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  */
  22 namespace Wikimedia\Rdbms;
  23
  24 use Psr\Log\LoggerInterface;
  25 use Psr\Log\NullLogger;
  26 use Wikimedia\ScopedCallback;
  27 use BagOStuff;
  28 use EmptyBagOStuff;
  29 use WANObjectCache;
  30 use ArrayUtils;
  31 use InvalidArgumentException;
  32 use RuntimeException;
  33 use Exception;
  34
  35 /**
  36  * Database connection, tracking, load balancing, and transaction manager for a cluster
  37  *
  38  * @ingroup Database
  39  */
  40 class LoadBalancer implements ILoadBalancer {
  41         /** @var array[] Map of (server index => server config array) */
  42         private $servers;
  43         /** @var Database[][][] Map of (connection category => server index => IDatabase[]) */
  44         private $conns;
  45         /** @var float[] Map of (server index => weight) */
  46         private $loads;
  47         /** @var array[] Map of (group => server index => weight) */
  48         private $groupLoads;
  49         /** @var bool Whether to disregard replica DB lag as a factor in replica DB selection */
  50         private $allowLagged;
  51         /** @var int Seconds to spend waiting on replica DB lag to resolve */
  52         private $waitTimeout;
  53         /** @var array The LoadMonitor configuration */
  54         private $loadMonitorConfig;
  55         /** @var array[] $aliases Map of (table => (dbname, schema, prefix) map) */
  56         private $tableAliases = [];
  57         /** @var string[] Map of (index alias => index) */
  58         private $indexAliases = [];
  59
  60         /** @var ILoadMonitor */
  61         private $loadMonitor;
  62         /** @var callable|null Callback to run before the first connection attempt */
  63         private $chronologyCallback;
  64         /** @var BagOStuff */
  65         private $srvCache;
  66         /** @var WANObjectCache */
  67         private $wanCache;
  68         /** @var object|string Class name or object With profileIn/profileOut methods */
  69         protected $profiler;
  70         /** @var TransactionProfiler */
  71         protected $trxProfiler;
  72         /** @var LoggerInterface */
  73         protected $replLogger;
  74         /** @var LoggerInterface */
  75         protected $connLogger;
  76         /** @var LoggerInterface */
  77         protected $queryLogger;
  78         /** @var LoggerInterface */
  79         protected $perfLogger;
  80
  81         /** @var Database DB connection object that caused a problem */
  82         private $errorConnection;
  83         /** @var int The generic (not query grouped) replica DB index (of $mServers) */
  84         private $readIndex;
  85         /** @var bool|DBMasterPos False if not set */
  86         private $waitForPos;
  87         /** @var bool Whether the generic reader fell back to a lagged replica DB */
  88         private $laggedReplicaMode = false;
  89         /** @var bool Whether the generic reader fell back to a lagged replica DB */
  90         private $allReplicasDownMode = false;
  91         /** @var string The last DB selection or connection error */
  92         private $lastError = 'Unknown error';
  93         /** @var string|bool Reason the LB is read-only or false if not */
  94         private $readOnlyReason = false;
  95         /** @var int Total connections opened */
  96         private $connsOpened = 0;
  97         /** @var string|bool String if a requested DBO_TRX transaction round is active */
  98         private $trxRoundId = false;
  99         /** @var array[] Map of (name => callable) */
 100         private $trxRecurringCallbacks = [];
 101         /** @var DatabaseDomain Local Domain ID and default for selectDB() calls */
 102         private $localDomain;
 103         /** @var string Alternate ID string for the domain instead of DatabaseDomain::getId() */
 104         private $localDomainIdAlias;
 105         /** @var string Current server name */
 106         private $host;
 107         /** @var bool Whether this PHP instance is for a CLI script */
 108         protected $cliMode;
 109         /** @var string Agent name for query profiling */
 110         protected $agent;
 111
 112         /** @var callable Exception logger */
 113         private $errorLogger;
 114         /** @var callable Deprecation logger */
 115         private $deprecationLogger;
 116
 117         /** @var bool */
 118         private $disabled = false;
 119         /** @var bool Whether any connection has been attempted yet */
 120         private $connectionAttempted = false;
 121         /** @var int */
 122         private $maxLag = self::MAX_LAG_DEFAULT;
 123         /** @var string Stage of the current transaction round in the transaction round life-cycle */
 124         private $trxRoundStage = self::ROUND_CURSORY;
 125
 126         /** @var int Warn when this many connection are held */
 127         const CONN_HELD_WARN_THRESHOLD = 10;
 128
 129         /** @var int Default 'maxLag' when unspecified */
 130         const MAX_LAG_DEFAULT = 10;
 131         /** @var int Default 'waitTimeout' when unspecified */
 132         const MAX_WAIT_DEFAULT = 10;
 133         /** @var int Seconds to cache master server read-only status */
 134         const TTL_CACHE_READONLY = 5;
 135
 136         const KEY_LOCAL = 'local';
 137         const KEY_FOREIGN_FREE = 'foreignFree';
 138         const KEY_FOREIGN_INUSE = 'foreignInUse';
 139
 140         const KEY_LOCAL_NOROUND = 'localAutoCommit';
 141         const KEY_FOREIGN_FREE_NOROUND = 'foreignFreeAutoCommit';
 142         const KEY_FOREIGN_INUSE_NOROUND = 'foreignInUseAutoCommit';
 143
 144         /** @var string Transaction round, explicit or implicit, has not finished writing */
 145         const ROUND_CURSORY = 'cursory';
 146         /** @var string Transaction round writes are complete and ready for pre-commit checks */
 147         const ROUND_FINALIZED = 'finalized';
 148         /** @var string Transaction round passed final pre-commit checks */
 149         const ROUND_APPROVED = 'approved';
 150         /** @var string Transaction round was committed and post-commit callbacks must be run */
 151         const ROUND_COMMIT_CALLBACKS = 'commit-callbacks';
 152         /** @var string Transaction round was rolled back and post-rollback callbacks must be run */
 153         const ROUND_ROLLBACK_CALLBACKS = 'rollback-callbacks';
 154         /** @var string Transaction round encountered an error */
 155         const ROUND_ERROR = 'error';
 156
 157         public function __construct( array $params ) {
 158                 if ( !isset( $params['servers'] ) ) {
 159                         throw new InvalidArgumentException( __CLASS__ . ': missing servers parameter' );
 160                 }
 161                 $this->servers = $params['servers'];
 162                 foreach ( $this->servers as $i => $server ) {
 163                         if ( $i == 0 ) {
 164                                 $this->servers[$i]['master'] = true;
 165                         } else {
 166                                 $this->servers[$i]['replica'] = true;
 167                         }
 168                 }
 169
 170                 $localDomain = isset( $params['localDomain'] )
 171                         ? DatabaseDomain::newFromId( $params['localDomain'] )
 172                         : DatabaseDomain::newUnspecified();
 173                 $this->setLocalDomain( $localDomain );
 174
 175                 $this->waitTimeout = isset( $params['waitTimeout'] )
 176                         ? $params['waitTimeout']
 177                         : self::MAX_WAIT_DEFAULT;
 178
 179                 $this->readIndex = -1;
 180                 $this->conns = [
 181                         // Connection were transaction rounds may be applied
 182                         self::KEY_LOCAL => [],
 183                         self::KEY_FOREIGN_INUSE => [],
 184                         self::KEY_FOREIGN_FREE => [],
 185                         // Auto-committing counterpart connections that ignore transaction rounds
 186                         self::KEY_LOCAL_NOROUND => [],
 187                         self::KEY_FOREIGN_INUSE_NOROUND => [],
 188                         self::KEY_FOREIGN_FREE_NOROUND => []
 189                 ];
 190                 $this->loads = [];
 191                 $this->waitForPos = false;
 192                 $this->allowLagged = false;
 193
 194                 if ( isset( $params['readOnlyReason'] ) && is_string( $params['readOnlyReason'] ) ) {
 195                         $this->readOnlyReason = $params['readOnlyReason'];
 196                 }
 197
 198                 if ( isset( $params['maxLag'] ) ) {
 199                         $this->maxLag = $params['maxLag'];
 200                 }
 201
 202                 if ( isset( $params['loadMonitor'] ) ) {
 203                         $this->loadMonitorConfig = $params['loadMonitor'];
 204                 } else {
 205                         $this->loadMonitorConfig = [ 'class' => 'LoadMonitorNull' ];
 206                 }
 207                 $this->loadMonitorConfig += [ 'lagWarnThreshold' => $this->maxLag ];
 208
 209                 foreach ( $params['servers'] as $i => $server ) {
 210                         $this->loads[$i] = $server['load'];
 211                         if ( isset( $server['groupLoads'] ) ) {
 212                                 foreach ( $server['groupLoads'] as $group => $ratio ) {
 213                                         if ( !isset( $this->groupLoads[$group] ) ) {
 214                                                 $this->groupLoads[$group] = [];
 215                                         }
 216                                         $this->groupLoads[$group][$i] = $ratio;
 217                                 }
 218                         }
 219                 }
 220
 221                 if ( isset( $params['srvCache'] ) ) {
 222                         $this->srvCache = $params['srvCache'];
 223                 } else {
 224                         $this->srvCache = new EmptyBagOStuff();
 225                 }
 226                 if ( isset( $params['wanCache'] ) ) {
 227                         $this->wanCache = $params['wanCache'];
 228                 } else {
 229                         $this->wanCache = WANObjectCache::newEmpty();
 230                 }
 231                 $this->profiler = isset( $params['profiler'] ) ? $params['profiler'] : null;
 232                 if ( isset( $params['trxProfiler'] ) ) {
 233                         $this->trxProfiler = $params['trxProfiler'];
 234                 } else {
 235                         $this->trxProfiler = new TransactionProfiler();
 236                 }
 237
 238                 $this->errorLogger = isset( $params['errorLogger'] )
 239                         ? $params['errorLogger']
 240                         : function ( Exception $e ) {
 241                                 trigger_error( get_class( $e ) . ': ' . $e->getMessage(), E_USER_WARNING );
 242                         };
 243                 $this->deprecationLogger = isset( $params['deprecationLogger'] )
 244                         ? $params['deprecationLogger']
 245                         : function ( $msg ) {
 246                                 trigger_error( $msg, E_USER_DEPRECATED );
 247                         };
 248
 249                 foreach ( [ 'replLogger', 'connLogger', 'queryLogger', 'perfLogger' ] as $key ) {
 250                         $this->$key = isset( $params[$key] ) ? $params[$key] : new NullLogger();
 251                 }
 252
 253                 $this->host = isset( $params['hostname'] )
 254                         ? $params['hostname']
 255                         : ( gethostname() ?: 'unknown' );
 256                 $this->cliMode = isset( $params['cliMode'] )
 257                         ? $params['cliMode']
 258                         : ( PHP_SAPI === 'cli' || PHP_SAPI === 'phpdbg' );
 259                 $this->agent = isset( $params['agent'] ) ? $params['agent'] : '';
 260
 261                 if ( isset( $params['chronologyCallback'] ) ) {
 262                         $this->chronologyCallback = $params['chronologyCallback'];
 263                 }
 264
 265                 if ( isset( $params['roundStage'] ) ) {
 266                         if ( $params['roundStage'] === self::STAGE_POSTCOMMIT_CALLBACKS ) {
 267                                 $this->trxRoundStage = self::ROUND_COMMIT_CALLBACKS;
