LBFactory::singleton() - Code Metrics - Inspection of "Daily Inspection: Merge "objectcache: Add changeTT..." - wikimedia/mediawiki - Measure and Improve Code Quality continuously with Scrutinizer

Completed

Branch — master (bbf110)

unknown

created 2016-08-12 17:27 UTC

LBFactory::singleton() A

↳ Parent: LBFactory

Complexity

Conditions	1
Paths	1

Size

Total Lines	3
Code Lines	2

Duplication

Lines	0
Ratio	0 %

Importance

Changes

Metric	Value
cc	1
eloc	2
nc	1
nop	0
dl	0
loc	3
rs	10
c	0
b	0
f	0

<?php
/**
 * Generator of database load balancing objects.
 *
 * 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 Database
 */

use MediaWiki\MediaWikiServices;
use MediaWiki\Services\DestructibleService;
use Psr\Log\LoggerInterface;
use MediaWiki\Logger\LoggerFactory;

/**
 * An interface for generating database load balancers
 * @ingroup Database
 */
abstract class LBFactory implements DestructibleService {
	/** @var ChronologyProtector */
	protected $chronProt;
	/** @var TransactionProfiler */
	protected $trxProfiler;
	/** @var LoggerInterface */
	protected $trxLogger;
	/** @var BagOStuff */
	protected $srvCache;
	/** @var WANObjectCache */
	protected $wanCache;

	/** @var string|bool Reason all LBs are read-only or false if not */
	protected $readOnlyReason = false;

	const SHUTDOWN_NO_CHRONPROT = 1; // don't save ChronologyProtector positions (for async code)

	/**
	 * Construct a factory based on a configuration array (typically from $wgLBFactoryConf)
	 * @param array $conf
	 * @TODO: inject objects via dependency framework
	 */
	public function __construct( array $conf ) {
		if ( isset( $conf['readOnlyReason'] ) && is_string( $conf['readOnlyReason'] ) ) {
			$this->readOnlyReason = $conf['readOnlyReason'];
		}
		$this->chronProt = $this->newChronologyProtector();
		$this->trxProfiler = Profiler::instance()->getTransactionProfiler();
		// Use APC/memcached style caching, but avoids loops with CACHE_DB (T141804)
		$cache = ObjectCache::getLocalServerInstance();
		if ( $cache->getQoS( $cache::ATTR_EMULATION ) > $cache::QOS_EMULATION_SQL ) {
			$this->srvCache = $cache;
		} else {
			$this->srvCache = new EmptyBagOStuff();
		}
		$wCache = ObjectCache::getMainWANInstance();
		if ( $wCache->getQoS( $wCache::ATTR_EMULATION ) > $wCache::QOS_EMULATION_SQL ) {
			$this->wanCache = $wCache;
		} else {
			$this->wanCache = WANObjectCache::newEmpty();
		}
		$this->trxLogger = LoggerFactory::getInstance( 'DBTransaction' );
	}

	/**
	 * Disables all load balancers. All connections are closed, and any attempt to
	 * open a new connection will result in a DBAccessError.
	 * @see LoadBalancer::disable()
	 */
	public function destroy() {
		$this->shutdown();
		$this->forEachLBCallMethod( 'disable' );
	}

	/**
	 * Disables all access to the load balancer, will cause all database access
	 * to throw a DBAccessError
	 */
	public static function disableBackend() {
		MediaWikiServices::disableStorageBackend();
	}

	/**
	 * Get an LBFactory instance
	 *
	 * @deprecated since 1.27, use MediaWikiServices::getDBLoadBalancerFactory() instead.
	 *
	 * @return LBFactory
	 */
	public static function singleton() {
		return MediaWikiServices::getInstance()->getDBLoadBalancerFactory();
	}

	/**
	 * Returns the LBFactory class to use and the load balancer configuration.
	 *
	 * @todo instead of this, use a ServiceContainer for managing the different implementations.
	 *
	 * @param array $config (e.g. $wgLBFactoryConf)
	 * @return string Class name
	 */
	public static function getLBFactoryClass( array $config ) {
		// For configuration backward compatibility after removing
		// underscores from class names in MediaWiki 1.23.
		$bcClasses = [
			'LBFactory_Simple' => 'LBFactorySimple',
			'LBFactory_Single' => 'LBFactorySingle',
			'LBFactory_Multi' => 'LBFactoryMulti',
			'LBFactory_Fake' => 'LBFactoryFake',
		];

