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 mixed 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 DB 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 $genericLoads;
  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 local DB domain instead of DatabaseDomain::getId() */
  86         private $localDomainIdAlias;
  87         /** @var int */
  88         private $maxLag;
  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 */
 107         private $genericReadIndex = -1;
 108         /** @var int[] The group replica DB indexes keyed by group */
 109         private $readIndexByGroup = [];
 110         /** @var bool|DBMasterPos Replication sync position or false if not set */
 111         private $waitForPos;
 112         /** @var bool Whether the generic reader fell back to a lagged replica DB */
 113         private $laggedReplicaMode = false;
 114         /** @var bool Whether the generic reader fell back to a lagged replica DB */
 115         private $allReplicasDownMode = false;
 116         /** @var string The last DB selection or connection error */
 117         private $lastError = 'Unknown error';
 118         /** @var string|bool Reason the LB is read-only or false if not */
 119         private $readOnlyReason = false;
 120         /** @var int Total connections opened */
 121         private $connsOpened = 0;
 122         /** @var bool */
 123         private $disabled = false;
 124         /** @var bool Whether any connection has been attempted yet */
 125         private $connectionAttempted = false;
 126
 127         /** @var int|null An integer ID of the managing LBFactory instance or null */
 128         private $ownerId;
 129         /** @var string|bool String if a requested DBO_TRX transaction round is active */
 130         private $trxRoundId = false;
 131         /** @var string Stage of the current transaction round in the transaction round life-cycle */
 132         private $trxRoundStage = self::ROUND_CURSORY;
 133
 134         /** @var string|null */
 135         private $defaultGroup = null;
 136
 137         /** @var int Warn when this many connection are held */
 138         const CONN_HELD_WARN_THRESHOLD = 10;
 139
 140         /** @var int Default 'maxLag' when unspecified */
 141         const MAX_LAG_DEFAULT = 6;
 142         /** @var int Default 'waitTimeout' when unspecified */
 143         const MAX_WAIT_DEFAULT = 10;
 144         /** @var int Seconds to cache master server read-only status */
 145         const TTL_CACHE_READONLY = 5;
 146
 147         const KEY_LOCAL = 'local';
 148         const KEY_FOREIGN_FREE = 'foreignFree';
 149         const KEY_FOREIGN_INUSE = 'foreignInUse';
 150
 151         const KEY_LOCAL_NOROUND = 'localAutoCommit';
 152         const KEY_FOREIGN_FREE_NOROUND = 'foreignFreeAutoCommit';
 153         const KEY_FOREIGN_INUSE_NOROUND = 'foreignInUseAutoCommit';
 154
 155         /** @var string Transaction round, explicit or implicit, has not finished writing */
 156         const ROUND_CURSORY = 'cursory';
 157         /** @var string Transaction round writes are complete and ready for pre-commit checks */
 158         const ROUND_FINALIZED = 'finalized';
 159         /** @var string Transaction round passed final pre-commit checks */
 160         const ROUND_APPROVED = 'approved';
 161         /** @var string Transaction round was committed and post-commit callbacks must be run */
 162         const ROUND_COMMIT_CALLBACKS = 'commit-callbacks';
 163         /** @var string Transaction round was rolled back and post-rollback callbacks must be run */
 164         const ROUND_ROLLBACK_CALLBACKS = 'rollback-callbacks';
 165         /** @var string Transaction round encountered an error */
 166         const ROUND_ERROR = 'error';
 167
 168         public function __construct( array $params ) {
 169                 if ( !isset( $params['servers'] ) ) {
 170                         throw new InvalidArgumentException( __CLASS__ . ': missing "servers" parameter' );
 171                 }
 172                 $this->servers = $params['servers'];
 173                 foreach ( $this->servers as $i => $server ) {
 174                         if ( $i == 0 ) {
 175                                 $this->servers[$i]['master'] = true;
 176                         } else {
 177                                 $this->servers[$i]['replica'] = true;
 178                         }
 179                 }
 180
 181                 $localDomain = isset( $params['localDomain'] )
 182                         ? DatabaseDomain::newFromId( $params['localDomain'] )
 183                         : DatabaseDomain::newUnspecified();
 184                 $this->setLocalDomain( $localDomain );
 185
 186                 $this->waitTimeout = $params['waitTimeout'] ?? self::MAX_WAIT_DEFAULT;
 187
 188                 $this->conns = [
 189                         // Connection were transaction rounds may be applied
 190                         self::KEY_LOCAL => [],
 191                         self::KEY_FOREIGN_INUSE => [],
 192                         self::KEY_FOREIGN_FREE => [],
 193                         // Auto-committing counterpart connections that ignore transaction rounds
 194                         self::KEY_LOCAL_NOROUND => [],
 195                         self::KEY_FOREIGN_INUSE_NOROUND => [],
 196                         self::KEY_FOREIGN_FREE_NOROUND => []
 197                 ];
 198                 $this->genericLoads = [];
 199                 $this->waitForPos = false;
 200                 $this->allowLagged = false;
 201
 202                 if ( isset( $params['readOnlyReason'] ) && is_string( $params['readOnlyReason'] ) ) {
 203                         $this->readOnlyReason = $params['readOnlyReason'];
 204                 }
 205
 206                 $this->maxLag = $params['maxLag'] ?? self::MAX_LAG_DEFAULT;
 207
 208                 $this->loadMonitorConfig = $params['loadMonitor'] ?? [ 'class' => 'LoadMonitorNull' ];
 209                 $this->loadMonitorConfig += [ 'lagWarnThreshold' => $this->maxLag ];
 210
 211                 foreach ( $params['servers'] as $i => $server ) {
 212                         $this->genericLoads[$i] = $server['load'];
 213                         if ( isset( $server['groupLoads'] ) ) {
 214                                 foreach ( $server['groupLoads'] as $group => $ratio ) {
 215                                         if ( !isset( $this->groupLoads[$group] ) ) {
 216                                                 $this->groupLoads[$group] = [];
 217                                         }
 218                                         $this->groupLoads[$group][$i] = $ratio;
 219                                 }
 220                         }
 221                 }
 222
 223                 $this->srvCache = $params['srvCache'] ?? new EmptyBagOStuff();
 224                 $this->wanCache = $params['wanCache'] ?? WANObjectCache::newEmpty();
 225                 $this->profiler = $params['profiler'] ?? null;
 226                 $this->trxProfiler = $params['trxProfiler'] ?? new TransactionProfiler();
 227
 228                 $this->errorLogger = $params['errorLogger'] ?? function ( Exception $e ) {
 229                         trigger_error( get_class( $e ) . ': ' . $e->getMessage(), E_USER_WARNING );
 230                 };
 231                 $this->deprecationLogger = $params['deprecationLogger'] ?? function ( $msg ) {
 232                         trigger_error( $msg, E_USER_DEPRECATED );
 233                 };
 234
 235                 foreach ( [ 'replLogger', 'connLogger', 'queryLogger', 'perfLogger' ] as $key ) {
 236                         $this->$key = $params[$key] ?? new NullLogger();
 237                 }
 238
 239                 $this->hostname = $params['hostname'] ?? ( gethostname() ?: 'unknown' );
 240                 $this->cliMode = $params['cliMode'] ?? ( PHP_SAPI === 'cli' || PHP_SAPI === 'phpdbg' );
 241                 $this->agent = $params['agent'] ?? '';
 242
 243                 if ( isset( $params['chronologyCallback'] ) ) {
 244                         $this->chronologyCallback = $params['chronologyCallback'];
 245                 }
 246
 247                 if ( isset( $params['roundStage'] ) ) {
 248                         if ( $params['roundStage'] === self::STAGE_POSTCOMMIT_CALLBACKS ) {
 249                                 $this->trxRoundStage = self::ROUND_COMMIT_CALLBACKS;
 250                         } elseif ( $params['roundStage'] === self::STAGE_POSTROLLBACK_CALLBACKS ) {
 251                                 $this->trxRoundStage = self::ROUND_ROLLBACK_CALLBACKS;
 252                         }
 253                 }
 254
 255                 $this->defaultGroup = $params['defaultGroup'] ?? null;
 256                 $this->ownerId = $params['ownerId'] ?? null;
 257         }
 258
 259         public function getLocalDomainID() {
 260                 return $this->localDomain->getId();
 261         }
 262
 263         public function resolveDomainID( $domain ) {
 264                 if ( $domain === $this->localDomainIdAlias || $domain === false ) {
 265                         // Local connection requested via some backwards-compatibility domain alias
 266                         return $this->getLocalDomainID();
 267                 }
 268
 269                 return (string)$domain;
 270         }
 271
 272         /**
 273          * @param int $flags
 274          * @return bool
 275          */
 276         private function sanitizeConnectionFlags( $flags ) {
 277                 if ( ( $flags & self::CONN_TRX_AUTOCOMMIT ) === self::CONN_TRX_AUTOCOMMIT ) {
 278                         // Assuming all servers are of the same type (or similar), which is overwhelmingly
 279                         // the case, use the master server information to get the attributes. The information
 280                         // for $i cannot be used since it might be DB_REPLICA, which might require connection
 281                         // attempts in order to be resolved into a real server index.
 282                         $attributes = $this->getServerAttributes( $this->getWriterIndex() );
 283                         if ( $attributes[Database::ATTR_DB_LEVEL_LOCKING] ) {
 284                                 // Callers sometimes want to (a) escape REPEATABLE-READ stateness without locking
 285                                 // rows (e.g. FOR UPDATE) or (b) make small commits during a larger transactions
 286                                 // to reduce lock contention. None of these apply for sqlite and using separate
 287                                 // connections just causes self-deadlocks.
 288                                 $flags &= ~self::CONN_TRX_AUTOCOMMIT;
 289                                 $this->connLogger->info( __METHOD__ .
