includes/libs/rdbms/loadbalancer/LoadBalancer.php

   1 <?php
   2 /**
   3  * Database load balancing manager
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License as published by
   7  * the Free Software Foundation; either version 2 of the License, or
   8  * (at your option) any later version.
   9  *
  10  * This program is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  13  * GNU General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU General Public License along
  16  * with this program; if not, write to the Free Software Foundation, Inc.,
  17  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  18  * http://www.gnu.org/copyleft/gpl.html
  19  *
  20  * @file
  21  * @ingroup Database
  22  */
  23 use Psr\Log\LoggerInterface;
  24
  25 /**
  26  * Database load balancing, tracking, and transaction management object
  27  *
  28  * @ingroup Database
  29  */
  30 class LoadBalancer implements ILoadBalancer {
  31         /** @var array[] Map of (server index => server config array) */
  32         private $mServers;
  33         /** @var array[] Map of (local/foreignUsed/foreignFree => server index => IDatabase array) */
  34         private $mConns;
  35         /** @var array Map of (server index => weight) */
  36         private $mLoads;
  37         /** @var array[] Map of (group => server index => weight) */
  38         private $mGroupLoads;
  39         /** @var bool Whether to disregard replica DB lag as a factor in replica DB selection */
  40         private $mAllowLagged;
  41         /** @var integer Seconds to spend waiting on replica DB lag to resolve */
  42         private $mWaitTimeout;
  43         /** @var string The LoadMonitor subclass name */
  44         private $mLoadMonitorClass;
  45
  46         /** @var LoadMonitor */
  47         private $mLoadMonitor;
  48         /** @var BagOStuff */
  49         private $srvCache;
  50         /** @var BagOStuff */
  51         private $memCache;
  52         /** @var WANObjectCache */
  53         private $wanCache;
  54         /** @var TransactionProfiler */
  55         protected $trxProfiler;
  56         /** @var LoggerInterface */
  57         protected $replLogger;
  58         /** @var LoggerInterface */
  59         protected $connLogger;
  60         /** @var LoggerInterface */
  61         protected $queryLogger;
  62         /** @var LoggerInterface */
  63         protected $perfLogger;
  64
  65         /** @var bool|IDatabase Database connection that caused a problem */
  66         private $mErrorConnection;
  67         /** @var integer The generic (not query grouped) replica DB index (of $mServers) */
  68         private $mReadIndex;
  69         /** @var bool|DBMasterPos False if not set */
  70         private $mWaitForPos;
  71         /** @var bool Whether the generic reader fell back to a lagged replica DB */
  72         private $laggedReplicaMode = false;
  73         /** @var bool Whether the generic reader fell back to a lagged replica DB */
  74         private $allReplicasDownMode = false;
  75         /** @var string The last DB selection or connection error */
  76         private $mLastError = 'Unknown error';
  77         /** @var string|bool Reason the LB is read-only or false if not */
  78         private $readOnlyReason = false;
  79         /** @var integer Total connections opened */
  80         private $connsOpened = 0;
  81         /** @var string|bool String if a requested DBO_TRX transaction round is active */
  82         private $trxRoundId = false;
  83         /** @var array[] Map of (name => callable) */
  84         private $trxRecurringCallbacks = [];
  85         /** @var string Local Domain ID and default for selectDB() calls */
  86         private $localDomain;
  87         /** @var string Current server name */
  88         private $host;
  89
  90         /** @var callable Exception logger */
  91         private $errorLogger;
  92
  93         /** @var boolean */
  94         private $disabled = false;
  95
  96         /** @var integer Warn when this many connection are held */
  97         const CONN_HELD_WARN_THRESHOLD = 10;
  98         /** @var integer Default 'max lag' when unspecified */
  99         const MAX_LAG_DEFAULT = 10;
 100         /** @var integer Max time to wait for a replica DB to catch up (e.g. ChronologyProtector) */
 101         const POS_WAIT_TIMEOUT = 10;
 102         /** @var integer Seconds to cache master server read-only status */
 103         const TTL_CACHE_READONLY = 5;
 104
 105         public function __construct( array $params ) {
 106                 if ( !isset( $params['servers'] ) ) {
 107                         throw new InvalidArgumentException( __CLASS__ . ': missing servers parameter' );
 108                 }
 109                 $this->mServers = $params['servers'];
 110                 $this->mWaitTimeout = isset( $params['waitTimeout'] )
 111                         ? $params['waitTimeout']
 112                         : self::POS_WAIT_TIMEOUT;
 113                 $this->localDomain = isset( $params['localDomain'] ) ? $params['localDomain'] : '';
 114
 115                 $this->mReadIndex = -1;
 116                 $this->mConns = [
 117                         'local' => [],
 118                         'foreignUsed' => [],
 119                         'foreignFree' => [] ];
 120                 $this->mLoads = [];
 121                 $this->mWaitForPos = false;
 122                 $this->mErrorConnection = false;
 123                 $this->mAllowLagged = false;
 124
 125                 if ( isset( $params['readOnlyReason'] ) && is_string( $params['readOnlyReason'] ) ) {
 126                         $this->readOnlyReason = $params['readOnlyReason'];
 127                 }
 128
 129                 if ( isset( $params['loadMonitor'] ) ) {
 130                         $this->mLoadMonitorClass = $params['loadMonitor'];
 131                 } else {
 132                         $master = reset( $params['servers'] );
 133                         if ( isset( $master['type'] ) && $master['type'] === 'mysql' ) {
 134                                 $this->mLoadMonitorClass = 'LoadMonitorMySQL';
 135                         } else {
 136                                 $this->mLoadMonitorClass = 'LoadMonitorNull';
 137                         }
 138                 }
 139
 140                 foreach ( $params['servers'] as $i => $server ) {
 141                         $this->mLoads[$i] = $server['load'];
 142                         if ( isset( $server['groupLoads'] ) ) {
 143                                 foreach ( $server['groupLoads'] as $group => $ratio ) {
 144                                         if ( !isset( $this->mGroupLoads[$group] ) ) {
 145                                                 $this->mGroupLoads[$group] = [];
 146                                         }
 147                                         $this->mGroupLoads[$group][$i] = $ratio;
 148                                 }
 149                         }
 150                 }
 151
 152                 if ( isset( $params['srvCache'] ) ) {
 153                         $this->srvCache = $params['srvCache'];
 154                 } else {
 155                         $this->srvCache = new EmptyBagOStuff();
 156                 }
 157                 if ( isset( $params['memCache'] ) ) {
 158                         $this->memCache = $params['memCache'];
 159                 } else {
 160                         $this->memCache = new EmptyBagOStuff();
 161                 }
 162                 if ( isset( $params['wanCache'] ) ) {
 163                         $this->wanCache = $params['wanCache'];
 164                 } else {
 165                         $this->wanCache = WANObjectCache::newEmpty();
 166                 }
 167                 if ( isset( $params['trxProfiler'] ) ) {
 168                         $this->trxProfiler = $params['trxProfiler'];
 169                 } else {
 170                         $this->trxProfiler = new TransactionProfiler();
 171                 }
 172
 173                 $this->errorLogger = isset( $params['errorLogger'] )
 174                         ? $params['errorLogger']
 175                         : function ( Exception $e ) {
 176                                 trigger_error( E_WARNING, $e->getMessage() );
 177                         };
 178
 179                 foreach ( [ 'replLogger', 'connLogger', 'queryLogger', 'perfLogger' ] as $key ) {
 180                         $this->$key = isset( $params[$key] ) ? $params[$key] : new \Psr\Log\NullLogger();
 181                 }
 182
 183                 $this->host = isset( $params['hostname'] )
 184                         ? $params['hostname']
 185                         : ( gethostname() ?: 'unknown' );
 186         }
 187
 188         /**
 189          * Get a LoadMonitor instance
 190          *
 191          * @return LoadMonitor
 192          */
 193         private function getLoadMonitor() {
 194                 if ( !isset( $this->mLoadMonitor ) ) {
 195                         $class = $this->mLoadMonitorClass;
 196                         $this->mLoadMonitor = new $class( $this, $this->srvCache, $this->memCache );
 197                         $this->mLoadMonitor->setLogger( $this->replLogger );
 198                 }
 199
 200                 return $this->mLoadMonitor;
 201         }
 202
 203         /**
 204          * @param array $loads
 205          * @param bool|string $domain Domain to get non-lagged for
 206          * @param int $maxLag Restrict the maximum allowed lag to this many seconds
 207          * @return bool|int|string
 208          */
 209         private function getRandomNonLagged( array $loads, $domain = false, $maxLag = INF ) {
 210                 $lags = $this->getLagTimes( $domain );
 211
 212                 # Unset excessively lagged servers
 213                 foreach ( $lags as $i => $lag ) {
 214                         if ( $i != 0 ) {
 215                                 # How much lag this server nominally is allowed to have
 216                                 $maxServerLag = isset( $this->mServers[$i]['max lag'] )
 217                                         ? $this->mServers[$i]['max lag']
 218                                         : self::MAX_LAG_DEFAULT; // default
 219                                 # Constrain that futher by $maxLag argument
 220                                 $maxServerLag = min( $maxServerLag, $maxLag );
 221
 222                                 $host = $this->getServerName( $i );
 223                                 if ( $lag === false && !is_infinite( $maxServerLag ) ) {
 224                                         $this->replLogger->error( "Server $host (#$i) is not replicating?" );
 225                                         unset( $loads[$i] );
 226                                 } elseif ( $lag > $maxServerLag ) {
 227                                         $this->replLogger->warning( "Server $host (#$i) has >= $lag seconds of lag" );
 228                                         unset( $loads[$i] );
 229                                 }
 230                         }
 231                 }
 232
 233                 # Find out if all the replica DBs with non-zero load are lagged
 234                 $sum = 0;
 235                 foreach ( $loads as $load ) {
 236                         $sum += $load;
 237                 }
 238                 if ( $sum == 0 ) {
 239                         # No appropriate DB servers except maybe the master and some replica DBs with zero load
 240                         # Do NOT use the master
 241                         # Instead, this function will return false, triggering read-only mode,
 242                         # and a lagged replica DB will be used instead.
