PageEditStash.php
No OneTemporary
Actions

Size

18 KB

Referenced Files

None

Subscribers

None

PageEditStash.php
View Options

	<?php
	/**
	* 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
	*/

	namespace MediaWiki\Storage;

	use MediaWiki\Content\Content;
	use MediaWiki\HookContainer\HookContainer;
	use MediaWiki\HookContainer\HookRunner;
	use MediaWiki\Page\PageIdentity;
	use MediaWiki\Page\WikiPageFactory;
	use MediaWiki\Parser\ParserOutput;
	use MediaWiki\Parser\ParserOutputFlags;
	use MediaWiki\Revision\SlotRecord;
	use MediaWiki\Storage\Hook\ParserOutputStashForEditHook;
	use MediaWiki\User\UserEditTracker;
	use MediaWiki\User\UserFactory;
	use MediaWiki\User\UserIdentity;
	use Psr\Log\LoggerInterface;
	use stdClass;
	use Wikimedia\ObjectCache\BagOStuff;
	use Wikimedia\Rdbms\IConnectionProvider;
	use Wikimedia\ScopedCallback;
	use Wikimedia\Stats\StatsFactory;
	use WikiPage;

	/**
	* Manage the pre-emptive page parsing for edits to wiki pages.
	*
	* This is written to by ApiStashEdit, and consumed by ApiEditPage
	* and EditPage (via PageUpdaterFactory and DerivedPageDataUpdater).
	*
	* See also mediawiki.action.edit/stash.js.
	*
	* @since 1.34
	* @ingroup Page
	*/
	class PageEditStash {
	/** @var BagOStuff */
	private $cache;
	/** @var IConnectionProvider */
	private $dbProvider;
	/** @var LoggerInterface */
	private $logger;
	/** @var StatsFactory */
	private $stats;
	/** @var ParserOutputStashForEditHook */
	private $hookRunner;
	/** @var UserEditTracker */
	private $userEditTracker;
	/** @var UserFactory */
	private $userFactory;
	/** @var WikiPageFactory */
	private $wikiPageFactory;
	/** @var int */
	private $initiator;

	public const ERROR_NONE = 'stashed';
	public const ERROR_PARSE = 'error_parse';
	public const ERROR_CACHE = 'error_cache';
	public const ERROR_UNCACHEABLE = 'uncacheable';
	public const ERROR_BUSY = 'busy';

	public const PRESUME_FRESH_TTL_SEC = 30;
	public const MAX_CACHE_TTL = 300; // 5 minutes
	public const MAX_SIGNATURE_TTL = 60;

	private const MAX_CACHE_RECENT = 2;

	public const INITIATOR_USER = 1;
	public const INITIATOR_JOB_OR_CLI = 2;

	/**
	* @param BagOStuff $cache
	* @param IConnectionProvider $dbProvider
	* @param LoggerInterface $logger
	* @param StatsFactory $stats
	* @param UserEditTracker $userEditTracker
	* @param UserFactory $userFactory
	* @param WikiPageFactory $wikiPageFactory
	* @param HookContainer $hookContainer
	* @param int $initiator Class INITIATOR__* constant
	*/
	public function __construct(
	BagOStuff $cache,
	IConnectionProvider $dbProvider,
	LoggerInterface $logger,
	StatsFactory $stats,
	UserEditTracker $userEditTracker,
	UserFactory $userFactory,
	WikiPageFactory $wikiPageFactory,
	HookContainer $hookContainer,
	$initiator
	) {
	$this->cache = $cache;
	$this->dbProvider = $dbProvider;
	$this->logger = $logger;
	$this->stats = $stats;
	$this->userEditTracker = $userEditTracker;
	$this->userFactory = $userFactory;
	$this->wikiPageFactory = $wikiPageFactory;
	$this->hookRunner = new HookRunner( $hookContainer );
	$this->initiator = $initiator;
	}

	/**
	* @param PageUpdater $pageUpdater (a WikiPage instance is also supported but deprecated)
	* @param Content $content Edit content
	* @param UserIdentity $user
	* @param string $summary Edit summary
	* @return string Class ERROR_* constant
	*/
	public function parseAndCache( $pageUpdater, Content $content, UserIdentity $user, string $summary ) {
	$logger = $this->logger;

	if ( $pageUpdater instanceof WikiPage ) {
	wfDeprecated( __METHOD__ . ' with WikiPage instance', '1.42' );
	$pageUpdater = $pageUpdater->newPageUpdater( $user );
	}

