includes/libs/rdbms/loadbalancer/LoadBalancer.php

   1 <?php
   2 /**
   3  * Database load balancing manager
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License as published by
   7  * the Free Software Foundation; either version 2 of the License, or
   8  * (at your option) any later version.
   9  *
  10  * This program is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  13  * GNU General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU General Public License along
  16  * with this program; if not, write to the Free Software Foundation, Inc.,
  17  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  18  * http://www.gnu.org/copyleft/gpl.html
  19  *
  20  * @file
  21  */
  22 namespace Wikimedia\Rdbms;
  23
  24 use Psr\Log\LoggerInterface;
  25 use Psr\Log\NullLogger;
  26 use Wikimedia\ScopedCallback;
  27 use BagOStuff;
  28 use EmptyBagOStuff;
  29 use WANObjectCache;
  30 use ArrayUtils;
  31 use InvalidArgumentException;
  32 use RuntimeException;
  33 use Exception;
  34
  35 /**
  36  * Database connection, tracking, load balancing, and transaction manager for a cluster
  37  *
  38  * @ingroup Database
  39  */
  40 class LoadBalancer implements ILoadBalancer {
  41         /** @var array[] Map of (server index => server config array) */
  42         private $mServers;
  43         /** @var Database[][][] Map of (connection category => server index => IDatabase[]) */
  44         private $mConns;
  45         /** @var float[] Map of (server index => weight) */
  46         private $mLoads;
  47         /** @var array[] Map of (group => server index => weight) */
  48         private $mGroupLoads;
  49         /** @var bool Whether to disregard replica DB lag as a factor in replica DB selection */
  50         private $mAllowLagged;
  51         /** @var int Seconds to spend waiting on replica DB lag to resolve */
  52         private $mWaitTimeout;
  53         /** @var array The LoadMonitor configuration */
  54         private $loadMonitorConfig;
  55         /** @var array[] $aliases Map of (table => (dbname, schema, prefix) map) */
  56         private $tableAliases = [];
  57
  58         /** @var ILoadMonitor */
  59         private $loadMonitor;
  60         /** @var ChronologyProtector|null */
  61         private $chronProt;
  62         /** @var BagOStuff */
  63         private $srvCache;
  64         /** @var WANObjectCache */
  65         private $wanCache;
  66         /** @var object|string Class name or object With profileIn/profileOut methods */
  67         protected $profiler;
  68         /** @var TransactionProfiler */
  69         protected $trxProfiler;
  70         /** @var LoggerInterface */
  71         protected $replLogger;
  72         /** @var LoggerInterface */
  73         protected $connLogger;
  74         /** @var LoggerInterface */
  75         protected $queryLogger;
  76         /** @var LoggerInterface */
  77         protected $perfLogger;
  78
  79         /** @var Database DB connection object that caused a problem */
  80         private $errorConnection;
  81         /** @var int The generic (not query grouped) replica DB index (of $mServers) */
  82         private $mReadIndex;
  83         /** @var bool|DBMasterPos False if not set */
  84         private $mWaitForPos;
  85         /** @var bool Whether the generic reader fell back to a lagged replica DB */
  86         private $laggedReplicaMode = false;
  87         /** @var bool Whether the generic reader fell back to a lagged replica DB */
  88         private $allReplicasDownMode = false;
  89         /** @var string The last DB selection or connection error */
  90         private $mLastError = 'Unknown error';
  91         /** @var string|bool Reason the LB is read-only or false if not */
  92         private $readOnlyReason = false;
  93         /** @var int Total connections opened */
  94         private $connsOpened = 0;
  95         /** @var string|bool String if a requested DBO_TRX transaction round is active */
  96         private $trxRoundId = false;
  97         /** @var array[] Map of (name => callable) */
  98         private $trxRecurringCallbacks = [];
  99         /** @var DatabaseDomain Local Domain ID and default for selectDB() calls */
 100         private $localDomain;
 101         /** @var string Alternate ID string for the domain instead of DatabaseDomain::getId() */
 102         private $localDomainIdAlias;
 103         /** @var string Current server name */
 104         private $host;
 105         /** @var bool Whether this PHP instance is for a CLI script */
 106         protected $cliMode;
 107         /** @var string Agent name for query profiling */
 108         protected $agent;
 109
 110         /** @var callable Exception logger */
 111         private $errorLogger;
 112
 113         /** @var bool */
 114         private $disabled = false;
 115         /** @var bool */
 116         private $chronProtInitialized = false;
 117         /** @var int */
 118         private $maxLag = self::MAX_LAG_DEFAULT;
 119
 120         /** @var int Warn when this many connection are held */
 121         const CONN_HELD_WARN_THRESHOLD = 10;
 122
 123         /** @var int Default 'maxLag' when unspecified */
 124         const MAX_LAG_DEFAULT = 10;
 125         /** @var int Seconds to cache master server read-only status */
 126         const TTL_CACHE_READONLY = 5;
 127
 128         const KEY_LOCAL = 'local';
 129         const KEY_FOREIGN_FREE = 'foreignFree';
 130         const KEY_FOREIGN_INUSE = 'foreignInUse';
 131
 132         const KEY_LOCAL_NOROUND = 'localAutoCommit';
 133         const KEY_FOREIGN_FREE_NOROUND = 'foreignFreeAutoCommit';
 134         const KEY_FOREIGN_INUSE_NOROUND = 'foreignInUseAutoCommit';
 135
 136         public function __construct( array $params ) {
 137                 if ( !isset( $params['servers'] ) ) {
 138                         throw new InvalidArgumentException( __CLASS__ . ': missing servers parameter' );
 139                 }
 140                 $this->mServers = $params['servers'];
 141                 foreach ( $this->mServers as $i => $server ) {
 142                         if ( $i == 0 ) {
 143                                 $this->mServers[$i]['master'] = true;
 144                         } else {
 145                                 $this->mServers[$i]['replica'] = true;
 146                         }
 147                 }
 148
 149                 $this->localDomain = isset( $params['localDomain'] )
 150                         ? DatabaseDomain::newFromId( $params['localDomain'] )
 151                         : DatabaseDomain::newUnspecified();
 152                 // In case a caller assumes that the domain ID is simply <db>-<prefix>, which is almost
 153                 // always true, gracefully handle the case when they fail to account for escaping.