 243                         return false;
 244                 }
 245
 246                 if ( count( $loads ) == 0 ) {
 247                         return false;
 248                 }
 249
 250                 # Return a random representative of the remainder
 251                 return ArrayUtils::pickRandom( $loads );
 252         }
 253
 254         public function getReaderIndex( $group = false, $domain = false ) {
 255                 if ( count( $this->mServers ) == 1 ) {
 256                         # Skip the load balancing if there's only one server
 257                         return $this->getWriterIndex();
 258                 } elseif ( $group === false && $this->mReadIndex >= 0 ) {
 259                         # Shortcut if generic reader exists already
 260                         return $this->mReadIndex;
 261                 }
 262
 263                 # Find the relevant load array
 264                 if ( $group !== false ) {
 265                         if ( isset( $this->mGroupLoads[$group] ) ) {
 266                                 $nonErrorLoads = $this->mGroupLoads[$group];
 267                         } else {
 268                                 # No loads for this group, return false and the caller can use some other group
 269                                 $this->connLogger->info( __METHOD__ . ": no loads for group $group" );
 270
 271                                 return false;
 272                         }
 273                 } else {
 274                         $nonErrorLoads = $this->mLoads;
 275                 }
 276
 277                 if ( !count( $nonErrorLoads ) ) {
 278                         throw new InvalidArgumentException( "Empty server array given to LoadBalancer" );
 279                 }
 280
 281                 # Scale the configured load ratios according to the dynamic load if supported
 282                 $this->getLoadMonitor()->scaleLoads( $nonErrorLoads, $group, $domain );
 283
 284                 $laggedReplicaMode = false;
 285
 286                 # No server found yet
 287                 $i = false;
 288                 # First try quickly looking through the available servers for a server that
 289                 # meets our criteria
 290                 $currentLoads = $nonErrorLoads;
 291                 while ( count( $currentLoads ) ) {
 292                         if ( $this->mAllowLagged || $laggedReplicaMode ) {
 293                                 $i = ArrayUtils::pickRandom( $currentLoads );
 294                         } else {
 295                                 $i = false;
 296                                 if ( $this->mWaitForPos && $this->mWaitForPos->asOfTime() ) {
 297                                         # ChronologyProtecter causes mWaitForPos to be set via sessions.
 298                                         # This triggers doWait() after connect, so it's especially good to
 299                                         # avoid lagged servers so as to avoid just blocking in that method.
 300                                         $ago = microtime( true ) - $this->mWaitForPos->asOfTime();
 301                                         # Aim for <= 1 second of waiting (being too picky can backfire)
 302                                         $i = $this->getRandomNonLagged( $currentLoads, $domain, $ago + 1 );
 303                                 }
 304                                 if ( $i === false ) {
 305                                         # Any server with less lag than it's 'max lag' param is preferable
 306                                         $i = $this->getRandomNonLagged( $currentLoads, $domain );
 307                                 }
 308                                 if ( $i === false && count( $currentLoads ) != 0 ) {
 309                                         # All replica DBs lagged. Switch to read-only mode
 310                                         $this->replLogger->error( "All replica DBs lagged. Switch to read-only mode" );
 311                                         $i = ArrayUtils::pickRandom( $currentLoads );
 312                                         $laggedReplicaMode = true;
 313                                 }
 314                         }
 315
 316                         if ( $i === false ) {
 317                                 # pickRandom() returned false
 318                                 # This is permanent and means the configuration or the load monitor
 319                                 # wants us to return false.
 320                                 $this->connLogger->debug( __METHOD__ . ": pickRandom() returned false" );
 321
 322                                 return false;
 323                         }
 324
 325                         $serverName = $this->getServerName( $i );
 326                         $this->connLogger->debug( __METHOD__ . ": Using reader #$i: $serverName..." );
 327
 328                         $conn = $this->openConnection( $i, $domain );
 329                         if ( !$conn ) {
 330                                 $this->connLogger->warning( __METHOD__ . ": Failed connecting to $i/$domain" );
 331                                 unset( $nonErrorLoads[$i] );
 332                                 unset( $currentLoads[$i] );
 333                                 $i = false;
 334                                 continue;
 335                         }
 336
 337                         // Decrement reference counter, we are finished with this connection.
 338                         // It will be incremented for the caller later.
 339                         if ( $domain !== false ) {
 340                                 $this->reuseConnection( $conn );
 341                         }
 342
 343                         # Return this server
 344                         break;
 345                 }
 346
 347                 # If all servers were down, quit now
 348                 if ( !count( $nonErrorLoads ) ) {
 349                         $this->connLogger->error( "All servers down" );
 350                 }
 351
 352                 if ( $i !== false ) {
 353                         # Replica DB connection successful.
 354                         # Wait for the session master pos for a short time.
