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 ILoadMonitor */
  42         private $loadMonitor;
  43         /** @var callable|null Callback to run before the first connection attempt */
  44         private $chronologyCallback;
  45         /** @var BagOStuff */
  46         private $srvCache;
  47         /** @var WANObjectCache */
  48         private $wanCache;
  49         /** @var object|string Class name or object With profileIn/profileOut methods */
  50         private $profiler;
  51         /** @var TransactionProfiler */
  52         private $trxProfiler;
  53         /** @var LoggerInterface */
  54         private $replLogger;
  55         /** @var LoggerInterface */
  56         private $connLogger;
  57         /** @var LoggerInterface */
  58         private $queryLogger;
  59         /** @var LoggerInterface */
  60         private $perfLogger;
  61         /** @var callable Exception logger */
  62         private $errorLogger;
  63         /** @var callable Deprecation logger */
  64         private $deprecationLogger;
  65
  66         /** @var DatabaseDomain Local Domain ID and default for selectDB() calls */
  67         private $localDomain;
  68
  69         /** @var Database[][][] Map of (connection category => server index => IDatabase[]) */
  70         private $conns;
  71
  72         /** @var array[] Map of (server index => server config array) */
  73         private $servers;
  74         /** @var float[] Map of (server index => weight) */
  75         private $loads;
  76         /** @var array[] Map of (group => server index => weight) */
  77         private $groupLoads;
  78         /** @var bool Whether to disregard replica DB lag as a factor in replica DB selection */
  79         private $allowLagged;
  80         /** @var int Seconds to spend waiting on replica DB lag to resolve */
  81         private $waitTimeout;
  82         /** @var array The LoadMonitor configuration */
  83         private $loadMonitorConfig;
  84         /** @var string Alternate ID string for the domain instead of DatabaseDomain::getId() */
  85         private $localDomainIdAlias;
  86         /** @var int */
  87         private $maxLag = self::MAX_LAG_DEFAULT;
  88
  89         /** @var string Current server name */
  90         private $hostname;
  91         /** @var bool Whether this PHP instance is for a CLI script */
  92         private $cliMode;
  93         /** @var string Agent name for query profiling */
  94         private $agent;
  95
  96         /** @var array[] $aliases Map of (table => (dbname, schema, prefix) map) */
  97         private $tableAliases = [];
  98         /** @var string[] Map of (index alias => index) */
  99         private $indexAliases = [];
 100         /** @var array[] Map of (name => callable) */
 101         private $trxRecurringCallbacks = [];
 102
 103         /** @var Database DB connection object that caused a problem */
 104         private $errorConnection;
 105         /** @var int The generic (not query grouped) replica DB index (of $mServers) */
 106         private $readIndex;
 107         /** @var bool|DBMasterPos False if not set */
 108         private $waitForPos;
 109         /** @var bool Whether the generic reader fell back to a lagged replica DB */
 110         private $laggedReplicaMode = false;
 111         /** @var bool Whether the generic reader fell back to a lagged replica DB */
 112         private $allReplicasDownMode = false;
 113         /** @var string The last DB selection or connection error */
 114         private $lastError = 'Unknown error';
 115         /** @var string|bool Reason the LB is read-only or false if not */
 116         private $readOnlyReason = false;
 117         /** @var int Total connections opened */
 118         private $connsOpened = 0;
 119         /** @var bool */
 120         private $disabled = false;
 121         /** @var bool Whether any connection has been attempted yet */
 122         private $connectionAttempted = false;
 123
 124         /** @var string|bool String if a requested DBO_TRX transaction round is active */
 125         private $trxRoundId = false;
 126         /** @var string Stage of the current transaction round in the transaction round life-cycle */
 127         private $trxRoundStage = self::ROUND_CURSORY;
 128
 129         /** @var string|null */
 130         private $defaultGroup = null;
 131
 132         /** @var int Warn when this many connection are held */
 133         const CONN_HELD_WARN_THRESHOLD = 10;
 134
 135         /** @var int Default 'maxLag' when unspecified */
 136         const MAX_LAG_DEFAULT = 10;
 137         /** @var int Default 'waitTimeout' when unspecified */
 138         const MAX_WAIT_DEFAULT = 10;
 139         /** @var int Seconds to cache master server read-only status */
 140         const TTL_CACHE_READONLY = 5;
 141
 142         const KEY_LOCAL = 'local';
 143         const KEY_FOREIGN_FREE = 'foreignFree';
 144         const KEY_FOREIGN_INUSE = 'foreignInUse';
 145
 146         const KEY_LOCAL_NOROUND = 'localAutoCommit';
 147         const KEY_FOREIGN_FREE_NOROUND = 'foreignFreeAutoCommit';
 148         const KEY_FOREIGN_INUSE_NOROUND = 'foreignInUseAutoCommit';
 149
 150         /** @var string Transaction round, explicit or implicit, has not finished writing */
 151         const ROUND_CURSORY = 'cursory';
 152         /** @var string Transaction round writes are complete and ready for pre-commit checks */
 153         const ROUND_FINALIZED = 'finalized';
 154         /** @var string Transaction round passed final pre-commit checks */
 155         const ROUND_APPROVED = 'approved';
 156         /** @var string Transaction round was committed and post-commit callbacks must be run */
 157         const ROUND_COMMIT_CALLBACKS = 'commit-callbacks';
 158         /** @var string Transaction round was rolled back and post-rollback callbacks must be run */
 159         const ROUND_ROLLBACK_CALLBACKS = 'rollback-callbacks';
 160         /** @var string Transaction round encountered an error */
 161         const ROUND_ERROR = 'error';
 162
 163         public function __construct( array $params ) {
 164                 if ( !isset( $params['servers'] ) ) {
 165                         throw new InvalidArgumentException( __CLASS__ . ': missing servers parameter' );
 166                 }
 167                 $this->servers = $params['servers'];
 168                 foreach ( $this->servers as $i => $server ) {
 169                         if ( $i == 0 ) {
 170                                 $this->servers[$i]['master'] = true;
 171                         } else {
 172                                 $this->servers[$i]['replica'] = true;
 173                         }
 174                 }
 175
 176                 $localDomain = isset( $params['localDomain'] )
 177                         ? DatabaseDomain::newFromId( $params['localDomain'] )
 178                         : DatabaseDomain::newUnspecified();
 179                 $this->setLocalDomain( $localDomain );
 180
 181                 $this->waitTimeout = $params['waitTimeout'] ?? self::MAX_WAIT_DEFAULT;
 182
 183                 $this->readIndex = -1;
 184                 $this->conns = [
 185                         // Connection were transaction rounds may be applied
 186                         self::KEY_LOCAL => [],
 187                         self::KEY_FOREIGN_INUSE => [],
 188                         self::KEY_FOREIGN_FREE => [],
 189                         // Auto-committing counterpart connections that ignore transaction rounds
 190                         self::KEY_LOCAL_NOROUND => [],
 191                         self::KEY_FOREIGN_INUSE_NOROUND => [],
 192                         self::KEY_FOREIGN_FREE_NOROUND => []
 193                 ];
 194                 $this->loads = [];
 195                 $this->waitForPos = false;
 196                 $this->allowLagged = false;
 197
 198                 if ( isset( $params['readOnlyReason'] ) && is_string( $params['readOnlyReason'] ) ) {
 199                         $this->readOnlyReason = $params['readOnlyReason'];
 200                 }
 201
 202                 if ( isset( $params['maxLag'] ) ) {
 203                         $this->maxLag = $params['maxLag'];
 204                 }
 205
 206                 if ( isset( $params['loadMonitor'] ) ) {
 207                         $this->loadMonitorConfig = $params['loadMonitor'];
 208                 } else {
 209                         $this->loadMonitorConfig = [ 'class' => 'LoadMonitorNull' ];
 210                 }
 211                 $this->loadMonitorConfig += [ 'lagWarnThreshold' => $this->maxLag ];
 212
 213                 foreach ( $params['servers'] as $i => $server ) {
 214                         $this->loads[$i] = $server['load'];
 215                         if ( isset( $server['groupLoads'] ) ) {
 216                                 foreach ( $server['groupLoads'] as $group => $ratio ) {
 217                                         if ( !isset( $this->groupLoads[$group] ) ) {
 218                                                 $this->groupLoads[$group] = [];
 219                                         }
 220                                         $this->groupLoads[$group][$i] = $ratio;
 221                                 }
 222                         }
 223                 }
 224
 225                 if ( isset( $params['srvCache'] ) ) {
 226                         $this->srvCache = $params['srvCache'];
 227                 } else {
 228                         $this->srvCache = new EmptyBagOStuff();
 229                 }
 230                 if ( isset( $params['wanCache'] ) ) {
 231                         $this->wanCache = $params['wanCache'];
 232                 } else {
 233                         $this->wanCache = WANObjectCache::newEmpty();
 234                 }
 235                 $this->profiler = $params['profiler'] ?? null;
 236                 if ( isset( $params['trxProfiler'] ) ) {
 237                         $this->trxProfiler = $params['trxProfiler'];
 238                 } else {
 239                         $this->trxProfiler = new TransactionProfiler();
 240                 }
 241
 242                 $this->errorLogger = $params['errorLogger'] ?? function ( Exception $e ) {
 243                         trigger_error( get_class( $e ) . ': ' . $e->getMessage(), E_USER_WARNING );
 244                 };
 245                 $this->deprecationLogger = $params['deprecationLogger'] ?? function ( $msg ) {
 246                         trigger_error( $msg, E_USER_DEPRECATED );
 247                 };
 248
 249                 foreach ( [ 'replLogger', 'connLogger', 'queryLogger', 'perfLogger' ] as $key ) {
 250                         $this->$key = $params[$key] ?? new NullLogger();
 251                 }
 252
 253                 $this->hostname = $params['hostname'] ?? ( gethostname() ?: 'unknown' );
 254                 $this->cliMode = $params['cliMode'] ?? ( PHP_SAPI === 'cli' || PHP_SAPI === 'phpdbg' );
 255                 $this->agent = $params['agent'] ?? '';
 256
 257                 if ( isset( $params['chronologyCallback'] ) ) {
 258                         $this->chronologyCallback = $params['chronologyCallback'];
 259                 }
 260
 261                 if ( isset( $params['roundStage'] ) ) {
 262                         if ( $params['roundStage'] === self::STAGE_POSTCOMMIT_CALLBACKS ) {
 263                                 $this->trxRoundStage = self::ROUND_COMMIT_CALLBACKS;
 264                         } elseif ( $params['roundStage'] === self::STAGE_POSTROLLBACK_CALLBACKS ) {
 265                                 $this->trxRoundStage = self::ROUND_ROLLBACK_CALLBACKS;
 266                         }
 267                 }
 268
 269                 $this->defaultGroup = $params['defaultGroup'] ?? null;
 270         }
 271
 272         /**
 273          * Get the local (and default) database domain ID of connection handles
 274          *
 275          * @see DatabaseDomain
 276          * @return string Database domain ID; this specifies DB name, schema, and table prefix
 277          * @since 1.31
 278          */
 279         public function getLocalDomainID() {
 280                 return $this->localDomain->getId();
 281         }
 282
 283         /**
 284          * Get a LoadMonitor instance
 285          *
 286          * @return ILoadMonitor
 287          */
 288         private function getLoadMonitor() {
 289                 if ( !isset( $this->loadMonitor ) ) {
 290                         $compat = [
 291                                 'LoadMonitor' => LoadMonitor::class,
 292                                 'LoadMonitorNull' => LoadMonitorNull::class,
 293                                 'LoadMonitorMySQL' => LoadMonitorMySQL::class,
 294                         ];
 295
 296                         $class = $this->loadMonitorConfig['class'];
 297                         if ( isset( $compat[$class] ) ) {
 298                                 $class = $compat[$class];
 299                         }
 300
 301                         $this->loadMonitor = new $class(
 302                                 $this, $this->srvCache, $this->wanCache, $this->loadMonitorConfig );
 303                         $this->loadMonitor->setLogger( $this->replLogger );
 304                 }
 305
 306                 return $this->loadMonitor;
 307         }
 308
 309         /**
 310          * @param array $loads
 311          * @param bool|string $domain Domain to get non-lagged for
 312          * @param int $maxLag Restrict the maximum allowed lag to this many seconds
 313          * @return bool|int|string
 314          */
 315         private function getRandomNonLagged( array $loads, $domain = false, $maxLag = INF ) {
 316                 $lags = $this->getLagTimes( $domain );
 317
 318                 # Unset excessively lagged servers
 319                 foreach ( $lags as $i => $lag ) {
 320                         if ( $i != 0 ) {
 321                                 # How much lag this server nominally is allowed to have
 322                                 $maxServerLag = $this->servers[$i]['max lag'] ?? $this->maxLag; // default
 323                                 # Constrain that futher by $maxLag argument
 324                                 $maxServerLag = min( $maxServerLag, $maxLag );
 325
 326                                 $host = $this->getServerName( $i );
 327                                 if ( $lag === false && !is_infinite( $maxServerLag ) ) {
 328                                         $this->replLogger->error(
 329                                                 __METHOD__ .
