ParserCache.php
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ParserCache.php
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	<?php
	/**
	* Cache for outputs of the PHP parser
	*
	* 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 Parser
	*/

	namespace MediaWiki\Parser;

	use Exception;
	use InvalidArgumentException;
	use JsonException;
	use MediaWiki\HookContainer\HookContainer;
	use MediaWiki\HookContainer\HookRunner;
	use MediaWiki\Json\JsonCodec;
	use MediaWiki\Page\PageRecord;
	use MediaWiki\Page\WikiPageFactory;
	use MediaWiki\Title\TitleFactory;
	use Psr\Log\LoggerInterface;
	use Wikimedia\ObjectCache\BagOStuff;
	use Wikimedia\ObjectCache\EmptyBagOStuff;
	use Wikimedia\ObjectCache\HashBagOStuff;
	use Wikimedia\Stats\StatsFactory;
	use Wikimedia\UUID\GlobalIdGenerator;

	/**
	* Cache for ParserOutput objects corresponding to the latest page revisions.
	*
	* The ParserCache is a two-tiered cache backed by BagOStuff which supports
	* varying the stored content on the values of ParserOptions used during
	* a page parse.
	*
	* First tier is keyed by the page ID and stores ParserCacheMetadata, which
	* contains information about cache expiration and the list of ParserOptions
	* used during the parse of the page. For example, if only 'dateformat' and
	* 'userlang' options were accessed by the parser when producing output for the
	* page, array [ 'dateformat', 'userlang' ] will be stored in the metadata cache.
	* This means none of the other existing options had any effect on the output.
	*
	* The second tier of the cache contains ParserOutput objects. The key for the
	* second tier is constructed from the page ID and values of those ParserOptions
	* used during a page parse which affected the output. Upon cache lookup, the list
	* of used option names is retrieved from tier 1 cache, and only the values of
	* those options are hashed together with the page ID to produce a key, while
	* the rest of the options are ignored. Following the example above where
	* only [ 'dateformat', 'userlang' ] options changed the parser output for a
	* page, the key will look like 'page_id!dateformat=default:userlang=ru'.
	* Thus any cache lookup with dateformat=default and userlang=ru will hit the
	* same cache entry regardless of the values of the rest of the options, since they
	* were not accessed during a parse and thus did not change the output.
	*
	* @see ParserOutput::recordOption()
	* @see ParserOutput::getUsedOptions()
	* @see ParserOptions::allCacheVaryingOptions()
	* @ingroup Cache Parser
	*/
	class ParserCache {
	/**
	* Constants for self::getKey()
	* @since 1.30
	* @since 1.36 the constants were made public
	*/

	/** Use only current data */
	public const USE_CURRENT_ONLY = 0;

	/** Use expired data if current data is unavailable */
	public const USE_EXPIRED = 1;

	/** Use expired data or data from different revisions if current data is unavailable */
	public const USE_OUTDATED = 2;

	/**
	* Use expired data and data from different revisions, and if all else
	* fails vary on all variable options
	*/
	private const USE_ANYTHING = 3;

	/** @var string The name of this ParserCache. Used as a root of the cache key. */
	private $name;

	/** @var BagOStuff */
	private $cache;

	/**
	* Anything cached prior to this is invalidated
	*
	* @var string
	*/
	private $cacheEpoch;

	/** @var HookRunner */
	private $hookRunner;

	/** @var JsonCodec */
	private $jsonCodec;

	/** @var StatsFactory */
	private $stats;

	/** @var LoggerInterface */
	private $logger;

	/** @var TitleFactory */
	private $titleFactory;

	/** @var WikiPageFactory */
	private $wikiPageFactory;

	private ?ParserCacheFilter $filter = null;

	private GlobalIdGenerator $globalIdGenerator;

	/**
	* @var BagOStuff small in-process cache to store metadata.
	* It's needed multiple times during the request, for example
	* to build a PoolWorkArticleView key, and then to fetch the
	* actual ParserCache entry.
	*/
	private $metadataProcCache;