 268                         } elseif ( $params['roundStage'] === self::STAGE_POSTROLLBACK_CALLBACKS ) {
 269                                 $this->trxRoundStage = self::ROUND_ROLLBACK_CALLBACKS;
 270                         }
 271                 }
 272         }
 273
 274         /**
 275          * Get the local (and default) database domain ID of connection handles
 276          *
 277          * @see DatabaseDomain
 278          * @return string Database domain ID; this specifies DB name, schema, and table prefix
 279          * @since 1.31
 280          */
 281         public function getLocalDomainID() {
 282                 return $this->localDomain->getId();
 283         }
 284
 285         /**
 286          * Get a LoadMonitor instance
 287          *
 288          * @return ILoadMonitor
 289          */
 290         private function getLoadMonitor() {
 291                 if ( !isset( $this->loadMonitor ) ) {
 292                         $compat = [
 293                                 'LoadMonitor' => LoadMonitor::class,
 294                                 'LoadMonitorNull' => LoadMonitorNull::class,
 295                                 'LoadMonitorMySQL' => LoadMonitorMySQL::class,
 296                         ];
 297
 298                         $class = $this->loadMonitorConfig['class'];
 299                         if ( isset( $compat[$class] ) ) {
 300                                 $class = $compat[$class];
 301                         }
 302
 303                         $this->loadMonitor = new $class(
 304                                 $this, $this->srvCache, $this->wanCache, $this->loadMonitorConfig );
 305                         $this->loadMonitor->setLogger( $this->replLogger );
 306                 }
 307
 308                 return $this->loadMonitor;
 309         }
 310
 311         /**
 312          * @param array $loads
 313          * @param bool|string $domain Domain to get non-lagged for
 314          * @param int $maxLag Restrict the maximum allowed lag to this many seconds
 315          * @return bool|int|string
 316          */
 317         private function getRandomNonLagged( array $loads, $domain = false, $maxLag = INF ) {
 318                 $lags = $this->getLagTimes( $domain );
 319
 320                 # Unset excessively lagged servers
 321                 foreach ( $lags as $i => $lag ) {
 322                         if ( $i != 0 ) {
 323                                 # How much lag this server nominally is allowed to have
 324                                 $maxServerLag = isset( $this->servers[$i]['max lag'] )
 325                                         ? $this->servers[$i]['max lag']
 326                                         : $this->maxLag; // default
 327                                 # Constrain that futher by $maxLag argument
 328                                 $maxServerLag = min( $maxServerLag, $maxLag );
 329
 330                                 $host = $this->getServerName( $i );
 331                                 if ( $lag === false && !is_infinite( $maxServerLag ) ) {
 332                                         $this->replLogger->error(
 333                                                 __METHOD__ .
 334                                                 ": server {host} is not replicating?", [ 'host' => $host ] );
 335                                         unset( $loads[$i] );
 336                                 } elseif ( $lag > $maxServerLag ) {
 337                                         $this->replLogger->info(
 338                                                 __METHOD__ .
 339                                                 ": server {host} has {lag} seconds of lag (>= {maxlag})",
 340                                                 [ 'host' => $host, 'lag' => $lag, 'maxlag' => $maxServerLag ]
 341                                         );
 342                                         unset( $loads[$i] );
 343                                 }
 344                         }
 345                 }
 346
 347                 # Find out if all the replica DBs with non-zero load are lagged
 348                 $sum = 0;
 349                 foreach ( $loads as $load ) {
 350                         $sum += $load;
 351                 }
 352                 if ( $sum == 0 ) {
 353                         # No appropriate DB servers except maybe the master and some replica DBs with zero load
 354                         # Do NOT use the master
 355                         # Instead, this function will return false, triggering read-only mode,
 356                         # and a lagged replica DB will be used instead.
 357                         return false;
 358                 }
 359
 360                 if ( count( $loads ) == 0 ) {
 361                         return false;
 362                 }
 363
 364                 # Return a random representative of the remainder
 365                 return ArrayUtils::pickRandom( $loads );
 366         }
 367
 368         public function getReaderIndex( $group = false, $domain = false ) {
 369                 if ( count( $this->servers ) == 1 ) {
 370                         // Skip the load balancing if there's only one server
 371                         return $this->getWriterIndex();
 372                 } elseif ( $group === false && $this->readIndex >= 0 ) {
 373                         // Shortcut if the generic reader index was already cached
 374                         return $this->readIndex;
 375                 }
 376
 377                 if ( $group !== false ) {
 378                         // Use the server weight array for this load group
 379                         if ( isset( $this->groupLoads[$group] ) ) {
 380                                 $loads = $this->groupLoads[$group];
 381                         } else {
 382                                 // No loads for this group, return false and the caller can use some other group
 383                                 $this->connLogger->info( __METHOD__ . ": no loads for group $group" );
 384
 385                                 return false;
 386                         }
 387                 } else {
 388                         // Use the generic load group
 389                         $loads = $this->loads;
 390                 }
 391
 392                 // Scale the configured load ratios according to each server's load and state
 393                 $this->getLoadMonitor()->scaleLoads( $loads, $domain );
 394
 395                 // Pick a server to use, accounting for weights, load, lag, and "waitForPos"
 396                 list( $i, $laggedReplicaMode ) = $this->pickReaderIndex( $loads, $domain );
 397                 if ( $i === false ) {
 398                         // Replica DB connection unsuccessful
 399                         return false;
 400                 }
 401
 402                 if ( $this->waitForPos && $i != $this->getWriterIndex() ) {
 403                         // Before any data queries are run, wait for the server to catch up to the
 404                         // specified position. This is used to improve session consistency. Note that
 405                         // when LoadBalancer::waitFor() sets "waitForPos", the waiting triggers here,
 406                         // so update laggedReplicaMode as needed for consistency.
 407                         if ( !$this->doWait( $i ) ) {
 408                                 $laggedReplicaMode = true;
 409                         }
 410                 }
 411
 412                 if ( $this->readIndex <= 0 && $this->loads[$i] > 0 && $group === false ) {
 413                         // Cache the generic reader index for future ungrouped DB_REPLICA handles
 414                         $this->readIndex = $i;
 415                         // Record if the generic reader index is in "lagged replica DB" mode
 416                         if ( $laggedReplicaMode ) {
 417                                 $this->laggedReplicaMode = true;
 418                         }
 419                 }
 420
 421                 $serverName = $this->getServerName( $i );
 422                 $this->connLogger->debug( __METHOD__ . ": using server $serverName for group '$group'" );
 423
 424                 return $i;
 425         }
 426
 427         /**
 428          * @param array $loads List of server weights
 429          * @param string|bool $domain
 430          * @return array (reader index, lagged replica mode) or false on failure
 431          */
 432         private function pickReaderIndex( array $loads, $domain = false ) {
 433                 if ( !count( $loads ) ) {
 434                         throw new InvalidArgumentException( "Empty server array given to LoadBalancer" );
 435                 }
 436
 437                 /** @var int|bool $i Index of selected server */
 438                 $i = false;
 439                 /** @var bool $laggedReplicaMode Whether server is considered lagged */
 440                 $laggedReplicaMode = false;
 441
 442                 // Quickly look through the available servers for a server that meets criteria...
 443                 $currentLoads = $loads;
 444                 while ( count( $currentLoads ) ) {
 445                         if ( $this->allowLagged || $laggedReplicaMode ) {
 446                                 $i = ArrayUtils::pickRandom( $currentLoads );
 447                         } else {
 448                                 $i = false;
 449                                 if ( $this->waitForPos && $this->waitForPos->asOfTime() ) {
 450                                         // "chronologyCallback" sets "waitForPos" for session consistency.
 451                                         // This triggers doWait() after connect, so it's especially good to
 452                                         // avoid lagged servers so as to avoid excessive delay in that method.
 453                                         $ago = microtime( true ) - $this->waitForPos->asOfTime();
 454                                         // Aim for <= 1 second of waiting (being too picky can backfire)
 455                                         $i = $this->getRandomNonLagged( $currentLoads, $domain, $ago + 1 );
 456                                 }
 457                                 if ( $i === false ) {
 458                                         // Any server with less lag than it's 'max lag' param is preferable
 459                                         $i = $this->getRandomNonLagged( $currentLoads, $domain );
 460                                 }
 461                                 if ( $i === false && count( $currentLoads ) != 0 ) {
 462                                         // All replica DBs lagged. Switch to read-only mode
 463                                         $this->replLogger->error(
 464                                                 __METHOD__ . ": all replica DBs lagged. Switch to read-only mode" );
 465                                         $i = ArrayUtils::pickRandom( $currentLoads );
 466                                         $laggedReplicaMode = true;
 467                                 }
 468                         }
 469
 470                         if ( $i === false ) {
 471                                 // pickRandom() returned false.
 472                                 // This is permanent and means the configuration or the load monitor
 473                                 // wants us to return false.
 474                                 $this->connLogger->debug( __METHOD__ . ": pickRandom() returned false" );
 475
 476                                 return [ false, false ];
 477                         }
 478
 479                         $serverName = $this->getServerName( $i );
 480                         $this->connLogger->debug( __METHOD__ . ": Using reader #$i: $serverName..." );
 481
 482                         $conn = $this->openConnection( $i, $domain );
 483                         if ( !$conn ) {
 484                                 $this->connLogger->warning( __METHOD__ . ": Failed connecting to $i/$domain" );
 485                                 unset( $currentLoads[$i] ); // avoid this server next iteration
 486                                 $i = false;
 487                                 continue;
 488                         }
 489
 490                         // Decrement reference counter, we are finished with this connection.
 491                         // It will be incremented for the caller later.
