Background Jobs

A system like ownCloud sometimes requires tasks to be done on a regular basis without requiring user interaction or hindering ownCloud’s performance. For that reason, as a system administrator, you can configure background jobs (for example, database clean-ups) to be executed without any user interaction.

These jobs are typically referred to as Cron Jobs. Cron jobs are commands or shell-based scripts that are scheduled to periodically run at fixed times, dates, or intervals. cron.php is an ownCloud internal process that runs such background jobs on demand.

ownCloud plug-in applications can register actions with cron.php automatically to take care of typical housekeeping operations. These actions can include garbage collecting of temporary files or checking for newly updated files using filescan() on externally mounted file systems.

Cron Jobs

You can schedule Cron jobs in three ways: AJAX, Webcron, or Cron. These can all be configured in the admin settings menu. The default method is to use AJAX. However, the recommended method is to use Cron. The following sections describe the differences between each method.

AJAX

The AJAX scheduling method is the default option. However, it is also the least reliable. Each time a user visits the ownCloud page, a single background job is executed. The advantage of this mechanism, however, is that it does not require access to the system nor registration with a third party service. The disadvantage of this mechanism, when compared to the Webcron service, is that it requires regular visits to the page for it to be triggered.

Note

Especially when using the Activity App or external storages, where new files are added, updated, or deleted one of the two methods below should be preferred.

Webcron

By registering your ownCloud cron.php script address as an external webcron service (for example, easyCron), you ensure that background jobs are executed regularly. To use this type of service, your external webcron service must be able to access your ownCloud server using the Internet. For example:

URL to call: http[s]://<domain-of-your-server>/owncloud/cron.php

Cron

Using the operating system Cron feature is the preferred method for executing regular tasks. This method enables the execution of scheduled jobs without the inherent limitations which the web server might have.

For example, to run a Cron job on a *nix system every 15 minutes, under the default web server user (often, www-data or wwwrun) you must set up the following Cron job to call the cron.php script:

# crontab -u www-data -e
*/15  *  *  *  * php -f /path/to/your/owncloud/cron.php

You can verify if the cron job has been added and scheduled by executing:

# crontab -u www-data -l
*/15  *  *  *  * php -f /path/to/your/owncloud/cron.php

Note

You have to make sure that php is found by cron. Best practice is to expressly add the full path like /usr/bin/php. On some systems it might be necessary to call php-cli instead of php.

Please refer to the crontab man page for the exact command syntax.

Parallel Task Execution

Regardless of the approach which you take, since ownCloud 9.1, Cron jobs can be run in parallel. This is done by running cron.php multiple times. Depending on the process which you’re automating, this may not be necessary. However, for longer-running tasks, such as those which are LDAP related, it may be very beneficial.

There is no way to do so via the ownCloud UI. But, the most direct way to do so, is by opening three console tabs and in each one run php cron.php. Each of these processes would acquire their own list of jobs to process without overlapping any other.

Available Background Jobs

A number of existing background jobs are available to be run just for specific tasks.

Note

These jobs are generally only needed on large instances and can be run as background jobs. If the number of users in your installation ranges between 1,000 and 3,000, or if you’re using LDAP and it becomes a bottleneck, then admins can delete several entries in the oc_jobs table and replace them with the corresponding occ command, which you can see here:

  • OCA\Files_Trashbin\BackgroundJob\ExpireTrash -> occ trashbin:expire
  • OCA\Files_Versions\BackgroundJob\ExpireVersions -> occ versions:expire
  • OCA\DAVCardDAV\SyncJob -> occ dav:sync-system-addressbook
  • OCA\Federation\SyncJob -> occ federation:sync-addressbooks

If used, these should be scheduled to run on a daily basis.

While not exhaustive, these include:

ExpireTrash

The ExpireTrash job, contained in OCA\Files_Trashbin\BackgroundJob\ExpireTrash, will remove any file in the ownCloud trash bin which is older than the specified maximum file retention time. It can be run, as follows, using the OCC command:

occ trashbin:expire

ExpireVersions

The ExpireVersions job, contained in OCA\Files_Versions\BackgroundJob\ExpireVersions, will expire versions of files which are older than the specified maximum version retention time. It can be run, as follows, using the OCC command:

occ versions:expire

SyncJob (CardDAV)

The CardDAV SyncJob, contained in OCA\DAV\CardDAV\SyncJob, syncs the local system address book, updating any existing contacts, and deleting any expired contacts. It can be run, as follows, using the OCC command:

occ dav:sync-system-addressbook

SyncJob (Federation)

OCAFederationSyncJob

It can be run, as follows, using the OCC command:

occ federation:sync-addressbooks