includes/db/LoadBalancer.php

   1 <?php
   2 /**
   3  * Database load balancing
   4  *
   5  * @file
   6  * @ingroup Database
   7  */
   8
   9 /**
  10  * Database load balancing object
  11  *
  12  * @todo document
  13  * @ingroup Database
  14  */
  15 class LoadBalancer {
  16         /* private */ var $mServers, $mConns, $mLoads, $mGroupLoads;
  17         /* private */ var $mFailFunction, $mErrorConnection;
  18         /* private */ var $mReadIndex, $mAllowLagged;
  19         /* private */ var $mWaitForPos, $mWaitTimeout;
  20         /* private */ var $mLaggedSlaveMode, $mLastError = 'Unknown error';
  21         /* private */ var $mParentInfo, $mLagTimes;
  22         /* private */ var $mLoadMonitorClass, $mLoadMonitor;
  23
  24         /**
  25          * @param $params Array with keys:
  26          *    servers           Required. Array of server info structures.
  27          *    failFunction      Deprecated, use exceptions instead.
  28          *    masterWaitTimeout Replication lag wait timeout
  29          *    loadMonitor       Name of a class used to fetch server lag and load.
  30          */
  31         function __construct( $params )
  32         {
  33                 if ( !isset( $params['servers'] ) ) {
  34                         throw new MWException( __CLASS__.': missing servers parameter' );
  35                 }
  36                 $this->mServers = $params['servers'];
  37
  38                 if ( isset( $params['failFunction'] ) ) {
  39                         $this->mFailFunction = $params['failFunction'];
  40                 } else {
  41                         $this->mFailFunction = false;
  42                 }
  43                 if ( isset( $params['waitTimeout'] ) ) {
  44                         $this->mWaitTimeout = $params['waitTimeout'];
  45                 } else {
  46                         $this->mWaitTimeout = 10;
  47                 }
  48
  49                 $this->mReadIndex = -1;
  50                 $this->mWriteIndex = -1;
  51                 $this->mConns = array(
  52                         'local' => array(),
  53                         'foreignUsed' => array(),
  54                         'foreignFree' => array() );
  55                 $this->mLoads = array();
  56                 $this->mWaitForPos = false;
  57                 $this->mLaggedSlaveMode = false;
  58                 $this->mErrorConnection = false;
  59                 $this->mAllowLag = false;
  60                 $this->mLoadMonitorClass = isset( $params['loadMonitor'] )
  61                         ? $params['loadMonitor'] : 'LoadMonitor_MySQL';
  62
  63                 foreach( $params['servers'] as $i => $server ) {
  64                         $this->mLoads[$i] = $server['load'];
  65                         if ( isset( $server['groupLoads'] ) ) {
  66                                 foreach ( $server['groupLoads'] as $group => $ratio ) {
  67                                         if ( !isset( $this->mGroupLoads[$group] ) ) {
  68                                                 $this->mGroupLoads[$group] = array();
  69                                         }
  70                                         $this->mGroupLoads[$group][$i] = $ratio;
  71                                 }
  72                         }
  73                 }
  74         }
  75
  76         static function newFromParams( $servers, $failFunction = false, $waitTimeout = 10 )
  77         {
  78                 return new LoadBalancer( $servers, $failFunction, $waitTimeout );
  79         }
  80
  81         /**
  82          * Get a LoadMonitor instance
  83          */
  84         function getLoadMonitor() {
  85                 if ( !isset( $this->mLoadMonitor ) ) {
  86                         $class = $this->mLoadMonitorClass;
  87                         $this->mLoadMonitor = new $class( $this );
  88                 }
  89                 return $this->mLoadMonitor;
  90         }
  91
  92         /**
  93          * Get or set arbitrary data used by the parent object, usually an LBFactory
  94          */
  95         function parentInfo( $x = null ) {
  96                 return wfSetVar( $this->mParentInfo, $x );
  97         }
  98
  99         /**
 100          * Given an array of non-normalised probabilities, this function will select
 101          * an element and return the appropriate key
 102          */
 103         function pickRandom( $weights )
 104         {
 105                 if ( !is_array( $weights ) || count( $weights ) == 0 ) {
 106                         return false;
 107                 }
 108
 109                 $sum = array_sum( $weights );
 110                 if ( $sum == 0 ) {
 111                         # No loads on any of them
 112                         # In previous versions, this triggered an unweighted random selection,
 113                         # but this feature has been removed as of April 2006 to allow for strict
 114                         # separation of query groups.
