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Diffstat (limited to 'www/wiki/includes/filebackend/lockmanager/MySqlLockManager.php')
| -rw-r--r-- | www/wiki/includes/filebackend/lockmanager/MySqlLockManager.php | 141 |
1 files changed, 141 insertions, 0 deletions
diff --git a/www/wiki/includes/filebackend/lockmanager/MySqlLockManager.php b/www/wiki/includes/filebackend/lockmanager/MySqlLockManager.php new file mode 100644 index 00000000..2108aed4 --- /dev/null +++ b/www/wiki/includes/filebackend/lockmanager/MySqlLockManager.php @@ -0,0 +1,141 @@ +<?php + +use Wikimedia\Rdbms\IDatabase; +use Wikimedia\Rdbms\DBError; + +/** + * MySQL version of DBLockManager that supports shared locks. + * + * Do NOT use this on connection handles that are also being used for anything + * else as the transaction isolation will be wrong and all the other changes will + * get rolled back when the locks release! + * + * All lock servers must have the innodb table defined in maintenance/locking/filelocks.sql. + * 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 = [ + self::LOCK_SH => 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;" ); + # 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; + } +} |