 154                 if ( $this->localDomain->getTablePrefix() != '' ) {
 155                         $this->localDomainIdAlias =
 156                                 $this->localDomain->getDatabase() . '-' . $this->localDomain->getTablePrefix();
 157                 } else {
 158                         $this->localDomainIdAlias = $this->localDomain->getDatabase();
 159                 }
 160
 161                 $this->mWaitTimeout = isset( $params['waitTimeout'] ) ? $params['waitTimeout'] : 10;
 162
 163                 $this->mReadIndex = -1;
 164                 $this->mConns = [
 165                         // Connection were transaction rounds may be applied
 166                         self::KEY_LOCAL => [],
 167                         self::KEY_FOREIGN_INUSE => [],
 168                         self::KEY_FOREIGN_FREE => [],
 169                         // Auto-committing counterpart connections that ignore transaction rounds
 170                         self::KEY_LOCAL_NOROUND => [],
 171                         self::KEY_FOREIGN_INUSE_NOROUND => [],
 172                         self::KEY_FOREIGN_FREE_NOROUND => []
 173                 ];
 174                 $this->mLoads = [];
 175                 $this->mWaitForPos = false;
 176                 $this->mAllowLagged = false;
 177
 178                 if ( isset( $params['readOnlyReason'] ) && is_string( $params['readOnlyReason'] ) ) {
 179                         $this->readOnlyReason = $params['readOnlyReason'];
 180                 }
 181
 182                 if ( isset( $params['maxLag'] ) ) {
 183                         $this->maxLag = $params['maxLag'];
 184                 }
 185
 186                 if ( isset( $params['loadMonitor'] ) ) {
 187                         $this->loadMonitorConfig = $params['loadMonitor'];
 188                 } else {
 189                         $this->loadMonitorConfig = [ 'class' => 'LoadMonitorNull' ];
 190                 }
 191                 $this->loadMonitorConfig += [ 'lagWarnThreshold' => $this->maxLag ];
 192
 193                 foreach ( $params['servers'] as $i => $server ) {
 194                         $this->mLoads[$i] = $server['load'];
 195                         if ( isset( $server['groupLoads'] ) ) {
 196                                 foreach ( $server['groupLoads'] as $group => $ratio ) {
 197                                         if ( !isset( $this->mGroupLoads[$group] ) ) {
 198                                                 $this->mGroupLoads[$group] = [];
 199                                         }
 200                                         $this->mGroupLoads[$group][$i] = $ratio;
 201                                 }
 202                         }
 203                 }
 204
 205                 if ( isset( $params['srvCache'] ) ) {
 206                         $this->srvCache = $params['srvCache'];
 207                 } else {
 208                         $this->srvCache = new EmptyBagOStuff();
 209                 }
 210                 if ( isset( $params['wanCache'] ) ) {
 211                         $this->wanCache = $params['wanCache'];
 212                 } else {
 213                         $this->wanCache = WANObjectCache::newEmpty();
 214                 }
 215                 $this->profiler = isset( $params['profiler'] ) ? $params['profiler'] : null;
 216                 if ( isset( $params['trxProfiler'] ) ) {
 217                         $this->trxProfiler = $params['trxProfiler'];
 218                 } else {
 219                         $this->trxProfiler = new TransactionProfiler();
 220                 }
 221
 222                 $this->errorLogger = isset( $params['errorLogger'] )
 223                         ? $params['errorLogger']
 224                         : function ( Exception $e ) {
 225                                 trigger_error( get_class( $e ) . ': ' . $e->getMessage(), E_USER_WARNING );
 226                         };
 227
 228                 foreach ( [ 'replLogger', 'connLogger', 'queryLogger', 'perfLogger' ] as $key ) {
 229                         $this->$key = isset( $params[$key] ) ? $params[$key] : new NullLogger();
 230                 }
 231
 232                 $this->host = isset( $params['hostname'] )
 233                         ? $params['hostname']
 234                         : ( gethostname() ?: 'unknown' );
 235                 $this->cliMode = isset( $params['cliMode'] ) ? $params['cliMode'] : PHP_SAPI === 'cli';
 236                 $this->agent = isset( $params['agent'] ) ? $params['agent'] : '';
 237
 238                 if ( isset( $params['chronologyProtector'] ) ) {
 239                         $this->chronProt = $params['chronologyProtector'];
 240                 }
 241         }
 242
 243         /**
 244          * Get a LoadMonitor instance
 245          *
 246          * @return ILoadMonitor
 247          */
 248         private function getLoadMonitor() {
 249                 if ( !isset( $this->loadMonitor ) ) {
 250                         $compat = [
 251                                 'LoadMonitor' => LoadMonitor::class,
 252                                 'LoadMonitorNull' => LoadMonitorNull::class,
 253                                 'LoadMonitorMySQL' => LoadMonitorMySQL::class,
 254                         ];
 255
 256                         $class = $this->loadMonitorConfig['class'];
 257                         if ( isset( $compat[$class] ) ) {
 258                                 $class = $compat[$class];
 259                         }
 260
 261                         $this->loadMonitor = new $class(