 355                         if ( $this->mWaitForPos && $i > 0 ) {
 356                                 $this->doWait( $i );
 357                         }
 358                         if ( $this->mReadIndex <= 0 && $this->mLoads[$i] > 0 && $group === false ) {
 359                                 $this->mReadIndex = $i;
 360                                 # Record if the generic reader index is in "lagged replica DB" mode
 361                                 if ( $laggedReplicaMode ) {
 362                                         $this->laggedReplicaMode = true;
 363                                 }
 364                         }
 365                         $serverName = $this->getServerName( $i );
 366                         $this->connLogger->debug(
 367                                 __METHOD__ . ": using server $serverName for group '$group'" );
 368                 }
 369
 370                 return $i;
 371         }
 372
 373         public function waitFor( $pos ) {
 374                 $this->mWaitForPos = $pos;
 375                 $i = $this->mReadIndex;
 376
 377                 if ( $i > 0 ) {
 378                         if ( !$this->doWait( $i ) ) {
 379                                 $this->laggedReplicaMode = true;
 380                         }
 381                 }
 382         }
 383
 384         /**
 385          * Set the master wait position and wait for a "generic" replica DB to catch up to it
 386          *
 387          * This can be used a faster proxy for waitForAll()
 388          *
 389          * @param DBMasterPos $pos
 390          * @param int $timeout Max seconds to wait; default is mWaitTimeout
 391          * @return bool Success (able to connect and no timeouts reached)
 392          * @since 1.26
 393          */
 394         public function waitForOne( $pos, $timeout = null ) {
 395                 $this->mWaitForPos = $pos;
 396
 397                 $i = $this->mReadIndex;
 398                 if ( $i <= 0 ) {
 399                         // Pick a generic replica DB if there isn't one yet
 400                         $readLoads = $this->mLoads;
 401                         unset( $readLoads[$this->getWriterIndex()] ); // replica DBs only
 402                         $readLoads = array_filter( $readLoads ); // with non-zero load
 403                         $i = ArrayUtils::pickRandom( $readLoads );
 404                 }
 405
 406                 if ( $i > 0 ) {
 407                         $ok = $this->doWait( $i, true, $timeout );
 408                 } else {
 409                         $ok = true; // no applicable loads
 410                 }
 411
 412                 return $ok;
 413         }
 414
 415         public function waitForAll( $pos, $timeout = null ) {
 416                 $this->mWaitForPos = $pos;
 417                 $serverCount = count( $this->mServers );
 418
 419                 $ok = true;
 420                 for ( $i = 1; $i < $serverCount; $i++ ) {
 421                         if ( $this->mLoads[$i] > 0 ) {
 422                                 $ok = $this->doWait( $i, true, $timeout ) && $ok;
 423                         }
 424                 }
 425
 426                 return $ok;
 427         }
 428
 429         public function getAnyOpenConnection( $i ) {
 430                 foreach ( $this->mConns as $connsByServer ) {
 431                         if ( !empty( $connsByServer[$i] ) ) {
 432                                 return reset( $connsByServer[$i] );
 433                         }
 434                 }
 435
 436                 return false;
 437         }
 438
 439         /**
 440          * Wait for a given replica DB to catch up to the master pos stored in $this
 441          * @param int $index Server index
 442          * @param bool $open Check the server even if a new connection has to be made
 443          * @param int $timeout Max seconds to wait; default is mWaitTimeout
 444          * @return bool
 445          */
 446         protected function doWait( $index, $open = false, $timeout = null ) {
 447                 $close = false; // close the connection afterwards
 448
 449                 // Check if we already know that the DB has reached this point
 450                 $server = $this->getServerName( $index );
 451                 $key = $this->srvCache->makeGlobalKey( __CLASS__, 'last-known-pos', $server );
 452                 /** @var DBMasterPos $knownReachedPos */
 453                 $knownReachedPos = $this->srvCache->get( $key );
 454                 if ( $knownReachedPos && $knownReachedPos->hasReached( $this->mWaitForPos ) ) {
 455                         $this->replLogger->debug( __METHOD__ .
 456                                 ": replica DB $server known to be caught up (pos >= $knownReachedPos)." );
 457                         return true;
 458                 }
 459
 460                 // Find a connection to wait on, creating one if needed and allowed
 461                 $conn = $this->getAnyOpenConnection( $index );
 462                 if ( !$conn ) {
 463                         if ( !$open ) {
 464                                 $this->replLogger->debug( __METHOD__ . ": no connection open for $server" );
 465
 466                                 return false;
 467                         } else {
 468                                 $conn = $this->openConnection( $index, '' );
 469                                 if ( !$conn ) {
 470                                         $this->replLogger->warning( __METHOD__ . ": failed to connect to $server" );
 471
 472                                         return false;
 473                                 }
 474                                 // Avoid connection spam in waitForAll() when connections
 475                                 // are made just for the sake of doing this lag check.
 476                                 $close = true;
 477                         }
 478                 }
 479
 480                 $this->replLogger->info( __METHOD__ . ": Waiting for replica DB $server to catch up..." );
 481                 $timeout = $timeout ?: $this->mWaitTimeout;
 482                 $result = $conn->masterPosWait( $this->mWaitForPos, $timeout );
 483
 484                 if ( $result == -1 || is_null( $result ) ) {
 485                         // Timed out waiting for replica DB, use master instead
 486                         $msg = __METHOD__ . ": Timed out waiting on $server pos {$this->mWaitForPos}";
 487                         $this->replLogger->warning( "$msg" );
 488                         $ok = false;
 489                 } else {
 490                         $this->replLogger->info( __METHOD__ . ": Done" );
 491                         $ok = true;
 492                         // Remember that the DB reached this point
 493                         $this->srvCache->set( $key, $this->mWaitForPos, BagOStuff::TTL_DAY );
 494                 }
 495
 496                 if ( $close ) {
 497                         $this->closeConnection( $conn );
 498                 }
 499
 500                 return $ok;
 501         }
 502
 503         public function getConnection( $i, $groups = [], $domain = false ) {
 504                 if ( $i === null || $i === false ) {
 505                         throw new InvalidArgumentException( 'Attempt to call ' . __METHOD__ .
 506                                 ' with invalid server index' );
 507                 }
 508
 509                 if ( $domain === $this->localDomain ) {
 510                         $domain = false;
 511                 }
 512
 513                 $groups = ( $groups === false || $groups === [] )
 514                         ? [ false ] // check one "group": the generic pool
 515                         : (array)$groups;
 516
 517                 $masterOnly = ( $i == DB_MASTER || $i == $this->getWriterIndex() );
 518                 $oldConnsOpened = $this->connsOpened; // connections open now
 519
 520                 if ( $i == DB_MASTER ) {
 521                         $i = $this->getWriterIndex();
 522                 } else {
 523                         # Try to find an available server in any the query groups (in order)
 524                         foreach ( $groups as $group ) {
 525                                 $groupIndex = $this->getReaderIndex( $group, $domain );
 526                                 if ( $groupIndex !== false ) {
 527                                         $i = $groupIndex;
 528                                         break;
 529                                 }
 530                         }
 531                 }
 532
 533                 # Operation-based index
 534                 if ( $i == DB_REPLICA ) {
 535                         $this->mLastError = 'Unknown error'; // reset error string
 536                         # Try the general server pool if $groups are unavailable.
 537                         $i = in_array( false, $groups, true )
 538                                 ? false // don't bother with this if that is what was tried above
 539                                 : $this->getReaderIndex( false, $domain );
 540                         # Couldn't find a working server in getReaderIndex()?
 541                         if ( $i === false ) {
 542                                 $this->mLastError = 'No working replica DB server: ' . $this->mLastError;
 543
 544                                 return $this->reportConnectionError();
 545                         }
 546                 }
 547
 548                 # Now we have an explicit index into the servers array
 549                 $conn = $this->openConnection( $i, $domain );
 550                 if ( !$conn ) {
 551                         return $this->reportConnectionError();
 552                 }
 553
 554                 # Profile any new connections that happen
 555                 if ( $this->connsOpened > $oldConnsOpened ) {
 556                         $host = $conn->getServer();
 557                         $dbname = $conn->getDBname();
 558                         $this->trxProfiler->recordConnection( $host, $dbname, $masterOnly );
 559                 }
 560
 561                 if ( $masterOnly ) {
 562                         # Make master-requested DB handles inherit any read-only mode setting
 563                         $conn->setLBInfo( 'readOnlyReason', $this->getReadOnlyReason( $domain, $conn ) );
 564                 }
 565
 566                 return $conn;
 567         }
 568
 569         public function reuseConnection( $conn ) {
 570                 $serverIndex = $conn->getLBInfo( 'serverIndex' );
 571                 $refCount = $conn->getLBInfo( 'foreignPoolRefCount' );
 572                 if ( $serverIndex === null || $refCount === null ) {
 573                         /**
 574                          * This can happen in code like:
 575                          *   foreach ( $dbs as $db ) {
 576                          *     $conn = $lb->getConnection( DB_REPLICA, [], $db );
 577                          *     ...
