Manual:Job queue/ja

MediaWiki 1.6 でジョブキューが導入され、長い処理を非同期的に実行できるようになりました. このジョブキューは、バッチ処理を使用して短時間のタスクを多数保持するよう設計されています.

Set up
By default, jobs are run at the end of a web request. If possible, it is recommended that you disable this default behaviour by setting to , and instead schedule the running of jobs completely in the background, via the command line. For example, you could use cron to run the jobs every day at midnight by entering the following in your crontab file:

ページ リクエストの際のジョブ実行
By default, at the end of each web request, 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  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. asynchronous の節を参照してください.

パフォーマンスの問題点
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.

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. 例:

非同期
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. 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.

Deferred updates
The deferred updates mechanism was introduced in MediaWiki 1.23 and received major changes during MediaWiki 1.27 and 1.28. It allows the execution of some features at the end of the request, when all the content has been sent to the browser, instead of queuing it in the job, which would otherwise be executed potentially some hours later. The goal of this alternate mechanism is mainly to speed up the main MediaWiki requests, and at the same time execute some features as soon as possible at the end of the request.

Some deferrable updates can be both deferrable updates and jobs, if specified as such.

MediaWiki 1.22 での変更点
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.

MediaWiki 1.23 での変更点
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 introduced 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 introduced 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 introduced 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 キャッシュの無効化
大量のページに相当する既存のHTMLキャッシュを一気に無効にしてしまう操作は、〔テンプレートの改訂だけでなく〕より幅広い種類にわたります:


 * 画像の改訂（すべてのサムネイルを作り直し、大きさも再計算する必要があります）
 * ページの削除（すべてのリンク元でのリンクの色を、青から赤にする必要があります）
 * ページの作成、または復帰〔被削除物の回復. undelete. 復活とも〕（上記同様ですが、反対に赤から青にします）
 * テンプレートの改訂（テンプレートの参照読み込みされたページ〔のキャッシュ〕をすべて更新する必要があります）

テンプレートの改訂を除くこれらの操作の結果、リンクの表〔の内容〕が無効になることはありませんが、一方で、当該ページのリンク元の、あるいは当該画像の使用先の、すべてのページのHTMLキャッシュが無効になります. 1ページ分のキャッシュを無効にする処理はごく短く、必要なのはデータベースのフィールドを1件更新し、マルチキャストのパケットを1つ発してキャッシュを消すことだけです. しかしそれが1000件以上もある場合には、かなり時間がかかります. 初期設定では、500ページ分以上を無効化する必要のある場合のみ、500ページあたり1件の処理項目が〔ジョブキューに〕発生します ( を参照).

典型的な値
低負荷の期間に、ジョブキューはゼロであるかもしれません. Wikimedia でのジョブキューは、実際ほとんどゼロではありません. 混雑していない時間帯では数百から千であるかもしれません. 混雑している日の間では、それは数百万でもあり、１０％以上素早く上下します.

Special:Statistics
MediaWiki 1.16 まで、ジョブキューの長さは Special:Statistics に表示されました. 1.17 (75272) からそれは取り除かれて で確認できます:

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.