 492                         if ( $domain !== false ) {
 493                                 $this->reuseConnection( $conn );
 494                         }
 495
 496                         // Return this server
 497                         break;
 498                 }
 499
 500                 // If all servers were down, quit now
 501                 if ( !count( $currentLoads ) ) {
 502                         $this->connLogger->error( __METHOD__ . ": all servers down" );
 503                 }
 504
 505                 return [ $i, $laggedReplicaMode ];
 506         }
 507
 508         public function waitFor( $pos ) {
 509                 $oldPos = $this->waitForPos;
 510                 try {
 511                         $this->waitForPos = $pos;
 512                         // If a generic reader connection was already established, then wait now
 513                         $i = $this->readIndex;
 514                         if ( $i > 0 ) {
 515                                 if ( !$this->doWait( $i ) ) {
 516                                         $this->laggedReplicaMode = true;
 517                                 }
 518                         }
 519                 } finally {
 520                         // Restore the older position if it was higher since this is used for lag-protection
 521                         $this->setWaitForPositionIfHigher( $oldPos );
 522                 }
 523         }
 524
 525         public function waitForOne( $pos, $timeout = null ) {
 526                 $oldPos = $this->waitForPos;
 527                 try {
 528                         $this->waitForPos = $pos;
 529
 530                         $i = $this->readIndex;
 531                         if ( $i <= 0 ) {
 532                                 // Pick a generic replica DB if there isn't one yet
 533                                 $readLoads = $this->loads;
 534                                 unset( $readLoads[$this->getWriterIndex()] ); // replica DBs only
 535                                 $readLoads = array_filter( $readLoads ); // with non-zero load
 536                                 $i = ArrayUtils::pickRandom( $readLoads );
 537                         }
 538
 539                         if ( $i > 0 ) {
 540                                 $ok = $this->doWait( $i, true, $timeout );
 541                         } else {
 542                                 $ok = true; // no applicable loads
 543                         }
 544                 } finally {
 545                         # Restore the old position, as this is not used for lag-protection but for throttling
 546                         $this->waitForPos = $oldPos;
 547                 }
 548
 549                 return $ok;
 550         }
 551
 552         public function waitForAll( $pos, $timeout = null ) {
 553                 $timeout = $timeout ?: $this->waitTimeout;
 554
 555                 $oldPos = $this->waitForPos;
 556                 try {
 557                         $this->waitForPos = $pos;
 558                         $serverCount = count( $this->servers );
 559
 560                         $ok = true;
 561                         for ( $i = 1; $i < $serverCount; $i++ ) {
 562                                 if ( $this->loads[$i] > 0 ) {
 563                                         $start = microtime( true );
 564                                         $ok = $this->doWait( $i, true, $timeout ) && $ok;
 565                                         $timeout -= intval( microtime( true ) - $start );
 566                                         if ( $timeout <= 0 ) {
 567                                                 break; // timeout reached
 568                                         }
 569                                 }
 570                         }
 571                 } finally {
 572                         # Restore the old position, as this is not used for lag-protection but for throttling
 573                         $this->waitForPos = $oldPos;
 574                 }
 575
 576                 return $ok;
 577         }
 578
 579         /**
 580          * @param DBMasterPos|bool $pos
 581          */
 582         private function setWaitForPositionIfHigher( $pos ) {
 583                 if ( !$pos ) {
 584                         return;
 585                 }
 586
 587                 if ( !$this->waitForPos || $pos->hasReached( $this->waitForPos ) ) {
 588                         $this->waitForPos = $pos;
 589                 }
 590         }
 591
 592         public function getAnyOpenConnection( $i, $flags = 0 ) {
 593                 $autocommit = ( ( $flags & self::CONN_TRX_AUTOCOMMIT ) == self::CONN_TRX_AUTOCOMMIT );
 594                 foreach ( $this->conns as $connsByServer ) {
 595                         if ( !isset( $connsByServer[$i] ) ) {
 596                                 continue;
 597                         }
 598
 599                         foreach ( $connsByServer[$i] as $conn ) {
 600                                 if ( !$autocommit || $conn->getLBInfo( 'autoCommitOnly' ) ) {
 601                                         return $conn;
 602                                 }
 603                         }
 604                 }
 605
 606                 return false;
 607         }
 608
 609         /**
 610          * Wait for a given replica DB to catch up to the master pos stored in $this
 611          * @param int $index Server index
 612          * @param bool $open Check the server even if a new connection has to be made
 613          * @param int $timeout Max seconds to wait; default is "waitTimeout" given to __construct()
 614          * @return bool
 615          */
 616         protected function doWait( $index, $open = false, $timeout = null ) {
 617                 $timeout = max( 1, intval( $timeout ?: $this->waitTimeout ) );
 618
 619                 // Check if we already know that the DB has reached this point
 620                 $server = $this->getServerName( $index );
 621                 $key = $this->srvCache->makeGlobalKey( __CLASS__, 'last-known-pos', $server, 'v1' );
 622                 /** @var DBMasterPos $knownReachedPos */
 623                 $knownReachedPos = $this->srvCache->get( $key );
 624                 if (
 625                         $knownReachedPos instanceof DBMasterPos &&
 626                         $knownReachedPos->hasReached( $this->waitForPos )
 627                 ) {
 628                         $this->replLogger->debug(
 629                                 __METHOD__ .
 630                                 ': replica DB {dbserver} known to be caught up (pos >= $knownReachedPos).',
 631                                 [ 'dbserver' => $server ]
 632                         );
 633                         return true;
 634                 }
 635
 636                 // Find a connection to wait on, creating one if needed and allowed
 637                 $close = false; // close the connection afterwards
 638                 $conn = $this->getAnyOpenConnection( $index );
 639                 if ( !$conn ) {
 640                         if ( !$open ) {
 641                                 $this->replLogger->debug(
 642                                         __METHOD__ . ': no connection open for {dbserver}',
 643                                         [ 'dbserver' => $server ]
 644                                 );
 645
 646                                 return false;
 647                         } else {
 648                                 $conn = $this->openConnection( $index, self::DOMAIN_ANY );
 649                                 if ( !$conn ) {
 650                                         $this->replLogger->warning(
 651                                                 __METHOD__ . ': failed to connect to {dbserver}',
 652                                                 [ 'dbserver' => $server ]
 653                                         );
 654
 655                                         return false;
 656                                 }
 657                                 // Avoid connection spam in waitForAll() when connections
 658                                 // are made just for the sake of doing this lag check.
 659                                 $close = true;
 660                         }
 661                 }
 662
 663                 $this->replLogger->info(
 664                         __METHOD__ .
 665                         ': waiting for replica DB {dbserver} to catch up...',
 666                         [ 'dbserver' => $server ]
 667                 );
 668
 669                 $result = $conn->masterPosWait( $this->waitForPos, $timeout );
 670
 671                 if ( $result === null ) {
 672                         $this->replLogger->warning(
 673                                 __METHOD__ . ': Errored out waiting on {host} pos {pos}',
 674                                 [
 675                                         'host' => $server,
 676                                         'pos' => $this->waitForPos,
 677                                         'trace' => ( new RuntimeException() )->getTraceAsString()
 678                                 ]
 679                         );
 680                         $ok = false;
 681                 } elseif ( $result == -1 ) {
 682                         $this->replLogger->warning(
 683                                 __METHOD__ . ': Timed out waiting on {host} pos {pos}',
 684                                 [
 685                                         'host' => $server,
 686                                         'pos' => $this->waitForPos,
 687                                         'trace' => ( new RuntimeException() )->getTraceAsString()
 688                                 ]
 689                         );
 690                         $ok = false;
 691                 } else {
 692                         $this->replLogger->debug( __METHOD__ . ": done waiting" );
 693                         $ok = true;
 694                         // Remember that the DB reached this point
 695                         $this->srvCache->set( $key, $this->waitForPos, BagOStuff::TTL_DAY );
 696                 }
 697
 698                 if ( $close ) {
 699                         $this->closeConnection( $conn );
 700                 }
 701
 702                 return $ok;
 703         }
 704
 705         public function getConnection( $i, $groups = [], $domain = false, $flags = 0 ) {
 706                 if ( $i === null || $i === false ) {
 707                         throw new InvalidArgumentException( 'Attempt to call ' . __METHOD__ .
 708                                 ' with invalid server index' );
 709                 }
 710
 711                 if ( $this->localDomain->equals( $domain ) || $domain === $this->localDomainIdAlias ) {
 712                         $domain = false; // local connection requested
 713                 }
 714
 715                 if ( ( $flags & self::CONN_TRX_AUTOCOMMIT ) === self::CONN_TRX_AUTOCOMMIT ) {
 716                         // Assuming all servers are of the same type (or similar), which is overwhelmingly
 717                         // the case, use the master server information to get the attributes. The information
 718                         // for $i cannot be used since it might be DB_REPLICA, which might require connection
 719                         // attempts in order to be resolved into a real server index.
 720                         $attributes = $this->getServerAttributes( $this->getWriterIndex() );
 721                         if ( $attributes[Database::ATTR_DB_LEVEL_LOCKING] ) {
 722                                 // Callers sometimes want to (a) escape REPEATABLE-READ stateness without locking
 723                                 // rows (e.g. FOR UPDATE) or (b) make small commits during a larger transactions
 724                                 // to reduce lock contention. None of these apply for sqlite and using separate
 725                                 // connections just causes self-deadlocks.
 726                                 $flags &= ~self::CONN_TRX_AUTOCOMMIT;
 727                                 $this->connLogger->info( __METHOD__ .
 728                                         ': ignoring CONN_TRX_AUTOCOMMIT to avoid deadlocks.' );
 729                         }
 730                 }
 731
 732                 $groups = ( $groups === false || $groups === [] )
 733                         ? [ false ] // check one "group": the generic pool
 734                         : (array)$groups;
 735
 736                 $masterOnly = ( $i == self::DB_MASTER || $i == $this->getWriterIndex() );
 737                 $oldConnsOpened = $this->connsOpened; // connections open now
 738
 739                 if ( $i == self::DB_MASTER ) {
 740                         $i = $this->getWriterIndex();
 741                 } elseif ( $i == self::DB_REPLICA ) {
 742                         # Try to find an available server in any the query groups (in order)
 743                         foreach ( $groups as $group ) {
 744                                 $groupIndex = $this->getReaderIndex( $group, $domain );
 745                                 if ( $groupIndex !== false ) {
 746                                         $i = $groupIndex;
 747                                         break;
 748                                 }
 749                         }
 750                 }
 751
 752                 # Operation-based index
 753                 if ( $i == self::DB_REPLICA ) {
 754                         $this->lastError = 'Unknown error'; // reset error string
 755                         # Try the general server pool if $groups are unavailable.
 756                         $i = ( $groups === [ false ] )
 757                                 ? false // don't bother with this if that is what was tried above
 758                                 : $this->getReaderIndex( false, $domain );
 759                         # Couldn't find a working server in getReaderIndex()?
 760                         if ( $i === false ) {
 761                                 $this->lastError = 'No working replica DB server: ' . $this->lastError;
 762                                 // Throw an exception
 763                                 $this->reportConnectionError();
 764                                 return null; // not reached
 765                         }
 766                 }
 767
 768                 # Now we have an explicit index into the servers array
 769                 $conn = $this->openConnection( $i, $domain, $flags );
 770                 if ( !$conn ) {
 771                         // Throw an exception
 772                         $this->reportConnectionError();
 773                         return null; // not reached
 774                 }
 775
 776                 # Profile any new connections that happen
 777                 if ( $this->connsOpened > $oldConnsOpened ) {
 778                         $host = $conn->getServer();
 779                         $dbname = $conn->getDBname();
 780                         $this->trxProfiler->recordConnection( $host, $dbname, $masterOnly );
 781                 }
 782
 783                 if ( $masterOnly ) {
 784                         # Make master-requested DB handles inherit any read-only mode setting
 785                         $conn->setLBInfo( 'readOnlyReason', $this->getReadOnlyReason( $domain, $conn ) );
 786                 }
 787
 788                 return $conn;
 789         }
 790
 791         public function reuseConnection( IDatabase $conn ) {
 792                 $serverIndex = $conn->getLBInfo( 'serverIndex' );
 793                 $refCount = $conn->getLBInfo( 'foreignPoolRefCount' );
 794                 if ( $serverIndex === null || $refCount === null ) {
 795                         /**
 796                          * This can happen in code like:
 797                          *   foreach ( $dbs as $db ) {
 798                          *     $conn = $lb->getConnection( $lb::DB_REPLICA, [], $db );
 799                          *     ...
 800                          *     $lb->reuseConnection( $conn );
 801                          *   }
 802                          * When a connection to the local DB is opened in this way, reuseConnection()
 803                          * should be ignored
 804                          */
 805                         return;
 806                 } elseif ( $conn instanceof DBConnRef ) {
 807                         // DBConnRef already handles calling reuseConnection() and only passes the live
 808                         // Database instance to this method. Any caller passing in a DBConnRef is broken.
 809                         $this->connLogger->error(
 810                                 __METHOD__ . ": got DBConnRef instance.\n" .
 811                                 ( new RuntimeException() )->getTraceAsString() );
 812
 813                         return;
 814                 }
 815
 816                 if ( $this->disabled ) {
 817                         return; // DBConnRef handle probably survived longer than the LoadBalancer
 818                 }
 819
 820                 if ( $conn->getLBInfo( 'autoCommitOnly' ) ) {
 821                         $connFreeKey = self::KEY_FOREIGN_FREE_NOROUND;
 822                         $connInUseKey = self::KEY_FOREIGN_INUSE_NOROUND;
 823                 } else {
 824                         $connFreeKey = self::KEY_FOREIGN_FREE;
 825                         $connInUseKey = self::KEY_FOREIGN_INUSE;
 826                 }
 827
 828                 $domain = $conn->getDomainID();
 829                 if ( !isset( $this->conns[$connInUseKey][$serverIndex][$domain] ) ) {
 830                         throw new InvalidArgumentException( __METHOD__ .
 831                                 ": connection $serverIndex/$domain not found; it may have already been freed." );
 832                 } elseif ( $this->conns[$connInUseKey][$serverIndex][$domain] !== $conn ) {
 833                         throw new InvalidArgumentException( __METHOD__ .
 834                                 ": connection $serverIndex/$domain mismatched; it may have already been freed." );
 835                 }
 836
 837                 $conn->setLBInfo( 'foreignPoolRefCount', --$refCount );
 838                 if ( $refCount <= 0 ) {
 839                         $this->conns[$connFreeKey][$serverIndex][$domain] = $conn;
 840                         unset( $this->conns[$connInUseKey][$serverIndex][$domain] );
 841                         if ( !$this->conns[$connInUseKey][$serverIndex] ) {
 842                                 unset( $this->conns[$connInUseKey][$serverIndex] ); // clean up
 843                         }
 844                         $this->connLogger->debug( __METHOD__ . ": freed connection $serverIndex/$domain" );
 845                 } else {
 846                         $this->connLogger->debug( __METHOD__ .
 847                                 ": reference count for $serverIndex/$domain reduced to $refCount" );
 848                 }
 849         }
 850
 851         public function getConnectionRef( $db, $groups = [], $domain = false, $flags = 0 ) {
 852                 $domain = ( $domain !== false ) ? $domain : $this->localDomain;
 853
 854                 return new DBConnRef( $this, $this->getConnection( $db, $groups, $domain, $flags ) );
 855         }
 856
 857         public function getLazyConnectionRef( $db, $groups = [], $domain = false, $flags = 0 ) {
 858                 $domain = ( $domain !== false ) ? $domain : $this->localDomain;
 859
 860                 return new DBConnRef( $this, [ $db, $groups, $domain, $flags ] );
 861         }
 862
 863         public function getMaintenanceConnectionRef( $db, $groups = [], $domain = false, $flags = 0 ) {
 864                 $domain = ( $domain !== false ) ? $domain : $this->localDomain;
 865
 866                 return new MaintainableDBConnRef(
 867                         $this, $this->getConnection( $db, $groups, $domain, $flags ) );
 868         }
 869
 870         public function openConnection( $i, $domain = false, $flags = 0 ) {
 871                 if ( $this->localDomain->equals( $domain ) || $domain === $this->localDomainIdAlias ) {
 872                         $domain = false; // local connection requested
 873                 }
 874
 875                 if ( !$this->connectionAttempted && $this->chronologyCallback ) {
 876                         $this->connLogger->debug( __METHOD__ . ': calling initLB() before first connection.' );
 877                         // Load any "waitFor" positions before connecting so that doWait() is triggered
 878                         $this->connectionAttempted = true;
 879                         call_user_func( $this->chronologyCallback, $this );
 880                 }
 881
 882                 // Check if an auto-commit connection is being requested. If so, it will not reuse the
 883                 // main set of DB connections but rather its own pool since:
 884                 // a) those are usually set to implicitly use transaction rounds via DBO_TRX
 885                 // b) those must support the use of explicit transaction rounds via beginMasterChanges()
 886                 $autoCommit = ( ( $flags & self::CONN_TRX_AUTOCOMMIT ) == self::CONN_TRX_AUTOCOMMIT );
 887
 888                 if ( $domain !== false ) {
 889                         // Connection is to a foreign domain
 890                         $conn = $this->openForeignConnection( $i, $domain, $flags );
 891                 } else {
 892                         // Connection is to the local domain
 893                         $connKey = $autoCommit ? self::KEY_LOCAL_NOROUND : self::KEY_LOCAL;
 894                         if ( isset( $this->conns[$connKey][$i][0] ) ) {
 895                                 $conn = $this->conns[$connKey][$i][0];
 896                         } else {
 897                                 if ( !isset( $this->servers[$i] ) || !is_array( $this->servers[$i] ) ) {
 898                                         throw new InvalidArgumentException( "No server with index '$i'." );
 899                                 }
 900                                 // Open a new connection
 901                                 $server = $this->servers[$i];
 902                                 $server['serverIndex'] = $i;
 903                                 $server['autoCommitOnly'] = $autoCommit;
 904                                 if ( $this->localDomain->getDatabase() !== null ) {
 905                                         // Use the local domain table prefix if the local domain is specified
 906                                         $server['tablePrefix'] = $this->localDomain->getTablePrefix();
 907                                 }
 908                                 $conn = $this->reallyOpenConnection( $server, $this->localDomain );
 909                                 $host = $this->getServerName( $i );
 910                                 if ( $conn->isOpen() ) {
 911                                         $this->connLogger->debug(
 912                                                 __METHOD__ . ": connected to database $i at '$host'." );
 913                                         $this->conns[$connKey][$i][0] = $conn;
 914                                 } else {
 915                                         $this->connLogger->warning(
 916                                                 __METHOD__ . ": failed to connect to database $i at '$host'." );
 917                                         $this->errorConnection = $conn;
 918                                         $conn = false;
 919                                 }
 920                         }
 921                 }
 922
 923                 if ( $conn instanceof IDatabase && !$conn->isOpen() ) {
 924                         // Connection was made but later unrecoverably lost for some reason.
 925                         // Do not return a handle that will just throw exceptions on use,
 926                         // but let the calling code (e.g. getReaderIndex) try another server.
 927                         // See DatabaseMyslBase::ping() for how this can happen.
 928                         $this->errorConnection = $conn;
 929                         $conn = false;
 930                 }
 931
 932                 if ( $autoCommit && $conn instanceof IDatabase ) {
 933                         $conn->clearFlag( $conn::DBO_TRX ); // auto-commit mode
 934                 }
 935
 936                 return $conn;
 937         }
 938
 939         /**
 940          * Open a connection to a foreign DB, or return one if it is already open.
 941          *
 942          * Increments a reference count on the returned connection which locks the
 943          * connection to the requested domain. This reference count can be
 944          * decremented by calling reuseConnection().
 945          *
 946          * If a connection is open to the appropriate server already, but with the wrong
 947          * database, it will be switched to the right database and returned, as long as
 948          * it has been freed first with reuseConnection().
 949          *
 950          * On error, returns false, and the connection which caused the
 951          * error will be available via $this->errorConnection.
 952          *
 953          * @note If disable() was called on this LoadBalancer, this method will throw a DBAccessError.