 262                                 $this, $this->srvCache, $this->wanCache, $this->loadMonitorConfig );
 263                         $this->loadMonitor->setLogger( $this->replLogger );
 264                 }
 265
 266                 return $this->loadMonitor;
 267         }
 268
 269         /**
 270          * @param array $loads
 271          * @param bool|string $domain Domain to get non-lagged for
 272          * @param int $maxLag Restrict the maximum allowed lag to this many seconds
 273          * @return bool|int|string
 274          */
 275         private function getRandomNonLagged( array $loads, $domain = false, $maxLag = INF ) {
 276                 $lags = $this->getLagTimes( $domain );
 277
 278                 # Unset excessively lagged servers
 279                 foreach ( $lags as $i => $lag ) {
 280                         if ( $i != 0 ) {
 281                                 # How much lag this server nominally is allowed to have
 282                                 $maxServerLag = isset( $this->mServers[$i]['max lag'] )
 283                                         ? $this->mServers[$i]['max lag']
 284                                         : $this->maxLag; // default
 285                                 # Constrain that futher by $maxLag argument
 286                                 $maxServerLag = min( $maxServerLag, $maxLag );
 287
 288                                 $host = $this->getServerName( $i );
 289                                 if ( $lag === false && !is_infinite( $maxServerLag ) ) {
 290                                         $this->replLogger->error(
 291                                                 "Server {host} is not replicating?", [ 'host' => $host ] );
 292                                         unset( $loads[$i] );
 293                                 } elseif ( $lag > $maxServerLag ) {
 294                                         $this->replLogger->info(
 295                                                 "Server {host} has {lag} seconds of lag (>= {maxlag})",
 296                                                 [ 'host' => $host, 'lag' => $lag, 'maxlag' => $maxServerLag ]
 297                                         );
 298                                         unset( $loads[$i] );
 299                                 }
 300                         }
 301                 }
 302
 303                 # Find out if all the replica DBs with non-zero load are lagged
 304                 $sum = 0;
 305                 foreach ( $loads as $load ) {
 306                         $sum += $load;
 307                 }
 308                 if ( $sum == 0 ) {
 309                         # No appropriate DB servers except maybe the master and some replica DBs with zero load
 310                         # Do NOT use the master
 311                         # Instead, this function will return false, triggering read-only mode,
 312                         # and a lagged replica DB will be used instead.
 313                         return false;
 314                 }
 315
 316                 if ( count( $loads ) == 0 ) {
 317                         return false;
 318                 }
 319
 320                 # Return a random representative of the remainder
 321                 return ArrayUtils::pickRandom( $loads );
 322         }
 323
 324         public function getReaderIndex( $group = false, $domain = false ) {
 325                 if ( count( $this->mServers ) == 1 ) {
 326                         // Skip the load balancing if there's only one server
 327                         return $this->getWriterIndex();
 328                 } elseif ( $group === false && $this->mReadIndex >= 0 ) {
 329                         // Shortcut if the generic reader index was already cached
 330                         return $this->mReadIndex;
 331                 }
 332
 333                 if ( $group !== false ) {
 334                         // Use the server weight array for this load group
 335                         if ( isset( $this->mGroupLoads[$group] ) ) {
 336                                 $loads = $this->mGroupLoads[$group];
 337                         } else {
 338                                 // No loads for this group, return false and the caller can use some other group
 339                                 $this->connLogger->info( __METHOD__ . ": no loads for group $group" );
 340
 341                                 return false;
 342                         }
 343                 } else {
 344                         // Use the generic load group
 345                         $loads = $this->mLoads;
 346                 }
 347
 348                 // Scale the configured load ratios according to each server's load and state
 349                 $this->getLoadMonitor()->scaleLoads( $loads, $domain );
 350
 351                 // Pick a server to use, accounting for weights, load, lag, and mWaitForPos
 352                 list( $i, $laggedReplicaMode ) = $this->pickReaderIndex( $loads, $domain );
 353                 if ( $i === false ) {
 354                         // Replica DB connection unsuccessful
 355                         return false;
 356                 }
 357
 358                 if ( $this->mWaitForPos && $i != $this->getWriterIndex() ) {
 359                         // Before any data queries are run, wait for the server to catch up to the
 360                         // specified position. This is used to improve session consistency. Note that
 361                         // when LoadBalancer::waitFor() sets mWaitForPos, the waiting triggers here,
 362                         // so update laggedReplicaMode as needed for consistency.
