From: Demon <chadh@wikimedia.org>
Date: Wed, 8 Aug 2012 18:15:18 +0000 (+0000)
Subject: Merge "[LockManager] Cleaned up DBLockManager and reduced code duplication."
X-Git-Tag: 1.31.0-rc.0~22798
X-Git-Url: http://git.cyclocoop.org/%27.%28%24current%20%3E%202?a=commitdiff_plain;h=4878e9593c313e0ab6d4a81a3ecea36a0afdb291;hp=-c;p=lhc%2Fweb%2Fwiklou.git

Merge "[LockManager] Cleaned up DBLockManager and reduced code duplication."
---

4878e9593c313e0ab6d4a81a3ecea36a0afdb291
diff --combined includes/filerepo/backend/lockmanager/DBLockManager.php
index f5d7b599f2,5e6aed0211..204ca3b895
--- a/includes/filerepo/backend/lockmanager/DBLockManager.php
+++ b/includes/filerepo/backend/lockmanager/DBLockManager.php
@@@ -37,11 -37,9 +37,9 @@@
   * @ingroup LockManager
   * @since 1.19
   */
- class DBLockManager extends LockManager {
+ class DBLockManager extends QuorumLockManager {
  	/** @var Array Map of DB names to server config */
  	protected $dbServers; // (DB name => server config array)
- 	/** @var Array Map of bucket indexes to peer DB lists */
- 	protected $dbsByBucket; // (bucket index => (ldb1, ldb2, ...))
  	/** @var BagOStuff */
  	protected $statusCache;
  
@@@ -54,7 -52,7 +52,7 @@@
  
  	/**
  	 * Construct a new instance from configuration.
- 	 * 
+ 	 *
  	 * $config paramaters include:
  	 *     'dbServers'   : Associative array of DB names to server configuration.
  	 *                     Configuration is an associative array that includes:
@@@ -73,7 -71,7 +71,7 @@@
  	 *                     This tells the DB server how long to wait before assuming
  	 *                     connection failure and releasing all the locks for a session.
  	 *
- 	 * @param Array $config 
+ 	 * @param Array $config
  	 */
  	public function __construct( array $config ) {
  		parent::__construct( $config );
@@@ -81,9 -79,9 +79,9 @@@
  		$this->dbServers = isset( $config['dbServers'] )
  			? $config['dbServers']
  			: array(); // likely just using 'localDBMaster'
- 		// Sanitize dbsByBucket config to prevent PHP errors
- 		$this->dbsByBucket = array_filter( $config['dbsByBucket'], 'is_array' );
- 		$this->dbsByBucket = array_values( $this->dbsByBucket ); // consecutive
+ 		// Sanitize srvsByBucket config to prevent PHP errors
+ 		$this->srvsByBucket = array_filter( $config['dbsByBucket'], 'is_array' );
+ 		$this->srvsByBucket = array_values( $this->srvsByBucket ); // consecutive
  
  		if ( isset( $config['lockExpiry'] ) ) {
  			$this->lockExpiry = $config['lockExpiry'];
@@@ -95,179 -93,97 +93,97 @@@
  			? 60 // pick a safe-ish number to match DB timeout default
  			: $this->lockExpiry; // cover worst case
  
- 		foreach ( $this->dbsByBucket as $bucket ) {
- 			if ( count( $bucket ) > 1 ) {
+ 		foreach ( $this->srvsByBucket as $bucket ) {
+ 			if ( count( $bucket ) > 1 ) { // multiple peers
  				// Tracks peers that couldn't be queried recently to avoid lengthy
  				// connection timeouts. This is useless if each bucket has one peer.
- 				$this->statusCache = wfGetMainCache();
+ 				try {
+ 					$this->statusCache = ObjectCache::newAccelerator( array() );
+ 				} catch ( MWException $e ) {
+ 					trigger_error( __CLASS__ .
+ 						" using multiple DB peers without apc, xcache, or wincache." );
+ 				}
  				break;
  			}
  		}
  
- 		$this->session = '';
- 		for ( $i = 0; $i < 5; $i++ ) {
- 			$this->session .= mt_rand( 0, 2147483647 );
- 		}
- 		$this->session = wfBaseConvert( sha1( $this->session ), 16, 36, 31 );
+ 		$this->session = wfRandomString( 31 );
  	}
  
  	/**
- 	 * @see LockManager::doLock()
- 	 * @param $paths array
- 	 * @param $type int
+ 	 * Get a connection to a lock DB and acquire locks on $paths.
+ 	 * This does not use GET_LOCK() per http://bugs.mysql.com/bug.php?id=1118.
+ 	 *
+ 	 * @see QuorumLockManager::getLocksOnServer()
  	 * @return Status
  	 */
- 	protected function doLock( array $paths, $type ) {
+ 	protected function getLocksOnServer( $lockSrv, array $paths, $type ) {
  		$status = Status::newGood();
  
