1 files changed, 295 insertions, 0 deletions
diff --git a/includes/filerepo/backend/lockmanager/LSLockManager.php b/includes/filerepo/backend/lockmanager/LSLockManager.php
new file mode 100644
index 00000000..b7ac743c
--- /dev/null
+++ b/includes/filerepo/backend/lockmanager/LSLockManager.php
@@ -0,0 +1,295 @@
+<?php
+
+/**
+ * Manage locks using a lock daemon server.
+ *
+ * Version of LockManager based on using lock daemon servers.
+ * This is meant for multi-wiki systems that may share files.
+ * All locks are non-blocking, which avoids 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 servers, each
+ * running LockServerDaemon.php, listening on a designated TCP port.
+ * A majority of peers must agree for a lock to be acquired.
+ *
+ * @ingroup LockManager
+ * @since 1.19
+ */
+class LSLockManager extends LockManager {
+	/** @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
+	);
+
+	/** @var Array Map of server names to server config */
+	protected $lockServers; // (server name => server config array)
+	/** @var Array Map of bucket indexes to peer server lists */
+	protected $srvsByBucket; // (bucket index => (lsrv1, lsrv2, ...))
+
+	/** @var Array Map Server connections (server name => resource) */
+	protected $conns = array();
+
+	protected $connTimeout; // float number of seconds
+	protected $session = ''; // random SHA-1 string
+
+	/**
+	 * Construct a new instance from configuration.
+	 * 
+	 * $config paramaters include:
+	 *     'lockServers'  : Associative array of server names to configuration.
+	 *                      Configuration is an associative array that includes:
+	 *                      'host'    - IP address/hostname
+	 *                      'port'    - TCP port
+	 *                      'authKey' - Secret string the lock server uses
+	 *     'srvsByBucket' : Array of 1-16 consecutive integer keys, starting from 0,
+	 *                      each having an odd-numbered list of server names (peers) as values.
+	 *     'connTimeout'  : Lock server connection attempt timeout. [optional]
+	 *
+	 * @param Array $config 
+	 */
+	public function __construct( array $config ) {
+		$this->lockServers = $config['lockServers'];
+		// Sanitize srvsByBucket config to prevent PHP errors
+		$this->srvsByBucket = array_filter( $config['srvsByBucket'], 'is_array' );
+		$this->srvsByBucket = array_values( $this->srvsByBucket ); // consecutive
+
+		if ( isset( $config['connTimeout'] ) ) {
+			$this->connTimeout = $config['connTimeout'];
+		} else {
+			$this->connTimeout = 3; // use some sane amount
+		}
+
+		$this->session = '';
+		for ( $i = 0; $i < 5; $i++ ) {
+			$this->session .= mt_rand( 0, 2147483647 );
+		}
+		$this->session = wfBaseConvert( sha1( $this->session ), 16, 36, 31 );
+	}
+
+	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->doLockingRequestAll( $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 servers for this bucket.
+				// 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;
+			}
+			// 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;
+	}
+
+	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 release locks when zero
+		if ( !count( $this->locksHeld ) ) {
+			$status->merge( $this->releaseLocks() );
+		}
+
+		return $status;
+	}
+
+	/**
+	 * Get a connection to a lock server and acquire locks on $paths
+	 *
+	 * @param $lockSrv string
+	 * @param $paths Array
+	 * @param $type integer LockManager::LOCK_EX or LockManager::LOCK_SH
+	 * @return bool Resources able to be locked
+	 */
+	protected function doLockingRequest( $lockSrv, array $paths, $type ) {
+		if ( $type == self::LOCK_SH ) { // reader locks
+			$type = 'SH';
+		} elseif ( $type == self::LOCK_EX ) { // writer locks
+			$type = 'EX';
+		} else {
+			return true; // ok...
+		}
+
+		// Send out the command and get the response...