 578                          *     $lb->reuseConnection( $conn );
 579                          *   }
 580                          * When a connection to the local DB is opened in this way, reuseConnection()
 581                          * should be ignored
 582                          */
 583                         return;
 584                 }
 585
 586                 $dbName = $conn->getDBname();
 587                 $prefix = $conn->tablePrefix();
 588                 if ( strval( $prefix ) !== '' ) {
 589                         $domain = "$dbName-$prefix";
 590                 } else {
 591                         $domain = $dbName;
 592                 }
 593                 if ( $this->mConns['foreignUsed'][$serverIndex][$domain] !== $conn ) {
 594                         throw new InvalidArgumentException( __METHOD__ . ": connection not found, has " .
 595                                 "the connection been freed already?" );
 596                 }
 597                 $conn->setLBInfo( 'foreignPoolRefCount', --$refCount );
 598                 if ( $refCount <= 0 ) {
 599                         $this->mConns['foreignFree'][$serverIndex][$domain] = $conn;
 600                         unset( $this->mConns['foreignUsed'][$serverIndex][$domain] );
 601                         $this->connLogger->debug( __METHOD__ . ": freed connection $serverIndex/$domain" );
 602                 } else {
 603                         $this->connLogger->debug( __METHOD__ .
 604                                 ": reference count for $serverIndex/$domain reduced to $refCount" );
 605                 }
 606         }
 607
 608         /**
 609          * Get a database connection handle reference
 610          *
 611          * The handle's methods wrap simply wrap those of a IDatabase handle
 612          *
 613          * @see LoadBalancer::getConnection() for parameter information
 614          *
 615          * @param int $db
 616          * @param array|string|bool $groups Query group(s), or false for the generic reader
 617          * @param string|bool $domain Domain ID, or false for the current domain
 618          * @return DBConnRef
 619          * @since 1.22
 620          */
 621         public function getConnectionRef( $db, $groups = [], $domain = false ) {
 622                 return new DBConnRef( $this, $this->getConnection( $db, $groups, $domain ) );
 623         }
 624
 625         /**
 626          * Get a database connection handle reference without connecting yet
 627          *
 628          * The handle's methods wrap simply wrap those of a IDatabase handle
 629          *
 630          * @see LoadBalancer::getConnection() for parameter information
 631          *
 632          * @param int $db
 633          * @param array|string|bool $groups Query group(s), or false for the generic reader
 634          * @param string|bool $domain Domain ID, or false for the current domain
 635          * @return DBConnRef
 636          * @since 1.22
 637          */
 638         public function getLazyConnectionRef( $db, $groups = [], $domain = false ) {
 639                 $domain = ( $domain !== false ) ? $domain : $this->localDomain;
 640
 641                 return new DBConnRef( $this, [ $db, $groups, $domain ] );
 642         }
 643
 644         public function openConnection( $i, $domain = false ) {
 645                 if ( $domain !== false ) {
 646                         $conn = $this->openForeignConnection( $i, $domain );
 647                 } elseif ( isset( $this->mConns['local'][$i][0] ) ) {
 648                         $conn = $this->mConns['local'][$i][0];
 649                 } else {
 650                         $server = $this->mServers[$i];
 651                         $server['serverIndex'] = $i;
 652                         $conn = $this->reallyOpenConnection( $server, false );
 653                         $serverName = $this->getServerName( $i );
 654                         if ( $conn->isOpen() ) {
 655                                 $this->connLogger->debug( "Connected to database $i at '$serverName'." );
 656                                 $this->mConns['local'][$i][0] = $conn;
 657                         } else {
 658                                 $this->connLogger->warning( "Failed to connect to database $i at '$serverName'." );
 659                                 $this->mErrorConnection = $conn;
 660                                 $conn = false;
 661                         }
 662                 }
 663
 664                 if ( $conn && !$conn->isOpen() ) {
 665                         // Connection was made but later unrecoverably lost for some reason.
 666                         // Do not return a handle that will just throw exceptions on use,
 667                         // but let the calling code (e.g. getReaderIndex) try another server.
 668                         // See DatabaseMyslBase::ping() for how this can happen.
 669                         $this->mErrorConnection = $conn;
 670                         $conn = false;
 671                 }
 672
 673                 return $conn;
 674         }
 675
 676         /**
 677          * Open a connection to a foreign DB, or return one if it is already open.
 678          *
 679          * Increments a reference count on the returned connection which locks the
 680          * connection to the requested domain. This reference count can be
 681          * decremented by calling reuseConnection().
 682          *
 683          * If a connection is open to the appropriate server already, but with the wrong
 684          * database, it will be switched to the right database and returned, as long as
 685          * it has been freed first with reuseConnection().
 686          *
 687          * On error, returns false, and the connection which caused the
 688          * error will be available via $this->mErrorConnection.
 689          *
 690          * @note If disable() was called on this LoadBalancer, this method will throw a DBAccessError.
 691          *
 692          * @param int $i Server index
 693          * @param string $domain Domain ID to open
 694          * @return IDatabase
 695          */
 696         private function openForeignConnection( $i, $domain ) {
 697                 list( $dbName, $prefix ) = explode( '-', $domain, 2 ) + [ '', '' ];
 698
 699                 if ( isset( $this->mConns['foreignUsed'][$i][$domain] ) ) {
 700                         // Reuse an already-used connection
 701                         $conn = $this->mConns['foreignUsed'][$i][$domain];
 702                         $this->connLogger->debug( __METHOD__ . ": reusing connection $i/$domain" );
 703                 } elseif ( isset( $this->mConns['foreignFree'][$i][$domain] ) ) {
 704                         // Reuse a free connection for the same domain
 705                         $conn = $this->mConns['foreignFree'][$i][$domain];
 706                         unset( $this->mConns['foreignFree'][$i][$domain] );
 707                         $this->mConns['foreignUsed'][$i][$domain] = $conn;
 708                         $this->connLogger->debug( __METHOD__ . ": reusing free connection $i/$domain" );
 709                 } elseif ( !empty( $this->mConns['foreignFree'][$i] ) ) {
 710                         // Reuse a connection from another domain
 711                         $conn = reset( $this->mConns['foreignFree'][$i] );
 712                         $oldDomain = key( $this->mConns['foreignFree'][$i] );
 713
 714                         // The empty string as a DB name means "don't care".
 715                         // DatabaseMysqlBase::open() already handle this on connection.
 716                         if ( $dbName !== '' && !$conn->selectDB( $dbName ) ) {
 717                                 $this->mLastError = "Error selecting database $dbName on server " .
 718                                         $conn->getServer() . " from client host {$this->host}";
 719                                 $this->mErrorConnection = $conn;
 720                                 $conn = false;
 721                         } else {
 722                                 $conn->tablePrefix( $prefix );
 723                                 unset( $this->mConns['foreignFree'][$i][$oldDomain] );
 724                                 $this->mConns['foreignUsed'][$i][$domain] = $conn;
 725                                 $this->connLogger->debug( __METHOD__ .
 726                                         ": reusing free connection from $oldDomain for $domain" );
 727                         }
 728                 } else {
 729                         // Open a new connection
 730                         $server = $this->mServers[$i];
 731                         $server['serverIndex'] = $i;
 732                         $server['foreignPoolRefCount'] = 0;
 733                         $server['foreign'] = true;
 734                         $conn = $this->reallyOpenConnection( $server, $dbName );
 735                         if ( !$conn->isOpen() ) {
 736                                 $this->connLogger->warning( __METHOD__ . ": connection error for $i/$domain" );
 737                                 $this->mErrorConnection = $conn;
 738                                 $conn = false;
 739                         } else {
 740                                 $conn->tablePrefix( $prefix );
 741                                 $this->mConns['foreignUsed'][$i][$domain] = $conn;
 742                                 $this->connLogger->debug( __METHOD__ . ": opened new connection for $i/$domain" );
 743                         }
 744                 }
 745
 746                 // Increment reference count
 747                 if ( $conn ) {
 748                         $refCount = $conn->getLBInfo( 'foreignPoolRefCount' );
 749                         $conn->setLBInfo( 'foreignPoolRefCount', $refCount + 1 );
 750                 }
 751
 752                 return $conn;
 753         }
 754
 755         /**
 756          * Test if the specified index represents an open connection
 757          *
 758          * @param int $index Server index
 759          * @access private
 760          * @return bool
 761          */
 762         private function isOpen( $index ) {
 763                 if ( !is_integer( $index ) ) {
 764                         return false;
 765                 }
 766
 767                 return (bool)$this->getAnyOpenConnection( $index );
 768         }
 769
 770         /**
 771          * Really opens a connection. Uncached.
 772          * Returns a Database object whether or not the connection was successful.
 773          * @access private
 774          *
 775          * @param array $server
 776          * @param bool $dbNameOverride
 777          * @return IDatabase
 778          * @throws DBAccessError
 779          * @throws InvalidArgumentException
 780          */
 781         protected function reallyOpenConnection( $server, $dbNameOverride = false ) {
 782                 if ( $this->disabled ) {
 783                         throw new DBAccessError();
 784                 }
 785
 786                 if ( !is_array( $server ) ) {
 787                         throw new InvalidArgumentException(
 788                                 'You must update your load-balancing configuration. ' .
 789                                 'See DefaultSettings.php entry for $wgDBservers.' );
 790                 }
 791
 792                 if ( $dbNameOverride !== false ) {
 793                         $server['dbname'] = $dbNameOverride;
 794                 }
 795
 796                 // Let the handle know what the cluster master is (e.g. "db1052")
 797                 $masterName = $this->getServerName( $this->getWriterIndex() );
 798                 $server['clusterMasterHost'] = $masterName;
 799
 800                 // Log when many connection are made on requests
 801                 if ( ++$this->connsOpened >= self::CONN_HELD_WARN_THRESHOLD ) {
 802                         $this->perfLogger->warning( __METHOD__ . ": " .
 803                                 "{$this->connsOpened}+ connections made (master=$masterName)" );
 804                 }
 805
 806                 // Set loggers
 807                 $server['connLogger'] = $this->connLogger;
 808                 $server['queryLogger'] = $this->queryLogger;
 809                 $server['trxProfiler'] = $this->trxProfiler;
 810
 811                 // Create a live connection object
 812                 try {
 813                         $db = DatabaseBase::factory( $server['type'], $server );
 814                 } catch ( DBConnectionError $e ) {
 815                         // FIXME: This is probably the ugliest thing I have ever done to
 816                         // PHP. I'm half-expecting it to segfault, just out of disgust. -- TS
 817                         $db = $e->db;
 818                 }
 819
 820                 $db->setLBInfo( $server );
 821                 $db->setLazyMasterHandle(
 822                         $this->getLazyConnectionRef( DB_MASTER, [], $db->getWikiID() )
 823                 );
 824
 825                 if ( $server['serverIndex'] === $this->getWriterIndex() ) {
 826                         if ( $this->trxRoundId !== false ) {
 827                                 $this->applyTransactionRoundFlags( $db );
 828                         }
 829                         foreach ( $this->trxRecurringCallbacks as $name => $callback ) {
 830                                 $db->setTransactionListener( $name, $callback );
 831                         }
 832                 }
 833
 834                 return $db;
 835         }
 836
 837         /**
 838          * @throws DBConnectionError
 839          * @return bool
 840          */
 841         private function reportConnectionError() {
 842                 $conn = $this->mErrorConnection; // The connection which caused the error
 843                 $context = [
 844                         'method' => __METHOD__,
 845                         'last_error' => $this->mLastError,
 846                 ];
 847
 848                 if ( !is_object( $conn ) ) {
 849                         // No last connection, probably due to all servers being too busy
 850                         $this->connLogger->error(
 851                                 "LB failure with no last connection. Connection error: {last_error}",
 852                                 $context
 853                         );
 854
 855                         // If all servers were busy, mLastError will contain something sensible
 856                         throw new DBConnectionError( null, $this->mLastError );
 857                 } else {
 858                         $context['db_server'] = $conn->getProperty( 'mServer' );
 859                         $this->connLogger->warning(
 860                                 "Connection error: {last_error} ({db_server})",
 861                                 $context
 862                         );
 863
 864                         // throws DBConnectionError
 865                         $conn->reportConnectionError( "{$this->mLastError} ({$context['db_server']})" );
 866                 }
 867
 868                 return false; /* not reached */
 869         }
 870
 871         public function getWriterIndex() {
 872                 return 0;
 873         }
 874
 875         public function haveIndex( $i ) {
 876                 return array_key_exists( $i, $this->mServers );
 877         }
 878
 879         public function isNonZeroLoad( $i ) {
 880                 return array_key_exists( $i, $this->mServers ) && $this->mLoads[$i] != 0;
 881         }
 882
 883         public function getServerCount() {
 884                 return count( $this->mServers );
 885         }
 886
 887         public function getServerName( $i ) {
 888                 if ( isset( $this->mServers[$i]['hostName'] ) ) {
 889                         $name = $this->mServers[$i]['hostName'];
 890                 } elseif ( isset( $this->mServers[$i]['host'] ) ) {
 891                         $name = $this->mServers[$i]['host'];
 892                 } else {
 893                         $name = '';
 894                 }
 895
 896                 return ( $name != '' ) ? $name : 'localhost';
 897         }
 898
 899         public function getServerInfo( $i ) {
 900                 if ( isset( $this->mServers[$i] ) ) {
 901                         return $this->mServers[$i];
 902                 } else {
 903                         return false;
 904                 }
 905         }
 906
 907         public function setServerInfo( $i, array $serverInfo ) {
 908                 $this->mServers[$i] = $serverInfo;
 909         }
 910
 911         public function getMasterPos() {
 912                 # If this entire request was served from a replica DB without opening a connection to the
 913                 # master (however unlikely that may be), then we can fetch the position from the replica DB.
 914                 $masterConn = $this->getAnyOpenConnection( $this->getWriterIndex() );
 915                 if ( !$masterConn ) {
 916                         $serverCount = count( $this->mServers );
 917                         for ( $i = 1; $i < $serverCount; $i++ ) {
 918                                 $conn = $this->getAnyOpenConnection( $i );
 919                                 if ( $conn ) {
 920                                         return $conn->getSlavePos();
 921                                 }
 922                         }
 923                 } else {
 924                         return $masterConn->getMasterPos();
 925                 }
 926
 927                 return false;
 928         }
 929
 930         /**
 931          * Disable this load balancer. All connections are closed, and any attempt to
 932          * open a new connection will result in a DBAccessError.
