includes/cache/LinkCache.php
<?php
/**
* Page existence cache.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License along
* with this program; if not, write to the Free Software Foundation, Inc.,
* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
* http://www.gnu.org/copyleft/gpl.html
*
* @file
* @ingroup Cache
*/
namespace MediaWiki\Cache;
use InvalidArgumentException;
use MapCacheLRU;
use MediaWiki\Linker\LinkTarget;
use MediaWiki\MainConfigNames;
use MediaWiki\MediaWikiServices;
use MediaWiki\Page\PageIdentity;
use MediaWiki\Page\PageReference;
use MediaWiki\Page\PageStoreRecord;
use MediaWiki\Title\NamespaceInfo;
use MediaWiki\Title\TitleFormatter;
use MediaWiki\Title\TitleValue;
use Psr\Log\LoggerAwareInterface;
use Psr\Log\LoggerInterface;
use Psr\Log\NullLogger;
use stdClass;
use WANObjectCache;
use Wikimedia\Rdbms\Database;
use Wikimedia\Rdbms\IDBAccessObject;
use Wikimedia\Rdbms\ILoadBalancer;
use Wikimedia\Rdbms\IReadableDatabase;
/**
* Cache for article titles (prefixed DB keys) and ids linked from one source
*
* @ingroup Cache
*/
class LinkCache implements LoggerAwareInterface {
/** @var MapCacheLRU */
private $entries;
/** @var WANObjectCache */
private $wanCache;
/** @var TitleFormatter */
private $titleFormatter;
/** @var NamespaceInfo */
private $nsInfo;
/** @var ILoadBalancer|null */
private $loadBalancer;
/** @var LoggerInterface */
private $logger;
/** How many Titles to store */
private const MAX_SIZE = 10000;
/** Key to page row object or null */
private const ROW = 0;
/** Key to query READ_* flags */
private const FLAGS = 1;
/**
* @param TitleFormatter $titleFormatter
* @param WANObjectCache $cache
* @param NamespaceInfo $nsInfo
* @param ILoadBalancer|null $loadBalancer Use null when no database is set up, for example on installation
*/
public function __construct(
TitleFormatter $titleFormatter,
WANObjectCache $cache,
NamespaceInfo $nsInfo,
ILoadBalancer $loadBalancer = null
) {
$this->entries = new MapCacheLRU( self::MAX_SIZE );
$this->wanCache = $cache;
$this->titleFormatter = $titleFormatter;
$this->nsInfo = $nsInfo;
$this->loadBalancer = $loadBalancer;
$this->logger = new NullLogger();
}
/**
* @param LoggerInterface $logger
*/
public function setLogger( LoggerInterface $logger ) {
$this->logger = $logger;
}
/**
* @param LinkTarget|PageReference|array|string $page
* @param bool $passThrough Return $page if $page is a string
* @return ?string the cache key
*/
private function getCacheKey( $page, $passThrough = false ) {
if ( is_string( $page ) ) {
if ( $passThrough ) {
return $page;
} else {
throw new InvalidArgumentException( 'They key may not be given as a string here' );
}
}
if ( is_array( $page ) ) {
$namespace = $page['page_namespace'];
$dbkey = $page['page_title'];
return strtr( $this->titleFormatter->formatTitle( $namespace, $dbkey ), ' ', '_' );
}
if ( $page instanceof PageReference && $page->getWikiId() !== PageReference::LOCAL ) {
// No cross-wiki support yet. Perhaps LinkCache can become wiki-aware in the future.
$this->logger->info(
'cross-wiki page reference',
[
'page-wiki' => $page->getWikiId(),
'page-reference' => $this->titleFormatter->getFullText( $page )
]
);
return null;
}
if ( $page instanceof PageIdentity && !$page->canExist() ) {
// Non-proper page, perhaps a special page or interwiki link or relative section link.
$this->logger->warning(
'non-proper page reference: {page-reference}',
[ 'page-reference' => $this->titleFormatter->getFullText( $page ) ]
);
return null;
}
if ( $page instanceof LinkTarget
&& ( $page->isExternal() || $page->getText() === '' || $page->getNamespace() < 0 )
) {
// Interwiki link or relative section link. These do not have a page ID, so they
// can neither be "good" nor "bad" in the sense of this class.
$this->logger->warning(
'link to non-proper page: {page-link}',
[ 'page-link' => $this->titleFormatter->getFullText( $page ) ]
);
return null;
}
return $this->titleFormatter->getPrefixedDBkey( $page );
}
/**
* Get the ID of a page known to the process cache
*
* @param LinkTarget|PageReference|array|string $page The page to get the ID for,
* as an object, an array containing the page_namespace and page_title fields,
* or a prefixed DB key. In MediaWiki 1.36 and earlier, only a string was accepted.