+		$keys = array_unique( array_map( 'LockManager::sha1Base36', $paths ) );
+		$response = $this->sendCommand( $lockSrv, 'ACQUIRE', $type, $keys );
+
+		return ( $response === 'ACQUIRED' );
+	}
+
+	/**
+	 * Send a command and get back the response
+	 *
+	 * @param $lockSrv string
+	 * @param $action string
+	 * @param $type string
+	 * @param $values Array
+	 * @return string|false
+	 */
+	protected function sendCommand( $lockSrv, $action, $type, $values ) {
+		$conn = $this->getConnection( $lockSrv );
+		if ( !$conn ) {
+			return false; // no connection
+		}
+		$authKey = $this->lockServers[$lockSrv]['authKey'];
+		// Build of the command as a flat string...
+		$values = implode( '|', $values );
+		$key = sha1( $this->session . $action . $type . $values . $authKey );
+		// Send out the command...
+		if ( fwrite( $conn, "{$this->session}:$key:$action:$type:$values\n" ) === false ) {
+			return false;
+		}
+		// Get the response...
+		$response = fgets( $conn );
+		if ( $response === false ) {
+			return false;
+		}
+		return trim( $response );
+	}
+
+	/**
+	 * Attempt to acquire locks with the peers for a bucket
+	 *
+	 * @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', 'srverrors')
+	 */
+	protected function doLockingRequestAll( $bucket, array $paths, $type ) {
+		$yesVotes = 0; // locks made on trustable servers
+		$votesLeft = count( $this->srvsByBucket[$bucket] ); // remaining peers
+		$quorum = floor( $votesLeft/2 + 1 ); // simple majority
+		// Get votes for each peer, in order, until we have enough...
+		foreach ( $this->srvsByBucket[$bucket] as $lockSrv ) {
+			// Attempt to acquire the lock on this peer
+			if ( !$this->doLockingRequest( $lockSrv, $paths, $type ) ) {
+				return 'cantacquire'; // vetoed; resource locked
+			}
+			++$yesVotes; // success for this peer
+			if ( $yesVotes >= $quorum ) {
+				return true; // lock obtained
+			}
+			--$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 'srverrors'; // not enough votes to ensure correctness
+	}
+
+	/**
+	 * Get (or reuse) a connection to a lock server
+	 *
+	 * @param $lockSrv string
+	 * @return resource
+	 */
+	protected function getConnection( $lockSrv ) {
+		if ( !isset( $this->conns[$lockSrv] ) ) {
+			$cfg = $this->lockServers[$lockSrv];
+			wfSuppressWarnings();
+			$errno = $errstr = '';
+			$conn = fsockopen( $cfg['host'], $cfg['port'], $errno, $errstr, $this->connTimeout );
+			wfRestoreWarnings();
+			if ( $conn === false ) {
+				return null;
+			}
+			$sec = floor( $this->connTimeout );
+			$usec = floor( ( $this->connTimeout - floor( $this->connTimeout ) ) * 1e6 );
+			stream_set_timeout( $conn, $sec, $usec );
+			$this->conns[$lockSrv] = $conn;
+		}
+		return $this->conns[$lockSrv];
+	}
+
+	/**
+	 * Release all locks that this session is holding
+	 *
+	 * @return Status
+	 */
+	protected function releaseLocks() {
+		$status = Status::newGood();
+		foreach ( $this->conns as $lockSrv => $conn ) {
+			$response = $this->sendCommand( $lockSrv, 'RELEASE_ALL', '', array() );
+			if ( $response !== 'RELEASED_ALL' ) {
+				$status->fatal( 'lockmanager-fail-svr-release', $lockSrv );
+			}
+		}
+		return $status;
+	}
+
+	/**
+	 * 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->srvsByBucket );
+	}
+
+	/**
+	 * Make sure remaining locks get cleared for sanity
+	 */
+	function __destruct() {
+		$this->releaseLocks();
+		foreach ( $this->conns as $conn ) {
+			fclose( $conn );
+		}
+	}
+}