- 		$pathsToLock = array();
- 		// Get locks that need to be acquired (buckets => locks)...
- 		foreach ( $paths as $path ) {
- 			if ( isset( $this->locksHeld[$path][$type] ) ) {
- 				++$this->locksHeld[$path][$type];
- 			} elseif ( isset( $this->locksHeld[$path][self::LOCK_EX] ) ) {
- 				$this->locksHeld[$path][$type] = 1;
- 			} else {
- 				$bucket = $this->getBucketFromKey( $path );
- 				$pathsToLock[$bucket][] = $path;
- 			}
- 		}
- 
- 		$lockedPaths = array(); // files locked in this attempt
- 		// Attempt to acquire these locks...
- 		foreach ( $pathsToLock as $bucket => $paths ) {
- 			// Try to acquire the locks for this bucket
- 			$res = $this->doLockingQueryAll( $bucket, $paths, $type );
- 			if ( $res === 'cantacquire' ) {
- 				// Resources already locked by another process.
- 				// Abort and unlock everything we just locked.
+ 		if ( $type == self::LOCK_EX ) { // writer locks
+ 			try {
+ 				$keys = array_unique( array_map( 'LockManager::sha1Base36', $paths ) );
+ 				# Build up values for INSERT clause
+ 				$data = array();
+ 				foreach ( $keys as $key ) {
+ 					$data[] = array( 'fle_key' => $key );
+ 				}
+ 				# Wait on any existing writers and block new ones if we get in
+ 				$db = $this->getConnection( $lockSrv ); // checked in isServerUp()
+ 				$db->insert( 'filelocks_exclusive', $data, __METHOD__ );
+ 			} catch ( DBError $e ) {
  				foreach ( $paths as $path ) {
  					$status->fatal( 'lockmanager-fail-acquirelock', $path );
  				}
- 				$status->merge( $this->doUnlock( $lockedPaths, $type ) );
- 				return $status;
- 			} elseif ( $res !== true ) {
- 				// Couldn't contact any DBs for this bucket.
- 				// Abort and unlock everything we just locked.
- 				$status->fatal( 'lockmanager-fail-db-bucket', $bucket );
- 				$status->merge( $this->doUnlock( $lockedPaths, $type ) );
- 				return $status;
  			}
- 			// Record these locks as active
- 			foreach ( $paths as $path ) {
- 				$this->locksHeld[$path][$type] = 1; // locked
- 			}
- 			// Keep track of what locks were made in this attempt
- 			$lockedPaths = array_merge( $lockedPaths, $paths );
  		}
  
  		return $status;
  	}
  
  	/**
- 	 * @see LockManager::doUnlock()
- 	 * @param $paths array
- 	 * @param $type int
+ 	 * @see QuorumLockManager::freeLocksOnServer()
  	 * @return Status
  	 */
- 	protected function doUnlock( array $paths, $type ) {
+ 	protected function freeLocksOnServer( $lockSrv, array $paths, $type ) {
+ 		return Status::newGood(); // not supported
+ 	}
+ 
+ 	/**
+ 	 * @see QuorumLockManager::releaseAllLocks()
+ 	 * @return Status
+ 	 */
+ 	protected function releaseAllLocks() {
  		$status = Status::newGood();
  
- 		foreach ( $paths as $path ) {
- 			if ( !isset( $this->locksHeld[$path] ) ) {
- 				$status->warning( 'lockmanager-notlocked', $path );
- 			} elseif ( !isset( $this->locksHeld[$path][$type] ) ) {
- 				$status->warning( 'lockmanager-notlocked', $path );
- 			} else {
- 				--$this->locksHeld[$path][$type];
- 				if ( $this->locksHeld[$path][$type] <= 0 ) {
- 					unset( $this->locksHeld[$path][$type] );
- 				}
- 				if ( !count( $this->locksHeld[$path] ) ) {
- 					unset( $this->locksHeld[$path] ); // no SH or EX locks left for key
+ 		foreach ( $this->conns as $lockDb => $db ) {
+ 			if ( $db->trxLevel() ) { // in transaction
+ 				try {
+ 					$db->rollback( __METHOD__ ); // finish transaction and kill any rows
+ 				} catch ( DBError $e ) {
+ 					$status->fatal( 'lockmanager-fail-db-release', $lockDb );
  				}
  			}
  		}
  
- 		// Reference count the locks held and COMMIT when zero
- 		if ( !count( $this->locksHeld ) ) {
- 			$status->merge( $this->finishLockTransactions() );
- 		}
- 
  		return $status;
  	}
  
