MessageBlobStore.php
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MessageBlobStore.php
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	<?php
	/**
	* @license GPL-2.0-or-later
	* @file
	* @author Roan Kattouw
	* @author Trevor Parscal
	*/

	namespace MediaWiki\ResourceLoader;

	use MediaWiki\Json\FormatJson;
	use MediaWiki\MediaWikiServices;
	use Psr\Log\LoggerAwareInterface;
	use Psr\Log\LoggerInterface;
	use Psr\Log\NullLogger;
	use Wikimedia\ObjectCache\WANObjectCache;
	use Wikimedia\Rdbms\Database;

	/**
	* This class generates message blobs for use by ResourceLoader.
	*
	* A message blob is a JSON object containing the interface messages for a
	* certain module in a certain language.
	*
	* @ingroup ResourceLoader
	* @since 1.17
	*/
	class MessageBlobStore implements LoggerAwareInterface {
	/** @var ResourceLoader */
	private $resourceloader;

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

	/** @var WANObjectCache */
	protected $wanCache;

	/**
	* @param ResourceLoader $rl
	* @param LoggerInterface\|null $logger
	* @param WANObjectCache\|null $wanObjectCache
	*/
	public function __construct(
	ResourceLoader $rl,
	?LoggerInterface $logger,
	?WANObjectCache $wanObjectCache
	) {
	$this->resourceloader = $rl;
	$this->logger = $logger ?: new NullLogger();

	// NOTE: when changing this assignment, make sure the code in the instantiator for
	// LocalisationCache which calls MessageBlobStore::clearGlobalCacheEntry() uses the
	// same cache object.
	$this->wanCache = $wanObjectCache ?: MediaWikiServices::getInstance()
	->getMainWANObjectCache();
	}

	/**
	* @since 1.27
	* @param LoggerInterface $logger
	*/
	public function setLogger( LoggerInterface $logger ): void {
	$this->logger = $logger;
	}

	/**
	* Get the message blob for a module
	*
	* @since 1.27
	* @param Module $module
	* @param string $lang Language code
	* @return string JSON
	*/
	public function getBlob( Module $module, $lang ) {
	$blobs = $this->getBlobs( [ $module->getName() => $module ], $lang );
	return $blobs[$module->getName()];
	}

	/**
	* Get the message blobs for a set of modules
	*
	* @since 1.27
	* @param Module[] $modules Array of module objects keyed by name
	* @param string $lang Language code
	* @return string[] An array mapping module names to message blobs
	*/
	public function getBlobs( array $modules, $lang ) {
	// Each cache key for a message blob by module name and language code also has a generic
	// check key without language code. This is used to invalidate any and all language subkeys
	// that exist for a module from the updateMessage() method.
	$checkKeys = [
	self::makeGlobalPurgeKey( $this->wanCache )
	];
	$cacheKeys = [];
	foreach ( $modules as $name => $module ) {
	$cacheKey = $this->makeBlobCacheKey( $name, $lang, $module );
	$cacheKeys[$name] = $cacheKey;
	$checkKeys[$cacheKey][] = $this->makeModulePurgeKey( $name );
	}
	$curTTLs = [];
	$result = $this->wanCache->getMulti( array_values( $cacheKeys ), $curTTLs, $checkKeys );

	$blobs = [];
	foreach ( $modules as $name => $module ) {
	$key = $cacheKeys[$name];
	if ( !isset( $result[$key] ) \|\| $curTTLs[$key] === null \|\| $curTTLs[$key] < 0 ) {
	$blobs[$name] = $this->recacheMessageBlob( $key, $module, $lang );
	} else {
	// Use unexpired cache
	$blobs[$name] = $result[$key];
	}
	}
	return $blobs;
	}

	/**
	* @param WANObjectCache $cache
	* @return string Cache key
	*/
	private static function makeGlobalPurgeKey( WANObjectCache $cache ) {
	return $cache->makeGlobalKey( 'resourceloader-messageblob' );
	}

	/**
	* Per-module check key, for ::updateMessage()
	*
	* @param string $name
	* @return string Cache key
	*/
	private function makeModulePurgeKey( $name ) {
	return $this->wanCache->makeKey( 'resourceloader-messageblob', $name );
	}