		$class = $config['class'];

		if ( isset( $bcClasses[$class] ) ) {
			$class = $bcClasses[$class];
			wfDeprecated(
				'$wgLBFactoryConf must be updated. See RELEASE-NOTES for details',
				'1.23'
			);
		}

		return $class;
	}

	/**
	 * Shut down, close connections and destroy the cached instance.
	 *
	 * @deprecated since 1.27, use LBFactory::destroy()
	 */
	public static function destroyInstance() {
		self::singleton()->destroy();
	}

	/**
	 * Create a new load balancer object. The resulting object will be untracked,
	 * not chronology-protected, and the caller is responsible for cleaning it up.
	 *
	 * @param bool|string $wiki Wiki ID, or false for the current wiki
	 * @return LoadBalancer
	 */
	abstract public function newMainLB( $wiki = false );

	/**
	 * Get a cached (tracked) load balancer object.
	 *
	 * @param bool|string $wiki Wiki ID, or false for the current wiki
	 * @return LoadBalancer
	 */
	abstract public function getMainLB( $wiki = false );

	/**
	 * Create a new load balancer for external storage. The resulting object will be
	 * untracked, not chronology-protected, and the caller is responsible for
	 * cleaning it up.
	 *
	 * @param string $cluster External storage cluster, or false for core
	 * @param bool|string $wiki Wiki ID, or false for the current wiki
	 * @return LoadBalancer
	 */
	abstract protected function newExternalLB( $cluster, $wiki = false );

	/**
	 * Get a cached (tracked) load balancer for external storage
	 *
	 * @param string $cluster External storage cluster, or false for core
	 * @param bool|string $wiki Wiki ID, or false for the current wiki
	 * @return LoadBalancer
	 */
	abstract public function &getExternalLB( $cluster, $wiki = false );

	/**
	 * Execute a function for each tracked load balancer
	 * The callback is called with the load balancer as the first parameter,
	 * and $params passed as the subsequent parameters.
	 *
	 * @param callable $callback
	 * @param array $params
	 */
	abstract public function forEachLB( $callback, array $params = [] );

	/**
	 * Prepare all tracked load balancers for shutdown
	 * @param integer $flags Supports SHUTDOWN_* flags
	 * STUB
	 */
	public function shutdown( $flags = 0 ) {
	}

	/**
	 * Call a method of each tracked load balancer
	 *
	 * @param string $methodName
	 * @param array $args
	 */
	private function forEachLBCallMethod( $methodName, array $args = [] ) {
		$this->forEachLB(
			function ( LoadBalancer $loadBalancer, $methodName, array $args ) {
				call_user_func_array( [ $loadBalancer, $methodName ], $args );
			},
			[ $methodName, $args ]
		);
	}

	/**
	 * Commit on all connections. Done for two reasons:
	 * 1. To commit changes to the masters.
	 * 2. To release the snapshot on all connections, master and slave.
	 * @param string $fname Caller name
	 * @param array $options Options map:
	 *   - maxWriteDuration: abort if more than this much time was spent in write queries
	 */
	public function commitAll( $fname = __METHOD__, array $options = [] ) {
		$this->commitMasterChanges( $fname, $options );
		$this->forEachLBCallMethod( 'commitAll', [ $fname ] );
	}

	/**
	 * Commit changes on all master connections
	 * @param string $fname Caller name
	 * @param array $options Options map:
	 *   - maxWriteDuration: abort if more than this much time was spent in write queries
	 */
	public function commitMasterChanges( $fname = __METHOD__, array $options = [] ) {
		// Perform all pre-commit callbacks, aborting on failure
		$this->forEachLBCallMethod( 'runMasterPreCommitCallbacks' );
		// Perform all pre-commit checks, aborting on failure
		$this->forEachLBCallMethod( 'approveMasterChanges', [ $options ] );
		// Log the DBs and methods involved in multi-DB transactions
		$this->logIfMultiDbTransaction();
		// Actually perform the commit on all master DB connections
		$this->forEachLBCallMethod( 'commitMasterChanges', [ $fname ] );
		// Run all post-commit callbacks
		$this->forEachLBCallMethod( 'runMasterPostCommitCallbacks' );
		// Commit any dangling DBO_TRX transactions from callbacks on one DB to another DB
		$this->forEachLBCallMethod( 'commitMasterChanges', [ $fname ] );
	}

