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[mediawiki.git] / includes / libs / rdbms / lbfactory / LBFactory.php

<?php
/**
 * Generator and manager 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 Wikimedia\ScopedCallback;

/**
 * An interface for generating database load balancers
 * @ingroup Database
 */
abstract class LBFactory implements ILBFactory {
        /** @var ChronologyProtector */
        protected $chronProt;
        /** @var object|string Class name or object With profileIn/profileOut methods */
        protected $profiler;
        /** @var TransactionProfiler */
        protected $trxProfiler;
        /** @var LoggerInterface */
        protected $replLogger;
        /** @var LoggerInterface */
        protected $connLogger;
        /** @var LoggerInterface */
        protected $queryLogger;
        /** @var LoggerInterface */
        protected $perfLogger;
        /** @var callable Error logger */
        protected $errorLogger;
        /** @var BagOStuff */
        protected $srvCache;
        /** @var BagOStuff */
        protected $memCache;
        /** @var WANObjectCache */
        protected $wanCache;

        /** @var DatabaseDomain Local domain */
        protected $localDomain;
        /** @var string Local hostname of the app server */
        protected $hostname;
        /** @var array Web request information about the client */
        protected $requestInfo;

        /** @var mixed */
        protected $ticket;
        /** @var string|bool String if a requested DBO_TRX transaction round is active */
        protected $trxRoundId = false;
        /** @var string|bool Reason all LBs are read-only or false if not */
        protected $readOnlyReason = false;
        /** @var callable[] */
        protected $replicationWaitCallbacks = [];

        /** @var bool Whether this PHP instance is for a CLI script */
        protected $cliMode;
        /** @var string Agent name for query profiling */
        protected $agent;

        private static $loggerFields =
                [ 'replLogger', 'connLogger', 'queryLogger', 'perfLogger' ];

        public function __construct( array $conf ) {
                $this->localDomain = isset( $conf['localDomain'] )
                        ? DatabaseDomain::newFromId( $conf['localDomain'] )
                        : DatabaseDomain::newUnspecified();

                if ( isset( $conf['readOnlyReason'] ) && is_string( $conf['readOnlyReason'] ) ) {
                        $this->readOnlyReason = $conf['readOnlyReason'];
                }

                $this->srvCache = isset( $conf['srvCache'] ) ? $conf['srvCache'] : new EmptyBagOStuff();
                $this->memCache = isset( $conf['memCache'] ) ? $conf['memCache'] : new EmptyBagOStuff();
                $this->wanCache = isset( $conf['wanCache'] )
                        ? $conf['wanCache']
                        : WANObjectCache::newEmpty();

                foreach ( self::$loggerFields as $key ) {
                        $this->$key = isset( $conf[$key] ) ? $conf[$key] : new \Psr\Log\NullLogger();
                }
                $this->errorLogger = isset( $conf['errorLogger'] )
                        ? $conf['errorLogger']
                        : function ( Exception $e ) {
                                trigger_error( E_USER_WARNING, get_class( $e ) . ': ' . $e->getMessage() );
                        };

                $this->profiler = isset( $params['profiler'] ) ? $params['profiler'] : null;
                $this->trxProfiler = isset( $conf['trxProfiler'] )
                        ? $conf['trxProfiler']
                        : new TransactionProfiler();

                $this->requestInfo = [
                        'IPAddress' => isset( $_SERVER[ 'REMOTE_ADDR' ] ) ? $_SERVER[ 'REMOTE_ADDR' ] : '',
                        'UserAgent' => isset( $_SERVER['HTTP_USER_AGENT'] ) ? $_SERVER['HTTP_USER_AGENT'] : '',
                        'ChronologyProtection' => 'true'
                ];

                $this->cliMode = isset( $params['cliMode'] ) ? $params['cliMode'] : PHP_SAPI === 'cli';
                $this->hostname = isset( $conf['hostname'] ) ? $conf['hostname'] : gethostname();
                $this->agent = isset( $params['agent'] ) ? $params['agent'] : '';

                $this->ticket = mt_rand();
        }

        public function destroy() {
                $this->shutdown( self::SHUTDOWN_NO_CHRONPROT );
                $this->forEachLBCallMethod( 'disable' );
        }

        public function shutdown(
                $mode = self::SHUTDOWN_CHRONPROT_SYNC, callable $workCallback = null
        ) {
                $chronProt = $this->getChronologyProtector();
                if ( $mode === self::SHUTDOWN_CHRONPROT_SYNC ) {
                        $this->shutdownChronologyProtector( $chronProt, $workCallback, 'sync' );
                } elseif ( $mode === self::SHUTDOWN_CHRONPROT_ASYNC ) {
                        $this->shutdownChronologyProtector( $chronProt, null, 'async' );
                }