 933          *
 934          * @since 1.27
 935          */
 936         public function disable() {
 937                 $this->closeAll();
 938                 $this->disabled = true;
 939         }
 940
 941         public function closeAll() {
 942                 $this->forEachOpenConnection( function ( IDatabase $conn ) {
 943                         $conn->close();
 944                 } );
 945
 946                 $this->mConns = [
 947                         'local' => [],
 948                         'foreignFree' => [],
 949                         'foreignUsed' => [],
 950                 ];
 951                 $this->connsOpened = 0;
 952         }
 953
 954         public function closeConnection( IDatabase $conn ) {
 955                 $serverIndex = $conn->getLBInfo( 'serverIndex' ); // second index level of mConns
 956                 foreach ( $this->mConns as $type => $connsByServer ) {
 957                         if ( !isset( $connsByServer[$serverIndex] ) ) {
 958                                 continue;
 959                         }
 960
 961                         foreach ( $connsByServer[$serverIndex] as $i => $trackedConn ) {
 962                                 if ( $conn === $trackedConn ) {
 963                                         unset( $this->mConns[$type][$serverIndex][$i] );
 964                                         --$this->connsOpened;
 965                                         break 2;
 966                                 }
 967                         }
 968                 }
 969
 970                 $conn->close();
 971         }
 972
 973         public function commitAll( $fname = __METHOD__ ) {
 974                 $failures = [];
 975
 976                 $restore = ( $this->trxRoundId !== false );
 977                 $this->trxRoundId = false;
 978                 $this->forEachOpenConnection(
 979                         function ( IDatabase $conn ) use ( $fname, $restore, &$failures ) {
 980                                 try {
 981                                         $conn->commit( $fname, $conn::FLUSHING_ALL_PEERS );
 982                                 } catch ( DBError $e ) {
 983                                         call_user_func( $this->errorLogger, $e );
 984                                         $failures[] = "{$conn->getServer()}: {$e->getMessage()}";
 985                                 }
 986                                 if ( $restore && $conn->getLBInfo( 'master' ) ) {
 987                                         $this->undoTransactionRoundFlags( $conn );
 988                                 }
 989                         }
 990                 );
 991
 992                 if ( $failures ) {
 993                         throw new DBExpectedError(
 994                                 null,
 995                                 "Commit failed on server(s) " . implode( "\n", array_unique( $failures ) )
 996                         );
 997                 }
 998         }
 999
1000         /**
1001          * Perform all pre-commit callbacks that remain part of the atomic transactions
1002          * and disable any post-commit callbacks until runMasterPostTrxCallbacks()
1003          * @since 1.28
1004          */
1005         public function finalizeMasterChanges() {
1006                 $this->forEachOpenMasterConnection( function ( DatabaseBase $conn ) {
1007                         // Any error should cause all DB transactions to be rolled back together
1008                         $conn->setTrxEndCallbackSuppression( false );
1009                         $conn->runOnTransactionPreCommitCallbacks();
1010                         // Defer post-commit callbacks until COMMIT finishes for all DBs
1011                         $conn->setTrxEndCallbackSuppression( true );
1012                 } );
1013         }
1014
1015         /**
1016          * Perform all pre-commit checks for things like replication safety
1017          * @param array $options Includes:
1018          *   - maxWriteDuration : max write query duration time in seconds
1019          * @throws DBTransactionError
1020          * @since 1.28
1021          */
1022         public function approveMasterChanges( array $options ) {
1023                 $limit = isset( $options['maxWriteDuration'] ) ? $options['maxWriteDuration'] : 0;
1024                 $this->forEachOpenMasterConnection( function ( IDatabase $conn ) use ( $limit ) {
1025                         // If atomic sections or explicit transactions are still open, some caller must have
1026                         // caught an exception but failed to properly rollback any changes. Detect that and
1027                         // throw and error (causing rollback).
1028                         if ( $conn->explicitTrxActive() ) {
1029                                 throw new DBTransactionError(
1030                                         $conn,
1031                                         "Explicit transaction still active. A caller may have caught an error."
1032                                 );
1033                         }
1034                         // Assert that the time to replicate the transaction will be sane.
1035                         // If this fails, then all DB transactions will be rollback back together.
1036                         $time = $conn->pendingWriteQueryDuration( $conn::ESTIMATE_DB_APPLY );
1037                         if ( $limit > 0 && $time > $limit ) {
1038                                 throw new DBTransactionSizeError(
1039                                         $conn,
1040                                         "Transaction spent $time second(s) in writes, exceeding the $limit limit.",
1041                                         [ $time, $limit ]
1042                                 );
1043                         }
1044                         // If a connection sits idle while slow queries execute on another, that connection
1045                         // may end up dropped before the commit round is reached. Ping servers to detect this.
1046                         if ( $conn->writesOrCallbacksPending() && !$conn->ping() ) {
1047                                 throw new DBTransactionError(
1048                                         $conn,
1049                                         "A connection to the {$conn->getDBname()} database was lost before commit."
1050                                 );
1051                         }
1052                 } );
1053         }
1054
1055         /**
1056          * Flush any master transaction snapshots and set DBO_TRX (if DBO_DEFAULT is set)
1057          *
1058          * The DBO_TRX setting will be reverted to the default in each of these methods:
1059          *   - commitMasterChanges()
1060          *   - rollbackMasterChanges()
1061          *   - commitAll()
1062          * This allows for custom transaction rounds from any outer transaction scope.
1063          *
1064          * @param string $fname
1065          * @throws DBExpectedError
1066          * @since 1.28
1067          */
1068         public function beginMasterChanges( $fname = __METHOD__ ) {
1069                 if ( $this->trxRoundId !== false ) {
1070                         throw new DBTransactionError(
1071                                 null,
1072                                 "$fname: Transaction round '{$this->trxRoundId}' already started."
1073                         );
1074                 }
1075                 $this->trxRoundId = $fname;
1076
1077                 $failures = [];
1078                 $this->forEachOpenMasterConnection(
1079                         function ( DatabaseBase $conn ) use ( $fname, &$failures ) {
1080                                 $conn->setTrxEndCallbackSuppression( true );
1081                                 try {
1082                                         $conn->flushSnapshot( $fname );
1083                                 } catch ( DBError $e ) {
1084                                         call_user_func( $this->errorLogger, $e );
1085                                         $failures[] = "{$conn->getServer()}: {$e->getMessage()}";
1086                                 }
1087                                 $conn->setTrxEndCallbackSuppression( false );
1088                                 $this->applyTransactionRoundFlags( $conn );
1089                         }
1090                 );
1091
1092                 if ( $failures ) {
1093                         throw new DBExpectedError(
1094                                 null,
1095                                 "$fname: Flush failed on server(s) " . implode( "\n", array_unique( $failures ) )
1096                         );
1097                 }
1098         }
1099
1100         public function commitMasterChanges( $fname = __METHOD__ ) {
1101                 $failures = [];
1102
1103                 $restore = ( $this->trxRoundId !== false );
1104                 $this->trxRoundId = false;
1105                 $this->forEachOpenMasterConnection(
1106                         function ( IDatabase $conn ) use ( $fname, $restore, &$failures ) {
1107                                 try {
1108                                         if ( $conn->writesOrCallbacksPending() ) {
1109                                                 $conn->commit( $fname, $conn::FLUSHING_ALL_PEERS );
1110                                         } elseif ( $restore ) {
1111                                                 $conn->flushSnapshot( $fname );
1112                                         }
1113                                 } catch ( DBError $e ) {
1114                                         call_user_func( $this->errorLogger, $e );
1115                                         $failures[] = "{$conn->getServer()}: {$e->getMessage()}";
1116                                 }
1117                                 if ( $restore ) {
1118                                         $this->undoTransactionRoundFlags( $conn );
1119                                 }
1120                         }
1121                 );
1122
1123                 if ( $failures ) {
1124                         throw new DBExpectedError(
1125                                 null,
1126                                 "$fname: Commit failed on server(s) " . implode( "\n", array_unique( $failures ) )
1127                         );
1128                 }
1129         }
1130
1131         /**
1132          * Issue all pending post-COMMIT/ROLLBACK callbacks
1133          * @param integer $type IDatabase::TRIGGER_* constant
1134          * @return Exception|null The first exception or null if there were none
1135          * @since 1.28
1136          */
1137         public function runMasterPostTrxCallbacks( $type ) {
1138                 $e = null; // first exception
1139                 $this->forEachOpenMasterConnection( function ( DatabaseBase $conn ) use ( $type, &$e ) {
1140                         $conn->setTrxEndCallbackSuppression( false );
1141                         if ( $conn->writesOrCallbacksPending() ) {
1142                                 // This happens if onTransactionIdle() callbacks leave callbacks on *another* DB
1143                                 // (which finished its callbacks already). Warn and recover in this case. Let the
1144                                 // callbacks run in the final commitMasterChanges() in LBFactory::shutdown().
1145                                 $this->queryLogger->error( __METHOD__ . ": found writes/callbacks pending." );
1146                                 return;
1147                         } elseif ( $conn->trxLevel() ) {
1148                                 // This happens for single-DB setups where DB_REPLICA uses the master DB,
1149                                 // thus leaving an implicit read-only transaction open at this point. It
1150                                 // also happens if onTransactionIdle() callbacks leave implicit transactions
1151                                 // open on *other* DBs (which is slightly improper). Let these COMMIT on the
1152                                 // next call to commitMasterChanges(), possibly in LBFactory::shutdown().