 330                                                 ": server {host} is not replicating?", [ 'host' => $host ] );
 331                                         unset( $loads[$i] );
 332                                 } elseif ( $lag > $maxServerLag ) {
 333                                         $this->replLogger->info(
 334                                                 __METHOD__ .
 335                                                 ": server {host} has {lag} seconds of lag (>= {maxlag})",
 336                                                 [ 'host' => $host, 'lag' => $lag, 'maxlag' => $maxServerLag ]
 337                                         );
 338                                         unset( $loads[$i] );
 339                                 }
 340                         }
 341                 }
 342
 343                 # Find out if all the replica DBs with non-zero load are lagged
 344                 $sum = 0;
 345                 foreach ( $loads as $load ) {
 346                         $sum += $load;
 347                 }
 348                 if ( $sum == 0 ) {
 349                         # No appropriate DB servers except maybe the master and some replica DBs with zero load
 350                         # Do NOT use the master
 351                         # Instead, this function will return false, triggering read-only mode,
 352                         # and a lagged replica DB will be used instead.
 353                         return false;
 354                 }
 355
 356                 if ( count( $loads ) == 0 ) {
 357                         return false;
 358                 }
 359
 360                 # Return a random representative of the remainder
 361                 return ArrayUtils::pickRandom( $loads );
 362         }
 363
 364         public function getReaderIndex( $group = false, $domain = false ) {
 365                 if ( count( $this->servers ) == 1 ) {
 366                         // Skip the load balancing if there's only one server
 367                         return $this->getWriterIndex();
 368                 } elseif ( $group === false && $this->readIndex >= 0 ) {
 369                         // Shortcut if the generic reader index was already cached
 370                         return $this->readIndex;
 371                 }
 372
 373                 if ( $group !== false ) {
 374                         // Use the server weight array for this load group
 375                         if ( isset( $this->groupLoads[$group] ) ) {
 376                                 $loads = $this->groupLoads[$group];
 377                         } else {
 378                                 // No loads for this group, return false and the caller can use some other group
 379                                 $this->connLogger->info( __METHOD__ . ": no loads for group $group" );
 380
 381                                 return false;
 382                         }
 383                 } else {
 384                         // Use the generic load group
 385                         $loads = $this->loads;
 386                 }
 387
 388                 // Scale the configured load ratios according to each server's load and state
 389                 $this->getLoadMonitor()->scaleLoads( $loads, $domain );
 390
 391                 // Pick a server to use, accounting for weights, load, lag, and "waitForPos"
 392                 list( $i, $laggedReplicaMode ) = $this->pickReaderIndex( $loads, $domain );
 393                 if ( $i === false ) {
 394                         // Replica DB connection unsuccessful
 395                         return false;
 396                 }
 397
 398                 if ( $this->waitForPos && $i != $this->getWriterIndex() ) {
 399                         // Before any data queries are run, wait for the server to catch up to the
 400                         // specified position. This is used to improve session consistency. Note that
 401                         // when LoadBalancer::waitFor() sets "waitForPos", the waiting triggers here,
 402                         // so update laggedReplicaMode as needed for consistency.
 403                         if ( !$this->doWait( $i ) ) {
 404                                 $laggedReplicaMode = true;
 405                         }
 406                 }
 407
 408                 if ( $this->readIndex <= 0 && $this->loads[$i] > 0 && $group === false ) {
 409                         // Cache the generic reader index for future ungrouped DB_REPLICA handles
 410                         $this->readIndex = $i;
 411                         // Record if the generic reader index is in "lagged replica DB" mode
 412                         if ( $laggedReplicaMode ) {
 413                                 $this->laggedReplicaMode = true;
 414                         }
 415                 }
 416
 417                 $serverName = $this->getServerName( $i );
 418                 $this->connLogger->debug( __METHOD__ . ": using server $serverName for group '$group'" );
 419
 420                 return $i;
 421         }
 422
 423         /**
 424          * @param array $loads List of server weights
 425          * @param string|bool $domain
 426          * @return array (reader index, lagged replica mode) or false on failure
 427          */
 428         private function pickReaderIndex( array $loads, $domain = false ) {
 429                 if ( !count( $loads ) ) {
 430                         throw new InvalidArgumentException( "Empty server array given to LoadBalancer" );
 431                 }
 432
 433                 /** @var int|bool $i Index of selected server */
 434                 $i = false;
 435                 /** @var bool $laggedReplicaMode Whether server is considered lagged */
 436                 $laggedReplicaMode = false;
 437
 438                 // Quickly look through the available servers for a server that meets criteria...
 439                 $currentLoads = $loads;
 440                 while ( count( $currentLoads ) ) {
 441                         if ( $this->allowLagged || $laggedReplicaMode ) {
 442                                 $i = ArrayUtils::pickRandom( $currentLoads );
 443                         } else {
 444                                 $i = false;
 445                                 if ( $this->waitForPos && $this->waitForPos->asOfTime() ) {
 446                                         // "chronologyCallback" sets "waitForPos" for session consistency.
 447                                         // This triggers doWait() after connect, so it's especially good to
 448                                         // avoid lagged servers so as to avoid excessive delay in that method.
 449                                         $ago = microtime( true ) - $this->waitForPos->asOfTime();
 450                                         // Aim for <= 1 second of waiting (being too picky can backfire)
 451                                         $i = $this->getRandomNonLagged( $currentLoads, $domain, $ago + 1 );
 452                                 }
 453                                 if ( $i === false ) {
 454                                         // Any server with less lag than it's 'max lag' param is preferable
 455                                         $i = $this->getRandomNonLagged( $currentLoads, $domain );
 456                                 }
 457                                 if ( $i === false && count( $currentLoads ) != 0 ) {
 458                                         // All replica DBs lagged. Switch to read-only mode
 459                                         $this->replLogger->error(
 460                                                 __METHOD__ . ": all replica DBs lagged. Switch to read-only mode" );
 461                                         $i = ArrayUtils::pickRandom( $currentLoads );
 462                                         $laggedReplicaMode = true;
 463                                 }
 464                         }
 465
 466                         if ( $i === false ) {
 467                                 // pickRandom() returned false.
 468                                 // This is permanent and means the configuration or the load monitor
 469                                 // wants us to return false.
 470                                 $this->connLogger->debug( __METHOD__ . ": pickRandom() returned false" );
 471
 472                                 return [ false, false ];
 473                         }
 474
 475                         $serverName = $this->getServerName( $i );
 476                         $this->connLogger->debug( __METHOD__ . ": Using reader #$i: $serverName..." );
 477
 478                         $conn = $this->openConnection( $i, $domain );
 479                         if ( !$conn ) {
 480                                 $this->connLogger->warning( __METHOD__ . ": Failed connecting to $i/$domain" );
 481                                 unset( $currentLoads[$i] ); // avoid this server next iteration
 482                                 $i = false;
 483                                 continue;
 484                         }
 485
 486                         // Decrement reference counter, we are finished with this connection.
 487                         // It will be incremented for the caller later.
