Help:Job queue
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This is a copy of the master help page at Meta. Do not edit this copy. Edits will be lost in the next update from the master page. See below for more information. |
In MediaWiki 1.6, a job queue was introduced, to perform long-running tasks asynchronously. The job queue is designed to hold many short tasks. You can view the length of the job queue by visiting Special:Statistics on most 1.6 wikis. By default, each time a request runs, one job is taken from the job queue and executed. If the performance burden of this is too great, you can reduce $wgJobRunRate by putting something like this in your LocalSettings.php:
- $wgJobRunRate = 0.01;
You can also execute the job queue from the command line, by running maintenance/runJobs.php.
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Why the job queue exists
Updating links tables when a template changes
MediaWiki 1.6 adds a job to the job queue for each article using the template. Each job is a command to read an article, expand any templates, and update the link table accordingly. So null edits are no longer necessary, although it may take a while for big operations to complete. This can help to ease strain on a real person.
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 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, jobs are added when more than 500 pages need to be invalidated, one job per 500 operations.
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Wikipedia-specific help
This page is a copy of the master help page at Meta (for general help information all Wikimedia projects can use), with two Wikipedia-specific templates inserted. To update the main text, edit the master help page for all projects at m:Help:Job queue. For Wikipedia-specific issues, use Template:Ph:Job queue (the extra text at the bottom of this page) or Template:Phh:Job queue for a Wikipedia-specific lead (text appears at the top of this page). You are welcome to replace the full wikitext of this page with that of the master page at Meta at any time. To view this page in other languages see the master page at Meta.