	/**
	 * Rollback changes on all master connections
	 * @param string $fname Caller name
	 * @since 1.23
	 */
	public function rollbackMasterChanges( $fname = __METHOD__ ) {
		$this->forEachLBCallMethod( 'rollbackMasterChanges', [ $fname ] );
	}

	/**
	 * Log query info if multi DB transactions are going to be committed now
	 */
	private function logIfMultiDbTransaction() {
		$callersByDB = [];
		$this->forEachLB( function ( LoadBalancer $lb ) use ( &$callersByDB ) {
			$masterName = $lb->getServerName( $lb->getWriterIndex() );
			$callers = $lb->pendingMasterChangeCallers();
			if ( $callers ) {
				$callersByDB[$masterName] = $callers;
			}
		} );

		if ( count( $callersByDB ) >= 2 ) {
			$dbs = implode( ', ', array_keys( $callersByDB ) );
			$msg = "Multi-DB transaction [{$dbs}]:\n";
			foreach ( $callersByDB as $db => $callers ) {
				$msg .= "$db: " . implode( '; ', $callers ) . "\n";
			}
			$this->trxLogger->info( $msg );
		}
	}

	/**
	 * Determine if any master connection has pending changes
	 * @return bool
	 * @since 1.23
	 */
	public function hasMasterChanges() {
		$ret = false;
		$this->forEachLB( function ( LoadBalancer $lb ) use ( &$ret ) {
			$ret = $ret || $lb->hasMasterChanges();
		} );

		return $ret;
	}

	/**
	 * Detemine if any lagged slave connection was used
	 * @since 1.27
	 * @return bool
	 */
	public function laggedSlaveUsed() {
		$ret = false;
		$this->forEachLB( function ( LoadBalancer $lb ) use ( &$ret ) {
			$ret = $ret || $lb->laggedSlaveUsed();
		} );

		return $ret;
	}

	/**
	 * Determine if any master connection has pending/written changes from this request
	 * @return bool
	 * @since 1.27
	 */
	public function hasOrMadeRecentMasterChanges() {
		$ret = false;
		$this->forEachLB( function ( LoadBalancer $lb ) use ( &$ret ) {
			$ret = $ret || $lb->hasOrMadeRecentMasterChanges();
		} );
		return $ret;
	}

	/**
	 * Waits for the slave DBs to catch up to the current master position
	 *
	 * Use this when updating very large numbers of rows, as in maintenance scripts,
	 * to avoid causing too much lag. Of course, this is a no-op if there are no slaves.
	 *
	 * By default this waits on all DB clusters actually used in this request.
	 * This makes sense when lag being waiting on is caused by the code that does this check.
	 * In that case, setting "ifWritesSince" can avoid the overhead of waiting for clusters
	 * that were not changed since the last wait check. To forcefully wait on a specific cluster
	 * for a given wiki, use the 'wiki' parameter. To forcefully wait on an "external" cluster,
	 * use the "cluster" parameter.
	 *
	 * Never call this function after a large DB write that is *still* in a transaction.
	 * It only makes sense to call this after the possible lag inducing changes were committed.
	 *
	 * @param array $opts Optional fields that include:
	 *   - wiki : wait on the load balancer DBs that handles the given wiki
	 *   - cluster : wait on the given external load balancer DBs
	 *   - timeout : Max wait time. Default: ~60 seconds
	 *   - ifWritesSince: Only wait if writes were done since this UNIX timestamp
	 * @throws DBReplicationWaitError If a timeout or error occured waiting on a DB cluster
	 * @since 1.27
	 */
	public function waitForReplication( array $opts = [] ) {
		$opts += [
			'wiki' => false,
			'cluster' => false,
			'timeout' => 60,
			'ifWritesSince' => null
		];

		// Figure out which clusters need to be checked
		/** @var LoadBalancer[] $lbs */
		$lbs = [];
		if ( $opts['cluster'] !== false ) {
			$lbs[] = $this->getExternalLB( $opts['cluster'] );
		} elseif ( $opts['wiki'] !== false ) {
			$lbs[] = $this->getMainLB( $opts['wiki'] );
		} else {
			$this->forEachLB( function ( LoadBalancer $lb ) use ( &$lbs ) {
				$lbs[] = $lb;
			} );
			if ( !$lbs ) {
				return; // nothing actually used
			}
		}

