513 lines
15 KiB
PHP
513 lines
15 KiB
PHP
<?php
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/**
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* Predictive edit preparation system for MediaWiki page.
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License along
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* with this program; if not, write to the Free Software Foundation, Inc.,
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* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
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* http://www.gnu.org/copyleft/gpl.html
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*
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* @file
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*/
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namespace MediaWiki\Storage;
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use ActorMigration;
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use BagOStuff;
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use Content;
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use Hooks;
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use Liuggio\StatsdClient\Factory\StatsdDataFactoryInterface;
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use ParserOutput;
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use Psr\Log\LoggerInterface;
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use stdClass;
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use Title;
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use User;
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use Wikimedia\Rdbms\ILoadBalancer;
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use Wikimedia\ScopedCallback;
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use WikiPage;
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/**
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* Class for managing stashed edits used by the page updater classes
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*
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* @since 1.34
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*/
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class PageEditStash {
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/** @var BagOStuff */
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private $cache;
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/** @var ILoadBalancer */
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private $lb;
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/** @var LoggerInterface */
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private $logger;
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/** @var StatsdDataFactoryInterface */
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private $stats;
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/** @var int */
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private $initiator;
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const ERROR_NONE = 'stashed';
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const ERROR_PARSE = 'error_parse';
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const ERROR_CACHE = 'error_cache';
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const ERROR_UNCACHEABLE = 'uncacheable';
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const ERROR_BUSY = 'busy';
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const PRESUME_FRESH_TTL_SEC = 30;
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const MAX_CACHE_TTL = 300; // 5 minutes
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const MAX_SIGNATURE_TTL = 60;
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const MAX_CACHE_RECENT = 2;
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const INITIATOR_USER = 1;
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const INITIATOR_JOB_OR_CLI = 2;
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/**
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* @param BagOStuff $cache
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* @param ILoadBalancer $lb
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* @param LoggerInterface $logger
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* @param StatsdDataFactoryInterface $stats
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* @param int $initiator Class INITIATOR__* constant
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*/
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public function __construct(
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BagOStuff $cache,
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ILoadBalancer $lb,
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LoggerInterface $logger,
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StatsdDataFactoryInterface $stats,
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$initiator
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) {
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$this->cache = $cache;
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$this->lb = $lb;
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$this->logger = $logger;
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$this->stats = $stats;
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$this->initiator = $initiator;
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}
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/**
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* @param WikiPage $page
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* @param Content $content Edit content
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* @param User $user
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* @param string $summary Edit summary
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* @return string Class ERROR_* constant
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*/
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public function parseAndCache( WikiPage $page, Content $content, User $user, $summary ) {
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$logger = $this->logger;
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$title = $page->getTitle();
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$key = $this->getStashKey( $title, $this->getContentHash( $content ), $user );
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$fname = __METHOD__;
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// Use the master DB to allow for fast blocking locks on the "save path" where this
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// value might actually be used to complete a page edit. If the edit submission request
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// happens before this edit stash requests finishes, then the submission will block until
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// the stash request finishes parsing. For the lock acquisition below, there is not much
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// need to duplicate parsing of the same content/user/summary bundle, so try to avoid
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// blocking at all here.
