Merge ".mailmap: Correct two contributor names"

[mediawiki.git] / includes / externalstore / ExternalStoreDB.php

<?php
/**
 * 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
 */

use Wikimedia\Rdbms\DatabaseDomain;
use Wikimedia\Rdbms\DBUnexpectedError;
use Wikimedia\Rdbms\ILoadBalancer;
use Wikimedia\Rdbms\LBFactory;
use Wikimedia\Rdbms\Query;
use Wikimedia\Rdbms\ServerInfo;
use Wikimedia\ScopedCallback;

/**
 * External storage in a SQL database.
 *
 * In this system, each store "location" maps to a database "cluster".
 * The clusters must be defined in the normal LBFactory configuration.
 *
 * @see ExternalStoreAccess
 * @ingroup ExternalStorage
 */
class ExternalStoreDB extends ExternalStoreMedium {
        /** @var LBFactory */
        private $lbFactory;

        /**
         * @see ExternalStoreMedium::__construct()
         * @param array $params Additional parameters include:
         *   - lbFactory: an LBFactory instance
         */
        public function __construct( array $params ) {
                parent::__construct( $params );
                if ( !isset( $params['lbFactory'] ) || !( $params['lbFactory'] instanceof LBFactory ) ) {
                        throw new InvalidArgumentException( "LBFactory required in 'lbFactory' field." );
                }
                $this->lbFactory = $params['lbFactory'];
        }

        /**
         * Fetch data from given external store URL.
         *
         * The provided URL is in the form of `DB://cluster/id` or `DB://cluster/id/itemid`
         * for concatenated storage if ConcatenatedGzipHistoryBlob was used.
         *
         * @param string $url
         * @return string|false False if missing
         * @see ExternalStoreMedium::fetchFromURL()
         */
        public function fetchFromURL( $url ) {
                [ $cluster, $id, $itemID ] = $this->parseURL( $url );
                $ret = $this->fetchBlob( $cluster, $id, $itemID );

                if ( $itemID !== false && $ret !== false ) {
                        return $ret->getItem( $itemID );
                }

                return $ret;
        }

        /**
         * Fetch multiple URLs from given external store.
         *
         * The provided URLs are in the form of `DB://cluster/id`, or `DB://cluster/id/itemid`
         * for concatenated storage if ConcatenatedGzipHistoryBlob was used.
         *
         * @param array $urls An array of external store URLs
         * @return array A map from url to stored content. Failed results
         *     are not represented.
         */
        public function batchFetchFromURLs( array $urls ) {
                $batched = $inverseUrlMap = [];
                foreach ( $urls as $url ) {
                        [ $cluster, $id, $itemID ] = $this->parseURL( $url );
                        $batched[$cluster][$id][] = $itemID;
                        // false $itemID gets cast to int, but should be ok
                        // since we do === from the $itemID in $batched
                        $inverseUrlMap[$cluster][$id][$itemID] = $url;
                }
                $ret = [];
                foreach ( $batched as $cluster => $batchByCluster ) {
                        $res = $this->batchFetchBlobs( $cluster, $batchByCluster );
                        /** @var HistoryBlob $blob */
                        foreach ( $res as $id => $blob ) {
                                foreach ( $batchByCluster[$id] as $itemID ) {
                                        $url = $inverseUrlMap[$cluster][$id][$itemID];
                                        if ( $itemID === false ) {
                                                $ret[$url] = $blob;
                                        } else {
                                                $ret[$url] = $blob->getItem( $itemID );
                                        }
                                }
                        }
                }

                return $ret;
        }

        /**
         * @inheritDoc
         */
        public function store( $location, $data ) {
                $blobsTable = $this->getTable( $location );

                $dbw = $this->getPrimary( $location );
                $dbw->newInsertQueryBuilder()
                        ->insertInto( $blobsTable )
                        ->row( [ 'blob_text' => $data ] )
                        ->caller( __METHOD__ )->execute();

                $id = $dbw->insertId();
                if ( !$id ) {
                        throw new ExternalStoreException( __METHOD__ . ': no insert ID' );
                }

                return "DB://$location/$id";
        }

        /**
         * @inheritDoc
         */
        public function isReadOnly( $location ) {
                if ( parent::isReadOnly( $location ) ) {
                        return true;
                }

                return ( $this->getLoadBalancer( $location )->getReadOnlyReason() !== false );
        }

        /**
         * Get a LoadBalancer for the specified cluster
         *
         * @param string $cluster Cluster name
         * @return ILoadBalancer
         */
        private function getLoadBalancer( $cluster ) {
                return $this->lbFactory->getExternalLB( $cluster );
        }

        /**
         * Get a replica DB connection for the specified cluster
         *
         * @since 1.34
         * @param string $cluster Cluster name
         * @return \Wikimedia\Rdbms\IReadableDatabase
         */
        public function getReplica( $cluster ) {
                $lb = $this->getLoadBalancer( $cluster );

                return $lb->getConnection(
                        DB_REPLICA,
                        [],
                        $this->getDomainId( $lb->getServerInfo( ServerInfo::WRITER_INDEX ) ),
                        $lb::CONN_TRX_AUTOCOMMIT
                );
        }

        /**
         * Get a primary database connection for the specified cluster
         *
         * @param string $cluster Cluster name
         * @return \Wikimedia\Rdbms\IMaintainableDatabase
         * @since 1.37
         */
        public function getPrimary( $cluster ) {
                $lb = $this->getLoadBalancer( $cluster );

                return $lb->getMaintenanceConnectionRef(
                        DB_PRIMARY,
                        [],
                        $this->getDomainId( $lb->getServerInfo( ServerInfo::WRITER_INDEX ) ),
                        $lb::CONN_TRX_AUTOCOMMIT
                );
        }

        /**
         * @param array $server Primary DB server configuration array for LoadBalancer
         * @return string|false Database domain ID or false
         */
        private function getDomainId( array $server ) {
                if ( $this->isDbDomainExplicit ) {
                        return $this->dbDomain; // explicit foreign domain
                }

                if ( isset( $server['dbname'] ) ) {
                        // T200471: for b/c, treat any "dbname" field as forcing which database to use.
                        // MediaWiki/LoadBalancer previously did not enforce any concept of a local DB
                        // domain, but rather assumed that the LB server configuration matched $wgDBname.
                        // This check is useful when the external storage DB for this cluster does not use
                        // the same name as the corresponding "main" DB(s) for wikis.
                        $domain = new DatabaseDomain(
                                $server['dbname'],
                                $server['schema'] ?? null,
                                $server['tablePrefix'] ?? ''
                        );

                        return $domain->getId();
                }

                return false; // local LB domain
        }

        /**
         * Get the configured blobs table name for this database
         *
         * Typically, a suffix like "_clusterX" can be used to facilitate clean merging of
         * read-only storage clusters by simply cloning tables to the new cluster servers.
         *
         * @param string $cluster Cluster name
         * @return string Unqualified table name (e.g. "blobs_cluster32" or default "blobs")
         * @internal Only for use within ExternalStoreDB and its core maintenance scripts
         */
        public function getTable( string $cluster ) {
                $lb = $this->getLoadBalancer( $cluster );
                $info = $lb->getServerInfo( ServerInfo::WRITER_INDEX );

                return $info['blobs table'] ?? 'blobs';
        }

        /**
         * Create the appropriate blobs table on this cluster
         *
         * @since 1.34
         * @param string $cluster
         */
        public function initializeTable( $cluster ) {
                global $IP;

                static $supportedTypes = [ 'mysql', 'sqlite' ];

                $dbw = $this->getPrimary( $cluster );
                if ( !in_array( $dbw->getType(), $supportedTypes, true ) ) {
                        throw new DBUnexpectedError( $dbw, "RDBMS type '{$dbw->getType()}' not supported." );
                }

                $sqlFilePath = "$IP/maintenance/storage/blobs.sql";
                $sql = file_get_contents( $sqlFilePath );
                if ( $sql === false ) {
                        throw new RuntimeException( "Failed to read '$sqlFilePath'." );
                }

                $blobsTable = $this->getTable( $cluster );
                $encTable = $dbw->tableName( $blobsTable );
                $sqlWithReplacedVars = str_replace(
                        [ '/*$wgDBprefix*/blobs', '/*_*/blobs' ],
                        [ $encTable, $encTable ],
                        $sql
                );

                $dbw->query(
                        new Query(
                                $sqlWithReplacedVars,
                                $dbw::QUERY_CHANGE_SCHEMA,
                                'CREATE',
                                $blobsTable,
                                $sqlWithReplacedVars
                        ),
                        __METHOD__
                );
        }

        /**
         * Fetch a blob item out of the database; a cache of the last-loaded
         * blob will be kept so that multiple loads out of a multi-item blob
         * can avoid redundant database access and decompression.
         * @param string $cluster
         * @param string $id
         * @param string $itemID
         * @return HistoryBlob|false Returns false if missing
         */
        private function fetchBlob( $cluster, $id, $itemID ) {
                /**
                 * One-step cache variable to hold base blobs; operations that
                 * pull multiple revisions may often pull multiple times from
                 * the same blob. By keeping the last-used one open, we avoid
                 * redundant unserialization and decompression overhead.
                 */
                static $externalBlobCache = [];

                $cacheID = ( $itemID === false ) ? "$cluster/$id" : "$cluster/$id/";
                $cacheID = "$cacheID@{$this->dbDomain}";

                if ( isset( $externalBlobCache[$cacheID] ) ) {
                        $this->logger->debug( __METHOD__ . ": cache hit on $cacheID" );

                        return $externalBlobCache[$cacheID];
                }

                $this->logger->debug( __METHOD__ . ": cache miss on $cacheID" );

                $blobsTable = $this->getTable( $cluster );