	/**
	* @param string $name
	* @param string $lang
	* @param Module $module
	* @return string Cache key
	*/
	private function makeBlobCacheKey( $name, $lang, Module $module ) {
	$messages = array_values( array_unique( $module->getMessages() ) );
	sort( $messages );
	return $this->wanCache->makeKey( 'resourceloader-messageblob',
	$name,
	$lang,
	md5( json_encode( $messages ) )
	);
	}

	/**
	* @since 1.27
	* @param string $cacheKey
	* @param Module $module
	* @param string $lang
	* @return string JSON blob
	*/
	protected function recacheMessageBlob( $cacheKey, Module $module, $lang ) {
	$blob = $this->generateMessageBlob( $module, $lang );
	$cache = $this->wanCache;
	$dbr = MediaWikiServices::getInstance()->getConnectionProvider()->getReplicaDatabase();
	$cache->set( $cacheKey, $blob,
	// Add part of a day to TTL to avoid all modules expiring at once
	$cache::TTL_WEEK + mt_rand( 0, $cache::TTL_DAY ),
	Database::getCacheSetOptions( $dbr )
	);
	return $blob;
	}

	/**
	* Invalidate cache keys for modules using this message key.
	* Called by MessageCache when a message has changed.
	*
	* @param string $key Message key
	*/
	public function updateMessage( $key ): void {
	$moduleNames = $this->resourceloader->getModulesByMessage( $key );
	foreach ( $moduleNames as $moduleName ) {
	// Use the default holdoff TTL to account for database replica DB lag
	// which can affect MessageCache.
	$this->wanCache->touchCheckKey( $this->makeModulePurgeKey( $moduleName ) );
	}
	}

	/**
	* Invalidate cache keys for all known modules.
	*
	* Used by LocalisationCache, DatabaseUpdater and purgeMessageBlobStore.php script
	* after regenerating l10n cache.
	*/
	public static function clearGlobalCacheEntry( WANObjectCache $cache ) {
	// Disable holdoff TTL because:
	// - LocalisationCache is populated by messages on-disk and don't have DB lag,
	// thus there is no need for hold off. We only clear it after new localisation
	// updates are known to be deployed to all servers.
	// - This global check key invalidates message blobs for all modules for all wikis
	// in cache contexts (e.g. languages, skins). Setting a hold-off on this key could
	// cause a cache stampede since no values would be stored for several seconds.
	$cache->touchCheckKey( self::makeGlobalPurgeKey( $cache ), $cache::HOLDOFF_TTL_NONE );
	}

	/**
	* @since 1.27
	* @param string $key Message key
	* @param string $lang Language code
	* @return string\|null
	*/
	protected function fetchMessage( $key, $lang ) {
	$message = wfMessage( $key )->inLanguage( $lang );
	if ( !$message->exists() ) {
	$this->logger->warning( 'Failed to find {messageKey} ({lang})', [
	'messageKey' => $key,
	'lang' => $lang,
	] );
	$value = null;
	} else {
	$value = $message->plain();
	}
	return $value;
	}

	/**
	* Generate the message blob for a given module in a given language.
	*
	* @param Module $module
	* @param string $lang Language code
	* @return string JSON blob
	*/
	private function generateMessageBlob( Module $module, $lang ) {
	$messages = [];
	foreach ( $module->getMessages() as $key ) {
	$value = $this->fetchMessage( $key, $lang );
	// If the message does not exist, omit it from the blob so that
	// client-side mw.message may do its own existence handling.
	if ( $value !== null ) {
	$messages[$key] = $value;
	}
	}

	$json = FormatJson::encode( (object)$messages, false, FormatJson::UTF8_OK );
	// @codeCoverageIgnoreStart
	if ( $json === false ) {
	$this->logger->warning( 'Failed to encode message blob for {module} ({lang})', [
	'module' => $module->getName(),
	'lang' => $lang,
	] );
	$json = '{}';
	}
	// codeCoverageIgnoreEnd
	return $json;
	}
	}

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