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$dbw = $this->lb->getConnection( DB_MASTER );
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if ( !$dbw->lock( $key, $fname, 0 ) ) {
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// De-duplicate requests on the same key
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return self::ERROR_BUSY;
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}
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/** @noinspection PhpUnusedLocalVariableInspection */
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$unlocker = new ScopedCallback( function () use ( $dbw, $key, $fname ) {
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$dbw->unlock( $key, $fname );
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} );
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$cutoffTime = time() - self::PRESUME_FRESH_TTL_SEC;
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// Reuse any freshly build matching edit stash cache
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$editInfo = $this->getStashValue( $key );
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if ( $editInfo && wfTimestamp( TS_UNIX, $editInfo->timestamp ) >= $cutoffTime ) {
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$alreadyCached = true;
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} else {
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$format = $content->getDefaultFormat();
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$editInfo = $page->prepareContentForEdit( $content, null, $user, $format, false );
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$editInfo->output->setCacheTime( $editInfo->timestamp );
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$alreadyCached = false;
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}
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$context = [ 'cachekey' => $key, 'title' => $title->getPrefixedText() ];
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if ( $editInfo && $editInfo->output ) {
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// Let extensions add ParserOutput metadata or warm other caches
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Hooks::run( 'ParserOutputStashForEdit',
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[ $page, $content, $editInfo->output, $summary, $user ] );
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if ( $alreadyCached ) {
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$logger->debug( "Parser output for key '{cachekey}' already cached.", $context );
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return self::ERROR_NONE;
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}
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$code = $this->storeStashValue(
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$key,
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$editInfo->pstContent,
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$editInfo->output,
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$editInfo->timestamp,
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$user
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);
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if ( $code === true ) {
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$logger->debug( "Cached parser output for key '{cachekey}'.", $context );
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return self::ERROR_NONE;
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} elseif ( $code === 'uncacheable' ) {
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$logger->info(
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"Uncacheable parser output for key '{cachekey}' [{code}].",
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$context + [ 'code' => $code ]
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);
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return self::ERROR_UNCACHEABLE;
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} else {
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$logger->error(
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"Failed to cache parser output for key '{cachekey}'.",
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$context + [ 'code' => $code ]
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);
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return self::ERROR_CACHE;
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}
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}
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return self::ERROR_PARSE;
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}
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/**
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* Check that a prepared edit is in cache and still up-to-date
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*
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* This method blocks if the prepared edit is already being rendered,
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* waiting until rendering finishes before doing final validity checks.
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*
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* The cache is rejected if template or file changes are detected.
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* Note that foreign template or file transclusions are not checked.
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*
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* This returns an object with the following fields:
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* - pstContent: the Content after pre-save-transform
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* - output: the ParserOutput instance
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* - timestamp: the timestamp of the parse
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* - edits: author edit count if they are logged in or NULL otherwise
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*
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* @param Title $title
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* @param Content $content
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* @param User $user User to get parser options from
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* @return stdClass|bool Returns edit stash object or false on cache miss
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*/
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public function checkCache( Title $title, Content $content, User $user ) {
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if (
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// The context is not an HTTP POST request
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!$user->getRequest()->wasPosted() ||
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// The context is a CLI script or a job runner HTTP POST request
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$this->initiator !== self::INITIATOR_USER ||
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// The editor account is a known bot
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$user->isBot()
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) {
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// Avoid wasted queries and statsd pollution
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return false;
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}
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$logger = $this->logger;
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$key = $this->getStashKey( $title, $this->getContentHash( $content ), $user );
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$context = [
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'key' => $key,
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'title' => $title->getPrefixedText(),
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'user' => $user->getName()
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];
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$editInfo = $this->getAndWaitForStashValue( $key );
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if ( !is_object( $editInfo ) || !$editInfo->output ) {
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$this->incrStatsByContent( 'cache_misses.no_stash', $content );
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if ( $this->recentStashEntryCount( $user ) > 0 ) {
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$logger->info( "Empty cache for key '{key}' but not for user.", $context );
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} else {
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$logger->debug( "Empty cache for key '{key}'.", $context );
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}
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return false;
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}
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$age = time() - wfTimestamp( TS_UNIX, $editInfo->output->getCacheTime() );
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$context['age'] = $age;
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$isCacheUsable = true;
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if ( $age <= self::PRESUME_FRESH_TTL_SEC ) {
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// Assume nothing changed in this time
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$this->incrStatsByContent( 'cache_hits.presumed_fresh', $content );
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$logger->debug( "Timestamp-based cache hit for key '{key}'.", $context );
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} elseif ( $user->isAnon() ) {
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$lastEdit = $this->lastEditTime( $user );
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$cacheTime = $editInfo->output->getCacheTime();
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if ( $lastEdit < $cacheTime ) {
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// Logged-out user made no local upload/template edits in the meantime
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$this->incrStatsByContent( 'cache_hits.presumed_fresh', $content );
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$logger->debug( "Edit check based cache hit for key '{key}'.", $context );
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} else {
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$isCacheUsable = false;
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$this->incrStatsByContent( 'cache_misses.proven_stale', $content );
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$logger->info( "Stale cache for key '{key}' due to outside edits.", $context );
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}
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} else {
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if ( $editInfo->edits === $user->getEditCount() ) {
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// Logged-in user made no local upload/template edits in the meantime
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$this->incrStatsByContent( 'cache_hits.presumed_fresh', $content );
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$logger->debug( "Edit count based cache hit for key '{key}'.", $context );
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} else {
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$isCacheUsable = false;
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$this->incrStatsByContent( 'cache_misses.proven_stale', $content );
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$logger->info( "Stale cache for key '{key}'due to outside edits.", $context );
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}
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}
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if ( !$isCacheUsable ) {
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return false;
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}
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if ( $editInfo->output->getFlag( 'vary-revision' ) ) {
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// This can be used for the initial parse, e.g. for filters or doEditContent(),
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// but a second parse will be triggered in doEditUpdates(). This is not optimal.