                $this->commitMasterChanges( __METHOD__ ); // sanity
        }

        /**
         * @see ILBFactory::newMainLB()
         * @param bool $domain
         * @return LoadBalancer
         */
        abstract public function newMainLB( $domain = false );

        /**
         * @see ILBFactory::getMainLB()
         * @param bool $domain
         * @return LoadBalancer
         */
        abstract public function getMainLB( $domain = false );

        /**
         * @see ILBFactory::newExternalLB()
         * @param string $cluster
         * @return LoadBalancer
         */
        abstract public function newExternalLB( $cluster );

        /**
         * @see ILBFactory::getExternalLB()
         * @param string $cluster
         * @return LoadBalancer
         */
        abstract public function getExternalLB( $cluster );

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

        public function flushReplicaSnapshots( $fname = __METHOD__ ) {
                $this->forEachLBCallMethod( 'flushReplicaSnapshots', [ $fname ] );
        }

        public function commitAll( $fname = __METHOD__, array $options = [] ) {
                $this->commitMasterChanges( $fname, $options );
                $this->forEachLBCallMethod( 'commitAll', [ $fname ] );
        }

        public function beginMasterChanges( $fname = __METHOD__ ) {
                if ( $this->trxRoundId !== false ) {
                        throw new DBTransactionError(
                                null,
                                "$fname: transaction round '{$this->trxRoundId}' already started."
                        );
                }
                $this->trxRoundId = $fname;
                // Set DBO_TRX flags on all appropriate DBs
                $this->forEachLBCallMethod( 'beginMasterChanges', [ $fname ] );
        }

        public function commitMasterChanges( $fname = __METHOD__, array $options = [] ) {
                if ( $this->trxRoundId !== false && $this->trxRoundId !== $fname ) {
                        throw new DBTransactionError(
                                null,
                                "$fname: transaction round '{$this->trxRoundId}' still running."
                        );
                }
                /** @noinspection PhpUnusedLocalVariableInspection */
                $scope = $this->getScopedPHPBehaviorForCommit(); // try to ignore client aborts
                // Run pre-commit callbacks and suppress post-commit callbacks, aborting on failure
                $this->forEachLBCallMethod( 'finalizeMasterChanges' );
                $this->trxRoundId = false;
                // Perform 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 and revert DBO_TRX
                $this->forEachLBCallMethod( 'commitMasterChanges', [ $fname ] );
                // Run all post-commit callbacks
                /** @var Exception $e */
                $e = null; // first callback exception
                $this->forEachLB( function ( ILoadBalancer $lb ) use ( &$e ) {
                        $ex = $lb->runMasterPostTrxCallbacks( IDatabase::TRIGGER_COMMIT );
                        $e = $e ?: $ex;
                } );
                // Commit any dangling DBO_TRX transactions from callbacks on one DB to another DB
                $this->forEachLBCallMethod( 'commitMasterChanges', [ $fname ] );
                // Throw any last post-commit callback error
                if ( $e instanceof Exception ) {
                        throw $e;
                }
        }

        public function rollbackMasterChanges( $fname = __METHOD__ ) {
                $this->trxRoundId = false;
                $this->forEachLBCallMethod( 'suppressTransactionEndCallbacks' );
                $this->forEachLBCallMethod( 'rollbackMasterChanges', [ $fname ] );
                // Run all post-rollback callbacks
                $this->forEachLB( function ( ILoadBalancer $lb ) {
                        $lb->runMasterPostTrxCallbacks( IDatabase::TRIGGER_ROLLBACK );
                } );
        }

