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 UnexpectedValueException;
  32 use InvalidArgumentException;
  33 use RuntimeException;
  34 use Exception;
  35
  36 /**
  37  * Database connection, tracking, load balancing, and transaction manager for a cluster
  38  *
  39  * @ingroup Database
  40  */
  41 class LoadBalancer implements ILoadBalancer {
  42         /** @var ILoadMonitor */
  43         private $loadMonitor;
  44         /** @var callable|null Callback to run before the first connection attempt */
  45         private $chronologyCallback;
  46         /** @var BagOStuff */
  47         private $srvCache;
  48         /** @var WANObjectCache */
  49         private $wanCache;
  50         /** @var object|string Class name or object With profileIn/profileOut methods */
  51         private $profiler;
  52         /** @var TransactionProfiler */
  53         private $trxProfiler;
  54         /** @var LoggerInterface */
  55         private $replLogger;
  56         /** @var LoggerInterface */
  57         private $connLogger;
  58         /** @var LoggerInterface */
  59         private $queryLogger;
  60         /** @var LoggerInterface */
  61         private $perfLogger;
  62         /** @var callable Exception logger */
  63         private $errorLogger;
  64         /** @var callable Deprecation logger */
  65         private $deprecationLogger;
  66
  67         /** @var DatabaseDomain Local Domain ID and default for selectDB() calls */
  68         private $localDomain;
  69
  70         /** @var Database[][][] Map of (connection category => server index => IDatabase[]) */
  71         private $conns;
  72
  73         /** @var array[] Map of (server index => server config array) */
  74         private $servers;
  75         /** @var float[] Map of (server index => weight) */
  76         private $loads;
  77         /** @var array[] Map of (group => server index => weight) */
  78         private $groupLoads;
  79         /** @var bool Whether to disregard replica DB lag as a factor in replica DB selection */
  80         private $allowLagged;
  81         /** @var int Seconds to spend waiting on replica DB lag to resolve */
  82         private $waitTimeout;
  83         /** @var array The LoadMonitor configuration */
  84         private $loadMonitorConfig;
  85         /** @var string Alternate ID string for the domain instead of DatabaseDomain::getId() */
  86         private $localDomainIdAlias;
  87         /** @var int */
  88         private $maxLag = self::MAX_LAG_DEFAULT;
  89
  90         /** @var string Current server name */
  91         private $hostname;
  92         /** @var bool Whether this PHP instance is for a CLI script */
  93         private $cliMode;
  94         /** @var string Agent name for query profiling */
  95         private $agent;
  96
  97         /** @var array[] $aliases Map of (table => (dbname, schema, prefix) map) */
  98         private $tableAliases = [];
  99         /** @var string[] Map of (index alias => index) */
 100         private $indexAliases = [];
 101         /** @var array[] Map of (name => callable) */
 102         private $trxRecurringCallbacks = [];
 103
 104         /** @var Database DB connection object that caused a problem */
 105         private $errorConnection;
 106         /** @var int The generic (not query grouped) replica DB index (of $mServers) */
 107         private $readIndex;
 108         /** @var bool|DBMasterPos False if not set */
 109         private $waitForPos;
 110         /** @var bool Whether the generic reader fell back to a lagged replica DB */
 111         private $laggedReplicaMode = false;
 112         /** @var bool Whether the generic reader fell back to a lagged replica DB */
 113         private $allReplicasDownMode = false;
 114         /** @var string The last DB selection or connection error */
 115         private $lastError = 'Unknown error';
 116         /** @var string|bool Reason the LB is read-only or false if not */
 117         private $readOnlyReason = false;
 118         /** @var int Total connections opened */
 119         private $connsOpened = 0;
 120         /** @var bool */
 121         private $disabled = false;
 122         /** @var bool Whether any connection has been attempted yet */
 123         private $connectionAttempted = false;
 124
 125         /** @var string|bool String if a requested DBO_TRX transaction round is active */
 126         private $trxRoundId = false;
 127         /** @var string Stage of the current transaction round in the transaction round life-cycle */
 128         private $trxRoundStage = self::ROUND_CURSORY;
 129
 130         /** @var string|null */
 131         private $defaultGroup = null;
 132
 133         /** @var int Warn when this many connection are held */
 134         const CONN_HELD_WARN_THRESHOLD = 10;
 135
 136         /** @var int Default 'maxLag' when unspecified */
 137         const MAX_LAG_DEFAULT = 10;
 138         /** @var int Default 'waitTimeout' when unspecified */
 139         const MAX_WAIT_DEFAULT = 10;
 140         /** @var int Seconds to cache master server read-only status */
 141         const TTL_CACHE_READONLY = 5;
 142
 143         const KEY_LOCAL = 'local';
 144         const KEY_FOREIGN_FREE = 'foreignFree';
 145         const KEY_FOREIGN_INUSE = 'foreignInUse';
 146
 147         const KEY_LOCAL_NOROUND = 'localAutoCommit';
 148         const KEY_FOREIGN_FREE_NOROUND = 'foreignFreeAutoCommit';
 149         const KEY_FOREIGN_INUSE_NOROUND = 'foreignInUseAutoCommit';
 150
 151         /** @var string Transaction round, explicit or implicit, has not finished writing */
 152         const ROUND_CURSORY = 'cursory';
 153         /** @var string Transaction round writes are complete and ready for pre-commit checks */
 154         const ROUND_FINALIZED = 'finalized';
 155         /** @var string Transaction round passed final pre-commit checks */
 156         const ROUND_APPROVED = 'approved';
 157         /** @var string Transaction round was committed and post-commit callbacks must be run */
 158         const ROUND_COMMIT_CALLBACKS = 'commit-callbacks';
 159         /** @var string Transaction round was rolled back and post-rollback callbacks must be run */
 160         const ROUND_ROLLBACK_CALLBACKS = 'rollback-callbacks';
 161         /** @var string Transaction round encountered an error */
 162         const ROUND_ERROR = 'error';
 163
 164         public function __construct( array $params ) {
 165                 if ( !isset( $params['servers'] ) ) {
 166                         throw new InvalidArgumentException( __CLASS__ . ': missing servers parameter' );
 167                 }
 168                 $this->servers = $params['servers'];
 169                 foreach ( $this->servers as $i => $server ) {
 170                         if ( $i == 0 ) {
 171                                 $this->servers[$i]['master'] = true;
 172                         } else {
 173                                 $this->servers[$i]['replica'] = true;
 174                         }
 175                 }
 176
 177                 $localDomain = isset( $params['localDomain'] )
 178                         ? DatabaseDomain::newFromId( $params['localDomain'] )
 179                         : DatabaseDomain::newUnspecified();
 180                 $this->setLocalDomain( $localDomain );
 181
 182                 $this->waitTimeout = $params['waitTimeout'] ?? self::MAX_WAIT_DEFAULT;
 183
 184                 $this->readIndex = -1;
 185                 $this->conns = [
 186                         // Connection were transaction rounds may be applied
 187                         self::KEY_LOCAL => [],
 188                         self::KEY_FOREIGN_INUSE => [],
 189                         self::KEY_FOREIGN_FREE => [],
 190                         // Auto-committing counterpart connections that ignore transaction rounds
 191                         self::KEY_LOCAL_NOROUND => [],
 192                         self::KEY_FOREIGN_INUSE_NOROUND => [],
 193                         self::KEY_FOREIGN_FREE_NOROUND => []
 194                 ];
 195                 $this->loads = [];
 196                 $this->waitForPos = false;
 197                 $this->allowLagged = false;
 198
 199                 if ( isset( $params['readOnlyReason'] ) && is_string( $params['readOnlyReason'] ) ) {
 200                         $this->readOnlyReason = $params['readOnlyReason'];
 201                 }
 202
 203                 if ( isset( $params['maxLag'] ) ) {
 204                         $this->maxLag = $params['maxLag'];
 205                 }
 206
 207                 if ( isset( $params['loadMonitor'] ) ) {
 208                         $this->loadMonitorConfig = $params['loadMonitor'];
 209                 } else {
 210                         $this->loadMonitorConfig = [ 'class' => 'LoadMonitorNull' ];
 211                 }
 212                 $this->loadMonitorConfig += [ 'lagWarnThreshold' => $this->maxLag ];
 213
 214                 foreach ( $params['servers'] as $i => $server ) {
 215                         $this->loads[$i] = $server['load'];
 216                         if ( isset( $server['groupLoads'] ) ) {
 217                                 foreach ( $server['groupLoads'] as $group => $ratio ) {
 218                                         if ( !isset( $this->groupLoads[$group] ) ) {
 219                                                 $this->groupLoads[$group] = [];
 220                                         }
 221                                         $this->groupLoads[$group][$i] = $ratio;
 222                                 }
 223                         }
 224                 }
 225
 226                 if ( isset( $params['srvCache'] ) ) {
 227                         $this->srvCache = $params['srvCache'];
 228                 } else {
 229                         $this->srvCache = new EmptyBagOStuff();
 230                 }
 231                 if ( isset( $params['wanCache'] ) ) {
 232                         $this->wanCache = $params['wanCache'];
 233                 } else {
 234                         $this->wanCache = WANObjectCache::newEmpty();
 235                 }
 236                 $this->profiler = $params['profiler'] ?? null;
 237                 if ( isset( $params['trxProfiler'] ) ) {
 238                         $this->trxProfiler = $params['trxProfiler'];
 239                 } else {
 240                         $this->trxProfiler = new TransactionProfiler();
 241                 }
 242
 243                 $this->errorLogger = $params['errorLogger'] ?? function ( Exception $e ) {
 244                         trigger_error( get_class( $e ) . ': ' . $e->getMessage(), E_USER_WARNING );
 245                 };
 246                 $this->deprecationLogger = $params['deprecationLogger'] ?? function ( $msg ) {
 247                         trigger_error( $msg, E_USER_DEPRECATED );
 248                 };
 249
 250                 foreach ( [ 'replLogger', 'connLogger', 'queryLogger', 'perfLogger' ] as $key ) {
 251                         $this->$key = $params[$key] ?? new NullLogger();
 252                 }
 253
 254                 $this->hostname = $params['hostname'] ?? ( gethostname() ?: 'unknown' );
 255                 $this->cliMode = $params['cliMode'] ?? ( PHP_SAPI === 'cli' || PHP_SAPI === 'phpdbg' );
 256                 $this->agent = $params['agent'] ?? '';
 257
 258                 if ( isset( $params['chronologyCallback'] ) ) {
 259                         $this->chronologyCallback = $params['chronologyCallback'];
 260                 }
 261
 262                 if ( isset( $params['roundStage'] ) ) {
 263                         if ( $params['roundStage'] === self::STAGE_POSTCOMMIT_CALLBACKS ) {
 264                                 $this->trxRoundStage = self::ROUND_COMMIT_CALLBACKS;
 265                         } elseif ( $params['roundStage'] === self::STAGE_POSTROLLBACK_CALLBACKS ) {
 266                                 $this->trxRoundStage = self::ROUND_ROLLBACK_CALLBACKS;
 267                         }
 268                 }
 269
 270                 $this->defaultGroup = $params['defaultGroup'] ?? null;
 271         }
 272
 273         public function getLocalDomainID() {
 274                 return $this->localDomain->getId();
 275         }
 276
 277         public function resolveDomainID( $domain ) {
 278                 return ( $domain !== false ) ? (string)$domain : $this->getLocalDomainID();
 279         }
 280
 281         /**
 282          * Get a LoadMonitor instance
 283          *
 284          * @return ILoadMonitor
 285          */
 286         private function getLoadMonitor() {
 287                 if ( !isset( $this->loadMonitor ) ) {
 288                         $compat = [
 289                                 'LoadMonitor' => LoadMonitor::class,
 290                                 'LoadMonitorNull' => LoadMonitorNull::class,
 291                                 'LoadMonitorMySQL' => LoadMonitorMySQL::class,
 292                         ];
 293
 294                         $class = $this->loadMonitorConfig['class'];
 295                         if ( isset( $compat[$class] ) ) {
 296                                 $class = $compat[$class];
 297                         }
 298
 299                         $this->loadMonitor = new $class(
 300                                 $this, $this->srvCache, $this->wanCache, $this->loadMonitorConfig );
 301                         $this->loadMonitor->setLogger( $this->replLogger );
 302                 }
 303
 304                 return $this->loadMonitor;
 305         }
 306
 307         /**
 308          * @param array $loads
 309          * @param bool|string $domain Domain to get non-lagged for
 310          * @param int $maxLag Restrict the maximum allowed lag to this many seconds
 311          * @return bool|int|string
 312          */
 313         private function getRandomNonLagged( array $loads, $domain = false, $maxLag = INF ) {
 314                 $lags = $this->getLagTimes( $domain );
 315
 316                 # Unset excessively lagged servers
 317                 foreach ( $lags as $i => $lag ) {
 318                         if ( $i != 0 ) {
 319                                 # How much lag this server nominally is allowed to have
 320                                 $maxServerLag = $this->servers[$i]['max lag'] ?? $this->maxLag; // default
 321                                 # Constrain that futher by $maxLag argument
 322                                 $maxServerLag = min( $maxServerLag, $maxLag );
 323
 324                                 $host = $this->getServerName( $i );
 325                                 if ( $lag === false && !is_infinite( $maxServerLag ) ) {
 326                                         $this->replLogger->error(
 327                                                 __METHOD__ .