 290                                         ': ignoring CONN_TRX_AUTOCOMMIT to avoid deadlocks.' );
 291                         }
 292                 }
 293
 294                 return $flags;
 295         }
 296
 297         /**
 298          * @param IDatabase $conn
 299          * @param int $flags
 300          * @throws DBUnexpectedError
 301          */
 302         private function enforceConnectionFlags( IDatabase $conn, $flags ) {
 303                 if ( ( $flags & self::CONN_TRX_AUTOCOMMIT ) == self::CONN_TRX_AUTOCOMMIT ) {
 304                         if ( $conn->trxLevel() ) { // sanity
 305                                 throw new DBUnexpectedError(
 306                                         $conn,
 307                                         'Handle requested with CONN_TRX_AUTOCOMMIT yet it has a transaction'
 308                                 );
 309                         }
 310
 311                         $conn->clearFlag( $conn::DBO_TRX ); // auto-commit mode
 312                 }
 313         }
 314
 315                 /**
 316          * Get a LoadMonitor instance
 317          *
 318          * @return ILoadMonitor
 319          */
 320         private function getLoadMonitor() {
 321                 if ( !isset( $this->loadMonitor ) ) {
 322                         $compat = [
 323                                 'LoadMonitor' => LoadMonitor::class,
 324                                 'LoadMonitorNull' => LoadMonitorNull::class,
 325                                 'LoadMonitorMySQL' => LoadMonitorMySQL::class,
 326                         ];
 327
 328                         $class = $this->loadMonitorConfig['class'];
 329                         if ( isset( $compat[$class] ) ) {
 330                                 $class = $compat[$class];
 331                         }
 332
 333                         $this->loadMonitor = new $class(
 334                                 $this, $this->srvCache, $this->wanCache, $this->loadMonitorConfig );
 335                         $this->loadMonitor->setLogger( $this->replLogger );
 336                 }
 337
 338                 return $this->loadMonitor;
 339         }
 340
 341         /**
 342          * @param array $loads
 343          * @param bool|string $domain Domain to get non-lagged for
 344          * @param int $maxLag Restrict the maximum allowed lag to this many seconds
 345          * @return bool|int|string
 346          */
 347         private function getRandomNonLagged( array $loads, $domain = false, $maxLag = INF ) {
 348                 $lags = $this->getLagTimes( $domain );
 349
 350                 # Unset excessively lagged servers
 351                 foreach ( $lags as $i => $lag ) {
 352                         if ( $i != 0 ) {
 353                                 # How much lag this server nominally is allowed to have
 354                                 $maxServerLag = $this->servers[$i]['max lag'] ?? $this->maxLag; // default
 355                                 # Constrain that futher by $maxLag argument
 356                                 $maxServerLag = min( $maxServerLag, $maxLag );
 357
 358                                 $host = $this->getServerName( $i );
 359                                 if ( $lag === false && !is_infinite( $maxServerLag ) ) {
 360                                         $this->replLogger->debug(
 361                                                 __METHOD__ .
 362                                                 ": server {host} is not replicating?", [ 'host' => $host ] );
 363                                         unset( $loads[$i] );
 364                                 } elseif ( $lag > $maxServerLag ) {
 365                                         $this->replLogger->debug(
 366                                                 __METHOD__ .
 367                                                 ": server {host} has {lag} seconds of lag (>= {maxlag})",
 368                                                 [ 'host' => $host, 'lag' => $lag, 'maxlag' => $maxServerLag ]
 369                                         );
 370                                         unset( $loads[$i] );
 371                                 }
 372                         }
 373                 }
 374
 375                 # Find out if all the replica DBs with non-zero load are lagged
 376                 $sum = 0;
 377                 foreach ( $loads as $load ) {
 378                         $sum += $load;
 379                 }
 380                 if ( $sum == 0 ) {
 381                         # No appropriate DB servers except maybe the master and some replica DBs with zero load
 382                         # Do NOT use the master
 383                         # Instead, this function will return false, triggering read-only mode,
 384                         # and a lagged replica DB will be used instead.
 385                         return false;
 386                 }
 387
 388                 if ( count( $loads ) == 0 ) {
 389                         return false;
 390                 }
 391
 392                 # Return a random representative of the remainder
 393                 return ArrayUtils::pickRandom( $loads );
 394         }
 395
 396         /**
 397          * @param int $i
 398          * @param array $groups
 399          * @param string|bool $domain
 400          * @return int The index of a specific server (replica DBs are checked for connectivity)
 401          */
 402         private function getConnectionIndex( $i, $groups, $domain ) {
 403                 // Check one "group" per default: the generic pool
 404                 $defaultGroups = $this->defaultGroup ? [ $this->defaultGroup ] : [ false ];
 405
 406                 $groups = ( $groups === false || $groups === [] )
 407                         ? $defaultGroups
 408                         : (array)$groups;
 409
 410                 if ( $i === self::DB_MASTER ) {
 411                         $i = $this->getWriterIndex();
 412                 } elseif ( $i === self::DB_REPLICA ) {
 413                         # Try to find an available server in any the query groups (in order)
 414                         foreach ( $groups as $group ) {
 415                                 $groupIndex = $this->getReaderIndex( $group, $domain );
 416                                 if ( $groupIndex !== false ) {
 417                                         $i = $groupIndex;
 418                                         break;
 419                                 }
 420                         }
 421                 }
 422
 423                 # Operation-based index
 424                 if ( $i === self::DB_REPLICA ) {
 425                         $this->lastError = 'Unknown error'; // reset error string
 426                         # Try the general server pool if $groups are unavailable.
 427                         $i = ( $groups === [ false ] )
 428                                 ? false // don't bother with this if that is what was tried above
 429                                 : $this->getReaderIndex( false, $domain );
 430                         # Couldn't find a working server in getReaderIndex()?
 431                         if ( $i === false ) {
 432                                 $this->lastError = 'No working replica DB server: ' . $this->lastError;
 433                                 // Throw an exception
 434                                 $this->reportConnectionError();
 435                                 return null; // unreachable due to exception
 436                         }
 437                 }
 438
 439                 return $i;
 440         }
 441
 442         public function getReaderIndex( $group = false, $domain = false ) {
 443                 if ( count( $this->servers ) == 1 ) {
 444                         // Skip the load balancing if there's only one server
 445                         return $this->getWriterIndex();
 446                 }
 447
 448                 $index = $this->getExistingReaderIndex( $group );
 449                 if ( $index >= 0 ) {
 450                         // A reader index was already selected and "waitForPos" was handled
 451                         return $index;
 452                 }
 453
 454                 if ( $group !== false ) {
 455                         // Use the server weight array for this load group
 456                         if ( isset( $this->groupLoads[$group] ) ) {
 457                                 $loads = $this->groupLoads[$group];
 458                         } else {
 459                                 // No loads for this group, return false and the caller can use some other group
 460                                 $this->connLogger->info( __METHOD__ . ": no loads for group $group" );
 461
 462                                 return false;
 463                         }
 464                 } else {
 465                         // Use the generic load group
 466                         $loads = $this->genericLoads;
 467                 }
 468
 469                 // Scale the configured load ratios according to each server's load and state
 470                 $this->getLoadMonitor()->scaleLoads( $loads, $domain );
 471
 472                 // Pick a server to use, accounting for weights, load, lag, and "waitForPos"
 473                 $this->lazyLoadReplicationPositions(); // optimizes server candidate selection
 474                 list( $i, $laggedReplicaMode ) = $this->pickReaderIndex( $loads, $domain );
 475                 if ( $i === false ) {
 476                         // DB connection unsuccessful
 477                         return false;
 478                 }
 479
 480                 // If data seen by queries is expected to reflect the transactions committed as of
 481                 // or after a given replication position then wait for the DB to apply those changes
 482                 if ( $this->waitForPos && $i != $this->getWriterIndex() && !$this->doWait( $i ) ) {
 483                         // Data will be outdated compared to what was expected
 484                         $laggedReplicaMode = true;
 485                 }
 486
 487                 // Cache the reader index for future DB_REPLICA handles
 488                 $this->setExistingReaderIndex( $group, $i );
 489                 // Record whether the generic reader index is in "lagged replica DB" mode
 490                 if ( $group === false && $laggedReplicaMode ) {
 491                         $this->laggedReplicaMode = true;
 492                 }
 493
 494                 $serverName = $this->getServerName( $i );
 495                 $this->connLogger->debug( __METHOD__ . ": using server $serverName for group '$group'" );
 496
 497                 return $i;
 498         }
 499
 500         /**
 501          * Get the server index chosen by the load balancer for use with the given query group
 502          *
 503          * @param string|bool $group Query group; use false for the generic group
 504          * @return int Server index or -1 if none was chosen
 505          */
 506         protected function getExistingReaderIndex( $group ) {
 507                 if ( $group === false ) {
 508                         $index = $this->genericReadIndex;
 509                 } else {
 510                         $index = $this->readIndexByGroup[$group] ?? -1;
 511                 }
 512
 513                 return $index;
 514         }
 515
 516         /**
 517          * Set the server index chosen by the load balancer for use with the given query group
 518          *
 519          * @param string|bool $group Query group; use false for the generic group
 520          * @param int $index The index of a specific server
 521          */
 522         private function setExistingReaderIndex( $group, $index ) {
 523                 if ( $index < 0 ) {
 524                         throw new UnexpectedValueException( "Cannot set a negative read server index" );
 525                 }
 526
 527                 if ( $group === false ) {
 528                         $this->genericReadIndex = $index;
 529                 } else {
 530                         $this->readIndexByGroup[$group] = $index;
 531                 }
 532         }
 533
 534         /**
 535          * @param array $loads List of server weights
 536          * @param string|bool $domain
 537          * @return array (reader index, lagged replica mode) or false on failure
 538          */
 539         private function pickReaderIndex( array $loads, $domain = false ) {
 540                 if ( $loads === [] ) {
 541                         throw new InvalidArgumentException( "Server configuration array is empty" );
 542                 }
 543
 544                 /** @var int|bool $i Index of selected server */
 545                 $i = false;
 546                 /** @var bool $laggedReplicaMode Whether server is considered lagged */
 547                 $laggedReplicaMode = false;
 548
 549                 // Quickly look through the available servers for a server that meets criteria...
 550                 $currentLoads = $loads;
 551                 while ( count( $currentLoads ) ) {
 552                         if ( $this->allowLagged || $laggedReplicaMode ) {
 553                                 $i = ArrayUtils::pickRandom( $currentLoads );
 554                         } else {
 555                                 $i = false;
 556                                 if ( $this->waitForPos && $this->waitForPos->asOfTime() ) {
 557                                         $this->replLogger->debug( __METHOD__ . ": replication positions detected" );
 558                                         // "chronologyCallback" sets "waitForPos" for session consistency.
 559                                         // This triggers doWait() after connect, so it's especially good to
 560                                         // avoid lagged servers so as to avoid excessive delay in that method.
 561                                         $ago = microtime( true ) - $this->waitForPos->asOfTime();
 562                                         // Aim for <= 1 second of waiting (being too picky can backfire)
 563                                         $i = $this->getRandomNonLagged( $currentLoads, $domain, $ago + 1 );
 564                                 }
 565                                 if ( $i === false ) {
 566                                         // Any server with less lag than it's 'max lag' param is preferable
 567                                         $i = $this->getRandomNonLagged( $currentLoads, $domain );
 568                                 }
 569                                 if ( $i === false && count( $currentLoads ) != 0 ) {
 570                                         // All replica DBs lagged. Switch to read-only mode
 571                                         $this->replLogger->error(
 572                                                 __METHOD__ . ": all replica DBs lagged. Switch to read-only mode" );
 573                                         $i = ArrayUtils::pickRandom( $currentLoads );
 574                                         $laggedReplicaMode = true;
 575                                 }
 576                         }
 577
 578                         if ( $i === false ) {
 579                                 // pickRandom() returned false.
 580                                 // This is permanent and means the configuration or the load monitor
 581                                 // wants us to return false.
 582                                 $this->connLogger->debug( __METHOD__ . ": pickRandom() returned false" );
 583
 584                                 return [ false, false ];
 585                         }
 586
 587                         $serverName = $this->getServerName( $i );
 588                         $this->connLogger->debug( __METHOD__ . ": Using reader #$i: $serverName..." );
 589
 590                         $conn = $this->getConnection( $i, [], $domain, self::CONN_SILENCE_ERRORS );
 591                         if ( !$conn ) {
 592                                 $this->connLogger->warning( __METHOD__ . ": Failed connecting to $i/$domain" );
 593                                 unset( $currentLoads[$i] ); // avoid this server next iteration
 594                                 $i = false;
 595                                 continue;
 596                         }
 597
 598                         // Decrement reference counter, we are finished with this connection.