 954          *
 955          * @param int $i Server index
 956          * @param string $domain Domain ID to open
 957          * @param int $flags Class CONN_* constant bitfield
 958          * @return Database
 959          */
 960         private function openForeignConnection( $i, $domain, $flags = 0 ) {
 961                 $domainInstance = DatabaseDomain::newFromId( $domain );
 962                 $dbName = $domainInstance->getDatabase();
 963                 $prefix = $domainInstance->getTablePrefix();
 964                 $autoCommit = ( ( $flags & self::CONN_TRX_AUTOCOMMIT ) == self::CONN_TRX_AUTOCOMMIT );
 965
 966                 if ( $autoCommit ) {
 967                         $connFreeKey = self::KEY_FOREIGN_FREE_NOROUND;
 968                         $connInUseKey = self::KEY_FOREIGN_INUSE_NOROUND;
 969                 } else {
 970                         $connFreeKey = self::KEY_FOREIGN_FREE;
 971                         $connInUseKey = self::KEY_FOREIGN_INUSE;
 972                 }
 973
 974                 if ( isset( $this->conns[$connInUseKey][$i][$domain] ) ) {
 975                         // Reuse an in-use connection for the same domain
 976                         $conn = $this->conns[$connInUseKey][$i][$domain];
 977                         $this->connLogger->debug( __METHOD__ . ": reusing connection $i/$domain" );
 978                 } elseif ( isset( $this->conns[$connFreeKey][$i][$domain] ) ) {
 979                         // Reuse a free connection for the same domain
 980                         $conn = $this->conns[$connFreeKey][$i][$domain];
 981                         unset( $this->conns[$connFreeKey][$i][$domain] );
 982                         $this->conns[$connInUseKey][$i][$domain] = $conn;
 983                         $this->connLogger->debug( __METHOD__ . ": reusing free connection $i/$domain" );
 984                 } elseif ( !empty( $this->conns[$connFreeKey][$i] ) ) {
 985                         // Reuse a free connection from another domain
 986                         $conn = reset( $this->conns[$connFreeKey][$i] );
 987                         $oldDomain = key( $this->conns[$connFreeKey][$i] );
 988                         if ( strlen( $dbName ) && !$conn->selectDB( $dbName ) ) {
 989                                 $this->lastError = "Error selecting database '$dbName' on server " .
 990                                         $conn->getServer() . " from client host {$this->host}";
 991                                 $this->errorConnection = $conn;
 992                                 $conn = false;
 993                         } else {
 994                                 $conn->tablePrefix( $prefix );
 995                                 unset( $this->conns[$connFreeKey][$i][$oldDomain] );
 996                                 // Note that if $domain is an empty string, getDomainID() might not match it
 997                                 $this->conns[$connInUseKey][$i][$conn->getDomainId()] = $conn;
 998                                 $this->connLogger->debug( __METHOD__ .
 999                                         ": reusing free connection from $oldDomain for $domain" );
1000                         }
1001                 } else {
1002                         if ( !isset( $this->servers[$i] ) || !is_array( $this->servers[$i] ) ) {
1003                                 throw new InvalidArgumentException( "No server with index '$i'." );
1004                         }
1005                         // Open a new connection
1006                         $server = $this->servers[$i];
1007                         $server['serverIndex'] = $i;
1008                         $server['foreignPoolRefCount'] = 0;
1009                         $server['foreign'] = true;
1010                         $server['autoCommitOnly'] = $autoCommit;
1011                         $conn = $this->reallyOpenConnection( $server, $domainInstance );
1012                         if ( !$conn->isOpen() ) {
1013                                 $this->connLogger->warning( __METHOD__ . ": connection error for $i/$domain" );
1014                                 $this->errorConnection = $conn;
1015                                 $conn = false;
1016                         } else {
1017                                 $conn->tablePrefix( $prefix ); // as specified
1018                                 // Note that if $domain is an empty string, getDomainID() might not match it
1019                                 $this->conns[$connInUseKey][$i][$conn->getDomainID()] = $conn;
1020                                 $this->connLogger->debug( __METHOD__ . ": opened new connection for $i/$domain" );
1021                         }
1022                 }
1023
1024                 // Increment reference count
1025                 if ( $conn instanceof IDatabase ) {
1026                         $refCount = $conn->getLBInfo( 'foreignPoolRefCount' );
1027                         $conn->setLBInfo( 'foreignPoolRefCount', $refCount + 1 );
1028                 }
1029
1030                 return $conn;
1031         }
1032
1033         public function getServerAttributes( $i ) {
1034                 return Database::attributesFromType(
1035                         $this->getServerType( $i ),
1036                         isset( $this->servers[$i]['driver'] ) ? $this->servers[$i]['driver'] : null
1037                 );
1038         }
1039
1040         /**
1041          * Test if the specified index represents an open connection
1042          *
1043          * @param int $index Server index
1044          * @access private
1045          * @return bool
1046          */
1047         private function isOpen( $index ) {
1048                 if ( !is_int( $index ) ) {
1049                         return false;
1050                 }
1051
1052                 return (bool)$this->getAnyOpenConnection( $index );
1053         }
1054
1055         /**
1056          * Open a new network connection to a server (uncached)
1057          *
1058          * Returns a Database object whether or not the connection was successful.
1059          *
1060          * @param array $server
1061          * @param DatabaseDomain $domainOverride Use an unspecified domain to not select any database
1062          * @return Database
1063          * @throws DBAccessError
1064          * @throws InvalidArgumentException
1065          */
1066         protected function reallyOpenConnection( array $server, DatabaseDomain $domainOverride ) {
1067                 if ( $this->disabled ) {
1068                         throw new DBAccessError();
1069                 }
1070
1071                 // Handle $domainOverride being a specified or an unspecified domain
1072                 if ( $domainOverride->getDatabase() === null ) {
1073                         // Normally, an RDBMS requires a DB name specified on connection and the $server
1074                         // configuration array is assumed to already specify an appropriate DB name.
1075                         if ( $server['type'] === 'mysql' ) {
1076                                 // For MySQL, DATABASE and SCHEMA are synonyms, connections need not specify a DB,
1077                                 // and the DB name in $server might not exist due to legacy reasons (the default
1078                                 // domain used to ignore the local LB domain, even when mismatched).
1079                                 $server['dbname'] = null;
1080                         }
1081                 } else {
1082                         $server['dbname'] = $domainOverride->getDatabase();
1083                         $server['schema'] = $domainOverride->getSchema();
1084                 }
1085
1086                 // Let the handle know what the cluster master is (e.g. "db1052")
1087                 $masterName = $this->getServerName( $this->getWriterIndex() );
1088                 $server['clusterMasterHost'] = $masterName;
1089
1090                 // Log when many connection are made on requests
1091                 if ( ++$this->connsOpened >= self::CONN_HELD_WARN_THRESHOLD ) {
1092                         $this->perfLogger->warning( __METHOD__ . ": " .
1093                                 "{$this->connsOpened}+ connections made (master=$masterName)" );
1094                 }
1095
1096                 $server['srvCache'] = $this->srvCache;
1097                 // Set loggers and profilers
1098                 $server['connLogger'] = $this->connLogger;
1099                 $server['queryLogger'] = $this->queryLogger;
1100                 $server['errorLogger'] = $this->errorLogger;
1101                 $server['deprecationLogger'] = $this->deprecationLogger;
1102                 $server['profiler'] = $this->profiler;
1103                 $server['trxProfiler'] = $this->trxProfiler;
1104                 // Use the same agent and PHP mode for all DB handles
1105                 $server['cliMode'] = $this->cliMode;
1106                 $server['agent'] = $this->agent;
1107                 // Use DBO_DEFAULT flags by default for LoadBalancer managed databases. Assume that the
1108                 // application calls LoadBalancer::commitMasterChanges() before the PHP script completes.
1109                 $server['flags'] = isset( $server['flags'] ) ? $server['flags'] : IDatabase::DBO_DEFAULT;
1110
1111                 // Create a live connection object
1112                 try {
1113                         $db = Database::factory( $server['type'], $server );
1114                 } catch ( DBConnectionError $e ) {
1115                         // FIXME: This is probably the ugliest thing I have ever done to
1116                         // PHP. I'm half-expecting it to segfault, just out of disgust. -- TS
1117                         $db = $e->db;
1118                 }
1119
1120                 $db->setLBInfo( $server );
1121                 $db->setLazyMasterHandle(
1122                         $this->getLazyConnectionRef( self::DB_MASTER, [], $db->getDomainID() )
1123                 );
1124                 $db->setTableAliases( $this->tableAliases );
1125                 $db->setIndexAliases( $this->indexAliases );
1126
1127                 if ( $server['serverIndex'] === $this->getWriterIndex() ) {
1128                         if ( $this->trxRoundId !== false ) {
1129                                 $this->applyTransactionRoundFlags( $db );
1130                         }
1131                         foreach ( $this->trxRecurringCallbacks as $name => $callback ) {
1132                                 $db->setTransactionListener( $name, $callback );
1133                         }
1134                 }
1135
1136                 return $db;
1137         }
1138
1139         /**
1140          * @throws DBConnectionError
1141          */
1142         private function reportConnectionError() {
1143                 $conn = $this->errorConnection; // the connection which caused the error
1144                 $context = [
1145                         'method' => __METHOD__,
1146                         'last_error' => $this->lastError,
1147                 ];
1148
1149                 if ( $conn instanceof IDatabase ) {
1150                         $context['db_server'] = $conn->getServer();
1151                         $this->connLogger->warning(
1152                                 __METHOD__ . ": connection error: {last_error} ({db_server})",
1153                                 $context
1154                         );
1155
1156                         throw new DBConnectionError( $conn, "{$this->lastError} ({$context['db_server']})" );
1157                 } else {
1158                         // No last connection, probably due to all servers being too busy
1159                         $this->connLogger->error(
1160                                 __METHOD__ .
1161                                 ": LB failure with no last connection. Connection error: {last_error}",
1162                                 $context
1163                         );
1164
1165                         // If all servers were busy, "lastError" will contain something sensible
1166                         throw new DBConnectionError( null, $this->lastError );
1167                 }
1168         }
1169
1170         public function getWriterIndex() {
1171                 return 0;
1172         }
1173
1174         public function haveIndex( $i ) {
1175                 return array_key_exists( $i, $this->servers );
1176         }
1177
1178         public function isNonZeroLoad( $i ) {
1179                 return array_key_exists( $i, $this->servers ) && $this->loads[$i] != 0;
1180         }
1181
1182         public function getServerCount() {
1183                 return count( $this->servers );
1184         }
1185
1186         public function getServerName( $i ) {
1187                 if ( isset( $this->servers[$i]['hostName'] ) ) {
1188                         $name = $this->servers[$i]['hostName'];
1189                 } elseif ( isset( $this->servers[$i]['host'] ) ) {
1190                         $name = $this->servers[$i]['host'];
1191                 } else {
1192                         $name = '';
1193                 }
1194
1195                 return ( $name != '' ) ? $name : 'localhost';
1196         }
1197
1198         public function getServerType( $i ) {
1199                 return isset( $this->servers[$i]['type'] ) ? $this->servers[$i]['type'] : 'unknown';
1200         }
1201
1202         public function getMasterPos() {
1203                 # If this entire request was served from a replica DB without opening a connection to the
1204                 # master (however unlikely that may be), then we can fetch the position from the replica DB.