 328                                                 ": server {host} is not replicating?", [ 'host' => $host ] );
 329                                         unset( $loads[$i] );
 330                                 } elseif ( $lag > $maxServerLag ) {
 331                                         $this->replLogger->info(
 332                                                 __METHOD__ .
 333                                                 ": server {host} has {lag} seconds of lag (>= {maxlag})",
 334                                                 [ 'host' => $host, 'lag' => $lag, 'maxlag' => $maxServerLag ]
 335                                         );
 336                                         unset( $loads[$i] );
 337                                 }
 338                         }
 339                 }
 340
 341                 # Find out if all the replica DBs with non-zero load are lagged
 342                 $sum = 0;
 343                 foreach ( $loads as $load ) {
 344                         $sum += $load;
 345                 }
 346                 if ( $sum == 0 ) {
 347                         # No appropriate DB servers except maybe the master and some replica DBs with zero load
 348                         # Do NOT use the master
 349                         # Instead, this function will return false, triggering read-only mode,
 350                         # and a lagged replica DB will be used instead.
 351                         return false;
 352                 }
 353
 354                 if ( count( $loads ) == 0 ) {
 355                         return false;
 356                 }
 357
 358                 # Return a random representative of the remainder
 359                 return ArrayUtils::pickRandom( $loads );
 360         }
 361
 362         public function getReaderIndex( $group = false, $domain = false ) {
 363                 if ( count( $this->servers ) == 1 ) {
 364                         // Skip the load balancing if there's only one server
 365                         return $this->getWriterIndex();
 366                 } elseif ( $group === false && $this->readIndex >= 0 ) {
 367                         // Shortcut if the generic reader index was already cached
 368                         return $this->readIndex;
 369                 }
 370
 371                 if ( $group !== false ) {
 372                         // Use the server weight array for this load group
 373                         if ( isset( $this->groupLoads[$group] ) ) {
 374                                 $loads = $this->groupLoads[$group];
 375                         } else {
 376                                 // No loads for this group, return false and the caller can use some other group
 377                                 $this->connLogger->info( __METHOD__ . ": no loads for group $group" );
 378
 379                                 return false;
 380                         }
 381                 } else {
 382                         // Use the generic load group
 383                         $loads = $this->loads;
 384                 }
 385
 386                 // Scale the configured load ratios according to each server's load and state
 387                 $this->getLoadMonitor()->scaleLoads( $loads, $domain );
 388
 389                 // Pick a server to use, accounting for weights, load, lag, and "waitForPos"
 390                 list( $i, $laggedReplicaMode ) = $this->pickReaderIndex( $loads, $domain );
 391                 if ( $i === false ) {
 392                         // Replica DB connection unsuccessful
 393                         return false;
 394                 }
 395
 396                 if ( $this->waitForPos && $i != $this->getWriterIndex() ) {
 397                         // Before any data queries are run, wait for the server to catch up to the
 398                         // specified position. This is used to improve session consistency. Note that
 399                         // when LoadBalancer::waitFor() sets "waitForPos", the waiting triggers here,
 400                         // so update laggedReplicaMode as needed for consistency.
 401                         if ( !$this->doWait( $i ) ) {
 402                                 $laggedReplicaMode = true;
 403                         }
 404                 }
 405
 406                 if ( $this->readIndex <= 0 && $this->loads[$i] > 0 && $group === false ) {
 407                         // Cache the generic reader index for future ungrouped DB_REPLICA handles
 408                         $this->readIndex = $i;
 409                         // Record if the generic reader index is in "lagged replica DB" mode
 410                         if ( $laggedReplicaMode ) {
 411                                 $this->laggedReplicaMode = true;
 412                         }
 413                 }
 414
 415                 $serverName = $this->getServerName( $i );
 416                 $this->connLogger->debug( __METHOD__ . ": using server $serverName for group '$group'" );
 417
 418                 return $i;
 419         }
 420
 421         /**
 422          * @param array $loads List of server weights
 423          * @param string|bool $domain
 424          * @return array (reader index, lagged replica mode) or false on failure
 425          */
 426         private function pickReaderIndex( array $loads, $domain = false ) {
 427                 if ( !count( $loads ) ) {
 428                         throw new InvalidArgumentException( "Empty server array given to LoadBalancer" );
 429                 }
 430
 431                 /** @var int|bool $i Index of selected server */
 432                 $i = false;
 433                 /** @var bool $laggedReplicaMode Whether server is considered lagged */
 434                 $laggedReplicaMode = false;
 435
 436                 // Quickly look through the available servers for a server that meets criteria...
 437                 $currentLoads = $loads;
 438                 while ( count( $currentLoads ) ) {
 439                         if ( $this->allowLagged || $laggedReplicaMode ) {
 440                                 $i = ArrayUtils::pickRandom( $currentLoads );
 441                         } else {
 442                                 $i = false;
 443                                 if ( $this->waitForPos && $this->waitForPos->asOfTime() ) {
 444                                         // "chronologyCallback" sets "waitForPos" for session consistency.
 445                                         // This triggers doWait() after connect, so it's especially good to
 446                                         // avoid lagged servers so as to avoid excessive delay in that method.
 447                                         $ago = microtime( true ) - $this->waitForPos->asOfTime();
 448                                         // Aim for <= 1 second of waiting (being too picky can backfire)
 449                                         $i = $this->getRandomNonLagged( $currentLoads, $domain, $ago + 1 );
 450                                 }
 451                                 if ( $i === false ) {
 452                                         // Any server with less lag than it's 'max lag' param is preferable
 453                                         $i = $this->getRandomNonLagged( $currentLoads, $domain );
 454                                 }
 455                                 if ( $i === false && count( $currentLoads ) != 0 ) {
 456                                         // All replica DBs lagged. Switch to read-only mode
 457                                         $this->replLogger->error(
 458                                                 __METHOD__ . ": all replica DBs lagged. Switch to read-only mode" );
 459                                         $i = ArrayUtils::pickRandom( $currentLoads );
 460                                         $laggedReplicaMode = true;
 461                                 }
 462                         }
 463
 464                         if ( $i === false ) {
 465                                 // pickRandom() returned false.
 466                                 // This is permanent and means the configuration or the load monitor
 467                                 // wants us to return false.
 468                                 $this->connLogger->debug( __METHOD__ . ": pickRandom() returned false" );
 469
 470                                 return [ false, false ];
 471                         }
 472
 473                         $serverName = $this->getServerName( $i );
 474                         $this->connLogger->debug( __METHOD__ . ": Using reader #$i: $serverName..." );
 475
 476                         $conn = $this->openConnection( $i, $domain );
 477                         if ( !$conn ) {
 478                                 $this->connLogger->warning( __METHOD__ . ": Failed connecting to $i/$domain" );
 479                                 unset( $currentLoads[$i] ); // avoid this server next iteration
 480                                 $i = false;
 481                                 continue;
 482                         }
 483
 484                         // Decrement reference counter, we are finished with this connection.
 485                         // It will be incremented for the caller later.