 363                         if ( !$this->doWait( $i ) ) {
 364                                 $laggedReplicaMode = true;
 365                         }
 366                 }
 367
 368                 if ( $this->mReadIndex <= 0 && $this->mLoads[$i] > 0 && $group === false ) {
 369                         // Cache the generic reader index for future ungrouped DB_REPLICA handles
 370                         $this->mReadIndex = $i;
 371                         // Record if the generic reader index is in "lagged replica DB" mode
 372                         if ( $laggedReplicaMode ) {
 373                                 $this->laggedReplicaMode = true;
 374                         }
 375                 }
 376
 377                 $serverName = $this->getServerName( $i );
 378                 $this->connLogger->debug( __METHOD__ . ": using server $serverName for group '$group'" );
 379
 380                 return $i;
 381         }
 382
 383         /**
 384          * @param array $loads List of server weights
 385          * @param string|bool $domain
 386          * @return array (reader index, lagged replica mode) or false on failure
 387          */
 388         private function pickReaderIndex( array $loads, $domain = false ) {
 389                 if ( !count( $loads ) ) {
 390                         throw new InvalidArgumentException( "Empty server array given to LoadBalancer" );
 391                 }
 392
 393                 /** @var int|bool $i Index of selected server */
 394                 $i = false;
 395                 /** @var bool $laggedReplicaMode Whether server is considered lagged */
 396                 $laggedReplicaMode = false;
 397
 398                 // Quickly look through the available servers for a server that meets criteria...
 399                 $currentLoads = $loads;
 400                 while ( count( $currentLoads ) ) {
 401                         if ( $this->mAllowLagged || $laggedReplicaMode ) {
 402                                 $i = ArrayUtils::pickRandom( $currentLoads );
 403                         } else {
 404                                 $i = false;
 405                                 if ( $this->mWaitForPos && $this->mWaitForPos->asOfTime() ) {
 406                                         // ChronologyProtecter sets mWaitForPos for session consistency.
 407                                         // This triggers doWait() after connect, so it's especially good to
 408                                         // avoid lagged servers so as to avoid excessive delay in that method.
 409                                         $ago = microtime( true ) - $this->mWaitForPos->asOfTime();
 410                                         // Aim for <= 1 second of waiting (being too picky can backfire)
 411                                         $i = $this->getRandomNonLagged( $currentLoads, $domain, $ago + 1 );
 412                                 }
 413                                 if ( $i === false ) {
 414                                         // Any server with less lag than it's 'max lag' param is preferable
 415                                         $i = $this->getRandomNonLagged( $currentLoads, $domain );
 416                                 }
 417                                 if ( $i === false && count( $currentLoads ) != 0 ) {
 418                                         // All replica DBs lagged. Switch to read-only mode
 419                                         $this->replLogger->error( "All replica DBs lagged. Switch to read-only mode" );
 420                                         $i = ArrayUtils::pickRandom( $currentLoads );
 421                                         $laggedReplicaMode = true;
 422                                 }
 423                         }
 424
 425                         if ( $i === false ) {
 426                                 // pickRandom() returned false.
 427                                 // This is permanent and means the configuration or the load monitor
 428                                 // wants us to return false.
 429                                 $this->connLogger->debug( __METHOD__ . ": pickRandom() returned false" );
 430
 431                                 return [ false, false ];
 432                         }
 433
 434                         $serverName = $this->getServerName( $i );
 435                         $this->connLogger->debug( __METHOD__ . ": Using reader #$i: $serverName..." );
 436
 437                         $conn = $this->openConnection( $i, $domain );
 438                         if ( !$conn ) {
 439                                 $this->connLogger->warning( __METHOD__ . ": Failed connecting to $i/$domain" );
 440                                 unset( $currentLoads[$i] ); // avoid this server next iteration
 441                                 $i = false;
 442                                 continue;
 443                         }
 444
 445                         // Decrement reference counter, we are finished with this connection.
 446                         // It will be incremented for the caller later.