	$page = $pageUpdater->getPage();
	$key = $this->getStashKey( $page, $this->getContentHash( $content ), $user );
	$fname = __METHOD__;

	// Use the primary DB to allow for fast blocking locks on the "save path" where this
	// value might actually be used to complete a page edit. If the edit submission request
	// happens before this edit stash requests finishes, then the submission will block until
	// the stash request finishes parsing. For the lock acquisition below, there is not much
	// need to duplicate parsing of the same content/user/summary bundle, so try to avoid
	// blocking at all here.
	$dbw = $this->dbProvider->getPrimaryDatabase();
	if ( !$dbw->lock( $key, $fname, 0 ) ) {
	// De-duplicate requests on the same key
	return self::ERROR_BUSY;
	}
	/** @noinspection PhpUnusedLocalVariableInspection */
	$unlocker = new ScopedCallback( static function () use ( $dbw, $key, $fname ) {
	$dbw->unlock( $key, $fname );
	} );

	$cutoffTime = time() - self::PRESUME_FRESH_TTL_SEC;

	// Reuse any freshly build matching edit stash cache
	$editInfo = $this->getStashValue( $key );
	if ( $editInfo && (int)wfTimestamp( TS_UNIX, $editInfo->timestamp ) >= $cutoffTime ) {
	$alreadyCached = true;
	} else {
	$pageUpdater->setContent( SlotRecord::MAIN, $content );

	$update = $pageUpdater->prepareUpdate( EDIT_INTERNAL ); // applies pre-safe transform
	$output = $update->getCanonicalParserOutput(); // causes content to be parsed
	$output->setCacheTime( $update->getRevision()->getTimestamp() );

	// emulate a cache value that kind of looks like a PreparedEdit, for use below
	$editInfo = (object)[
	'pstContent' => $update->getRawContent( SlotRecord::MAIN ),
	'output' => $output,
	'timestamp' => $output->getCacheTime()
	];

	$alreadyCached = false;
	}

	$logContext = [ 'cachekey' => $key, 'title' => (string)$page ];

	if ( $editInfo->output ) {
	// Let extensions add ParserOutput metadata or warm other caches
	$legacyUser = $this->userFactory->newFromUserIdentity( $user );
	$legacyPage = $this->wikiPageFactory->newFromTitle( $page );
	$this->hookRunner->onParserOutputStashForEdit(
	$legacyPage, $content, $editInfo->output, $summary, $legacyUser );

	if ( $alreadyCached ) {
	$logger->debug( "Parser output for key '{cachekey}' already cached.", $logContext );

	return self::ERROR_NONE;
	}

	$code = $this->storeStashValue(
	$key,
	$editInfo->pstContent,
	$editInfo->output,
	$editInfo->timestamp,
	$user
	);

	if ( $code === true ) {
	$logger->debug( "Cached parser output for key '{cachekey}'.", $logContext );

	return self::ERROR_NONE;
	} elseif ( $code === 'uncacheable' ) {
	$logger->info(
	"Uncacheable parser output for key '{cachekey}' [{code}].",
	$logContext + [ 'code' => $code ]
	);

	return self::ERROR_UNCACHEABLE;
	} else {
	$logger->error(
	"Failed to cache parser output for key '{cachekey}'.",
	$logContext + [ 'code' => $code ]
	);