* @return int Page ID, or zero if the page was not cached or does not exist or is not a
* proper page (e.g. a special page or an interwiki link).
*/
public function getGoodLinkID( $page ) {
$key = $this->getCacheKey( $page, true );
if ( $key === null ) {
return 0;
}
$entry = $this->entries->get( $key );
if ( !$entry ) {
return 0;
}
$row = $entry[self::ROW];
return $row ? (int)$row->page_id : 0;
}
/**
* Get the field of a page known to the process cache
*
* If this link is not a cached good title, it will return NULL.
* @param LinkTarget|PageReference|array $page The page to get cached info for.
* Can be given as an object or an associative array containing the
* page_namespace and page_title fields.
* In MediaWiki 1.36 and earlier, only LinkTarget was accepted.
* @param string $field ( 'id', 'length', 'redirect', 'revision', 'model', 'lang' )
* @return string|int|null The field value, or null if the page was not cached or does not exist
* or is not a proper page (e.g. a special page or interwiki link).
*/
public function getGoodLinkFieldObj( $page, string $field ) {
$key = $this->getCacheKey( $page );
if ( $key === null ) {
return null;
}
$entry = $this->entries->get( $key );
if ( !$entry ) {
return null;
}
$row = $entry[self::ROW];
if ( !$row ) {
return null;
}
switch ( $field ) {
case 'id':
return (int)$row->page_id;
case 'length':
return (int)$row->page_len;
case 'redirect':
return (int)$row->page_is_redirect;
case 'revision':
return (int)$row->page_latest;
case 'model':
return !empty( $row->page_content_model )
? (string)$row->page_content_model
: null;
case 'lang':
return !empty( $row->page_lang )
? (string)$row->page_lang
: null;
default:
throw new InvalidArgumentException( "Unknown field: $field" );
}
}
/**
* Check if a page is known to be missing based on the process cache
*
* @param LinkTarget|PageReference|array|string $page The page to get cached info for,
* as an object, an array containing the page_namespace and page_title fields,
* or a prefixed DB key. In MediaWiki 1.36 and earlier, only a string was accepted.
* In MediaWiki 1.36 and earlier, only a string was accepted.
* @return bool Whether the page is known to be missing based on the process cache
*/
public function isBadLink( $page ) {
$key = $this->getCacheKey( $page, true );
if ( $key === null ) {
return false;
}
$entry = $this->entries->get( $key );
return ( $entry && !$entry[self::ROW] );
}
/**
* Add information about an existing page to the process cache
*
* Callers must set the READ_LATEST flag if the row came from a DB_PRIMARY source.
* However, the use of such data is highly discouraged; most callers rely on seeing
* consistent DB_REPLICA data (e.g. REPEATABLE-READ point-in-time snapshots) and the
* accidental use of DB_PRIMARY data via LinkCache is prone to causing anomalies.
*
* @param LinkTarget|PageReference|array $page The page to set cached info for.
* Can be given as an object or an associative array containing the
* page_namespace and page_title fields.
* In MediaWiki 1.36 and earlier, only LinkTarget was accepted.
* @param stdClass $row Object which has all fields returned by getSelectFields().
* @param int $queryFlags The query flags used to retrieve the row, IDBAccessObject::READ_*
* @since 1.19
*/
public function addGoodLinkObjFromRow(
$page,
stdClass $row,
int $queryFlags = IDBAccessObject::READ_NORMAL
) {
$key = $this->getCacheKey( $page );
if ( $key === null ) {
return;
}
foreach ( self::getSelectFields() as $field ) {
if ( !property_exists( $row, $field ) ) {
throw new InvalidArgumentException( "Missing field: $field" );
}
}
$this->entries->set( $key, [ self::ROW => $row, self::FLAGS => $queryFlags ] );
}
/**
* Add information about a missing page to the process cache
*
* Callers must set the READ_LATEST flag if the row came from a DB_PRIMARY source.
* However, the use of such data is highly discouraged; most callers rely on seeing
* consistent DB_REPLICA data (e.g. REPEATABLE-READ point-in-time snapshots) and the
* accidental use of DB_PRIMARY data via LinkCache is prone to causing anomalies.
*
* @param LinkTarget|PageReference|array $page The page to set cached info for.
* Can be given as an object or an associative array containing the
* page_namespace and page_title fields.
* In MediaWiki 1.36 and earlier, only LinkTarget was accepted.