 486                         if ( $domain !== false ) {
 487                                 $this->reuseConnection( $conn );
 488                         }
 489
 490                         // Return this server
 491                         break;
 492                 }
 493
 494                 // If all servers were down, quit now
 495                 if ( !count( $currentLoads ) ) {
 496                         $this->connLogger->error( __METHOD__ . ": all servers down" );
 497                 }
 498
 499                 return [ $i, $laggedReplicaMode ];
 500         }
 501
 502         public function waitFor( $pos ) {
 503                 $oldPos = $this->waitForPos;
 504                 try {
 505                         $this->waitForPos = $pos;
 506                         // If a generic reader connection was already established, then wait now
 507                         $i = $this->readIndex;
 508                         if ( $i > 0 ) {
 509                                 if ( !$this->doWait( $i ) ) {
 510                                         $this->laggedReplicaMode = true;
 511                                 }
 512                         }
 513                 } finally {
 514                         // Restore the older position if it was higher since this is used for lag-protection
 515                         $this->setWaitForPositionIfHigher( $oldPos );
 516                 }
 517         }
 518
 519         public function waitForOne( $pos, $timeout = null ) {
 520                 $oldPos = $this->waitForPos;
 521                 try {
 522                         $this->waitForPos = $pos;
 523
 524                         $i = $this->readIndex;
 525                         if ( $i <= 0 ) {
 526                                 // Pick a generic replica DB if there isn't one yet
 527                                 $readLoads = $this->loads;
 528                                 unset( $readLoads[$this->getWriterIndex()] ); // replica DBs only
 529                                 $readLoads = array_filter( $readLoads ); // with non-zero load
 530                                 $i = ArrayUtils::pickRandom( $readLoads );
 531                         }
 532
 533                         if ( $i > 0 ) {
 534                                 $ok = $this->doWait( $i, true, $timeout );
 535                         } else {
 536                                 $ok = true; // no applicable loads
 537                         }
 538                 } finally {
 539                         # Restore the old position, as this is not used for lag-protection but for throttling
 540                         $this->waitForPos = $oldPos;
 541                 }
 542
 543                 return $ok;
 544         }
 545
 546         public function waitForAll( $pos, $timeout = null ) {
 547                 $timeout = $timeout ?: $this->waitTimeout;
 548
 549                 $oldPos = $this->waitForPos;
 550                 try {
 551                         $this->waitForPos = $pos;
 552                         $serverCount = count( $this->servers );
 553
 554                         $ok = true;
 555                         for ( $i = 1; $i < $serverCount; $i++ ) {
 556                                 if ( $this->loads[$i] > 0 ) {
 557                                         $start = microtime( true );
 558                                         $ok = $this->doWait( $i, true, $timeout ) && $ok;
 559                                         $timeout -= intval( microtime( true ) - $start );
 560                                         if ( $timeout <= 0 ) {
 561                                                 break; // timeout reached
 562                                         }
 563                                 }
 564                         }
 565                 } finally {
 566                         # Restore the old position, as this is not used for lag-protection but for throttling
 567                         $this->waitForPos = $oldPos;
 568                 }
 569
 570                 return $ok;
 571         }
 572
 573         /**
 574          * @param DBMasterPos|bool $pos
 575          */
 576         private function setWaitForPositionIfHigher( $pos ) {
 577                 if ( !$pos ) {
 578                         return;
 579                 }
 580
 581                 if ( !$this->waitForPos || $pos->hasReached( $this->waitForPos ) ) {
 582                         $this->waitForPos = $pos;
 583                 }
 584         }
 585
 586         public function getAnyOpenConnection( $i, $flags = 0 ) {
 587                 $autocommit = ( ( $flags & self::CONN_TRX_AUTOCOMMIT ) == self::CONN_TRX_AUTOCOMMIT );
 588                 foreach ( $this->conns as $connsByServer ) {
 589                         if ( !isset( $connsByServer[$i] ) ) {
 590                                 continue;
 591                         }
 592
 593                         foreach ( $connsByServer[$i] as $conn ) {
 594                                 if ( !$autocommit || $conn->getLBInfo( 'autoCommitOnly' ) ) {
 595                                         return $conn;
 596                                 }
 597                         }
 598                 }
 599
 600                 return false;
 601         }
 602
 603         /**
 604          * Wait for a given replica DB to catch up to the master pos stored in $this
 605          * @param int $index Server index
 606          * @param bool $open Check the server even if a new connection has to be made
 607          * @param int|null $timeout Max seconds to wait; default is "waitTimeout" given to __construct()
 608          * @return bool
 609          */
 610         protected function doWait( $index, $open = false, $timeout = null ) {
 611                 $timeout = max( 1, intval( $timeout ?: $this->waitTimeout ) );
 612
 613                 // Check if we already know that the DB has reached this point
 614                 $server = $this->getServerName( $index );
 615                 $key = $this->srvCache->makeGlobalKey( __CLASS__, 'last-known-pos', $server, 'v1' );
 616                 /** @var DBMasterPos $knownReachedPos */
 617                 $knownReachedPos = $this->srvCache->get( $key );
 618                 if (
 619                         $knownReachedPos instanceof DBMasterPos &&
 620                         $knownReachedPos->hasReached( $this->waitForPos )
 621                 ) {
 622                         $this->replLogger->debug(
 623                                 __METHOD__ .
 624                                 ': replica DB {dbserver} known to be caught up (pos >= $knownReachedPos).',
 625                                 [ 'dbserver' => $server ]
 626                         );
 627                         return true;
 628                 }
 629
 630                 // Find a connection to wait on, creating one if needed and allowed
 631                 $close = false; // close the connection afterwards
 632                 $conn = $this->getAnyOpenConnection( $index );
 633                 if ( !$conn ) {
 634                         if ( !$open ) {
 635                                 $this->replLogger->debug(
 636                                         __METHOD__ . ': no connection open for {dbserver}',
 637                                         [ 'dbserver' => $server ]
 638                                 );
 639
 640                                 return false;
 641                         } else {
 642                                 $conn = $this->openConnection( $index, self::DOMAIN_ANY );
 643                                 if ( !$conn ) {
 644                                         $this->replLogger->warning(
 645                                                 __METHOD__ . ': failed to connect to {dbserver}',
 646                                                 [ 'dbserver' => $server ]
 647                                         );
 648
 649                                         return false;
 650                                 }
 651                                 // Avoid connection spam in waitForAll() when connections
 652                                 // are made just for the sake of doing this lag check.
 653                                 $close = true;
 654                         }
 655                 }
 656
 657                 $this->replLogger->info(
 658                         __METHOD__ .
 659                         ': waiting for replica DB {dbserver} to catch up...',
 660                         [ 'dbserver' => $server ]
 661                 );
 662
 663                 $result = $conn->masterPosWait( $this->waitForPos, $timeout );
 664
 665                 if ( $result === null ) {
 666                         $this->replLogger->warning(
 667                                 __METHOD__ . ': Errored out waiting on {host} pos {pos}',
 668                                 [
 669                                         'host' => $server,
 670                                         'pos' => $this->waitForPos,
 671                                         'trace' => ( new RuntimeException() )->getTraceAsString()
 672                                 ]
 673                         );
 674                         $ok = false;
 675                 } elseif ( $result == -1 ) {
 676                         $this->replLogger->warning(
 677                                 __METHOD__ . ': Timed out waiting on {host} pos {pos}',
 678                                 [
 679                                         'host' => $server,
 680                                         'pos' => $this->waitForPos,
 681                                         'trace' => ( new RuntimeException() )->getTraceAsString()
 682                                 ]
 683                         );
 684                         $ok = false;
 685                 } else {
 686                         $this->replLogger->debug( __METHOD__ . ": done waiting" );
 687                         $ok = true;
 688                         // Remember that the DB reached this point
 689                         $this->srvCache->set( $key, $this->waitForPos, BagOStuff::TTL_DAY );
 690                 }
 691
 692                 if ( $close ) {
 693                         $this->closeConnection( $conn );
 694                 }
 695
 696                 return $ok;
 697         }
 698
 699         public function getConnection( $i, $groups = [], $domain = false, $flags = 0 ) {
 700                 if ( $i === null || $i === false ) {
 701                         throw new InvalidArgumentException( 'Attempt to call ' . __METHOD__ .
 702                                 ' with invalid server index' );
 703                 }
 704
 705                 if ( $this->localDomain->equals( $domain ) || $domain === $this->localDomainIdAlias ) {
 706                         $domain = false; // local connection requested
 707                 }
 708
 709                 if ( ( $flags & self::CONN_TRX_AUTOCOMMIT ) === self::CONN_TRX_AUTOCOMMIT ) {
 710                         // Assuming all servers are of the same type (or similar), which is overwhelmingly
 711                         // the case, use the master server information to get the attributes. The information
 712                         // for $i cannot be used since it might be DB_REPLICA, which might require connection
 713                         // attempts in order to be resolved into a real server index.
 714                         $attributes = $this->getServerAttributes( $this->getWriterIndex() );
 715                         if ( $attributes[Database::ATTR_DB_LEVEL_LOCKING] ) {
 716                                 // Callers sometimes want to (a) escape REPEATABLE-READ stateness without locking
 717                                 // rows (e.g. FOR UPDATE) or (b) make small commits during a larger transactions
 718                                 // to reduce lock contention. None of these apply for sqlite and using separate
 719                                 // connections just causes self-deadlocks.
 720                                 $flags &= ~self::CONN_TRX_AUTOCOMMIT;
 721                                 $this->connLogger->info( __METHOD__ .
 722                                         ': ignoring CONN_TRX_AUTOCOMMIT to avoid deadlocks.' );
 723                         }
 724                 }
 725
 726                 // Check one "group" per default: the generic pool
 727                 $defaultGroups = $this->defaultGroup ? [ $this->defaultGroup ] : [ false ];
 728
 729                 $groups = ( $groups === false || $groups === [] )
 730                         ? $defaultGroups
 731                         : (array)$groups;
 732
 733                 $masterOnly = ( $i == self::DB_MASTER || $i == $this->getWriterIndex() );
 734                 $oldConnsOpened = $this->connsOpened; // connections open now
 735
 736                 if ( $i == self::DB_MASTER ) {
 737                         $i = $this->getWriterIndex();
 738                 } elseif ( $i == self::DB_REPLICA ) {
 739                         # Try to find an available server in any the query groups (in order)
 740                         foreach ( $groups as $group ) {
 741                                 $groupIndex = $this->getReaderIndex( $group, $domain );
 742                                 if ( $groupIndex !== false ) {
 743                                         $i = $groupIndex;
 744                                         break;
 745                                 }
 746                         }
 747                 }
 748
 749                 # Operation-based index
 750                 if ( $i == self::DB_REPLICA ) {
 751                         $this->lastError = 'Unknown error'; // reset error string
 752                         # Try the general server pool if $groups are unavailable.
 753                         $i = ( $groups === [ false ] )
 754                                 ? false // don't bother with this if that is what was tried above
 755                                 : $this->getReaderIndex( false, $domain );
 756                         # Couldn't find a working server in getReaderIndex()?
 757                         if ( $i === false ) {
 758                                 $this->lastError = 'No working replica DB server: ' . $this->lastError;
 759                                 // Throw an exception
 760                                 $this->reportConnectionError();
 761                                 return null; // not reached
 762                         }
 763                 }
 764
 765                 # Now we have an explicit index into the servers array
 766                 $conn = $this->openConnection( $i, $domain, $flags );
 767                 if ( !$conn ) {
 768                         // Throw an exception
 769                         $this->reportConnectionError();
 770                         return null; // not reached
 771                 }
 772
 773                 # Profile any new connections that happen
 774                 if ( $this->connsOpened > $oldConnsOpened ) {
 775                         $host = $conn->getServer();
 776                         $dbname = $conn->getDBname();
 777                         $this->trxProfiler->recordConnection( $host, $dbname, $masterOnly );
 778                 }
 779
 780                 if ( $masterOnly ) {
 781                         # Make master-requested DB handles inherit any read-only mode setting
 782                         $conn->setLBInfo( 'readOnlyReason', $this->getReadOnlyReason( $domain, $conn ) );
 783                 }
 784
 785                 return $conn;
 786         }
 787
 788         public function reuseConnection( IDatabase $conn ) {
 789                 $serverIndex = $conn->getLBInfo( 'serverIndex' );
 790                 $refCount = $conn->getLBInfo( 'foreignPoolRefCount' );
 791                 if ( $serverIndex === null || $refCount === null ) {
 792                         /**
 793                          * This can happen in code like:
 794                          *   foreach ( $dbs as $db ) {
 795                          *     $conn = $lb->getConnection( $lb::DB_REPLICA, [], $db );
 796                          *     ...