 115                         return false;
 116                 }
 117                 $max = mt_getrandmax();
 118                 $rand = mt_rand(0, $max) / $max * $sum;
 119
 120                 $sum = 0;
 121                 foreach ( $weights as $i => $w ) {
 122                         $sum += $w;
 123                         if ( $sum >= $rand ) {
 124                                 break;
 125                         }
 126                 }
 127                 return $i;
 128         }
 129
 130         function getRandomNonLagged( $loads, $wiki = false ) {
 131                 # Unset excessively lagged servers
 132                 $lags = $this->getLagTimes( $wiki );
 133                 foreach ( $lags as $i => $lag ) {
 134                         if ( $i != 0 && isset( $this->mServers[$i]['max lag'] ) ) {
 135                                 if ( $lag === false ) {
 136                                         wfDebug( "Server #$i is not replicating\n" );
 137                                         unset( $loads[$i] );
 138                                 } elseif ( $lag > $this->mServers[$i]['max lag'] ) {
 139                                         wfDebug( "Server #$i is excessively lagged ($lag seconds)\n" );
 140                                         unset( $loads[$i] );
 141                                 }
 142                         }
 143                 }
 144
 145                 # Find out if all the slaves with non-zero load are lagged
 146                 $sum = 0;
 147                 foreach ( $loads as $load ) {
 148                         $sum += $load;
 149                 }
 150                 if ( $sum == 0 ) {
 151                         # No appropriate DB servers except maybe the master and some slaves with zero load
 152                         # Do NOT use the master
 153                         # Instead, this function will return false, triggering read-only mode,
 154                         # and a lagged slave will be used instead.
 155                         return false;
 156                 }
 157
 158                 if ( count( $loads ) == 0 ) {
 159                         return false;
 160                 }
 161
 162                 #wfDebugLog( 'connect', var_export( $loads, true ) );
 163
 164                 # Return a random representative of the remainder
 165                 return $this->pickRandom( $loads );
 166         }
 167
 168         /**
 169          * Get the index of the reader connection, which may be a slave
 170          * This takes into account load ratios and lag times. It should
 171          * always return a consistent index during a given invocation
 172          *
 173          * Side effect: opens connections to databases
 174          */
 175         function getReaderIndex( $group = false, $wiki = false ) {
 176                 global $wgReadOnly, $wgDBClusterTimeout, $wgDBAvgStatusPoll, $wgDBtype;
 177
 178                 # FIXME: For now, only go through all this for mysql databases
 179                 if ($wgDBtype != 'mysql') {
 180                         return $this->getWriterIndex();
 181                 }
 182
 183                 if ( count( $this->mServers ) == 1 )  {
 184                         # Skip the load balancing if there's only one server
 185                         return 0;
 186                 } elseif ( $group === false and $this->mReadIndex >= 0 ) {
 187                         # Shortcut if generic reader exists already
 188                         return $this->mReadIndex;
 189                 }
 190
 191                 wfProfileIn( __METHOD__ );
 192
 193                 $totalElapsed = 0;
 194
 195                 # convert from seconds to microseconds
 196                 $timeout = $wgDBClusterTimeout * 1e6;
 197
 198                 # Find the relevant load array
 199                 if ( $group !== false ) {
 200                         if ( isset( $this->mGroupLoads[$group] ) ) {
 201                                 $nonErrorLoads = $this->mGroupLoads[$group];
 202                         } else {
 203                                 # No loads for this group, return false and the caller can use some other group
 204                                 wfDebug( __METHOD__.": no loads for group $group\n" );
 205                                 wfProfileOut( __METHOD__ );
 206                                 return false;
 207                         }
 208                 } else {
 209                         $nonErrorLoads = $this->mLoads;
 210                 }
 211
 212                 if ( !$nonErrorLoads ) {
 213                         throw new MWException( "Empty server array given to LoadBalancer" );
 214                 }
 215
 216                 # Scale the configured load ratios according to the dynamic load (if the load monitor supports it)
 217                 $this->getLoadMonitor()->scaleLoads( $nonErrorLoads, $group, $wiki );
 218
 219                 $i = false;
 220                 $found = false;
 221                 $laggedSlaveMode = false;
 222
 223                 # First try quickly looking through the available servers for a server that
 224                 # meets our criteria
 225                 do {
 226                         $totalThreadsConnected = 0;
 227                         $overloadedServers = 0;
 228                         $currentLoads = $nonErrorLoads;
 229                         while ( count( $currentLoads ) ) {
 230                                 if ( $wgReadOnly || $this->mAllowLagged || $laggedSlaveMode ) {
 231                                         $i = $this->pickRandom( $currentLoads );
 232                                 } else {
 233                                         $i = $this->getRandomNonLagged( $currentLoads, $wiki );
 234                                         if ( $i === false && count( $currentLoads ) != 0 )  {
 235                                                 # All slaves lagged. Switch to read-only mode
 236                                                 $wgReadOnly = wfMsgNoDBForContent( 'readonly_lag' );
 237                                                 $i = $this->pickRandom( $currentLoads );
 238                                                 $laggedSlaveMode = true;
 239                                         }
 240                                 }
 241
 242                                 if ( $i === false ) {
 243                                         # pickRandom() returned false
 244                                         # This is permanent and means the configuration or the load monitor
 245                                         # wants us to return false.