 488                         if ( $domain !== false ) {
 489                                 $this->reuseConnection( $conn );
 490                         }
 491
 492                         // Return this server
 493                         break;
 494                 }
 495
 496                 // If all servers were down, quit now
 497                 if ( !count( $currentLoads ) ) {
 498                         $this->connLogger->error( __METHOD__ . ": all servers down" );
 499                 }
 500
 501                 return [ $i, $laggedReplicaMode ];
 502         }
 503
 504         public function waitFor( $pos ) {
 505                 $oldPos = $this->waitForPos;
 506                 try {
 507                         $this->waitForPos = $pos;
 508                         // If a generic reader connection was already established, then wait now
 509                         $i = $this->readIndex;
 510                         if ( $i > 0 ) {
 511                                 if ( !$this->doWait( $i ) ) {
 512                                         $this->laggedReplicaMode = true;
 513                                 }
 514                         }
 515                 } finally {
 516                         // Restore the older position if it was higher since this is used for lag-protection
 517                         $this->setWaitForPositionIfHigher( $oldPos );
 518                 }
 519         }
 520
 521         public function waitForOne( $pos, $timeout = null ) {
 522                 $oldPos = $this->waitForPos;
 523                 try {
 524                         $this->waitForPos = $pos;
 525
 526                         $i = $this->readIndex;
 527                         if ( $i <= 0 ) {
 528                                 // Pick a generic replica DB if there isn't one yet
 529                                 $readLoads = $this->loads;
 530                                 unset( $readLoads[$this->getWriterIndex()] ); // replica DBs only
 531                                 $readLoads = array_filter( $readLoads ); // with non-zero load
 532                                 $i = ArrayUtils::pickRandom( $readLoads );
 533                         }
 534
 535                         if ( $i > 0 ) {
 536                                 $ok = $this->doWait( $i, true, $timeout );
 537                         } else {
 538                                 $ok = true; // no applicable loads
 539                         }
 540                 } finally {
 541                         # Restore the old position, as this is not used for lag-protection but for throttling
 542                         $this->waitForPos = $oldPos;
 543                 }
 544
 545                 return $ok;
 546         }
 547
 548         public function waitForAll( $pos, $timeout = null ) {
 549                 $timeout = $timeout ?: $this->waitTimeout;
 550
 551                 $oldPos = $this->waitForPos;
 552                 try {
 553                         $this->waitForPos = $pos;
 554                         $serverCount = count( $this->servers );
 555
 556                         $ok = true;
 557                         for ( $i = 1; $i < $serverCount; $i++ ) {
 558                                 if ( $this->loads[$i] > 0 ) {
 559                                         $start = microtime( true );
 560                                         $ok = $this->doWait( $i, true, $timeout ) && $ok;
 561                                         $timeout -= intval( microtime( true ) - $start );
 562                                         if ( $timeout <= 0 ) {
 563                                                 break; // timeout reached
 564                                         }
 565                                 }
 566                         }
 567                 } finally {
 568                         # Restore the old position, as this is not used for lag-protection but for throttling
 569                         $this->waitForPos = $oldPos;
 570                 }
 571
 572                 return $ok;
 573         }
 574
 575         /**
 576          * @param DBMasterPos|bool $pos
 577          */
 578         private function setWaitForPositionIfHigher( $pos ) {
 579                 if ( !$pos ) {
 580                         return;
 581                 }
 582
 583                 if ( !$this->waitForPos || $pos->hasReached( $this->waitForPos ) ) {
 584                         $this->waitForPos = $pos;
 585                 }
 586         }
 587
 588         public function getAnyOpenConnection( $i, $flags = 0 ) {
 589                 $autocommit = ( ( $flags & self::CONN_TRX_AUTOCOMMIT ) == self::CONN_TRX_AUTOCOMMIT );
 590                 foreach ( $this->conns as $connsByServer ) {
 591                         if ( !isset( $connsByServer[$i] ) ) {
 592                                 continue;
 593                         }
 594
 595                         foreach ( $connsByServer[$i] as $conn ) {
 596                                 if ( !$autocommit || $conn->getLBInfo( 'autoCommitOnly' ) ) {
 597                                         return $conn;
 598                                 }
 599                         }
 600                 }
 601
 602                 return false;
 603         }
 604
 605         /**
 606          * Wait for a given replica DB to catch up to the master pos stored in $this
 607          * @param int $index Server index
 608          * @param bool $open Check the server even if a new connection has to be made
 609          * @param int $timeout Max seconds to wait; default is "waitTimeout" given to __construct()
 610          * @return bool
 611          */
 612         protected function doWait( $index, $open = false, $timeout = null ) {
 613                 $timeout = max( 1, intval( $timeout ?: $this->waitTimeout ) );
 614
 615                 // Check if we already know that the DB has reached this point
 616                 $server = $this->getServerName( $index );
 617                 $key = $this->srvCache->makeGlobalKey( __CLASS__, 'last-known-pos', $server, 'v1' );
 618                 /** @var DBMasterPos $knownReachedPos */
 619                 $knownReachedPos = $this->srvCache->get( $key );
 620                 if (
 621                         $knownReachedPos instanceof DBMasterPos &&
 622                         $knownReachedPos->hasReached( $this->waitForPos )
 623                 ) {
 624                         $this->replLogger->debug(
 625                                 __METHOD__ .
 626                                 ': replica DB {dbserver} known to be caught up (pos >= $knownReachedPos).',
 627                                 [ 'dbserver' => $server ]
 628                         );
 629                         return true;
 630                 }
 631
 632                 // Find a connection to wait on, creating one if needed and allowed
 633                 $close = false; // close the connection afterwards
 634                 $conn = $this->getAnyOpenConnection( $index );
 635                 if ( !$conn ) {
 636                         if ( !$open ) {
 637                                 $this->replLogger->debug(
 638                                         __METHOD__ . ': no connection open for {dbserver}',
 639                                         [ 'dbserver' => $server ]
 640                                 );
 641
 642                                 return false;
 643                         } else {
 644                                 $conn = $this->openConnection( $index, self::DOMAIN_ANY );
 645                                 if ( !$conn ) {
 646                                         $this->replLogger->warning(
 647                                                 __METHOD__ . ': failed to connect to {dbserver}',
 648                                                 [ 'dbserver' => $server ]
 649                                         );
 650
 651                                         return false;
 652                                 }
 653                                 // Avoid connection spam in waitForAll() when connections
 654                                 // are made just for the sake of doing this lag check.
 655                                 $close = true;
 656                         }
 657                 }
 658
 659                 $this->replLogger->info(
 660                         __METHOD__ .
 661                         ': waiting for replica DB {dbserver} to catch up...',
 662                         [ 'dbserver' => $server ]
 663                 );
 664
 665                 $result = $conn->masterPosWait( $this->waitForPos, $timeout );
 666
 667                 if ( $result === null ) {
 668                         $this->replLogger->warning(
 669                                 __METHOD__ . ': Errored out waiting on {host} pos {pos}',
 670                                 [
 671                                         'host' => $server,
 672                                         'pos' => $this->waitForPos,
 673                                         'trace' => ( new RuntimeException() )->getTraceAsString()
 674                                 ]
 675                         );
 676                         $ok = false;
 677                 } elseif ( $result == -1 ) {
 678                         $this->replLogger->warning(
 679                                 __METHOD__ . ': Timed out waiting on {host} pos {pos}',
 680                                 [
 681                                         'host' => $server,
 682                                         'pos' => $this->waitForPos,
 683                                         'trace' => ( new RuntimeException() )->getTraceAsString()
 684                                 ]
 685                         );
 686                         $ok = false;
 687                 } else {
 688                         $this->replLogger->debug( __METHOD__ . ": done waiting" );
 689                         $ok = true;
 690                         // Remember that the DB reached this point
 691                         $this->srvCache->set( $key, $this->waitForPos, BagOStuff::TTL_DAY );
 692                 }
 693
 694                 if ( $close ) {
 695                         $this->closeConnection( $conn );
 696                 }
 697
 698                 return $ok;
 699         }
 700
 701         public function getConnection( $i, $groups = [], $domain = false, $flags = 0 ) {
 702                 if ( $i === null || $i === false ) {
 703                         throw new InvalidArgumentException( 'Attempt to call ' . __METHOD__ .
 704                                 ' with invalid server index' );
 705                 }
 706
 707                 if ( $this->localDomain->equals( $domain ) || $domain === $this->localDomainIdAlias ) {
 708                         $domain = false; // local connection requested
 709                 }
 710
 711                 if ( ( $flags & self::CONN_TRX_AUTOCOMMIT ) === self::CONN_TRX_AUTOCOMMIT ) {
 712                         // Assuming all servers are of the same type (or similar), which is overwhelmingly
 713                         // the case, use the master server information to get the attributes. The information
 714                         // for $i cannot be used since it might be DB_REPLICA, which might require connection
 715                         // attempts in order to be resolved into a real server index.
 716                         $attributes = $this->getServerAttributes( $this->getWriterIndex() );
 717                         if ( $attributes[Database::ATTR_DB_LEVEL_LOCKING] ) {
 718                                 // Callers sometimes want to (a) escape REPEATABLE-READ stateness without locking
 719                                 // rows (e.g. FOR UPDATE) or (b) make small commits during a larger transactions
 720                                 // to reduce lock contention. None of these apply for sqlite and using separate
 721                                 // connections just causes self-deadlocks.
 722                                 $flags &= ~self::CONN_TRX_AUTOCOMMIT;
 723                                 $this->connLogger->info( __METHOD__ .
 724                                         ': ignoring CONN_TRX_AUTOCOMMIT to avoid deadlocks.' );
 725                         }
 726                 }
 727
 728                 // Check one "group" per default: the generic pool
 729                 $defaultGroups = $this->defaultGroup ? [ $this->defaultGroup ] : [ false ];
 730
 731                 $groups = ( $groups === false || $groups === [] )
 732                         ? $defaultGroups
 733                         : (array)$groups;
 734
 735                 $masterOnly = ( $i == self::DB_MASTER || $i == $this->getWriterIndex() );
 736                 $oldConnsOpened = $this->connsOpened; // connections open now
 737
 738                 if ( $i == self::DB_MASTER ) {
 739                         $i = $this->getWriterIndex();
 740                 } elseif ( $i == self::DB_REPLICA ) {
 741                         # Try to find an available server in any the query groups (in order)
 742                         foreach ( $groups as $group ) {
 743                                 $groupIndex = $this->getReaderIndex( $group, $domain );
 744                                 if ( $groupIndex !== false ) {
 745                                         $i = $groupIndex;
 746                                         break;
 747                                 }
 748                         }
 749                 }
 750
 751                 # Operation-based index
 752                 if ( $i == self::DB_REPLICA ) {
 753                         $this->lastError = 'Unknown error'; // reset error string
 754                         # Try the general server pool if $groups are unavailable.
 755                         $i = ( $groups === [ false ] )
 756                                 ? false // don't bother with this if that is what was tried above
 757                                 : $this->getReaderIndex( false, $domain );
 758                         # Couldn't find a working server in getReaderIndex()?