 797                          *     $lb->reuseConnection( $conn );
 798                          *   }
 799                          * When a connection to the local DB is opened in this way, reuseConnection()
 800                          * should be ignored
 801                          */
 802                         return;
 803                 } elseif ( $conn instanceof DBConnRef ) {
 804                         // DBConnRef already handles calling reuseConnection() and only passes the live
 805                         // Database instance to this method. Any caller passing in a DBConnRef is broken.
 806                         $this->connLogger->error(
 807                                 __METHOD__ . ": got DBConnRef instance.\n" .
 808                                 ( new RuntimeException() )->getTraceAsString() );
 809
 810                         return;
 811                 }
 812
 813                 if ( $this->disabled ) {
 814                         return; // DBConnRef handle probably survived longer than the LoadBalancer
 815                 }
 816
 817                 if ( $conn->getLBInfo( 'autoCommitOnly' ) ) {
 818                         $connFreeKey = self::KEY_FOREIGN_FREE_NOROUND;
 819                         $connInUseKey = self::KEY_FOREIGN_INUSE_NOROUND;
 820                 } else {
 821                         $connFreeKey = self::KEY_FOREIGN_FREE;
 822                         $connInUseKey = self::KEY_FOREIGN_INUSE;
 823                 }
 824
 825                 $domain = $conn->getDomainID();
 826                 if ( !isset( $this->conns[$connInUseKey][$serverIndex][$domain] ) ) {
 827                         throw new InvalidArgumentException( __METHOD__ .
 828                                 ": connection $serverIndex/$domain not found; it may have already been freed." );
 829                 } elseif ( $this->conns[$connInUseKey][$serverIndex][$domain] !== $conn ) {
 830                         throw new InvalidArgumentException( __METHOD__ .
 831                                 ": connection $serverIndex/$domain mismatched; it may have already been freed." );
 832                 }
 833
 834                 $conn->setLBInfo( 'foreignPoolRefCount', --$refCount );
 835                 if ( $refCount <= 0 ) {
 836                         $this->conns[$connFreeKey][$serverIndex][$domain] = $conn;
 837                         unset( $this->conns[$connInUseKey][$serverIndex][$domain] );
 838                         if ( !$this->conns[$connInUseKey][$serverIndex] ) {
 839                                 unset( $this->conns[$connInUseKey][$serverIndex] ); // clean up
 840                         }
 841                         $this->connLogger->debug( __METHOD__ . ": freed connection $serverIndex/$domain" );
 842                 } else {
 843                         $this->connLogger->debug( __METHOD__ .
 844                                 ": reference count for $serverIndex/$domain reduced to $refCount" );
 845                 }
 846         }
 847
 848         public function getConnectionRef( $db, $groups = [], $domain = false, $flags = 0 ) {
 849                 $domain = $this->resolveDomainID( $domain );
 850
 851                 return new DBConnRef( $this, $this->getConnection( $db, $groups, $domain, $flags ) );
 852         }
 853
 854         public function getLazyConnectionRef( $db, $groups = [], $domain = false, $flags = 0 ) {
 855                 $domain = $this->resolveDomainID( $domain );
 856
 857                 return new DBConnRef( $this, [ $db, $groups, $domain, $flags ] );
 858         }
 859
 860         public function getMaintenanceConnectionRef( $db, $groups = [], $domain = false, $flags = 0 ) {
 861                 $domain = $this->resolveDomainID( $domain );
 862
 863                 return new MaintainableDBConnRef(
 864                         $this, $this->getConnection( $db, $groups, $domain, $flags ) );
 865         }
 866
 867         public function openConnection( $i, $domain = false, $flags = 0 ) {
 868                 if ( $this->localDomain->equals( $domain ) || $domain === $this->localDomainIdAlias ) {
 869                         $domain = false; // local connection requested
 870                 }
 871
 872                 if ( !$this->connectionAttempted && $this->chronologyCallback ) {
 873                         $this->connLogger->debug( __METHOD__ . ': calling initLB() before first connection.' );
 874                         // Load any "waitFor" positions before connecting so that doWait() is triggered
 875                         $this->connectionAttempted = true;
 876                         ( $this->chronologyCallback )( $this );
 877                 }
 878
 879                 // Check if an auto-commit connection is being requested. If so, it will not reuse the
 880                 // main set of DB connections but rather its own pool since:
 881                 // a) those are usually set to implicitly use transaction rounds via DBO_TRX
 882                 // b) those must support the use of explicit transaction rounds via beginMasterChanges()
 883                 $autoCommit = ( ( $flags & self::CONN_TRX_AUTOCOMMIT ) == self::CONN_TRX_AUTOCOMMIT );
 884
 885                 if ( $domain !== false ) {
 886                         // Connection is to a foreign domain
 887                         $conn = $this->openForeignConnection( $i, $domain, $flags );
 888                 } else {
 889                         // Connection is to the local domain
 890                         $conn = $this->openLocalConnection( $i, $flags );
 891                 }
 892
 893                 if ( $conn instanceof IDatabase && !$conn->isOpen() ) {
 894                         // Connection was made but later unrecoverably lost for some reason.
 895                         // Do not return a handle that will just throw exceptions on use,
 896                         // but let the calling code (e.g. getReaderIndex) try another server.
 897                         // See DatabaseMyslBase::ping() for how this can happen.
 898                         $this->errorConnection = $conn;
 899                         $conn = false;
 900                 }
 901
 902                 if ( $autoCommit && $conn instanceof IDatabase ) {
 903                         if ( $conn->trxLevel() ) { // sanity
 904                                 throw new DBUnexpectedError(
 905                                         $conn,
 906                                         __METHOD__ . ': CONN_TRX_AUTOCOMMIT handle has a transaction.'
 907                                 );
 908                         }
 909
 910                         $conn->clearFlag( $conn::DBO_TRX ); // auto-commit mode
 911                 }
 912
 913                 return $conn;
 914         }
 915
 916         /**
 917          * Open a connection to a local DB, or return one if it is already open.
 918          *
 919          * On error, returns false, and the connection which caused the
 920          * error will be available via $this->errorConnection.
 921          *
 922          * @note If disable() was called on this LoadBalancer, this method will throw a DBAccessError.
 923          *
 924          * @param int $i Server index
 925          * @param int $flags Class CONN_* constant bitfield
 926          * @return Database
 927          */
 928         private function openLocalConnection( $i, $flags = 0 ) {
 929                 $autoCommit = ( ( $flags & self::CONN_TRX_AUTOCOMMIT ) == self::CONN_TRX_AUTOCOMMIT );
 930
 931                 $connKey = $autoCommit ? self::KEY_LOCAL_NOROUND : self::KEY_LOCAL;
 932                 if ( isset( $this->conns[$connKey][$i][0] ) ) {
 933                         $conn = $this->conns[$connKey][$i][0];
 934                 } else {
 935                         if ( !isset( $this->servers[$i] ) || !is_array( $this->servers[$i] ) ) {
 936                                 throw new InvalidArgumentException( "No server with index '$i'." );
 937                         }
 938                         // Open a new connection
 939                         $server = $this->servers[$i];
 940                         $server['serverIndex'] = $i;
 941                         $server['autoCommitOnly'] = $autoCommit;
 942                         $conn = $this->reallyOpenConnection( $server, $this->localDomain );
 943                         $host = $this->getServerName( $i );
 944                         if ( $conn->isOpen() ) {
 945                                 $this->connLogger->debug(
 946                                         __METHOD__ . ": connected to database $i at '$host'." );
 947                                 $this->conns[$connKey][$i][0] = $conn;
 948                         } else {
 949                                 $this->connLogger->warning(
 950                                         __METHOD__ . ": failed to connect to database $i at '$host'." );
 951                                 $this->errorConnection = $conn;
 952                                 $conn = false;
 953                         }
 954                 }
 955
 956                 // Final sanity check to make sure the right domain is selected
 957                 if (
 958                         $conn instanceof IDatabase &&
 959                         !$this->localDomain->isCompatible( $conn->getDomainID() )
 960                 ) {
 961                         throw new UnexpectedValueException(
 962                                 "Got connection to '{$conn->getDomainID()}', " .
 963                                 "but expected local domain ('{$this->localDomain}')." );
 964                 }
 965
 966                 return $conn;
 967         }
 968
 969         /**
 970          * Open a connection to a foreign DB, or return one if it is already open.
 971          *
 972          * Increments a reference count on the returned connection which locks the
 973          * connection to the requested domain. This reference count can be
 974          * decremented by calling reuseConnection().
 975          *
 976          * If a connection is open to the appropriate server already, but with the wrong
 977          * database, it will be switched to the right database and returned, as long as
 978          * it has been freed first with reuseConnection().
 979          *
 980          * On error, returns false, and the connection which caused the
 981          * error will be available via $this->errorConnection.
 982          *
 983          * @note If disable() was called on this LoadBalancer, this method will throw a DBAccessError.
