LBFactory::hasMasterChanges() - Code Metrics - Inspection of "Daily Inspection: Merge "Adding support for numeri..." - wikimedia/mediawiki - Measure and Improve Code Quality continuously with Scrutinizer

Completed

Branch — master (420c52)

unknown

created 2016-07-27 17:20 UTC

LBFactory::hasMasterChanges() A

↳ Parent: LBFactory

Complexity

Conditions	2
Paths	1

Size

Total Lines	8
Code Lines	5

Duplication

Lines	0
Ratio	0 %

Importance

Changes

Metric	Value
cc	2
eloc	5
nc	1
nop	0
dl	0
loc	8
rs	9.4285
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 $logger;

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

wikimedia / mediawiki

Branch — master (420c52)

LBFactory::hasMasterChanges() A

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