[Owncloud] Background Jobs

[Jan-Christoph Borchardt]

Awesoooome! Does that mean that step-by-step, all the »refresh« and
»rescan« buttons can go away?

Just one thing: You say »there are four options: using the systems
cron feature, using a webcron service, using AJAX or not using
background jobs at all.«
Why even have the possibility to deactivate it? It’s a great function
which improves the experience silently, as with doing away with the
need for refresh buttons. And since doing it via AJAX is a good
default there’s no reason to not just do it like that always – or is
there?


On Sat, Aug 11, 2012 at 7:07 AM, Jakob Sack <mail at jakobsack.de> wrote:
> Hi,
>
> yesterday I pushed the new Background Jobs system to ownCloud master. As you
> can guess from the name, this feature allows ownCloud to do certain tasks in
> the background without blocking the UI. It also makes it possible to execute
> some tasks without any need of user interaction, for example fetching news
> while the user is on holidays.
> From a users perspective there is not much to pay attention to, background
> jobs tries to get out of the way as much as possible. On the other hand,
> administrators can use the settings interface to set the way background jobs
> are executed. There are four options: using the systems cron feature, using
> a webcron service, using AJAX or not using background jobs at all. Using the
> systems cron feature is the preferred way. It allows regular executed jobs
> without the limitations the web server may have. The second recommended
> option is the webcron implementation. By registering your ownCloud cron.php
> address at a webcron service like [1] you ensure that background jobs will
> be executed regularly. Using AJAX is the default option, although the least
> reliable. Every time a  user visits the page a single background job gets
> executed. The disadvantage of this solution compared to the webcron service
> is that it requires regular visits of the page. The reason for making this
> option the default is that this solution simply does not require access to
> the system or registration on some third party service.
> When you are implementing background jobs in your app, please be aware of
> the difference between the AJAX/Webcron and the cron implementation! The
> AJAX/Webcron implementation gets started by your-favorite-web-server, so you
> might have some limitations on execution time or memory. These limitations
> do not affect the system cron implementation, which calls php from the
> command line. As a consequence, you should split large tasks when not using
> system cron. You can check whether the app has been started by systems cron
> by checking if OC::$CLI is set to true.
> If you want to  use background jobs in your app, you have to register them
> in appinfo/app.php by calling OCP\BackgroundJobs::addRegularTask( $class,
> $method ).
> The first app featuring a background job is the news app being implemented
> by Alessandro Cosentino (zimba12). If you want to use background jobs in
> your app, have a look at the apps:newsapp repository first! There you will
> not only find a working example, but also a strategy of how to deal with the
> different requirements of AJAX/Webcron and the system cron.
> Regards,
>
> Jakob
>
> 1: http://www.easycron.com/
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