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<?php |
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/** |
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* MySQL version of DBLockManager that supports shared locks. |
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* |
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* Do NOT use this on connection handles that are also being used for anything |
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* else as the transaction isolation will be wrong and all the other changes will |
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* get rolled back when the locks release! |
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* |
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* All lock servers must have the innodb table defined in maintenance/locking/filelocks.sql. |
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* All locks are non-blocking, which avoids deadlocks. |
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* |
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* @ingroup LockManager |
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*/ |
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class MySqlLockManager extends DBLockManager { |
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/** @var array Mapping of lock types to the type actually used */ |
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protected $lockTypeMap = [ |
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self::LOCK_SH => self::LOCK_SH, |
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self::LOCK_UW => self::LOCK_SH, |
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self::LOCK_EX => self::LOCK_EX |
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]; |
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public function __construct( array $config ) { |
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parent::__construct( $config ); |
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$this->session = substr( $this->session, 0, 31 ); // fit to field |
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} |
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protected function initConnection( $lockDb, IDatabase $db ) { |
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# Let this transaction see lock rows from other transactions |
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$db->query( "SET SESSION TRANSACTION ISOLATION LEVEL READ UNCOMMITTED;" ); |
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# Do everything in a transaction as it all gets rolled back eventually |
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$db->startAtomic( __CLASS__ ); |
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} |
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/** |
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* Get a connection to a lock DB and acquire locks on $paths. |
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* This does not use GET_LOCK() per http://bugs.mysql.com/bug.php?id=1118. |
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* |
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* @see DBLockManager::getLocksOnServer() |
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* @param string $lockSrv |
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* @param array $paths |
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* @param string $type |
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* @return StatusValue |
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*/ |
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protected function doGetLocksOnServer( $lockSrv, array $paths, $type ) { |
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$status = StatusValue::newGood(); |
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$db = $this->getConnection( $lockSrv ); // checked in isServerUp() |
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$keys = []; // list of hash keys for the paths |
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$data = []; // list of rows to insert |
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$checkEXKeys = []; // list of hash keys that this has no EX lock on |
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# Build up values for INSERT clause |
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foreach ( $paths as $path ) { |
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$key = $this->sha1Base36Absolute( $path ); |
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$keys[] = $key; |
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$data[] = [ 'fls_key' => $key, 'fls_session' => $this->session ]; |
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if ( !isset( $this->locksHeld[$path][self::LOCK_EX] ) ) { |
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$checkEXKeys[] = $key; // this has no EX lock on $key itself |
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} |
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} |
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# Block new writers (both EX and SH locks leave entries here)... |
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$db->insert( 'filelocks_shared', $data, __METHOD__, [ 'IGNORE' ] ); |
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# Actually do the locking queries... |
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if ( $type == self::LOCK_SH ) { // reader locks |
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# Bail if there are any existing writers... |
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if ( count( $checkEXKeys ) ) { |
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$blocked = $db->selectField( |
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'filelocks_exclusive', |
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'1', |
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[ 'fle_key' => $checkEXKeys ], |
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__METHOD__ |
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); |
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} else { |
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$blocked = false; |
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} |
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# Other prospective writers that haven't yet updated filelocks_exclusive |
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# will recheck filelocks_shared after doing so and bail due to this entry. |
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} else { // writer locks |
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$encSession = $db->addQuotes( $this->session ); |
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# Bail if there are any existing writers... |
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# This may detect readers, but the safe check for them is below. |
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# Note: if two writers come at the same time, both bail :) |
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$blocked = $db->selectField( |
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'filelocks_shared', |
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'1', |
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[ 'fls_key' => $keys, "fls_session != $encSession" ], |
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__METHOD__ |
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); |
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if ( !$blocked ) { |
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# Build up values for INSERT clause |
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$data = []; |
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foreach ( $keys as $key ) { |
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$data[] = [ 'fle_key' => $key ]; |
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} |
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# Block new readers/writers... |
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$db->insert( 'filelocks_exclusive', $data, __METHOD__ ); |
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# Bail if there are any existing readers... |
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$blocked = $db->selectField( |
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'filelocks_shared', |
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'1', |
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[ 'fls_key' => $keys, "fls_session != $encSession" ], |
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__METHOD__ |
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); |
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} |
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} |
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if ( $blocked ) { |
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foreach ( $paths as $path ) { |
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$status->fatal( 'lockmanager-fail-acquirelock', $path ); |
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} |
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} |
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return $status; |
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} |
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/** |
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* @see QuorumLockManager::releaseAllLocks() |
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* @return StatusValue |
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*/ |
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View Code Duplication |
protected function releaseAllLocks() { |
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$status = StatusValue::newGood(); |
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foreach ( $this->conns as $lockDb => $db ) { |
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if ( $db->trxLevel() ) { // in transaction |
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try { |
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$db->rollback( __METHOD__ ); // finish transaction and kill any rows |
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} catch ( DBError $e ) { |
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$status->fatal( 'lockmanager-fail-db-release', $lockDb ); |
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} |
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} |
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} |
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return $status; |
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} |
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} |
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wikimedia /
mediawiki