 246                                         wfDebugLog( 'connect', __METHOD__.": pickRandom() returned false\n" );
 247                                         wfProfileOut( __METHOD__ );
 248                                         return false;
 249                                 }
 250
 251                                 wfDebugLog( 'connect', __METHOD__.": Using reader #$i: {$this->mServers[$i]['host']}...\n" );
 252                                 $conn = $this->openConnection( $i, $wiki );
 253
 254                                 if ( !$conn ) {
 255                                         wfDebugLog( 'connect', __METHOD__.": Failed connecting to $i/$wiki\n" );
 256                                         unset( $nonErrorLoads[$i] );
 257                                         unset( $currentLoads[$i] );
 258                                         continue;
 259                                 }
 260
 261                                 // Perform post-connection backoff
 262                                 $threshold = isset( $this->mServers[$i]['max threads'] )
 263                                         ? $this->mServers[$i]['max threads'] : false;
 264                                 $backoff = $this->getLoadMonitor()->postConnectionBackoff( $conn, $threshold );
 265
 266                                 // Decrement reference counter, we are finished with this connection.
 267                                 // It will be incremented for the caller later.
 268                                 if ( $wiki !== false ) {
 269                                         $this->reuseConnection( $conn );
 270                                 }
 271
 272                                 if ( $backoff ) {
 273                                         # Post-connection overload, don't use this server for now
 274                                         $totalThreadsConnected += $backoff;
 275                                         $overloadedServers++;
 276                                         unset( $currentLoads[$i] );
 277                                 } else {
 278                                         # Return this server
 279                                         break 2;
 280                                 }
 281                         }
 282
 283                         # No server found yet
 284                         $i = false;
 285
 286                         # If all servers were down, quit now
 287                         if ( !count( $nonErrorLoads ) ) {
 288                                 wfDebugLog( 'connect', "All servers down\n" );
 289                                 break;
 290                         }
 291
 292                         # Some servers must have been overloaded
 293                         if ( $overloadedServers == 0 ) {
 294                                 throw new MWException( __METHOD__.": unexpectedly found no overloaded servers" );
 295                         }
 296                         # Back off for a while
 297                         # Scale the sleep time by the number of connected threads, to produce a
 298                         # roughly constant global poll rate
 299                         $avgThreads = $totalThreadsConnected / $overloadedServers;
 300                         $totalElapsed += $this->sleep( $wgDBAvgStatusPoll * $avgThreads );
 301                 } while ( $totalElapsed < $timeout );
 302
 303                 if ( $totalElapsed >= $timeout ) {
 304                         wfDebugLog( 'connect', "All servers busy\n" );
 305                         $this->mErrorConnection = false;
 306                         $this->mLastError = 'All servers busy';
 307                 }
 308
 309                 if ( $i !== false ) {
 310                         # Slave connection successful
 311                         # Wait for the session master pos for a short time
 312                         if ( $this->mWaitForPos && $i > 0 ) {
 313                                 if ( !$this->doWait( $i ) ) {
 314                                         $this->mServers[$i]['slave pos'] = $conn->getSlavePos();
 315                                 }
 316                         }
 317                         if ( $this->mReadIndex <=0 && $this->mLoads[$i]>0 && $i !== false ) {
 318                                 $this->mReadIndex = $i;
 319                         }
 320                 }
 321                 wfProfileOut( __METHOD__ );
 322                 return $i;
 323         }
 324
 325         /**
 326          * Wait for a specified number of microseconds, and return the period waited
 327          */
 328         function sleep( $t ) {
 329                 wfProfileIn( __METHOD__ );
 330                 wfDebug( __METHOD__.": waiting $t us\n" );
 331                 usleep( $t );
 332                 wfProfileOut( __METHOD__ );
 333                 return $t;
 334         }
 335
 336         /**
 337          * Get a random server to use in a query group
 338          * @deprecated use getReaderIndex
 339          */
 340         function getGroupIndex( $group ) {
 341                 return $this->getReaderIndex( $group );
 342         }
 343
 344         /**
 345          * Set the master wait position
 346          * If a DB_SLAVE connection has been opened already, waits
 347          * Otherwise sets a variable telling it to wait if such a connection is opened
 348          */
 349         public function waitFor( $pos ) {
 350                 wfProfileIn( __METHOD__ );
 351                 $this->mWaitForPos = $pos;
 352                 $i = $this->mReadIndex;
 353