 599                         // It will be incremented for the caller later.
 600                         if ( $domain !== false ) {
 601                                 $this->reuseConnection( $conn );
 602                         }
 603
 604                         // Return this server
 605                         break;
 606                 }
 607
 608                 // If all servers were down, quit now
 609                 if ( $currentLoads === [] ) {
 610                         $this->connLogger->error( __METHOD__ . ": all servers down" );
 611                 }
 612
 613                 return [ $i, $laggedReplicaMode ];
 614         }
 615
 616         public function waitFor( $pos ) {
 617                 $oldPos = $this->waitForPos;
 618                 try {
 619                         $this->waitForPos = $pos;
 620                         // If a generic reader connection was already established, then wait now
 621                         if ( $this->genericReadIndex > 0 && !$this->doWait( $this->genericReadIndex ) ) {
 622                                 $this->laggedReplicaMode = true;
 623                         }
 624                         // Otherwise, wait until a connection is established in getReaderIndex()
 625                 } finally {
 626                         // Restore the older position if it was higher since this is used for lag-protection
 627                         $this->setWaitForPositionIfHigher( $oldPos );
 628                 }
 629         }
 630
 631         public function waitForOne( $pos, $timeout = null ) {
 632                 $oldPos = $this->waitForPos;
 633                 try {
 634                         $this->waitForPos = $pos;
 635
 636                         $i = $this->genericReadIndex;
 637                         if ( $i <= 0 ) {
 638                                 // Pick a generic replica DB if there isn't one yet
 639                                 $readLoads = $this->genericLoads;
 640                                 unset( $readLoads[$this->getWriterIndex()] ); // replica DBs only
 641                                 $readLoads = array_filter( $readLoads ); // with non-zero load
 642                                 $i = ArrayUtils::pickRandom( $readLoads );
 643                         }
 644
 645                         if ( $i > 0 ) {
 646                                 $ok = $this->doWait( $i, true, $timeout );
 647                         } else {
 648                                 $ok = true; // no applicable loads
 649                         }
 650                 } finally {
 651                         # Restore the old position, as this is not used for lag-protection but for throttling
 652                         $this->waitForPos = $oldPos;
 653                 }
 654
 655                 return $ok;
 656         }
 657
 658         public function waitForAll( $pos, $timeout = null ) {
 659                 $timeout = $timeout ?: $this->waitTimeout;
 660
 661                 $oldPos = $this->waitForPos;
 662                 try {
 663                         $this->waitForPos = $pos;
 664                         $serverCount = count( $this->servers );
 665
 666                         $ok = true;
 667                         for ( $i = 1; $i < $serverCount; $i++ ) {
 668                                 if ( $this->genericLoads[$i] > 0 ) {
 669                                         $start = microtime( true );
 670                                         $ok = $this->doWait( $i, true, $timeout ) && $ok;
 671                                         $timeout -= intval( microtime( true ) - $start );
 672                                         if ( $timeout <= 0 ) {
 673                                                 break; // timeout reached
 674                                         }
 675                                 }
 676                         }
 677                 } finally {
 678                         # Restore the old position, as this is not used for lag-protection but for throttling
 679                         $this->waitForPos = $oldPos;
 680                 }
 681
 682                 return $ok;
 683         }
 684
 685         /**
 686          * @param DBMasterPos|bool $pos
 687          */
 688         private function setWaitForPositionIfHigher( $pos ) {
 689                 if ( !$pos ) {
 690                         return;
 691                 }
 692
 693                 if ( !$this->waitForPos || $pos->hasReached( $this->waitForPos ) ) {
 694                         $this->waitForPos = $pos;
 695                 }
 696         }
 697
 698         public function getAnyOpenConnection( $i, $flags = 0 ) {
 699                 $i = ( $i === self::DB_MASTER ) ? $this->getWriterIndex() : $i;
 700                 $autocommit = ( ( $flags & self::CONN_TRX_AUTOCOMMIT ) == self::CONN_TRX_AUTOCOMMIT );
 701
 702                 foreach ( $this->conns as $connsByServer ) {
 703                         if ( $i === self::DB_REPLICA ) {
 704                                 $indexes = array_keys( $connsByServer );
 705                         } else {
 706                                 $indexes = isset( $connsByServer[$i] ) ? [ $i ] : [];
 707                         }
 708
 709                         foreach ( $indexes as $index ) {
 710                                 foreach ( $connsByServer[$index] as $conn ) {
 711                                         if ( !$conn->isOpen() ) {
 712                                                 continue; // some sort of error occured?
 713                                         }
 714                                         if ( !$autocommit || $conn->getLBInfo( 'autoCommitOnly' ) ) {
 715                                                 return $conn;
 716                                         }
 717                                 }
 718                         }
 719                 }
 720
 721                 return false;
 722         }
 723
 724         /**
 725          * Wait for a given replica DB to catch up to the master pos stored in $this
 726          * @param int $index Server index
 727          * @param bool $open Check the server even if a new connection has to be made
 728          * @param int|null $timeout Max seconds to wait; default is "waitTimeout" given to __construct()
 729          * @return bool
 730          */
 731         protected function doWait( $index, $open = false, $timeout = null ) {
 732                 $timeout = max( 1, intval( $timeout ?: $this->waitTimeout ) );
 733
 734                 // Check if we already know that the DB has reached this point
 735                 $server = $this->getServerName( $index );
 736                 $key = $this->srvCache->makeGlobalKey( __CLASS__, 'last-known-pos', $server, 'v1' );
 737                 /** @var DBMasterPos $knownReachedPos */
 738                 $knownReachedPos = $this->srvCache->get( $key );
 739                 if (
 740                         $knownReachedPos instanceof DBMasterPos &&
 741                         $knownReachedPos->hasReached( $this->waitForPos )
 742                 ) {
 743                         $this->replLogger->debug(
 744                                 __METHOD__ .
 745                                 ': replica DB {dbserver} known to be caught up (pos >= $knownReachedPos).',
 746                                 [ 'dbserver' => $server ]
 747                         );
 748                         return true;
 749                 }
 750
 751                 // Find a connection to wait on, creating one if needed and allowed
 752                 $close = false; // close the connection afterwards
 753                 $conn = $this->getAnyOpenConnection( $index );
 754                 if ( !$conn ) {
 755                         if ( !$open ) {
 756                                 $this->replLogger->debug(
 757                                         __METHOD__ . ': no connection open for {dbserver}',
 758                                         [ 'dbserver' => $server ]
 759                                 );
 760
 761                                 return false;
 762                         }
 763                         // Open a temporary new connection in order to wait for replication
 764                         $conn = $this->getConnection( $index, [], self::DOMAIN_ANY, self::CONN_SILENCE_ERRORS );
 765                         if ( !$conn ) {
 766                                 $this->replLogger->warning(
 767                                         __METHOD__ . ': failed to connect to {dbserver}',
 768                                         [ 'dbserver' => $server ]
 769                                 );
 770
 771                                 return false;
 772                         }
 773                         // Avoid connection spam in waitForAll() when connections
 774                         // are made just for the sake of doing this lag check.
 775                         $close = true;
 776                 }
 777
 778                 $this->replLogger->info(
 779                         __METHOD__ .
 780                         ': waiting for replica DB {dbserver} to catch up...',
 781                         [ 'dbserver' => $server ]
 782                 );
 783
 784                 $result = $conn->masterPosWait( $this->waitForPos, $timeout );
 785
 786                 if ( $result === null ) {
 787                         $this->replLogger->warning(
 788                                 __METHOD__ . ': Errored out waiting on {host} pos {pos}',
 789                                 [
 790                                         'host' => $server,
 791                                         'pos' => $this->waitForPos,
 792                                         'trace' => ( new RuntimeException() )->getTraceAsString()
 793                                 ]
 794                         );
 795                         $ok = false;
 796                 } elseif ( $result == -1 ) {
 797                         $this->replLogger->warning(
 798                                 __METHOD__ . ': Timed out waiting on {host} pos {pos}',
 799                                 [
 800                                         'host' => $server,
 801                                         'pos' => $this->waitForPos,
 802                                         'trace' => ( new RuntimeException() )->getTraceAsString()
 803                                 ]
 804                         );
 805                         $ok = false;
 806                 } else {
 807                         $this->replLogger->debug( __METHOD__ . ": done waiting" );
 808                         $ok = true;
 809                         // Remember that the DB reached this point
 810                         $this->srvCache->set( $key, $this->waitForPos, BagOStuff::TTL_DAY );
 811                 }
 812
 813                 if ( $close ) {
 814                         $this->closeConnection( $conn );
 815                 }
 816
 817                 return $ok;
 818         }
 819
 820         public function getConnection( $i, $groups = [], $domain = false, $flags = 0 ) {
 821                 if ( !is_int( $i ) ) {
 822                         throw new InvalidArgumentException( "Cannot connect without a server index" );
 823                 } elseif ( $groups && $i > 0 ) {
 824                         throw new InvalidArgumentException( "Got query groups with server index #$i" );
 825                 }
 826
 827                 $domain = $this->resolveDomainID( $domain );
 828                 $flags = $this->sanitizeConnectionFlags( $flags );
 829                 $masterOnly = ( $i == self::DB_MASTER || $i == $this->getWriterIndex() );
 830
 831                 // Number of connections made before getting the server index and handle
 832                 $priorConnectionsMade = $this->connsOpened;
 833
 834                 // Choose a server if $i is DB_MASTER/DB_REPLICA (might trigger new connections)
 835                 $serverIndex = $this->getConnectionIndex( $i, $groups, $domain );
 836                 // Get an open connection to that server (might trigger a new connection)
 837                 $conn = $this->localDomain->equals( $domain )
 838                         ? $this->getLocalConnection( $serverIndex, $flags )
 839                         : $this->getForeignConnection( $serverIndex, $domain, $flags );
 840                 // Throw an error or bail out if the connection attempt failed
 841                 if ( !( $conn instanceof IDatabase ) ) {
 842                         if ( ( $flags & self::CONN_SILENCE_ERRORS ) != self::CONN_SILENCE_ERRORS ) {
 843                                 $this->reportConnectionError();
 844                         }
 845
 846                         return false;
 847                 }
 848
 849                 // Profile any new connections caused by this method
 850                 if ( $this->connsOpened > $priorConnectionsMade ) {
 851                         $host = $conn->getServer();
 852                         $dbname = $conn->getDBname();
 853                         $this->trxProfiler->recordConnection( $host, $dbname, $masterOnly );
 854                 }
 855
 856                 if ( !$conn->isOpen() ) {
 857                         // Connection was made but later unrecoverably lost for some reason.
 858                         // Do not return a handle that will just throw exceptions on use,
 859                         // but let the calling code (e.g. getReaderIndex) try another server.