	return self::ERROR_CACHE;
	}
	}

	return self::ERROR_PARSE;
	}

	/**
	* Check that a prepared edit is in cache and still up-to-date
	*
	* This method blocks if the prepared edit is already being rendered,
	* waiting until rendering finishes before doing final validity checks.
	*
	* The cache is rejected if template or file changes are detected.
	* Note that foreign template or file transclusions are not checked.
	*
	* This returns an object with the following fields:
	* - pstContent: the Content after pre-save-transform
	* - output: the ParserOutput instance
	* - timestamp: the timestamp of the parse
	* - edits: author edit count if they are logged in or NULL otherwise
	*
	* @param PageIdentity $page
	* @param Content $content
	* @param UserIdentity $user to get parser options from
	* @return stdClass\|false Returns edit stash object or false on cache miss
	*/
	public function checkCache( PageIdentity $page, Content $content, UserIdentity $user ) {
	$legacyUser = $this->userFactory->newFromUserIdentity( $user );
	if (
	// The context is not an HTTP POST request
	!$legacyUser->getRequest()->wasPosted() \|\|
	// The context is a CLI script or a job runner HTTP POST request
	$this->initiator !== self::INITIATOR_USER \|\|
	// The editor account is a known bot
	$legacyUser->isBot()
	) {
	// Avoid wasted queries and statsd pollution
	return false;
	}

	$logger = $this->logger;

	$key = $this->getStashKey( $page, $this->getContentHash( $content ), $user );
	$logContext = [
	'key' => $key,
	'title' => (string)$page,
	'user' => $user->getName()
	];

	$editInfo = $this->getAndWaitForStashValue( $key );
	if ( !is_object( $editInfo ) \|\| !$editInfo->output ) {
	$this->incrCacheReadStats( 'miss', 'no_stash', $content );
	if ( $this->recentStashEntryCount( $user ) > 0 ) {
	$logger->info( "Empty cache for key '{key}' but not for user.", $logContext );
	} else {
	$logger->debug( "Empty cache for key '{key}'.", $logContext );
	}

	return false;
	}

	$age = time() - (int)wfTimestamp( TS_UNIX, $editInfo->output->getCacheTime() );
	$logContext['age'] = $age;

	$isCacheUsable = true;
	if ( $age <= self::PRESUME_FRESH_TTL_SEC ) {
	// Assume nothing changed in this time
	$this->incrCacheReadStats( 'hit', 'presumed_fresh', $content );
	$logger->debug( "Timestamp-based cache hit for key '{key}'.", $logContext );
	} elseif ( !$user->isRegistered() ) {
	$lastEdit = $this->lastEditTime( $user );
	$cacheTime = $editInfo->output->getCacheTime();
	if ( $lastEdit < $cacheTime ) {
	// Logged-out user made no local upload/template edits in the meantime
	$this->incrCacheReadStats( 'hit', 'presumed_fresh', $content );
	$logger->debug( "Edit check based cache hit for key '{key}'.", $logContext );
	} else {
	$isCacheUsable = false;
	$this->incrCacheReadStats( 'miss', 'proven_stale', $content );
	$logger->info( "Stale cache for key '{key}' due to outside edits.", $logContext );
	}
	} else {
	if ( $editInfo->edits === $this->userEditTracker->getUserEditCount( $user ) ) {
	// Logged-in user made no local upload/template edits in the meantime
	$this->incrCacheReadStats( 'hit', 'presumed_fresh', $content );
	$logger->debug( "Edit count based cache hit for key '{key}'.", $logContext );
	} else {
	$isCacheUsable = false;
	$this->incrCacheReadStats( 'miss', 'proven_stale', $content );
	$logger->info( "Stale cache for key '{key}'due to outside edits.", $logContext );
	}
	}

	if ( !$isCacheUsable ) {
	return false;
	}

	if ( $editInfo->output->getOutputFlag( ParserOutputFlags::VARY_REVISION ) ) {
	// This can be used for the initial parse, e.g. for filters or doUserEditContent(),
	// but a second parse will be triggered in doEditUpdates() no matter what
	$logger->info(
	"Cache for key '{key}' has vary-revision; post-insertion parse inevitable.",
	$logContext
	);
	} else {
	static $flagsMaybeReparse = [
	// Similar to the above if we didn't guess the ID correctly
	ParserOutputFlags::VARY_REVISION_ID,
	// Similar to the above if we didn't guess the timestamp correctly
	ParserOutputFlags::VARY_REVISION_TIMESTAMP,
	// Similar to the above if we didn't guess the content correctly
	ParserOutputFlags::VARY_REVISION_SHA1,
	// Similar to the above if we didn't guess page ID correctly
	ParserOutputFlags::VARY_PAGE_ID,
	];
	foreach ( $flagsMaybeReparse as $flag ) {
	if ( $editInfo->output->getOutputFlag( $flag ) ) {
	$logger->debug(
	"Cache for key '{key}' has $flag; post-insertion parse possible.",
	$logContext
	);
	}
	}
	}