 354                 if ( $i > 0 ) {
 355                         if ( !$this->doWait( $i ) ) {
 356                                 $this->mServers[$i]['slave pos'] = $this->getAnyOpenConnection( $i )->getSlavePos();
 357                                 $this->mLaggedSlaveMode = true;
 358                         }
 359                 }
 360                 wfProfileOut( __METHOD__ );
 361         }
 362
 363         /**
 364          * Get any open connection to a given server index, local or foreign
 365          * Returns false if there is no connection open
 366          */
 367         function getAnyOpenConnection( $i ) {
 368                 foreach ( $this->mConns as $type => $conns ) {
 369                         if ( !empty( $conns[$i] ) ) {
 370                                 return reset( $conns[$i] );
 371                         }
 372                 }
 373                 return false;
 374         }
 375
 376         /**
 377          * Wait for a given slave to catch up to the master pos stored in $this
 378          */
 379         function doWait( $index ) {
 380                 # Find a connection to wait on
 381                 $conn = $this->getAnyOpenConnection( $index );
 382                 if ( !$conn ) {
 383                         wfDebug( __METHOD__ . ": no connection open\n" );
 384                         return false;
 385                 }
 386
 387                 wfDebug( __METHOD__.": Waiting for slave #$index to catch up...\n" );
 388                 $result = $conn->masterPosWait( $this->mWaitForPos, $this->mWaitTimeout );
 389
 390                 if ( $result == -1 || is_null( $result ) ) {
 391                         # Timed out waiting for slave, use master instead
 392                         wfDebug( __METHOD__.": Timed out waiting for slave #$index pos {$this->mWaitForPos}\n" );
 393                         return false;
 394                 } else {
 395                         wfDebug( __METHOD__.": Done\n" );
 396                         return true;
 397                 }
 398         }
 399
 400         /**
 401          * Get a connection by index
 402          * This is the main entry point for this class.
 403          *
 404          * @param $i Integer: server index
 405          * @param $groups Array: query groups
 406          * @param $wiki String: wiki ID
 407          *
 408          * @return DatabaseBase
 409          */
 410         public function &getConnection( $i, $groups = array(), $wiki = false ) {
 411                 wfProfileIn( __METHOD__ );
 412
 413                 if ( $i == DB_LAST ) {
 414                         throw new MWException( 'Attempt to call ' . __METHOD__ . ' with deprecated server index DB_LAST' );
 415                 } elseif ( $i === null || $i === false ) {
 416                         throw new MWException( 'Attempt to call ' . __METHOD__ . ' with invalid server index' );
 417                 }
 418
 419                 if ( $wiki === wfWikiID() ) {
 420                         $wiki = false;
 421                 }
 422
 423                 # Query groups
 424                 if ( $i == DB_MASTER ) {
 425                         $i = $this->getWriterIndex();
 426                 } elseif ( !is_array( $groups ) ) {
 427                         $groupIndex = $this->getReaderIndex( $groups, $wiki );
 428                         if ( $groupIndex !== false ) {
 429                                 $serverName = $this->getServerName( $groupIndex );
 430                                 wfDebug( __METHOD__.": using server $serverName for group $groups\n" );
 431                                 $i = $groupIndex;
 432                         }
 433                 } else {
 434                         foreach ( $groups as $group ) {
 435                                 $groupIndex = $this->getReaderIndex( $group, $wiki );
 436                                 if ( $groupIndex !== false ) {
 437                                         $serverName = $this->getServerName( $groupIndex );
 438                                         wfDebug( __METHOD__.": using server $serverName for group $group\n" );
 439                                         $i = $groupIndex;
 440                                         break;
 441                                 }
 442                         }
 443                 }
 444
 445                 # Operation-based index
 446                 if ( $i == DB_SLAVE ) {
 447                         $i = $this->getReaderIndex( false, $wiki );
 448                         # Couldn't find a working server in getReaderIndex()?
 449                         if ( $i === false ) {
 450                                 $this->mLastError = 'No working slave server: ' . $this->mLastError;
 451                                 $this->reportConnectionError( $this->mErrorConnection );
 452                                 return false;
 453                         }
 454                 }
 455
 456                 # Now we have an explicit index into the servers array
 457                 $conn = $this->openConnection( $i, $wiki );
 458                 if ( !$conn ) {
 459                         $this->reportConnectionError( $this->mErrorConnection );
 460                 }
 461
 462                 wfProfileOut( __METHOD__ );
 463                 return $conn;
 464         }
 465
 466         /**
 467          * Mark a foreign connection as being available for reuse under a different
 468          * DB name or prefix. This mechanism is reference-counted, and must be called
 469          * the same number of times as getConnection() to work.