* @param int $queryFlags The query flags used to retrieve the row, IDBAccessObject::READ_*
*/
public function addBadLinkObj( $page, int $queryFlags = IDBAccessObject::READ_NORMAL ) {
$key = $this->getCacheKey( $page );
if ( $key === null ) {
return;
}
$this->entries->set( $key, [ self::ROW => null, self::FLAGS => $queryFlags ] );
}
/**
* Clear information about a page being missing from the process cache
*
* @param LinkTarget|PageReference|array|string $page The page to clear cached info for,
* as an object, an array containing the page_namespace and page_title fields,
* or a prefixed DB key. In MediaWiki 1.36 and earlier, only a string was accepted.
* In MediaWiki 1.36 and earlier, only a string was accepted.
*/
public function clearBadLink( $page ) {
$key = $this->getCacheKey( $page, true );
if ( $key === null ) {
return;
}
$entry = $this->entries->get( $key );
if ( $entry && !$entry[self::ROW] ) {
$this->entries->clear( $key );
}
}
/**
* Clear information about a page from the process cache
*
* @param LinkTarget|PageReference|array $page The page to clear cached info for.
* Can be given as an object or an associative array containing the
* page_namespace and page_title fields.
* In MediaWiki 1.36 and earlier, only LinkTarget was accepted.
*/
public function clearLink( $page ) {
$key = $this->getCacheKey( $page );
if ( $key !== null ) {
$this->entries->clear( $key );
}
}
/**
* Fields that LinkCache needs to select
*
* @since 1.28
* @return array
*/
public static function getSelectFields() {
$pageLanguageUseDB = MediaWikiServices::getInstance()->getMainConfig()
->get( MainConfigNames::PageLanguageUseDB );
$fields = array_merge(
PageStoreRecord::REQUIRED_FIELDS,
[
'page_len',
'page_content_model',
]
);
if ( $pageLanguageUseDB ) {
$fields[] = 'page_lang';
}
return $fields;
}
/**
* Add a title to the link cache, return the page_id or zero if non-existent.
* This causes the link to be looked up in the database if it is not yet cached.
*
* @deprecated since 1.37, use PageStore::getPageForLink() instead.
*
* @param LinkTarget|PageReference|array $page The page to load.
* Can be given as an object or an associative array containing the
* page_namespace and page_title fields.
* In MediaWiki 1.36 and earlier, only LinkTarget was accepted.
* @param int $queryFlags IDBAccessObject::READ_XXX
*
* @return int Page ID or zero
*/
public function addLinkObj( $page, int $queryFlags = IDBAccessObject::READ_NORMAL ) {
$row = $this->getGoodLinkRow(
$page->getNamespace(),
$page->getDBkey(),
[ $this, 'fetchPageRow' ],
$queryFlags
);
return $row ? (int)$row->page_id : 0;
}
/**
* @param TitleValue $link
* @param callable|null $fetchCallback
* @param int $queryFlags
* @return array [ $shouldAddGoodLink, $row ], $shouldAddGoodLink is a bool indicating
* whether addGoodLinkObjFromRow should be called, and $row is the row the caller was looking
* for (or null, when it was not found).
*/
private function getGoodLinkRowInternal(
TitleValue $link,
callable $fetchCallback = null,
int $queryFlags = IDBAccessObject::READ_NORMAL
): array {
$callerShouldAddGoodLink = false;
$key = $this->getCacheKey( $link );
if ( $key === null ) {
return [ $callerShouldAddGoodLink, null ];
}
$ns = $link->getNamespace();
$dbkey = $link->getDBkey();
$entry = $this->entries->get( $key );
if ( $entry && $entry[self::FLAGS] >= $queryFlags ) {
return [ $callerShouldAddGoodLink, $entry[self::ROW] ?: null ];
}
if ( !$fetchCallback ) {
return [ $callerShouldAddGoodLink, null ];
}
$callerShouldAddGoodLink = true;
$wanCacheKey = $this->getPersistentCacheKey( $link );
if ( $wanCacheKey !== null && !( $queryFlags & IDBAccessObject::READ_LATEST ) ) {
// Some pages are often transcluded heavily, so use persistent caching
$row = $this->wanCache->getWithSetCallback(
$wanCacheKey,
WANObjectCache::TTL_DAY,
function ( $curValue, &$ttl, array &$setOpts ) use ( $fetchCallback, $ns, $dbkey ) {
$dbr = $this->loadBalancer->getConnection( ILoadBalancer::DB_REPLICA );
$setOpts += Database::getCacheSetOptions( $dbr );
$row = $fetchCallback( $dbr, $ns, $dbkey, [] );
$mtime = $row ? (int)wfTimestamp( TS_UNIX, $row->page_touched ) : false;
$ttl = $this->wanCache->adaptiveTTL( $mtime, $ttl );
return $row;
}
);
} else {
// No persistent caching needed, but we can still use the callback.
