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-rw-r--r--includes/filerepo/backend/lockmanager/DBLockManager.php469
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diff --git a/includes/filerepo/backend/lockmanager/DBLockManager.php b/includes/filerepo/backend/lockmanager/DBLockManager.php
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--- a/includes/filerepo/backend/lockmanager/DBLockManager.php
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-<?php
-
-/**
- * Version of LockManager based on using DB table locks.
- * This is meant for multi-wiki systems that may share files.
- * All locks are blocking, so it might be useful to set a small
- * lock-wait timeout via server config to curtail 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 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
- */
-class DBLockManager extends LockManager {
- /** @var Array Map of DB names to server config */
- protected $dbServers; // (DB name => server config array)
- /** @var Array Map of bucket indexes to peer DB lists */
- protected $dbsByBucket; // (bucket index => (ldb1, ldb2, ...))
- /** @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 = array();
-
- /**
- * Construct a new instance from configuration.
- *
- * $config paramaters 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).
- * '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.
- *
- * @param Array $config
- */
- public function __construct( array $config ) {
- $this->dbServers = isset( $config['dbServers'] )
- ? $config['dbServers']
- : array(); // likely just using 'localDBMaster'
- // Sanitize dbsByBucket config to prevent PHP errors
- $this->dbsByBucket = array_filter( $config['dbsByBucket'], 'is_array' );
- $this->dbsByBucket = array_values( $this->dbsByBucket ); // 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->dbsByBucket as $bucket ) {
- if ( count( $bucket ) > 1 ) {
- // Tracks peers that couldn't be queried recently to avoid lengthy
- // connection timeouts. This is useless if each bucket has one peer.
- $this->statusCache = wfGetMainCache();
- break;
- }
- }
-
- $this->session = '';
- for ( $i = 0; $i < 5; $i++ ) {
- $this->session .= mt_rand( 0, 2147483647 );
- }
- $this->session = wfBaseConvert( sha1( $this->session ), 16, 36, 31 );
- }
-
- /**
- * @see LockManager::doLock()
- */
- 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->doLockingQueryAll( $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 DBs for this bucket.
- // Abort and unlock everything we just locked.
- $status->fatal( 'lockmanager-fail-db-bucket', $bucket );
- $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;
- }
-
- /**
- * @see LockManager::doUnlock()
- */
- 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 COMMIT when zero
- if ( !count( $this->locksHeld ) ) {
- $status->merge( $this->finishLockTransactions() );
- }
-
- return $status;
- }
-
- /**
- * 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.
- *
- * @param $lockDb string
- * @param $paths Array
- * @param $type integer LockManager::LOCK_EX or LockManager::LOCK_SH
- * @return bool Resources able to be locked
- * @throws DBError
- */
- protected function doLockingQuery( $lockDb, array $paths, $type ) {
- if ( $type == self::LOCK_EX ) { // writer locks
- $db = $this->getConnection( $lockDb );
- if ( !$db ) {
- return false; // bad config
- }
- $keys = array_unique( array_map( 'LockManager::sha1Base36', $paths ) );
- # Build up values for INSERT clause
- $data = array();
- foreach ( $keys as $key ) {
- $data[] = array( 'fle_key' => $key );
- }
- # Wait on any existing writers and block new ones if we get in
- $db->insert( 'filelocks_exclusive', $data, __METHOD__ );
- }
- return true;
- }
-
- /**
- * Attempt to acquire locks with the peers for a bucket.
- * This should avoid throwing any exceptions.
- *
- * @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', 'dberrors')
- */
- protected function doLockingQueryAll( $bucket, array $paths, $type ) {
- $yesVotes = 0; // locks made on trustable DBs
- $votesLeft = count( $this->dbsByBucket[$bucket] ); // remaining DBs
- $quorum = floor( $votesLeft/2 + 1 ); // simple majority
- // Get votes for each DB, in order, until we have enough...
- foreach ( $this->dbsByBucket[$bucket] as $lockDb ) {
- // Check that DB is not *known* to be down
- if ( $this->cacheCheckFailures( $lockDb ) ) {
- try {
- // Attempt to acquire the lock on this DB
- if ( !$this->doLockingQuery( $lockDb, $paths, $type ) ) {
- return 'cantacquire'; // vetoed; resource locked
- }
- ++$yesVotes; // success for this peer
- if ( $yesVotes >= $quorum ) {
- return true; // lock obtained
- }
- } catch ( DBConnectionError $e ) {
- $this->cacheRecordFailure( $lockDb );
- } catch ( DBError $e ) {
- if ( $this->lastErrorIndicatesLocked( $lockDb ) ) {
- return 'cantacquire'; // vetoed; resource locked
- }
- }
- }
- --$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 'dberrors'; // not enough votes to ensure correctness
- }
-
- /**
- * Get (or reuse) a connection to a lock DB
- *
- * @param $lockDb string
- * @return Database
- * @throws DBError
- */
- protected function getConnection( $lockDb ) {
- if ( !isset( $this->conns[$lockDb] ) ) {
- $db = null;
- if ( $lockDb === 'localDBMaster' ) {
- $lb = wfGetLBFactory()->newMainLB();
- $db = $lb->getConnection( DB_MASTER );
- } 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 = array();
- 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(); // start transaction
- }
- return $this->conns[$lockDb];
- }
-
- /**
- * Do additional initialization for new lock DB connection
- *
- * @param $lockDb string
- * @param $db DatabaseBase
- * @return void
- * @throws DBError
- */
- protected function initConnection( $lockDb, DatabaseBase $db ) {}
-
- /**
- * Commit all changes to lock-active databases.