		// Get all the master positions of applicable DBs right now.
		// This can be faster since waiting on one cluster reduces the
		// time needed to wait on the next clusters.
		$masterPositions = array_fill( 0, count( $lbs ), false );
		foreach ( $lbs as $i => $lb ) {
			if ( $lb->getServerCount() <= 1 ) {
				// Bug 27975 - Don't try to wait for slaves if there are none
				// Prevents permission error when getting master position
				continue;
			} elseif ( $opts['ifWritesSince']
				&& $lb->lastMasterChangeTimestamp() < $opts['ifWritesSince']
			) {
				continue; // no writes since the last wait
			}
			$masterPositions[$i] = $lb->getMasterPos();
		}

		$failed = [];
		foreach ( $lbs as $i => $lb ) {
			if ( $masterPositions[$i] ) {
				// The DBMS may not support getMasterPos() or the whole
				// load balancer might be fake (e.g. $wgAllDBsAreLocalhost).
				if ( !$lb->waitForAll( $masterPositions[$i], $opts['timeout'] ) ) {
					$failed[] = $lb->getServerName( $lb->getWriterIndex() );
				}
			}
		}

		if ( $failed ) {
			throw new DBReplicationWaitError(
				"Could not wait for slaves to catch up to " .
				implode( ', ', $failed )
			);
		}
	}

	/**
	 * Disable the ChronologyProtector for all load balancers
	 *
	 * This can be called at the start of special API entry points
	 *
	 * @since 1.27
	 */
	public function disableChronologyProtection() {
		$this->chronProt->setEnabled( false );
	}

	/**
	 * @return ChronologyProtector
	 */
	protected function newChronologyProtector() {
		$request = RequestContext::getMain()->getRequest();
		$chronProt = new ChronologyProtector(
			ObjectCache::getMainStashInstance(),
			[
				'ip' => $request->getIP(),
				'agent' => $request->getHeader( 'User-Agent' )
			]
		);
		if ( PHP_SAPI === 'cli' ) {
			$chronProt->setEnabled( false );
		} elseif ( $request->getHeader( 'ChronologyProtection' ) === 'false' ) {
			// Request opted out of using position wait logic. This is useful for requests
			// done by the job queue or background ETL that do not have a meaningful session.
			$chronProt->setWaitEnabled( false );
		}

		return $chronProt;
	}

	/**
	 * @param ChronologyProtector $cp
	 */
	protected function shutdownChronologyProtector( ChronologyProtector $cp ) {
		// Get all the master positions needed
		$this->forEachLB( function ( LoadBalancer $lb ) use ( $cp ) {
			$cp->shutdownLB( $lb );
		} );
		// Write them to the stash
		$unsavedPositions = $cp->shutdown();
		// If the positions failed to write to the stash, at least wait on local datacenter
		// slaves to catch up before responding. Even if there are several DCs, this increases
		// the chance that the user will see their own changes immediately afterwards. As long
		// as the sticky DC cookie applies (same domain), this is not even an issue.
		$this->forEachLB( function ( LoadBalancer $lb ) use ( $unsavedPositions ) {
			$masterName = $lb->getServerName( $lb->getWriterIndex() );
			if ( isset( $unsavedPositions[$masterName] ) ) {
				$lb->waitForAll( $unsavedPositions[$masterName] );
			}
		} );
	}

	/**
	 * Close all open database connections on all open load balancers.
	 * @since 1.28
	 */
	public function closeAll() {
		$this->forEachLBCallMethod( 'closeAll', [] );
	}

}

/**
 * Exception class for attempted DB access
 */
class DBAccessError extends MWException {
	public function __construct() {
		parent::__construct( "Mediawiki tried to access the database via wfGetDB(). " .
			"This is not allowed, because database access has been disabled." );
	}
}

/**
 * Exception class for replica DB wait timeouts
 */
class DBReplicationWaitError extends Exception {
}


