LBFactory.php

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<?php
namespace Wikimedia\Rdbms;
 
use Psr\Log\LoggerInterface;
use Wikimedia\ScopedCallback;
use BagOStuff;
use EmptyBagOStuff;
use WANObjectCache;
use Exception;
use RuntimeException;
 
abstract class LBFactory implements ILBFactory {
    protected $chronProt;
    protected $profiler;
    protected $trxProfiler;
    protected $replLogger;
    protected $connLogger;
    protected $queryLogger;
    protected $perfLogger;
    protected $errorLogger;
    protected $srvCache;
    protected $memStash;
    protected $wanCache;
 
    protected $localDomain;
    protected $hostname;
    protected $requestInfo;
 
    protected $ticket;
    protected $trxRoundId = false;
    protected $readOnlyReason = false;
    protected $replicationWaitCallbacks = [];
 
    protected $cliMode;
    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->memStash = isset( $conf['memStash'] ) ? $conf['memStash'] : 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( $conf['profiler'] ) ? $conf['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( $conf['cliMode'] ) ? $conf['cliMode'] : PHP_SAPI === 'cli';
        $this->hostname = isset( $conf['hostname'] ) ? $conf['hostname'] : gethostname();
        $this->agent = isset( $conf['agent'] ) ? $conf['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
    }
 
    abstract public function newMainLB( $domain = false );
 
    abstract public function getMainLB( $domain = false );
 
    abstract public function newExternalLB( $cluster );
 
    abstract public function getExternalLB( $cluster );
 
    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."
            );
        }
        $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
        $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 );
        } );
    }
 
    public function hasTransactionRound() {
        return ( $this->trxRoundId !== false );
    }
 
    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
        $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 ) {
                // T29975 - 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 );
    }
 
    protected function getChronologyProtector() {
        if ( $this->chronProt ) {
            return $this->chronProt;
        }
 
        $this->chronProt = new ChronologyProtector(
            $this->memStash,
            [
                '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;
    }
 
    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] );
            }
        } );
    }
 
    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,
            'chronologyProtector' => $this->getChronologyProtector()
        ];
    }
 
    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;
    }
 
    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();
    }
}
 
class_alias( LBFactory::class, 'LBFactory' );