Manual:Job queue/pl

W MediaWiki 1.6 została wprowadzona kolejka zadań (ang. job queue) do wykonywania długotrwałych zadań w sposób asynchroniczny. Celem kolejki zadań jest umożliwienie wykonywania wielu zadań przy wykorzystaniu przetwarzania wsadowego.

Set up
Można również ustawić $wgJobRunRate na 0, a następnie użyć procesu crona do opróżnienia kolejki zadań. Odbywa się to poprzez uruchomienie maintenance/runJobs.php. For instance, if you were to use cron to run the jobs every day at midnight you would enter in your crontab file:

Job execution on page requests
By default, each time a page request runs, one job is taken from the job queue and executed. This behavior is controlled by the configuration variable. Setting this variable to, will run a job on each request. Setting this variable to a number between  and   will execute a job on average every   requests. Setting this variable to 0 will disable the execution of jobs during page requests completely, but you should run manually or periodically.

When enabled, jobs will be executed opening a socket and making an internal HTTP request to an unlisted special page: SpecialRunJobs.php. See the asynchronous section.

Performance issue
If the performance burden of this is too great, you can reduce by putting something like this in your LocalSettings.php:

Manual usage
There is also a way to empty the job queue manually, for example after changing a template that's present on many pages. Simply run the  maintenance script. For example:

Asynchronous
The configuration variable has been added to force the execution of jobs synchronously, in scenarios where making an internal HTTP request for job execution is not wanted.

When running jobs asynchronously, it will open an internal HTTP connection for handling the execution of jobs, and will return the contents of the page immediately to the client without waiting for the job to complete. Otherwise, the job will be executed in the same process and the client will have to wait until the job is completed. When the job does not run asynchronously, if a fatal error occurs during job execution, it will propagate to the client, aborting the load of the page.

Note that even if $wgRunJobsAsync is set to true, if PHP can't open a socket to make the internal HTTP request, it will fallback to the synchronous job execution. There are some configurations that can cause the asynchronous job execution to fail:


 * Run jobs async does not honor $wgServerName.
 * runJobs not following redirect.

Changes introduced in MediaWiki 1.22
In, the job queue execution on each page request was changed so, instead of executing the job inside the same PHP process that's rendering the page, a new PHP cli command is spawned to execute  in the background. It will only work if is set to an actual path or safe mode is off, otherwise, the old method will be used.

This new execution method could cause some problems:


 * If is set to an incompatible version of PHP (e.g.: an outdated version) jobs may fail to run (fixed in 1.23).
 * PHP  restrictions are in effect, and  is disallowed (, fixed in 1.23).
 * Performance: even if the job queue is empty, the new PHP process is started anyway (, fixed in 1.23).
 * Sometimes the spawning PHP process cause the server or only the CLI process to hang due to stdout and stderr descriptors not properly redirected (, fixed in 1.22)
 * It does not work for shared code (wiki farms), because it doesn't pass additional required parameters to runJobs.php to identify the wiki that's running the job (, fixed in 1.23)
 * Normal shell limits like, and  are enforced on the runJobs.php process that's being executed in the background.

There's no way to revert to the old on-request job queue handling, besides setting to , for example, which may cause other problems. It can be disabled completely by setting, but jobs will no longer run on page requests, and you must explicitly run runJobs.php to periodically run pending jobs.

Changes introduced in MediaWiki 1.23
In MediaWiki 1.23, the 1.22 execution method is abandoned, and jobs are triggered by MediaWiki making an HTTP connection to itself.

It was first designed as an API entry point but later changed to be an unlisted Special Page: SpecialRunJobs.php.

While it solves various bugs introduced in 1.22, it still requires loading a lot of PHP classes in memory on a new process to execute a job, and also makes a new HTTP request that the server must handle.

Aktualizacja tabeli linków po zmianach w szablonie
MediaWiki 1.6 dodaje zadanie do kolejki zadań dla każdego artykułu, który zawiera w sobie jakiś szablon. Każde zadanie to polecenie, aby przejrzeć artykuł, rozwinąć szablony i odpowiednio zaktualizować tabelę linków. Nie są więc już konieczne puste edycje, których zadaniem byłoby wymuszenie tych aktualizacji, choć może to trochę potrwać, zwłaszcza gdy jest dużo operacji do wykonania. Może to wyraźny sposób odciążyć w pracy jej użytkowników.

Inwalidacja pamięci podręcznej HTML
Szeroka klasa operacji może spowodować potrzebę inwalidacji (czyli unieważnienia/aktualizacji) pamięci podręcznej HTML dla dużej liczby stron; są to operacje typu:


 * zmiana grafiki (wszystkie miniaturki muszą być ponownie zrenderowane a ich rozmiary od nowa przeliczone)
 * usunięcie strony (we wszystkie linkach prowadzących do niej na innych stronach trzeba zmienić kolor z niebieskiego na czerwony)
 * utworzenie lub przywrócenie strony (jak wyżej ale kolor należy zmienić z czerwonego na niebieski)
 * zmiana zawartości szablonu (wszystkie strony, które zawierają dany szablon potrzebują aktualizacji)

Except for template changes, these operations do not invalidate the links tables, but they do invalidate the HTML cache of all pages linking to that page, or using that image. Invalidating the cache of a page is a short operation; it only requires updating a single database field and sending a multicast packet to clear the caches. But if there are more than about 1000 to do, it takes a long time. By default, one job is added per 500 operations (see )

Typical values
During a period of low load, the job queue might be zero. At Wikimedia, the job queue is, in practice, almost never zero. In off-peak hours, it might be a few hundred to a thousand. During a busy day, it might be a few million, but it can quickly fluctuate by 10% or more.

Special:Statistics
Up to MediaWiki 1.16, the job queue value was shown on Special:Statistics. However, since 1.17 (75272) it's been removed, and can be seen now with :

The number of jobs returned in the API result may be slightly inaccurate when using MySQL, which estimates the number of jobs in the database. This number can fluctuate based on the number of jobs that have recently been added or deleted. For other databases that do not support fast result-size estimation, the actual number of jobs is given.