1		<?php
2		/**
3		* Generator of database load balancing objects.
4		*
5		* This program is free software; you can redistribute it and/or modify
6		* it under the terms of the GNU General Public License as published by
7		* the Free Software Foundation; either version 2 of the License, or
8		* (at your option) any later version.
9		*
10		* This program is distributed in the hope that it will be useful,
11		* but WITHOUT ANY WARRANTY; without even the implied warranty of
12		* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13		* GNU General Public License for more details.
14		*
15		* You should have received a copy of the GNU General Public License along
16		* with this program; if not, write to the Free Software Foundation, Inc.,
17		* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
18		* http://www.gnu.org/copyleft/gpl.html
19		*
20		* @file
21		* @ingroup Database
22		*/
23
24		use MediaWiki\MediaWikiServices;
25		use MediaWiki\Services\DestructibleService;
26		use Psr\Log\LoggerInterface;
27		use MediaWiki\Logger\LoggerFactory;
28
29		/**
30		* An interface for generating database load balancers
31		* @ingroup Database
32		*/
33		abstract class LBFactory implements DestructibleService {
34		/** @var ChronologyProtector */
35		protected $chronProt;
36		/** @var TransactionProfiler */
37		protected $trxProfiler;
38		/** @var LoggerInterface */
39		protected $trxLogger;
40		/** @var BagOStuff */
41		protected $srvCache;
42		/** @var WANObjectCache */
43		protected $wanCache;
44
45		/** @var string\|bool Reason all LBs are read-only or false if not */
46		protected $readOnlyReason = false;
47
48		const SHUTDOWN_NO_CHRONPROT = 1; // don't save ChronologyProtector positions (for async code)
49
50		/**
51		* Construct a factory based on a configuration array (typically from $wgLBFactoryConf)
52		* @param array $conf
53		* @TODO: inject objects via dependency framework
54		*/
55		public function __construct( array $conf ) {
56	View Code Duplication	if ( isset( $conf['readOnlyReason'] ) && is_string( $conf['readOnlyReason'] ) ) {
57		$this->readOnlyReason = $conf['readOnlyReason'];
58		}
59		$this->chronProt = $this->newChronologyProtector();
60		$this->trxProfiler = Profiler::instance()->getTransactionProfiler();
61		// Use APC/memcached style caching, but avoids loops with CACHE_DB (T141804)
62		$cache = ObjectCache::getLocalServerInstance();
63		if ( $cache->getQoS( $cache::ATTR_EMULATION ) > $cache::QOS_EMULATION_SQL ) {
64		$this->srvCache = $cache;
65		} else {
66		$this->srvCache = new EmptyBagOStuff();
67		}
68		$wCache = ObjectCache::getMainWANInstance();
69		if ( $wCache->getQoS( $wCache::ATTR_EMULATION ) > $wCache::QOS_EMULATION_SQL ) {
70		$this->wanCache = $wCache;
71		} else {
72		$this->wanCache = WANObjectCache::newEmpty();
73		}
74		$this->trxLogger = LoggerFactory::getInstance( 'DBTransaction' );
75		}
76
77		/**
78		* Disables all load balancers. All connections are closed, and any attempt to
79		* open a new connection will result in a DBAccessError.
80		* @see LoadBalancer::disable()
81		*/
82		public function destroy() {
83		$this->shutdown();
84		$this->forEachLBCallMethod( 'disable' );
85		}
86
87		/**
88		* Disables all access to the load balancer, will cause all database access
89		* to throw a DBAccessError
90		*/
91		public static function disableBackend() {
92		MediaWikiServices::disableStorageBackend();
93		}
94
95		/**
96		* Get an LBFactory instance
97		*
98		* @deprecated since 1.27, use MediaWikiServices::getDBLoadBalancerFactory() instead.
99		*
100		* @return LBFactory
101		*/
102		public static function singleton() {
103		return MediaWikiServices::getInstance()->getDBLoadBalancerFactory();
104		}
105
106		/**
107		* Returns the LBFactory class to use and the load balancer configuration.
108		*
109		* @todo instead of this, use a ServiceContainer for managing the different implementations.
110		*
111		* @param array $config (e.g. $wgLBFactoryConf)
112		* @return string Class name
113		*/
114		public static function getLBFactoryClass( array $config ) {
115		// For configuration backward compatibility after removing
116		// underscores from class names in MediaWiki 1.23.
117		$bcClasses = [
118		'LBFactory_Simple' => 'LBFactorySimple',
119		'LBFactory_Single' => 'LBFactorySingle',
