Manual:File cache/fr

MediaWiki possède un schéma simplifié optionnel pour enregitrer le HTML généré des pages d'articles dans le cache.

Opération et utilisation
Le cache des fichiers est activé en initialisant ces variables dans LocalSettings.php :

= true; /* par défaut : false */ = "$IP/cache"; # ou en laissant la valeur par défaut : "{$wgUploadDirectory}/cache" qui vaut "$IP/images/cache" par défaut

Ceci a pour conséquence que la page web HTML générée pour chaque page du wiki, sera rangée dans un fichier dédié sur le disque dur. Toute les demandes ultérieures émanant d'utilisateurs anonymes sont répondues non pas en générant de nouveau la page mais simplement en renvoyant la version du fichier HTML qui a été enregistré sur le disque. Ceci permet de gagner du temps.

Le texte web HTML généré est mis sur le disque dans les répertoires sous  et ressemble à ceci :

 -rw-r--r-- 1 apache apache 57421 Jan 7 01:58 cache/0/04/P%C3%A1gina_principal.html -rw-r--r-- 1 apache apache 29608 Jan 4 16:37 cache/1/17/P%C3%A1gina_Riscada.html -rw-r--r-- 1 apache apache 21592 Jan 3 07:27 cache/1/1c/P%C3%A1gina_Duplicada.html -rw-r--r-- 1 apache apache 36088 Jan 7 02:03 cache/2/24/P%C3%A1gina_principal_alternativa.html -rw-r--r-- 1 apache apache 44205 Jan 7 06:10 cache/a/a4/P%C3%A1gina_linkada.html -rw-r--r-- 1 apache apache 24686 Jan 3 07:27 cache/d/db/P%C3%A1gina_Invertida.html -rw-r--r-- 1 apache apache 17222 Jan 3 06:28 cache/f/f0/P%C3%A1gina_n%C3%A3o_encontrada.html

Dans cet exemple, le répertoire du cache des fichiers est cache/ et les pages du wiki sont enregistrées dans chaque fichier Página ..., avec une correspondance d'un fichier Página_....html pour une page du wiki. Ces fichiers sont créés au fur et à mesure que les utilisateurs visitent les articles du wiki; vous pouvez tous les créer en une seule passe avec le script de maintenance rebuildFileCache.php.

Le cache des fichiers se comporte plutôt brutalement; il n'y a pas de durée limite de présence dans le cache pour les pages générées et elles sont mises en cache inconditionnellemnt, même si elles contiennent des variables, des extensions, et d'autres sorties variables. Certaines extensions suppriment la mise en cache pour les pages ayant un contenu dynamique.

Pour un résultat plus parlant, considerez l'utilisation de $wgUseGzip à la place de (ou combiné avec).

Pour des sites plus gros, l'utilisation d'un cache externe tel que Squid ou Varnish est préférable pour l'activation du cache des fichiers.

Si le cache des fichiers semble ne pas fonctionner, assurez-vous que le serveur web a la permission d'écrire dans le répertoire que vous avez choisi.

Limitations
Les noms de fichier des fichiers du cache sont définis en fonction du titre des pages. Depending on the language, which is used in the page titles, some characters in the file names will have to be encoded in order to make up a valid file name for the according file system. Pour les langues telles que l'arabe, le chinois et autres, cela peut se traduire par l'avertissement PHP suivant :

PHP Warning: file_put_contents(cache/......html.gz): failed to open stream: File name too long in includes/cache/FileCacheBase.php on line 171

Ceci est une limitation connue. Voir.

Category and image description pages aren't purged from file cache. For example, adding or removing a page from a category doesn't update the category page, causing not logged in users to not see the changes in the category page. Ceci est une limitation connue. Voir

Domaine et intervalle
Caching is only done for users who:
 * are not logged in.
 * do not have their user_newtalk flag active.

Caching is only done for pages which:
 * are not special pages.
 * are not redirects.
 * are being viewed in current version, plain view, no url parameters

This covers the majority of requests to the wiki, but it is still important to set up bytecode and application caching to handle the rest.

Validation
The modification time of the cached file is compared with the global  timestamp set in  on each view.

If the file is at least as new as both of these, it is considered valid and is sent directly to the client. If it is older or does not exist, parsing and rendering continues and the results are saved for future use.

Invalidation
The entire cache can be invalidated by setting  to the current time, or by deleting all files in the cache.

Individual pages are invalidated by updating their page.page_touched fields, conveniently done by calling. This should be done on article creation, edit saves, renames, and creation and deletion of linked articles (in order to update edit links). Invalidation operations that occur when editing templates, for example, check pages that use template to compare the cache date against page_touched.

Certains cas ne sont pas encore bien gérés, ce qui inclut probablement :


 * 'reload' ou 'refresh' du navigateur (ne recharge que la page en cache sans en faire la mise à jour)
 * output variables from extensions such as Extension:DynamicPageList disable filecache for those pages to avoid stale data. Those that don't will return stale data even on browser refresh.
 * certain long error messages may be cached indefinitely as if they were valid page content; only ?action=purge will remove these from the file cache once stored. A minimum output size threshold is used to avoid caching most errors, like fatal PHP errors.

