/includes/filebackend/lockmanager/DBLockManager.php
PHP | 433 lines | 232 code | 41 blank | 160 comment | 27 complexity | 89f9d95f76f8b8ce5590ae0b3fa95553 MD5 | raw file
- <?php
- /**
- * Version of LockManager based on using DB table locks.
- *
- * This program is free software; you can redistribute it and/or modify
- * it under the terms of the GNU General Public License as published by
- * the Free Software Foundation; either version 2 of the License, or
- * (at your option) any later version.
- *
- * This program is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
- * GNU General Public License for more details.
- *
- * You should have received a copy of the GNU General Public License along
- * with this program; if not, write to the Free Software Foundation, Inc.,
- * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
- * http://www.gnu.org/copyleft/gpl.html
- *
- * @file
- * @ingroup LockManager
- */
- /**
- * Version of LockManager based on using named/row DB locks.
- *
- * This is meant for multi-wiki systems that may share files.
- *
- * 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
- */
- abstract class DBLockManager extends QuorumLockManager {
- /** @var array Map of DB names to server config */
- protected $dbServers; // (DB name => server config array)
- /** @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 = [];
- /**
- * Construct a new instance from configuration.
- *
- * @param array $config Parameters 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).
- * Only use 'localDBMaster' if the domain is a valid wiki ID.
- * - 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.
- */
- public function __construct( array $config ) {
- parent::__construct( $config );
- $this->dbServers = isset( $config['dbServers'] )
- ? $config['dbServers']
- : []; // likely just using 'localDBMaster'
- // Sanitize srvsByBucket config to prevent PHP errors
- $this->srvsByBucket = array_filter( $config['dbsByBucket'], 'is_array' );
- $this->srvsByBucket = array_values( $this->srvsByBucket ); // 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->srvsByBucket as $bucket ) {
- if ( count( $bucket ) > 1 ) { // multiple peers
- // Tracks peers that couldn't be queried recently to avoid lengthy
- // connection timeouts. This is useless if each bucket has one peer.
- $this->statusCache = ObjectCache::getLocalServerInstance();
- break;
- }
- }
- $this->session = wfRandomString( 31 );
- }
- // @todo change this code to work in one batch
- protected function getLocksOnServer( $lockSrv, array $pathsByType ) {
- $status = Status::newGood();
- foreach ( $pathsByType as $type => $paths ) {
- $status->merge( $this->doGetLocksOnServer( $lockSrv, $paths, $type ) );
- }
- return $status;
- }
- protected function freeLocksOnServer( $lockSrv, array $pathsByType ) {
- return Status::newGood();
- }
- /**
- * @see QuorumLockManager::isServerUp()
- * @param string $lockSrv
- * @return bool
- */
- protected function isServerUp( $lockSrv ) {
- if ( !$this->cacheCheckFailures( $lockSrv ) ) {
- return false; // recent failure to connect
- }
- try {
- $this->getConnection( $lockSrv );
- } catch ( DBError $e ) {
- $this->cacheRecordFailure( $lockSrv );
- return false; // failed to connect
- }
- return true;
- }
- /**
- * Get (or reuse) a connection to a lock DB
- *
- * @param string $lockDb
- * @return IDatabase
- * @throws DBError
- */
- protected function getConnection( $lockDb ) {
- if ( !isset( $this->conns[$lockDb] ) ) {
- $db = null;
- if ( $lockDb === 'localDBMaster' ) {
- $lb = wfGetLBFactory()->getMainLB( $this->domain );
- $db = $lb->getConnection( DB_MASTER, [], $this->domain );
- } 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 = [];
- 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( __METHOD__ ); // start transaction
- }
- return $this->conns[$lockDb];
- }
- /**
- * Do additional initialization for new lock DB connection
- *
- * @param string $lockDb
- * @param IDatabase $db
- * @throws DBError
- */
- protected function initConnection( $lockDb, IDatabase $db ) {
- }
- /**
- * Checks if the DB has not recently had connection/query errors.
- * This just avoids wasting time on doomed connection attempts.