	return $editInfo;
	}

	/**
	* @param string $result
	* @param string $reason
	* @param Content $content
	*/
	private function incrCacheReadStats( $result, $reason, Content $content ) {
	static $subtypeByResult = [ 'miss' => 'cache_misses', 'hit' => 'cache_hits' ];
	$this->stats->getCounter( "editstash_cache_checks_total" )
	->setLabel( 'reason', $reason )
	->setLabel( 'result', $result )
	->setLabel( 'model', $content->getModel() )
	->copyToStatsdAt( [
	'editstash.' . $subtypeByResult[ $result ] . '.' . $reason,
	'editstash_by_model.' . $content->getModel() . '.' . $subtypeByResult[ $result ] . '.' . $reason ] )
	->increment();
	}

	/**
	* @param string $key
	* @return bool\|stdClass
	*/
	private function getAndWaitForStashValue( $key ) {
	$editInfo = $this->getStashValue( $key );

	if ( !$editInfo ) {
	$start = microtime( true );
	// We ignore user aborts and keep parsing. Block on any prior parsing
	// so as to use its results and make use of the time spent parsing.
	$dbw = $this->dbProvider->getPrimaryDatabase();
	if ( $dbw->lock( $key, __METHOD__, 30 ) ) {
	$editInfo = $this->getStashValue( $key );
	$dbw->unlock( $key, __METHOD__ );
	}

	$timeMs = 1000 * max( 0, microtime( true ) - $start );
	$this->stats->getTiming( 'editstash_lock_wait_seconds' )
	->copyToStatsdAt( 'editstash.lock_wait_time' )
	->observe( $timeMs );
	}

	return $editInfo;
	}

	/**
	* @param string $textHash
	* @return string\|bool Text or false if missing
	*/
	public function fetchInputText( $textHash ) {
	$textKey = $this->cache->makeKey( 'stashedit', 'text', $textHash );

	return $this->cache->get( $textKey );
	}

	/**
	* @param string $text
	* @param string $textHash
	* @return bool Success
	*/
	public function stashInputText( $text, $textHash ) {
	$textKey = $this->cache->makeKey( 'stashedit', 'text', $textHash );

	return $this->cache->set(
	$textKey,
	$text,
	self::MAX_CACHE_TTL,
	BagOStuff::WRITE_ALLOW_SEGMENTS
	);
	}

	/**
	* @param UserIdentity $user
	* @return string\|null TS_MW timestamp or null
	*/
	private function lastEditTime( UserIdentity $user ) {
	$time = $this->dbProvider->getReplicaDatabase()->newSelectQueryBuilder()
	->select( 'MAX(rc_timestamp)' )
	->from( 'recentchanges' )
	->join( 'actor', null, 'actor_id=rc_actor' )
	->where( [ 'actor_name' => $user->getName() ] )
	->caller( __METHOD__ )
	->fetchField();

	return wfTimestampOrNull( TS_MW, $time );
	}

	/**
	* Get hash of the content, factoring in model/format
	*
	* @param Content $content
	* @return string
	*/
	private function getContentHash( Content $content ) {
	return sha1( implode( "\n", [
	$content->getModel(),
	$content->getDefaultFormat(),
	$content->serialize( $content->getDefaultFormat() )
	] ) );
	}

	/**
	* Get the temporary prepared edit stash key for a user
	*
	* This key can be used for caching prepared edits provided:
	* - a) The $user was used for PST options
	* - b) The parser output was made from the PST using cannonical matching options
	*
	* @param PageIdentity $page
	* @param string $contentHash Result of getContentHash()
	* @param UserIdentity $user User to get parser options from
	* @return string
	*/
	private function getStashKey( PageIdentity $page, $contentHash, UserIdentity $user ) {
	return $this->cache->makeKey(
	'stashedit-info-v2',
	md5( "{$page->getNamespace()}\n{$page->getDBkey()}" ),
	// Account for the edit model/text
	$contentHash,
	// Account for user name related variables like signatures
	md5( "{$user->getId()}\n{$user->getName()}" )
	);
	}