 759                         if ( $i === false ) {
 760                                 $this->lastError = 'No working replica DB server: ' . $this->lastError;
 761                                 // Throw an exception
 762                                 $this->reportConnectionError();
 763                                 return null; // not reached
 764                         }
 765                 }
 766
 767                 # Now we have an explicit index into the servers array
 768                 $conn = $this->openConnection( $i, $domain, $flags );
 769                 if ( !$conn ) {
 770                         // Throw an exception
 771                         $this->reportConnectionError();
 772                         return null; // not reached
 773                 }
 774
 775                 # Profile any new connections that happen
 776                 if ( $this->connsOpened > $oldConnsOpened ) {
 777                         $host = $conn->getServer();
 778                         $dbname = $conn->getDBname();
 779                         $this->trxProfiler->recordConnection( $host, $dbname, $masterOnly );
 780                 }
 781
 782                 if ( $masterOnly ) {
 783                         # Make master-requested DB handles inherit any read-only mode setting
 784                         $conn->setLBInfo( 'readOnlyReason', $this->getReadOnlyReason( $domain, $conn ) );
 785                 }
 786
 787                 return $conn;
 788         }
 789
 790         public function reuseConnection( IDatabase $conn ) {
 791                 $serverIndex = $conn->getLBInfo( 'serverIndex' );
 792                 $refCount = $conn->getLBInfo( 'foreignPoolRefCount' );
 793                 if ( $serverIndex === null || $refCount === null ) {
 794                         /**
 795                          * This can happen in code like:
 796                          *   foreach ( $dbs as $db ) {
 797                          *     $conn = $lb->getConnection( $lb::DB_REPLICA, [], $db );
 798                          *     ...
 799                          *     $lb->reuseConnection( $conn );
 800                          *   }
 801                          * When a connection to the local DB is opened in this way, reuseConnection()
 802                          * should be ignored
 803                          */
 804                         return;
 805                 } elseif ( $conn instanceof DBConnRef ) {
 806                         // DBConnRef already handles calling reuseConnection() and only passes the live
 807                         // Database instance to this method. Any caller passing in a DBConnRef is broken.
 808                         $this->connLogger->error(
 809                                 __METHOD__ . ": got DBConnRef instance.\n" .
 810                                 ( new RuntimeException() )->getTraceAsString() );
 811
 812                         return;
 813                 }
 814
 815                 if ( $this->disabled ) {
 816                         return; // DBConnRef handle probably survived longer than the LoadBalancer
 817                 }
 818
 819                 if ( $conn->getLBInfo( 'autoCommitOnly' ) ) {
 820                         $connFreeKey = self::KEY_FOREIGN_FREE_NOROUND;
 821                         $connInUseKey = self::KEY_FOREIGN_INUSE_NOROUND;
 822                 } else {
 823                         $connFreeKey = self::KEY_FOREIGN_FREE;
 824                         $connInUseKey = self::KEY_FOREIGN_INUSE;
 825                 }
 826
 827                 $domain = $conn->getDomainID();
 828                 if ( !isset( $this->conns[$connInUseKey][$serverIndex][$domain] ) ) {
 829                         throw new InvalidArgumentException( __METHOD__ .
 830                                 ": connection $serverIndex/$domain not found; it may have already been freed." );
 831                 } elseif ( $this->conns[$connInUseKey][$serverIndex][$domain] !== $conn ) {
 832                         throw new InvalidArgumentException( __METHOD__ .
 833                                 ": connection $serverIndex/$domain mismatched; it may have already been freed." );
 834                 }
 835
 836                 $conn->setLBInfo( 'foreignPoolRefCount', --$refCount );
 837                 if ( $refCount <= 0 ) {
 838                         $this->conns[$connFreeKey][$serverIndex][$domain] = $conn;
 839                         unset( $this->conns[$connInUseKey][$serverIndex][$domain] );
 840                         if ( !$this->conns[$connInUseKey][$serverIndex] ) {
 841                                 unset( $this->conns[$connInUseKey][$serverIndex] ); // clean up
 842                         }
 843                         $this->connLogger->debug( __METHOD__ . ": freed connection $serverIndex/$domain" );
 844                 } else {
 845                         $this->connLogger->debug( __METHOD__ .
 846                                 ": reference count for $serverIndex/$domain reduced to $refCount" );
 847                 }
 848         }
 849
 850         public function getConnectionRef( $db, $groups = [], $domain = false, $flags = 0 ) {
 851                 $domain = ( $domain !== false ) ? $domain : $this->localDomain;
 852
 853                 return new DBConnRef( $this, $this->getConnection( $db, $groups, $domain, $flags ) );
 854         }
 855
 856         public function getLazyConnectionRef( $db, $groups = [], $domain = false, $flags = 0 ) {
 857                 $domain = ( $domain !== false ) ? $domain : $this->localDomain;
 858
 859                 return new DBConnRef( $this, [ $db, $groups, $domain, $flags ] );
 860         }
 861
 862         public function getMaintenanceConnectionRef( $db, $groups = [], $domain = false, $flags = 0 ) {
 863                 $domain = ( $domain !== false ) ? $domain : $this->localDomain;
 864
 865                 return new MaintainableDBConnRef(
 866                         $this, $this->getConnection( $db, $groups, $domain, $flags ) );
 867         }
 868
 869         public function openConnection( $i, $domain = false, $flags = 0 ) {
 870                 if ( $this->localDomain->equals( $domain ) || $domain === $this->localDomainIdAlias ) {
 871                         $domain = false; // local connection requested
 872                 }
 873
 874                 if ( !$this->connectionAttempted && $this->chronologyCallback ) {
 875                         $this->connLogger->debug( __METHOD__ . ': calling initLB() before first connection.' );
 876                         // Load any "waitFor" positions before connecting so that doWait() is triggered
 877                         $this->connectionAttempted = true;
 878                         ( $this->chronologyCallback )( $this );
 879                 }
 880
 881                 // Check if an auto-commit connection is being requested. If so, it will not reuse the
 882                 // main set of DB connections but rather its own pool since:
 883                 // a) those are usually set to implicitly use transaction rounds via DBO_TRX
 884                 // b) those must support the use of explicit transaction rounds via beginMasterChanges()
 885                 $autoCommit = ( ( $flags & self::CONN_TRX_AUTOCOMMIT ) == self::CONN_TRX_AUTOCOMMIT );
 886
 887                 if ( $domain !== false ) {
 888                         // Connection is to a foreign domain
 889                         $conn = $this->openForeignConnection( $i, $domain, $flags );
 890                 } else {
 891                         // Connection is to the local domain
 892                         $connKey = $autoCommit ? self::KEY_LOCAL_NOROUND : self::KEY_LOCAL;
 893                         if ( isset( $this->conns[$connKey][$i][0] ) ) {
 894                                 $conn = $this->conns[$connKey][$i][0];
 895                         } else {
 896                                 if ( !isset( $this->servers[$i] ) || !is_array( $this->servers[$i] ) ) {
 897                                         throw new InvalidArgumentException( "No server with index '$i'." );
 898                                 }
 899                                 // Open a new connection
 900                                 $server = $this->servers[$i];
 901                                 $server['serverIndex'] = $i;
 902                                 $server['autoCommitOnly'] = $autoCommit;
 903                                 if ( $this->localDomain->getDatabase() !== null ) {
 904                                         // Use the local domain table prefix if the local domain is specified
 905                                         $server['tablePrefix'] = $this->localDomain->getTablePrefix();
 906                                 }
 907                                 $conn = $this->reallyOpenConnection( $server, $this->localDomain );
 908                                 $host = $this->getServerName( $i );
 909                                 if ( $conn->isOpen() ) {
 910                                         $this->connLogger->debug(
 911                                                 __METHOD__ . ": connected to database $i at '$host'." );
 912                                         $this->conns[$connKey][$i][0] = $conn;
 913                                 } else {
 914                                         $this->connLogger->warning(
 915                                                 __METHOD__ . ": failed to connect to database $i at '$host'." );
 916                                         $this->errorConnection = $conn;
 917                                         $conn = false;
 918                                 }
 919                         }
 920                 }
 921
 922                 if ( $conn instanceof IDatabase && !$conn->isOpen() ) {
 923                         // Connection was made but later unrecoverably lost for some reason.
 924                         // Do not return a handle that will just throw exceptions on use,
 925                         // but let the calling code (e.g. getReaderIndex) try another server.
 926                         // See DatabaseMyslBase::ping() for how this can happen.
 927                         $this->errorConnection = $conn;
 928                         $conn = false;
 929                 }
 930
 931                 if ( $autoCommit && $conn instanceof IDatabase ) {
 932                         $conn->clearFlag( $conn::DBO_TRX ); // auto-commit mode
 933                 }
 934
 935                 return $conn;
 936         }
 937
 938         /**
 939          * Open a connection to a foreign DB, or return one if it is already open.
 940          *
 941          * Increments a reference count on the returned connection which locks the
 942          * connection to the requested domain. This reference count can be
 943          * decremented by calling reuseConnection().
 944          *
 945          * If a connection is open to the appropriate server already, but with the wrong
 946          * database, it will be switched to the right database and returned, as long as
 947          * it has been freed first with reuseConnection().
 948          *
 949          * On error, returns false, and the connection which caused the
 950          * error will be available via $this->errorConnection.
 951          *
 952          * @note If disable() was called on this LoadBalancer, this method will throw a DBAccessError.
 953          *
 954          * @param int $i Server index
 955          * @param string $domain Domain ID to open
 956          * @param int $flags Class CONN_* constant bitfield
 957          * @return Database
 958          */
 959         private function openForeignConnection( $i, $domain, $flags = 0 ) {
 960                 $domainInstance = DatabaseDomain::newFromId( $domain );
 961                 $dbName = $domainInstance->getDatabase();
 962                 $prefix = $domainInstance->getTablePrefix();
 963                 $autoCommit = ( ( $flags & self::CONN_TRX_AUTOCOMMIT ) == self::CONN_TRX_AUTOCOMMIT );
 964
 965                 if ( $autoCommit ) {
 966                         $connFreeKey = self::KEY_FOREIGN_FREE_NOROUND;
 967                         $connInUseKey = self::KEY_FOREIGN_INUSE_NOROUND;
 968                 } else {
 969                         $connFreeKey = self::KEY_FOREIGN_FREE;
 970                         $connInUseKey = self::KEY_FOREIGN_INUSE;
 971                 }
 972
 973                 if ( isset( $this->conns[$connInUseKey][$i][$domain] ) ) {
 974                         // Reuse an in-use connection for the same domain
 975                         $conn = $this->conns[$connInUseKey][$i][$domain];
 976                         $this->connLogger->debug( __METHOD__ . ": reusing connection $i/$domain" );
 977                 } elseif ( isset( $this->conns[$connFreeKey][$i][$domain] ) ) {
 978                         // Reuse a free connection for the same domain
 979                         $conn = $this->conns[$connFreeKey][$i][$domain];
 980                         unset( $this->conns[$connFreeKey][$i][$domain] );
 981                         $this->conns[$connInUseKey][$i][$domain] = $conn;
 982                         $this->connLogger->debug( __METHOD__ . ": reusing free connection $i/$domain" );
 983                 } elseif ( !empty( $this->conns[$connFreeKey][$i] ) ) {
 984                         // Reuse a free connection from another domain
 985                         $conn = reset( $this->conns[$connFreeKey][$i] );
 986                         $oldDomain = key( $this->conns[$connFreeKey][$i] );
 987                         if ( strlen( $dbName ) && !$conn->selectDB( $dbName ) ) {
 988                                 $this->lastError = "Error selecting database '$dbName' on server " .
