Avoid pointless use of isset() in LBFactoryMulti()

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

<?php
/**
 * Advanced generator of database load balancing objects for database 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-database, multi-master factory for Wikimedia and similar installations.
 * Ignores the old configuration globals.
 *
 * @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[] Server info associative array
         * @note 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 = [];

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

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

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

        /**
         * @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 section */
        private $templateOverridesBySection;

        /** @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 = [];

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

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

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

        /** @var string */
        private $loadMonitorClass = 'LoadMonitor';

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

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

        /**
         * @see LBFactory::__construct()
         *
         * Template override precedence (highest => lowest):
         *   - templateOverridesByServer
         *   - masterTemplateOverrides
         *   - templateOverridesBySection/templateOverridesByCluster
         *   - externalTemplateOverrides
         *   - serverTemplate
         * Overrides only work on top level keys (so nested values will not be merged).
         *
         * Server configuration maps should be of the format Database::factory() requires.
         * Additionally, a 'max lag' key should also be set on server maps, indicating how stale the
         * data can be before the load balancer tries to avoid using it. The map can have 'is static'
         * set to disable blocking  replication sync checks (intended for archive servers with
         * unchanging data).
         *
         * @param array $conf Parameters of LBFactory::__construct() as well as:
         *   - sectionsByDB                Map of database names to section names.
         *   - sectionLoads                2-d map. For each section, gives a map of server names to
         *                                 load ratios. For example:
         *                                 [
         *                                     'section1' => [
         *                                         'db1' => 100,
         *                                         'db2' => 100
         *                                     ]
         *                                 ]
         *   - serverTemplate              Server configuration map intended for Database::factory().
         *                                 Note that "host", "hostName" and "load" entries will be
         *                                 overridden by "sectionLoads" and "hostsByName".
         *   - groupLoadsBySection         3-d map giving server load ratios for each section/group.
         *                                 For example:
         *                                 [
         *                                     'section1' => [
         *                                         'group1' => [
         *                                             'db1' => 100,
         *                                             'db2' => 100
         *                                         ]
         *                                     ]
         *                                 ]
         *   - groupLoadsByDB              3-d map giving server load ratios by DB name.
         *   - hostsByName                 Map of hostname to IP address.
         *   - externalLoads               Map of external storage cluster name to server load map.
         *   - externalTemplateOverrides   Set of server configuration maps overriding
         *                                 "serverTemplate" for external storage.
         *   - templateOverridesByServer   2-d map overriding "serverTemplate" and
         *                                 "externalTemplateOverrides" on a server-by-server basis.
         *                                 Applies to both core and external storage.
         *   - templateOverridesBySection  2-d map overriding the server configuration maps by section.
         *   - templateOverridesByCluster  2-d map overriding the server configuration maps by external
         *                                 storage cluster.
         *   - masterTemplateOverrides     Server configuration map overrides 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.
         */
        public function __construct( array $conf ) {
                parent::__construct( $conf );

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

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

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

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

                return $section;
        }

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

                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];
                }

                $template = $this->serverTemplate;
                if ( isset( $this->templateOverridesBySection[$section] ) ) {
                        $template = $this->templateOverridesBySection[$section] + $template;
                }

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

        /**
         * @param DatabaseDomain|string|bool $domain Domain ID, or false for the current domain
         * @return LoadBalancer
         */
        public function getMainLB( $domain = false ) {
                $section = $this->getSectionForDomain( $domain );
                if ( !isset( $this->mainLBs[$section] ) ) {
                        $lb = $this->newMainLB( $domain );
                        $this->getChronologyProtector()->initLB( $lb );
                        $this->mainLBs[$section] = $lb;
                }

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

        public function newExternalLB( $cluster ) {
                if ( !isset( $this->externalLoads[$cluster] ) ) {
                        throw new InvalidArgumentException( __METHOD__ . ": Unknown cluster \"$cluster\"" );
                }
                $template = $this->serverTemplate;
                if ( $this->externalTemplateOverrides ) {
                        $template = $this->externalTemplateOverrides + $template;
                }
                if ( isset( $this->templateOverridesByCluster[$cluster] ) ) {
                        $template = $this->templateOverridesByCluster[$cluster] + $template;
                }

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

        public function getExternalLB( $cluster ) {
                if ( !isset( $this->extLBs[$cluster] ) ) {
                        $this->extLBs[$cluster] = $this->newExternalLB( $cluster );
                        $this->getChronologyProtector()->initLB( $this->extLBs[$cluster] );
                }

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

        public function getAllMainLBs() {
                $lbs = [];
                foreach ( $this->sectionsByDB as $db => $section ) {
                        if ( !isset( $lbs[$section] ) ) {
                                $lbs[$section] = $this->getMainLB( $db );
                        }
                }

                return $lbs;
        }

        public function getAllExternalLBs() {
                $lbs = [];
                foreach ( $this->externalLoads as $cluster => $unused ) {
                        $lbs[$cluster] = $this->getExternalLB( $cluster );
                }

                return $lbs;
        }

        /**
         * 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 ) {
                $lb = new LoadBalancer( array_merge(
                        $this->baseLoadBalancerParams(),
                        [
                                'servers' => $this->makeServerArray( $template, $loads, $groupLoads ),
                                'loadMonitor' => [ 'class' => $this->loadMonitorClass ],
                                'readOnlyReason' => $readOnlyReason
                        ]
                ) );
                $this->initLoadBalancer( $lb );

                return $lb;
        }

        /**
         * 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 = [];
                $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 ( $this->masterTemplateOverrides ) {
                                        $serverInfo = $this->masterTemplateOverrides + $serverInfo;
                                }
                                $master = false;
                        } else {
                                $serverInfo['replica'] = 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;
                        $serverInfo += [ 'flags' => IDatabase::DBO_DEFAULT ];

                        $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 = [];
                foreach ( $groupLoads as $group => $loads ) {
                        foreach ( $loads as $server => $load ) {
                                $reindexed[$server][$group] = $load;
                        }
                }

                return $reindexed;
        }

        /**
         * @param DatabaseDomain|string|bool $domain Domain ID, or false for the current domain
         * @return array [database name, table prefix]
         */
        private function getDBNameAndPrefix( $domain = false ) {
                $domain = ( $domain === false )
                        ? $this->localDomain
                        : DatabaseDomain::newFromId( $domain );

                return [ $domain->getDatabase(), $domain->getTablePrefix() ];
        }

        /**
         * 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 = [] ) {
                foreach ( $this->mainLBs as $lb ) {
                        call_user_func_array( $callback, array_merge( [ $lb ], $params ) );
                }
                foreach ( $this->extLBs as $lb ) {
                        call_user_func_array( $callback, array_merge( [ $lb ], $params ) );
                }
        }
}