/includes/db/loadbalancer/LBFactory.php
PHP | 481 lines | 228 code | 51 blank | 202 comment | 24 complexity | 742794129010404271a071a1ffd7c26e MD5 | raw file
- <?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 Psr\Log\LoggerInterface;
- use MediaWiki\Logger\LoggerFactory;
- /**
- * An interface for generating database load balancers
- * @ingroup Database
- */
- abstract class LBFactory {
- /** @var ChronologyProtector */
- protected $chronProt;
- /** @var TransactionProfiler */
- protected $trxProfiler;
- /** @var LoggerInterface */
- protected $logger;
- /** @var LBFactory */
- private static $instance;
- /** @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 access to the load balancer, will cause all database access
- * to throw a DBAccessError
- */
- public static function disableBackend() {
- global $wgLBFactoryConf;
- self::$instance = new LBFactoryFake( $wgLBFactoryConf );
- }
- /**
- * Get an LBFactory instance
- *
- * @return LBFactory
- */
- public static function singleton() {
- global $wgLBFactoryConf;
- if ( is_null( self::$instance ) ) {
- $class = self::getLBFactoryClass( $wgLBFactoryConf );
- $config = $wgLBFactoryConf;
- if ( !isset( $config['readOnlyReason'] ) ) {
- $config['readOnlyReason'] = wfConfiguredReadOnlyReason();
- }
- self::$instance = new $class( $config );
- }
- return self::$instance;
- }
- /**
- * Returns the LBFactory class to use and the load balancer configuration.
- *
- * @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 $class;
- }
- /**
- * Shut down, close connections and destroy the cached instance.
- */
- public static function destroyInstance() {
- if ( self::$instance ) {
- self::$instance->shutdown();
- self::$instance->forEachLBCallMethod( 'closeAll' );
- self::$instance = null;
- }
- }
- /**
- * Set the instance to be the given object
- *
- * @param LBFactory $instance
- */
- public static function setInstance( $instance ) {
- self::destroyInstance();
- self::$instance = $instance;
- }
- /**
- * 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
- */
- public function commitAll( $fname = __METHOD__ ) {
- $this->logMultiDbTransaction();
- $start = microtime( true );
- $this->forEachLBCallMethod( 'commitAll', [ $fname ] );
- $timeMs = 1000 * ( microtime( true ) - $start );
- RequestContext::getMain()->getStats()->timing( "db.commit-all", $timeMs );
- }
- /**
- * 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 = [] ) {
- $limit = isset( $options['maxWriteDuration'] ) ? $options['maxWriteDuration'] : 0;
- $this->logMultiDbTransaction();
- $this->forEachLB( function ( LoadBalancer $lb ) use ( $limit ) {
- $lb->forEachOpenConnection( function ( IDatabase $db ) use ( $limit ) {
- $time = $db->pendingWriteQueryDuration();
- if ( $limit > 0 && $time > $limit ) {
- throw new DBTransactionError(
- $db,
- wfMessage( 'transaction-duration-limit-exceeded', $time, $limit )->text()
- );
- }
- } );
- } );
- $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 logMultiDbTransaction() {
- $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] );
- }
- } );
- }
- }
- /**
- * 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." );
- }
- }
- /**
- * Exception class for replica DB wait timeouts
- */
- class DBReplicationWaitError extends Exception {
- }