1205                 $masterConn = $this->getAnyOpenConnection( $this->getWriterIndex() );
1206                 if ( !$masterConn ) {
1207                         $serverCount = count( $this->servers );
1208                         for ( $i = 1; $i < $serverCount; $i++ ) {
1209                                 $conn = $this->getAnyOpenConnection( $i );
1210                                 if ( $conn ) {
1211                                         return $conn->getReplicaPos();
1212                                 }
1213                         }
1214                 } else {
1215                         return $masterConn->getMasterPos();
1216                 }
1217
1218                 return false;
1219         }
1220
1221         public function disable() {
1222                 $this->closeAll();
1223                 $this->disabled = true;
1224         }
1225
1226         public function closeAll() {
1227                 $this->forEachOpenConnection( function ( IDatabase $conn ) {
1228                         $host = $conn->getServer();
1229                         $this->connLogger->debug(
1230                                 __METHOD__ . ": closing connection to database '$host'." );
1231                         $conn->close();
1232                 } );
1233
1234                 $this->conns = [
1235                         self::KEY_LOCAL => [],
1236                         self::KEY_FOREIGN_INUSE => [],
1237                         self::KEY_FOREIGN_FREE => [],
1238                         self::KEY_LOCAL_NOROUND => [],
1239                         self::KEY_FOREIGN_INUSE_NOROUND => [],
1240                         self::KEY_FOREIGN_FREE_NOROUND => []
1241                 ];
1242                 $this->connsOpened = 0;
1243         }
1244
1245         public function closeConnection( IDatabase $conn ) {
1246                 $serverIndex = $conn->getLBInfo( 'serverIndex' );
1247                 foreach ( $this->conns as $type => $connsByServer ) {
1248                         if ( !isset( $connsByServer[$serverIndex] ) ) {
1249                                 continue;
1250                         }
1251
1252                         foreach ( $connsByServer[$serverIndex] as $i => $trackedConn ) {
1253                                 if ( $conn === $trackedConn ) {
1254                                         $host = $this->getServerName( $i );
1255                                         $this->connLogger->debug(
1256                                                 __METHOD__ . ": closing connection to database $i at '$host'." );
1257                                         unset( $this->conns[$type][$serverIndex][$i] );
1258                                         --$this->connsOpened;
1259                                         break 2;
1260                                 }
1261                         }
1262                 }
1263
1264                 $conn->close();
1265         }
1266
1267         public function commitAll( $fname = __METHOD__ ) {
1268                 $this->commitMasterChanges( $fname );
1269                 $this->flushMasterSnapshots( $fname );
1270                 $this->flushReplicaSnapshots( $fname );
1271         }
1272
1273         public function finalizeMasterChanges() {
1274                 $this->assertTransactionRoundStage( [ self::ROUND_CURSORY, self::ROUND_FINALIZED ] );
1275
1276                 $this->trxRoundStage = self::ROUND_ERROR; // "failed" until proven otherwise
1277                 // Loop until callbacks stop adding callbacks on other connections
1278                 $total = 0;
1279                 do {
1280                         $count = 0; // callbacks execution attempts
1281                         $this->forEachOpenMasterConnection( function ( Database $conn ) use ( &$count ) {
1282                                 // Run any pre-commit callbacks while leaving the post-commit ones suppressed.
1283                                 // Any error should cause all (peer) transactions to be rolled back together.
1284                                 $count += $conn->runOnTransactionPreCommitCallbacks();
1285                         } );
1286                         $total += $count;
1287                 } while ( $count > 0 );
1288                 // Defer post-commit callbacks until after COMMIT/ROLLBACK happens on all handles
1289                 $this->forEachOpenMasterConnection( function ( Database $conn ) {
1290                         $conn->setTrxEndCallbackSuppression( true );
1291                 } );
1292                 $this->trxRoundStage = self::ROUND_FINALIZED;
1293
1294                 return $total;
1295         }
1296
1297         public function approveMasterChanges( array $options ) {
1298                 $this->assertTransactionRoundStage( self::ROUND_FINALIZED );
1299
1300                 $limit = isset( $options['maxWriteDuration'] ) ? $options['maxWriteDuration'] : 0;
1301
1302                 $this->trxRoundStage = self::ROUND_ERROR; // "failed" until proven otherwise
1303                 $this->forEachOpenMasterConnection( function ( IDatabase $conn ) use ( $limit ) {
1304                         // If atomic sections or explicit transactions are still open, some caller must have
1305                         // caught an exception but failed to properly rollback any changes. Detect that and
1306                         // throw and error (causing rollback).
1307                         if ( $conn->explicitTrxActive() ) {
1308                                 throw new DBTransactionError(
1309                                         $conn,
1310                                         "Explicit transaction still active. A caller may have caught an error."
1311                                 );
1312                         }
1313                         // Assert that the time to replicate the transaction will be sane.
1314                         // If this fails, then all DB transactions will be rollback back together.
1315                         $time = $conn->pendingWriteQueryDuration( $conn::ESTIMATE_DB_APPLY );
1316                         if ( $limit > 0 && $time > $limit ) {
1317                                 throw new DBTransactionSizeError(
1318                                         $conn,
1319                                         "Transaction spent $time second(s) in writes, exceeding the limit of $limit.",
1320                                         [ $time, $limit ]
1321                                 );
1322                         }
1323                         // If a connection sits idle while slow queries execute on another, that connection
1324                         // may end up dropped before the commit round is reached. Ping servers to detect this.
1325                         if ( $conn->writesOrCallbacksPending() && !$conn->ping() ) {
1326                                 throw new DBTransactionError(
1327                                         $conn,
1328                                         "A connection to the {$conn->getDBname()} database was lost before commit."
1329                                 );
1330                         }
1331                 } );
1332                 $this->trxRoundStage = self::ROUND_APPROVED;
1333         }
1334
1335         public function beginMasterChanges( $fname = __METHOD__ ) {
1336                 if ( $this->trxRoundId !== false ) {
1337                         throw new DBTransactionError(
1338                                 null,
1339                                 "$fname: Transaction round '{$this->trxRoundId}' already started."
1340                         );
1341                 }
1342                 $this->assertTransactionRoundStage( self::ROUND_CURSORY );
1343
1344                 // Clear any empty transactions (no writes/callbacks) from the implicit round
1345                 $this->flushMasterSnapshots( $fname );
1346
1347                 $this->trxRoundId = $fname;
1348                 $this->trxRoundStage = self::ROUND_ERROR; // "failed" until proven otherwise
1349                 // Mark applicable handles as participating in this explicit transaction round.
1350                 // For each of these handles, any writes and callbacks will be tied to a single
1351                 // transaction. The (peer) handles will reject begin()/commit() calls unless they
1352                 // are part of an en masse commit or an en masse rollback.
1353                 $this->forEachOpenMasterConnection( function ( Database $conn ) {
1354                         $this->applyTransactionRoundFlags( $conn );
1355                 } );
1356                 $this->trxRoundStage = self::ROUND_CURSORY;
1357         }
1358
1359         public function commitMasterChanges( $fname = __METHOD__ ) {
1360                 $this->assertTransactionRoundStage( self::ROUND_APPROVED );
1361
1362                 $failures = [];
1363
1364                 /** @noinspection PhpUnusedLocalVariableInspection */
1365                 $scope = $this->getScopedPHPBehaviorForCommit(); // try to ignore client aborts
1366
1367                 $restore = ( $this->trxRoundId !== false );
1368                 $this->trxRoundId = false;
1369                 $this->trxRoundStage = self::ROUND_ERROR; // "failed" until proven otherwise
1370                 // Commit any writes and clear any snapshots as well (callbacks require AUTOCOMMIT).
1371                 // Note that callbacks should already be suppressed due to finalizeMasterChanges().
1372                 $this->forEachOpenMasterConnection(
1373                         function ( IDatabase $conn ) use ( $fname, &$failures ) {
1374                                 try {
1375                                         $conn->commit( $fname, $conn::FLUSHING_ALL_PEERS );
1376                                 } catch ( DBError $e ) {
1377                                         call_user_func( $this->errorLogger, $e );
1378                                         $failures[] = "{$conn->getServer()}: {$e->getMessage()}";
1379                                 }
1380                         }
1381                 );
1382                 if ( $failures ) {
1383                         throw new DBTransactionError(
1384                                 null,
1385                                 "$fname: Commit failed on server(s) " . implode( "\n", array_unique( $failures ) )
1386                         );
1387                 }
1388                 if ( $restore ) {
1389                         // Unmark handles as participating in this explicit transaction round
1390                         $this->forEachOpenMasterConnection( function ( Database $conn ) {
1391                                 $this->undoTransactionRoundFlags( $conn );
1392                         } );
1393                 }
1394                 $this->trxRoundStage = self::ROUND_COMMIT_CALLBACKS;
1395         }
1396
1397         public function runMasterTransactionIdleCallbacks() {
1398                 if ( $this->trxRoundStage === self::ROUND_COMMIT_CALLBACKS ) {
1399                         $type = IDatabase::TRIGGER_COMMIT;
1400                 } elseif ( $this->trxRoundStage === self::ROUND_ROLLBACK_CALLBACKS ) {
1401                         $type = IDatabase::TRIGGER_ROLLBACK;
1402                 } else {
1403                         throw new DBTransactionError(
1404                                 null,
1405                                 "Transaction should be in the callback stage (not '{$this->trxRoundStage}')"
1406                         );
1407                 }
1408
1409                 $oldStage = $this->trxRoundStage;
1410                 $this->trxRoundStage = self::ROUND_ERROR; // "failed" until proven otherwise
1411
1412                 // Now that the COMMIT/ROLLBACK step is over, enable post-commit callback runs
1413                 $this->forEachOpenMasterConnection( function ( Database $conn ) {
1414                         $conn->setTrxEndCallbackSuppression( false );
1415                 } );
1416
1417                 $e = null; // first exception
1418                 // Loop until callbacks stop adding callbacks on other connections
1419                 do {
1420                         // Run any pending callbacks for each connection...
1421                         $count = 0; // callback execution attempts
1422                         $this->forEachOpenMasterConnection(
1423                                 function ( Database $conn ) use ( $type, &$e, &$count ) {
1424                                         if ( $conn->trxLevel() ) {
1425                                                 return; // retry in the next iteration, after commit() is called
1426                                         }
1427                                         try {
1428                                                 $count += $conn->runOnTransactionIdleCallbacks( $type );
1429                                         } catch ( Exception $ex ) {
1430                                                 $e = $e ?: $ex;
1431                                         }
1432                                 }
1433                         );
1434                         // Clear out any active transactions left over from callbacks...