 984          *
 985          * @param int $i Server index
 986          * @param string $domain Domain ID to open
 987          * @param int $flags Class CONN_* constant bitfield
 988          * @return Database|bool Returns false on connection error
 989          * @throws DBError When database selection fails
 990          */
 991         private function openForeignConnection( $i, $domain, $flags = 0 ) {
 992                 $domainInstance = DatabaseDomain::newFromId( $domain );
 993                 $autoCommit = ( ( $flags & self::CONN_TRX_AUTOCOMMIT ) == self::CONN_TRX_AUTOCOMMIT );
 994
 995                 if ( $autoCommit ) {
 996                         $connFreeKey = self::KEY_FOREIGN_FREE_NOROUND;
 997                         $connInUseKey = self::KEY_FOREIGN_INUSE_NOROUND;
 998                 } else {
 999                         $connFreeKey = self::KEY_FOREIGN_FREE;
1000                         $connInUseKey = self::KEY_FOREIGN_INUSE;
1001                 }
1002
1003                 /** @var Database $conn */
1004                 $conn = null;
1005
1006                 if ( isset( $this->conns[$connInUseKey][$i][$domain] ) ) {
1007                         // Reuse an in-use connection for the same domain
1008                         $conn = $this->conns[$connInUseKey][$i][$domain];
1009                         $this->connLogger->debug( __METHOD__ . ": reusing connection $i/$domain" );
1010                 } elseif ( isset( $this->conns[$connFreeKey][$i][$domain] ) ) {
1011                         // Reuse a free connection for the same domain
1012                         $conn = $this->conns[$connFreeKey][$i][$domain];
1013                         unset( $this->conns[$connFreeKey][$i][$domain] );
1014                         $this->conns[$connInUseKey][$i][$domain] = $conn;
1015                         $this->connLogger->debug( __METHOD__ . ": reusing free connection $i/$domain" );
1016                 } elseif ( !empty( $this->conns[$connFreeKey][$i] ) ) {
1017                         // Reuse a free connection from another domain if possible
1018                         foreach ( $this->conns[$connFreeKey][$i] as $oldDomain => $conn ) {
1019                                 if ( $domainInstance->getDatabase() !== null ) {
1020                                         // Check if changing the database will require a new connection.
1021                                         // In that case, leave the connection handle alone and keep looking.
1022                                         // This prevents connections from being closed mid-transaction and can
1023                                         // also avoid overhead if the same database will later be requested.
1024                                         if (
1025                                                 $conn->databasesAreIndependent() &&
1026                                                 $conn->getDBname() !== $domainInstance->getDatabase()
1027                                         ) {
1028                                                 continue;
1029                                         }
1030                                         // Select the new database, schema, and prefix
1031                                         $conn->selectDomain( $domainInstance );
1032                                 } else {
1033                                         // Stay on the current database, but update the schema/prefix
1034                                         $conn->dbSchema( $domainInstance->getSchema() );
1035                                         $conn->tablePrefix( $domainInstance->getTablePrefix() );
1036                                 }
1037                                 unset( $this->conns[$connFreeKey][$i][$oldDomain] );
1038                                 // Note that if $domain is an empty string, getDomainID() might not match it
1039                                 $this->conns[$connInUseKey][$i][$conn->getDomainId()] = $conn;
1040                                 $this->connLogger->debug( __METHOD__ .
1041                                         ": reusing free connection from $oldDomain for $domain" );
1042                                 break;
1043                         }
1044                 }
1045
1046                 if ( !$conn ) {
1047                         if ( !isset( $this->servers[$i] ) || !is_array( $this->servers[$i] ) ) {
1048                                 throw new InvalidArgumentException( "No server with index '$i'." );
1049                         }
1050                         // Open a new connection
1051                         $server = $this->servers[$i];
1052                         $server['serverIndex'] = $i;
1053                         $server['foreignPoolRefCount'] = 0;
1054                         $server['foreign'] = true;
1055                         $server['autoCommitOnly'] = $autoCommit;
1056                         $conn = $this->reallyOpenConnection( $server, $domainInstance );
1057                         if ( !$conn->isOpen() ) {
1058                                 $this->connLogger->warning( __METHOD__ . ": connection error for $i/$domain" );
1059                                 $this->errorConnection = $conn;
1060                                 $conn = false;
1061                         } else {
1062                                 // Note that if $domain is an empty string, getDomainID() might not match it
1063                                 $this->conns[$connInUseKey][$i][$conn->getDomainID()] = $conn;
1064                                 $this->connLogger->debug( __METHOD__ . ": opened new connection for $i/$domain" );
1065                         }
1066                 }
1067
1068                 if ( $conn instanceof IDatabase ) {
1069                         // Final sanity check to make sure the right domain is selected
1070                         if ( !$domainInstance->isCompatible( $conn->getDomainID() ) ) {
1071                                 throw new UnexpectedValueException(
1072                                         "Got connection to '{$conn->getDomainID()}', but expected '$domain'." );
1073                         }
1074                         // Increment reference count
1075                         $refCount = $conn->getLBInfo( 'foreignPoolRefCount' );
1076                         $conn->setLBInfo( 'foreignPoolRefCount', $refCount + 1 );
1077                 }
1078
1079                 return $conn;
1080         }
1081
1082         public function getServerAttributes( $i ) {
1083                 return Database::attributesFromType(
1084                         $this->getServerType( $i ),
1085                         $this->servers[$i]['driver'] ?? null
1086                 );
1087         }
1088
1089         /**
1090          * Test if the specified index represents an open connection
1091          *
1092          * @param int $index Server index
1093          * @access private
1094          * @return bool
1095          */
1096         private function isOpen( $index ) {
1097                 if ( !is_int( $index ) ) {
1098                         return false;
1099                 }
1100
1101                 return (bool)$this->getAnyOpenConnection( $index );
1102         }
1103
1104         /**
1105          * Open a new network connection to a server (uncached)
1106          *
1107          * Returns a Database object whether or not the connection was successful.
1108          *
1109          * @param array $server
1110          * @param DatabaseDomain $domain Domain the connection is for, possibly unspecified
1111          * @return Database
1112          * @throws DBAccessError
1113          * @throws InvalidArgumentException
1114          */
1115         protected function reallyOpenConnection( array $server, DatabaseDomain $domain ) {
1116                 if ( $this->disabled ) {
1117                         throw new DBAccessError();
1118                 }
1119
1120                 if ( $domain->getDatabase() === null ) {
1121                         // The database domain does not specify a DB name and some database systems require a
1122                         // valid DB specified on connection. The $server configuration array contains a default
1123                         // DB name to use for connections in such cases.
1124                         if ( $server['type'] === 'mysql' ) {
1125                                 // For MySQL, DATABASE and SCHEMA are synonyms, connections need not specify a DB,
1126                                 // and the DB name in $server might not exist due to legacy reasons (the default
1127                                 // domain used to ignore the local LB domain, even when mismatched).
1128                                 $server['dbname'] = null;
1129                         }
1130                 } else {
1131                         $server['dbname'] = $domain->getDatabase();
1132                 }
1133
1134                 if ( $domain->getSchema() !== null ) {
1135                         $server['schema'] = $domain->getSchema();
1136                 }
1137
1138                 // It is always possible to connect with any prefix, even the empty string
1139                 $server['tablePrefix'] = $domain->getTablePrefix();
1140
1141                 // Let the handle know what the cluster master is (e.g. "db1052")
1142                 $masterName = $this->getServerName( $this->getWriterIndex() );
1143                 $server['clusterMasterHost'] = $masterName;
1144
1145                 // Log when many connection are made on requests
1146                 if ( ++$this->connsOpened >= self::CONN_HELD_WARN_THRESHOLD ) {
1147                         $this->perfLogger->warning( __METHOD__ . ": " .
1148                                 "{$this->connsOpened}+ connections made (master=$masterName)" );
1149                 }
1150
1151                 $server['srvCache'] = $this->srvCache;
1152                 // Set loggers and profilers
1153                 $server['connLogger'] = $this->connLogger;
1154                 $server['queryLogger'] = $this->queryLogger;
1155                 $server['errorLogger'] = $this->errorLogger;
1156                 $server['deprecationLogger'] = $this->deprecationLogger;
1157                 $server['profiler'] = $this->profiler;
1158                 $server['trxProfiler'] = $this->trxProfiler;
1159                 // Use the same agent and PHP mode for all DB handles
1160                 $server['cliMode'] = $this->cliMode;
1161                 $server['agent'] = $this->agent;
1162                 // Use DBO_DEFAULT flags by default for LoadBalancer managed databases. Assume that the
1163                 // application calls LoadBalancer::commitMasterChanges() before the PHP script completes.
1164                 $server['flags'] = $server['flags'] ?? IDatabase::DBO_DEFAULT;
1165
1166                 // Create a live connection object
1167                 try {
1168                         $db = Database::factory( $server['type'], $server );
1169                 } catch ( DBConnectionError $e ) {
1170                         // FIXME: This is probably the ugliest thing I have ever done to
1171                         // PHP. I'm half-expecting it to segfault, just out of disgust. -- TS
1172                         $db = $e->db;
1173                 }
1174
1175                 $db->setLBInfo( $server );
1176                 $db->setLazyMasterHandle(
1177                         $this->getLazyConnectionRef( self::DB_MASTER, [], $db->getDomainID() )
1178                 );
1179                 $db->setTableAliases( $this->tableAliases );
1180                 $db->setIndexAliases( $this->indexAliases );
1181
1182                 if ( $server['serverIndex'] === $this->getWriterIndex() ) {
1183                         if ( $this->trxRoundId !== false ) {
1184                                 $this->applyTransactionRoundFlags( $db );
1185                         }
1186                         foreach ( $this->trxRecurringCallbacks as $name => $callback ) {
1187                                 $db->setTransactionListener( $name, $callback );
1188                         }
1189                 }
1190
1191                 return $db;
1192         }
1193
1194         /**
1195          * @throws DBConnectionError
1196          */
1197         private function reportConnectionError() {
1198                 $conn = $this->errorConnection; // the connection which caused the error
1199                 $context = [
1200                         'method' => __METHOD__,
1201                         'last_error' => $this->lastError,
1202                 ];
1203
1204                 if ( $conn instanceof IDatabase ) {
1205                         $context['db_server'] = $conn->getServer();
1206                         $this->connLogger->warning(
1207                                 __METHOD__ . ": connection error: {last_error} ({db_server})",
1208                                 $context
1209                         );
1210
1211                         throw new DBConnectionError( $conn, "{$this->lastError} ({$context['db_server']})" );
1212                 } else {
1213                         // No last connection, probably due to all servers being too busy
1214                         $this->connLogger->error(
1215                                 __METHOD__ .
1216                                 ": LB failure with no last connection. Connection error: {last_error}",
1217                                 $context
1218                         );
1219
1220                         // If all servers were busy, "lastError" will contain something sensible
1221                         throw new DBConnectionError( null, $this->lastError );
1222                 }
1223         }
1224
1225         public function getWriterIndex() {
1226                 return 0;
1227         }
1228
1229         public function haveIndex( $i ) {
1230                 return array_key_exists( $i, $this->servers );
1231         }
1232
1233         public function isNonZeroLoad( $i ) {
1234                 return array_key_exists( $i, $this->servers ) && $this->loads[$i] != 0;
1235         }
1236
1237         public function getServerCount() {
1238                 return count( $this->servers );
1239         }
1240
1241         public function getServerName( $i ) {
1242                 if ( isset( $this->servers[$i]['hostName'] ) ) {
1243                         $name = $this->servers[$i]['hostName'];
1244                 } elseif ( isset( $this->servers[$i]['host'] ) ) {
1245                         $name = $this->servers[$i]['host'];
1246                 } else {
1247                         $name = '';
1248                 }
1249
1250                 return ( $name != '' ) ? $name : 'localhost';
1251         }
1252
1253         public function getServerInfo( $i ) {
1254                 if ( isset( $this->servers[$i] ) ) {
1255                         return $this->servers[$i];
1256                 } else {
1257                         return false;
1258                 }
1259         }
1260
1261         public function getServerType( $i ) {
1262                 return $this->servers[$i]['type'] ?? 'unknown';
1263         }
1264
1265         public function getMasterPos() {
1266                 # If this entire request was served from a replica DB without opening a connection to the
1267                 # master (however unlikely that may be), then we can fetch the position from the replica DB.
