crontab command to open a crontab editor window for the www-data user. This is the user that Apache (the web server) runs as on Debian based systems

$ crontab -u www-data -e

This will open an editor window. To run the cli cron script every 15 minutes, add the line:

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

NOTE: the final >/dev/null sends all the output to the 'bin' and stops you getting an email every 15 minutes.

Setting up cron on your system

Choose the information for your server type:

Here are some more instructions for specific hosts (please check that these are up to date):

Using third party cron service

Besides using cron hosted on your own server, you may use third party cron service (usually called webcron):

  • EasyCron - A webcron service provider that eliminates the need of crontab or other task schedulers to set cron job.

Cron settings in Moodle

There are settings within Moodle that control aspects of cron operation:

Remote cron

Using the 'web based' version of cron it is perfectly ok to place the cron process on a different machine to the Moodle server. For example, the cron service on a Unix server can invoke the cron web 'page' on a Windows based Moodle server.

Running cron for several Moodle servers

  • If both your servers are web servers, and they jointly serve one Moodle instance (in some sort of a cluster), then only one server should run the Moodle cron job.
  • If those two web servers run different Moodle instances, then each Moodle instance needs a cron job. (Even a single Apache web server can run different Moodle instances on different domains by using its virtual hosts capability https://httpd.apache.org/docs/2.2/vhosts/index.html.)

See also

Using Moodle forum discussions: