PHPSessionHandler: Implement SessionHandlerInterface

[mediawiki.git] / includes / db / loadbalancer / LBFactoryMulti.php

<?php
/**
 * Advanced generator of database load balancing objects for wiki farms.
 *
 * 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
 */

/**
 * A multi-wiki, multi-master factory for Wikimedia and similar installations.
 * Ignores the old configuration globals
 *
 * Configuration:
 *     sectionsByDB                A map of database names to section names.
 *
 *     sectionLoads                A 2-d map. For each section, gives a map of server names to
 *                                 load ratios. For example:
 *                                 array(
 *                                     'section1' => array(
 *                                         'db1' => 100,
 *                                         'db2' => 100
 *                                     )
 *                                 )
 *
 *     serverTemplate              A server info associative array as documented for $wgDBservers.
 *                                 The host, hostName and load entries will be overridden.
 *
 *     groupLoadsBySection         A 3-d map giving server load ratios for each section and group.
 *                                 For example:
 *                                 array(
 *                                     'section1' => array(
 *                                         'group1' => array(
 *                                             'db1' => 100,
 *                                             'db2' => 100
 *                                         )
 *                                     )
 *                                 )
 *
 *     groupLoadsByDB              A 3-d map giving server load ratios by DB name.
 *
 *     hostsByName                 A map of hostname to IP address.
 *
 *     externalLoads               A map of external storage cluster name to server load map.
 *
 *     externalTemplateOverrides   A set of server info keys overriding serverTemplate for external
 *                                 storage.
 *
 *     templateOverridesByServer   A 2-d map overriding serverTemplate and
 *                                 externalTemplateOverrides on a server-by-server basis. Applies
 *                                 to both core and external storage.
 *
 *     templateOverridesByCluster  A 2-d map overriding the server info by external storage cluster.
 *
 *     masterTemplateOverrides     An override array for all master servers.
 *
 *     loadMonitorClass            Name of the LoadMonitor class to always use.
 *
 *     readOnlyBySection           A map of section name to read-only message.
 *                                 Missing or false for read/write.
 *
 * @ingroup Database
 */
class LBFactoryMulti extends LBFactory {
        /** @var array A map of database names to section names */
        private $sectionsByDB;

        /**
         * @var array A 2-d map. For each section, gives a map of server names to
         * load ratios
         */
        private $sectionLoads;

        /**
         * @var array A server info associative array as documented for
         * $wgDBservers. The host, hostName and load entries will be
         * overridden
         */
        private $serverTemplate;

        // Optional settings

        /** @var array A 3-d map giving server load ratios for each section and group */
        private $groupLoadsBySection = array();

        /** @var array A 3-d map giving server load ratios by DB name */
        private $groupLoadsByDB = array();

        /** @var array A map of hostname to IP address */
        private $hostsByName = array();

        /** @var array A map of external storage cluster name to server load map */
        private $externalLoads = array();

        /**
         * @var array A set of server info keys overriding serverTemplate for
         * external storage
         */
        private $externalTemplateOverrides;

        /**
         * @var array A 2-d map overriding serverTemplate and
         * externalTemplateOverrides on a server-by-server basis. Applies to both
         * core and external storage
         */
        private $templateOverridesByServer;

        /** @var array A 2-d map overriding the server info by external storage cluster */
        private $templateOverridesByCluster;

        /** @var array An override array for all master servers */
        private $masterTemplateOverrides;

        /**
         * @var array|bool A map of section name to read-only message. Missing or
         * false for read/write
         */
        private $readOnlyBySection = array();

        // Other stuff

        /** @var array Load balancer factory configuration */
        private $conf;

        /** @var LoadBalancer[] */
        private $mainLBs = array();

        /** @var LoadBalancer[] */
        private $extLBs = array();

        /** @var string */
        private $loadMonitorClass;

        /** @var string */
        private $lastWiki;

        /** @var string */
        private $lastSection;

        /**
         * @param array $conf
         * @throws MWException
         */
        public function __construct( array $conf ) {
                parent::__construct( $conf );

                $this->conf = $conf;
                $required = array( 'sectionsByDB', 'sectionLoads', 'serverTemplate' );
                $optional = array( 'groupLoadsBySection', 'groupLoadsByDB', 'hostsByName',
                        'externalLoads', 'externalTemplateOverrides', 'templateOverridesByServer',
                        'templateOverridesByCluster', 'masterTemplateOverrides',
                        'readOnlyBySection', 'loadMonitorClass' );

                foreach ( $required as $key ) {
                        if ( !isset( $conf[$key] ) ) {
                                throw new MWException( __CLASS__ . ": $key is required in configuration" );
                        }
                        $this->$key = $conf[$key];
                }

                foreach ( $optional as $key ) {
                        if ( isset( $conf[$key] ) ) {
                                $this->$key = $conf[$key];
                        }
                }
        }

        /**
         * @param bool|string $wiki
         * @return string
         */
        private function getSectionForWiki( $wiki = false ) {
                if ( $this->lastWiki === $wiki ) {
                        return $this->lastSection;
                }
                list( $dbName, ) = $this->getDBNameAndPrefix( $wiki );
                if ( isset( $this->sectionsByDB[$dbName] ) ) {
                        $section = $this->sectionsByDB[$dbName];
                } else {
                        $section = 'DEFAULT';
                }
                $this->lastSection = $section;
                $this->lastWiki = $wiki;

                return $section;
        }

        /**
         * @param bool|string $wiki
         * @return LoadBalancer
         */
        public function newMainLB( $wiki = false ) {
                list( $dbName, ) = $this->getDBNameAndPrefix( $wiki );
                $section = $this->getSectionForWiki( $wiki );
                if ( isset( $this->groupLoadsByDB[$dbName] ) ) {
                        $groupLoads = $this->groupLoadsByDB[$dbName];
                } else {
                        $groupLoads = array();
                }

                if ( isset( $this->groupLoadsBySection[$section] ) ) {
                        $groupLoads = array_merge_recursive( $groupLoads, $this->groupLoadsBySection[$section] );
                }

                $readOnlyReason = $this->readOnlyReason;
                // Use the LB-specific read-only reason if everything isn't already read-only
                if ( $readOnlyReason === false && isset( $this->readOnlyBySection[$section] ) ) {
                        $readOnlyReason = $this->readOnlyBySection[$section];
                }

                return $this->newLoadBalancer(
                        $this->serverTemplate,
                        $this->sectionLoads[$section],
                        $groupLoads,
                        $readOnlyReason
                );
        }

        /**
         * @param bool|string $wiki
         * @return LoadBalancer
         */
        public function getMainLB( $wiki = false ) {
                $section = $this->getSectionForWiki( $wiki );
                if ( !isset( $this->mainLBs[$section] ) ) {
                        $lb = $this->newMainLB( $wiki );
                        $lb->parentInfo( array( 'id' => "main-$section" ) );
                        $this->chronProt->initLB( $lb );
                        $this->mainLBs[$section] = $lb;
                }

                return $this->mainLBs[$section];
        }

        /**
         * @param string $cluster
         * @param bool|string $wiki
         * @throws MWException
         * @return LoadBalancer
         */
        protected function newExternalLB( $cluster, $wiki = false ) {
                if ( !isset( $this->externalLoads[$cluster] ) ) {
                        throw new MWException( __METHOD__ . ": Unknown cluster \"$cluster\"" );
                }
                $template = $this->serverTemplate;
                if ( isset( $this->externalTemplateOverrides ) ) {
                        $template = $this->externalTemplateOverrides + $template;
                }
                if ( isset( $this->templateOverridesByCluster[$cluster] ) ) {
                        $template = $this->templateOverridesByCluster[$cluster] + $template;
                }

                return $this->newLoadBalancer(
                        $template,
                        $this->externalLoads[$cluster],
                        array(),
                        $this->readOnlyReason
                );
        }

        /**
         * @param string $cluster External storage cluster, or false for core
         * @param bool|string $wiki Wiki ID, or false for the current wiki
         * @return LoadBalancer
         */
        public function &getExternalLB( $cluster, $wiki = false ) {
                if ( !isset( $this->extLBs[$cluster] ) ) {
                        $this->extLBs[$cluster] = $this->newExternalLB( $cluster, $wiki );
                        $this->extLBs[$cluster]->parentInfo( array( 'id' => "ext-$cluster" ) );
                        $this->chronProt->initLB( $this->extLBs[$cluster] );
                }

                return $this->extLBs[$cluster];
        }

        /**
         * Make a new load balancer object based on template and load array
         *
         * @param array $template
         * @param array $loads
         * @param array $groupLoads
         * @param string|bool $readOnlyReason
         * @return LoadBalancer
         */
        private function newLoadBalancer( $template, $loads, $groupLoads, $readOnlyReason ) {
                return new LoadBalancer( array(
                        'servers' => $this->makeServerArray( $template, $loads, $groupLoads ),
                        'loadMonitor' => $this->loadMonitorClass,
                        'readOnlyReason' => $readOnlyReason,
                        'trxProfiler' => $this->trxProfiler
                ) );
        }

        /**
         * Make a server array as expected by LoadBalancer::__construct, using a template and load array
         *
         * @param array $template
         * @param array $loads
         * @param array $groupLoads
         * @return array
         */
        private function makeServerArray( $template, $loads, $groupLoads ) {
                $servers = array();
                $master = true;
                $groupLoadsByServer = $this->reindexGroupLoads( $groupLoads );
                foreach ( $groupLoadsByServer as $server => $stuff ) {
                        if ( !isset( $loads[$server] ) ) {
                                $loads[$server] = 0;
                        }
                }
                foreach ( $loads as $serverName => $load ) {
                        $serverInfo = $template;
                        if ( $master ) {
                                $serverInfo['master'] = true;
                                if ( isset( $this->masterTemplateOverrides ) ) {
                                        $serverInfo = $this->masterTemplateOverrides + $serverInfo;
                                }
                                $master = false;
                        } else {
                                $serverInfo['slave'] = true;
                        }
                        if ( isset( $this->templateOverridesByServer[$serverName] ) ) {
                                $serverInfo = $this->templateOverridesByServer[$serverName] + $serverInfo;
                        }
                        if ( isset( $groupLoadsByServer[$serverName] ) ) {
                                $serverInfo['groupLoads'] = $groupLoadsByServer[$serverName];
                        }
                        if ( isset( $this->hostsByName[$serverName] ) ) {
                                $serverInfo['host'] = $this->hostsByName[$serverName];
                        } else {
                                $serverInfo['host'] = $serverName;
                        }
                        $serverInfo['hostName'] = $serverName;
                        $serverInfo['load'] = $load;
                        $servers[] = $serverInfo;
                }

                return $servers;
        }

        /**
         * Take a group load array indexed by group then server, and reindex it by server then group
         * @param array $groupLoads
         * @return array
         */
        private function reindexGroupLoads( $groupLoads ) {
                $reindexed = array();
                foreach ( $groupLoads as $group => $loads ) {
                        foreach ( $loads as $server => $load ) {
                                $reindexed[$server][$group] = $load;
                        }
                }

                return $reindexed;
        }

        /**
         * Get the database name and prefix based on the wiki ID
         * @param bool|string $wiki
         * @return array
         */
        private function getDBNameAndPrefix( $wiki = false ) {
                if ( $wiki === false ) {
                        global $wgDBname, $wgDBprefix;

                        return array( $wgDBname, $wgDBprefix );
                } else {
                        return wfSplitWikiID( $wiki );
                }
        }

        /**
         * 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
         */
        public function forEachLB( $callback, array $params = array() ) {
                foreach ( $this->mainLBs as $lb ) {
                        call_user_func_array( $callback, array_merge( array( $lb ), $params ) );
                }
                foreach ( $this->extLBs as $lb ) {
                        call_user_func_array( $callback, array_merge( array( $lb ), $params ) );
                }
        }

        public function shutdown( $flags = 0 ) {
                if ( !( $flags & self::SHUTDOWN_NO_CHRONPROT ) ) {
                        $this->shutdownChronologyProtector( $this->chronProt );
                }
                $this->commitMasterChanges( __METHOD__ ); // sanity
        }
}