messagecache.php

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<?php
/**
 *
 * @package MediaWiki
 * @subpackage Cache
 */

/**
 *
 */
define( 'MSG_LOAD_TIMEOUT', 60);
define( 'MSG_LOCK_TIMEOUT', 10);
define( 'MSG_WAIT_TIMEOUT', 10);

/**
 * Message cache
 * Performs various useful MediaWiki namespace-related functions
 *
 * @package MediaWiki
 */
class MessageCache {
	var $mCache, $mUseCache, $mDisable, $mExpiry;
	var $mMemcKey, $mKeys, $mParserOptions, $mParser;
	var $mExtensionMessages = array();
	var $mInitialised = false;
	var $mDeferred = true;

	function __construct( &$memCached, $useDB, $expiry, $memcPrefix) {
		wfProfileIn( __METHOD__ );

		$this->mUseCache = !is_null( $memCached );
		$this->mMemc = &$memCached;
		$this->mDisable = !$useDB;
		$this->mExpiry = $expiry;
		$this->mDisableTransform = false;
		$this->mMemcKey = $memcPrefix.':messages';
		$this->mKeys = false; # initialised on demand
		$this->mInitialised = true;

		wfProfileIn( __METHOD__.'-parseropt' );
		$this->mParserOptions = new ParserOptions( $u=NULL );
		wfProfileOut( __METHOD__.'-parseropt' );
		$this->mParser = null;

		# When we first get asked for a message,
		# then we'll fill up the cache. If we
		# can return a cache hit, this saves
		# some extra milliseconds
		$this->mDeferred = true;

		wfProfileOut( __METHOD__ );
	}

	/**
	 * Try to load the cache from a local file
	 */
	function loadFromLocal( $hash ) {
		global $wgLocalMessageCache, $wgDBname;

		$this->mCache = false;
		if ( $wgLocalMessageCache === false ) {
			return;
		}

		$filename = "$wgLocalMessageCache/messages-$wgDBname";

		wfSuppressWarnings();
		$file = fopen( $filename, 'r' );
		wfRestoreWarnings();
		if ( !$file ) {
			return;
		}

		// Check to see if the file has the hash specified
		$localHash = fread( $file, 32 );
		if ( $hash == $localHash ) {
			// All good, get the rest of it
			$serialized = fread( $file, 1000000 );
			$this->mCache = unserialize( $serialized );
		}
		fclose( $file );
	}

	/**
	 * Save the cache to a local file
	 */
	function saveToLocal( $serialized, $hash ) {
		global $wgLocalMessageCache, $wgDBname;

		if ( $wgLocalMessageCache === false ) {
			return;
		}

		$filename = "$wgLocalMessageCache/messages-$wgDBname";
		$oldUmask = umask( 0 );
		wfMkdirParents( $wgLocalMessageCache, 0777 );
		umask( $oldUmask );

		$file = fopen( $filename, 'w' );
		if ( !$file ) {
			wfDebug( "Unable to open local cache file for writing\n" );
			return;
		}

		fwrite( $file, $hash . $serialized );
		fclose( $file );
		@chmod( $filename, 0666 );
	}

	function loadFromScript( $hash ) {
		global $wgLocalMessageCache, $wgDBname;
		if ( $wgLocalMessageCache === false ) {
			return;
		}
		
		$filename = "$wgLocalMessageCache/messages-$wgDBname";
		
		wfSuppressWarnings();
		$file = fopen( $filename, 'r' );
		wfRestoreWarnings();
		if ( !$file ) {
			return;
		}
		$localHash=substr(fread($file,40),8);
		fclose($file);
		if ($hash!=$localHash) {
			return;
		}
		require("$wgLocalMessageCache/messages-$wgDBname");
	}
	
	function saveToScript($array, $hash) {
		global $wgLocalMessageCache, $wgDBname;
		if ( $wgLocalMessageCache === false ) {
			return;
		}

		$filename = "$wgLocalMessageCache/messages-$wgDBname";
		$oldUmask = umask( 0 );
		wfMkdirParents( $wgLocalMessageCache, 0777 );
		umask( $oldUmask );
		$file = fopen( $filename.'.tmp', 'w');
		fwrite($file,"<?php\n//$hash\n\n \$this->mCache = array(");
		
		foreach ($array as $key => $message) {
			fwrite($file, "'". $this->escapeForScript($key).
				"' => '" . $this->escapeForScript($message). 
				"',\n");
		}
		fwrite($file,");\n?>");
		fclose($file);
		rename($filename.'.tmp',$filename);
	}

	function escapeForScript($string) {
		$string = str_replace( '\\', '\\\\', $string );
		$string = str_replace( '\'', '\\\'', $string );
		return $string;
	}