        /**
         * Log query info if multi DB transactions are going to be committed now
         */
        private function logIfMultiDbTransaction() {
                $callersByDB = [];
                $this->forEachLB( function ( ILoadBalancer $lb ) use ( &$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->queryLogger->info( $msg );
                }
        }

        public function hasMasterChanges() {
                $ret = false;
                $this->forEachLB( function ( ILoadBalancer $lb ) use ( &$ret ) {
                        $ret = $ret || $lb->hasMasterChanges();
                } );

                return $ret;
        }

        public function laggedReplicaUsed() {
                $ret = false;
                $this->forEachLB( function ( ILoadBalancer $lb ) use ( &$ret ) {
                        $ret = $ret || $lb->laggedReplicaUsed();
                } );

                return $ret;
        }

        public function hasOrMadeRecentMasterChanges( $age = null ) {
                $ret = false;
                $this->forEachLB( function ( ILoadBalancer $lb ) use ( $age, &$ret ) {
                        $ret = $ret || $lb->hasOrMadeRecentMasterChanges( $age );
                } );
                return $ret;
        }

        public function waitForReplication( array $opts = [] ) {
                $opts += [
                        'domain' => false,
                        'cluster' => false,
                        'timeout' => 60,
                        'ifWritesSince' => null
                ];

                if ( $opts['domain'] === false && isset( $opts['wiki'] ) ) {
                        $opts['domain'] = $opts['wiki']; // b/c
                }

                // Figure out which clusters need to be checked
                /** @var ILoadBalancer[] $lbs */
                $lbs = [];
                if ( $opts['cluster'] !== false ) {
                        $lbs[] = $this->getExternalLB( $opts['cluster'] );
                } elseif ( $opts['domain'] !== false ) {
                        $lbs[] = $this->getMainLB( $opts['domain'] );
                } else {
                        $this->forEachLB( function ( ILoadBalancer $lb ) use ( &$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 replica DBs 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();
                }

                // Run any listener callbacks *after* getting the DB positions. The more
                // time spent in the callbacks, the less time is spent in waitForAll().
                foreach ( $this->replicationWaitCallbacks as $callback ) {
                        $callback();
                }

                $failed = [];
                foreach ( $lbs as $i => $lb ) {
                        if ( $masterPositions[$i] ) {
                                // The DBMS may not support getMasterPos()
                                if ( !$lb->waitForAll( $masterPositions[$i], $opts['timeout'] ) ) {
                                        $failed[] = $lb->getServerName( $lb->getWriterIndex() );
                                }
                        }
                }

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

        public function setWaitForReplicationListener( $name, callable $callback = null ) {
                if ( $callback ) {
                        $this->replicationWaitCallbacks[$name] = $callback;
                } else {
                        unset( $this->replicationWaitCallbacks[$name] );
                }
        }

        public function getEmptyTransactionTicket( $fname ) {
                if ( $this->hasMasterChanges() ) {
                        $this->queryLogger->error( __METHOD__ . ": $fname does not have outer scope.\n" .
                                ( new RuntimeException() )->getTraceAsString() );

                        return null;
                }

                return $this->ticket;
        }

        public function commitAndWaitForReplication( $fname, $ticket, array $opts = [] ) {
                if ( $ticket !== $this->ticket ) {
                        $this->perfLogger->error( __METHOD__ . ": $fname does not have outer scope.\n" .
                                ( new RuntimeException() )->getTraceAsString() );

                        return;
                }

                // The transaction owner and any caller with the empty transaction ticket can commit
                // so that getEmptyTransactionTicket() callers don't risk seeing DBTransactionError.
                if ( $this->trxRoundId !== false && $fname !== $this->trxRoundId ) {
                        $this->queryLogger->info( "$fname: committing on behalf of {$this->trxRoundId}." );
                        $fnameEffective = $this->trxRoundId;
                } else {
                        $fnameEffective = $fname;
                }

                $this->commitMasterChanges( $fnameEffective );
                $this->waitForReplication( $opts );
                // If a nested caller committed on behalf of $fname, start another empty $fname
                // transaction, leaving the caller with the same empty transaction state as before.
                if ( $fnameEffective !== $fname ) {
                        $this->beginMasterChanges( $fnameEffective );
                }
        }

        public function getChronologyProtectorTouched( $dbName ) {
                return $this->getChronologyProtector()->getTouched( $dbName );
        }

        public function disableChronologyProtection() {
                $this->getChronologyProtector()->setEnabled( false );
        }

        /**
         * @return ChronologyProtector
         */
        protected function getChronologyProtector() {
                if ( $this->chronProt ) {
                        return $this->chronProt;
                }

                $this->chronProt = new ChronologyProtector(
                        $this->memCache,
                        [
                                'ip' => $this->requestInfo['IPAddress'],
                                'agent' => $this->requestInfo['UserAgent'],
                        ],
                        isset( $_GET['cpPosTime'] ) ? $_GET['cpPosTime'] : null
                );
                $this->chronProt->setLogger( $this->replLogger );

                if ( $this->cliMode ) {
                        $this->chronProt->setEnabled( false );
                } elseif ( $this->requestInfo['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.
                        $this->chronProt->setWaitEnabled( false );
                }