1435                         $this->forEachOpenMasterConnection( function ( Database $conn ) use ( &$e ) {
1436                                 if ( $conn->writesPending() ) {
1437                                         // A callback from another handle wrote to this one and DBO_TRX is set
1438                                         $this->queryLogger->warning( __METHOD__ . ": found writes pending." );
1439                                         $fnames = implode( ', ', $conn->pendingWriteAndCallbackCallers() );
1440                                         $this->queryLogger->warning(
1441                                                 __METHOD__ . ": found writes pending ($fnames).",
1442                                                 [
1443                                                         'db_server' => $conn->getServer(),
1444                                                         'db_name' => $conn->getDBname()
1445                                                 ]
1446                                         );
1447                                 } elseif ( $conn->trxLevel() ) {
1448                                         // A callback from another handle read from this one and DBO_TRX is set,
1449                                         // which can easily happen if there is only one DB (no replicas)
1450                                         $this->queryLogger->debug( __METHOD__ . ": found empty transaction." );
1451                                 }
1452                                 try {
1453                                         $conn->commit( __METHOD__, $conn::FLUSHING_ALL_PEERS );
1454                                 } catch ( Exception $ex ) {
1455                                         $e = $e ?: $ex;
1456                                 }
1457                         } );
1458                 } while ( $count > 0 );
1459
1460                 $this->trxRoundStage = $oldStage;
1461
1462                 return $e;
1463         }
1464
1465         public function runMasterTransactionListenerCallbacks() {
1466                 if ( $this->trxRoundStage === self::ROUND_COMMIT_CALLBACKS ) {
1467                         $type = IDatabase::TRIGGER_COMMIT;
1468                 } elseif ( $this->trxRoundStage === self::ROUND_ROLLBACK_CALLBACKS ) {
1469                         $type = IDatabase::TRIGGER_ROLLBACK;
1470                 } else {
1471                         throw new DBTransactionError(
1472                                 null,
1473                                 "Transaction should be in the callback stage (not '{$this->trxRoundStage}')"
1474                         );
1475                 }
1476
1477                 $e = null;
1478
1479                 $this->trxRoundStage = self::ROUND_ERROR; // "failed" until proven otherwise
1480                 $this->forEachOpenMasterConnection( function ( Database $conn ) use ( $type, &$e ) {
1481                         try {
1482                                 $conn->runTransactionListenerCallbacks( $type );
1483                         } catch ( Exception $ex ) {
1484                                 $e = $e ?: $ex;
1485                         }
1486                 } );
1487                 $this->trxRoundStage = self::ROUND_CURSORY;
1488
1489                 return $e;
1490         }
1491
1492         public function rollbackMasterChanges( $fname = __METHOD__ ) {
1493                 $restore = ( $this->trxRoundId !== false );
1494                 $this->trxRoundId = false;
1495                 $this->trxRoundStage = self::ROUND_ERROR; // "failed" until proven otherwise
1496                 $this->forEachOpenMasterConnection( function ( IDatabase $conn ) use ( $fname ) {
1497                         $conn->rollback( $fname, $conn::FLUSHING_ALL_PEERS );
1498                 } );
1499                 if ( $restore ) {
1500                         // Unmark handles as participating in this explicit transaction round
1501                         $this->forEachOpenMasterConnection( function ( Database $conn ) {
1502                                 $this->undoTransactionRoundFlags( $conn );
1503                         } );
1504                 }
1505                 $this->trxRoundStage = self::ROUND_ROLLBACK_CALLBACKS;
1506         }
1507
1508         /**
1509          * @param string|string[] $stage
1510          */
1511         private function assertTransactionRoundStage( $stage ) {
1512                 $stages = (array)$stage;
1513
1514                 if ( !in_array( $this->trxRoundStage, $stages, true ) ) {
1515                         $stageList = implode(
1516                                 '/',
1517                                 array_map( function ( $v ) {
1518                                         return "'$v'";
1519                                 }, $stages )
1520                         );
1521                         throw new DBTransactionError(
1522                                 null,
1523                                 "Transaction round stage must be $stageList (not '{$this->trxRoundStage}')"
1524                         );
1525                 }
1526         }
1527
1528         /**
1529          * Make all DB servers with DBO_DEFAULT/DBO_TRX set join the transaction round
1530          *
1531          * Some servers may have neither flag enabled, meaning that they opt out of such
1532          * transaction rounds and remain in auto-commit mode. Such behavior might be desired
1533          * when a DB server is used for something like simple key/value storage.
1534          *
1535          * @param Database $conn
1536          */
1537         private function applyTransactionRoundFlags( Database $conn ) {
1538                 if ( $conn->getLBInfo( 'autoCommitOnly' ) ) {
1539                         return; // transaction rounds do not apply to these connections
1540                 }
1541
1542                 if ( $conn->getFlag( $conn::DBO_DEFAULT ) ) {
1543                         // DBO_TRX is controlled entirely by CLI mode presence with DBO_DEFAULT.
1544                         // Force DBO_TRX even in CLI mode since a commit round is expected soon.
1545                         $conn->setFlag( $conn::DBO_TRX, $conn::REMEMBER_PRIOR );
1546                 }
1547
1548                 if ( $conn->getFlag( $conn::DBO_TRX ) ) {
1549                         $conn->setLBInfo( 'trxRoundId', $this->trxRoundId );
1550                 }
1551         }
1552
1553         /**
1554          * @param Database $conn
1555          */
1556         private function undoTransactionRoundFlags( Database $conn ) {
1557                 if ( $conn->getLBInfo( 'autoCommitOnly' ) ) {
1558                         return; // transaction rounds do not apply to these connections
1559                 }
1560
1561                 if ( $conn->getFlag( $conn::DBO_TRX ) ) {
1562                         $conn->setLBInfo( 'trxRoundId', false );
1563                 }
1564
1565                 if ( $conn->getFlag( $conn::DBO_DEFAULT ) ) {
1566                         $conn->restoreFlags( $conn::RESTORE_PRIOR );
1567                 }
1568         }
1569
1570         public function flushReplicaSnapshots( $fname = __METHOD__ ) {
1571                 $this->forEachOpenReplicaConnection( function ( IDatabase $conn ) use ( $fname ) {
1572                         $conn->flushSnapshot( $fname );
1573                 } );
1574         }
1575
1576         public function flushMasterSnapshots( $fname = __METHOD__ ) {
1577                 $this->forEachOpenMasterConnection( function ( IDatabase $conn ) use ( $fname ) {
1578                         $conn->flushSnapshot( $fname );
1579                 } );
1580         }
1581
1582         /**
1583          * @return string
1584          * @since 1.32
1585          */
1586         public function getTransactionRoundStage() {
1587                 return $this->trxRoundStage;
1588         }
1589
1590         public function hasMasterConnection() {
1591                 return $this->isOpen( $this->getWriterIndex() );
1592         }
1593
1594         public function hasMasterChanges() {
1595                 $pending = 0;
1596                 $this->forEachOpenMasterConnection( function ( IDatabase $conn ) use ( &$pending ) {
1597                         $pending |= $conn->writesOrCallbacksPending();
1598                 } );
1599
1600                 return (bool)$pending;
1601         }
1602
1603         public function lastMasterChangeTimestamp() {
1604                 $lastTime = false;
1605                 $this->forEachOpenMasterConnection( function ( IDatabase $conn ) use ( &$lastTime ) {
1606                         $lastTime = max( $lastTime, $conn->lastDoneWrites() );
1607                 } );
1608
1609                 return $lastTime;
1610         }
1611
1612         public function hasOrMadeRecentMasterChanges( $age = null ) {
1613                 $age = ( $age === null ) ? $this->waitTimeout : $age;
1614
1615                 return ( $this->hasMasterChanges()
1616                         || $this->lastMasterChangeTimestamp() > microtime( true ) - $age );
1617         }
1618
1619         public function pendingMasterChangeCallers() {
1620                 $fnames = [];
1621                 $this->forEachOpenMasterConnection( function ( IDatabase $conn ) use ( &$fnames ) {
1622                         $fnames = array_merge( $fnames, $conn->pendingWriteCallers() );
1623                 } );
1624
1625                 return $fnames;
1626         }
1627
1628         public function getLaggedReplicaMode( $domain = false ) {
1629                 // No-op if there is only one DB (also avoids recursion)
1630                 if ( !$this->laggedReplicaMode && $this->getServerCount() > 1 ) {
1631                         try {
1632                                 // See if laggedReplicaMode gets set
1633                                 $conn = $this->getConnection( self::DB_REPLICA, false, $domain );
1634                                 $this->reuseConnection( $conn );
1635                         } catch ( DBConnectionError $e ) {
1636                                 // Avoid expensive re-connect attempts and failures
1637                                 $this->allReplicasDownMode = true;
1638                                 $this->laggedReplicaMode = true;
1639                         }
1640                 }
1641
1642                 return $this->laggedReplicaMode;
1643         }
1644
1645         public function laggedReplicaUsed() {
1646                 return $this->laggedReplicaMode;
1647         }
1648
1649         /**
1650          * @return bool
1651          * @since 1.27
1652          * @deprecated Since 1.28; use laggedReplicaUsed()
1653          */
1654         public function laggedSlaveUsed() {
1655                 return $this->laggedReplicaUsed();
1656         }
1657
1658         public function getReadOnlyReason( $domain = false, IDatabase $conn = null ) {
1659                 if ( $this->readOnlyReason !== false ) {
1660                         return $this->readOnlyReason;
1661                 } elseif ( $this->getLaggedReplicaMode( $domain ) ) {
1662                         if ( $this->allReplicasDownMode ) {
1663                                 return 'The database has been automatically locked ' .
1664                                         'until the replica database servers become available';
1665                         } else {
1666                                 return 'The database has been automatically locked ' .