 860                         $this->errorConnection = $conn;
 861                         return false;
 862                 }
 863
 864                 $this->enforceConnectionFlags( $conn, $flags );
 865                 if ( $serverIndex == $this->getWriterIndex() ) {
 866                         // If the load balancer is read-only, perhaps due to replication lag, then master
 867                         // DB handles will reflect that. Note that Database::assertIsWritableMaster() takes
 868                         // care of replica DB handles whereas getReadOnlyReason() would cause infinite loops.
 869                         $conn->setLBInfo( 'readOnlyReason', $this->getReadOnlyReason( $domain, $conn ) );
 870                 }
 871
 872                 return $conn;
 873         }
 874
 875         public function reuseConnection( IDatabase $conn ) {
 876                 $serverIndex = $conn->getLBInfo( 'serverIndex' );
 877                 $refCount = $conn->getLBInfo( 'foreignPoolRefCount' );
 878                 if ( $serverIndex === null || $refCount === null ) {
 879                         /**
 880                          * This can happen in code like:
 881                          *   foreach ( $dbs as $db ) {
 882                          *     $conn = $lb->getConnection( $lb::DB_REPLICA, [], $db );
 883                          *     ...
 884                          *     $lb->reuseConnection( $conn );
 885                          *   }
 886                          * When a connection to the local DB is opened in this way, reuseConnection()
 887                          * should be ignored
 888                          */
 889                         return;
 890                 } elseif ( $conn instanceof DBConnRef ) {
 891                         // DBConnRef already handles calling reuseConnection() and only passes the live
 892                         // Database instance to this method. Any caller passing in a DBConnRef is broken.
 893                         $this->connLogger->error(
 894                                 __METHOD__ . ": got DBConnRef instance.\n" .
 895                                 ( new RuntimeException() )->getTraceAsString() );
 896
 897                         return;
 898                 }
 899
 900                 if ( $this->disabled ) {
 901                         return; // DBConnRef handle probably survived longer than the LoadBalancer
 902                 }
 903
 904                 if ( $conn->getLBInfo( 'autoCommitOnly' ) ) {
 905                         $connFreeKey = self::KEY_FOREIGN_FREE_NOROUND;
 906                         $connInUseKey = self::KEY_FOREIGN_INUSE_NOROUND;
 907                 } else {
 908                         $connFreeKey = self::KEY_FOREIGN_FREE;
 909                         $connInUseKey = self::KEY_FOREIGN_INUSE;
 910                 }
 911
 912                 $domain = $conn->getDomainID();
 913                 if ( !isset( $this->conns[$connInUseKey][$serverIndex][$domain] ) ) {
 914                         throw new InvalidArgumentException(
 915                                 "Connection $serverIndex/$domain not found; it may have already been freed" );
 916                 } elseif ( $this->conns[$connInUseKey][$serverIndex][$domain] !== $conn ) {
 917                         throw new InvalidArgumentException(
 918                                 "Connection $serverIndex/$domain mismatched; it may have already been freed" );
 919                 }
 920
 921                 $conn->setLBInfo( 'foreignPoolRefCount', --$refCount );
 922                 if ( $refCount <= 0 ) {
 923                         $this->conns[$connFreeKey][$serverIndex][$domain] = $conn;
 924                         unset( $this->conns[$connInUseKey][$serverIndex][$domain] );
 925                         if ( !$this->conns[$connInUseKey][$serverIndex] ) {
 926                                 unset( $this->conns[$connInUseKey][$serverIndex] ); // clean up
 927                         }
 928                         $this->connLogger->debug( __METHOD__ . ": freed connection $serverIndex/$domain" );
 929                 } else {
 930                         $this->connLogger->debug( __METHOD__ .
 931                                 ": reference count for $serverIndex/$domain reduced to $refCount" );
 932                 }
 933         }
 934
 935         public function getConnectionRef( $i, $groups = [], $domain = false, $flags = 0 ) {
 936                 $domain = $this->resolveDomainID( $domain );
 937                 $role = $this->getRoleFromIndex( $i );
 938
 939                 return new DBConnRef( $this, $this->getConnection( $i, $groups, $domain, $flags ), $role );
 940         }
 941
 942         public function getLazyConnectionRef( $i, $groups = [], $domain = false, $flags = 0 ) {
 943                 $domain = $this->resolveDomainID( $domain );
 944                 $role = $this->getRoleFromIndex( $i );
 945
 946                 return new DBConnRef( $this, [ $i, $groups, $domain, $flags ], $role );
 947         }
 948
 949         public function getMaintenanceConnectionRef( $i, $groups = [], $domain = false, $flags = 0 ) {
 950                 $domain = $this->resolveDomainID( $domain );
 951                 $role = $this->getRoleFromIndex( $i );
 952
 953                 return new MaintainableDBConnRef(
 954                         $this, $this->getConnection( $i, $groups, $domain, $flags ), $role );
 955         }
 956
 957         /**
 958          * @param int $i Server index or DB_MASTER/DB_REPLICA
 959          * @return int One of DB_MASTER/DB_REPLICA
 960          */
 961         private function getRoleFromIndex( $i ) {
 962                 return ( $i === self::DB_MASTER || $i === $this->getWriterIndex() )
 963                         ? self::DB_MASTER
 964                         : self::DB_REPLICA;
 965         }
 966
 967         /**
 968          * @param int $i
 969          * @param bool $domain
 970          * @param int $flags
 971          * @return Database|bool Live database handle or false on failure
 972          * @deprecated Since 1.34 Use getConnection() instead
 973          */
 974         public function openConnection( $i, $domain = false, $flags = 0 ) {
 975                 return $this->getConnection( $i, [], $domain, $flags | self::CONN_SILENCE_ERRORS );
 976         }
 977
 978         /**
 979          * Open a connection to a local DB, or return one if it is already open.
 980          *
 981          * On error, returns false, and the connection which caused the
 982          * error will be available via $this->errorConnection.
 983          *
 984          * @note If disable() was called on this LoadBalancer, this method will throw a DBAccessError.
 985          *
 986          * @param int $i Server index
 987          * @param int $flags Class CONN_* constant bitfield
 988          * @return Database
 989          */
 990         private function getLocalConnection( $i, $flags = 0 ) {
 991                 // Connection handles required to be in auto-commit mode use a separate connection
 992                 // pool since the main pool is effected by implicit and explicit transaction rounds
 993                 $autoCommit = ( ( $flags & self::CONN_TRX_AUTOCOMMIT ) == self::CONN_TRX_AUTOCOMMIT );
 994
 995                 $connKey = $autoCommit ? self::KEY_LOCAL_NOROUND : self::KEY_LOCAL;
 996                 if ( isset( $this->conns[$connKey][$i][0] ) ) {
 997                         $conn = $this->conns[$connKey][$i][0];
 998                 } else {
 999                         if ( !isset( $this->servers[$i] ) || !is_array( $this->servers[$i] ) ) {
1000                                 throw new InvalidArgumentException( "No server with index '$i'" );
1001                         }
1002                         // Open a new connection
1003                         $server = $this->servers[$i];
1004                         $server['serverIndex'] = $i;
1005                         $server['autoCommitOnly'] = $autoCommit;
1006                         $conn = $this->reallyOpenConnection( $server, $this->localDomain );
1007                         $host = $this->getServerName( $i );
1008                         if ( $conn->isOpen() ) {
1009                                 $this->connLogger->debug(
1010                                         __METHOD__ . ": connected to database $i at '$host'." );
1011                                 $this->conns[$connKey][$i][0] = $conn;
1012                         } else {
1013                                 $this->connLogger->warning(
1014                                         __METHOD__ . ": failed to connect to database $i at '$host'." );
1015                                 $this->errorConnection = $conn;
1016                                 $conn = false;
1017                         }
1018                 }
1019
1020                 // Final sanity check to make sure the right domain is selected
1021                 if (
1022                         $conn instanceof IDatabase &&
1023                         !$this->localDomain->isCompatible( $conn->getDomainID() )
1024                 ) {
1025                         throw new UnexpectedValueException(
1026                                 "Got connection to '{$conn->getDomainID()}', " .
1027                                 "but expected local domain ('{$this->localDomain}')" );
1028                 }
1029
1030                 return $conn;
1031         }
1032
1033         /**
1034          * Open a connection to a foreign DB, or return one if it is already open.
1035          *
1036          * Increments a reference count on the returned connection which locks the
1037          * connection to the requested domain. This reference count can be
1038          * decremented by calling reuseConnection().
1039          *
1040          * If a connection is open to the appropriate server already, but with the wrong
1041          * database, it will be switched to the right database and returned, as long as
1042          * it has been freed first with reuseConnection().
1043          *
1044          * On error, returns false, and the connection which caused the
1045          * error will be available via $this->errorConnection.
1046          *
1047          * @note If disable() was called on this LoadBalancer, this method will throw a DBAccessError.
1048          *
1049          * @param int $i Server index
1050          * @param string $domain Domain ID to open
1051          * @param int $flags Class CONN_* constant bitfield
1052          * @return Database|bool Returns false on connection error
1053          * @throws DBError When database selection fails
1054          */
1055         private function getForeignConnection( $i, $domain, $flags = 0 ) {
1056                 $domainInstance = DatabaseDomain::newFromId( $domain );
1057                 // Connection handles required to be in auto-commit mode use a separate connection
1058                 // pool since the main pool is effected by implicit and explicit transaction rounds
1059                 $autoCommit = ( ( $flags & self::CONN_TRX_AUTOCOMMIT ) == self::CONN_TRX_AUTOCOMMIT );
1060
1061                 if ( $autoCommit ) {
1062                         $connFreeKey = self::KEY_FOREIGN_FREE_NOROUND;
1063                         $connInUseKey = self::KEY_FOREIGN_INUSE_NOROUND;
1064                 } else {
1065                         $connFreeKey = self::KEY_FOREIGN_FREE;
1066                         $connInUseKey = self::KEY_FOREIGN_INUSE;
1067                 }
1068
1069                 /** @var Database $conn */
1070                 $conn = null;
1071
1072                 if ( isset( $this->conns[$connInUseKey][$i][$domain] ) ) {
1073                         // Reuse an in-use connection for the same domain
1074                         $conn = $this->conns[$connInUseKey][$i][$domain];
1075                         $this->connLogger->debug( __METHOD__ . ": reusing connection $i/$domain" );
1076                 } elseif ( isset( $this->conns[$connFreeKey][$i][$domain] ) ) {
1077                         // Reuse a free connection for the same domain
1078                         $conn = $this->conns[$connFreeKey][$i][$domain];
1079                         unset( $this->conns[$connFreeKey][$i][$domain] );
1080                         $this->conns[$connInUseKey][$i][$domain] = $conn;
1081                         $this->connLogger->debug( __METHOD__ . ": reusing free connection $i/$domain" );
1082                 } elseif ( !empty( $this->conns[$connFreeKey][$i] ) ) {
1083                         // Reuse a free connection from another domain if possible
1084                         foreach ( $this->conns[$connFreeKey][$i] as $oldDomain => $conn ) {
1085                                 if ( $domainInstance->getDatabase() !== null ) {
1086                                         // Check if changing the database will require a new connection.