1268                 $masterConn = $this->getAnyOpenConnection( $this->getWriterIndex() );
1269                 if ( !$masterConn ) {
1270                         $serverCount = count( $this->servers );
1271                         for ( $i = 1; $i < $serverCount; $i++ ) {
1272                                 $conn = $this->getAnyOpenConnection( $i );
1273                                 if ( $conn ) {
1274                                         return $conn->getReplicaPos();
1275                                 }
1276                         }
1277                 } else {
1278                         return $masterConn->getMasterPos();
1279                 }
1280
1281                 return false;
1282         }
1283
1284         public function disable() {
1285                 $this->closeAll();
1286                 $this->disabled = true;
1287         }
1288
1289         public function closeAll() {
1290                 $fname = __METHOD__;
1291                 $this->forEachOpenConnection( function ( IDatabase $conn ) use ( $fname ) {
1292                         $host = $conn->getServer();
1293                         $this->connLogger->debug(
1294                                 $fname . ": closing connection to database '$host'." );
1295                         $conn->close();
1296                 } );
1297
1298                 $this->conns = [
1299                         self::KEY_LOCAL => [],
1300                         self::KEY_FOREIGN_INUSE => [],
1301                         self::KEY_FOREIGN_FREE => [],
1302                         self::KEY_LOCAL_NOROUND => [],
1303                         self::KEY_FOREIGN_INUSE_NOROUND => [],
1304                         self::KEY_FOREIGN_FREE_NOROUND => []
1305                 ];
1306                 $this->connsOpened = 0;
1307         }
1308
1309         public function closeConnection( IDatabase $conn ) {
1310                 $serverIndex = $conn->getLBInfo( 'serverIndex' );
1311                 foreach ( $this->conns as $type => $connsByServer ) {
1312                         if ( !isset( $connsByServer[$serverIndex] ) ) {
1313                                 continue;
1314                         }
1315
1316                         foreach ( $connsByServer[$serverIndex] as $i => $trackedConn ) {
1317                                 if ( $conn === $trackedConn ) {
1318                                         $host = $this->getServerName( $i );
1319                                         $this->connLogger->debug(
1320                                                 __METHOD__ . ": closing connection to database $i at '$host'." );
1321                                         unset( $this->conns[$type][$serverIndex][$i] );
1322                                         --$this->connsOpened;
1323                                         break 2;
1324                                 }
1325                         }
1326                 }
1327
1328                 $conn->close();
1329         }
1330
1331         public function commitAll( $fname = __METHOD__ ) {
1332                 $this->commitMasterChanges( $fname );
1333                 $this->flushMasterSnapshots( $fname );
1334                 $this->flushReplicaSnapshots( $fname );
1335         }
1336
1337         public function finalizeMasterChanges() {
1338                 $this->assertTransactionRoundStage( [ self::ROUND_CURSORY, self::ROUND_FINALIZED ] );
1339
1340                 $this->trxRoundStage = self::ROUND_ERROR; // "failed" until proven otherwise
1341                 // Loop until callbacks stop adding callbacks on other connections
1342                 $total = 0;
1343                 do {
1344                         $count = 0; // callbacks execution attempts
1345                         $this->forEachOpenMasterConnection( function ( Database $conn ) use ( &$count ) {
1346                                 // Run any pre-commit callbacks while leaving the post-commit ones suppressed.
1347                                 // Any error should cause all (peer) transactions to be rolled back together.
1348                                 $count += $conn->runOnTransactionPreCommitCallbacks();
1349                         } );
1350                         $total += $count;
1351                 } while ( $count > 0 );
1352                 // Defer post-commit callbacks until after COMMIT/ROLLBACK happens on all handles
1353                 $this->forEachOpenMasterConnection( function ( Database $conn ) {
1354                         $conn->setTrxEndCallbackSuppression( true );
1355                 } );
1356                 $this->trxRoundStage = self::ROUND_FINALIZED;
1357
1358                 return $total;
1359         }
1360
1361         public function approveMasterChanges( array $options ) {
1362                 $this->assertTransactionRoundStage( self::ROUND_FINALIZED );
1363
1364                 $limit = $options['maxWriteDuration'] ?? 0;
1365
1366                 $this->trxRoundStage = self::ROUND_ERROR; // "failed" until proven otherwise
1367                 $this->forEachOpenMasterConnection( function ( IDatabase $conn ) use ( $limit ) {
1368                         // If atomic sections or explicit transactions are still open, some caller must have
1369                         // caught an exception but failed to properly rollback any changes. Detect that and
1370                         // throw and error (causing rollback).
1371                         $conn->assertNoOpenTransactions();
1372                         // Assert that the time to replicate the transaction will be sane.
1373                         // If this fails, then all DB transactions will be rollback back together.
1374                         $time = $conn->pendingWriteQueryDuration( $conn::ESTIMATE_DB_APPLY );
1375                         if ( $limit > 0 && $time > $limit ) {
1376                                 throw new DBTransactionSizeError(
1377                                         $conn,
1378                                         "Transaction spent $time second(s) in writes, exceeding the limit of $limit.",
1379                                         [ $time, $limit ]
1380                                 );
1381                         }
1382                         // If a connection sits idle while slow queries execute on another, that connection
1383                         // may end up dropped before the commit round is reached. Ping servers to detect this.
1384                         if ( $conn->writesOrCallbacksPending() && !$conn->ping() ) {
1385                                 throw new DBTransactionError(
1386                                         $conn,
1387                                         "A connection to the {$conn->getDBname()} database was lost before commit."
1388                                 );
1389                         }
1390                 } );
1391                 $this->trxRoundStage = self::ROUND_APPROVED;
1392         }
1393
1394         public function beginMasterChanges( $fname = __METHOD__ ) {
1395                 if ( $this->trxRoundId !== false ) {
1396                         throw new DBTransactionError(
1397                                 null,
1398                                 "$fname: Transaction round '{$this->trxRoundId}' already started."
1399                         );
1400                 }
1401                 $this->assertTransactionRoundStage( self::ROUND_CURSORY );
1402
1403                 // Clear any empty transactions (no writes/callbacks) from the implicit round
1404                 $this->flushMasterSnapshots( $fname );
1405
1406                 $this->trxRoundId = $fname;
1407                 $this->trxRoundStage = self::ROUND_ERROR; // "failed" until proven otherwise
1408                 // Mark applicable handles as participating in this explicit transaction round.
1409                 // For each of these handles, any writes and callbacks will be tied to a single
1410                 // transaction. The (peer) handles will reject begin()/commit() calls unless they
1411                 // are part of an en masse commit or an en masse rollback.
1412                 $this->forEachOpenMasterConnection( function ( Database $conn ) {
1413                         $this->applyTransactionRoundFlags( $conn );
1414                 } );
1415                 $this->trxRoundStage = self::ROUND_CURSORY;
1416         }
1417
1418         public function commitMasterChanges( $fname = __METHOD__ ) {
1419                 $this->assertTransactionRoundStage( self::ROUND_APPROVED );
1420
1421                 $failures = [];
1422
1423                 /** @noinspection PhpUnusedLocalVariableInspection */
1424                 $scope = $this->getScopedPHPBehaviorForCommit(); // try to ignore client aborts
1425
1426                 $restore = ( $this->trxRoundId !== false );
1427                 $this->trxRoundId = false;
1428                 $this->trxRoundStage = self::ROUND_ERROR; // "failed" until proven otherwise
1429                 // Commit any writes and clear any snapshots as well (callbacks require AUTOCOMMIT).
1430                 // Note that callbacks should already be suppressed due to finalizeMasterChanges().
1431                 $this->forEachOpenMasterConnection(
1432                         function ( IDatabase $conn ) use ( $fname, &$failures ) {
1433                                 try {
1434                                         $conn->commit( $fname, $conn::FLUSHING_ALL_PEERS );
1435                                 } catch ( DBError $e ) {
1436                                         ( $this->errorLogger )( $e );
1437                                         $failures[] = "{$conn->getServer()}: {$e->getMessage()}";
1438                                 }
1439                         }
1440                 );
1441                 if ( $failures ) {
1442                         throw new DBTransactionError(
1443                                 null,
1444                                 "$fname: Commit failed on server(s) " . implode( "\n", array_unique( $failures ) )
1445                         );
1446                 }
1447                 if ( $restore ) {
1448                         // Unmark handles as participating in this explicit transaction round
1449                         $this->forEachOpenMasterConnection( function ( Database $conn ) {
1450                                 $this->undoTransactionRoundFlags( $conn );
1451                         } );
1452                 }
1453                 $this->trxRoundStage = self::ROUND_COMMIT_CALLBACKS;
1454         }
1455
1456         public function runMasterTransactionIdleCallbacks() {
1457                 if ( $this->trxRoundStage === self::ROUND_COMMIT_CALLBACKS ) {
1458                         $type = IDatabase::TRIGGER_COMMIT;
1459                 } elseif ( $this->trxRoundStage === self::ROUND_ROLLBACK_CALLBACKS ) {
1460                         $type = IDatabase::TRIGGER_ROLLBACK;
1461                 } else {
1462                         throw new DBTransactionError(
1463                                 null,
1464                                 "Transaction should be in the callback stage (not '{$this->trxRoundStage}')"
1465                         );
1466                 }
1467
1468                 $oldStage = $this->trxRoundStage;
1469                 $this->trxRoundStage = self::ROUND_ERROR; // "failed" until proven otherwise
1470
1471                 // Now that the COMMIT/ROLLBACK step is over, enable post-commit callback runs
1472                 $this->forEachOpenMasterConnection( function ( Database $conn ) {
1473                         $conn->setTrxEndCallbackSuppression( false );
1474                 } );
1475
1476                 $e = null; // first exception
1477                 $fname = __METHOD__;
1478                 // Loop until callbacks stop adding callbacks on other connections
1479                 do {
1480                         // Run any pending callbacks for each connection...
1481                         $count = 0; // callback execution attempts
1482                         $this->forEachOpenMasterConnection(
1483                                 function ( Database $conn ) use ( $type, &$e, &$count ) {
1484                                         if ( $conn->trxLevel() ) {
1485                                                 return; // retry in the next iteration, after commit() is called
1486                                         }
1487                                         try {
1488                                                 $count += $conn->runOnTransactionIdleCallbacks( $type );
1489                                         } catch ( Exception $ex ) {
1490                                                 $e = $e ?: $ex;
1491                                         }
1492                                 }
1493                         );
1494                         // Clear out any active transactions left over from callbacks...