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$logger->info(
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"Cache for key '{key}' has vary_revision; post-insertion parse inevitable.",
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$context
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);
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} elseif ( $editInfo->output->getFlag( 'vary-revision-id' ) ) {
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// Similar to the above if we didn't guess the ID correctly.
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$logger->debug(
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"Cache for key '{key}' has vary_revision_id; post-insertion parse possible.",
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$context
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);
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}
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return $editInfo;
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}
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/**
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* @param string $subkey
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* @param Content $content
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*/
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private function incrStatsByContent( $subkey, Content $content ) {
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$this->stats->increment( 'editstash.' . $subkey ); // overall for b/c
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$this->stats->increment( 'editstash_by_model.' . $content->getModel() . '.' . $subkey );
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}
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/**
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* @param string $key
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* @return bool|stdClass
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*/
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private function getAndWaitForStashValue( $key ) {
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$editInfo = $this->getStashValue( $key );
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if ( !$editInfo ) {
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$start = microtime( true );
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// We ignore user aborts and keep parsing. Block on any prior parsing
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// so as to use its results and make use of the time spent parsing.
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// Skip this logic if there no master connection in case this method
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// is called on an HTTP GET request for some reason.
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$dbw = $this->lb->getAnyOpenConnection( $this->lb->getWriterIndex() );
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if ( $dbw && $dbw->lock( $key, __METHOD__, 30 ) ) {
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$editInfo = $this->getStashValue( $key );
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$dbw->unlock( $key, __METHOD__ );
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}
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$timeMs = 1000 * max( 0, microtime( true ) - $start );
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$this->stats->timing( 'editstash.lock_wait_time', $timeMs );
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}
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return $editInfo;
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}
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/**
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* @param string $textHash
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* @return string|bool Text or false if missing
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*/
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public function fetchInputText( $textHash ) {
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$textKey = $this->cache->makeKey( 'stashedit', 'text', $textHash );
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return $this->cache->get( $textKey );
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}
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/**
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* @param string $text
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* @param string $textHash
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* @return bool Success
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*/
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public function stashInputText( $text, $textHash ) {
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$textKey = $this->cache->makeKey( 'stashedit', 'text', $textHash );
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return $this->cache->set( $textKey, $text, self::MAX_CACHE_TTL );
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}
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/**
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* @param User $user
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* @return string|null TS_MW timestamp or null
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*/
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private function lastEditTime( User $user ) {
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$db = $this->lb->getConnection( DB_REPLICA );
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$actorQuery = ActorMigration::newMigration()->getWhere( $db, 'rc_user', $user, false );
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$time = $db->selectField(
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[ 'recentchanges' ] + $actorQuery['tables'],
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'MAX(rc_timestamp)',
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[ $actorQuery['conds'] ],
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__METHOD__,
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[],
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$actorQuery['joins']
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);
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return wfTimestampOrNull( TS_MW, $time );
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}
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/**
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* Get hash of the content, factoring in model/format
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*
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* @param Content $content
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* @return string
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*/
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private function getContentHash( Content $content ) {
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return sha1( implode( "\n", [
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$content->getModel(),
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$content->getDefaultFormat(),
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$content->serialize( $content->getDefaultFormat() )
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] ) );
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}
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/**
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* Get the temporary prepared edit stash key for a user
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*
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* This key can be used for caching prepared edits provided:
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* - a) The $user was used for PST options
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* - b) The parser output was made from the PST using cannonical matching options
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*
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* @param Title $title
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* @param string $contentHash Result of getContentHash()
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* @param User $user User to get parser options from
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* @return string
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*/
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private function getStashKey( Title $title, $contentHash, User $user ) {
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return $this->cache->makeKey(