  	/**
- 	 * Get a connection to a lock DB and acquire locks on $paths.
- 	 * This does not use GET_LOCK() per http://bugs.mysql.com/bug.php?id=1118.
- 	 *
- 	 * @param $lockDb string
- 	 * @param $paths Array
- 	 * @param $type integer LockManager::LOCK_EX or LockManager::LOCK_SH
- 	 * @return bool Resources able to be locked
- 	 * @throws DBError
+ 	 * @see QuorumLockManager::isServerUp()
+ 	 * @return bool
  	 */
- 	protected function doLockingQuery( $lockDb, array $paths, $type ) {
- 		if ( $type == self::LOCK_EX ) { // writer locks
- 			$db = $this->getConnection( $lockDb );
- 			if ( !$db ) {
- 				return false; // bad config
- 			}
- 			$keys = array_unique( array_map( 'LockManager::sha1Base36', $paths ) );
- 			# Build up values for INSERT clause
- 			$data = array();
- 			foreach ( $keys as $key ) {
- 				$data[] = array( 'fle_key' => $key );
- 			}
- 			# Wait on any existing writers and block new ones if we get in
- 			$db->insert( 'filelocks_exclusive', $data, __METHOD__ );
+ 	protected function isServerUp( $lockSrv ) {
+ 		if ( !$this->cacheCheckFailures( $lockSrv ) ) {
+ 			return false; // recent failure to connect
  		}
- 		return true;
- 	}
- 
- 	/**
- 	 * Attempt to acquire locks with the peers for a bucket.
- 	 * This should avoid throwing any exceptions.
- 	 *
- 	 * @param $bucket integer
- 	 * @param $paths Array List of resource keys to lock
- 	 * @param $type integer LockManager::LOCK_EX or LockManager::LOCK_SH
- 	 * @return bool|string One of (true, 'cantacquire', 'dberrors')
- 	 */
- 	protected function doLockingQueryAll( $bucket, array $paths, $type ) {
- 		$yesVotes = 0; // locks made on trustable DBs
- 		$votesLeft = count( $this->dbsByBucket[$bucket] ); // remaining DBs
- 		$quorum = floor( $votesLeft/2 + 1 ); // simple majority
- 		// Get votes for each DB, in order, until we have enough...
- 		foreach ( $this->dbsByBucket[$bucket] as $lockDb ) {
- 			// Check that DB is not *known* to be down
- 			if ( $this->cacheCheckFailures( $lockDb ) ) {
- 				try {
- 					// Attempt to acquire the lock on this DB
- 					if ( !$this->doLockingQuery( $lockDb, $paths, $type ) ) {
- 						return 'cantacquire'; // vetoed; resource locked
- 					}
- 					++$yesVotes; // success for this peer
- 					if ( $yesVotes >= $quorum ) {
- 						return true; // lock obtained
- 					}
- 				} catch ( DBConnectionError $e ) {
- 					$this->cacheRecordFailure( $lockDb );
- 				} catch ( DBError $e ) {
- 					if ( $this->lastErrorIndicatesLocked( $lockDb ) ) {
- 						return 'cantacquire'; // vetoed; resource locked
- 					}
- 				}
- 			}
- 			--$votesLeft;
- 			$votesNeeded = $quorum - $yesVotes;
- 			if ( $votesNeeded > $votesLeft ) {
- 				// In "trust cache" mode we don't have to meet the quorum
- 				break; // short-circuit
- 			}
+ 		try {
+ 			$this->getConnection( $lockSrv );
+ 		} catch ( DBError $e ) {
+ 			$this->cacheRecordFailure( $lockSrv );
+ 			return false; // failed to connect
  		}
- 		// At this point, we must not have meet the quorum
- 		return 'dberrors'; // not enough votes to ensure correctness
+ 		return true;
  	}
  
  	/**
@@@ -318,56 -234,17 +234,17 @@@
  	 */
  	protected function initConnection( $lockDb, DatabaseBase $db ) {}
  