1495                         $this->forEachOpenMasterConnection( function ( Database $conn ) use ( &$e, $fname ) {
1496                                 if ( $conn->writesPending() ) {
1497                                         // A callback from another handle wrote to this one and DBO_TRX is set
1498                                         $this->queryLogger->warning( $fname . ": found writes pending." );
1499                                         $fnames = implode( ', ', $conn->pendingWriteAndCallbackCallers() );
1500                                         $this->queryLogger->warning(
1501                                                 $fname . ": found writes pending ($fnames).",
1502                                                 [
1503                                                         'db_server' => $conn->getServer(),
1504                                                         'db_name' => $conn->getDBname()
1505                                                 ]
1506                                         );
1507                                 } elseif ( $conn->trxLevel() ) {
1508                                         // A callback from another handle read from this one and DBO_TRX is set,
1509                                         // which can easily happen if there is only one DB (no replicas)
1510                                         $this->queryLogger->debug( $fname . ": found empty transaction." );
1511                                 }
1512                                 try {
1513                                         $conn->commit( $fname, $conn::FLUSHING_ALL_PEERS );
1514                                 } catch ( Exception $ex ) {
1515                                         $e = $e ?: $ex;
1516                                 }
1517                         } );
1518                 } while ( $count > 0 );
1519
1520                 $this->trxRoundStage = $oldStage;
1521
1522                 return $e;
1523         }
1524
1525         public function runMasterTransactionListenerCallbacks() {
1526                 if ( $this->trxRoundStage === self::ROUND_COMMIT_CALLBACKS ) {
1527                         $type = IDatabase::TRIGGER_COMMIT;
1528                 } elseif ( $this->trxRoundStage === self::ROUND_ROLLBACK_CALLBACKS ) {
1529                         $type = IDatabase::TRIGGER_ROLLBACK;
1530                 } else {
1531                         throw new DBTransactionError(
1532                                 null,
1533                                 "Transaction should be in the callback stage (not '{$this->trxRoundStage}')"
1534                         );
1535                 }
1536
1537                 $e = null;
1538
1539                 $this->trxRoundStage = self::ROUND_ERROR; // "failed" until proven otherwise
1540                 $this->forEachOpenMasterConnection( function ( Database $conn ) use ( $type, &$e ) {
1541                         try {
1542                                 $conn->runTransactionListenerCallbacks( $type );
1543                         } catch ( Exception $ex ) {
1544                                 $e = $e ?: $ex;
1545                         }
1546                 } );
1547                 $this->trxRoundStage = self::ROUND_CURSORY;
1548
1549                 return $e;
1550         }
1551
1552         public function rollbackMasterChanges( $fname = __METHOD__ ) {
1553                 $restore = ( $this->trxRoundId !== false );
1554                 $this->trxRoundId = false;
1555                 $this->trxRoundStage = self::ROUND_ERROR; // "failed" until proven otherwise
1556                 $this->forEachOpenMasterConnection( function ( IDatabase $conn ) use ( $fname ) {
1557                         $conn->rollback( $fname, $conn::FLUSHING_ALL_PEERS );
1558                 } );
1559                 if ( $restore ) {
1560                         // Unmark handles as participating in this explicit transaction round
1561                         $this->forEachOpenMasterConnection( function ( Database $conn ) {
1562                                 $this->undoTransactionRoundFlags( $conn );
1563                         } );
1564                 }
1565                 $this->trxRoundStage = self::ROUND_ROLLBACK_CALLBACKS;
1566         }
1567
1568         /**
1569          * @param string|string[] $stage
1570          */
1571         private function assertTransactionRoundStage( $stage ) {
1572                 $stages = (array)$stage;
1573
1574                 if ( !in_array( $this->trxRoundStage, $stages, true ) ) {
1575                         $stageList = implode(
1576                                 '/',
1577                                 array_map( function ( $v ) {
1578                                         return "'$v'";
1579                                 }, $stages )
1580                         );
1581                         throw new DBTransactionError(
1582                                 null,
1583                                 "Transaction round stage must be $stageList (not '{$this->trxRoundStage}')"
1584                         );
1585                 }
1586         }
1587
1588         /**
1589          * Make all DB servers with DBO_DEFAULT/DBO_TRX set join the transaction round
1590          *
1591          * Some servers may have neither flag enabled, meaning that they opt out of such
1592          * transaction rounds and remain in auto-commit mode. Such behavior might be desired
1593          * when a DB server is used for something like simple key/value storage.
1594          *
1595          * @param Database $conn
1596          */
1597         private function applyTransactionRoundFlags( Database $conn ) {
1598                 if ( $conn->getLBInfo( 'autoCommitOnly' ) ) {
1599                         return; // transaction rounds do not apply to these connections
1600                 }
1601
1602                 if ( $conn->getFlag( $conn::DBO_DEFAULT ) ) {
1603                         // DBO_TRX is controlled entirely by CLI mode presence with DBO_DEFAULT.
1604                         // Force DBO_TRX even in CLI mode since a commit round is expected soon.
1605                         $conn->setFlag( $conn::DBO_TRX, $conn::REMEMBER_PRIOR );
1606                 }
1607
1608                 if ( $conn->getFlag( $conn::DBO_TRX ) ) {
1609                         $conn->setLBInfo( 'trxRoundId', $this->trxRoundId );
1610                 }
1611         }
1612
1613         /**
1614          * @param Database $conn
1615          */
1616         private function undoTransactionRoundFlags( Database $conn ) {
1617                 if ( $conn->getLBInfo( 'autoCommitOnly' ) ) {
1618                         return; // transaction rounds do not apply to these connections
1619                 }
1620
1621                 if ( $conn->getFlag( $conn::DBO_TRX ) ) {
1622                         $conn->setLBInfo( 'trxRoundId', false );
1623                 }
1624
1625                 if ( $conn->getFlag( $conn::DBO_DEFAULT ) ) {
1626                         $conn->restoreFlags( $conn::RESTORE_PRIOR );
1627                 }
1628         }
1629
1630         public function flushReplicaSnapshots( $fname = __METHOD__ ) {
1631                 $this->forEachOpenReplicaConnection( function ( IDatabase $conn ) use ( $fname ) {
1632                         $conn->flushSnapshot( $fname );
1633                 } );
1634         }
1635
1636         public function flushMasterSnapshots( $fname = __METHOD__ ) {
1637                 $this->forEachOpenMasterConnection( function ( IDatabase $conn ) use ( $fname ) {
1638                         $conn->flushSnapshot( $fname );
1639                 } );
1640         }
1641
1642         /**
1643          * @return string
1644          * @since 1.32
1645          */
1646         public function getTransactionRoundStage() {
1647                 return $this->trxRoundStage;
1648         }
1649
1650         public function hasMasterConnection() {
1651                 return $this->isOpen( $this->getWriterIndex() );
1652         }
1653
1654         public function hasMasterChanges() {
1655                 $pending = 0;
1656                 $this->forEachOpenMasterConnection( function ( IDatabase $conn ) use ( &$pending ) {
1657                         $pending |= $conn->writesOrCallbacksPending();
1658                 } );
1659
1660                 return (bool)$pending;
1661         }
1662
1663         public function lastMasterChangeTimestamp() {
1664                 $lastTime = false;
1665                 $this->forEachOpenMasterConnection( function ( IDatabase $conn ) use ( &$lastTime ) {
1666                         $lastTime = max( $lastTime, $conn->lastDoneWrites() );
1667                 } );
1668
1669                 return $lastTime;
1670         }
1671
1672         public function hasOrMadeRecentMasterChanges( $age = null ) {
1673                 $age = ( $age === null ) ? $this->waitTimeout : $age;
1674
1675                 return ( $this->hasMasterChanges()
1676                         || $this->lastMasterChangeTimestamp() > microtime( true ) - $age );
1677         }
1678
1679         public function pendingMasterChangeCallers() {
1680                 $fnames = [];
1681                 $this->forEachOpenMasterConnection( function ( IDatabase $conn ) use ( &$fnames ) {
1682                         $fnames = array_merge( $fnames, $conn->pendingWriteCallers() );
1683                 } );
1684
1685                 return $fnames;
1686         }
1687
1688         public function getLaggedReplicaMode( $domain = false ) {
1689                 // No-op if there is only one DB (also avoids recursion)
1690                 if ( !$this->laggedReplicaMode && $this->getServerCount() > 1 ) {
1691                         try {
1692                                 // See if laggedReplicaMode gets set
1693                                 $conn = $this->getConnection( self::DB_REPLICA, false, $domain );
1694                                 $this->reuseConnection( $conn );
1695                         } catch ( DBConnectionError $e ) {
1696                                 // Avoid expensive re-connect attempts and failures
1697                                 $this->allReplicasDownMode = true;
1698                                 $this->laggedReplicaMode = true;
1699                         }
1700                 }
1701
1702                 return $this->laggedReplicaMode;
1703         }
1704
1705         public function laggedReplicaUsed() {
1706                 return $this->laggedReplicaMode;
1707         }
1708
1709         /**
1710          * @return bool
1711          * @since 1.27
1712          * @deprecated Since 1.28; use laggedReplicaUsed()
1713          */
1714         public function laggedSlaveUsed() {
1715                 return $this->laggedReplicaUsed();
1716         }
1717
1718         public function getReadOnlyReason( $domain = false, IDatabase $conn = null ) {
1719                 if ( $this->readOnlyReason !== false ) {
1720                         return $this->readOnlyReason;
1721                 } elseif ( $this->getLaggedReplicaMode( $domain ) ) {
1722                         if ( $this->allReplicasDownMode ) {
1723                                 return 'The database has been automatically locked ' .
1724                                         'until the replica database servers become available';
1725                         } else {
1726                                 return 'The database has been automatically locked ' .