 447                         if ( $domain !== false ) {
 448                                 $this->reuseConnection( $conn );
 449                         }
 450
 451                         // Return this server
 452                         break;
 453                 }
 454
 455                 // If all servers were down, quit now
 456                 if ( !count( $currentLoads ) ) {
 457                         $this->connLogger->error( "All servers down" );
 458                 }
 459
 460                 return [ $i, $laggedReplicaMode ];
 461         }
 462
 463         public function waitFor( $pos ) {
 464                 $oldPos = $this->mWaitForPos;
 465                 try {
 466                         $this->mWaitForPos = $pos;
 467                         // If a generic reader connection was already established, then wait now
 468                         $i = $this->mReadIndex;
 469                         if ( $i > 0 ) {
 470                                 if ( !$this->doWait( $i ) ) {
 471                                         $this->laggedReplicaMode = true;
 472                                 }
 473                         }
 474                 } finally {
 475                         // Restore the older position if it was higher since this is used for lag-protection
 476                         $this->setWaitForPositionIfHigher( $oldPos );
 477                 }
 478         }
 479
 480         public function waitForOne( $pos, $timeout = null ) {
 481                 $oldPos = $this->mWaitForPos;
 482                 try {
 483                         $this->mWaitForPos = $pos;
 484
 485                         $i = $this->mReadIndex;
 486                         if ( $i <= 0 ) {
 487                                 // Pick a generic replica DB if there isn't one yet
 488                                 $readLoads = $this->mLoads;
 489                                 unset( $readLoads[$this->getWriterIndex()] ); // replica DBs only
 490                                 $readLoads = array_filter( $readLoads ); // with non-zero load
 491                                 $i = ArrayUtils::pickRandom( $readLoads );
 492                         }
 493
 494                         if ( $i > 0 ) {
 495                                 $ok = $this->doWait( $i, true, $timeout );
 496                         } else {
 497                                 $ok = true; // no applicable loads
 498                         }
 499                 } finally {
 500                         # Restore the old position, as this is not used for lag-protection but for throttling
 501                         $this->mWaitForPos = $oldPos;
 502                 }
 503
 504                 return $ok;
 505         }
 506
 507         public function waitForAll( $pos, $timeout = null ) {
 508                 $oldPos = $this->mWaitForPos;
 509                 try {
 510                         $this->mWaitForPos = $pos;
 511                         $serverCount = count( $this->mServers );
 512
 513                         $ok = true;
 514                         for ( $i = 1; $i < $serverCount; $i++ ) {
 515                                 if ( $this->mLoads[$i] > 0 ) {
 516                                         $ok = $this->doWait( $i, true, $timeout ) && $ok;
 517                                 }
 518                         }
 519                 } finally {
 520                         # Restore the old position, as this is not used for lag-protection but for throttling
 521                         $this->mWaitForPos = $oldPos;
 522                 }
 523
 524                 return $ok;
 525         }
 526
 527         /**
 528          * @param DBMasterPos|bool $pos
 529          */
 530         private function setWaitForPositionIfHigher( $pos ) {
 531                 if ( !$pos ) {
 532                         return;
 533                 }
 534
 535                 if ( !$this->mWaitForPos || $pos->hasReached( $this->mWaitForPos ) ) {
 536                         $this->mWaitForPos = $pos;
 537                 }
 538         }
 539
 540         /**
 541          * @param int $i
 542          * @return IDatabase|bool
 543          */
 544         public function getAnyOpenConnection( $i ) {
 545                 foreach ( $this->mConns as $connsByServer ) {
 546                         if ( !empty( $connsByServer[$i] ) ) {
 547                                 /** @var IDatabase[] $serverConns */
 548                                 $serverConns = $connsByServer[$i];
 549
 550                                 return reset( $serverConns );
 551                         }
 552                 }
 553
 554                 return false;
 555         }
 556
 557         /**
 558          * Wait for a given replica DB to catch up to the master pos stored in $this
 559          * @param int $index Server index
 560          * @param bool $open Check the server even if a new connection has to be made
 561          * @param int $timeout Max seconds to wait; default is mWaitTimeout
 562          * @return bool
 563          */
 564         protected function doWait( $index, $open = false, $timeout = null ) {
 565                 $close = false; // close the connection afterwards
 566
 567                 // Check if we already know that the DB has reached this point
 568                 $server = $this->getServerName( $index );
 569                 $key = $this->srvCache->makeGlobalKey( __CLASS__, 'last-known-pos', $server, 'v1' );
 570                 /** @var DBMasterPos $knownReachedPos */
 571                 $knownReachedPos = $this->srvCache->get( $key );
 572                 if (
 573                         $knownReachedPos instanceof DBMasterPos &&
 574                         $knownReachedPos->hasReached( $this->mWaitForPos )
 575                 ) {
 576                         $this->replLogger->debug( __METHOD__ .