 989                                         $conn->getServer() . " from client host {$this->hostname}";
 990                                 $this->errorConnection = $conn;
 991                                 $conn = false;
 992                         } else {
 993                                 $conn->tablePrefix( $prefix );
 994                                 unset( $this->conns[$connFreeKey][$i][$oldDomain] );
 995                                 // Note that if $domain is an empty string, getDomainID() might not match it
 996                                 $this->conns[$connInUseKey][$i][$conn->getDomainId()] = $conn;
 997                                 $this->connLogger->debug( __METHOD__ .
 998                                         ": reusing free connection from $oldDomain for $domain" );
 999                         }
1000                 } else {
1001                         if ( !isset( $this->servers[$i] ) || !is_array( $this->servers[$i] ) ) {
1002                                 throw new InvalidArgumentException( "No server with index '$i'." );
1003                         }
1004                         // Open a new connection
1005                         $server = $this->servers[$i];
1006                         $server['serverIndex'] = $i;
1007                         $server['foreignPoolRefCount'] = 0;
1008                         $server['foreign'] = true;
1009                         $server['autoCommitOnly'] = $autoCommit;
1010                         $conn = $this->reallyOpenConnection( $server, $domainInstance );
1011                         if ( !$conn->isOpen() ) {
1012                                 $this->connLogger->warning( __METHOD__ . ": connection error for $i/$domain" );
1013                                 $this->errorConnection = $conn;
1014                                 $conn = false;
1015                         } else {
1016                                 $conn->tablePrefix( $prefix ); // as specified
1017                                 // Note that if $domain is an empty string, getDomainID() might not match it
1018                                 $this->conns[$connInUseKey][$i][$conn->getDomainID()] = $conn;
1019                                 $this->connLogger->debug( __METHOD__ . ": opened new connection for $i/$domain" );
1020                         }
1021                 }
1022
1023                 // Increment reference count
1024                 if ( $conn instanceof IDatabase ) {
1025                         $refCount = $conn->getLBInfo( 'foreignPoolRefCount' );
1026                         $conn->setLBInfo( 'foreignPoolRefCount', $refCount + 1 );
1027                 }
1028
1029                 return $conn;
1030         }
1031
1032         public function getServerAttributes( $i ) {
1033                 return Database::attributesFromType(
1034                         $this->getServerType( $i ),
1035                         $this->servers[$i]['driver'] ?? null
1036                 );
1037         }
1038
1039         /**
1040          * Test if the specified index represents an open connection
1041          *
1042          * @param int $index Server index
1043          * @access private
1044          * @return bool
1045          */
1046         private function isOpen( $index ) {
1047                 if ( !is_int( $index ) ) {
1048                         return false;
1049                 }
1050
1051                 return (bool)$this->getAnyOpenConnection( $index );
1052         }
1053
1054         /**
1055          * Open a new network connection to a server (uncached)
1056          *
1057          * Returns a Database object whether or not the connection was successful.
1058          *
1059          * @param array $server
1060          * @param DatabaseDomain $domainOverride Use an unspecified domain to not select any database
1061          * @return Database
1062          * @throws DBAccessError
1063          * @throws InvalidArgumentException
1064          */
1065         protected function reallyOpenConnection( array $server, DatabaseDomain $domainOverride ) {
1066                 if ( $this->disabled ) {
1067                         throw new DBAccessError();
1068                 }
1069
1070                 // Handle $domainOverride being a specified or an unspecified domain
1071                 if ( $domainOverride->getDatabase() === null ) {
1072                         // Normally, an RDBMS requires a DB name specified on connection and the $server
1073                         // configuration array is assumed to already specify an appropriate DB name.
1074                         if ( $server['type'] === 'mysql' ) {
1075                                 // For MySQL, DATABASE and SCHEMA are synonyms, connections need not specify a DB,
1076                                 // and the DB name in $server might not exist due to legacy reasons (the default
1077                                 // domain used to ignore the local LB domain, even when mismatched).
1078                                 $server['dbname'] = null;
1079                         }
1080                 } else {
1081                         $server['dbname'] = $domainOverride->getDatabase();
1082                         $server['schema'] = $domainOverride->getSchema();
1083                 }
1084
1085                 // Let the handle know what the cluster master is (e.g. "db1052")
1086                 $masterName = $this->getServerName( $this->getWriterIndex() );
1087                 $server['clusterMasterHost'] = $masterName;
1088
1089                 // Log when many connection are made on requests
1090                 if ( ++$this->connsOpened >= self::CONN_HELD_WARN_THRESHOLD ) {
1091                         $this->perfLogger->warning( __METHOD__ . ": " .
1092                                 "{$this->connsOpened}+ connections made (master=$masterName)" );
1093                 }
1094
1095                 $server['srvCache'] = $this->srvCache;
1096                 // Set loggers and profilers
1097                 $server['connLogger'] = $this->connLogger;
1098                 $server['queryLogger'] = $this->queryLogger;
1099                 $server['errorLogger'] = $this->errorLogger;
1100                 $server['deprecationLogger'] = $this->deprecationLogger;
1101                 $server['profiler'] = $this->profiler;
1102                 $server['trxProfiler'] = $this->trxProfiler;
1103                 // Use the same agent and PHP mode for all DB handles
1104                 $server['cliMode'] = $this->cliMode;
1105                 $server['agent'] = $this->agent;
1106                 // Use DBO_DEFAULT flags by default for LoadBalancer managed databases. Assume that the
1107                 // application calls LoadBalancer::commitMasterChanges() before the PHP script completes.
1108                 $server['flags'] = $server['flags'] ?? IDatabase::DBO_DEFAULT;
1109
1110                 // Create a live connection object
1111                 try {
1112                         $db = Database::factory( $server['type'], $server );
1113                 } catch ( DBConnectionError $e ) {
1114                         // FIXME: This is probably the ugliest thing I have ever done to
1115                         // PHP. I'm half-expecting it to segfault, just out of disgust. -- TS
1116                         $db = $e->db;
1117                 }
1118
1119                 $db->setLBInfo( $server );
1120                 $db->setLazyMasterHandle(
1121                         $this->getLazyConnectionRef( self::DB_MASTER, [], $db->getDomainID() )
1122                 );
1123                 $db->setTableAliases( $this->tableAliases );
1124                 $db->setIndexAliases( $this->indexAliases );
1125
1126                 if ( $server['serverIndex'] === $this->getWriterIndex() ) {
1127                         if ( $this->trxRoundId !== false ) {
1128                                 $this->applyTransactionRoundFlags( $db );
1129                         }
1130                         foreach ( $this->trxRecurringCallbacks as $name => $callback ) {
1131                                 $db->setTransactionListener( $name, $callback );
1132                         }
1133                 }
1134
1135                 return $db;
1136         }
1137
1138         /**
1139          * @throws DBConnectionError
1140          */
1141         private function reportConnectionError() {
1142                 $conn = $this->errorConnection; // the connection which caused the error
1143                 $context = [
1144                         'method' => __METHOD__,
1145                         'last_error' => $this->lastError,
1146                 ];
1147
1148                 if ( $conn instanceof IDatabase ) {
1149                         $context['db_server'] = $conn->getServer();
1150                         $this->connLogger->warning(
1151                                 __METHOD__ . ": connection error: {last_error} ({db_server})",
1152                                 $context
1153                         );
1154
1155                         throw new DBConnectionError( $conn, "{$this->lastError} ({$context['db_server']})" );
1156                 } else {
1157                         // No last connection, probably due to all servers being too busy
1158                         $this->connLogger->error(
1159                                 __METHOD__ .
1160                                 ": LB failure with no last connection. Connection error: {last_error}",
1161                                 $context
1162                         );
1163
1164                         // If all servers were busy, "lastError" will contain something sensible
1165                         throw new DBConnectionError( null, $this->lastError );
1166                 }
1167         }
1168
1169         public function getWriterIndex() {
1170                 return 0;
1171         }
1172
1173         public function haveIndex( $i ) {
1174                 return array_key_exists( $i, $this->servers );
1175         }
1176
1177         public function isNonZeroLoad( $i ) {
1178                 return array_key_exists( $i, $this->servers ) && $this->loads[$i] != 0;
1179         }
1180
1181         public function getServerCount() {
1182                 return count( $this->servers );
1183         }
1184
1185         public function getServerName( $i ) {
1186                 if ( isset( $this->servers[$i]['hostName'] ) ) {
1187                         $name = $this->servers[$i]['hostName'];
1188                 } elseif ( isset( $this->servers[$i]['host'] ) ) {
1189                         $name = $this->servers[$i]['host'];
1190                 } else {
1191                         $name = '';
1192                 }
1193
1194                 return ( $name != '' ) ? $name : 'localhost';
1195         }
1196
1197         public function getServerInfo( $i ) {
1198                 if ( isset( $this->servers[$i] ) ) {
1199                         return $this->servers[$i];
1200                 } else {
1201                         return false;
1202                 }
1203         }
1204
1205         public function getServerType( $i ) {
1206                 return $this->servers[$i]['type'] ?? 'unknown';
1207         }
1208
1209         public function getMasterPos() {
1210                 # If this entire request was served from a replica DB without opening a connection to the
1211                 # master (however unlikely that may be), then we can fetch the position from the replica DB.