 470          */
 471         public function reuseConnection( $conn ) {
 472                 $serverIndex = $conn->getLBInfo('serverIndex');
 473                 $refCount = $conn->getLBInfo('foreignPoolRefCount');
 474                 $dbName = $conn->getDBname();
 475                 $prefix = $conn->tablePrefix();
 476                 if ( strval( $prefix ) !== '' ) {
 477                         $wiki = "$dbName-$prefix";
 478                 } else {
 479                         $wiki = $dbName;
 480                 }
 481                 if ( $serverIndex === null || $refCount === null ) {
 482                         wfDebug( __METHOD__.": this connection was not opened as a foreign connection\n" );
 483                         /**
 484                          * This can happen in code like:
 485                          *   foreach ( $dbs as $db ) {
 486                          *     $conn = $lb->getConnection( DB_SLAVE, array(), $db );
 487                          *     ...
 488                          *     $lb->reuseConnection( $conn );
 489                          *   }
 490                          * When a connection to the local DB is opened in this way, reuseConnection()
 491                          * should be ignored
 492                          */
 493                         return;
 494                 }
 495                 if ( $this->mConns['foreignUsed'][$serverIndex][$wiki] !== $conn ) {
 496                         throw new MWException( __METHOD__.": connection not found, has the connection been freed already?" );
 497                 }
 498                 $conn->setLBInfo( 'foreignPoolRefCount', --$refCount );
 499                 if ( $refCount <= 0 ) {
 500                         $this->mConns['foreignFree'][$serverIndex][$wiki] = $conn;
 501                         unset( $this->mConns['foreignUsed'][$serverIndex][$wiki] );
 502                         wfDebug( __METHOD__.": freed connection $serverIndex/$wiki\n" );
 503                 } else {
 504                         wfDebug( __METHOD__.": reference count for $serverIndex/$wiki reduced to $refCount\n" );
 505                 }
 506         }
 507
 508         /**
 509          * Open a connection to the server given by the specified index
 510          * Index must be an actual index into the array.
 511          * If the server is already open, returns it.
 512          *
 513          * On error, returns false, and the connection which caused the
 514          * error will be available via $this->mErrorConnection.
 515          *
 516          * @param $i Integer: server index
 517          * @param $wiki String: wiki ID to open
 518          * @return DatabaseBase
 519          *
 520          * @access private
 521          */
 522         function openConnection( $i, $wiki = false ) {
 523                 wfProfileIn( __METHOD__ );
 524                 if ( $wiki !== false ) {
 525                         $conn = $this->openForeignConnection( $i, $wiki );
 526                         wfProfileOut( __METHOD__);
 527                         return $conn;
 528                 }
 529                 if ( isset( $this->mConns['local'][$i][0] ) ) {
 530                         $conn = $this->mConns['local'][$i][0];
 531                 } else {
 532                         $server = $this->mServers[$i];
 533                         $server['serverIndex'] = $i;
 534                         $conn = $this->reallyOpenConnection( $server, false );
 535                         if ( $conn->isOpen() ) {
 536                                 $this->mConns['local'][$i][0] = $conn;
 537                         } else {
 538                                 wfDebug( "Failed to connect to database $i at {$this->mServers[$i]['host']}\n" );
 539                                 $this->mErrorConnection = $conn;
 540                                 $conn = false;
 541                         }
 542                 }
 543                 wfProfileOut( __METHOD__ );
 544                 return $conn;
 545         }
 546
 547         /**
 548          * Open a connection to a foreign DB, or return one if it is already open.
 549          *
 550          * Increments a reference count on the returned connection which locks the
 551          * connection to the requested wiki. This reference count can be
 552          * decremented by calling reuseConnection().
 553          *
 554          * If a connection is open to the appropriate server already, but with the wrong
 555          * database, it will be switched to the right database and returned, as long as
 556          * it has been freed first with reuseConnection().
 557          *
 558          * On error, returns false, and the connection which caused the
 559          * error will be available via $this->mErrorConnection.