1087                                         // In that case, leave the connection handle alone and keep looking.
1088                                         // This prevents connections from being closed mid-transaction and can
1089                                         // also avoid overhead if the same database will later be requested.
1090                                         if (
1091                                                 $conn->databasesAreIndependent() &&
1092                                                 $conn->getDBname() !== $domainInstance->getDatabase()
1093                                         ) {
1094                                                 continue;
1095                                         }
1096                                         // Select the new database, schema, and prefix
1097                                         $conn->selectDomain( $domainInstance );
1098                                 } else {
1099                                         // Stay on the current database, but update the schema/prefix
1100                                         $conn->dbSchema( $domainInstance->getSchema() );
1101                                         $conn->tablePrefix( $domainInstance->getTablePrefix() );
1102                                 }
1103                                 unset( $this->conns[$connFreeKey][$i][$oldDomain] );
1104                                 // Note that if $domain is an empty string, getDomainID() might not match it
1105                                 $this->conns[$connInUseKey][$i][$conn->getDomainID()] = $conn;
1106                                 $this->connLogger->debug( __METHOD__ .
1107                                         ": reusing free connection from $oldDomain for $domain" );
1108                                 break;
1109                         }
1110                 }
1111
1112                 if ( !$conn ) {
1113                         if ( !isset( $this->servers[$i] ) || !is_array( $this->servers[$i] ) ) {
1114                                 throw new InvalidArgumentException( "No server with index '$i'" );
1115                         }
1116                         // Open a new connection
1117                         $server = $this->servers[$i];
1118                         $server['serverIndex'] = $i;
1119                         $server['foreignPoolRefCount'] = 0;
1120                         $server['foreign'] = true;
1121                         $server['autoCommitOnly'] = $autoCommit;
1122                         $conn = $this->reallyOpenConnection( $server, $domainInstance );
1123                         if ( !$conn->isOpen() ) {
1124                                 $this->connLogger->warning( __METHOD__ . ": connection error for $i/$domain" );
1125                                 $this->errorConnection = $conn;
1126                                 $conn = false;
1127                         } else {
1128                                 // Note that if $domain is an empty string, getDomainID() might not match it
1129                                 $this->conns[$connInUseKey][$i][$conn->getDomainID()] = $conn;
1130                                 $this->connLogger->debug( __METHOD__ . ": opened new connection for $i/$domain" );
1131                         }
1132                 }
1133
1134                 if ( $conn instanceof IDatabase ) {
1135                         // Final sanity check to make sure the right domain is selected
1136                         if ( !$domainInstance->isCompatible( $conn->getDomainID() ) ) {
1137                                 throw new UnexpectedValueException(
1138                                         "Got connection to '{$conn->getDomainID()}', but expected '$domain'" );
1139                         }
1140                         // Increment reference count
1141                         $refCount = $conn->getLBInfo( 'foreignPoolRefCount' );
1142                         $conn->setLBInfo( 'foreignPoolRefCount', $refCount + 1 );
1143                 }
1144
1145                 return $conn;
1146         }
1147
1148         public function getServerAttributes( $i ) {
1149                 return Database::attributesFromType(
1150                         $this->getServerType( $i ),
1151                         $this->servers[$i]['driver'] ?? null
1152                 );
1153         }
1154
1155         /**
1156          * Test if the specified index represents an open connection
1157          *
1158          * @param int $index Server index
1159          * @private
1160          * @return bool
1161          */
1162         private function isOpen( $index ) {
1163                 if ( !is_int( $index ) ) {
1164                         return false;
1165                 }
1166
1167                 return (bool)$this->getAnyOpenConnection( $index );
1168         }
1169
1170         /**
1171          * Open a new network connection to a server (uncached)
1172          *
1173          * Returns a Database object whether or not the connection was successful.
1174          *
1175          * @param array $server
1176          * @param DatabaseDomain $domain Domain the connection is for, possibly unspecified
1177          * @return Database
1178          * @throws DBAccessError
1179          * @throws InvalidArgumentException
1180          */
1181         protected function reallyOpenConnection( array $server, DatabaseDomain $domain ) {
1182                 if ( $this->disabled ) {
1183                         throw new DBAccessError();
1184                 }
1185
1186                 if ( $domain->getDatabase() === null ) {
1187                         // The database domain does not specify a DB name and some database systems require a
1188                         // valid DB specified on connection. The $server configuration array contains a default
1189                         // DB name to use for connections in such cases.
1190                         if ( $server['type'] === 'mysql' ) {
1191                                 // For MySQL, DATABASE and SCHEMA are synonyms, connections need not specify a DB,
1192                                 // and the DB name in $server might not exist due to legacy reasons (the default
1193                                 // domain used to ignore the local LB domain, even when mismatched).
1194                                 $server['dbname'] = null;
1195                         }
1196                 } else {
1197                         $server['dbname'] = $domain->getDatabase();
1198                 }
1199
1200                 if ( $domain->getSchema() !== null ) {
1201                         $server['schema'] = $domain->getSchema();
1202                 }
1203
1204                 // It is always possible to connect with any prefix, even the empty string
1205                 $server['tablePrefix'] = $domain->getTablePrefix();
1206
1207                 // Let the handle know what the cluster master is (e.g. "db1052")
1208                 $masterName = $this->getServerName( $this->getWriterIndex() );
1209                 $server['clusterMasterHost'] = $masterName;
1210
1211                 // Log when many connection are made on requests
1212                 if ( ++$this->connsOpened >= self::CONN_HELD_WARN_THRESHOLD ) {
1213                         $this->perfLogger->warning( __METHOD__ . ": " .
1214                                 "{$this->connsOpened}+ connections made (master=$masterName)" );
1215                 }
1216
1217                 $server['srvCache'] = $this->srvCache;
1218                 // Set loggers and profilers
1219                 $server['connLogger'] = $this->connLogger;
1220                 $server['queryLogger'] = $this->queryLogger;
1221                 $server['errorLogger'] = $this->errorLogger;
1222                 $server['deprecationLogger'] = $this->deprecationLogger;
1223                 $server['profiler'] = $this->profiler;
1224                 $server['trxProfiler'] = $this->trxProfiler;
1225                 // Use the same agent and PHP mode for all DB handles
1226                 $server['cliMode'] = $this->cliMode;
1227                 $server['agent'] = $this->agent;
1228                 // Use DBO_DEFAULT flags by default for LoadBalancer managed databases. Assume that the
1229                 // application calls LoadBalancer::commitMasterChanges() before the PHP script completes.
1230                 $server['flags'] = $server['flags'] ?? IDatabase::DBO_DEFAULT;
1231
1232                 // Create a live connection object
1233                 try {
1234                         $db = Database::factory( $server['type'], $server );
1235                 } catch ( DBConnectionError $e ) {
1236                         // FIXME: This is probably the ugliest thing I have ever done to
1237                         // PHP. I'm half-expecting it to segfault, just out of disgust. -- TS
1238                         $db = $e->db;
1239                 }
1240
1241                 $db->setLBInfo( $server );
1242                 $db->setLazyMasterHandle(
1243                         $this->getLazyConnectionRef( self::DB_MASTER, [], $db->getDomainID() )
1244                 );
1245                 $db->setTableAliases( $this->tableAliases );
1246                 $db->setIndexAliases( $this->indexAliases );
1247
1248                 if ( $server['serverIndex'] === $this->getWriterIndex() ) {
1249                         if ( $this->trxRoundId !== false ) {
1250                                 $this->applyTransactionRoundFlags( $db );
1251                         }
1252                         foreach ( $this->trxRecurringCallbacks as $name => $callback ) {
1253                                 $db->setTransactionListener( $name, $callback );
1254                         }
1255                 }
1256
1257                 $this->lazyLoadReplicationPositions(); // session consistency
1258
1259                 return $db;
1260         }
1261
1262         /**
1263          * Make sure that any "waitForPos" positions are loaded and available to doWait()
1264          */
1265         private function lazyLoadReplicationPositions() {
1266                 if ( !$this->connectionAttempted && $this->chronologyCallback ) {
1267                         $this->connectionAttempted = true;
1268                         ( $this->chronologyCallback )( $this ); // generally calls waitFor()
1269                         $this->connLogger->debug( __METHOD__ . ': executed chronology callback.' );
1270                 }
1271         }
1272
1273         /**
1274          * @throws DBConnectionError
1275          */
1276         private function reportConnectionError() {
1277                 $conn = $this->errorConnection; // the connection which caused the error
1278                 $context = [
1279                         'method' => __METHOD__,
1280                         'last_error' => $this->lastError,
1281                 ];
1282
1283                 if ( $conn instanceof IDatabase ) {
1284                         $context['db_server'] = $conn->getServer();
1285                         $this->connLogger->warning(
1286                                 __METHOD__ . ": connection error: {last_error} ({db_server})",
1287                                 $context
1288                         );
1289
1290                         throw new DBConnectionError( $conn, "{$this->lastError} ({$context['db_server']})" );
1291                 } else {
1292                         // No last connection, probably due to all servers being too busy
1293                         $this->connLogger->error(
1294                                 __METHOD__ .
1295                                 ": LB failure with no last connection. Connection error: {last_error}",
1296                                 $context
1297                         );
1298
1299                         // If all servers were busy, "lastError" will contain something sensible
1300                         throw new DBConnectionError( null, $this->lastError );
1301                 }
1302         }
1303
1304         public function getWriterIndex() {
1305                 return 0;
1306         }
1307
1308         public function haveIndex( $i ) {
1309                 return array_key_exists( $i, $this->servers );
1310         }
1311
1312         public function isNonZeroLoad( $i ) {
1313                 return array_key_exists( $i, $this->servers ) && $this->genericLoads[$i] != 0;
1314         }
1315
1316         public function getServerCount() {
1317                 return count( $this->servers );
1318         }
1319
1320         public function getServerName( $i ) {
1321                 $name = $this->servers[$i]['hostName'] ?? $this->servers[$i]['host'] ?? '';
1322
1323                 return ( $name != '' ) ? $name : 'localhost';
1324         }
1325
1326         public function getServerInfo( $i ) {
1327                 return $this->servers[$i] ?? false;
1328         }
1329
1330         public function getServerType( $i ) {
1331                 return $this->servers[$i]['type'] ?? 'unknown';
1332         }
1333
1334         public function getMasterPos() {
1335                 # If this entire request was served from a replica DB without opening a connection to the
1336                 # master (however unlikely that may be), then we can fetch the position from the replica DB.
