includes/db/LBFactory_Multi.php

   1 <?php
   2 /**
   3  * Advanced database load balancing for wiki farms
   4  *
   5  * @file
   6  * @ingroup Database
   7  */
   8
   9
  10 /**
  11  * A multi-wiki, multi-master factory for Wikimedia and similar installations.
  12  * Ignores the old configuration globals
  13  *
  14  * Configuration:
  15  *     sectionsByDB                A map of database names to section names
  16  *
  17  *     sectionLoads                A 2-d map. For each section, gives a map of server names to load ratios.
  18  *                                 For example: array( 'section1' => array( 'db1' => 100, 'db2' => 100 ) )
  19  *
  20  *     serverTemplate              A server info associative array as documented for $wgDBservers. The host,
  21  *                                 hostName and load entries will be overridden.
  22  *
  23  *     groupLoadsBySection         A 3-d map giving server load ratios for each section and group. For example:
  24  *                                 array( 'section1' => array( 'group1' => array( 'db1' => 100, 'db2' => 100 ) ) )
  25  *
  26  *     groupLoadsByDB              A 3-d map giving server load ratios by DB name.
  27  *
  28  *     hostsByName                 A map of hostname to IP address.
  29  *
  30  *     externalLoads               A map of external storage cluster name to server load map
  31  *
  32  *     externalTemplateOverrides   A set of server info keys overriding serverTemplate for external storage
  33  *
  34  *     templateOverridesByServer   A 2-d map overriding serverTemplate and externalTemplateOverrides on a
  35  *                                 server-by-server basis. Applies to both core and external storage.
  36  *
  37  *     templateOverridesByCluster  A 2-d map overriding the server info by external storage cluster
  38  *
  39  *     masterTemplateOverrides     An override array for all master servers.
  40  *
  41  *     readOnlyBySection           A map of section name to read-only message. Missing or false for read/write.
  42  *
  43  * @ingroup Database
  44  */
  45 class LBFactory_Multi extends LBFactory {
  46         // Required settings
  47         var $sectionsByDB, $sectionLoads, $serverTemplate;
  48         // Optional settings
  49         var $groupLoadsBySection = array(), $groupLoadsByDB = array(), $hostsByName = array();
  50         var $externalLoads = array(), $externalTemplateOverrides, $templateOverridesByServer;
  51         var $templateOverridesByCluster, $masterTemplateOverrides, $readOnlyBySection = array();
  52         // Other stuff
  53         var $conf, $mainLBs = array(), $extLBs = array();
  54         var $lastWiki, $lastSection;
  55
  56         function __construct( $conf ) {
  57                 $this->chronProt = new ChronologyProtector;
  58                 $this->conf = $conf;
  59                 $required = array( 'sectionsByDB', 'sectionLoads', 'serverTemplate' );
  60                 $optional = array( 'groupLoadsBySection', 'groupLoadsByDB', 'hostsByName',
  61                         'externalLoads', 'externalTemplateOverrides', 'templateOverridesByServer',
  62                         'templateOverridesByCluster', 'masterTemplateOverrides',
  63                         'readOnlyBySection' );
  64
  65                 foreach ( $required as $key ) {
  66                         if ( !isset( $conf[$key] ) ) {
  67                                 throw new MWException( __CLASS__.": $key is required in configuration" );
  68                         }
  69                         $this->$key = $conf[$key];
  70                 }
  71
  72                 foreach ( $optional as $key ) {
  73                         if ( isset( $conf[$key] ) ) {
  74                                 $this->$key = $conf[$key];
  75                         }
  76                 }
  77
  78                 // Check for read-only mode
  79                 $section = $this->getSectionForWiki();
  80                 if ( !empty( $this->readOnlyBySection[$section] ) ) {
  81                         global $wgReadOnly;
  82                         $wgReadOnly = $this->readOnlyBySection[$section];
  83                 }
  84         }
  85
  86         function getSectionForWiki( $wiki = false ) {
  87                 if ( $this->lastWiki === $wiki ) {
  88                         return $this->lastSection;
  89                 }
  90                 list( $dbName, $prefix ) = $this->getDBNameAndPrefix( $wiki );
  91                 if ( isset( $this->sectionsByDB[$dbName] ) ) {
  92                         $section = $this->sectionsByDB[$dbName];
  93                 } else {
  94                         $section = 'DEFAULT';
  95                 }
  96                 $this->lastSection = $section;
  97                 $this->lastWiki = $wiki;
  98                 return $section;
  99         }
 100
 101         function newMainLB( $wiki = false ) {
 102                 list( $dbName, $prefix ) = $this->getDBNameAndPrefix( $wiki );
 103                 $section = $this->getSectionForWiki( $wiki );
 104                 $groupLoads = array();
 105                 if ( isset( $this->groupLoadsByDB[$dbName] ) ) {
 106                         $groupLoads = $this->groupLoadsByDB[$dbName];
 107                 }
 108                 if ( isset( $this->groupLoadsBySection[$section] ) ) {
 109                         $groupLoads = array_merge_recursive( $groupLoads, $this->groupLoadsBySection[$section] );
 110                 }
 111                 return $this->newLoadBalancer( $this->serverTemplate, $this->sectionLoads[$section], $groupLoads );
 112         }
 113
 114         function getMainLB( $wiki = false ) {
 115                 $section = $this->getSectionForWiki( $wiki );
 116                 if ( !isset( $this->mainLBs[$section] ) ) {
 117                         $lb = $this->newMainLB( $wiki, $section );
 118                         $this->chronProt->initLB( $lb );
 119                         $lb->parentInfo( array( 'id' => "main-$section" ) );
 120                         $this->mainLBs[$section] = $lb;