 560          *
 561          * @param $i Integer: server index
 562          * @param $wiki String: wiki ID to open
 563          * @return DatabaseBase
 564          */
 565         function openForeignConnection( $i, $wiki ) {
 566                 wfProfileIn(__METHOD__);
 567                 list( $dbName, $prefix ) = wfSplitWikiID( $wiki );
 568                 if ( isset( $this->mConns['foreignUsed'][$i][$wiki] ) ) {
 569                         // Reuse an already-used connection
 570                         $conn = $this->mConns['foreignUsed'][$i][$wiki];
 571                         wfDebug( __METHOD__.": reusing connection $i/$wiki\n" );
 572                 } elseif ( isset( $this->mConns['foreignFree'][$i][$wiki] ) ) {
 573                         // Reuse a free connection for the same wiki
 574                         $conn = $this->mConns['foreignFree'][$i][$wiki];
 575                         unset( $this->mConns['foreignFree'][$i][$wiki] );
 576                         $this->mConns['foreignUsed'][$i][$wiki] = $conn;
 577                         wfDebug( __METHOD__.": reusing free connection $i/$wiki\n" );
 578                 } elseif ( !empty( $this->mConns['foreignFree'][$i] ) ) {
 579                         // Reuse a connection from another wiki
 580                         $conn = reset( $this->mConns['foreignFree'][$i] );
 581                         $oldWiki = key( $this->mConns['foreignFree'][$i] );
 582
 583                         if ( !$conn->selectDB( $dbName ) ) {
 584                                 $this->mLastError = "Error selecting database $dbName on server " .
 585                                         $conn->getServer() . " from client host " . wfHostname() . "\n";
 586                                 $this->mErrorConnection = $conn;
 587                                 $conn = false;
 588                         } else {
 589                                 $conn->tablePrefix( $prefix );
 590                                 unset( $this->mConns['foreignFree'][$i][$oldWiki] );
 591                                 $this->mConns['foreignUsed'][$i][$wiki] = $conn;
 592                                 wfDebug( __METHOD__.": reusing free connection from $oldWiki for $wiki\n" );
 593                         }
 594                 } else {
 595                         // Open a new connection
 596                         $server = $this->mServers[$i];
 597                         $server['serverIndex'] = $i;
 598                         $server['foreignPoolRefCount'] = 0;
 599                         $conn = $this->reallyOpenConnection( $server, $dbName );
 600                         if ( !$conn->isOpen() ) {
 601                                 wfDebug( __METHOD__.": error opening connection for $i/$wiki\n" );
 602                                 $this->mErrorConnection = $conn;
 603                                 $conn = false;
 604                         } else {
 605                                 $conn->tablePrefix( $prefix );
 606                                 $this->mConns['foreignUsed'][$i][$wiki] = $conn;
 607                                 wfDebug( __METHOD__.": opened new connection for $i/$wiki\n" );
 608                         }
 609                 }
 610
 611                 // Increment reference count
 612                 if ( $conn ) {
 613                         $refCount = $conn->getLBInfo( 'foreignPoolRefCount' );
 614                         $conn->setLBInfo( 'foreignPoolRefCount', $refCount + 1 );
 615                 }
 616                 wfProfileOut(__METHOD__);
 617                 return $conn;
 618         }
 619
 620         /**
 621          * Test if the specified index represents an open connection
 622          *
 623          * @param $index Integer: server index
 624          * @access private
 625          */
 626         function isOpen( $index ) {
 627                 if( !is_integer( $index ) ) {
 628                         return false;
 629                 }
 630                 return (bool)$this->getAnyOpenConnection( $index );
 631         }
 632
 633         /**
 634          * Really opens a connection. Uncached.
 635          * Returns a Database object whether or not the connection was successful.