1337                 $masterConn = $this->getAnyOpenConnection( $this->getWriterIndex() );
1338                 if ( !$masterConn ) {
1339                         $serverCount = count( $this->servers );
1340                         for ( $i = 1; $i < $serverCount; $i++ ) {
1341                                 $conn = $this->getAnyOpenConnection( $i );
1342                                 if ( $conn ) {
1343                                         return $conn->getReplicaPos();
1344                                 }
1345                         }
1346                 } else {
1347                         return $masterConn->getMasterPos();
1348                 }
1349
1350                 return false;
1351         }
1352
1353         public function disable() {
1354                 $this->closeAll();
1355                 $this->disabled = true;
1356         }
1357
1358         public function closeAll() {
1359                 $fname = __METHOD__;
1360                 $this->forEachOpenConnection( function ( IDatabase $conn ) use ( $fname ) {
1361                         $host = $conn->getServer();
1362                         $this->connLogger->debug(
1363                                 $fname . ": closing connection to database '$host'." );
1364                         $conn->close();
1365                 } );
1366
1367                 $this->conns = [
1368                         self::KEY_LOCAL => [],
1369                         self::KEY_FOREIGN_INUSE => [],
1370                         self::KEY_FOREIGN_FREE => [],
1371                         self::KEY_LOCAL_NOROUND => [],
1372                         self::KEY_FOREIGN_INUSE_NOROUND => [],
1373                         self::KEY_FOREIGN_FREE_NOROUND => []
1374                 ];
1375                 $this->connsOpened = 0;
1376         }
1377
1378         public function closeConnection( IDatabase $conn ) {
1379                 if ( $conn instanceof DBConnRef ) {
1380                         // Avoid calling close() but still leaving the handle in the pool
1381                         throw new RuntimeException( 'Cannot close DBConnRef instance; it must be shareable' );
1382                 }
1383
1384                 $serverIndex = $conn->getLBInfo( 'serverIndex' );
1385                 foreach ( $this->conns as $type => $connsByServer ) {
1386                         if ( !isset( $connsByServer[$serverIndex] ) ) {
1387                                 continue;
1388                         }
1389
1390                         foreach ( $connsByServer[$serverIndex] as $i => $trackedConn ) {
1391                                 if ( $conn === $trackedConn ) {
1392                                         $host = $this->getServerName( $i );
1393                                         $this->connLogger->debug(
1394                                                 __METHOD__ . ": closing connection to database $i at '$host'." );
1395                                         unset( $this->conns[$type][$serverIndex][$i] );
1396                                         --$this->connsOpened;
1397                                         break 2;
1398                                 }
1399                         }
1400                 }
1401
1402                 $conn->close();
1403         }
1404
1405         public function commitAll( $fname = __METHOD__, $owner = null ) {
1406                 $this->commitMasterChanges( $fname, $owner );
1407                 $this->flushMasterSnapshots( $fname );
1408                 $this->flushReplicaSnapshots( $fname );
1409         }
1410
1411         public function finalizeMasterChanges( $fname = __METHOD__, $owner = null ) {
1412                 $this->assertOwnership( $fname, $owner );
1413                 $this->assertTransactionRoundStage( [ self::ROUND_CURSORY, self::ROUND_FINALIZED ] );
1414
1415                 $this->trxRoundStage = self::ROUND_ERROR; // "failed" until proven otherwise
1416                 // Loop until callbacks stop adding callbacks on other connections
1417                 $total = 0;
1418                 do {
1419                         $count = 0; // callbacks execution attempts
1420                         $this->forEachOpenMasterConnection( function ( Database $conn ) use ( &$count ) {
1421                                 // Run any pre-commit callbacks while leaving the post-commit ones suppressed.
1422                                 // Any error should cause all (peer) transactions to be rolled back together.
1423                                 $count += $conn->runOnTransactionPreCommitCallbacks();
1424                         } );
1425                         $total += $count;
1426                 } while ( $count > 0 );
1427                 // Defer post-commit callbacks until after COMMIT/ROLLBACK happens on all handles
1428                 $this->forEachOpenMasterConnection( function ( Database $conn ) {
1429                         $conn->setTrxEndCallbackSuppression( true );
1430                 } );
1431                 $this->trxRoundStage = self::ROUND_FINALIZED;
1432
1433                 return $total;
1434         }
1435
1436         public function approveMasterChanges( array $options, $fname = __METHOD__, $owner = null ) {
1437                 $this->assertOwnership( $fname, $owner );
1438                 $this->assertTransactionRoundStage( self::ROUND_FINALIZED );
1439
1440                 $limit = $options['maxWriteDuration'] ?? 0;
1441
1442                 $this->trxRoundStage = self::ROUND_ERROR; // "failed" until proven otherwise
1443                 $this->forEachOpenMasterConnection( function ( IDatabase $conn ) use ( $limit ) {
1444                         // If atomic sections or explicit transactions are still open, some caller must have
1445                         // caught an exception but failed to properly rollback any changes. Detect that and
1446                         // throw and error (causing rollback).
1447                         $conn->assertNoOpenTransactions();
1448                         // Assert that the time to replicate the transaction will be sane.
1449                         // If this fails, then all DB transactions will be rollback back together.
1450                         $time = $conn->pendingWriteQueryDuration( $conn::ESTIMATE_DB_APPLY );
1451                         if ( $limit > 0 && $time > $limit ) {
1452                                 throw new DBTransactionSizeError(
1453                                         $conn,
1454                                         "Transaction spent $time second(s) in writes, exceeding the limit of $limit",
1455                                         [ $time, $limit ]
1456                                 );
1457                         }
1458                         // If a connection sits idle while slow queries execute on another, that connection
1459                         // may end up dropped before the commit round is reached. Ping servers to detect this.
1460                         if ( $conn->writesOrCallbacksPending() && !$conn->ping() ) {
1461                                 throw new DBTransactionError(
1462                                         $conn,
1463                                         "A connection to the {$conn->getDBname()} database was lost before commit"
1464                                 );
1465                         }
1466                 } );
1467                 $this->trxRoundStage = self::ROUND_APPROVED;
1468         }
1469
1470         public function beginMasterChanges( $fname = __METHOD__, $owner = null ) {
1471                 $this->assertOwnership( $fname, $owner );
1472                 if ( $this->trxRoundId !== false ) {
1473                         throw new DBTransactionError(
1474                                 null,
1475                                 "$fname: Transaction round '{$this->trxRoundId}' already started"
1476                         );
1477                 }
1478                 $this->assertTransactionRoundStage( self::ROUND_CURSORY );
1479
1480                 // Clear any empty transactions (no writes/callbacks) from the implicit round
1481                 $this->flushMasterSnapshots( $fname );
1482
1483                 $this->trxRoundId = $fname;
1484                 $this->trxRoundStage = self::ROUND_ERROR; // "failed" until proven otherwise
1485                 // Mark applicable handles as participating in this explicit transaction round.
1486                 // For each of these handles, any writes and callbacks will be tied to a single
1487                 // transaction. The (peer) handles will reject begin()/commit() calls unless they
1488                 // are part of an en masse commit or an en masse rollback.
1489                 $this->forEachOpenMasterConnection( function ( Database $conn ) {
1490                         $this->applyTransactionRoundFlags( $conn );
1491                 } );
1492                 $this->trxRoundStage = self::ROUND_CURSORY;
1493         }
1494
1495         public function commitMasterChanges( $fname = __METHOD__, $owner = null ) {
1496                 $this->assertOwnership( $fname, $owner );
1497                 $this->assertTransactionRoundStage( self::ROUND_APPROVED );
1498
1499                 $failures = [];
1500
1501                 /** @noinspection PhpUnusedLocalVariableInspection */
1502                 $scope = ScopedCallback::newScopedIgnoreUserAbort(); // try to ignore client aborts
1503
1504                 $restore = ( $this->trxRoundId !== false );
1505                 $this->trxRoundId = false;
1506                 $this->trxRoundStage = self::ROUND_ERROR; // "failed" until proven otherwise
1507                 // Commit any writes and clear any snapshots as well (callbacks require AUTOCOMMIT).
1508                 // Note that callbacks should already be suppressed due to finalizeMasterChanges().
1509                 $this->forEachOpenMasterConnection(
1510                         function ( IDatabase $conn ) use ( $fname, &$failures ) {
1511                                 try {
1512                                         $conn->commit( $fname, $conn::FLUSHING_ALL_PEERS );
1513                                 } catch ( DBError $e ) {
1514                                         ( $this->errorLogger )( $e );
1515                                         $failures[] = "{$conn->getServer()}: {$e->getMessage()}";
1516                                 }
1517                         }
1518                 );
1519                 if ( $failures ) {
1520                         throw new DBTransactionError(
1521                                 null,
1522                                 "$fname: Commit failed on server(s) " . implode( "\n", array_unique( $failures ) )
1523                         );
1524                 }
1525                 if ( $restore ) {
1526                         // Unmark handles as participating in this explicit transaction round
1527                         $this->forEachOpenMasterConnection( function ( Database $conn ) {
1528                                 $this->undoTransactionRoundFlags( $conn );
1529                         } );
1530                 }
1531                 $this->trxRoundStage = self::ROUND_COMMIT_CALLBACKS;
1532         }
1533
1534         public function runMasterTransactionIdleCallbacks( $fname = __METHOD__, $owner = null ) {
1535                 $this->assertOwnership( $fname, $owner );
1536                 if ( $this->trxRoundStage === self::ROUND_COMMIT_CALLBACKS ) {
1537                         $type = IDatabase::TRIGGER_COMMIT;
1538                 } elseif ( $this->trxRoundStage === self::ROUND_ROLLBACK_CALLBACKS ) {
1539                         $type = IDatabase::TRIGGER_ROLLBACK;
1540                 } else {
1541                         throw new DBTransactionError(
1542                                 null,
1543                                 "Transaction should be in the callback stage (not '{$this->trxRoundStage}')"
1544                         );
1545                 }
1546
1547                 $oldStage = $this->trxRoundStage;
1548                 $this->trxRoundStage = self::ROUND_ERROR; // "failed" until proven otherwise
1549
1550                 // Now that the COMMIT/ROLLBACK step is over, enable post-commit callback runs
1551                 $this->forEachOpenMasterConnection( function ( Database $conn ) {
1552                         $conn->setTrxEndCallbackSuppression( false );
1553                 } );
1554
1555                 $e = null; // first exception
1556                 $fname = __METHOD__;
1557                 // Loop until callbacks stop adding callbacks on other connections
1558                 do {
1559                         // Run any pending callbacks for each connection...
1560                         $count = 0; // callback execution attempts
1561                         $this->forEachOpenMasterConnection(
1562                                 function ( Database $conn ) use ( $type, &$e, &$count ) {
1563                                         if ( $conn->trxLevel() ) {
1564                                                 return; // retry in the next iteration, after commit() is called
1565                                         }
1566                                         try {
1567                                                 $count += $conn->runOnTransactionIdleCallbacks( $type );
1568                                         } catch ( Exception $ex ) {
1569                                                 $e = $e ?: $ex;
1570                                         }
1571                                 }
1572                         );
1573                         // Clear out any active transactions left over from callbacks...