	/**
	* @param string $key
	* @return stdClass\|bool Object map (pstContent,output,outputID,timestamp,edits) or false
	*/
	private function getStashValue( $key ) {
	$serial = $this->cache->get( $key );

	return $this->unserializeStashInfo( $serial );
	}

	/**
	* Build a value to store in memcached based on the PST content and parser output
	*
	* This makes a simple version of WikiPage::prepareContentForEdit() as stash info
	*
	* @param string $key
	* @param Content $pstContent Pre-Save transformed content
	* @param ParserOutput $parserOutput
	* @param string $timestamp TS_MW
	* @param UserIdentity $user
	* @return string\|bool True or an error code
	*/
	private function storeStashValue(
	$key,
	Content $pstContent,
	ParserOutput $parserOutput,
	$timestamp,
	UserIdentity $user
	) {
	// If an item is renewed, mind the cache TTL determined by config and parser functions.
	// Put an upper limit on the TTL to avoid extreme template/file staleness.
	$age = time() - (int)wfTimestamp( TS_UNIX, $parserOutput->getCacheTime() );
	$ttl = min( $parserOutput->getCacheExpiry() - $age, self::MAX_CACHE_TTL );
	// Avoid extremely stale user signature timestamps (T84843)
	if ( $parserOutput->getOutputFlag( ParserOutputFlags::USER_SIGNATURE ) ) {
	$ttl = min( $ttl, self::MAX_SIGNATURE_TTL );
	}

	if ( $ttl <= 0 ) {
	return 'uncacheable'; // low TTL due to a tag, magic word, or signature?
	}

	// Store what is actually needed and split the output into another key (T204742)
	$stashInfo = (object)[
	'pstContent' => $pstContent,
	'output' => $parserOutput,
	'timestamp' => $timestamp,
	'edits' => $this->userEditTracker->getUserEditCount( $user ),
	];
	$serial = $this->serializeStashInfo( $stashInfo );
	if ( $serial === false ) {
	return 'store_error';
	}

	$ok = $this->cache->set( $key, $serial, $ttl, BagOStuff::WRITE_ALLOW_SEGMENTS );
	if ( $ok ) {
	// These blobs can waste slots in low cardinality memcached slabs
	$this->pruneExcessStashedEntries( $user, $key );
	}

	return $ok ? true : 'store_error';
	}

	/**
	* @param UserIdentity $user
	* @param string $newKey
	*/
	private function pruneExcessStashedEntries( UserIdentity $user, $newKey ) {
	$key = $this->cache->makeKey( 'stash-edit-recent', sha1( $user->getName() ) );

	$keyList = $this->cache->get( $key ) ?: [];
	if ( count( $keyList ) >= self::MAX_CACHE_RECENT ) {
	$oldestKey = array_shift( $keyList );
	$this->cache->delete( $oldestKey, BagOStuff::WRITE_ALLOW_SEGMENTS );
	}

	$keyList[] = $newKey;
	$this->cache->set( $key, $keyList, 2 * self::MAX_CACHE_TTL );
	}

	/**
	* @param UserIdentity $user
	* @return int
	*/
	private function recentStashEntryCount( UserIdentity $user ) {
	$key = $this->cache->makeKey( 'stash-edit-recent', sha1( $user->getName() ) );

	return count( $this->cache->get( $key ) ?: [] );
	}

	private function serializeStashInfo( stdClass $stashInfo ) {
	// @todo: use JSON with ParserOutput and Content
	return serialize( $stashInfo );
	}

	private function unserializeStashInfo( $serial ) {
	if ( is_string( $serial ) ) {
	// @todo: use JSON with ParserOutput and Content
	$stashInfo = unserialize( $serial );
	if ( is_object( $stashInfo ) && $stashInfo->output instanceof ParserOutput ) {
	return $stashInfo;
	}
	}

	return false;
	}
	}

File Metadata

Mime Type: text/x-php
Expires: Wed, Aug 19, 01:12 (2 w, 1 d ago)
Storage Engine: local-disk
Storage Format: Raw Data
Storage Handle: a3/86/3b3882f9caf75c6299435d9a51b5
Default Alt Text: PageEditStash.php (18 KB)

PageEditStash.phpNo OneTemporaryActions

PageEditStash.phpView Options

File Metadata

Event Timeline

PageEditStash.php
No OneTemporary
Actions

PageEditStash.php
View Options