1153                                 return;
1154                         }
1155                         try {
1156                                 $conn->runOnTransactionIdleCallbacks( $type );
1157                         } catch ( Exception $ex ) {
1158                                 $e = $e ?: $ex;
1159                         }
1160                         try {
1161                                 $conn->runTransactionListenerCallbacks( $type );
1162                         } catch ( Exception $ex ) {
1163                                 $e = $e ?: $ex;
1164                         }
1165                 } );
1166
1167                 return $e;
1168         }
1169
1170         /**
1171          * Issue ROLLBACK only on master, only if queries were done on connection
1172          * @param string $fname Caller name
1173          * @throws DBExpectedError
1174          * @since 1.23
1175          */
1176         public function rollbackMasterChanges( $fname = __METHOD__ ) {
1177                 $restore = ( $this->trxRoundId !== false );
1178                 $this->trxRoundId = false;
1179                 $this->forEachOpenMasterConnection(
1180                         function ( IDatabase $conn ) use ( $fname, $restore ) {
1181                                 if ( $conn->writesOrCallbacksPending() ) {
1182                                         $conn->rollback( $fname, $conn::FLUSHING_ALL_PEERS );
1183                                 }
1184                                 if ( $restore ) {
1185                                         $this->undoTransactionRoundFlags( $conn );
1186                                 }
1187                         }
1188                 );
1189         }
1190
1191         /**
1192          * Suppress all pending post-COMMIT/ROLLBACK callbacks
1193          * @return Exception|null The first exception or null if there were none
1194          * @since 1.28
1195          */
1196         public function suppressTransactionEndCallbacks() {
1197                 $this->forEachOpenMasterConnection( function ( DatabaseBase $conn ) {
1198                         $conn->setTrxEndCallbackSuppression( true );
1199                 } );
1200         }
1201
1202         /**
1203          * @param IDatabase $conn
1204          */
1205         private function applyTransactionRoundFlags( IDatabase $conn ) {
1206                 if ( $conn->getFlag( DBO_DEFAULT ) ) {
1207                         // DBO_TRX is controlled entirely by CLI mode presence with DBO_DEFAULT.
1208                         // Force DBO_TRX even in CLI mode since a commit round is expected soon.
1209                         $conn->setFlag( DBO_TRX, $conn::REMEMBER_PRIOR );
1210                         // If config has explicitly requested DBO_TRX be either on or off by not
1211                         // setting DBO_DEFAULT, then respect that. Forcing no transactions is useful
1212                         // for things like blob stores (ExternalStore) which want auto-commit mode.
1213                 }
1214         }
1215
1216         /**
1217          * @param IDatabase $conn
1218          */
1219         private function undoTransactionRoundFlags( IDatabase $conn ) {
1220                 if ( $conn->getFlag( DBO_DEFAULT ) ) {
1221                         $conn->restoreFlags( $conn::RESTORE_PRIOR );
1222                 }
1223         }
1224
1225         /**
1226          * Commit all replica DB transactions so as to flush any REPEATABLE-READ or SSI snapshot
1227          *
1228          * @param string $fname Caller name
1229          * @since 1.28
1230          */
1231         public function flushReplicaSnapshots( $fname = __METHOD__ ) {
1232                 $this->forEachOpenReplicaConnection( function ( IDatabase $conn ) {
1233                         $conn->flushSnapshot( __METHOD__ );
1234                 } );
1235         }
1236
1237         /**
1238          * @return bool Whether a master connection is already open
1239          * @since 1.24
1240          */
1241         public function hasMasterConnection() {
1242                 return $this->isOpen( $this->getWriterIndex() );
1243         }
1244
1245         /**
1246          * Determine if there are pending changes in a transaction by this thread
1247          * @since 1.23
1248          * @return bool
1249          */
1250         public function hasMasterChanges() {
1251                 $pending = 0;
1252                 $this->forEachOpenMasterConnection( function ( IDatabase $conn ) use ( &$pending ) {
1253                         $pending |= $conn->writesOrCallbacksPending();
1254                 } );
1255
1256                 return (bool)$pending;
1257         }
1258
1259         /**
1260          * Get the timestamp of the latest write query done by this thread
1261          * @since 1.25
1262          * @return float|bool UNIX timestamp or false
1263          */
1264         public function lastMasterChangeTimestamp() {
1265                 $lastTime = false;
1266                 $this->forEachOpenMasterConnection( function ( IDatabase $conn ) use ( &$lastTime ) {
1267                         $lastTime = max( $lastTime, $conn->lastDoneWrites() );
1268                 } );
1269
1270                 return $lastTime;
1271         }
1272
1273         /**
1274          * Check if this load balancer object had any recent or still
1275          * pending writes issued against it by this PHP thread
1276          *
1277          * @param float $age How many seconds ago is "recent" [defaults to mWaitTimeout]
1278          * @return bool
1279          * @since 1.25
1280          */
1281         public function hasOrMadeRecentMasterChanges( $age = null ) {
1282                 $age = ( $age === null ) ? $this->mWaitTimeout : $age;
1283
1284                 return ( $this->hasMasterChanges()
1285                         || $this->lastMasterChangeTimestamp() > microtime( true ) - $age );
1286         }
1287
1288         /**
1289          * Get the list of callers that have pending master changes
1290          *
1291          * @return string[] List of method names
1292          * @since 1.27
1293          */
1294         public function pendingMasterChangeCallers() {
1295                 $fnames = [];
1296                 $this->forEachOpenMasterConnection( function ( IDatabase $conn ) use ( &$fnames ) {
1297                         $fnames = array_merge( $fnames, $conn->pendingWriteCallers() );
1298                 } );
1299
1300                 return $fnames;
1301         }
1302
1303         public function getLaggedReplicaMode( $domain = false ) {
1304                 // No-op if there is only one DB (also avoids recursion)
1305                 if ( !$this->laggedReplicaMode && $this->getServerCount() > 1 ) {
1306                         try {
1307                                 // See if laggedReplicaMode gets set
1308                                 $conn = $this->getConnection( DB_REPLICA, false, $domain );
1309                                 $this->reuseConnection( $conn );
1310                         } catch ( DBConnectionError $e ) {
1311                                 // Avoid expensive re-connect attempts and failures
1312                                 $this->allReplicasDownMode = true;
1313                                 $this->laggedReplicaMode = true;
1314                         }
1315                 }
1316
1317                 return $this->laggedReplicaMode;
1318         }
1319
1320         /**
1321          * @param bool $domain
1322          * @return bool
1323          * @deprecated 1.28; use getLaggedReplicaMode()
1324          */
1325         public function getLaggedSlaveMode( $domain = false ) {
1326                 return $this->getLaggedReplicaMode( $domain );
1327         }
1328
1329         /**
1330          * @note This method will never cause a new DB connection
1331          * @return bool Whether any generic connection used for reads was highly "lagged"
1332          * @since 1.28
1333          */
1334         public function laggedReplicaUsed() {
1335                 return $this->laggedReplicaMode;
1336         }
1337
1338         /**
1339          * @return bool
1340          * @since 1.27
1341          * @deprecated Since 1.28; use laggedReplicaUsed()
1342          */
1343         public function laggedSlaveUsed() {
1344                 return $this->laggedReplicaUsed();
1345         }
1346
1347         /**
1348          * @note This method may trigger a DB connection if not yet done
1349          * @param string|bool $domain Domain ID, or false for the current domain
1350          * @param IDatabase|null DB master connection; used to avoid loops [optional]
1351          * @return string|bool Reason the master is read-only or false if it is not
1352          * @since 1.27
1353          */
1354         public function getReadOnlyReason( $domain = false, IDatabase $conn = null ) {
1355                 if ( $this->readOnlyReason !== false ) {
1356                         return $this->readOnlyReason;
1357                 } elseif ( $this->getLaggedReplicaMode( $domain ) ) {
1358                         if ( $this->allReplicasDownMode ) {
1359                                 return 'The database has been automatically locked ' .
1360                                         'until the replica database servers become available';
1361                         } else {
1362                                 return 'The database has been automatically locked ' .