1574                         $this->forEachOpenMasterConnection( function ( Database $conn ) use ( &$e, $fname ) {
1575                                 if ( $conn->writesPending() ) {
1576                                         // A callback from another handle wrote to this one and DBO_TRX is set
1577                                         $this->queryLogger->warning( $fname . ": found writes pending." );
1578                                         $fnames = implode( ', ', $conn->pendingWriteAndCallbackCallers() );
1579                                         $this->queryLogger->warning(
1580                                                 $fname . ": found writes pending ($fnames).",
1581                                                 [
1582                                                         'db_server' => $conn->getServer(),
1583                                                         'db_name' => $conn->getDBname()
1584                                                 ]
1585                                         );
1586                                 } elseif ( $conn->trxLevel() ) {
1587                                         // A callback from another handle read from this one and DBO_TRX is set,
1588                                         // which can easily happen if there is only one DB (no replicas)
1589                                         $this->queryLogger->debug( $fname . ": found empty transaction." );
1590                                 }
1591                                 try {
1592                                         $conn->commit( $fname, $conn::FLUSHING_ALL_PEERS );
1593                                 } catch ( Exception $ex ) {
1594                                         $e = $e ?: $ex;
1595                                 }
1596                         } );
1597                 } while ( $count > 0 );
1598
1599                 $this->trxRoundStage = $oldStage;
1600
1601                 return $e;
1602         }
1603
1604         public function runMasterTransactionListenerCallbacks( $fname = __METHOD__, $owner = null ) {
1605                 $this->assertOwnership( $fname, $owner );
1606                 if ( $this->trxRoundStage === self::ROUND_COMMIT_CALLBACKS ) {
1607                         $type = IDatabase::TRIGGER_COMMIT;
1608                 } elseif ( $this->trxRoundStage === self::ROUND_ROLLBACK_CALLBACKS ) {
1609                         $type = IDatabase::TRIGGER_ROLLBACK;
1610                 } else {
1611                         throw new DBTransactionError(
1612                                 null,
1613                                 "Transaction should be in the callback stage (not '{$this->trxRoundStage}')"
1614                         );
1615                 }
1616
1617                 $e = null;
1618
1619                 $this->trxRoundStage = self::ROUND_ERROR; // "failed" until proven otherwise
1620                 $this->forEachOpenMasterConnection( function ( Database $conn ) use ( $type, &$e ) {
1621                         try {
1622                                 $conn->runTransactionListenerCallbacks( $type );
1623                         } catch ( Exception $ex ) {
1624                                 $e = $e ?: $ex;
1625                         }
1626                 } );
1627                 $this->trxRoundStage = self::ROUND_CURSORY;
1628
1629                 return $e;
1630         }
1631
1632         public function rollbackMasterChanges( $fname = __METHOD__, $owner = null ) {
1633                 $this->assertOwnership( $fname, $owner );
1634
1635                 $restore = ( $this->trxRoundId !== false );
1636                 $this->trxRoundId = false;
1637                 $this->trxRoundStage = self::ROUND_ERROR; // "failed" until proven otherwise
1638                 $this->forEachOpenMasterConnection( function ( IDatabase $conn ) use ( $fname ) {
1639                         $conn->rollback( $fname, $conn::FLUSHING_ALL_PEERS );
1640                 } );
1641                 if ( $restore ) {
1642                         // Unmark handles as participating in this explicit transaction round
1643                         $this->forEachOpenMasterConnection( function ( Database $conn ) {
1644                                 $this->undoTransactionRoundFlags( $conn );
1645                         } );
1646                 }
1647                 $this->trxRoundStage = self::ROUND_ROLLBACK_CALLBACKS;
1648         }
1649
1650         /**
1651          * @param string|string[] $stage
1652          * @throws DBTransactionError
1653          */
1654         private function assertTransactionRoundStage( $stage ) {
1655                 $stages = (array)$stage;
1656
1657                 if ( !in_array( $this->trxRoundStage, $stages, true ) ) {
1658                         $stageList = implode(
1659                                 '/',
1660                                 array_map( function ( $v ) {
1661                                         return "'$v'";
1662                                 }, $stages )
1663                         );
1664                         throw new DBTransactionError(
1665                                 null,
1666                                 "Transaction round stage must be $stageList (not '{$this->trxRoundStage}')"
1667                         );
1668                 }
1669         }
1670
1671         /**
1672          * @param string $fname
1673          * @param int|null $owner Owner ID of the caller
1674          * @throws DBTransactionError
1675          */
1676         private function assertOwnership( $fname, $owner ) {
1677                 if ( $this->ownerId !== null && $owner !== $this->ownerId ) {
1678                         throw new DBTransactionError(
1679                                 null,
1680                                 "$fname: LoadBalancer is owned by LBFactory #{$this->ownerId} (got '$owner')."
1681                         );
1682                 }
1683         }
1684
1685         /**
1686          * Make all DB servers with DBO_DEFAULT/DBO_TRX set join the transaction round
1687          *
1688          * Some servers may have neither flag enabled, meaning that they opt out of such
1689          * transaction rounds and remain in auto-commit mode. Such behavior might be desired
1690          * when a DB server is used for something like simple key/value storage.
1691          *
1692          * @param Database $conn
1693          */
1694         private function applyTransactionRoundFlags( Database $conn ) {
1695                 if ( $conn->getLBInfo( 'autoCommitOnly' ) ) {
1696                         return; // transaction rounds do not apply to these connections
1697                 }
1698
1699                 if ( $conn->getFlag( $conn::DBO_DEFAULT ) ) {
1700                         // DBO_TRX is controlled entirely by CLI mode presence with DBO_DEFAULT.
1701                         // Force DBO_TRX even in CLI mode since a commit round is expected soon.
1702                         $conn->setFlag( $conn::DBO_TRX, $conn::REMEMBER_PRIOR );
1703                 }
1704
1705                 if ( $conn->getFlag( $conn::DBO_TRX ) ) {
1706                         $conn->setLBInfo( 'trxRoundId', $this->trxRoundId );
1707                 }
1708         }
1709
1710         /**
1711          * @param Database $conn
1712          */
1713         private function undoTransactionRoundFlags( Database $conn ) {
1714                 if ( $conn->getLBInfo( 'autoCommitOnly' ) ) {
1715                         return; // transaction rounds do not apply to these connections
1716                 }
1717
1718                 if ( $conn->getFlag( $conn::DBO_TRX ) ) {
1719                         $conn->setLBInfo( 'trxRoundId', false );
1720                 }
1721
1722                 if ( $conn->getFlag( $conn::DBO_DEFAULT ) ) {
1723                         $conn->restoreFlags( $conn::RESTORE_PRIOR );
1724                 }
1725         }
1726
1727         public function flushReplicaSnapshots( $fname = __METHOD__ ) {
1728                 $this->forEachOpenReplicaConnection( function ( IDatabase $conn ) use ( $fname ) {
1729                         $conn->flushSnapshot( $fname );
1730                 } );
1731         }
1732
1733         public function flushMasterSnapshots( $fname = __METHOD__ ) {
1734                 $this->forEachOpenMasterConnection( function ( IDatabase $conn ) use ( $fname ) {
1735                         $conn->flushSnapshot( $fname );
1736                 } );
1737         }
1738
1739         /**
1740          * @return string
1741          * @since 1.32
1742          */
1743         public function getTransactionRoundStage() {
1744                 return $this->trxRoundStage;
1745         }
1746
1747         public function hasMasterConnection() {
1748                 return $this->isOpen( $this->getWriterIndex() );
1749         }
1750
1751         public function hasMasterChanges() {
1752                 $pending = 0;
1753                 $this->forEachOpenMasterConnection( function ( IDatabase $conn ) use ( &$pending ) {
1754                         $pending |= $conn->writesOrCallbacksPending();
1755                 } );
1756
1757                 return (bool)$pending;
1758         }
1759
1760         public function lastMasterChangeTimestamp() {
1761                 $lastTime = false;
1762                 $this->forEachOpenMasterConnection( function ( IDatabase $conn ) use ( &$lastTime ) {
1763                         $lastTime = max( $lastTime, $conn->lastDoneWrites() );
1764                 } );
1765
1766                 return $lastTime;
1767         }
1768
1769         public function hasOrMadeRecentMasterChanges( $age = null ) {
1770                 $age = ( $age === null ) ? $this->waitTimeout : $age;
1771
1772                 return ( $this->hasMasterChanges()
1773                         || $this->lastMasterChangeTimestamp() > microtime( true ) - $age );
1774         }
1775
1776         public function pendingMasterChangeCallers() {
1777                 $fnames = [];
1778                 $this->forEachOpenMasterConnection( function ( IDatabase $conn ) use ( &$fnames ) {
1779                         $fnames = array_merge( $fnames, $conn->pendingWriteCallers() );
1780                 } );
1781
1782                 return $fnames;
1783         }
1784
1785         public function getLaggedReplicaMode( $domain = false ) {
1786                 if (
1787                         // Avoid recursion if there is only one DB
1788                         $this->getServerCount() > 1 &&
1789                         // Avoid recursion if the (non-zero load) master DB was picked for generic reads
1790                         $this->genericReadIndex !== $this->getWriterIndex() &&
1791                         // Stay in lagged replica mode during the load balancer instance lifetime
1792                         !$this->laggedReplicaMode
1793                 ) {
1794                         try {
1795                                 // Calling this method will set "laggedReplicaMode" as needed
1796                                 $this->getReaderIndex( false, $domain );
1797                         } catch ( DBConnectionError $e ) {
1798                                 // Avoid expensive re-connect attempts and failures
1799                                 $this->allReplicasDownMode = true;
1800                                 $this->laggedReplicaMode = true;
1801                         }
1802                 }
1803
1804                 return $this->laggedReplicaMode;
1805         }
1806
1807         public function laggedReplicaUsed() {
1808                 return $this->laggedReplicaMode;
1809         }
1810
1811         /**
1812          * @return bool
1813          * @since 1.27
1814          * @deprecated Since 1.28; use laggedReplicaUsed()
1815          */
1816         public function laggedSlaveUsed() {
1817                 return $this->laggedReplicaUsed();
1818         }
1819
1820         public function getReadOnlyReason( $domain = false, IDatabase $conn = null ) {
1821                 if ( $this->readOnlyReason !== false ) {
1822                         return $this->readOnlyReason;
1823                 } elseif ( $this->getLaggedReplicaMode( $domain ) ) {
1824                         if ( $this->allReplicasDownMode ) {
1825                                 return 'The database has been automatically locked ' .
1826                                         'until the replica database servers become available';
1827                         } else {
1828                                 return 'The database has been automatically locked ' .