 636          * @access private
 637          */
 638         function reallyOpenConnection( $server, $dbNameOverride = false ) {
 639                 if( !is_array( $server ) ) {
 640                         throw new MWException( 'You must update your load-balancing configuration. See DefaultSettings.php entry for $wgDBservers.' );
 641                 }
 642
 643                 extract( $server );
 644                 if ( $dbNameOverride !== false ) {
 645                         $dbname = $dbNameOverride;
 646                 }
 647
 648                 # Get class for this database type
 649                 $class = 'Database' . ucfirst( $type );
 650
 651                 # Create object
 652                 wfDebug( "Connecting to $host $dbname...\n" );
 653                 $db = new $class( $host, $user, $password, $dbname, 1, $flags );
 654                 if ( $db->isOpen() ) {
 655                         wfDebug( "Connected\n" );
 656                 } else {
 657                         wfDebug( "Failed\n" );
 658                 }
 659                 $db->setLBInfo( $server );
 660                 if ( isset( $server['fakeSlaveLag'] ) ) {
 661                         $db->setFakeSlaveLag( $server['fakeSlaveLag'] );
 662                 }
 663                 if ( isset( $server['fakeMaster'] ) ) {
 664                         $db->setFakeMaster( true );
 665                 }
 666                 return $db;
 667         }
 668
 669         function reportConnectionError( &$conn ) {
 670                 wfProfileIn( __METHOD__ );
 671
 672                 if ( !is_object( $conn ) ) {
 673                         // No last connection, probably due to all servers being too busy
 674                         wfLogDBError( "LB failure with no last connection\n" );
 675                         $conn = new Database;
 676                         if ( $this->mFailFunction ) {
 677                                 $conn->failFunction( $this->mFailFunction );
 678                                 $conn->reportConnectionError( $this->mLastError );
 679                         } else {
 680                                 // If all servers were busy, mLastError will contain something sensible
 681                                 throw new DBConnectionError( $conn, $this->mLastError );
 682                         }
 683                 } else {
 684                         if ( $this->mFailFunction ) {
 685                                 $conn->failFunction( $this->mFailFunction );
 686                         } else {
 687                                 $conn->failFunction( false );
 688                         }
 689                         $server = $conn->getProperty( 'mServer' );
 690                         wfLogDBError( "Connection error: {$this->mLastError} ({$server})\n" );
 691                         $conn->reportConnectionError( "{$this->mLastError} ({$server})" );
 692                 }
 693                 wfProfileOut( __METHOD__ );
 694         }
 695
 696         function getWriterIndex() {
 697                 return 0;
 698         }
 699
 700         /**
 701          * Returns true if the specified index is a valid server index
 702          */
 703         function haveIndex( $i ) {
 704                 return array_key_exists( $i, $this->mServers );
 705         }
 706
 707         /**
 708          * Returns true if the specified index is valid and has non-zero load
 709          */
 710         function isNonZeroLoad( $i ) {
 711                 return array_key_exists( $i, $this->mServers ) && $this->mLoads[$i] != 0;
 712         }
 713
 714         /**
 715          * Get the number of defined servers (not the number of open connections)
 716          */
 717         function getServerCount() {
 718                 return count( $this->mServers );
 719         }
 720
 721         /**
 722          * Get the host name or IP address of the server with the specified index
 723          * Prefer a readable name if available.
 724          */
 725         function getServerName( $i ) {
 726                 if ( isset( $this->mServers[$i]['hostName'] ) ) {
 727                         return $this->mServers[$i]['hostName'];
 728                 } elseif ( isset( $this->mServers[$i]['host'] ) ) {
 729                         return $this->mServers[$i]['host'];
 730                 } else {
 731                         return '';
 732                 }
 733         }
 734
 735         /**
 736          * Return the server info structure for a given index, or false if the index is invalid.
 737          */
 738         function getServerInfo( $i ) {
 739                 if ( isset( $this->mServers[$i] ) ) {
 740                         return $this->mServers[$i];
 741                 } else {
 742                         return false;
 743                 }
 744         }
 745
 746         /**
 747          * Get the current master position for chronology control purposes
 748          * @return mixed
 749          */
 750         function getMasterPos() {
 751                 # If this entire request was served from a slave without opening a connection to the
 752                 # master (however unlikely that may be), then we can fetch the position from the slave.
 753                 $masterConn = $this->getAnyOpenConnection( 0 );
 754                 if ( !$masterConn ) {
 755                         for ( $i = 1; $i < count( $this->mServers ); $i++ ) {
 756                                 $conn = $this->getAnyOpenConnection( $i );
 757                                 if ( $conn ) {
 758                                         wfDebug( "Master pos fetched from slave\n" );
 759                                         return $conn->getSlavePos();
 760                                 }
 761                         }
 762                 } else {
 763                         wfDebug( "Master pos fetched from master\n" );
 764                         return $masterConn->getMasterPos();
 765                 }
 766                 return false;
 767         }
 768
 769         /**
 770          * Close all open connections
 771          */
 772         function closeAll() {
 773                 foreach ( $this->mConns as $conns2 ) {
 774                         foreach  ( $conns2 as $conns3 ) {
 775                                 foreach ( $conns3 as $conn ) {
 776                                         $conn->close();
 777                                 }
 778                         }
 779                 }
 780                 $this->mConns = array(
 781                         'local' => array(),
 782                         'foreignFree' => array(),
 783                         'foreignUsed' => array(),
 784                 );
 785         }
 786
 787         /**
 788          * Close a connection
 789          * Using this function makes sure the LoadBalancer knows the connection is closed.
 790          * If you use $conn->close() directly, the load balancer won't update its state.