1363                                         'while the replica database servers catch up to the master.';
1364                         }
1365                 } elseif ( $this->masterRunningReadOnly( $domain, $conn ) ) {
1366                         return 'The database master is running in read-only mode.';
1367                 }
1368
1369                 return false;
1370         }
1371
1372         /**
1373          * @param string $domain Domain ID, or false for the current domain
1374          * @param IDatabase|null DB master connectionl used to avoid loops [optional]
1375          * @return bool
1376          */
1377         private function masterRunningReadOnly( $domain, IDatabase $conn = null ) {
1378                 $cache = $this->wanCache;
1379                 $masterServer = $this->getServerName( $this->getWriterIndex() );
1380
1381                 return (bool)$cache->getWithSetCallback(
1382                         $cache->makeGlobalKey( __CLASS__, 'server-read-only', $masterServer ),
1383                         self::TTL_CACHE_READONLY,
1384                         function () use ( $domain, $conn ) {
1385                                 $this->trxProfiler->setSilenced( true );
1386                                 try {
1387                                         $dbw = $conn ?: $this->getConnection( DB_MASTER, [], $domain );
1388                                         $readOnly = (int)$dbw->serverIsReadOnly();
1389                                 } catch ( DBError $e ) {
1390                                         $readOnly = 0;
1391                                 }
1392                                 $this->trxProfiler->setSilenced( false );
1393                                 return $readOnly;
1394                         },
1395                         [ 'pcTTL' => $cache::TTL_PROC_LONG, 'busyValue' => 0 ]
1396                 );
1397         }
1398
1399         public function allowLagged( $mode = null ) {
1400                 if ( $mode === null ) {
1401                         return $this->mAllowLagged;
1402                 }
1403                 $this->mAllowLagged = $mode;
1404
1405                 return $this->mAllowLagged;
1406         }
1407
1408         public function pingAll() {
1409                 $success = true;
1410                 $this->forEachOpenConnection( function ( IDatabase $conn ) use ( &$success ) {
1411                         if ( !$conn->ping() ) {
1412                                 $success = false;
1413                         }
1414                 } );
1415
1416                 return $success;
1417         }
1418
1419         public function forEachOpenConnection( $callback, array $params = [] ) {
1420                 foreach ( $this->mConns as $connsByServer ) {
1421                         foreach ( $connsByServer as $serverConns ) {
1422                                 foreach ( $serverConns as $conn ) {
1423                                         $mergedParams = array_merge( [ $conn ], $params );
1424                                         call_user_func_array( $callback, $mergedParams );
1425                                 }
1426                         }
1427                 }
1428         }
1429
1430         /**
1431          * Call a function with each open connection object to a master
1432          * @param callable $callback
1433          * @param array $params
1434          * @since 1.28
1435          */
1436         public function forEachOpenMasterConnection( $callback, array $params = [] ) {
1437                 $masterIndex = $this->getWriterIndex();
1438                 foreach ( $this->mConns as $connsByServer ) {
1439                         if ( isset( $connsByServer[$masterIndex] ) ) {
1440                                 /** @var IDatabase $conn */
1441                                 foreach ( $connsByServer[$masterIndex] as $conn ) {
1442                                         $mergedParams = array_merge( [ $conn ], $params );
1443                                         call_user_func_array( $callback, $mergedParams );
1444                                 }
1445                         }
1446                 }
1447         }
1448
1449         /**
1450          * Call a function with each open replica DB connection object
1451          * @param callable $callback
1452          * @param array $params
1453          * @since 1.28
1454          */
1455         public function forEachOpenReplicaConnection( $callback, array $params = [] ) {
1456                 foreach ( $this->mConns as $connsByServer ) {
1457                         foreach ( $connsByServer as $i => $serverConns ) {
1458                                 if ( $i === $this->getWriterIndex() ) {
1459                                         continue; // skip master
1460                                 }
1461                                 foreach ( $serverConns as $conn ) {
1462                                         $mergedParams = array_merge( [ $conn ], $params );
1463                                         call_user_func_array( $callback, $mergedParams );
1464                                 }
1465                         }
1466                 }
1467         }
1468
1469         public function getMaxLag( $domain = false ) {
1470                 $maxLag = -1;
1471                 $host = '';
1472                 $maxIndex = 0;
1473
1474                 if ( $this->getServerCount() <= 1 ) {
1475                         return [ $host, $maxLag, $maxIndex ]; // no replication = no lag
1476                 }
1477
1478                 $lagTimes = $this->getLagTimes( $domain );
1479                 foreach ( $lagTimes as $i => $lag ) {
1480                         if ( $this->mLoads[$i] > 0 && $lag > $maxLag ) {
1481                                 $maxLag = $lag;
1482                                 $host = $this->mServers[$i]['host'];
1483                                 $maxIndex = $i;
1484                         }
1485                 }
1486
1487                 return [ $host, $maxLag, $maxIndex ];
1488         }
1489
1490         public function getLagTimes( $domain = false ) {
1491                 if ( $this->getServerCount() <= 1 ) {
1492                         return [ 0 => 0 ]; // no replication = no lag
1493                 }
1494
1495                 # Send the request to the load monitor
1496                 return $this->getLoadMonitor()->getLagTimes( array_keys( $this->mServers ), $domain );
1497         }
1498
1499         public function safeGetLag( IDatabase $conn ) {
1500                 if ( $this->getServerCount() == 1 ) {
1501                         return 0;
1502                 } else {
1503                         return $conn->getLag();
1504                 }
1505         }
1506
1507         /**
1508          * Wait for a replica DB to reach a specified master position
1509          *
1510          * This will connect to the master to get an accurate position if $pos is not given
1511          *
1512          * @param IDatabase $conn Replica DB
1513          * @param DBMasterPos|bool $pos Master position; default: current position
1514          * @param integer $timeout Timeout in seconds
1515          * @return bool Success
1516          * @since 1.27
1517          */
1518         public function safeWaitForMasterPos( IDatabase $conn, $pos = false, $timeout = 10 ) {
1519                 if ( $this->getServerCount() == 1 || !$conn->getLBInfo( 'replica' ) ) {
1520                         return true; // server is not a replica DB
1521                 }
1522
1523                 $pos = $pos ?: $this->getConnection( DB_MASTER )->getMasterPos();
1524                 if ( !( $pos instanceof DBMasterPos ) ) {
1525                         return false; // something is misconfigured
1526                 }
1527
1528                 $result = $conn->masterPosWait( $pos, $timeout );
1529                 if ( $result == -1 || is_null( $result ) ) {
1530                         $msg = __METHOD__ . ": Timed out waiting on {$conn->getServer()} pos {$pos}";
1531                         $this->replLogger->warning( "$msg" );
1532                         $ok = false;
1533                 } else {
1534                         $this->replLogger->info( __METHOD__ . ": Done" );
1535                         $ok = true;
1536                 }
1537
1538                 return $ok;
1539         }
1540
1541         /**
1542          * Clear the cache for slag lag delay times
1543          *
1544          * This is only used for testing
1545          * @since 1.26
1546          */
1547         public function clearLagTimeCache() {
1548                 $this->getLoadMonitor()->clearCaches();
1549         }
1550
1551         /**
1552          * Set a callback via IDatabase::setTransactionListener() on
1553          * all current and future master connections of this load balancer
1554          *
1555          * @param string $name Callback name
1556          * @param callable|null $callback
1557          * @since 1.28
1558          */
1559         public function setTransactionListener( $name, callable $callback = null ) {
1560                 if ( $callback ) {
1561                         $this->trxRecurringCallbacks[$name] = $callback;
1562                 } else {
1563                         unset( $this->trxRecurringCallbacks[$name] );
1564                 }
1565                 $this->forEachOpenMasterConnection(
1566                         function ( IDatabase $conn ) use ( $name, $callback ) {
1567                                 $conn->setTransactionListener( $name, $callback );
1568                         }
1569                 );
1570         }
1571
1572         /**
1573          * Set a new table prefix for the existing local domain ID for testing
1574          *
1575          * @param string $prefix
1576          * @since 1.28
1577          */
1578         public function setDomainPrefix( $prefix ) {
1579                 list( $dbName, ) = explode( '-', $this->localDomain, 2 );
1580
1581                 $this->localDomain = "{$dbName}-{$prefix}";
1582         }
1583 }