 577                                 ': replica DB {dbserver} known to be caught up (pos >= $knownReachedPos).',
 578                                 [ 'dbserver' => $server ] );
 579                         return true;
 580                 }
 581
 582                 // Find a connection to wait on, creating one if needed and allowed
 583                 $conn = $this->getAnyOpenConnection( $index );
 584                 if ( !$conn ) {
 585                         if ( !$open ) {
 586                                 $this->replLogger->debug( __METHOD__ . ': no connection open for {dbserver}',
 587                                         [ 'dbserver' => $server ] );
 588
 589                                 return false;
 590                         } else {
 591                                 $conn = $this->openConnection( $index, self::DOMAIN_ANY );
 592                                 if ( !$conn ) {
 593                                         $this->replLogger->warning( __METHOD__ . ': failed to connect to {dbserver}',
 594                                                 [ 'dbserver' => $server ] );
 595
 596                                         return false;
 597                                 }
 598                                 // Avoid connection spam in waitForAll() when connections
 599                                 // are made just for the sake of doing this lag check.
 600                                 $close = true;
 601                         }
 602                 }
 603
 604                 $this->replLogger->info( __METHOD__ . ': Waiting for replica DB {dbserver} to catch up...',
 605                         [ 'dbserver' => $server ] );
 606                 $timeout = $timeout ?: $this->mWaitTimeout;
 607                 $result = $conn->masterPosWait( $this->mWaitForPos, $timeout );
 608
 609                 if ( $result == -1 || is_null( $result ) ) {
 610                         // Timed out waiting for replica DB, use master instead
 611                         $this->replLogger->warning(
 612                                 __METHOD__ . ': Timed out waiting on {host} pos {pos}',
 613                                 [ 'host' => $server, 'pos' => $this->mWaitForPos ]
 614                         );
 615                         $ok = false;
 616                 } else {
 617                         $this->replLogger->info( __METHOD__ . ": Done" );
 618                         $ok = true;
 619                         // Remember that the DB reached this point
 620                         $this->srvCache->set( $key, $this->mWaitForPos, BagOStuff::TTL_DAY );
 621                 }
 622
 623                 if ( $close ) {
 624                         $this->closeConnection( $conn );
 625                 }
 626
 627                 return $ok;
 628         }
 629
 630         public function getConnection( $i, $groups = [], $domain = false, $flags = 0 ) {
 631                 if ( $i === null || $i === false ) {
 632                         throw new InvalidArgumentException( 'Attempt to call ' . __METHOD__ .
 633                                 ' with invalid server index' );
 634                 }
 635
 636                 if ( $this->localDomain->equals( $domain ) || $domain === $this->localDomainIdAlias ) {
 637                         $domain = false; // local connection requested
 638                 }
 639
 640                 $groups = ( $groups === false || $groups === [] )
 641                         ? [ false ] // check one "group": the generic pool
 642                         : (array)$groups;
 643
 644                 $masterOnly = ( $i == self::DB_MASTER || $i == $this->getWriterIndex() );
 645                 $oldConnsOpened = $this->connsOpened; // connections open now
 646
 647                 if ( $i == self::DB_MASTER ) {
 648                         $i = $this->getWriterIndex();
 649                 } else {
 650                         # Try to find an available server in any the query groups (in order)
 651                         foreach ( $groups as $group ) {
 652                                 $groupIndex = $this->getReaderIndex( $group, $domain );
 653                                 if ( $groupIndex !== false ) {
 654                                         $i = $groupIndex;
 655                                         break;
 656                                 }
 657                         }
 658                 }
 659
 660                 # Operation-based index
 661                 if ( $i == self::DB_REPLICA ) {
 662                         $this->mLastError = 'Unknown error'; // reset error string
 663                         # Try the general server pool if $groups are unavailable.
 664                         $i = ( $groups === [ false ] )
 665                                 ? false // don't bother with this if that is what was tried above
 666                                 : $this->getReaderIndex( false, $domain );
 667                         # Couldn't find a working server in getReaderIndex()?
 668                         if ( $i === false ) {
 669                                 $this->mLastError = 'No working replica DB server: ' . $this->mLastError;
 670                                 // Throw an exception
 671                                 $this->reportConnectionError();
 672                                 return null; // not reached
 673                         }
 674                 }
 675
 676                 # Now we have an explicit index into the servers array
 677                 $conn = $this->openConnection( $i, $domain, $flags );
 678                 if ( !$conn ) {
 679                         // Throw an exception
 680                         $this->reportConnectionError();
 681                         return null; // not reached
 682                 }
 683
 684                 # Profile any new connections that happen
 685                 if ( $this->connsOpened > $oldConnsOpened ) {
 686                         $host = $conn->getServer();
 687                         $dbname = $conn->getDBname();
 688                         $this->trxProfiler->recordConnection( $host, $dbname, $masterOnly );
 689                 }
 690
 691                 if ( $masterOnly ) {
 692                         # Make master-requested DB handles inherit any read-only mode setting
 693                         $conn->setLBInfo( 'readOnlyReason', $this->getReadOnlyReason( $domain, $conn ) );
 694                 }
 695
 696                 return $conn;
 697         }
 698
 699         public function reuseConnection( $conn ) {
 700                 $serverIndex = $conn->getLBInfo( 'serverIndex' );
 701                 $refCount = $conn->getLBInfo( 'foreignPoolRefCount' );
 702                 if ( $serverIndex === null || $refCount === null ) {
 703                         /**
 704                          * This can happen in code like:
 705                          *   foreach ( $dbs as $db ) {
 706                          *     $conn = $lb->getConnection( $lb::DB_REPLICA, [], $db );
 707                          *     ...