	/**
	* Setup a cache pathway with a given back-end storage mechanism.
	*
	* This class use an invalidation strategy that is compatible with
	* MultiWriteBagOStuff in async replication mode.
	*
	* @param string $name
	* @param BagOStuff $cache
	* @param string $cacheEpoch Anything before this timestamp is invalidated
	* @param HookContainer $hookContainer
	* @param JsonCodec $jsonCodec
	* @param StatsFactory $stats
	* @param LoggerInterface $logger
	* @param TitleFactory $titleFactory
	* @param WikiPageFactory $wikiPageFactory
	* @param GlobalIdGenerator $globalIdGenerator
	*/
	public function __construct(
	string $name,
	BagOStuff $cache,
	string $cacheEpoch,
	HookContainer $hookContainer,
	JsonCodec $jsonCodec,
	StatsFactory $stats,
	LoggerInterface $logger,
	TitleFactory $titleFactory,
	WikiPageFactory $wikiPageFactory,
	GlobalIdGenerator $globalIdGenerator
	) {
	$this->name = $name;
	$this->cache = $cache;
	$this->cacheEpoch = $cacheEpoch;
	$this->hookRunner = new HookRunner( $hookContainer );
	$this->jsonCodec = $jsonCodec;
	$this->stats = $stats;
	$this->logger = $logger;
	$this->titleFactory = $titleFactory;
	$this->wikiPageFactory = $wikiPageFactory;
	$this->globalIdGenerator = $globalIdGenerator;
	$this->metadataProcCache = new HashBagOStuff( [ 'maxKeys' => 2 ] );
	}

	/**
	* @since 1.41
	* @param ParserCacheFilter $filter
	*/
	public function setFilter( ParserCacheFilter $filter ): void {
	$this->filter = $filter;
	}

	/**
	* @param PageRecord $page
	* @since 1.28
	*/
	public function deleteOptionsKey( PageRecord $page ) {
	$page->assertWiki( PageRecord::LOCAL );
	$key = $this->makeMetadataKey( $page );
	$this->metadataProcCache->delete( $key );
	$this->cache->delete( $key );
	}

	/**
	* Retrieve the ParserOutput from ParserCache, even if it's outdated.
	* @param PageRecord $page
	* @param ParserOptions $popts
	* @return ParserOutput\|false
	*/
	public function getDirty( PageRecord $page, $popts ) {
	$page->assertWiki( PageRecord::LOCAL );
	$value = $this->get( $page, $popts, true );
	return is_object( $value ) ? $value : false;
	}

	/**
	* @param PageRecord $page
	* @return string
	*/
	private function getContentModelFromPage( PageRecord $page ) {
	$wikiPage = $this->wikiPageFactory->newFromTitle( $page );
	return str_replace( '.', '_', $wikiPage->getContentModel() );
	}

	/**
	* @param PageRecord $page
	* @param string $status
	* @param string\|null $reason
	*/
	private function incrementStats( PageRecord $page, $status, $reason = null ) {
	$contentModel = $this->getContentModelFromPage( $page );
	$metricSuffix = $reason ? "{$status}_{$reason}" : $status;

	$this->stats->getCounter( 'ParserCache_operation_total' )
	->setLabel( 'name', $this->name )
	->setLabel( 'contentModel', $contentModel )
	->setLabel( 'status', $status )
	->setLabel( 'reason', $reason ?: 'n/a' )
	->copyToStatsdAt( "{$this->name}.{$contentModel}.{$metricSuffix}" )
	->increment();
	}

	/**
	* @param PageRecord $page
	* @param string $renderReason
	*/
	private function incrementRenderReasonStats( PageRecord $page, $renderReason ) {
	$contentModel = $this->getContentModelFromPage( $page );
	$renderReason = preg_replace( '/\W+/', '_', $renderReason );

	$this->stats->getCounter( 'ParserCache_render_total' )
	->setLabel( 'name', $this->name )
	->setLabel( 'contentModel', $contentModel )
	->setLabel( 'reason', $renderReason )
	->copyToStatsdAt( "{$this->name}.{$contentModel}.reason.{$renderReason}" )
	->increment();
	}

