self::LOCK_SH, self::LOCK_UW => self::LOCK_SH, self::LOCK_EX => self::LOCK_EX ]; public function __construct( array $config ) { parent::__construct( $config ); $this->session = substr( $this->session, 0, 31 ); // fit to field } protected function initConnection( $lockDb, IDatabase $db ) { # Let this transaction see lock rows from other transactions $db->query( "SET SESSION TRANSACTION ISOLATION LEVEL READ UNCOMMITTED;", __METHOD__ ); # Do everything in a transaction as it all gets rolled back eventually $db->startAtomic( __CLASS__ ); } /** * Get a connection to a lock DB and acquire locks on $paths. * This does not use GET_LOCK() per https://bugs.mysql.com/bug.php?id=1118. * * @see DBLockManager::getLocksOnServer() * @param string $lockSrv * @param array $paths * @param string $type * @return StatusValue */ protected function doGetLocksOnServer( $lockSrv, array $paths, $type ) { $status = StatusValue::newGood(); $db = $this->getConnection( $lockSrv ); // checked in isServerUp() $keys = []; // list of hash keys for the paths $data = []; // list of rows to insert $checkEXKeys = []; // list of hash keys that this has no EX lock on # Build up values for INSERT clause foreach ( $paths as $path ) { $key = $this->sha1Base36Absolute( $path ); $keys[] = $key; $data[] = [ 'fls_key' => $key, 'fls_session' => $this->session ]; if ( !isset( $this->locksHeld[$path][self::LOCK_EX] ) ) { $checkEXKeys[] = $key; // this has no EX lock on $key itself } } # Block new writers (both EX and SH locks leave entries here)... $db->insert( 'filelocks_shared', $data, __METHOD__, [ 'IGNORE' ] ); # Actually do the locking queries... if ( $type == self::LOCK_SH ) { // reader locks # Bail if there are any existing writers... if ( count( $checkEXKeys ) ) { $blocked = $db->selectField( 'filelocks_exclusive', '1', [ 'fle_key' => $checkEXKeys ], __METHOD__ ); } else { $blocked = false; } # Other prospective writers that haven't yet updated filelocks_exclusive # will recheck filelocks_shared after doing so and bail due to this entry. } else { // writer locks $encSession = $db->addQuotes( $this->session ); # Bail if there are any existing writers... # This 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', [ 'fls_key' => $keys, "fls_session != $encSession" ], __METHOD__ ); if ( !$blocked ) { # Build up values for INSERT clause $data = []; foreach ( $keys as $key ) { $data[] = [ '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', [ 'fls_key' => $keys, "fls_session != $encSession" ], __METHOD__ ); } } if ( $blocked ) { foreach ( $paths as $path ) { $status->fatal( 'lockmanager-fail-acquirelock', $path ); } } return $status; } /** * @see QuorumLockManager::releaseAllLocks() * @return StatusValue */ protected function releaseAllLocks() { $status = StatusValue::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; } }