120		'LBFactory_Multi' => 'LBFactoryMulti',
121		'LBFactory_Fake' => 'LBFactoryFake',
122		];
123
124		$class = $config['class'];
125
126		if ( isset( $bcClasses[$class] ) ) {
127		$class = $bcClasses[$class];
128		wfDeprecated(
129		'$wgLBFactoryConf must be updated. See RELEASE-NOTES for details',
130		'1.23'
131		);
132		}
133
134		return $class;
135		}
136
137		/**
138		* Shut down, close connections and destroy the cached instance.
139		*
140		* @deprecated since 1.27, use LBFactory::destroy()
141		*/
142		public static function destroyInstance() {
143		self::singleton()->destroy();
144		}
145
146		/**
147		* Create a new load balancer object. The resulting object will be untracked,
148		* not chronology-protected, and the caller is responsible for cleaning it up.
149		*
150		* @param bool\|string $wiki Wiki ID, or false for the current wiki
151		* @return LoadBalancer
152		*/
153		abstract public function newMainLB( $wiki = false );
154
155		/**
156		* Get a cached (tracked) load balancer object.
157		*
158		* @param bool\|string $wiki Wiki ID, or false for the current wiki
159		* @return LoadBalancer
160		*/
161		abstract public function getMainLB( $wiki = false );
162
163		/**
164		* Create a new load balancer for external storage. The resulting object will be
165		* untracked, not chronology-protected, and the caller is responsible for
166		* cleaning it up.
167		*
168		* @param string $cluster External storage cluster, or false for core
169		* @param bool\|string $wiki Wiki ID, or false for the current wiki
170		* @return LoadBalancer
171		*/
172		abstract protected function newExternalLB( $cluster, $wiki = false );
173
174		/**
175		* Get a cached (tracked) load balancer for external storage
176		*
177		* @param string $cluster External storage cluster, or false for core
178		* @param bool\|string $wiki Wiki ID, or false for the current wiki
179		* @return LoadBalancer
180		*/
181		abstract public function &getExternalLB( $cluster, $wiki = false );
182
183		/**
184		* Execute a function for each tracked load balancer
185		* The callback is called with the load balancer as the first parameter,
186		* and $params passed as the subsequent parameters.
187		*
188		* @param callable $callback
189		* @param array $params
190		*/
191		abstract public function forEachLB( $callback, array $params = [] );
192
193		/**
194		* Prepare all tracked load balancers for shutdown
195		* @param integer $flags Supports SHUTDOWN_* flags
196		* STUB
197		*/
198		public function shutdown( $flags = 0 ) {
199		}
200
201		/**
202		* Call a method of each tracked load balancer
203		*
204		* @param string $methodName
205		* @param array $args
206		*/
207		private function forEachLBCallMethod( $methodName, array $args = [] ) {
208		$this->forEachLB(
209		function ( LoadBalancer $loadBalancer, $methodName, array $args ) {
210		call_user_func_array( [ $loadBalancer, $methodName ], $args );
211		},
212		[ $methodName, $args ]
213		);
214		}
215
216		/**
217		* Commit on all connections. Done for two reasons:
218		* 1. To commit changes to the masters.
219		* 2. To release the snapshot on all connections, master and slave.
220		* @param string $fname Caller name
221		* @param array $options Options map:
222		* - maxWriteDuration: abort if more than this much time was spent in write queries
223		*/
224		public function commitAll( $fname = __METHOD__, array $options = [] ) {
225		$this->commitMasterChanges( $fname, $options );
226		$this->forEachLBCallMethod( 'commitAll', [ $fname ] );
227		}
228
229		/**
230		* Commit changes on all master connections
231		* @param string $fname Caller name
232		* @param array $options Options map:
233		* - maxWriteDuration: abort if more than this much time was spent in write queries
234		*/
235		public function commitMasterChanges( $fname = __METHOD__, array $options = [] ) {
236		// Perform all pre-commit callbacks, aborting on failure
237		$this->forEachLBCallMethod( 'runMasterPreCommitCallbacks' );
238		// Perform all pre-commit checks, aborting on failure
239		$this->forEachLBCallMethod( 'approveMasterChanges', [ $options ] );
240		// Log the DBs and methods involved in multi-DB transactions
241		$this->logIfMultiDbTransaction();
242		// Actually perform the commit on all master DB connections