1727                                         'while the replica database servers catch up to the master.';
1728                         }
1729                 } elseif ( $this->masterRunningReadOnly( $domain, $conn ) ) {
1730                         return 'The database master is running in read-only mode.';
1731                 }
1732
1733                 return false;
1734         }
1735
1736         /**
1737          * @param string $domain Domain ID, or false for the current domain
1738          * @param IDatabase|null $conn DB master connectionl used to avoid loops [optional]
1739          * @return bool
1740          */
1741         private function masterRunningReadOnly( $domain, IDatabase $conn = null ) {
1742                 $cache = $this->wanCache;
1743                 $masterServer = $this->getServerName( $this->getWriterIndex() );
1744
1745                 return (bool)$cache->getWithSetCallback(
1746                         $cache->makeGlobalKey( __CLASS__, 'server-read-only', $masterServer ),
1747                         self::TTL_CACHE_READONLY,
1748                         function () use ( $domain, $conn ) {
1749                                 $old = $this->trxProfiler->setSilenced( true );
1750                                 try {
1751                                         $dbw = $conn ?: $this->getConnection( self::DB_MASTER, [], $domain );
1752                                         $readOnly = (int)$dbw->serverIsReadOnly();
1753                                         if ( !$conn ) {
1754                                                 $this->reuseConnection( $dbw );
1755                                         }
1756                                 } catch ( DBError $e ) {
1757                                         $readOnly = 0;
1758                                 }
1759                                 $this->trxProfiler->setSilenced( $old );
1760                                 return $readOnly;
1761                         },
1762                         [ 'pcTTL' => $cache::TTL_PROC_LONG, 'busyValue' => 0 ]
1763                 );
1764         }
1765
1766         public function allowLagged( $mode = null ) {
1767                 if ( $mode === null ) {
1768                         return $this->allowLagged;
1769                 }
1770                 $this->allowLagged = $mode;
1771
1772                 return $this->allowLagged;
1773         }
1774
1775         public function pingAll() {
1776                 $success = true;
1777                 $this->forEachOpenConnection( function ( IDatabase $conn ) use ( &$success ) {
1778                         if ( !$conn->ping() ) {
1779                                 $success = false;
1780                         }
1781                 } );
1782
1783                 return $success;
1784         }
1785
1786         public function forEachOpenConnection( $callback, array $params = [] ) {
1787                 foreach ( $this->conns as $connsByServer ) {
1788                         foreach ( $connsByServer as $serverConns ) {
1789                                 foreach ( $serverConns as $conn ) {
1790                                         $callback( $conn, ...$params );
1791                                 }
1792                         }
1793                 }
1794         }
1795
1796         public function forEachOpenMasterConnection( $callback, array $params = [] ) {
1797                 $masterIndex = $this->getWriterIndex();
1798                 foreach ( $this->conns as $connsByServer ) {
1799                         if ( isset( $connsByServer[$masterIndex] ) ) {
1800                                 /** @var IDatabase $conn */
1801                                 foreach ( $connsByServer[$masterIndex] as $conn ) {
1802                                         $callback( $conn, ...$params );
1803                                 }
1804                         }
1805                 }
1806         }
1807
1808         public function forEachOpenReplicaConnection( $callback, array $params = [] ) {
1809                 foreach ( $this->conns as $connsByServer ) {
1810                         foreach ( $connsByServer as $i => $serverConns ) {
1811                                 if ( $i === $this->getWriterIndex() ) {
1812                                         continue; // skip master
1813                                 }
1814                                 foreach ( $serverConns as $conn ) {
1815                                         $callback( $conn, ...$params );
1816                                 }
1817                         }
1818                 }
1819         }
1820
1821         public function getMaxLag( $domain = false ) {
1822                 $maxLag = -1;
1823                 $host = '';
1824                 $maxIndex = 0;
1825
1826                 if ( $this->getServerCount() <= 1 ) {
1827                         return [ $host, $maxLag, $maxIndex ]; // no replication = no lag
1828                 }
1829
1830                 $lagTimes = $this->getLagTimes( $domain );
1831                 foreach ( $lagTimes as $i => $lag ) {
1832                         if ( $this->loads[$i] > 0 && $lag > $maxLag ) {
1833                                 $maxLag = $lag;
1834                                 $host = $this->servers[$i]['host'];
1835                                 $maxIndex = $i;
1836                         }
1837                 }
1838
1839                 return [ $host, $maxLag, $maxIndex ];
1840         }
1841
1842         public function getLagTimes( $domain = false ) {
1843                 if ( $this->getServerCount() <= 1 ) {
1844                         return [ $this->getWriterIndex() => 0 ]; // no replication = no lag
1845                 }
1846
1847                 $knownLagTimes = []; // map of (server index => 0 seconds)
1848                 $indexesWithLag = [];
1849                 foreach ( $this->servers as $i => $server ) {
1850                         if ( empty( $server['is static'] ) ) {
1851                                 $indexesWithLag[] = $i; // DB server might have replication lag
1852                         } else {
1853                                 $knownLagTimes[$i] = 0; // DB server is a non-replicating and read-only archive
1854                         }
1855                 }
1856
1857                 return $this->getLoadMonitor()->getLagTimes( $indexesWithLag, $domain ) + $knownLagTimes;
1858         }
1859
1860         public function safeGetLag( IDatabase $conn ) {
1861                 if ( $this->getServerCount() <= 1 ) {
1862                         return 0;
1863                 } else {
1864                         return $conn->getLag();
1865                 }
1866         }
1867
1868         /**
1869          * @param IDatabase $conn
1870          * @param DBMasterPos|bool $pos
1871          * @param int|null $timeout
1872          * @return bool
1873          */
1874         public function safeWaitForMasterPos( IDatabase $conn, $pos = false, $timeout = null ) {
1875                 $timeout = max( 1, $timeout ?: $this->waitTimeout );
1876
1877                 if ( $this->getServerCount() <= 1 || !$conn->getLBInfo( 'replica' ) ) {
1878                         return true; // server is not a replica DB
1879                 }
1880
1881                 if ( !$pos ) {
1882                         // Get the current master position, opening a connection if needed
1883                         $masterConn = $this->getAnyOpenConnection( $this->getWriterIndex() );
1884                         if ( $masterConn ) {
1885                                 $pos = $masterConn->getMasterPos();
1886                         } else {
1887                                 $masterConn = $this->openConnection( $this->getWriterIndex(), self::DOMAIN_ANY );
1888                                 $pos = $masterConn->getMasterPos();
1889                                 $this->closeConnection( $masterConn );
1890                         }
1891                 }
1892
1893                 if ( $pos instanceof DBMasterPos ) {
1894                         $result = $conn->masterPosWait( $pos, $timeout );
1895                         if ( $result == -1 || is_null( $result ) ) {
1896                                 $msg = __METHOD__ . ': timed out waiting on {host} pos {pos}';
1897                                 $this->replLogger->warning( $msg, [
1898                                         'host' => $conn->getServer(),
1899                                         'pos' => $pos,
1900                                         'trace' => ( new RuntimeException() )->getTraceAsString()
1901                                 ] );
1902                                 $ok = false;
1903                         } else {
1904                                 $this->replLogger->debug( __METHOD__ . ': done waiting' );
1905                                 $ok = true;
1906                         }
1907                 } else {
1908                         $ok = false; // something is misconfigured
1909                         $this->replLogger->error(
1910                                 __METHOD__ . ': could not get master pos for {host}',
1911                                 [
1912                                         'host' => $conn->getServer(),
1913                                         'trace' => ( new RuntimeException() )->getTraceAsString()
1914                                 ]
1915                         );
1916                 }
1917
1918                 return $ok;
1919         }
1920
1921         public function setTransactionListener( $name, callable $callback = null ) {
1922                 if ( $callback ) {
1923                         $this->trxRecurringCallbacks[$name] = $callback;
1924                 } else {
1925                         unset( $this->trxRecurringCallbacks[$name] );
1926                 }
1927                 $this->forEachOpenMasterConnection(
1928                         function ( IDatabase $conn ) use ( $name, $callback ) {
1929                                 $conn->setTransactionListener( $name, $callback );
1930                         }
1931                 );
1932         }
1933
1934         public function setTableAliases( array $aliases ) {
1935                 $this->tableAliases = $aliases;
1936         }
1937
1938         public function setIndexAliases( array $aliases ) {
1939                 $this->indexAliases = $aliases;
1940         }
1941
1942         public function setDomainPrefix( $prefix ) {
1943                 // Find connections to explicit foreign domains still marked as in-use...
1944                 $domainsInUse = [];
1945                 $this->forEachOpenConnection( function ( IDatabase $conn ) use ( &$domainsInUse ) {
1946                         // Once reuseConnection() is called on a handle, its reference count goes from 1 to 0.
1947                         // Until then, it is still in use by the caller (explicitly or via DBConnRef scope).
1948                         if ( $conn->getLBInfo( 'foreignPoolRefCount' ) > 0 ) {
1949                                 $domainsInUse[] = $conn->getDomainID();
1950                         }
1951                 } );
1952
1953                 // Do not switch connections to explicit foreign domains unless marked as safe
1954                 if ( $domainsInUse ) {
1955                         $domains = implode( ', ', $domainsInUse );
1956                         throw new DBUnexpectedError( null,
1957                                 "Foreign domain connections are still in use ($domains)." );
1958                 }
1959
1960                 $this->setLocalDomain( new DatabaseDomain(
1961                         $this->localDomain->getDatabase(),
1962                         $this->localDomain->getSchema(),
1963                         $prefix
1964                 ) );
1965
1966                 // Update the prefix for all local connections...
1967                 $this->forEachOpenConnection( function ( IDatabase $db ) use ( $prefix ) {
1968                         if ( !$db->getLBInfo( 'foreign' ) ) {
1969                                 $db->tablePrefix( $prefix );
1970                         }
1971                 } );
1972         }
1973
1974         /**
1975          * @param DatabaseDomain $domain
1976          */
1977         private function setLocalDomain( DatabaseDomain $domain ) {
1978                 $this->localDomain = $domain;
1979                 // In case a caller assumes that the domain ID is simply <db>-<prefix>, which is almost
1980                 // always true, gracefully handle the case when they fail to account for escaping.
1981                 if ( $this->localDomain->getTablePrefix() != '' ) {
1982                         $this->localDomainIdAlias =
1983                                 $this->localDomain->getDatabase() . '-' . $this->localDomain->getTablePrefix();
1984                 } else {
1985                         $this->localDomainIdAlias = $this->localDomain->getDatabase();
1986                 }
1987         }
1988
1989         /**
1990          * Make PHP ignore user aborts/disconnects until the returned
1991          * value leaves scope. This returns null and does nothing in CLI mode.
1992          *
1993          * @return ScopedCallback|null
1994          */
1995         final protected function getScopedPHPBehaviorForCommit() {
1996                 if ( PHP_SAPI != 'cli' ) { // https://bugs.php.net/bug.php?id=47540
1997                         $old = ignore_user_abort( true ); // avoid half-finished operations
1998                         return new ScopedCallback( function () use ( $old ) {
1999                                 ignore_user_abort( $old );
2000                         } );
2001                 }
2002
2003                 return null;
2004         }
2005
2006         function __destruct() {
2007                 // Avoid connection leaks for sanity
2008                 $this->disable();
2009         }
2010 }
2011
2012 /**
2013  * @deprecated since 1.29
2014  */
2015 class_alias( LoadBalancer::class, 'LoadBalancer' );