 708                          *     $lb->reuseConnection( $conn );
 709                          *   }
 710                          * When a connection to the local DB is opened in this way, reuseConnection()
 711                          * should be ignored
 712                          */
 713                         return;
 714                 } elseif ( $conn instanceof DBConnRef ) {
 715                         // DBConnRef already handles calling reuseConnection() and only passes the live
 716                         // Database instance to this method. Any caller passing in a DBConnRef is broken.
 717                         $this->connLogger->error( __METHOD__ . ": got DBConnRef instance.\n" .
 718                                 ( new RuntimeException() )->getTraceAsString() );
 719
 720                         return;
 721                 }
 722
 723                 if ( $this->disabled ) {
 724                         return; // DBConnRef handle probably survived longer than the LoadBalancer
 725                 }
 726
 727                 if ( $conn->getLBInfo( 'autoCommitOnly' ) ) {
 728                         $connFreeKey = self::KEY_FOREIGN_FREE_NOROUND;
 729                         $connInUseKey = self::KEY_FOREIGN_INUSE_NOROUND;
 730                 } else {
 731                         $connFreeKey = self::KEY_FOREIGN_FREE;
 732                         $connInUseKey = self::KEY_FOREIGN_INUSE;
 733                 }
 734
 735                 $domain = $conn->getDomainID();
 736                 if ( !isset( $this->mConns[$connInUseKey][$serverIndex][$domain] ) ) {
 737                         throw new InvalidArgumentException( __METHOD__ .
 738                                 ": connection $serverIndex/$domain not found; it may have already been freed." );
 739                 } elseif ( $this->mConns[$connInUseKey][$serverIndex][$domain] !== $conn ) {
 740                         throw new InvalidArgumentException( __METHOD__ .
 741                                 ": connection $serverIndex/$domain mismatched; it may have already been freed." );
 742                 }
 743
 744                 $conn->setLBInfo( 'foreignPoolRefCount', --$refCount );
 745                 if ( $refCount <= 0 ) {
 746                         $this->mConns[$connFreeKey][$serverIndex][$domain] = $conn;
 747                         unset( $this->mConns[$connInUseKey][$serverIndex][$domain] );
 748                         if ( !$this->mConns[$connInUseKey][$serverIndex] ) {
 749                                 unset( $this->mConns[$connInUseKey][$serverIndex] ); // clean up
 750                         }
 751                         $this->connLogger->debug( __METHOD__ . ": freed connection $serverIndex/$domain" );
 752                 } else {
 753                         $this->connLogger->debug( __METHOD__ .
 754                                 ": reference count for $serverIndex/$domain reduced to $refCount" );
 755                 }
 756         }
 757
 758         public function getConnectionRef( $db, $groups = [], $domain = false, $flags = 0 ) {
 759                 $domain = ( $domain !== false ) ? $domain : $this->localDomain;
 760
 761                 return new DBConnRef( $this, $this->getConnection( $db, $groups, $domain, $flags ) );
 762         }
 763
 764         public function getLazyConnectionRef( $db, $groups = [], $domain = false, $flags = 0 ) {
 765                 $domain = ( $domain !== false ) ? $domain : $this->localDomain;
 766
 767                 return new DBConnRef( $this, [ $db, $groups, $domain, $flags ] );
 768         }
 769
 770         public function getMaintenanceConnectionRef( $db, $groups = [], $domain = false, $flags = 0 ) {
 771                 $domain = ( $domain !== false ) ? $domain : $this->localDomain;
 772
 773                 return new MaintainableDBConnRef(
 774                         $this, $this->getConnection( $db, $groups, $domain, $flags ) );
 775         }
 776
 777         public function openConnection( $i, $domain = false, $flags = 0 ) {
 778                 if ( $this->localDomain->equals( $domain ) || $domain === $this->localDomainIdAlias ) {
 779                         $domain = false; // local connection requested
 780                 }
 781
 782                 if ( !$this->chronProtInitialized && $this->chronProt ) {
 783                         $this->connLogger->debug( __METHOD__ . ': calling initLB() before first connection.' );
 784                         // Load CP positions before connecting so that doWait() triggers later if needed
 785                         $this->chronProtInitialized = true;
 786                         $this->chronProt->initLB( $this );
 787                 }
 788
 789                 // Check if an auto-commit connection is being requested. If so, it will not reuse the
 790                 // main set of DB connections but rather its own pool since:
 791                 // a) those are usually set to implicitly use transaction rounds via DBO_TRX
 792                 // b) those must support the use of explicit transaction rounds via beginMasterChanges()
 793                 $autoCommit = ( ( $flags & self::CONN_TRX_AUTO ) == self::CONN_TRX_AUTO );
 794
 795                 if ( $domain !== false ) {
 796                         // Connection is to a foreign domain
 797                         $conn = $this->openForeignConnection( $i, $domain, $flags );
 798                 } else {
 799                         // Connection is to the local domain
 800                         $connKey = $autoCommit ? self::KEY_LOCAL_NOROUND : self::KEY_LOCAL;
 801                         if ( isset( $this->mConns[$connKey][$i][0] ) ) {
 802                                 $conn = $this->mConns[$connKey][$i][0];
 803                         } else {
 804                                 if ( !isset( $this->mServers[$i] ) || !is_array( $this->mServers[$i] ) ) {
 805                                         throw new InvalidArgumentException( "No server with index '$i'." );
 806                                 }
 807                                 // Open a new connection
 808                                 $server = $this->mServers[$i];
 809                                 $server['serverIndex'] = $i;
 810                                 $server['autoCommitOnly'] = $autoCommit;
 811                                 $conn = $this->reallyOpenConnection( $server, false );
 812                                 $host = $this->getServerName( $i );
 813                                 if ( $conn->isOpen() ) {
 814                                         $this->connLogger->debug( "Connected to database $i at '$host'." );
 815                                         $this->mConns[$connKey][$i][0] = $conn;
 816                                 } else {
 817                                         $this->connLogger->warning( "Failed to connect to database $i at '$host'." );
 818                                         $this->errorConnection = $conn;
 819                                         $conn = false;
 820                                 }
 821                         }
 822                 }
 823
 824                 if ( $conn instanceof IDatabase && !$conn->isOpen() ) {
 825                         // Connection was made but later unrecoverably lost for some reason.