243		$this->forEachLBCallMethod( 'commitMasterChanges', [ $fname ] );
244		// Run all post-commit callbacks
245		$this->forEachLBCallMethod( 'runMasterPostCommitCallbacks' );
246		// Commit any dangling DBO_TRX transactions from callbacks on one DB to another DB
247		$this->forEachLBCallMethod( 'commitMasterChanges', [ $fname ] );
248		}
249
250		/**
251		* Rollback changes on all master connections
252		* @param string $fname Caller name
253		* @since 1.23
254		*/
255		public function rollbackMasterChanges( $fname = __METHOD__ ) {
256		$this->forEachLBCallMethod( 'rollbackMasterChanges', [ $fname ] );
257		}
258
259		/**
260		* Log query info if multi DB transactions are going to be committed now
261		*/
262		private function logIfMultiDbTransaction() {
263		$callersByDB = [];
264		$this->forEachLB( function ( LoadBalancer $lb ) use ( &$callersByDB ) {
265		$masterName = $lb->getServerName( $lb->getWriterIndex() );
266		$callers = $lb->pendingMasterChangeCallers();
267		if ( $callers ) {
268		$callersByDB[$masterName] = $callers;
269		}
270		} );
271
272		if ( count( $callersByDB ) >= 2 ) {
273		$dbs = implode( ', ', array_keys( $callersByDB ) );
274		$msg = "Multi-DB transaction [{$dbs}]:\n";
275		foreach ( $callersByDB as $db => $callers ) {
276		$msg .= "$db: " . implode( '; ', $callers ) . "\n";
277		}
278		$this->trxLogger->info( $msg );
279		}
280		}
281
282		/**
283		* Determine if any master connection has pending changes
284		* @return bool
285		* @since 1.23
286		*/
287		public function hasMasterChanges() {
288		$ret = false;
289		$this->forEachLB( function ( LoadBalancer $lb ) use ( &$ret ) {
290		$ret = $ret \|\| $lb->hasMasterChanges();
291		} );
292
293		return $ret;
294		}
295
296		/**
297		* Detemine if any lagged slave connection was used
298		* @since 1.27
299		* @return bool
300		*/
301		public function laggedSlaveUsed() {
302		$ret = false;
303		$this->forEachLB( function ( LoadBalancer $lb ) use ( &$ret ) {
304		$ret = $ret \|\| $lb->laggedSlaveUsed();
305		} );
306
307		return $ret;
308		}
309
310		/**
311		* Determine if any master connection has pending/written changes from this request
312		* @return bool
313		* @since 1.27
314		*/
315		public function hasOrMadeRecentMasterChanges() {
316		$ret = false;
317		$this->forEachLB( function ( LoadBalancer $lb ) use ( &$ret ) {
318		$ret = $ret \|\| $lb->hasOrMadeRecentMasterChanges();
319		} );
320		return $ret;
321		}
322
323		/**
324		* Waits for the slave DBs to catch up to the current master position
325		*
326		* Use this when updating very large numbers of rows, as in maintenance scripts,
327		* to avoid causing too much lag. Of course, this is a no-op if there are no slaves.
328		*
329		* By default this waits on all DB clusters actually used in this request.
330		* This makes sense when lag being waiting on is caused by the code that does this check.
331		* In that case, setting "ifWritesSince" can avoid the overhead of waiting for clusters
332		* that were not changed since the last wait check. To forcefully wait on a specific cluster
333		* for a given wiki, use the 'wiki' parameter. To forcefully wait on an "external" cluster,
334		* use the "cluster" parameter.
335		*
336		* Never call this function after a large DB write that is still in a transaction.
337		* It only makes sense to call this after the possible lag inducing changes were committed.
338		*
339		* @param array $opts Optional fields that include:
340		* - wiki : wait on the load balancer DBs that handles the given wiki
341		* - cluster : wait on the given external load balancer DBs
342		* - timeout : Max wait time. Default: ~60 seconds
343		* - ifWritesSince: Only wait if writes were done since this UNIX timestamp
344		* @throws DBReplicationWaitError If a timeout or error occured waiting on a DB cluster
345		* @since 1.27
346		*/
347		public function waitForReplication( array $opts = [] ) {
348		$opts += [
349		'wiki' => false,
350		'cluster' => false,
351		'timeout' => 60,
352		'ifWritesSince' => null
353		];
354
355		// Figure out which clusters need to be checked
356		/** @var LoadBalancer[] $lbs */
357		$lbs = [];
358		if ( $opts['cluster'] !== false ) {
359		$lbs[] = $this->getExternalLB( $opts['cluster'] );
360		} elseif ( $opts['wiki'] !== false ) {
361		$lbs[] = $this->getMainLB( $opts['wiki'] );