- 	/**
- 	 * Commit all changes to lock-active databases.
- 	 * This should avoid throwing any exceptions.
- 	 *
- 	 * @return Status
- 	 */
- 	protected function finishLockTransactions() {
- 		$status = Status::newGood();
- 		foreach ( $this->conns as $lockDb => $db ) {
- 			if ( $db->trxLevel() ) { // in transaction
- 				try {
- 					$db->rollback( __METHOD__ ); // finish transaction and kill any rows
- 				} catch ( DBError $e ) {
- 					$status->fatal( 'lockmanager-fail-db-release', $lockDb );
- 				}
- 			}
- 		}
- 		return $status;
- 	}
- 
- 	/**
- 	 * Check if the last DB error for $lockDb indicates
- 	 * that a requested resource was locked by another process.
- 	 * This should avoid throwing any exceptions.
- 	 * 
- 	 * @param $lockDb string
- 	 * @return bool
- 	 */
- 	protected function lastErrorIndicatesLocked( $lockDb ) {
- 		if ( isset( $this->conns[$lockDb] ) ) { // sanity
- 			$db = $this->conns[$lockDb];
- 			return ( $db->wasDeadlock() || $db->wasLockTimeout() );
- 		}
- 		return false;
- 	}
- 
  	/**
  	 * Checks if the DB has not recently had connection/query errors.
  	 * This just avoids wasting time on doomed connection attempts.
- 	 * 
+ 	 *
  	 * @param $lockDb string
  	 * @return bool
  	 */
  	protected function cacheCheckFailures( $lockDb ) {
- 		if ( $this->statusCache && $this->safeDelay > 0 ) {
- 			$path = $this->getMissKey( $lockDb );
- 			$misses = $this->statusCache->get( $path );
- 			return !$misses;
- 		}
- 		return true;
+ 		return ( $this->statusCache && $this->safeDelay > 0 )
+ 			? !$this->statusCache->get( $this->getMissKey( $lockDb ) )
+ 			: true;
  	}
  
  	/**
@@@ -377,16 -254,9 +254,9 @@@
  	 * @return bool Success
  	 */
  	protected function cacheRecordFailure( $lockDb ) {
- 		if ( $this->statusCache && $this->safeDelay > 0 ) {
- 			$path = $this->getMissKey( $lockDb );
- 			$misses = $this->statusCache->get( $path );
- 			if ( $misses ) {
- 				return $this->statusCache->incr( $path );
- 			} else {
- 				return $this->statusCache->add( $path, 1, $this->safeDelay );
- 			}
- 		}
- 		return true;
+ 		return ( $this->statusCache && $this->safeDelay > 0 )
+ 			? $this->statusCache->set( $this->getMissKey( $lockDb ), 1, $this->safeDelay )
+ 			: true;
  	}
  
  	/**
@@@ -396,26 -266,15 +266,15 @@@
  	 * @return string
  	 */
  	protected function getMissKey( $lockDb ) {
- 		return 'lockmanager:querymisses:' . str_replace( ' ', '_', $lockDb );
- 	}
- 
- 	/**
- 	 * Get the bucket for resource path.
- 	 * This should avoid throwing any exceptions.
- 	 *
- 	 * @param $path string
- 	 * @return integer
- 	 */
- 	protected function getBucketFromKey( $path ) {
- 		$prefix = substr( sha1( $path ), 0, 2 ); // first 2 hex chars (8 bits)
- 		return intval( base_convert( $prefix, 16, 10 ) ) % count( $this->dbsByBucket );
+ 		$lockDb = ( $lockDb === 'localDBMaster' ) ? wfWikiID() : $lockDb; // non-relative
+ 		return 'dblockmanager:downservers:' . str_replace( ' ', '_', $lockDb );
  	}
  
  	/**
  	 * Make sure remaining locks get cleared for sanity
  	 */
  	function __destruct() {
 -		foreach ( $this->conns as $lockDb => $db ) {
 +		foreach ( $this->conns as $db ) {
  			if ( $db->trxLevel() ) { // in transaction
  				try {
  					$db->rollback( __METHOD__ ); // finish transaction and kill any rows
@@@ -452,16 -311,16 +311,16 @@@ class MySqlLockManager extends DBLockMa
  	}
  
  	/**
- 	 * @param $lockDb string
- 	 * @param $paths array
- 	 * @param $type int
- 	 * @return bool
+ 	 * Get a connection to a lock DB and acquire locks on $paths.
+ 	 * This does not use GET_LOCK() per http://bugs.mysql.com/bug.php?id=1118.
+ 	 *
+ 	 * @see DBLockManager::getLocksOnServer()
+ 	 * @return Status
  	 */
- 	protected function doLockingQuery( $lockDb, array $paths, $type ) {
- 		$db = $this->getConnection( $lockDb );
- 		if ( !$db ) {
- 			return false;
- 		}
+ 	protected function getLocksOnServer( $lockSrv, array $paths, $type ) {
+ 		$status = Status::newGood();
+ 
+ 		$db = $this->getConnection( $lockSrv ); // checked in isServerUp()
  		$keys = array_unique( array_map( 'LockManager::sha1Base36', $paths ) );
  		# Build up values for INSERT clause
  		$data = array();
@@@ -503,6 -362,13 +362,13 @@@
  				);
  			}
  		}
- 		return !$blocked;
+ 
+ 		if ( $blocked ) {
+ 			foreach ( $paths as $path ) {
+ 				$status->fatal( 'lockmanager-fail-acquirelock', $path );
+ 			}
+ 		}
+ 
+ 		return $status;
  	}
  }