Also see:.

Expiration
There should probably be some method of expiration of cache pages, particularly for pages containing variables (it is X date, we have X articles, etc).

If  is -1, file caching will be disabled for the output of the page. There is no provision to set an expiry time, so all HTML for all pages is cached forever. An explicit ?action=purge command (or an edit to the page) will regenerate that one page, but neither the MediaWiki internal no-cache flags nor the browser refresh will remove outdated extension output once it has been stored as part of a file-cached page.

Onglet de rafraichissement
It is possible to add a tab to force one individual page to be invalidated and refreshed by using ?action=purge using the Purge page extension.

Compression
Optionally, the cache may be compressed to save space and bandwidth. (This requires that zlib be enabled in the PHP config.)

If compression is enabled, the cache files are saved as .html.gz. Browsers that advertise support for gzip in their Accept-Encoding field will be given the gzipped version straight; for those browsers that don't, we unzip the data on the fly and send them the plaintext.

A "Vary: User-agent" header will be sent to tell proxy caches to be more careful about who it resends data to. ("Vary: Accept-encoding" would be more appropriate, but Internet Explorer refuses to cache pages so marked.)

Repli d'urgence
If the wiki can't contact the database server, it will try to show the cached version of whatever page was requested, regardless of whether it may be current or not, with a "database is down" message tacked into it.

This has some limitations:
 * special pages are not covered in any way, there's just a warning message
 * redirect pages are not cached, so clicking a link to a redirect doesn't go through to the final destination
 * pages with colons in the title (other than for a valid namespace) may still fail due to MediaWiki checking the DB to see if the title has a valid interwiki prefix. This occurs only if there is no interwiki cache entry for the page's prefix (see ) or   is falling back (or set to).
 * attempts to use non-view actions result in a plain page view, which may be confusing
 * there may be issues with the MySQL connection timeout which make it take prohibitively long before giving up, particularly if using persistent connections and the db dies later. Adjust mysql.connect_timeout (set to 3 or more) in php.ini to deal with this. Edit the webserver's php.ini not the cli php.ini.
 * fallback may fail if  is not "true" due to attempting a DB query
 * fallback may fail if  is set to "cache" and   is falling back (or set to) DB_CACHE

Répondre directement avec les pages du cache
By default, MediaWiki passes cache page with php. Here is how we use webserver configuration tricks to serve cached files directly without invoking MediaWiki or PHP at all.

First, setting. Then we add rewrite rules. See below.

Apache
The following mod_rewrite rule has been found to work in an .htaccess file on a shared webhost running Apache 2.2:

 RewriteBase / RewriteCond %{HTTP_COOKIE} !UserID= RewriteCond %{QUERY_STRING} !. RewriteCond %{DOCUMENT_ROOT}/w/html_cache/$1.html -s RewriteRule ^wiki/(.+)$ /w/html_cache/$1.html [B,L,NS]
 * 1) If a cached page exists under /w/html_cache, do an internal redirect to it:

However, this rewrite rule won't work properly for pages whose titles contain punctuation or non-ASCII characters. A tidy solution would be to use a RewriteMap, but this is not supported in .htaccess context. Instead, the following trick can be used to handle non-ASCII titles by pulling the URL-escaped title directly from the raw request line:

 RewriteBase / RewriteCond %{HTTP_COOKIE} !UserID= RewriteCond %{QUERY_STRING} !. ReWriteCond %{THE_REQUEST} ^GET\x20/wiki/([^\x20/]+)\x20HTTP RewriteCond %{DOCUMENT_ROOT}/w/html_cache/%1.html -s RewriteRule ^wiki/(.+)$ /w/html_cache/%1.html [B,L,NS]
 * 1) If a cached page exists under /w/html_cache, do an internal redirect to it:

This will still not match titles containing periods, slashes or other punctuation which the file cache escapes but browsers don't (or vice versa). One should also ensure that the appropriate Vary header gets sent:

Header append Vary Cookie

Also note that, since this redirect trick bypasses MediaWiki entirely, it won't respect. You may need to clear or rebuild the cache manually as needed instead.

Nginx
Since the nginx configuration language is pretty limited (it doesn't allow nested if statements, for example), it requires the ngx_lua module.

The following conf should be integrated inside your server block, and it assumes that:
 * you're using fancy urls like example.com/Page;
 * your cache folder is inside your MediaWiki folder (default);
 * you're already proxying *.php files to php-fpm (or whatever) in the last location block.

And here are the limitations:
 * as with the Apache solution, you have to run a cron job or manually rebuild the cache files when they change;
 * pages whose title include non-ASCII characters are served through PHP (which should be transparent to the user anyway).

Modifier les chemins si nécessaire.