	/**
	* Returns the ParserCache metadata about the given page
	* considering the given options.
	*
	* @note Which parser options influence the cache key
	* is controlled via ParserOutput::recordOption() or
	* ParserOptions::addExtraKey().
	*
	* @param PageRecord $page
	* @param int $staleConstraint one of the self::USE_ constants
	* @return ParserCacheMetadata\|null
	* @since 1.36
	*/
	public function getMetadata(
	PageRecord $page,
	int $staleConstraint = self::USE_ANYTHING
	): ?ParserCacheMetadata {
	$page->assertWiki( PageRecord::LOCAL );

	$pageKey = $this->makeMetadataKey( $page );
	$metadata = $this->metadataProcCache->get( $pageKey );
	if ( !$metadata ) {
	$metadata = $this->cache->get(
	$pageKey,
	BagOStuff::READ_VERIFIED
	);
	}

	if ( $metadata === false ) {
	$this->incrementStats( $page, 'miss', 'absent_metadata' );
	$this->logger->debug( 'ParserOutput metadata cache miss', [ 'name' => $this->name ] );
	return null;
	} else {
	// Ensure this cache hit is present in the in-process cache (T277829)
	$this->metadataProcCache->set( $pageKey, $metadata );
	}

	// NOTE: If the value wasn't serialized to JSON when being stored,
	// we may already have a ParserOutput object here. This used
	// to be the default behavior before 1.36. We need to retain
	// support so we can handle cached objects after an update
	// from an earlier revision.
	// NOTE: Support for reading string values from the cache must be
	// deployed a while before starting to write JSON to the cache,
	// in case we have to revert either change.
	if ( is_string( $metadata ) ) {
	$metadata = $this->restoreFromJson( $metadata, $pageKey, CacheTime::class );
	}

	if ( !$metadata instanceof CacheTime ) {
	$this->incrementStats( $page, 'miss', 'unserialize' );
	return null;
	}

	if ( $this->checkExpired( $metadata, $page, $staleConstraint, 'metadata' ) ) {
	return null;
	}

	if ( $this->checkOutdated( $metadata, $page, $staleConstraint, 'metadata' ) ) {
	return null;
	}

	$this->logger->debug( 'Parser cache options found', [ 'name' => $this->name ] );
	return $metadata;
	}

	private function makeMetadataKey( PageRecord $page ): string {
	return $this->cache->makeKey( $this->name, $page->getId( PageRecord::LOCAL ), '\|#\|', 'idoptions' );
	}

	/**
	* Get a key that will be used by the ParserCache to store the content
	* for a given page considering the given options and the array of
	* used options.
	*
	* @warning The exact format of the key is considered internal and is subject
	* to change, thus should not be used as storage or long-term caching key.
	* This is intended to be used for logging or keying something transient.
	*
	* @param PageRecord $page
	* @param ParserOptions $options
	* @param array\|null $usedOptions Defaults to all cache varying options.
	* @return string
	* @internal
	* @since 1.36
	*/
	public function makeParserOutputKey(
	PageRecord $page,
	ParserOptions $options,
	?array $usedOptions = null
	): string {
	$usedOptions ??= ParserOptions::allCacheVaryingOptions();
	$title = $this->titleFactory->newFromPageIdentity( $page );
	$hash = $options->optionsHash( $usedOptions, $title );
	// idhash seem to mean 'page id' + 'rendering hash' (r3710)
	return $this->cache->makeKey( $this->name, $page->getId( PageRecord::LOCAL ), '\|#\|', 'idhash', $hash );
	}

	/**
	* Retrieve the ParserOutput from ParserCache.
	* false if not found or outdated.
	*
	* @param PageRecord $page
	* @param ParserOptions $popts
	* @param bool $useOutdated (default false)
	*
	* @return ParserOutput\|false
	*/
	public function get( PageRecord $page, $popts, $useOutdated = false ) {
	$page->assertWiki( PageRecord::LOCAL );

	if ( !$page->exists() ) {
	$this->incrementStats( $page, 'miss', 'nonexistent' );
	return false;
	}