                $dbr = $this->getReplica( $cluster );
                $ret = $dbr->newSelectQueryBuilder()
                        ->select( 'blob_text' )
                        ->from( $blobsTable )
                        ->where( [ 'blob_id' => $id ] )
                        ->caller( __METHOD__ )->fetchField();

                if ( $ret === false ) {
                        // Try the primary DB
                        $this->logger->warning( __METHOD__ . ": primary DB fallback on $cacheID" );
                        $trxProfiler = $this->lbFactory->getTransactionProfiler();
                        $scope = $trxProfiler->silenceForScope( $trxProfiler::EXPECTATION_REPLICAS_ONLY );
                        $dbw = $this->getPrimary( $cluster );
                        $ret = $dbw->newSelectQueryBuilder()
                                ->select( 'blob_text' )
                                ->from( $blobsTable )
                                ->where( [ 'blob_id' => $id ] )
                                ->caller( __METHOD__ )->fetchField();
                        ScopedCallback::consume( $scope );
                        if ( $ret === false ) {
                                $this->logger->warning( __METHOD__ . ": primary DB failed to find $cacheID" );
                        }
                }
                if ( $itemID !== false && $ret !== false ) {
                        // Unserialise object; caller extracts item
                        $ret = HistoryBlobUtils::unserialize( $ret );
                }

                $externalBlobCache = [ $cacheID => $ret ];

                return $ret;
        }

        /**
         * Fetch multiple blob items out of the database
         *
         * @param string $cluster A cluster name valid for use with LBFactory
         * @param array $ids A map from the blob_id's to look for to the requested itemIDs in the blobs
         * @return array A map from the blob_id's requested to their content.
         *   Unlocated ids are not represented
         */
        private function batchFetchBlobs( $cluster, array $ids ) {
                $blobsTable = $this->getTable( $cluster );

                $dbr = $this->getReplica( $cluster );
                $res = $dbr->newSelectQueryBuilder()
                        ->select( [ 'blob_id', 'blob_text' ] )
                        ->from( $blobsTable )
                        ->where( [ 'blob_id' => array_keys( $ids ) ] )
                        ->caller( __METHOD__ )
                        ->fetchResultSet();

                $ret = [];
                $this->mergeBatchResult( $ret, $ids, $res );
                if ( $ids ) {
                        // Try the primary
                        $this->logger->info(
                                __METHOD__ . ": primary fallback on '$cluster' for: " .
                                implode( ',', array_keys( $ids ) )
                        );
                        $trxProfiler = $this->lbFactory->getTransactionProfiler();
                        $scope = $trxProfiler->silenceForScope( $trxProfiler::EXPECTATION_REPLICAS_ONLY );
                        $dbw = $this->getPrimary( $cluster );
                        $res = $dbw->newSelectQueryBuilder()
                                ->select( [ 'blob_id', 'blob_text' ] )
                                ->from( $blobsTable )
                                ->where( [ 'blob_id' => array_keys( $ids ) ] )
                                ->caller( __METHOD__ )
                                ->fetchResultSet();
                        ScopedCallback::consume( $scope );
                        $this->mergeBatchResult( $ret, $ids, $res );
                }
                if ( $ids ) {
                        $this->logger->error(
                                __METHOD__ . ": primary on '$cluster' failed locating items: " .
                                implode( ',', array_keys( $ids ) )
                        );
                }

                return $ret;
        }

        /**
         * Helper function for self::batchFetchBlobs for merging primary/replica DB results
         * @param array &$ret Current self::batchFetchBlobs return value
         * @param array &$ids Map from blob_id to requested itemIDs
         * @param mixed $res DB result from Database::select
         */
        private function mergeBatchResult( array &$ret, array &$ids, $res ) {
                foreach ( $res as $row ) {
                        $id = $row->blob_id;
                        $itemIDs = $ids[$id];
                        unset( $ids[$id] ); // to track if everything is found
                        if ( count( $itemIDs ) === 1 && reset( $itemIDs ) === false ) {
                                // single result stored per blob
                                $ret[$id] = $row->blob_text;
                        } else {
                                // multi result stored per blob
                                $ret[$id] = HistoryBlobUtils::unserialize( $row->blob_text );
                        }
                }
        }

        /**
         * @param string $url
         * @return array
         */
        protected function parseURL( $url ) {
                $path = explode( '/', $url );

                return [
                        $path[2], // cluster
                        $path[3], // id
                        $path[4] ?? false // itemID
                ];
        }

        /**
         * Get the cluster part of a URL
         *
         * @internal for installer
         * @param string $url
         * @return string|null
         */
        public function getClusterForUrl( $url ) {
                $parts = explode( '/', $url );
                return $parts[2] ?? null;
        }

        /**
         * Get the domain ID for a given cluster, which is false for the local wiki ID
         *
         * @internal for installer
         * @param string $cluster
         * @return string|false
         */
        public function getDomainIdForCluster( $cluster ) {
                $lb = $this->getLoadBalancer( $cluster );
                return $this->getDomainId( $lb->getServerInfo( ServerInfo::WRITER_INDEX ) );
        }
}