1212                 $masterConn = $this->getAnyOpenConnection( $this->getWriterIndex() );
1213                 if ( !$masterConn ) {
1214                         $serverCount = count( $this->servers );
1215                         for ( $i = 1; $i < $serverCount; $i++ ) {
1216                                 $conn = $this->getAnyOpenConnection( $i );
1217                                 if ( $conn ) {
1218                                         return $conn->getReplicaPos();
1219                                 }
1220                         }
1221                 } else {
1222                         return $masterConn->getMasterPos();
1223                 }
1224
1225                 return false;
1226         }
1227
1228         public function disable() {
1229                 $this->closeAll();
1230                 $this->disabled = true;
1231         }
1232
1233         public function closeAll() {
1234                 $this->forEachOpenConnection( function ( IDatabase $conn ) {
1235                         $host = $conn->getServer();
1236                         $this->connLogger->debug(
1237                                 __METHOD__ . ": closing connection to database '$host'." );
1238                         $conn->close();
1239                 } );
1240
1241                 $this->conns = [
1242                         self::KEY_LOCAL => [],
1243                         self::KEY_FOREIGN_INUSE => [],
1244                         self::KEY_FOREIGN_FREE => [],
1245                         self::KEY_LOCAL_NOROUND => [],
1246                         self::KEY_FOREIGN_INUSE_NOROUND => [],
1247                         self::KEY_FOREIGN_FREE_NOROUND => []
1248                 ];
1249                 $this->connsOpened = 0;
1250         }
1251
1252         public function closeConnection( IDatabase $conn ) {
1253                 $serverIndex = $conn->getLBInfo( 'serverIndex' );
1254                 foreach ( $this->conns as $type => $connsByServer ) {
1255                         if ( !isset( $connsByServer[$serverIndex] ) ) {
1256                                 continue;
1257                         }
1258
1259                         foreach ( $connsByServer[$serverIndex] as $i => $trackedConn ) {
1260                                 if ( $conn === $trackedConn ) {
1261                                         $host = $this->getServerName( $i );
1262                                         $this->connLogger->debug(
1263                                                 __METHOD__ . ": closing connection to database $i at '$host'." );
1264                                         unset( $this->conns[$type][$serverIndex][$i] );
1265                                         --$this->connsOpened;
1266                                         break 2;
1267                                 }
1268                         }
1269                 }
1270
1271                 $conn->close();
1272         }
1273
1274         public function commitAll( $fname = __METHOD__ ) {
1275                 $this->commitMasterChanges( $fname );
1276                 $this->flushMasterSnapshots( $fname );
1277                 $this->flushReplicaSnapshots( $fname );
1278         }
1279
1280         public function finalizeMasterChanges() {
1281                 $this->assertTransactionRoundStage( [ self::ROUND_CURSORY, self::ROUND_FINALIZED ] );
1282
1283                 $this->trxRoundStage = self::ROUND_ERROR; // "failed" until proven otherwise
1284                 // Loop until callbacks stop adding callbacks on other connections
1285                 $total = 0;
1286                 do {
1287                         $count = 0; // callbacks execution attempts
1288                         $this->forEachOpenMasterConnection( function ( Database $conn ) use ( &$count ) {
1289                                 // Run any pre-commit callbacks while leaving the post-commit ones suppressed.
1290                                 // Any error should cause all (peer) transactions to be rolled back together.
1291                                 $count += $conn->runOnTransactionPreCommitCallbacks();
1292                         } );
1293                         $total += $count;
1294                 } while ( $count > 0 );
1295                 // Defer post-commit callbacks until after COMMIT/ROLLBACK happens on all handles
1296                 $this->forEachOpenMasterConnection( function ( Database $conn ) {
1297                         $conn->setTrxEndCallbackSuppression( true );
1298                 } );
1299                 $this->trxRoundStage = self::ROUND_FINALIZED;
1300
1301                 return $total;
1302         }
1303
1304         public function approveMasterChanges( array $options ) {
1305                 $this->assertTransactionRoundStage( self::ROUND_FINALIZED );
1306
1307                 $limit = $options['maxWriteDuration'] ?? 0;
1308
1309                 $this->trxRoundStage = self::ROUND_ERROR; // "failed" until proven otherwise
1310                 $this->forEachOpenMasterConnection( function ( IDatabase $conn ) use ( $limit ) {
1311                         // If atomic sections or explicit transactions are still open, some caller must have
1312                         // caught an exception but failed to properly rollback any changes. Detect that and
1313                         // throw and error (causing rollback).
1314                         if ( $conn->explicitTrxActive() ) {
1315                                 throw new DBTransactionError(
1316                                         $conn,
1317                                         "Explicit transaction still active. A caller may have caught an error."
1318                                 );
1319                         }
1320                         // Assert that the time to replicate the transaction will be sane.
1321                         // If this fails, then all DB transactions will be rollback back together.
1322                         $time = $conn->pendingWriteQueryDuration( $conn::ESTIMATE_DB_APPLY );
1323                         if ( $limit > 0 && $time > $limit ) {
1324                                 throw new DBTransactionSizeError(
1325                                         $conn,
1326                                         "Transaction spent $time second(s) in writes, exceeding the limit of $limit.",
1327                                         [ $time, $limit ]
1328                                 );
1329                         }
1330                         // If a connection sits idle while slow queries execute on another, that connection
1331                         // may end up dropped before the commit round is reached. Ping servers to detect this.
1332                         if ( $conn->writesOrCallbacksPending() && !$conn->ping() ) {
1333                                 throw new DBTransactionError(
1334                                         $conn,
1335                                         "A connection to the {$conn->getDBname()} database was lost before commit."
1336                                 );
1337                         }
1338                 } );
1339                 $this->trxRoundStage = self::ROUND_APPROVED;
1340         }
1341
1342         public function beginMasterChanges( $fname = __METHOD__ ) {
1343                 if ( $this->trxRoundId !== false ) {
1344                         throw new DBTransactionError(
1345                                 null,
1346                                 "$fname: Transaction round '{$this->trxRoundId}' already started."
1347                         );
1348                 }
1349                 $this->assertTransactionRoundStage( self::ROUND_CURSORY );
1350
1351                 // Clear any empty transactions (no writes/callbacks) from the implicit round
1352                 $this->flushMasterSnapshots( $fname );
1353
1354                 $this->trxRoundId = $fname;
1355                 $this->trxRoundStage = self::ROUND_ERROR; // "failed" until proven otherwise
1356                 // Mark applicable handles as participating in this explicit transaction round.
1357                 // For each of these handles, any writes and callbacks will be tied to a single
1358                 // transaction. The (peer) handles will reject begin()/commit() calls unless they
1359                 // are part of an en masse commit or an en masse rollback.
1360                 $this->forEachOpenMasterConnection( function ( Database $conn ) {
1361                         $this->applyTransactionRoundFlags( $conn );
1362                 } );
1363                 $this->trxRoundStage = self::ROUND_CURSORY;
1364         }
1365
1366         public function commitMasterChanges( $fname = __METHOD__ ) {
1367                 $this->assertTransactionRoundStage( self::ROUND_APPROVED );
1368
1369                 $failures = [];
1370
1371                 /** @noinspection PhpUnusedLocalVariableInspection */
1372                 $scope = $this->getScopedPHPBehaviorForCommit(); // try to ignore client aborts
1373
1374                 $restore = ( $this->trxRoundId !== false );
1375                 $this->trxRoundId = false;
1376                 $this->trxRoundStage = self::ROUND_ERROR; // "failed" until proven otherwise
1377                 // Commit any writes and clear any snapshots as well (callbacks require AUTOCOMMIT).
1378                 // Note that callbacks should already be suppressed due to finalizeMasterChanges().
1379                 $this->forEachOpenMasterConnection(
1380                         function ( IDatabase $conn ) use ( $fname, &$failures ) {
1381                                 try {
1382                                         $conn->commit( $fname, $conn::FLUSHING_ALL_PEERS );
1383                                 } catch ( DBError $e ) {
1384                                         ( $this->errorLogger )( $e );
1385                                         $failures[] = "{$conn->getServer()}: {$e->getMessage()}";
1386                                 }
1387                         }
1388                 );
1389                 if ( $failures ) {
1390                         throw new DBTransactionError(
1391                                 null,
1392                                 "$fname: Commit failed on server(s) " . implode( "\n", array_unique( $failures ) )
1393                         );
1394                 }
1395                 if ( $restore ) {
1396                         // Unmark handles as participating in this explicit transaction round
1397                         $this->forEachOpenMasterConnection( function ( Database $conn ) {
1398                                 $this->undoTransactionRoundFlags( $conn );
1399                         } );
1400                 }
1401                 $this->trxRoundStage = self::ROUND_COMMIT_CALLBACKS;
1402         }
1403
1404         public function runMasterTransactionIdleCallbacks() {
1405                 if ( $this->trxRoundStage === self::ROUND_COMMIT_CALLBACKS ) {
1406                         $type = IDatabase::TRIGGER_COMMIT;
1407                 } elseif ( $this->trxRoundStage === self::ROUND_ROLLBACK_CALLBACKS ) {
1408                         $type = IDatabase::TRIGGER_ROLLBACK;
1409                 } else {
1410                         throw new DBTransactionError(
1411                                 null,
1412                                 "Transaction should be in the callback stage (not '{$this->trxRoundStage}')"
1413                         );
1414                 }
1415
1416                 $oldStage = $this->trxRoundStage;
1417                 $this->trxRoundStage = self::ROUND_ERROR; // "failed" until proven otherwise
1418
1419                 // Now that the COMMIT/ROLLBACK step is over, enable post-commit callback runs
1420                 $this->forEachOpenMasterConnection( function ( Database $conn ) {
1421                         $conn->setTrxEndCallbackSuppression( false );
1422                 } );
1423
1424                 $e = null; // first exception
1425                 // Loop until callbacks stop adding callbacks on other connections
1426                 do {
1427                         // Run any pending callbacks for each connection...
1428                         $count = 0; // callback execution attempts
1429                         $this->forEachOpenMasterConnection(
1430                                 function ( Database $conn ) use ( $type, &$e, &$count ) {
1431                                         if ( $conn->trxLevel() ) {
1432                                                 return; // retry in the next iteration, after commit() is called
1433                                         }
1434                                         try {
1435                                                 $count += $conn->runOnTransactionIdleCallbacks( $type );
1436                                         } catch ( Exception $ex ) {
1437                                                 $e = $e ?: $ex;
1438                                         }
1439                                 }
1440                         );
1441                         // Clear out any active transactions left over from callbacks...