	/**
	 * Loads messages either from memcached or the database, if not disabled
	 * On error, quietly switches to a fallback mode
	 * Returns false for a reportable error, true otherwise
	 */
	function load() {
		global $wgLocalMessageCache, $wgLocalMessageCacheSerialized;

		if ( $this->mDisable ) {
			static $shownDisabled = false;
			if ( !$shownDisabled ) {
				wfDebug( "MessageCache::load(): disabled\n" );
				$shownDisabled = true;
			}
			return true;
		}
		$fname = 'MessageCache::load';
		wfProfileIn( $fname );
		$success = true;

		if ( $this->mUseCache ) {
			$this->mCache = false;

			# Try local cache
			wfProfileIn( $fname.'-fromlocal' );
			$hash = $this->mMemc->get( "{$this->mMemcKey}-hash" );
			if ( $hash ) {
				if ($wgLocalMessageCacheSerialized) {
					$this->loadFromLocal( $hash );
				} else {
					$this->loadFromScript( $hash );
				}
			}
			wfProfileOut( $fname.'-fromlocal' );

			# Try memcached
			if ( !$this->mCache ) {
				wfProfileIn( $fname.'-fromcache' );
				$this->mCache = $this->mMemc->get( $this->mMemcKey );

				# Save to local cache
				if ( $wgLocalMessageCache !== false ) {
					$serialized = serialize( $this->mCache );
					if ( !$hash ) {
						$hash = md5( $serialized );
						$this->mMemc->set( "{$this->mMemcKey}-hash", $hash, $this->mExpiry );
					}
					if ($wgLocalMessageCacheSerialized) {
						$this->saveToLocal( $serialized,$hash );
					} else {
						$this->saveToScript( $this->mCache, $hash );
					}
				}
				wfProfileOut( $fname.'-fromcache' );
			}


			# If there's nothing in memcached, load all the messages from the database
			if ( !$this->mCache ) {
				wfDebug( "MessageCache::load(): loading all messages\n" );
				$this->lock();
				# Other threads don't need to load the messages if another thread is doing it.
				$success = $this->mMemc->add( $this->mMemcKey.'-status', "loading", MSG_LOAD_TIMEOUT );
				if ( $success ) {
					wfProfileIn( $fname.'-load' );
					$this->loadFromDB();
					wfProfileOut( $fname.'-load' );

					# Save in memcached
					# Keep trying if it fails, this is kind of important
					wfProfileIn( $fname.'-save' );
					for ($i=0; $i<20 &&
					           !$this->mMemc->set( $this->mMemcKey, $this->mCache, $this->mExpiry );
					     $i++ ) {
						usleep(mt_rand(500000,1500000));
					}

					# Save to local cache
					if ( $wgLocalMessageCache !== false ) {
						$serialized = serialize( $this->mCache );
						$hash = md5( $serialized );
						$this->mMemc->set( "{$this->mMemcKey}-hash", $hash, $this->mExpiry );
						if ($wgLocalMessageCacheSerialized) {
							$this->saveToLocal( $serialized,$hash );
						} else {
							$this->saveToScript( $this->mCache, $hash );
						}
					}

					wfProfileOut( $fname.'-save' );
					if ( $i == 20 ) {
						$this->mMemc->set( $this->mMemcKey.'-status', 'error', 60*5 );
						wfDebug( "MemCached set error in MessageCache: restart memcached server!\n" );
					}
				}
				$this->unlock();
			}

			if ( !is_array( $this->mCache ) ) {
				wfDebug( "MessageCache::load(): individual message mode\n" );
				# If it is 'loading' or 'error', switch to individual message mode, otherwise disable
				# Causing too much DB load, disabling -- TS
				$this->mDisable = true;
				/*
				if ( $this->mCache == "loading" ) {
					$this->mUseCache = false;
				} elseif ( $this->mCache == "error" ) {
					$this->mUseCache = false;
					$success = false;
				} else {
					$this->mDisable = true;
					$success = false;
				}*/
				$this->mCache = false;
			}
		}
		wfProfileOut( $fname );
		$this->mDeferred = false;
		return $success;
	}

	/**
	 * Loads all or main part of cacheable messages from the database
	 */
	function loadFromDB() {
		global $wgAllMessagesEn, $wgLang;

		$fname = 'MessageCache::loadFromDB';
		$dbr =& wfGetDB( DB_SLAVE );
		if ( !$dbr ) {
			throw new MWException( 'Invalid database object' );