	$staleConstraint = $useOutdated ? self::USE_OUTDATED : self::USE_CURRENT_ONLY;
	$parserOutputMetadata = $this->getMetadata( $page, $staleConstraint );
	if ( !$parserOutputMetadata ) {
	return false;
	}

	if ( !$popts->isSafeToCache( $parserOutputMetadata->getUsedOptions() ) ) {
	$this->incrementStats( $page, 'miss', 'unsafe' );
	return false;
	}

	$parserOutputKey = $this->makeParserOutputKey(
	$page,
	$popts,
	$parserOutputMetadata->getUsedOptions()
	);

	$value = $this->cache->get( $parserOutputKey, BagOStuff::READ_VERIFIED );
	if ( $value === false ) {
	$this->incrementStats( $page, 'miss', 'absent' );
	$this->logger->debug( 'ParserOutput cache miss', [ 'name' => $this->name ] );
	return false;
	}

	// NOTE: If the value wasn't serialized to JSON when being stored,
	// we may already have a ParserOutput object here. This used
	// to be the default behavior before 1.36. We need to retain
	// support so we can handle cached objects after an update
	// from an earlier revision.
	// NOTE: Support for reading string values from the cache must be
	// deployed a while before starting to write JSON to the cache,
	// in case we have to revert either change.
	if ( is_string( $value ) ) {
	$value = $this->restoreFromJson( $value, $parserOutputKey, ParserOutput::class );
	}

	if ( !$value instanceof ParserOutput ) {
	$this->incrementStats( $page, 'miss', 'unserialize' );
	return false;
	}

	if ( $this->checkExpired( $value, $page, $staleConstraint, 'output' ) ) {
	return false;
	}

	if ( $this->checkOutdated( $value, $page, $staleConstraint, 'output' ) ) {
	return false;
	}

	$wikiPage = $this->wikiPageFactory->newFromTitle( $page );
	if ( $this->hookRunner->onRejectParserCacheValue( $value, $wikiPage, $popts ) === false ) {
	$this->incrementStats( $page, 'miss', 'rejected' );
	$this->logger->debug( 'key valid, but rejected by RejectParserCacheValue hook handler',
	[ 'name' => $this->name ] );
	return false;
	}

	$this->logger->debug( 'ParserOutput cache found', [ 'name' => $this->name ] );
	$this->incrementStats( $page, 'hit' );
	return $value;
	}

	/**
	* @param ParserOutput $parserOutput
	* @param PageRecord $page
	* @param ParserOptions $popts
	* @param string\|null $cacheTime TS_MW timestamp when the cache was generated
	* @param int\|null $revId Revision ID that was parsed
	*/
	public function save(
	ParserOutput $parserOutput,
	PageRecord $page,
	$popts,
	$cacheTime = null,
	$revId = null
	) {
	$page->assertWiki( PageRecord::LOCAL );

	// T350538: Eventually we'll warn if the $cacheTime and $revId
	// parameters are non-null here, since we should be getting
	// them from the ParserOutput.
	if ( $revId !== null && $revId !== $parserOutput->getCacheRevisionId() ) {
	$this->logger->warning(
	'Inconsistent revision ID',
	[
	'name' => $this->name,
	'reason' => $popts->getRenderReason(),
	'revid1' => $revId,
	'revid2' => $parserOutput->getCacheRevisionId(),
	]
	);
	}

	if ( !$parserOutput->hasText() ) {
	throw new InvalidArgumentException( 'Attempt to cache a ParserOutput with no text set!' );
	}