1442                         $this->forEachOpenMasterConnection( function ( Database $conn ) use ( &$e ) {
1443                                 if ( $conn->writesPending() ) {
1444                                         // A callback from another handle wrote to this one and DBO_TRX is set
1445                                         $this->queryLogger->warning( __METHOD__ . ": found writes pending." );
1446                                         $fnames = implode( ', ', $conn->pendingWriteAndCallbackCallers() );
1447                                         $this->queryLogger->warning(
1448                                                 __METHOD__ . ": found writes pending ($fnames).",
1449                                                 [
1450                                                         'db_server' => $conn->getServer(),
1451                                                         'db_name' => $conn->getDBname()
1452                                                 ]
1453                                         );
1454                                 } elseif ( $conn->trxLevel() ) {
1455                                         // A callback from another handle read from this one and DBO_TRX is set,
1456                                         // which can easily happen if there is only one DB (no replicas)
1457                                         $this->queryLogger->debug( __METHOD__ . ": found empty transaction." );
1458                                 }
1459                                 try {
1460                                         $conn->commit( __METHOD__, $conn::FLUSHING_ALL_PEERS );
1461                                 } catch ( Exception $ex ) {
1462                                         $e = $e ?: $ex;
1463                                 }
1464                         } );
1465                 } while ( $count > 0 );
1466
1467                 $this->trxRoundStage = $oldStage;
1468
1469                 return $e;
1470         }
1471
1472         public function runMasterTransactionListenerCallbacks() {
1473                 if ( $this->trxRoundStage === self::ROUND_COMMIT_CALLBACKS ) {
1474                         $type = IDatabase::TRIGGER_COMMIT;
1475                 } elseif ( $this->trxRoundStage === self::ROUND_ROLLBACK_CALLBACKS ) {
1476                         $type = IDatabase::TRIGGER_ROLLBACK;
1477                 } else {
1478                         throw new DBTransactionError(
1479                                 null,
1480                                 "Transaction should be in the callback stage (not '{$this->trxRoundStage}')"
1481                         );
1482                 }
1483
1484                 $e = null;
1485
1486                 $this->trxRoundStage = self::ROUND_ERROR; // "failed" until proven otherwise
1487                 $this->forEachOpenMasterConnection( function ( Database $conn ) use ( $type, &$e ) {
1488                         try {
1489                                 $conn->runTransactionListenerCallbacks( $type );
1490                         } catch ( Exception $ex ) {
1491                                 $e = $e ?: $ex;
1492                         }
1493                 } );
1494                 $this->trxRoundStage = self::ROUND_CURSORY;
1495
1496                 return $e;
1497         }
1498
1499         public function rollbackMasterChanges( $fname = __METHOD__ ) {
1500                 $restore = ( $this->trxRoundId !== false );
1501                 $this->trxRoundId = false;
1502                 $this->trxRoundStage = self::ROUND_ERROR; // "failed" until proven otherwise
1503                 $this->forEachOpenMasterConnection( function ( IDatabase $conn ) use ( $fname ) {
1504                         $conn->rollback( $fname, $conn::FLUSHING_ALL_PEERS );
1505                 } );
1506                 if ( $restore ) {
1507                         // Unmark handles as participating in this explicit transaction round
1508                         $this->forEachOpenMasterConnection( function ( Database $conn ) {
1509                                 $this->undoTransactionRoundFlags( $conn );
1510                         } );
1511                 }
1512                 $this->trxRoundStage = self::ROUND_ROLLBACK_CALLBACKS;
1513         }
1514
1515         /**
1516          * @param string|string[] $stage
1517          */
1518         private function assertTransactionRoundStage( $stage ) {
1519                 $stages = (array)$stage;
1520
1521                 if ( !in_array( $this->trxRoundStage, $stages, true ) ) {
1522                         $stageList = implode(
1523                                 '/',
1524                                 array_map( function ( $v ) {
1525                                         return "'$v'";
1526                                 }, $stages )
1527                         );
1528                         throw new DBTransactionError(
1529                                 null,
1530                                 "Transaction round stage must be $stageList (not '{$this->trxRoundStage}')"
1531                         );
1532                 }
1533         }
1534
1535         /**
1536          * Make all DB servers with DBO_DEFAULT/DBO_TRX set join the transaction round
1537          *
1538          * Some servers may have neither flag enabled, meaning that they opt out of such
1539          * transaction rounds and remain in auto-commit mode. Such behavior might be desired
1540          * when a DB server is used for something like simple key/value storage.
1541          *
1542          * @param Database $conn
1543          */
1544         private function applyTransactionRoundFlags( Database $conn ) {
1545                 if ( $conn->getLBInfo( 'autoCommitOnly' ) ) {
1546                         return; // transaction rounds do not apply to these connections
1547                 }
1548
1549                 if ( $conn->getFlag( $conn::DBO_DEFAULT ) ) {
1550                         // DBO_TRX is controlled entirely by CLI mode presence with DBO_DEFAULT.
1551                         // Force DBO_TRX even in CLI mode since a commit round is expected soon.
1552                         $conn->setFlag( $conn::DBO_TRX, $conn::REMEMBER_PRIOR );
1553                 }
1554
1555                 if ( $conn->getFlag( $conn::DBO_TRX ) ) {
1556                         $conn->setLBInfo( 'trxRoundId', $this->trxRoundId );
1557                 }
1558         }
1559
1560         /**
1561          * @param Database $conn
1562          */
1563         private function undoTransactionRoundFlags( Database $conn ) {
1564                 if ( $conn->getLBInfo( 'autoCommitOnly' ) ) {
1565                         return; // transaction rounds do not apply to these connections
1566                 }
1567
1568                 if ( $conn->getFlag( $conn::DBO_TRX ) ) {
1569                         $conn->setLBInfo( 'trxRoundId', false );
1570                 }
1571
1572                 if ( $conn->getFlag( $conn::DBO_DEFAULT ) ) {
1573                         $conn->restoreFlags( $conn::RESTORE_PRIOR );
1574                 }
1575         }
1576
1577         public function flushReplicaSnapshots( $fname = __METHOD__ ) {
1578                 $this->forEachOpenReplicaConnection( function ( IDatabase $conn ) use ( $fname ) {
1579                         $conn->flushSnapshot( $fname );
1580                 } );
1581         }
1582
1583         public function flushMasterSnapshots( $fname = __METHOD__ ) {
1584                 $this->forEachOpenMasterConnection( function ( IDatabase $conn ) use ( $fname ) {
1585                         $conn->flushSnapshot( $fname );
1586                 } );
1587         }
1588
1589         /**
1590          * @return string
1591          * @since 1.32
1592          */
1593         public function getTransactionRoundStage() {
1594                 return $this->trxRoundStage;
1595         }
1596
1597         public function hasMasterConnection() {
1598                 return $this->isOpen( $this->getWriterIndex() );
1599         }
1600
1601         public function hasMasterChanges() {
1602                 $pending = 0;
1603                 $this->forEachOpenMasterConnection( function ( IDatabase $conn ) use ( &$pending ) {
1604                         $pending |= $conn->writesOrCallbacksPending();
1605                 } );
1606
1607                 return (bool)$pending;
1608         }
1609
1610         public function lastMasterChangeTimestamp() {
1611                 $lastTime = false;
1612                 $this->forEachOpenMasterConnection( function ( IDatabase $conn ) use ( &$lastTime ) {
1613                         $lastTime = max( $lastTime, $conn->lastDoneWrites() );
1614                 } );
1615
1616                 return $lastTime;
1617         }
1618
1619         public function hasOrMadeRecentMasterChanges( $age = null ) {
1620                 $age = ( $age === null ) ? $this->waitTimeout : $age;
1621
1622                 return ( $this->hasMasterChanges()
1623                         || $this->lastMasterChangeTimestamp() > microtime( true ) - $age );
1624         }
1625
1626         public function pendingMasterChangeCallers() {
1627                 $fnames = [];
1628                 $this->forEachOpenMasterConnection( function ( IDatabase $conn ) use ( &$fnames ) {
1629                         $fnames = array_merge( $fnames, $conn->pendingWriteCallers() );
1630                 } );
1631
1632                 return $fnames;
1633         }
1634
1635         public function getLaggedReplicaMode( $domain = false ) {
1636                 // No-op if there is only one DB (also avoids recursion)
1637                 if ( !$this->laggedReplicaMode && $this->getServerCount() > 1 ) {
1638                         try {
1639                                 // See if laggedReplicaMode gets set
1640                                 $conn = $this->getConnection( self::DB_REPLICA, false, $domain );
1641                                 $this->reuseConnection( $conn );
1642                         } catch ( DBConnectionError $e ) {
1643                                 // Avoid expensive re-connect attempts and failures
1644                                 $this->allReplicasDownMode = true;
1645                                 $this->laggedReplicaMode = true;
1646                         }
1647                 }
1648
1649                 return $this->laggedReplicaMode;
1650         }
1651
1652         public function laggedReplicaUsed() {
1653                 return $this->laggedReplicaMode;
1654         }
1655
1656         /**
1657          * @return bool
1658          * @since 1.27
1659          * @deprecated Since 1.28; use laggedReplicaUsed()
1660          */
1661         public function laggedSlaveUsed() {
1662                 return $this->laggedReplicaUsed();
1663         }
1664
1665         public function getReadOnlyReason( $domain = false, IDatabase $conn = null ) {
1666                 if ( $this->readOnlyReason !== false ) {
1667                         return $this->readOnlyReason;
1668                 } elseif ( $this->getLaggedReplicaMode( $domain ) ) {
1669                         if ( $this->allReplicasDownMode ) {
1670                                 return 'The database has been automatically locked ' .
1671                                         'until the replica database servers become available';
1672                         } else {
1673                                 return 'The database has been automatically locked ' .
