Update to MediaWiki 1.19.0

1 files changed, 469 insertions, 0 deletions

diff --git a/includes/filerepo/backend/lockmanager/DBLockManager.php b/includes/filerepo/backend/lockmanager/DBLockManager.php
new file mode 100644
index 00000000..045056ea
--- /dev/null
+++ b/includes/filerepo/backend/lockmanager/DBLockManager.php
@@ -0,0 +1,469 @@
+<?php
+
+/**
+ * Version of LockManager based on using DB table locks.
+ * This is meant for multi-wiki systems that may share files.
+ * All locks are blocking, so it might be useful to set a small
+ * lock-wait timeout via server config to curtail deadlocks.
+ *
+ * All lock requests for a resource, identified by a hash string, will map
+ * to one bucket. Each bucket maps to one or several peer DBs, each on their
+ * own server, all having the filelocks.sql tables (with row-level locking).
+ * A majority of peer DBs must agree for a lock to be acquired.
+ *
+ * Caching is used to avoid hitting servers that are down.
+ *
+ * @ingroup LockManager
+ * @since 1.19
+ */
+class DBLockManager extends LockManager {
+	/** @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;
+
+	protected $lockExpiry; // integer number of seconds
+	protected $safeDelay; // integer number of seconds
+
+	protected $session = 0; // random integer
+	/** @var Array Map Database connections (DB name => Database) */
+	protected $conns = array();
+
+	/**
+	 * 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:
+	 *                     'host'        - DB server name
+	 *                     'dbname'      - DB name
+	 *                     'type'        - DB type (mysql,postgres,...)
+	 *                     'user'        - DB user
+	 *                     'password'    - DB user password
+	 *                     'tablePrefix' - DB table prefix
+	 *                     'flags'       - DB flags (see DatabaseBase)
+	 *     'dbsByBucket' : Array of 1-16 consecutive integer keys, starting from 0,
+	 *                     each having an odd-numbered list of DB names (peers) as values.
+	 *                     Any DB named 'localDBMaster' will automatically use the DB master
+	 *                     settings for this wiki (without the need for a dbServers entry).
+	 *     'lockExpiry'  : Lock timeout (seconds) for dropped connections. [optional]
+	 *                     This tells the DB server how long to wait before assuming
+	 *                     connection failure and releasing all the locks for a session.
+	 *
+	 * @param Array $config 
+	 */
+	public function __construct( array $config ) {
+		$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
+
+		if ( isset( $config['lockExpiry'] ) ) {
+			$this->lockExpiry = $config['lockExpiry'];
+		} else {
+			$met = ini_get( 'max_execution_time' );
+			$this->lockExpiry = $met ? $met : 60; // use some sane amount if 0
+		}
+		$this->safeDelay = ( $this->lockExpiry <= 0 )
+			? 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 ) {
+				// 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();
+				break;
+			}
+		}
+
+		$this->session = '';
+		for ( $i = 0; $i < 5; $i++ ) {
+			$this->session .= mt_rand( 0, 2147483647 );
+		}
+		$this->session = wfBaseConvert( sha1( $this->session ), 16, 36, 31 );
+	}
+
+	/**
+	 * @see LockManager::doLock()
+	 */
+	protected function doLock( 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.
+				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()
+	 */
+	protected function doUnlock( array $paths, $type ) {
+		$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
+				}
+			}
+		}
+
+		// 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
+	 */
+	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__ );
+		}
+		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
+			}
+		}
+		// At this point, we must not have meet the quorum
+		return 'dberrors'; // not enough votes to ensure correctness
+	}
+
+	/**
+	 * Get (or reuse) a connection to a lock DB
+	 *
+	 * @param $lockDb string
+	 * @return Database
+	 * @throws DBError
+	 */
+	protected function getConnection( $lockDb ) {
+		if ( !isset( $this->conns[$lockDb] ) ) {
+			$db = null;
+			if ( $lockDb === 'localDBMaster' ) {
+				$lb = wfGetLBFactory()->newMainLB();
+				$db = $lb->getConnection( DB_MASTER );
+			} elseif ( isset( $this->dbServers[$lockDb] ) ) {
+				$config = $this->dbServers[$lockDb];
+				$db = DatabaseBase::factory( $config['type'], $config );
+			}
+			if ( !$db ) {
+				return null; // config error?
+			}
+			$this->conns[$lockDb] = $db;
+			$this->conns[$lockDb]->clearFlag( DBO_TRX );
+			# If the connection drops, try to avoid letting the DB rollback
+			# and release the locks before the file operations are finished.