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'stashed-edit-info',
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md5( $title->getPrefixedDBkey() ),
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// Account for the edit model/text
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$contentHash,
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// Account for user name related variables like signatures
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md5( $user->getId() . "\n" . $user->getName() )
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);
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}
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/**
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* @param string $hash
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* @return string
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*/
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private function getStashParserOutputKey( $hash ) {
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return $this->cache->makeKey( 'stashed-edit-output', $hash );
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}
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/**
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* @param string $key
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* @return stdClass|bool Object map (pstContent,output,outputID,timestamp,edits) or false
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*/
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private function getStashValue( $key ) {
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$stashInfo = $this->cache->get( $key );
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if ( !is_object( $stashInfo ) ) {
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return false;
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}
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$parserOutputKey = $this->getStashParserOutputKey( $stashInfo->outputID );
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$parserOutput = $this->cache->get( $parserOutputKey );
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if ( $parserOutput instanceof ParserOutput ) {
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$stashInfo->output = $parserOutput;
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return $stashInfo;
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}
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return false;
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}
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/**
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* Build a value to store in memcached based on the PST content and parser output
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*
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* This makes a simple version of WikiPage::prepareContentForEdit() as stash info
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*
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* @param string $key
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* @param Content $pstContent Pre-Save transformed content
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* @param ParserOutput $parserOutput
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* @param string $timestamp TS_MW
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* @param User $user
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* @return string|bool True or an error code
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*/
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private function storeStashValue(
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$key,
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Content $pstContent,
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ParserOutput $parserOutput,
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$timestamp,
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User $user
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) {
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// If an item is renewed, mind the cache TTL determined by config and parser functions.
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// Put an upper limit on the TTL for sanity to avoid extreme template/file staleness.
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$age = time() - wfTimestamp( TS_UNIX, $parserOutput->getCacheTime() );
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$ttl = min( $parserOutput->getCacheExpiry() - $age, self::MAX_CACHE_TTL );
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// Avoid extremely stale user signature timestamps (T84843)
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if ( $parserOutput->getFlag( 'user-signature' ) ) {
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$ttl = min( $ttl, self::MAX_SIGNATURE_TTL );
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}
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if ( $ttl <= 0 ) {
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return 'uncacheable'; // low TTL due to a tag, magic word, or signature?
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}
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// Store what is actually needed and split the output into another key (T204742)
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$parserOutputID = md5( $key );
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$stashInfo = (object)[
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'pstContent' => $pstContent,
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'outputID' => $parserOutputID,
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'timestamp' => $timestamp,
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'edits' => $user->getEditCount()
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];
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$ok = $this->cache->set( $key, $stashInfo, $ttl );
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if ( $ok ) {
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$ok = $this->cache->set(
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$this->getStashParserOutputKey( $parserOutputID ),
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$parserOutput,
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$ttl
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);
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}
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if ( $ok ) {
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// These blobs can waste slots in low cardinality memcached slabs
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$this->pruneExcessStashedEntries( $user, $key );
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}
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return $ok ? true : 'store_error';
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}
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/**
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* @param User $user
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* @param string $newKey
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*/
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private function pruneExcessStashedEntries( User $user, $newKey ) {
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$key = $this->cache->makeKey( 'stash-edit-recent', sha1( $user->getName() ) );
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$keyList = $this->cache->get( $key ) ?: [];
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if ( count( $keyList ) >= self::MAX_CACHE_RECENT ) {
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$oldestKey = array_shift( $keyList );
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$this->cache->delete( $oldestKey );
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}
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$keyList[] = $newKey;
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$this->cache->set( $key, $keyList, 2 * self::MAX_CACHE_TTL );
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}
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/**
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* @param User $user
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* @return int
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*/
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private function recentStashEntryCount( User $user ) {
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$key = $this->cache->makeKey( 'stash-edit-recent', sha1( $user->getName() ) );
|
|
|
|
return count( $this->cache->get( $key ) ?: [] );
|
|
}
|
|
}
|