1674                                         'while the replica database servers catch up to the master.';
1675                         }
1676                 } elseif ( $this->masterRunningReadOnly( $domain, $conn ) ) {
1677                         return 'The database master is running in read-only mode.';
1678                 }
1679
1680                 return false;
1681         }
1682
1683         /**
1684          * @param string $domain Domain ID, or false for the current domain
1685          * @param IDatabase|null $conn DB master connectionl used to avoid loops [optional]
1686          * @return bool
1687          */
1688         private function masterRunningReadOnly( $domain, IDatabase $conn = null ) {
1689                 $cache = $this->wanCache;
1690                 $masterServer = $this->getServerName( $this->getWriterIndex() );
1691
1692                 return (bool)$cache->getWithSetCallback(
1693                         $cache->makeGlobalKey( __CLASS__, 'server-read-only', $masterServer ),
1694                         self::TTL_CACHE_READONLY,
1695                         function () use ( $domain, $conn ) {
1696                                 $old = $this->trxProfiler->setSilenced( true );
1697                                 try {
1698                                         $dbw = $conn ?: $this->getConnection( self::DB_MASTER, [], $domain );
1699                                         $readOnly = (int)$dbw->serverIsReadOnly();
1700                                         if ( !$conn ) {
1701                                                 $this->reuseConnection( $dbw );
1702                                         }
1703                                 } catch ( DBError $e ) {
1704                                         $readOnly = 0;
1705                                 }
1706                                 $this->trxProfiler->setSilenced( $old );
1707                                 return $readOnly;
1708                         },
1709                         [ 'pcTTL' => $cache::TTL_PROC_LONG, 'busyValue' => 0 ]
1710                 );
1711         }
1712
1713         public function allowLagged( $mode = null ) {
1714                 if ( $mode === null ) {
1715                         return $this->allowLagged;
1716                 }
1717                 $this->allowLagged = $mode;
1718
1719                 return $this->allowLagged;
1720         }
1721
1722         public function pingAll() {
1723                 $success = true;
1724                 $this->forEachOpenConnection( function ( IDatabase $conn ) use ( &$success ) {
1725                         if ( !$conn->ping() ) {
1726                                 $success = false;
1727                         }
1728                 } );
1729
1730                 return $success;
1731         }
1732
1733         public function forEachOpenConnection( $callback, array $params = [] ) {
1734                 foreach ( $this->conns as $connsByServer ) {
1735                         foreach ( $connsByServer as $serverConns ) {
1736                                 foreach ( $serverConns as $conn ) {
1737                                         $callback( $conn, ...$params );
1738                                 }
1739                         }
1740                 }
1741         }
1742
1743         public function forEachOpenMasterConnection( $callback, array $params = [] ) {
1744                 $masterIndex = $this->getWriterIndex();
1745                 foreach ( $this->conns as $connsByServer ) {
1746                         if ( isset( $connsByServer[$masterIndex] ) ) {
1747                                 /** @var IDatabase $conn */
1748                                 foreach ( $connsByServer[$masterIndex] as $conn ) {
1749                                         $callback( $conn, ...$params );
1750                                 }
1751                         }
1752                 }
1753         }
1754
1755         public function forEachOpenReplicaConnection( $callback, array $params = [] ) {
1756                 foreach ( $this->conns as $connsByServer ) {
1757                         foreach ( $connsByServer as $i => $serverConns ) {
1758                                 if ( $i === $this->getWriterIndex() ) {
1759                                         continue; // skip master
1760                                 }
1761                                 foreach ( $serverConns as $conn ) {
1762                                         $callback( $conn, ...$params );
1763                                 }
1764                         }
1765                 }
1766         }
1767
1768         public function getMaxLag( $domain = false ) {
1769                 $maxLag = -1;
1770                 $host = '';
1771                 $maxIndex = 0;
1772
1773                 if ( $this->getServerCount() <= 1 ) {
1774                         return [ $host, $maxLag, $maxIndex ]; // no replication = no lag
1775                 }
1776
1777                 $lagTimes = $this->getLagTimes( $domain );
1778                 foreach ( $lagTimes as $i => $lag ) {
1779                         if ( $this->loads[$i] > 0 && $lag > $maxLag ) {
1780                                 $maxLag = $lag;
1781                                 $host = $this->servers[$i]['host'];
1782                                 $maxIndex = $i;
1783                         }
1784                 }
1785
1786                 return [ $host, $maxLag, $maxIndex ];
1787         }
1788
1789         public function getLagTimes( $domain = false ) {
1790                 if ( $this->getServerCount() <= 1 ) {
1791                         return [ $this->getWriterIndex() => 0 ]; // no replication = no lag
1792                 }
1793
1794                 $knownLagTimes = []; // map of (server index => 0 seconds)
1795                 $indexesWithLag = [];
1796                 foreach ( $this->servers as $i => $server ) {
1797                         if ( empty( $server['is static'] ) ) {
1798                                 $indexesWithLag[] = $i; // DB server might have replication lag
1799                         } else {
1800                                 $knownLagTimes[$i] = 0; // DB server is a non-replicating and read-only archive
1801                         }
1802                 }
1803
1804                 return $this->getLoadMonitor()->getLagTimes( $indexesWithLag, $domain ) + $knownLagTimes;
1805         }
1806
1807         public function safeGetLag( IDatabase $conn ) {
1808                 if ( $this->getServerCount() <= 1 ) {
1809                         return 0;
1810                 } else {
1811                         return $conn->getLag();
1812                 }
1813         }
1814
1815         /**
1816          * @param IDatabase $conn
1817          * @param DBMasterPos|bool $pos
1818          * @param int|null $timeout
1819          * @return bool
1820          */
1821         public function safeWaitForMasterPos( IDatabase $conn, $pos = false, $timeout = null ) {
1822                 $timeout = max( 1, $timeout ?: $this->waitTimeout );
1823
1824                 if ( $this->getServerCount() <= 1 || !$conn->getLBInfo( 'replica' ) ) {
1825                         return true; // server is not a replica DB
1826                 }
1827
1828                 if ( !$pos ) {
1829                         // Get the current master position, opening a connection if needed
1830                         $masterConn = $this->getAnyOpenConnection( $this->getWriterIndex() );
1831                         if ( $masterConn ) {
1832                                 $pos = $masterConn->getMasterPos();
1833                         } else {
1834                                 $masterConn = $this->openConnection( $this->getWriterIndex(), self::DOMAIN_ANY );
1835                                 $pos = $masterConn->getMasterPos();
1836                                 $this->closeConnection( $masterConn );
1837                         }
1838                 }
1839
1840                 if ( $pos instanceof DBMasterPos ) {
1841                         $result = $conn->masterPosWait( $pos, $timeout );
1842                         if ( $result == -1 || is_null( $result ) ) {
1843                                 $msg = __METHOD__ . ': timed out waiting on {host} pos {pos}';
1844                                 $this->replLogger->warning( $msg, [
1845                                         'host' => $conn->getServer(),
1846                                         'pos' => $pos,
1847                                         'trace' => ( new RuntimeException() )->getTraceAsString()
1848                                 ] );
1849                                 $ok = false;
1850                         } else {
1851                                 $this->replLogger->debug( __METHOD__ . ': done waiting' );
1852                                 $ok = true;
1853                         }
1854                 } else {
1855                         $ok = false; // something is misconfigured
1856                         $this->replLogger->error(
1857                                 __METHOD__ . ': could not get master pos for {host}',
1858                                 [
1859                                         'host' => $conn->getServer(),
1860                                         'trace' => ( new RuntimeException() )->getTraceAsString()
1861                                 ]
1862                         );
1863                 }
1864
1865                 return $ok;
1866         }
1867
1868         public function setTransactionListener( $name, callable $callback = null ) {
1869                 if ( $callback ) {
1870                         $this->trxRecurringCallbacks[$name] = $callback;
1871                 } else {
1872                         unset( $this->trxRecurringCallbacks[$name] );
1873                 }
1874                 $this->forEachOpenMasterConnection(
1875                         function ( IDatabase $conn ) use ( $name, $callback ) {
1876                                 $conn->setTransactionListener( $name, $callback );
1877                         }
1878                 );
1879         }
1880
1881         public function setTableAliases( array $aliases ) {
1882                 $this->tableAliases = $aliases;
1883         }
1884
1885         public function setIndexAliases( array $aliases ) {
1886                 $this->indexAliases = $aliases;
1887         }
1888
1889         public function setDomainPrefix( $prefix ) {
1890                 // Find connections to explicit foreign domains still marked as in-use...
1891                 $domainsInUse = [];
1892                 $this->forEachOpenConnection( function ( IDatabase $conn ) use ( &$domainsInUse ) {
1893                         // Once reuseConnection() is called on a handle, its reference count goes from 1 to 0.
1894                         // Until then, it is still in use by the caller (explicitly or via DBConnRef scope).
1895                         if ( $conn->getLBInfo( 'foreignPoolRefCount' ) > 0 ) {
1896                                 $domainsInUse[] = $conn->getDomainID();
1897                         }
1898                 } );
1899
1900                 // Do not switch connections to explicit foreign domains unless marked as safe
1901                 if ( $domainsInUse ) {
1902                         $domains = implode( ', ', $domainsInUse );
1903                         throw new DBUnexpectedError( null,
1904                                 "Foreign domain connections are still in use ($domains)." );
1905                 }
1906
1907                 $oldDomain = $this->localDomain->getId();
1908                 $this->setLocalDomain( new DatabaseDomain(
1909                         $this->localDomain->getDatabase(),
1910                         $this->localDomain->getSchema(),
1911                         $prefix
1912                 ) );
1913
1914                 $this->forEachOpenConnection( function ( IDatabase $db ) use ( $prefix, $oldDomain ) {
1915                         if ( !$db->getLBInfo( 'foreign' ) ) {
1916                                 $db->tablePrefix( $prefix );
1917                         }
1918                 } );
1919         }
1920
1921         /**
1922          * @param DatabaseDomain $domain
1923          */
1924         private function setLocalDomain( DatabaseDomain $domain ) {
1925                 $this->localDomain = $domain;
1926                 // In case a caller assumes that the domain ID is simply <db>-<prefix>, which is almost
1927                 // always true, gracefully handle the case when they fail to account for escaping.
1928                 if ( $this->localDomain->getTablePrefix() != '' ) {
1929                         $this->localDomainIdAlias =
1930                                 $this->localDomain->getDatabase() . '-' . $this->localDomain->getTablePrefix();
1931                 } else {
1932                         $this->localDomainIdAlias = $this->localDomain->getDatabase();
1933                 }
1934         }
1935
1936         /**
1937          * Make PHP ignore user aborts/disconnects until the returned
1938          * value leaves scope. This returns null and does nothing in CLI mode.
1939          *
1940          * @return ScopedCallback|null
1941          */
1942         final protected function getScopedPHPBehaviorForCommit() {
1943                 if ( PHP_SAPI != 'cli' ) { // https://bugs.php.net/bug.php?id=47540
1944                         $old = ignore_user_abort( true ); // avoid half-finished operations
1945                         return new ScopedCallback( function () use ( $old ) {
1946                                 ignore_user_abort( $old );
1947                         } );
1948                 }
1949
1950                 return null;
1951         }
1952
1953         function __destruct() {
1954                 // Avoid connection leaks for sanity
1955                 $this->disable();
1956         }
1957 }
1958
1959 /**
1960  * @deprecated since 1.29
1961  */
1962 class_alias( LoadBalancer::class, 'LoadBalancer' );