if ( ( $queryFlags & IDBAccessObject::READ_LATEST ) == IDBAccessObject::READ_LATEST ) {
$dbr = $this->loadBalancer->getConnection( DB_PRIMARY );
} else {
$dbr = $this->loadBalancer->getConnection( DB_REPLICA );
}
$options = [];
if ( ( $queryFlags & IDBAccessObject::READ_EXCLUSIVE ) == IDBAccessObject::READ_EXCLUSIVE ) {
$options[] = 'FOR UPDATE';
} elseif ( ( $queryFlags & IDBAccessObject::READ_LOCKING ) == IDBAccessObject::READ_LOCKING ) {
$options[] = 'LOCK IN SHARE MODE';
}
$row = $fetchCallback( $dbr, $ns, $dbkey, $options );
}
return [ $callerShouldAddGoodLink, $row ?: null ];
}
/**
* Returns the row for the page if the page exists (subject to race conditions).
* The row will be returned from local cache or WAN cache if possible, or it
* will be looked up using the callback provided.
*
* @param int $ns
* @param string $dbkey
* @param callable|null $fetchCallback A callback that will retrieve the link row with the
* signature ( IReadableDatabase $db, int $ns, string $dbkey, array $queryOptions ): ?stdObj.
* @param int $queryFlags IDBAccessObject::READ_XXX
*
* @return stdClass|null
* @internal for use by PageStore. Other code should use a PageLookup instead.
*/
public function getGoodLinkRow(
int $ns,
string $dbkey,
callable $fetchCallback = null,
int $queryFlags = IDBAccessObject::READ_NORMAL
): ?stdClass {
$link = TitleValue::tryNew( $ns, $dbkey );
if ( $link === null ) {
return null;
}
[ $shouldAddGoodLink, $row ] = $this->getGoodLinkRowInternal(
$link,
$fetchCallback,
$queryFlags
);
if ( $row ) {
if ( $shouldAddGoodLink ) {
try {
$this->addGoodLinkObjFromRow( $link, $row, $queryFlags );
} catch ( InvalidArgumentException $e ) {
// a field is missing from $row; maybe we used a cache?; invalidate it and try again
$this->invalidateTitle( $link );
[ , $row ] = $this->getGoodLinkRowInternal(
$link,
$fetchCallback,
$queryFlags
);
$this->addGoodLinkObjFromRow( $link, $row, $queryFlags );
}
}
} else {
$this->addBadLinkObj( $link );
}
return $row ?: null;
}
/**
* @param LinkTarget|PageReference|TitleValue $page
* @return string|null
*/
private function getPersistentCacheKey( $page ) {
// if no key can be derived, the page isn't cacheable
if ( $this->getCacheKey( $page ) === null || !$this->usePersistentCache( $page ) ) {
return null;
}
return $this->wanCache->makeKey(
'page',
$page->getNamespace(),
sha1( $page->getDBkey()
) );
}
/**
* @param LinkTarget|PageReference|int $pageOrNamespace
* @return bool
*/
private function usePersistentCache( $pageOrNamespace ) {
$ns = is_int( $pageOrNamespace ) ? $pageOrNamespace : $pageOrNamespace->getNamespace();
if ( in_array( $ns, [ NS_TEMPLATE, NS_FILE, NS_CATEGORY, NS_MEDIAWIKI ] ) ) {
return true;
}
// Focus on transcluded pages more than the main content
if ( $this->nsInfo->isContent( $ns ) ) {
return false;
}
// Non-talk extension namespaces (e.g. NS_MODULE)
return ( $ns >= 100 && $this->nsInfo->isSubject( $ns ) );
}
/**
* @param IReadableDatabase $db
* @param int $ns
* @param string $dbkey
* @param array $options Query options, see IDatabase::select() for details.
* @return stdClass|false
*/
private function fetchPageRow( IReadableDatabase $db, int $ns, string $dbkey, $options = [] ) {
$queryBuilder = $db->newSelectQueryBuilder()
->select( self::getSelectFields() )
->from( 'page' )
->where( [ 'page_namespace' => $ns, 'page_title' => $dbkey ] )
->options( $options );
return $queryBuilder->caller( __METHOD__ )->fetchRow();
}
/**
* Purge the persistent link cache for a title
*
* @param LinkTarget|PageReference $page
* In MediaWiki 1.36 and earlier, only LinkTarget was accepted.
* @since 1.28
*/
public function invalidateTitle( $page ) {
$wanCacheKey = $this->getPersistentCacheKey( $page );
if ( $wanCacheKey !== null ) {
$this->wanCache->delete( $wanCacheKey );
}
$this->clearLink( $page );
}
/**
* Clears cache
*/
public function clear() {
$this->entries->clear();
}
}
/** @deprecated class alias since 1.42 */
class_alias( LinkCache::class, 'LinkCache' );