- * This should avoid throwing any exceptions.
- *
- * @return Status
- */
- protected function finishLockTransactions() {
- $status = Status::newGood();
- foreach ( $this->conns as $lockDb => $db ) {
- if ( $db->trxLevel() ) { // in transaction
- try {
- $db->rollback(); // finish transaction and kill any rows
- } catch ( DBError $e ) {
- $status->fatal( 'lockmanager-fail-db-release', $lockDb );
- }
- }
- }
- return $status;
- }
-
- /**
- * Check if the last DB error for $lockDb indicates
- * that a requested resource was locked by another process.
- * This should avoid throwing any exceptions.
- *
- * @param $lockDb string
- * @return bool
- */
- protected function lastErrorIndicatesLocked( $lockDb ) {
- if ( isset( $this->conns[$lockDb] ) ) { // sanity
- $db = $this->conns[$lockDb];
- return ( $db->wasDeadlock() || $db->wasLockTimeout() );
- }
- return false;
- }
-
- /**
- * Checks if the DB has not recently had connection/query errors.
- * This just avoids wasting time on doomed connection attempts.
- *
- * @param $lockDb string
- * @return bool
- */
- protected function cacheCheckFailures( $lockDb ) {
- if ( $this->statusCache && $this->safeDelay > 0 ) {
- $path = $this->getMissKey( $lockDb );
- $misses = $this->statusCache->get( $path );
- return !$misses;
- }
- return true;
- }
-
- /**
- * Log a lock request failure to the cache
- *
- * @param $lockDb string
- * @return bool Success
- */
- protected function cacheRecordFailure( $lockDb ) {
- if ( $this->statusCache && $this->safeDelay > 0 ) {
- $path = $this->getMissKey( $lockDb );
- $misses = $this->statusCache->get( $path );
- if ( $misses ) {
- return $this->statusCache->incr( $path );
- } else {
- return $this->statusCache->add( $path, 1, $this->safeDelay );
- }
- }
- return true;
- }
-
- /**
- * Get a cache key for recent query misses for a DB
- *
- * @param $lockDb string
- * @return string
- */
- protected function getMissKey( $lockDb ) {
- return 'lockmanager:querymisses:' . str_replace( ' ', '_', $lockDb );
- }
-
- /**
- * 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->dbsByBucket );
- }
-
- /**
- * Make sure remaining locks get cleared for sanity
- */
- function __destruct() {
- foreach ( $this->conns as $lockDb => $db ) {
- if ( $db->trxLevel() ) { // in transaction
- try {
- $db->rollback(); // finish transaction and kill any rows
- } catch ( DBError $e ) {
- // oh well
- }
- }
- $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 = array(
- self::LOCK_SH => self::LOCK_SH,
- self::LOCK_UW => self::LOCK_SH,
- self::LOCK_EX => self::LOCK_EX
- );
-
- protected function initConnection( $lockDb, DatabaseBase $db ) {
- # Let this transaction see lock rows from other transactions
- $db->query( "SET SESSION TRANSACTION ISOLATION LEVEL READ UNCOMMITTED;" );
- }
-
- protected function doLockingQuery( $lockDb, array $paths, $type ) {
- $db = $this->getConnection( $lockDb );
- if ( !$db ) {
- return false;
- }
- $keys = array_unique( array_map( 'LockManager::sha1Base36', $paths ) );
- # Build up values for INSERT clause
- $data = array();
- foreach ( $keys as $key ) {
- $data[] = array( 'fls_key' => $key, 'fls_session' => $this->session );
- }
- # Block new writers...
- $db->insert( 'filelocks_shared', $data, __METHOD__, array( 'IGNORE' ) );
- # Actually do the locking queries...
- if ( $type == self::LOCK_SH ) { // reader locks
- # Bail if there are any existing writers...
- $blocked = $db->selectField( 'filelocks_exclusive', '1',
- array( 'fle_key' => $keys ),
- __METHOD__
- );
- # Prospective writers that haven't yet updated filelocks_exclusive
- # will recheck filelocks_shared after doing so and bail due to our entry.
- } else { // writer locks
- $encSession = $db->addQuotes( $this->session );
- # Bail if there are any existing writers...
- # The 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',
- array( 'fls_key' => $keys, "fls_session != $encSession" ),
- __METHOD__
- );
- if ( !$blocked ) {
- # Build up values for INSERT clause
- $data = array();
- foreach ( $keys as $key ) {
- $data[] = array( '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',
- array( 'fls_key' => $keys, "fls_session != $encSession" ),
- __METHOD__
- );
- }
- }
- return !$blocked;
- }
-}
generated by cgit v1.2.2 (git 2.25.0) at 2024-04-25 14:38:00 +0000