1829                                         'while the replica database servers catch up to the master.';
1830                         }
1831                 } elseif ( $this->masterRunningReadOnly( $domain, $conn ) ) {
1832                         return 'The database master is running in read-only mode.';
1833                 }
1834
1835                 return false;
1836         }
1837
1838         /**
1839          * @param string $domain Domain ID, or false for the current domain
1840          * @param IDatabase|null $conn DB master connectionl used to avoid loops [optional]
1841          * @return bool
1842          */
1843         private function masterRunningReadOnly( $domain, IDatabase $conn = null ) {
1844                 $cache = $this->wanCache;
1845                 $masterServer = $this->getServerName( $this->getWriterIndex() );
1846
1847                 return (bool)$cache->getWithSetCallback(
1848                         $cache->makeGlobalKey( __CLASS__, 'server-read-only', $masterServer ),
1849                         self::TTL_CACHE_READONLY,
1850                         function () use ( $domain, $conn ) {
1851                                 $old = $this->trxProfiler->setSilenced( true );
1852                                 try {
1853                                         $dbw = $conn ?: $this->getConnection( self::DB_MASTER, [], $domain );
1854                                         $readOnly = (int)$dbw->serverIsReadOnly();
1855                                         if ( !$conn ) {
1856                                                 $this->reuseConnection( $dbw );
1857                                         }
1858                                 } catch ( DBError $e ) {
1859                                         $readOnly = 0;
1860                                 }
1861                                 $this->trxProfiler->setSilenced( $old );
1862                                 return $readOnly;
1863                         },
1864                         [ 'pcTTL' => $cache::TTL_PROC_LONG, 'busyValue' => 0 ]
1865                 );
1866         }
1867
1868         public function allowLagged( $mode = null ) {
1869                 if ( $mode === null ) {
1870                         return $this->allowLagged;
1871                 }
1872                 $this->allowLagged = $mode;
1873
1874                 return $this->allowLagged;
1875         }
1876
1877         public function pingAll() {
1878                 $success = true;
1879                 $this->forEachOpenConnection( function ( IDatabase $conn ) use ( &$success ) {
1880                         if ( !$conn->ping() ) {
1881                                 $success = false;
1882                         }
1883                 } );
1884
1885                 return $success;
1886         }
1887
1888         public function forEachOpenConnection( $callback, array $params = [] ) {
1889                 foreach ( $this->conns as $connsByServer ) {
1890                         foreach ( $connsByServer as $serverConns ) {
1891                                 foreach ( $serverConns as $conn ) {
1892                                         $callback( $conn, ...$params );
1893                                 }
1894                         }
1895                 }
1896         }
1897
1898         public function forEachOpenMasterConnection( $callback, array $params = [] ) {
1899                 $masterIndex = $this->getWriterIndex();
1900                 foreach ( $this->conns as $connsByServer ) {
1901                         if ( isset( $connsByServer[$masterIndex] ) ) {
1902                                 /** @var IDatabase $conn */
1903                                 foreach ( $connsByServer[$masterIndex] as $conn ) {
1904                                         $callback( $conn, ...$params );
1905                                 }
1906                         }
1907                 }
1908         }
1909
1910         public function forEachOpenReplicaConnection( $callback, array $params = [] ) {
1911                 foreach ( $this->conns as $connsByServer ) {
1912                         foreach ( $connsByServer as $i => $serverConns ) {
1913                                 if ( $i === $this->getWriterIndex() ) {
1914                                         continue; // skip master
1915                                 }
1916                                 foreach ( $serverConns as $conn ) {
1917                                         $callback( $conn, ...$params );
1918                                 }
1919                         }
1920                 }
1921         }
1922
1923         public function getMaxLag( $domain = false ) {
1924                 $maxLag = -1;
1925                 $host = '';
1926                 $maxIndex = 0;
1927
1928                 if ( $this->getServerCount() <= 1 ) {
1929                         return [ $host, $maxLag, $maxIndex ]; // no replication = no lag
1930                 }
1931
1932                 $lagTimes = $this->getLagTimes( $domain );
1933                 foreach ( $lagTimes as $i => $lag ) {
1934                         if ( $this->genericLoads[$i] > 0 && $lag > $maxLag ) {
1935                                 $maxLag = $lag;
1936                                 $host = $this->servers[$i]['host'];
1937                                 $maxIndex = $i;
1938                         }
1939                 }
1940
1941                 return [ $host, $maxLag, $maxIndex ];
1942         }
1943
1944         public function getLagTimes( $domain = false ) {
1945                 if ( $this->getServerCount() <= 1 ) {
1946                         return [ $this->getWriterIndex() => 0 ]; // no replication = no lag
1947                 }
1948
1949                 $knownLagTimes = []; // map of (server index => 0 seconds)
1950                 $indexesWithLag = [];
1951                 foreach ( $this->servers as $i => $server ) {
1952                         if ( empty( $server['is static'] ) ) {
1953                                 $indexesWithLag[] = $i; // DB server might have replication lag
1954                         } else {
1955                                 $knownLagTimes[$i] = 0; // DB server is a non-replicating and read-only archive
1956                         }
1957                 }
1958
1959                 return $this->getLoadMonitor()->getLagTimes( $indexesWithLag, $domain ) + $knownLagTimes;
1960         }
1961
1962         /**
1963          * Get the lag in seconds for a given connection, or zero if this load
1964          * balancer does not have replication enabled.
1965          *
1966          * This should be used in preference to Database::getLag() in cases where
1967          * replication may not be in use, since there is no way to determine if
1968          * replication is in use at the connection level without running
1969          * potentially restricted queries such as SHOW SLAVE STATUS. Using this
1970          * function instead of Database::getLag() avoids a fatal error in this
1971          * case on many installations.
1972          *
1973          * @param IDatabase $conn
1974          * @return int|bool Returns false on error
1975          * @deprecated Since 1.34 Use IDatabase::getLag() instead
1976          */
1977         public function safeGetLag( IDatabase $conn ) {
1978                 if ( $this->getServerCount() <= 1 ) {
1979                         return 0;
1980                 } else {
1981                         return $conn->getLag();
1982                 }
1983         }
1984
1985         public function safeWaitForMasterPos( IDatabase $conn, $pos = false, $timeout = null ) {
1986                 $timeout = max( 1, $timeout ?: $this->waitTimeout );
1987
1988                 if ( $this->getServerCount() <= 1 || !$conn->getLBInfo( 'replica' ) ) {
1989                         return true; // server is not a replica DB
1990                 }
1991
1992                 if ( !$pos ) {
1993                         // Get the current master position, opening a connection if needed
1994                         $index = $this->getWriterIndex();
1995                         $masterConn = $this->getAnyOpenConnection( $index );
1996                         if ( $masterConn ) {
1997                                 $pos = $masterConn->getMasterPos();
1998                         } else {
1999                                 $flags = self::CONN_SILENCE_ERRORS;
2000                                 $masterConn = $this->getConnection( $index, [], self::DOMAIN_ANY, $flags );
2001                                 if ( !$masterConn ) {
2002                                         throw new DBReplicationWaitError(
2003                                                 null,
2004                                                 "Could not obtain a master database connection to get the position"
2005                                         );
2006                                 }
2007                                 $pos = $masterConn->getMasterPos();
2008                                 $this->closeConnection( $masterConn );
2009                         }
2010                 }
2011
2012                 if ( $pos instanceof DBMasterPos ) {
2013                         $start = microtime( true );
2014                         $result = $conn->masterPosWait( $pos, $timeout );
2015                         $seconds = max( microtime( true ) - $start, 0 );
2016                         if ( $result == -1 || is_null( $result ) ) {
2017                                 $msg = __METHOD__ . ': timed out waiting on {host} pos {pos} [{seconds}s]';
2018                                 $this->replLogger->warning( $msg, [
2019                                         'host' => $conn->getServer(),
2020                                         'pos' => $pos,
2021                                         'seconds' => round( $seconds, 6 ),
2022                                         'trace' => ( new RuntimeException() )->getTraceAsString()
2023                                 ] );
2024                                 $ok = false;
2025                         } else {
2026                                 $this->replLogger->debug( __METHOD__ . ': done waiting' );
2027                                 $ok = true;
2028                         }
2029                 } else {
2030                         $ok = false; // something is misconfigured
2031                         $this->replLogger->error(
2032                                 __METHOD__ . ': could not get master pos for {host}',
2033                                 [
2034                                         'host' => $conn->getServer(),
2035                                         'trace' => ( new RuntimeException() )->getTraceAsString()
2036                                 ]
2037                         );
2038                 }
2039
2040                 return $ok;
2041         }
2042
2043         public function setTransactionListener( $name, callable $callback = null ) {
2044                 if ( $callback ) {
2045                         $this->trxRecurringCallbacks[$name] = $callback;
2046                 } else {
2047                         unset( $this->trxRecurringCallbacks[$name] );
2048                 }
2049                 $this->forEachOpenMasterConnection(
2050                         function ( IDatabase $conn ) use ( $name, $callback ) {
2051                                 $conn->setTransactionListener( $name, $callback );
2052                         }
2053                 );
2054         }
2055
2056         public function setTableAliases( array $aliases ) {
2057                 $this->tableAliases = $aliases;
2058         }
2059
2060         public function setIndexAliases( array $aliases ) {
2061                 $this->indexAliases = $aliases;
2062         }
2063
2064         /**
2065          * @param string $prefix
2066          * @deprecated Since 1.33
2067          */
2068         public function setDomainPrefix( $prefix ) {
2069                 $this->setLocalDomainPrefix( $prefix );
2070         }
2071
2072         public function setLocalDomainPrefix( $prefix ) {
2073                 // Find connections to explicit foreign domains still marked as in-use...
2074                 $domainsInUse = [];
2075                 $this->forEachOpenConnection( function ( IDatabase $conn ) use ( &$domainsInUse ) {
2076                         // Once reuseConnection() is called on a handle, its reference count goes from 1 to 0.
2077                         // Until then, it is still in use by the caller (explicitly or via DBConnRef scope).
2078                         if ( $conn->getLBInfo( 'foreignPoolRefCount' ) > 0 ) {
2079                                 $domainsInUse[] = $conn->getDomainID();
2080                         }
2081                 } );
2082
2083                 // Do not switch connections to explicit foreign domains unless marked as safe
2084                 if ( $domainsInUse ) {
2085                         $domains = implode( ', ', $domainsInUse );
2086                         throw new DBUnexpectedError( null,
2087                                 "Foreign domain connections are still in use ($domains)" );
2088                 }
2089
2090                 $this->setLocalDomain( new DatabaseDomain(
2091                         $this->localDomain->getDatabase(),
2092                         $this->localDomain->getSchema(),
2093                         $prefix
2094                 ) );
2095
2096                 // Update the prefix for all local connections...
2097                 $this->forEachOpenConnection( function ( IDatabase $db ) use ( $prefix ) {
2098                         if ( !$db->getLBInfo( 'foreign' ) ) {
2099                                 $db->tablePrefix( $prefix );
2100                         }
2101                 } );
2102         }
2103
2104         public function redefineLocalDomain( $domain ) {
2105                 $this->closeAll();
2106
2107                 $this->setLocalDomain( DatabaseDomain::newFromId( $domain ) );
2108         }
2109
2110         /**
2111          * @param DatabaseDomain $domain
2112          */
2113         private function setLocalDomain( DatabaseDomain $domain ) {
2114                 $this->localDomain = $domain;
2115                 // In case a caller assumes that the domain ID is simply <db>-<prefix>, which is almost
2116                 // always true, gracefully handle the case when they fail to account for escaping.
2117                 if ( $this->localDomain->getTablePrefix() != '' ) {
2118                         $this->localDomainIdAlias =
2119                                 $this->localDomain->getDatabase() . '-' . $this->localDomain->getTablePrefix();
2120                 } else {
2121                         $this->localDomainIdAlias = $this->localDomain->getDatabase();
2122                 }
2123         }
2124
2125         function __destruct() {
2126                 // Avoid connection leaks for sanity
2127                 $this->disable();
2128         }
2129 }
2130
2131 /**
2132  * @deprecated since 1.29
2133  */
2134 class_alias( LoadBalancer::class, 'LoadBalancer' );