 121                 }
 122                 return $this->mainLBs[$section];
 123         }
 124
 125         function newExternalLB( $cluster, $wiki = false ) {
 126                 if ( !isset( $this->externalLoads[$cluster] ) ) {
 127                         throw new MWException( __METHOD__.": Unknown cluster \"$cluster\"" );
 128                 }
 129                 $template = $this->serverTemplate;
 130                 if ( isset( $this->externalTemplateOverrides ) ) {
 131                         $template = $this->externalTemplateOverrides + $template;
 132                 }
 133                 if ( isset( $this->templateOverridesByCluster[$cluster] ) ) {
 134                         $template = $this->templateOverridesByCluster[$cluster] + $template;
 135                 }
 136                 return $this->newLoadBalancer( $template, $this->externalLoads[$cluster], array() );
 137         }
 138
 139         function &getExternalLB( $cluster, $wiki = false ) {
 140                 if ( !isset( $this->extLBs[$cluster] ) ) {
 141                         $this->extLBs[$cluster] = $this->newExternalLB( $cluster, $wiki );
 142                         $this->extLBs[$cluster]->parentInfo( array( 'id' => "ext-$cluster" ) );
 143                 }
 144                 return $this->extLBs[$cluster];
 145         }
 146
 147         /**
 148          * Make a new load balancer object based on template and load array
 149          */
 150         function newLoadBalancer( $template, $loads, $groupLoads ) {
 151                 global $wgMasterWaitTimeout;
 152                 $servers = $this->makeServerArray( $template, $loads, $groupLoads );
 153                 $lb = new LoadBalancer( array(
 154                         'servers' => $servers,
 155                         'masterWaitTimeout' => $wgMasterWaitTimeout
 156                 ));
 157                 return $lb;
 158         }
 159
 160         /**
 161          * Make a server array as expected by LoadBalancer::__construct, using a template and load array
 162          */
 163         function makeServerArray( $template, $loads, $groupLoads ) {
 164                 $servers = array();
 165                 $master = true;
 166                 $groupLoadsByServer = $this->reindexGroupLoads( $groupLoads );
 167                 foreach ( $groupLoadsByServer as $server => $stuff ) {
 168                         if ( !isset( $loads[$server] ) ) {
 169                                 $loads[$server] = 0;
 170                         }
 171                 }
 172                 foreach ( $loads as $serverName => $load ) {
 173                         $serverInfo = $template;
 174                         if ( $master ) {
 175                                 $serverInfo['master'] = true;
 176                                 if ( isset( $this->masterTemplateOverrides ) ) {
 177                                         $serverInfo = $this->masterTemplateOverrides + $serverInfo;
 178                                 }
 179                                 $master = false;
 180                         }
 181                         if ( isset( $this->templateOverridesByServer[$serverName] ) ) {
 182                                 $serverInfo = $this->templateOverridesByServer[$serverName] + $serverInfo;
 183                         }
 184                         if ( isset( $groupLoadsByServer[$serverName] ) ) {
 185                                 $serverInfo['groupLoads'] = $groupLoadsByServer[$serverName];
 186                         }
 187                         if ( isset( $this->hostsByName[$serverName] ) ) {
 188                                 $serverInfo['host'] = $this->hostsByName[$serverName];
 189                         } else {
 190                                 $serverInfo['host'] = $serverName;
 191                         }
 192                         $serverInfo['hostName'] = $serverName;
 193                         $serverInfo['load'] = $load;
 194                         $servers[] = $serverInfo;
 195                 }
 196                 return $servers;
 197         }
 198
 199         /**
 200          * Take a group load array indexed by group then server, and reindex it by server then group
 201          */
 202         function reindexGroupLoads( $groupLoads ) {
 203                 $reindexed = array();
 204                 foreach ( $groupLoads as $group => $loads ) {
 205                         foreach ( $loads as $server => $load ) {
 206                                 $reindexed[$server][$group] = $load;
 207                         }
 208                 }
 209                 return $reindexed;
 210         }
 211
 212         /**
 213          * Get the database name and prefix based on the wiki ID
 214          */
 215         function getDBNameAndPrefix( $wiki = false ) {
 216                 if ( $wiki === false ) {
 217                         global $wgDBname, $wgDBprefix;
 218                         return array( $wgDBname, $wgDBprefix );
 219                 } else {
 220                         return wfSplitWikiID( $wiki );
 221                 }
 222         }
 223
 224         /**
 225          * Execute a function for each tracked load balancer
 226          * The callback is called with the load balancer as the first parameter,
 227          * and $params passed as the subsequent parameters.
 228          */
 229         function forEachLB( $callback, $params = array() ) {
 230                 foreach ( $this->mainLBs as $lb ) {
 231                         call_user_func_array( $callback, array_merge( array( $lb ), $params ) );
 232                 }
 233                 foreach ( $this->extLBs as $lb ) {
 234                         call_user_func_array( $callback, array_merge( array( $lb ), $params ) );
 235                 }
 236         }
 237
 238         function shutdown() {
 239                 foreach ( $this->mainLBs as $lb ) {
 240                         $this->chronProt->shutdownLB( $lb );
 241                 }
 242                 $this->chronProt->shutdown();
 243                 $this->commitMasterChanges();
 244         }
 245 }