 791          */
 792         function closeConnecton( $conn ) {
 793                 $done = false;
 794                 foreach ( $this->mConns as $i1 => $conns2 ) {
 795                         foreach ( $conns2 as $i2 => $conns3 ) {
 796                                 foreach ( $conns3 as $i3 => $candidateConn ) {
 797                                         if ( $conn === $candidateConn ) {
 798                                                 $conn->close();
 799                                                 unset( $this->mConns[$i1][$i2][$i3] );
 800                                                 $done = true;
 801                                                 break;
 802                                         }
 803                                 }
 804                         }
 805                 }
 806                 if ( !$done ) {
 807                         $conn->close();
 808                 }
 809         }
 810
 811         /**
 812          * Commit transactions on all open connections
 813          */
 814         function commitAll() {
 815                 foreach ( $this->mConns as $conns2 ) {
 816                         foreach ( $conns2 as $conns3 ) {
 817                                 foreach ( $conns3 as $conn ) {
 818                                         $conn->commit();
 819                                 }
 820                         }
 821                 }
 822         }
 823
 824         /* Issue COMMIT only on master, only if queries were done on connection */
 825         function commitMasterChanges() {
 826                 // Always 0, but who knows.. :)
 827                 $masterIndex = $this->getWriterIndex();
 828                 foreach ( $this->mConns as $type => $conns2 ) {
 829                         if ( empty( $conns2[$masterIndex] ) ) {
 830                                 continue;
 831                         }
 832                         foreach ( $conns2[$masterIndex] as $conn ) {
 833                                 if ( $conn->doneWrites() ) {
 834                                         $conn->commit();
 835                                 }
 836                         }
 837                 }
 838         }
 839
 840         function waitTimeout( $value = null ) {
 841                 return wfSetVar( $this->mWaitTimeout, $value );
 842         }
 843
 844         function getLaggedSlaveMode() {
 845                 return $this->mLaggedSlaveMode;
 846         }
 847
 848         /* Disables/enables lag checks */
 849         function allowLagged($mode=null) {
 850                 if ($mode===null)
 851                         return $this->mAllowLagged;
 852                 $this->mAllowLagged=$mode;
 853         }
 854
 855         function pingAll() {
 856                 $success = true;
 857                 foreach ( $this->mConns as $conns2 ) {
 858                         foreach ( $conns2 as $conns3 ) {
 859                                 foreach ( $conns3 as $conn ) {
 860                                         if ( !$conn->ping() ) {
 861                                                 $success = false;
 862                                         }
 863                                 }
 864                         }
 865                 }
 866                 return $success;
 867         }
 868
 869         /**
 870          * Call a function with each open connection object
 871          */
 872         function forEachOpenConnection( $callback, $params = array() ) {
 873                 foreach ( $this->mConns as $conns2 ) {
 874                         foreach ( $conns2 as $conns3 ) {
 875                                 foreach ( $conns3 as $conn ) {
 876                                         $mergedParams = array_merge( array( $conn ), $params );
 877                                         call_user_func_array( $callback, $mergedParams );
 878                                 }
 879                         }
 880                 }
 881         }
 882
 883         /**
 884          * Get the hostname and lag time of the most-lagged slave.
 885          * This is useful for maintenance scripts that need to throttle their updates.
 886          * May attempt to open connections to slaves on the default DB.
 887          * @param $wiki string Wiki ID, or false for the default database
 888          */
 889         function getMaxLag( $wiki = false ) {
 890                 $maxLag = -1;
 891                 $host = '';
 892                 foreach ( $this->mServers as $i => $conn ) {
 893                         $conn = false;
 894                         if ( $wiki === false ) {
 895                                 $conn = $this->getAnyOpenConnection( $i );
 896                         }
 897                         if ( !$conn ) {
 898                                 $conn = $this->openConnection( $i, $wiki );
 899                         }
 900                         if ( !$conn ) {
 901                                 continue;
 902                         }
 903                         $lag = $conn->getLag();
 904                         if ( $lag > $maxLag ) {
 905                                 $maxLag = $lag;
 906                                 $host = $this->mServers[$i]['host'];
 907                         }
 908                 }
 909                 return array( $host, $maxLag );
 910         }
 911
 912         /**
 913          * Get lag time for each server
 914          * Results are cached for a short time in memcached, and indefinitely in the process cache
 915          */
 916         function getLagTimes( $wiki = false ) {
 917                 # Try process cache
 918                 if ( isset( $this->mLagTimes ) ) {
 919                         return $this->mLagTimes;
 920                 }
 921                 # No, send the request to the load monitor
 922                 $this->mLagTimes = $this->getLoadMonitor()->getLagTimes( array_keys( $this->mServers ), $wiki );
 923                 return $this->mLagTimes;
 924         }
 925
 926         /**
 927          * Clear the cache for getLagTimes
 928          */
 929         function clearLagTimeCache() {
 930                 $this->mLagTimes = null;
 931         }
 932 }