- *
- * @param string $lockDb
- * @return bool
- */
- protected function cacheCheckFailures( $lockDb ) {
- return ( $this->statusCache && $this->safeDelay > 0 )
- ? !$this->statusCache->get( $this->getMissKey( $lockDb ) )
- : true;
- }
- /**
- * Log a lock request failure to the cache
- *
- * @param string $lockDb
- * @return bool Success
- */
- protected function cacheRecordFailure( $lockDb ) {
- return ( $this->statusCache && $this->safeDelay > 0 )
- ? $this->statusCache->set( $this->getMissKey( $lockDb ), 1, $this->safeDelay )
- : true;
- }
- /**
- * Get a cache key for recent query misses for a DB
- *
- * @param string $lockDb
- * @return string
- */
- protected function getMissKey( $lockDb ) {
- $lockDb = ( $lockDb === 'localDBMaster' ) ? wfWikiID() : $lockDb; // non-relative
- return 'dblockmanager:downservers:' . str_replace( ' ', '_', $lockDb );
- }
- /**
- * Make sure remaining locks get cleared for sanity
- */
- function __destruct() {
- $this->releaseAllLocks();
- foreach ( $this->conns as $db ) {
- $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 = [
- self::LOCK_SH => self::LOCK_SH,
- self::LOCK_UW => self::LOCK_SH,
- self::LOCK_EX => self::LOCK_EX
- ];
- /**
- * @param string $lockDb
- * @param IDatabase $db
- */
- protected function initConnection( $lockDb, IDatabase $db ) {
- # Let this transaction see lock rows from other transactions
- $db->query( "SET SESSION TRANSACTION ISOLATION LEVEL READ UNCOMMITTED;" );
- }
- /**
- * 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.
- *
- * @see DBLockManager::getLocksOnServer()
- * @param string $lockSrv
- * @param array $paths
- * @param string $type
- * @return Status
- */
- protected function doGetLocksOnServer( $lockSrv, array $paths, $type ) {
- $status = Status::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;
- }
- }
- # 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
- $blocked = false;
- # Bail if there are any existing writers...
- if ( count( $checkEXKeys ) ) {
- $blocked = $db->selectField( 'filelocks_exclusive', '1',
- [ 'fle_key' => $checkEXKeys ],
- __METHOD__
- );
- }
- # 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 Status
- */
- protected function releaseAllLocks() {
- $status = Status::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;
- }
- }
- /**
- * PostgreSQL version of DBLockManager that supports shared locks.
- * All locks are non-blocking, which avoids deadlocks.
- *
- * @ingroup LockManager
- */
- class PostgreSqlLockManager 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
- ];
- protected function doGetLocksOnServer( $lockSrv, array $paths, $type ) {
- $status = Status::newGood();
- if ( !count( $paths ) ) {
- return $status; // nothing to lock
- }
- $db = $this->getConnection( $lockSrv ); // checked in isServerUp()
- $bigints = array_unique( array_map(
- function ( $key ) {
- return Wikimedia\base_convert( substr( $key, 0, 15 ), 16, 10 );
- },
- array_map( [ $this, 'sha1Base16Absolute' ], $paths )
- ) );
- // Try to acquire all the locks...
- $fields = [];
- foreach ( $bigints as $bigint ) {
- $fields[] = ( $type == self::LOCK_SH )
- ? "pg_try_advisory_lock_shared({$db->addQuotes( $bigint )}) AS K$bigint"
- : "pg_try_advisory_lock({$db->addQuotes( $bigint )}) AS K$bigint";
- }
- $res = $db->query( 'SELECT ' . implode( ', ', $fields ), __METHOD__ );
- $row = $res->fetchRow();
- if ( in_array( 'f', $row ) ) {
- // Release any acquired locks if some could not be acquired...
- $fields = [];
- foreach ( $row as $kbigint => $ok ) {
- if ( $ok === 't' ) { // locked
- $bigint = substr( $kbigint, 1 ); // strip off the "K"
- $fields[] = ( $type == self::LOCK_SH )
- ? "pg_advisory_unlock_shared({$db->addQuotes( $bigint )})"
- : "pg_advisory_unlock({$db->addQuotes( $bigint )})";
- }
- }
- if ( count( $fields ) ) {
- $db->query( 'SELECT ' . implode( ', ', $fields ), __METHOD__ );
- }
- foreach ( $paths as $path ) {
- $status->fatal( 'lockmanager-fail-acquirelock', $path );
- }
- }
- return $status;
- }
- /**
- * @see QuorumLockManager::releaseAllLocks()
- * @return Status
- */
- protected function releaseAllLocks() {
- $status = Status::newGood();
- foreach ( $this->conns as $lockDb => $db ) {
- try {
- $db->query( "SELECT pg_advisory_unlock_all()", __METHOD__ );
- } catch ( DBError $e ) {
- $status->fatal( 'lockmanager-fail-db-release', $lockDb );
- }
- }
- return $status;
- }
- }