[Owncloud] Background Jobs

Tue Aug 14 23:56:32 UTC 2012

@Jakob: maybe I am missing something here, but is there a way for the
app developer to specify how often the job is executed?

Thanks,
Alessandro

On Mon, Aug 13, 2012 at 9:50 AM, Klaas Freitag <freitag at owncloud.com> wrote:
> On 13.08.2012 16:23, Jakob Sack wrote:
>>
>> Hi Klaas,
>>
>> maybe I chose the wrong words: To disable background jobs you do not
>> have to edit the program code but you must set the appconfig value
>> core:backgroundjobs_mode to "none".
>
> Ah, ok, sorry...
>
> IMO the important point is that an update does not kick out such things, but
> you probably have taken care :)
>
> Thanks,
>
> Klaas
>
>
>>
>> Am 13.08.2012 11:49, schrieb Klaas Freitag:
>>>
>>> On 12.08.2012 11:29, Jakob Sack wrote:
>>>>
>>>> I removed the option from the UI. In the program code the option "none"
>>>> is still usable.
>>>
>>> Come on, isn't that the worst of all possible solutions? ;-)
>>>
>>> Changing the program code is not the best way to do app configuration
>>> as the change will be gone with the next update. Why not put an value
>>> in config.php if we do not want a GUI option?
>>>
>>> I think there should be an option to set up ownCloud completely stand
>>> alone, without having the system seeking out for other web services.
>>>
>>> Or do I get something wrong?
>>>
>>> Thx,
>>> Klaas
>>>
>>>>
>>>> Am 11.08.2012 23:08, schrieb Jan-Christoph Borchardt:
>>>>>
>>>>> Ah sorry, I phrased it wrong. I didn’t mean »just use AJAX all the
>>>>> time and remove the option for cron jobs«, I meant »AJAX is always
>>>>> available and has no negative effect, so let’s just not have an option
>>>>> to deactivate background jobs«.
>>>>> Of course if the server supports it, cron should be used.
>>>>>
>>>>>
>>>>> TL;DR: Nice, let’s remove the option to deactivate background jobs.
>>>>>
>>>>>
>>>>>
>>>>> On Sat, Aug 11, 2012 at 2:03 PM, Jakob Sack <mail at jakobsack.de> wrote:
>>>>>>
>>>>>> Hi Jan,
>>>>>>
>>>>>> thank you for the praise.
>>>>>> as far as I know there is no reason for completely disabling
>>>>>> background
>>>>>> jobs.
>>>>>> I strongly disaggree with you regarding your second argument. Using
>>>>>> AJAX
>>>>>> always is a bad idea. Exactly spoken, there are at least two problems
>>>>>> with
>>>>>> the ajax solution: if you installed ownCloud on a shared web hosting
>>>>>> service
>>>>>> and use it alone or with your family chances are high that there are
>>>>>> periods
>>>>>> with no one being online. Then you could miss news that are meant
>>>>>> to be
>>>>>> fetched every now and then. In this case a webcron serice would be
>>>>>> perfect.
>>>>>> On the other hand a large setup with several hundred users - we both
>>>>>> know
>>>>>> that they exist - should not be bombed with another hundred requests
>>>>>> every
>>>>>> minute. In this case it's better to use the systems cron service
>>>>>> which does
>>>>>> not have the limitations apaches processes might have.
>>>>>> regards,
>>>>>>
>>>>>> Jakob
>>>>>>
>>>>>> Am 11.08.2012 20:30, schrieb 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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