Manual:Job queue/bn

মিডিয়াউইকি ১.৬-এ দীর্ঘকালীন চলমান কাজগুলি অবিচ্ছিন্নভাবে সম্পাদন করার জন্য একটি জব কিউই চালু করা হয়েছিল। জব কিউইটি ব্যাচ প্রসেসিং ব্যবহার করে অনেকগুলি ছোট কাজগুলি ধরে রাখতে ডিজাইন করা হয়েছে।



সেট আপ
আপনি পরিবর্তে কমান্ড লাইনের মাধ্যমে পটভূমিতে পুরোপুরি জবের সময়সূচি নির্ধারণ করার পরামর্শ দেওয়া হচ্ছে। By default, jobs are run at the end of a web request. Disable this default behaviour by setting to.

ক্রোন
You could use cron to run the jobs every hour. Add the following to your crontab file:

Using Cron makes it easy to get started, but can make email notifications and cascading template feel slow (to wait up to an hour). Consider using one of the below approaches to set up a continuous job runner instead.



অবিচ্ছিন্ন পরিষেবা
If you have shell access and the possibility to create init scripts, you can create a simple service to run jobs as they become available, and also throttle them to prevent the job runner to monopolize the CPU resources of the server:

একটি ব্যাশ স্ক্রিপ্ট তৈরি করুন, উদাহরণস্বরূপ  -এ:

সার্ভারটি কত গতিময় এবং এটি যে লোড পরিচালনা করে তার উপর নির্ভর করে আপনি প্রতিটি চক্রটিতে চালানোর জন্য কাজের সংখ্যা এবং প্রতিটি চক্রের জন্য অপেক্ষা করতে কয়েক সেকেন্ডের সংযোজন করতে পারেন।

স্ক্রিপ্টটি সম্পাদনযোগ্য করুন ।

যদি সিস্টেমড ব্যবহার করা হয় তবে  ফাইলটি তৈরি করে একটি নতুন পরিষেবা ইউনিট তৈরি করুন। Change the  parameter to the user that runs PHP on your web server:

এটি সক্ষম করুন এবং সেই আদেশগুলি দিয়ে এটি শুরু করুন:



পৃষ্ঠার অনুরোধগুলিতে কাজের সম্পাদনা
ডিফল্টরূপে, প্রতিটি ওয়েব অনুরোধের শেষে, একটি কাজ কাজের সারি থেকে নেওয়া হয় এবং কার্যকর করা হয়। This behavior is controlled by the configuration variable. Setting this variable to, will run a job on each request. Setting this variable to  will disable the execution of jobs during web requests completely, so that you can instead run  manually or periodically from the command line.

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



পারফরম্যান্স ইস্যু
If the performance burden of running jobs on every web request is too great but you are unable to run jobs from the command line, you can reduce to a number between   and. This means a job will execute on average every  requests.



ম্যানুয়াল ব্যবহার
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. উদাহরণস্বরূপ:

Abandoned jobs
A job can fail for some reasons. To understand why, you have to inspect the related log file.

In any case, if a job fails 3 times (so if the system has done that number of attempts), the job is then considered "abandoned" and it's not executed again.

Relevant source code:

https://doc.wikimedia.org/mediawiki-core/master/php/JobQueue_8php_source.html#l00085

An abandoned job is:


 * not executed anymore from
 * not counted from
 * not automatically removed from the database
 * but are included in the count of Special:Statistics

অ্যাসিঙ্ক্রোনাস
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. অন্যথায়, একই প্রক্রিয়াতে কাজটি কার্যকর করা হবে এবং ক্লায়েন্টকে কাজ শেষ না হওয়া পর্যন্ত অপেক্ষা করতে হবে। 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 fall back to the synchronous job execution. However, there are a variety of situations where this internal request may fail, and jobs won't be run, without falling back to the synchronous job execution. Starting with MediaWiki 1.28.1 and 1.27.2, $wgRunJobsAsync now defaults to false.



স্থিত আপডেট
The deferred updates mechanism allows the execution of code to be scheduled for the end of the request, after all content has been sent to the browser. This is similar to queuing a job, except that it runs immediately instead of upto several minutes/hours in the future.

DeferredUpdates was introduced in MediaWiki 1.23 and received major changes during MediaWiki 1.27 and 1.28. The goal of this mechanism is speed up the web responses by doing less work, as well as to prioritise some work that would previously be a job to run as soon as possible after the end of the response.

A deferrable update can implement  in order to be queueable as a Job as well. This is used by RefreshSecondaryDataUpdate in core, for example, which means if the update fails for any reason, MediaWiki will fallback to queuing as a job and try again later as to fulfil the contract in question.

Changes 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 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 the unlisted special page Special:RunJobs.

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.

Changes in MediaWiki 1.27
In MediaWiki 1.25 and MediaWiki 1.26, use of would sometimes cause jobs not to get run if the wiki has custom   configuration. This was fixed in MediaWiki 1.27.

Changes in MediaWiki 1.28
Between MediaWiki 1.23 and MediaWiki 1.27, use of would cause jobs not to get run on if MediaWiki requests are for a server name or protocol that does not match the currently configured server name one (e.g. when supporting both HTTP and HTTPS, or when MediaWiki is behind a reverse proxy that redirects to HTTPS). This was fixed in MediaWiki 1.28.

Changes in MediaWiki 1.29
In MediaWiki 1.27.0 to 1.27.3 and 1.28.0 to 1.28.2, when is set to a value greater than 0, an error like the one below may appear in error logs, or on the page:

PHP Notice: JobQueueGroup::__destruct: 1 buffered job(s) never inserted

As a result of this error, certain updates may fail in some cases, like category members not being updated on category pages, or recent changes displaying edits of deleted pages - even if you manually run to clear the job queue. It has been reported as a bug and was solved in 1.27.4 and 1.28.3.

Updating links tables when a template changes
When a template changes, MediaWiki adds a job to the job queue for each article transcluding that template. Each job is a command to read an article, expand any templates, and update the link table accordingly. Previously, the host articles would remain outdated until either their parser cache expires or until a user edits the article.

HTML cache invalidation
A wider class of operations can result in invalidation of the HTML cache for a large number of pages:


 * Changing an image (all the thumbnails have to be re-rendered, and their sizes recalculated)
 * Deleting a page (all the links to it from other pages need to change from blue to red)
 * Creating or undeleting a page (like above, but from red to blue)
 * Changing a template (all the pages that transclude the template need updating)

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 300 operations (see )

Note, however, that even if purging the cache of a page is a short operation, reparsing a complex page that is not in the cache may be expensive, especially if a highly used template is edited and causes lots of pages to be purged in a short period of time and your wiki has lots of concurrent visitors loading a wide spread of pages. This can be mitigated by reducing the number of pages purged in a short period of time, by reducing to a small number (20, for example) and also set  for   to a low number (5, for example).

Audio and video transcoding
When using to process local uploads of audio and video files, the job queue is used to run the potentially very slow creation of derivative transcodes at various resolutions/formats.

These are not suitable for running on web requests -- you will need a background runner.

It's recommended to set up separate runners for the  and   job types if possible. These two queues process different subsets of files -- the first for high resolution HD videos, and the second for lower-resolution videos and audio files which process more quickly.

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.



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