                $this->replLogger->debug( __METHOD__ . ': using request info ' .
                        json_encode( $this->requestInfo, JSON_PRETTY_PRINT ) );

                return $this->chronProt;
        }

        /**
         * Get and record all of the staged DB positions into persistent memory storage
         *
         * @param ChronologyProtector $cp
         * @param callable|null $workCallback Work to do instead of waiting on syncing positions
         * @param string $mode One of (sync, async); whether to wait on remote datacenters
         */
        protected function shutdownChronologyProtector(
                ChronologyProtector $cp, $workCallback, $mode
        ) {
                // Record all the master positions needed
                $this->forEachLB( function ( ILoadBalancer $lb ) use ( $cp ) {
                        $cp->shutdownLB( $lb );
                } );
                // Write them to the persistent stash. Try to do something useful by running $work
                // while ChronologyProtector waits for the stash write to replicate to all DCs.
                $unsavedPositions = $cp->shutdown( $workCallback, $mode );
                if ( $unsavedPositions && $workCallback ) {
                        // Invoke callback in case it did not cache the result yet
                        $workCallback(); // work now to block for less time in waitForAll()
                }
                // If the positions failed to write to the stash, at least wait on local datacenter
                // replica DBs 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 ( ILoadBalancer $lb ) use ( $unsavedPositions ) {
                        $masterName = $lb->getServerName( $lb->getWriterIndex() );
                        if ( isset( $unsavedPositions[$masterName] ) ) {
                                $lb->waitForAll( $unsavedPositions[$masterName] );
                        }
                } );
        }

        /**
         * Base parameters to LoadBalancer::__construct()
         * @return array
         */
        final protected function baseLoadBalancerParams() {
                return [
                        'localDomain' => $this->localDomain,
                        'readOnlyReason' => $this->readOnlyReason,
                        'srvCache' => $this->srvCache,
                        'wanCache' => $this->wanCache,
                        'profiler' => $this->profiler,
                        'trxProfiler' => $this->trxProfiler,
                        'queryLogger' => $this->queryLogger,
                        'connLogger' => $this->connLogger,
                        'replLogger' => $this->replLogger,
                        'errorLogger' => $this->errorLogger,
                        'hostname' => $this->hostname,
                        'cliMode' => $this->cliMode,
                        'agent' => $this->agent
                ];
        }

        /**
         * @param ILoadBalancer $lb
         */
        protected function initLoadBalancer( ILoadBalancer $lb ) {
                if ( $this->trxRoundId !== false ) {
                        $lb->beginMasterChanges( $this->trxRoundId ); // set DBO_TRX
                }
        }

        public function setDomainPrefix( $prefix ) {
                $this->localDomain = new DatabaseDomain(
                        $this->localDomain->getDatabase(),
                        null,
                        $prefix
                );

                $this->forEachLB( function( ILoadBalancer $lb ) use ( $prefix ) {
                        $lb->setDomainPrefix( $prefix );
                } );
        }

        public function closeAll() {
                $this->forEachLBCallMethod( 'closeAll', [] );
        }

        public function setAgentName( $agent ) {
                $this->agent = $agent;
        }

        public function appendPreShutdownTimeAsQuery( $url, $time ) {
                $usedCluster = 0;
                $this->forEachLB( function ( ILoadBalancer $lb ) use ( &$usedCluster ) {
                        $usedCluster |= ( $lb->getServerCount() > 1 );
                } );

                if ( !$usedCluster ) {
                        return $url; // no master/replica clusters touched
                }

                return strpos( $url, '?' ) === false ? "$url?cpPosTime=$time" : "$url&cpPosTime=$time";
        }

        public function setRequestInfo( array $info ) {
                $this->requestInfo = $info + $this->requestInfo;
        }

        /**
         * Make PHP ignore user aborts/disconnects until the returned
         * value leaves scope. This returns null and does nothing in CLI mode.
         *
         * @return ScopedCallback|null
         */
        final protected function getScopedPHPBehaviorForCommit() {
                if ( PHP_SAPI != 'cli' ) { // https://bugs.php.net/bug.php?id=47540
                        $old = ignore_user_abort( true ); // avoid half-finished operations
                        return new ScopedCallback( function () use ( $old ) {
                                ignore_user_abort( $old );
                        } );
                }

                return null;
        }

        function __destruct() {
                $this->destroy();
        }
}