362		} else {
363		$this->forEachLB( function ( LoadBalancer $lb ) use ( &$lbs ) {
364		$lbs[] = $lb;
365		} );
366		if ( !$lbs ) {
367		return; // nothing actually used
368		}
369		}
370
371		// Get all the master positions of applicable DBs right now.
372		// This can be faster since waiting on one cluster reduces the
373		// time needed to wait on the next clusters.
374		$masterPositions = array_fill( 0, count( $lbs ), false );
375		foreach ( $lbs as $i => $lb ) {
376		if ( $lb->getServerCount() <= 1 ) {
377		// Bug 27975 - Don't try to wait for slaves if there are none
378		// Prevents permission error when getting master position
379		continue;
380		} elseif ( $opts['ifWritesSince']
381		&& $lb->lastMasterChangeTimestamp() < $opts['ifWritesSince']
382		) {
383		continue; // no writes since the last wait
384		}
385		$masterPositions[$i] = $lb->getMasterPos();
386		}
387
388		$failed = [];
389		foreach ( $lbs as $i => $lb ) {
390		if ( $masterPositions[$i] ) {
391		// The DBMS may not support getMasterPos() or the whole
392		// load balancer might be fake (e.g. $wgAllDBsAreLocalhost).
393		if ( !$lb->waitForAll( $masterPositions[$i], $opts['timeout'] ) ) {
394		$failed[] = $lb->getServerName( $lb->getWriterIndex() );
395		}
396		}
397		}
398
399		if ( $failed ) {
400		throw new DBReplicationWaitError(
401		"Could not wait for slaves to catch up to " .
402		implode( ', ', $failed )
403		);
404		}
405		}
406
407		/**
408		* Disable the ChronologyProtector for all load balancers
409		*
410		* This can be called at the start of special API entry points
411		*
412		* @since 1.27
413		*/
414		public function disableChronologyProtection() {
415		$this->chronProt->setEnabled( false );
416		}
417
418		/**
419		* @return ChronologyProtector
420		*/
421		protected function newChronologyProtector() {
422		$request = RequestContext::getMain()->getRequest();
423		$chronProt = new ChronologyProtector(
424		ObjectCache::getMainStashInstance(),
425		[
426		'ip' => $request->getIP(),
427		'agent' => $request->getHeader( 'User-Agent' )
428		]
429		);
430		if ( PHP_SAPI === 'cli' ) {
431		$chronProt->setEnabled( false );
432		} elseif ( $request->getHeader( 'ChronologyProtection' ) === 'false' ) {
433		// Request opted out of using position wait logic. This is useful for requests
434		// done by the job queue or background ETL that do not have a meaningful session.
435		$chronProt->setWaitEnabled( false );
436		}
437
438		return $chronProt;
439		}
440
441		/**
442		* @param ChronologyProtector $cp
443		*/
444		protected function shutdownChronologyProtector( ChronologyProtector $cp ) {
445		// Get all the master positions needed
446		$this->forEachLB( function ( LoadBalancer $lb ) use ( $cp ) {
447		$cp->shutdownLB( $lb );
448		} );
449		// Write them to the stash
450		$unsavedPositions = $cp->shutdown();
451		// If the positions failed to write to the stash, at least wait on local datacenter
452		// slaves to catch up before responding. Even if there are several DCs, this increases
453		// the chance that the user will see their own changes immediately afterwards. As long
454		// as the sticky DC cookie applies (same domain), this is not even an issue.
455		$this->forEachLB( function ( LoadBalancer $lb ) use ( $unsavedPositions ) {
456		$masterName = $lb->getServerName( $lb->getWriterIndex() );
457		if ( isset( $unsavedPositions[$masterName] ) ) {
458		$lb->waitForAll( $unsavedPositions[$masterName] );
459		}
460		} );
461		}
462
463		/**
464		* Close all open database connections on all open load balancers.
465		* @since 1.28
466		*/
467		public function closeAll() {
468		$this->forEachLBCallMethod( 'closeAll', [] );
469		}
470
471		}
472
473		/**
474		* Exception class for attempted DB access
475		*/
476		class DBAccessError extends MWException {
477		public function __construct() {
478		parent::__construct( "Mediawiki tried to access the database via wfGetDB(). " .
479		"This is not allowed, because database access has been disabled." );
480		}
481		}
482
483		/**
484		* Exception class for replica DB wait timeouts
485		*/
486		class DBReplicationWaitError extends Exception {
487		}
488

wikimedia / mediawiki

Branch — master (bbf110)

LBFactory::singleton() A

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