+			# This won't handle the case of DB server restarts however.
+			$options = array();
+			if ( $this->lockExpiry > 0 ) {
+				$options['connTimeout'] = $this->lockExpiry;
+			}
+			$this->conns[$lockDb]->setSessionOptions( $options );
+			$this->initConnection( $lockDb, $this->conns[$lockDb] );
+		}
+		if ( !$this->conns[$lockDb]->trxLevel() ) {
+			$this->conns[$lockDb]->begin(); // start transaction
+		}
+		return $this->conns[$lockDb];
+	}
+
+	/**
+	 * Do additional initialization for new lock DB connection
+	 *
+	 * @param $lockDb string
+	 * @param $db DatabaseBase
+	 * @return void
+	 * @throws DBError
+	 */
+	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(); // 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;
+	}
+
+	/**
+	 * Log a lock request failure to the cache
+	 *
+	 * @param $lockDb string
+	 * @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;
+	}
+
+	/**
+	 * Get a cache key for recent query misses for a DB
+	 *
+	 * @param $lockDb string
+	 * @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 );
+	}
+
+	/**
+	 * Make sure remaining locks get cleared for sanity
+	 */
+	function __destruct() {
+		foreach ( $this->conns as $lockDb => $db ) {
+			if ( $db->trxLevel() ) { // in transaction
+				try {
+					$db->rollback(); // finish transaction and kill any rows
+				} catch ( DBError $e ) {
+					// oh well
+				}
+			}
+			$db->close();
+		}
+	}
+}
+
+/**
+ * MySQL version of DBLockManager that supports shared locks.
+ * All locks are non-blocking, which avoids deadlocks.
+ *
+ * @ingroup LockManager
+ */
+class MySqlLockManager extends DBLockManager {
+	/** @var Array Mapping of lock types to the type actually used */
+	protected $lockTypeMap = array(
+		self::LOCK_SH => self::LOCK_SH,
+		self::LOCK_UW => self::LOCK_SH,
+		self::LOCK_EX => self::LOCK_EX
+	);
+
+	protected function initConnection( $lockDb, DatabaseBase $db ) {
+		# Let this transaction see lock rows from other transactions
+		$db->query( "SET SESSION TRANSACTION ISOLATION LEVEL READ UNCOMMITTED;" );
+	}
+
+	protected function doLockingQuery( $lockDb, array $paths, $type ) {
+		$db = $this->getConnection( $lockDb );
+		if ( !$db ) {
+			return false;
+		}
+		$keys = array_unique( array_map( 'LockManager::sha1Base36', $paths ) );
+		# Build up values for INSERT clause
+		$data = array();
+		foreach ( $keys as $key ) {
+			$data[] = array( 'fls_key' => $key, 'fls_session' => $this->session );
+		}
+		# Block new writers...
+		$db->insert( 'filelocks_shared', $data, __METHOD__, array( 'IGNORE' ) );
+		# Actually do the locking queries...
+		if ( $type == self::LOCK_SH ) { // reader locks
+			# Bail if there are any existing writers...
+			$blocked = $db->selectField( 'filelocks_exclusive', '1',
+				array( 'fle_key' => $keys ),
+				__METHOD__
+			);
+			# Prospective writers that haven't yet updated filelocks_exclusive
+			# will recheck filelocks_shared after doing so and bail due to our entry.
+		} else { // writer locks
+			$encSession = $db->addQuotes( $this->session );
+			# Bail if there are any existing writers...
+			# The may detect readers, but the safe check for them is below.
+			# Note: if two writers come at the same time, both bail :)
+			$blocked = $db->selectField( 'filelocks_shared', '1',
+				array( 'fls_key' => $keys, "fls_session != $encSession" ),
+				__METHOD__
+			);
+			if ( !$blocked ) {
+				# Build up values for INSERT clause
+				$data = array();
+				foreach ( $keys as $key ) {
+					$data[] = array( 'fle_key' => $key );
+				}
+				# Block new readers/writers...
+				$db->insert( 'filelocks_exclusive', $data, __METHOD__ );
+				# Bail if there are any existing readers...
+				$blocked = $db->selectField( 'filelocks_shared', '1',
+					array( 'fls_key' => $keys, "fls_session != $encSession" ),
+					__METHOD__
+				);
+			}
+		}
+		return !$blocked;
+	}
+}