	$expire = $parserOutput->getCacheExpiry();

	if ( !$popts->isSafeToCache( $parserOutput->getUsedOptions() ) ) {
	$this->logger->debug(
	'Parser options are not safe to cache and has not been saved',
	[ 'name' => $this->name ]
	);
	$this->incrementStats( $page, 'save', 'unsafe' );
	return;
	}

	if ( $expire <= 0 ) {
	$this->logger->debug(
	'Parser output was marked as uncacheable and has not been saved',
	[ 'name' => $this->name ]
	);
	$this->incrementStats( $page, 'save', 'uncacheable' );
	return;
	}

	if ( $this->filter && !$this->filter->shouldCache( $parserOutput, $page, $popts ) ) {
	$this->logger->debug(
	'Parser output was filtered and has not been saved',
	[ 'name' => $this->name ]
	);
	$this->incrementStats( $page, 'save', 'filtered' );

	// TODO: In this case, we still want to cache in RevisionOutputCache (T350669).
	return;
	}

	if ( $this->cache instanceof EmptyBagOStuff ) {
	return;
	}

	// Ensure cache properties are set in the ParserOutput
	// T350538: These should be turned into assertions that the
	// properties are already present.
	if ( $cacheTime ) {
	$parserOutput->setCacheTime( $cacheTime );
	} else {
	if ( !$parserOutput->hasCacheTime() ) {
	$this->logger->warning(
	'No cache time set',
	[
	'name' => $this->name,
	'reason' => $popts->getRenderReason(),
	]
	);
	}
	$cacheTime = $parserOutput->getCacheTime();
	}

	if ( $revId ) {
	$parserOutput->setCacheRevisionId( $revId );
	} elseif ( $parserOutput->getCacheRevisionId() ) {
	$revId = $parserOutput->getCacheRevisionId();
	} else {
	$revId = $page->getLatest( PageRecord::LOCAL );
	$parserOutput->setCacheRevisionId( $revId );
	}
	if ( !$revId ) {
	$this->logger->warning(
	'Parser output cannot be saved if the revision ID is not known',
	[ 'name' => $this->name ]
	);
	$this->incrementStats( $page, 'save', 'norevid' );
	return;
	}

	if ( !$parserOutput->getRenderId() ) {
	$this->logger->warning(
	'Parser output missing render ID',
	[
	'name' => $this->name,
	'reason' => $popts->getRenderReason(),
	]
	);
	$parserOutput->setRenderId( $this->globalIdGenerator->newUUIDv1() );
	}

	// Transfer cache properties to the cache metadata
	$metadata = new CacheTime;
	$metadata->recordOptions( $parserOutput->getUsedOptions() );
	$metadata->updateCacheExpiry( $expire );
	$metadata->setCacheTime( $cacheTime );
	$metadata->setCacheRevisionId( $revId );

	$parserOutputKey = $this->makeParserOutputKey(
	$page,
	$popts,
	$metadata->getUsedOptions()
	);

	$msg = "Saved in parser cache with key $parserOutputKey" .
	" and timestamp $cacheTime" .
	" and revision id $revId.";

	$reason = $popts->getRenderReason();
	$msg .= " Rendering was triggered because: $reason";

	$parserOutput->addCacheMessage( $msg );

	$pageKey = $this->makeMetadataKey( $page );

	$parserOutputData = $this->convertForCache( $parserOutput, $parserOutputKey );
	$metadataData = $this->convertForCache( $metadata, $pageKey );

	if ( !$parserOutputData \|\| !$metadataData ) {
	$this->logger->warning(
	'Parser output failed to serialize and was not saved',
	[ 'name' => $this->name ]
	);
	$this->incrementStats( $page, 'save', 'nonserializable' );
	return;
	}

	// Save the parser output
	$this->cache->set(
	$parserOutputKey,
	$parserOutputData,
	$expire,
	BagOStuff::WRITE_ALLOW_SEGMENTS
	);

	// ...and its pointer to the local cache.
	$this->metadataProcCache->set( $pageKey, $metadataData, $expire );
	// ...and to the global cache.
	$this->cache->set( $pageKey, $metadataData, $expire );

	$title = $this->titleFactory->newFromPageIdentity( $page );
	$this->hookRunner->onParserCacheSaveComplete( $this, $parserOutput, $title, $popts, $revId );