1667                                         'while the replica database servers catch up to the master.';
1668                         }
1669                 } elseif ( $this->masterRunningReadOnly( $domain, $conn ) ) {
1670                         return 'The database master is running in read-only mode.';
1671                 }
1672
1673                 return false;
1674         }
1675
1676         /**
1677          * @param string $domain Domain ID, or false for the current domain
1678          * @param IDatabase|null $conn DB master connectionl used to avoid loops [optional]
1679          * @return bool
1680          */
1681         private function masterRunningReadOnly( $domain, IDatabase $conn = null ) {
1682                 $cache = $this->wanCache;
1683                 $masterServer = $this->getServerName( $this->getWriterIndex() );
1684
1685                 return (bool)$cache->getWithSetCallback(
1686                         $cache->makeGlobalKey( __CLASS__, 'server-read-only', $masterServer ),
1687                         self::TTL_CACHE_READONLY,
1688                         function () use ( $domain, $conn ) {
1689                                 $old = $this->trxProfiler->setSilenced( true );
1690                                 try {
1691                                         $dbw = $conn ?: $this->getConnection( self::DB_MASTER, [], $domain );
1692                                         $readOnly = (int)$dbw->serverIsReadOnly();
1693                                         if ( !$conn ) {
1694                                                 $this->reuseConnection( $dbw );
1695                                         }
1696                                 } catch ( DBError $e ) {
1697                                         $readOnly = 0;
1698                                 }
1699                                 $this->trxProfiler->setSilenced( $old );
1700                                 return $readOnly;
1701                         },
1702                         [ 'pcTTL' => $cache::TTL_PROC_LONG, 'busyValue' => 0 ]
1703                 );
1704         }
1705
1706         public function allowLagged( $mode = null ) {
1707                 if ( $mode === null ) {
1708                         return $this->allowLagged;
1709                 }
1710                 $this->allowLagged = $mode;
1711
1712                 return $this->allowLagged;
1713         }
1714
1715         public function pingAll() {
1716                 $success = true;
1717                 $this->forEachOpenConnection( function ( IDatabase $conn ) use ( &$success ) {
1718                         if ( !$conn->ping() ) {
1719                                 $success = false;
1720                         }
1721                 } );
1722
1723                 return $success;
1724         }
1725
1726         public function forEachOpenConnection( $callback, array $params = [] ) {
1727                 foreach ( $this->conns as $connsByServer ) {
1728                         foreach ( $connsByServer as $serverConns ) {
1729                                 foreach ( $serverConns as $conn ) {
1730                                         $mergedParams = array_merge( [ $conn ], $params );
1731                                         call_user_func_array( $callback, $mergedParams );
1732                                 }
1733                         }
1734                 }
1735         }
1736
1737         public function forEachOpenMasterConnection( $callback, array $params = [] ) {
1738                 $masterIndex = $this->getWriterIndex();
1739                 foreach ( $this->conns as $connsByServer ) {
1740                         if ( isset( $connsByServer[$masterIndex] ) ) {
1741                                 /** @var IDatabase $conn */
1742                                 foreach ( $connsByServer[$masterIndex] as $conn ) {
1743                                         $mergedParams = array_merge( [ $conn ], $params );
1744                                         call_user_func_array( $callback, $mergedParams );
1745                                 }
1746                         }
1747                 }
1748         }
1749
1750         public function forEachOpenReplicaConnection( $callback, array $params = [] ) {
1751                 foreach ( $this->conns as $connsByServer ) {
1752                         foreach ( $connsByServer as $i => $serverConns ) {
1753                                 if ( $i === $this->getWriterIndex() ) {
1754                                         continue; // skip master
1755                                 }
1756                                 foreach ( $serverConns as $conn ) {
1757                                         $mergedParams = array_merge( [ $conn ], $params );
1758                                         call_user_func_array( $callback, $mergedParams );
1759                                 }
1760                         }
1761                 }
1762         }
1763
1764         public function getMaxLag( $domain = false ) {
1765                 $maxLag = -1;
1766                 $host = '';
1767                 $maxIndex = 0;
1768
1769                 if ( $this->getServerCount() <= 1 ) {
1770                         return [ $host, $maxLag, $maxIndex ]; // no replication = no lag
1771                 }
1772
1773                 $lagTimes = $this->getLagTimes( $domain );
1774                 foreach ( $lagTimes as $i => $lag ) {
1775                         if ( $this->loads[$i] > 0 && $lag > $maxLag ) {
1776                                 $maxLag = $lag;
1777                                 $host = $this->servers[$i]['host'];
1778                                 $maxIndex = $i;
1779                         }
1780                 }
1781
1782                 return [ $host, $maxLag, $maxIndex ];
1783         }
1784
1785         public function getLagTimes( $domain = false ) {
1786                 if ( $this->getServerCount() <= 1 ) {
1787                         return [ $this->getWriterIndex() => 0 ]; // no replication = no lag
1788                 }
1789
1790                 $knownLagTimes = []; // map of (server index => 0 seconds)
1791                 $indexesWithLag = [];
1792                 foreach ( $this->servers as $i => $server ) {
1793                         if ( empty( $server['is static'] ) ) {
1794                                 $indexesWithLag[] = $i; // DB server might have replication lag
1795                         } else {
1796                                 $knownLagTimes[$i] = 0; // DB server is a non-replicating and read-only archive
1797                         }
1798                 }
1799
1800                 return $this->getLoadMonitor()->getLagTimes( $indexesWithLag, $domain ) + $knownLagTimes;
1801         }
1802
1803         public function safeGetLag( IDatabase $conn ) {
1804                 if ( $this->getServerCount() <= 1 ) {
1805                         return 0;
1806                 } else {
1807                         return $conn->getLag();
1808                 }
1809         }
1810
1811         /**
1812          * @param IDatabase $conn
1813          * @param DBMasterPos|bool $pos
1814          * @param int|null $timeout
1815          * @return bool
1816          */
1817         public function safeWaitForMasterPos( IDatabase $conn, $pos = false, $timeout = null ) {
1818                 $timeout = max( 1, $timeout ?: $this->waitTimeout );
1819
1820                 if ( $this->getServerCount() <= 1 || !$conn->getLBInfo( 'replica' ) ) {
1821                         return true; // server is not a replica DB
1822                 }
1823
1824                 if ( !$pos ) {
1825                         // Get the current master position, opening a connection if needed
1826                         $masterConn = $this->getAnyOpenConnection( $this->getWriterIndex() );
1827                         if ( $masterConn ) {
1828                                 $pos = $masterConn->getMasterPos();
1829                         } else {
1830                                 $masterConn = $this->openConnection( $this->getWriterIndex(), self::DOMAIN_ANY );
1831                                 $pos = $masterConn->getMasterPos();
1832                                 $this->closeConnection( $masterConn );
1833                         }
1834                 }
1835
1836                 if ( $pos instanceof DBMasterPos ) {
1837                         $result = $conn->masterPosWait( $pos, $timeout );
1838                         if ( $result == -1 || is_null( $result ) ) {
1839                                 $msg = __METHOD__ . ': timed out waiting on {host} pos {pos}';
1840                                 $this->replLogger->warning( $msg, [
1841                                         'host' => $conn->getServer(),
1842                                         'pos' => $pos,
1843                                         'trace' => ( new RuntimeException() )->getTraceAsString()
1844                                 ] );
1845                                 $ok = false;
1846                         } else {
1847                                 $this->replLogger->debug( __METHOD__ . ': done waiting' );
1848                                 $ok = true;
1849                         }
1850                 } else {
1851                         $ok = false; // something is misconfigured
1852                         $this->replLogger->error(
1853                                 __METHOD__ . ': could not get master pos for {host}',
1854                                 [
1855                                         'host' => $conn->getServer(),
1856                                         'trace' => ( new RuntimeException() )->getTraceAsString()
1857                                 ]
1858                         );
1859                 }
1860
1861                 return $ok;
1862         }
1863
1864         public function setTransactionListener( $name, callable $callback = null ) {
1865                 if ( $callback ) {
1866                         $this->trxRecurringCallbacks[$name] = $callback;
1867                 } else {
1868                         unset( $this->trxRecurringCallbacks[$name] );
1869                 }
1870                 $this->forEachOpenMasterConnection(
1871                         function ( IDatabase $conn ) use ( $name, $callback ) {
1872                                 $conn->setTransactionListener( $name, $callback );
1873                         }
1874                 );
1875         }
1876
1877         public function setTableAliases( array $aliases ) {
1878                 $this->tableAliases = $aliases;
1879         }
1880
1881         public function setIndexAliases( array $aliases ) {
1882                 $this->indexAliases = $aliases;
1883         }
1884
1885         public function setDomainPrefix( $prefix ) {
1886                 // Find connections to explicit foreign domains still marked as in-use...
1887                 $domainsInUse = [];
1888                 $this->forEachOpenConnection( function ( IDatabase $conn ) use ( &$domainsInUse ) {
1889                         // Once reuseConnection() is called on a handle, its reference count goes from 1 to 0.
1890                         // Until then, it is still in use by the caller (explicitly or via DBConnRef scope).
1891                         if ( $conn->getLBInfo( 'foreignPoolRefCount' ) > 0 ) {
1892                                 $domainsInUse[] = $conn->getDomainID();
1893                         }
1894                 } );
1895
1896                 // Do not switch connections to explicit foreign domains unless marked as safe
1897                 if ( $domainsInUse ) {
1898                         $domains = implode( ', ', $domainsInUse );
1899                         throw new DBUnexpectedError( null,
1900                                 "Foreign domain connections are still in use ($domains)." );
1901                 }
1902
1903                 $oldDomain = $this->localDomain->getId();
1904                 $this->setLocalDomain( new DatabaseDomain(
1905                         $this->localDomain->getDatabase(),
1906                         $this->localDomain->getSchema(),
1907                         $prefix
1908                 ) );
1909
1910                 $this->forEachOpenConnection( function ( IDatabase $db ) use ( $prefix, $oldDomain ) {
1911                         if ( !$db->getLBInfo( 'foreign' ) ) {
1912                                 $db->tablePrefix( $prefix );
1913                         }
1914                 } );
1915         }
1916
1917         /**
1918          * @param DatabaseDomain $domain
1919          */
1920         private function setLocalDomain( DatabaseDomain $domain ) {
1921                 $this->localDomain = $domain;
1922                 // In case a caller assumes that the domain ID is simply <db>-<prefix>, which is almost
1923                 // always true, gracefully handle the case when they fail to account for escaping.
1924                 if ( $this->localDomain->getTablePrefix() != '' ) {
1925                         $this->localDomainIdAlias =
1926                                 $this->localDomain->getDatabase() . '-' . $this->localDomain->getTablePrefix();
1927                 } else {
1928                         $this->localDomainIdAlias = $this->localDomain->getDatabase();
1929                 }
1930         }
1931
1932         /**
1933          * Make PHP ignore user aborts/disconnects until the returned
1934          * value leaves scope. This returns null and does nothing in CLI mode.
1935          *
1936          * @return ScopedCallback|null
1937          */
1938         final protected function getScopedPHPBehaviorForCommit() {
1939                 if ( PHP_SAPI != 'cli' ) { // https://bugs.php.net/bug.php?id=47540
1940                         $old = ignore_user_abort( true ); // avoid half-finished operations
1941                         return new ScopedCallback( function () use ( $old ) {
1942                                 ignore_user_abort( $old );
1943                         } );
1944                 }
1945
1946                 return null;
1947         }
1948
1949         function __destruct() {
1950                 // Avoid connection leaks for sanity
1951                 $this->disable();
1952         }
1953 }
1954
1955 /**
1956  * @deprecated since 1.29
1957  */
1958 class_alias( LoadBalancer::class, 'LoadBalancer' );