	$this->logger->debug( 'Saved in parser cache', [
	'name' => $this->name,
	'key' => $parserOutputKey,
	'cache_time' => $cacheTime,
	'rev_id' => $revId
	] );
	$this->incrementStats( $page, 'save', 'success' );
	$this->incrementRenderReasonStats( $page, $popts->getRenderReason() );
	}

	/**
	* Get the backend BagOStuff instance that
	* powers the parser cache
	*
	* @since 1.30
	* @internal
	* @return BagOStuff
	*/
	public function getCacheStorage() {
	return $this->cache;
	}

	/**
	* Check if $entry expired for $page given the $staleConstraint
	* when fetching from $cacheTier.
	* @param CacheTime $entry
	* @param PageRecord $page
	* @param int $staleConstraint One of USE_* constants.
	* @param string $cacheTier
	* @return bool
	*/
	private function checkExpired(
	CacheTime $entry,
	PageRecord $page,
	int $staleConstraint,
	string $cacheTier
	): bool {
	if ( $staleConstraint < self::USE_EXPIRED && $entry->expired( $page->getTouched() ) ) {
	$this->incrementStats( $page, 'miss', 'expired' );
	$this->logger->debug( "{$cacheTier} key expired", [
	'name' => $this->name,
	'touched' => $page->getTouched(),
	'epoch' => $this->cacheEpoch,
	'cache_time' => $entry->getCacheTime()
	] );
	return true;
	}
	return false;
	}

	/**
	* Check if $entry belongs to the latest revision of $page
	* given $staleConstraint when fetched from $cacheTier.
	* @param CacheTime $entry
	* @param PageRecord $page
	* @param int $staleConstraint One of USE_* constants.
	* @param string $cacheTier
	* @return bool
	*/
	private function checkOutdated(
	CacheTime $entry,
	PageRecord $page,
	int $staleConstraint,
	string $cacheTier
	): bool {
	$latestRevId = $page->getLatest( PageRecord::LOCAL );
	if ( $staleConstraint < self::USE_OUTDATED && $entry->isDifferentRevision( $latestRevId ) ) {
	$this->incrementStats( $page, 'miss', 'revid' );
	$this->logger->debug( "{$cacheTier} key is for an old revision", [
	'name' => $this->name,
	'rev_id' => $latestRevId,
	'cached_rev_id' => $entry->getCacheRevisionId()
	] );
	return true;
	}
	return false;
	}

	/**
	* @param string $jsonData
	* @param string $key
	* @param string $expectedClass
	* @return CacheTime\|ParserOutput\|null
	*/
	private function restoreFromJson( string $jsonData, string $key, string $expectedClass ) {
	try {
	/** @var CacheTime $obj */
	$obj = $this->jsonCodec->deserialize( $jsonData, $expectedClass );
	return $obj;
	} catch ( JsonException $e ) {
	$this->logger->error( "Unable to deserialize JSON", [
	'name' => $this->name,
	'cache_key' => $key,
	'ex_message' => $e->getMessage()
	] );
	return null;
	} catch ( Exception $e ) {
	$this->logger->error( "Unexpected failure during cache load", [
	'name' => $this->name,
	'cache_key' => $key,
	'ex_message' => $e->getMessage()
	] );
	return null;
	}
	}

	/**
	* @param CacheTime $obj
	* @param string $key
	* @return string\|null
	*/
	protected function convertForCache( CacheTime $obj, string $key ) {
	try {
	return $this->jsonCodec->serialize( $obj );
	} catch ( JsonException $e ) {
	// Try to collect some additional debugging information, but
	// wrap this in a try block to ensure we don't make the problem
	// worse.
	try {
	$details = $this->jsonCodec->detectNonSerializableData( $obj, true );
	} catch ( \Throwable $t ) {
	$details = $t->getMessage();
	}
	$this->logger->error( "Unable to serialize JSON", [
	'name' => $this->name,
	'cache_key' => $key,
	'ex_message' => $e->getMessage(),
	'details' => $details,
	'trace' => $e->getTraceAsString(),
	] );
	return null;
	}
	}
	}

	/** @deprecated class alias since 1.43 */
	class_alias( ParserCache::class, 'ParserCache' );

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