 826                         // Do not return a handle that will just throw exceptions on use,
 827                         // but let the calling code (e.g. getReaderIndex) try another server.
 828                         // See DatabaseMyslBase::ping() for how this can happen.
 829                         $this->errorConnection = $conn;
 830                         $conn = false;
 831                 }
 832
 833                 if ( $autoCommit && $conn instanceof IDatabase ) {
 834                         $conn->clearFlag( $conn::DBO_TRX ); // auto-commit mode
 835                 }
 836
 837                 return $conn;
 838         }
 839
 840         /**
 841          * Open a connection to a foreign DB, or return one if it is already open.
 842          *
 843          * Increments a reference count on the returned connection which locks the
 844          * connection to the requested domain. This reference count can be
 845          * decremented by calling reuseConnection().
 846          *
 847          * If a connection is open to the appropriate server already, but with the wrong
 848          * database, it will be switched to the right database and returned, as long as
 849          * it has been freed first with reuseConnection().
 850          *
 851          * On error, returns false, and the connection which caused the
 852          * error will be available via $this->errorConnection.
 853          *
 854          * @note If disable() was called on this LoadBalancer, this method will throw a DBAccessError.
 855          *
 856          * @param int $i Server index
 857          * @param string $domain Domain ID to open
 858          * @param int $flags Class CONN_* constant bitfield
 859          * @return Database
 860          */
 861         private function openForeignConnection( $i, $domain, $flags = 0 ) {
 862                 $domainInstance = DatabaseDomain::newFromId( $domain );
 863                 $dbName = $domainInstance->getDatabase();
 864                 $prefix = $domainInstance->getTablePrefix();
 865                 $autoCommit = ( ( $flags & self::CONN_TRX_AUTO ) == self::CONN_TRX_AUTO );
 866
 867                 if ( $autoCommit ) {
 868                         $connFreeKey = self::KEY_FOREIGN_FREE_NOROUND;
 869                         $connInUseKey = self::KEY_FOREIGN_INUSE_NOROUND;
 870                 } else {
 871                         $connFreeKey = self::KEY_FOREIGN_FREE;
 872                         $connInUseKey = self::KEY_FOREIGN_INUSE;
 873                 }
 874
 875                 if ( isset( $this->mConns[$connInUseKey][$i][$domain] ) ) {
 876                         // Reuse an in-use connection for the same domain
 877                         $conn = $this->mConns[$connInUseKey][$i][$domain];
 878                         $this->connLogger->debug( __METHOD__ . ": reusing connection $i/$domain" );
 879                 } elseif ( isset( $this->mConns[$connFreeKey][$i][$domain] ) ) {
 880                         // Reuse a free connection for the same domain
 881                         $conn = $this->mConns[$connFreeKey][$i][$domain];
 882                         unset( $this->mConns[$connFreeKey][$i][$domain] );
 883                         $this->mConns[$connInUseKey][$i][$domain] = $conn;
 884                         $this->connLogger->debug( __METHOD__ . ": reusing free connection $i/$domain" );
 885                 } elseif ( !empty( $this->mConns[$connFreeKey][$i] ) ) {
 886                         // Reuse a free connection from another domain
 887                         $conn = reset( $this->mConns[$connFreeKey][$i] );
 888                         $oldDomain = key( $this->mConns[$connFreeKey][$i] );
 889                         // The empty string as a DB name means "don't care".
 890                         // DatabaseMysqlBase::open() already handle this on connection.
 891                         if ( strlen( $dbName ) && !$conn->selectDB( $dbName ) ) {
 892                                 $this->mLastError = "Error selecting database '$dbName' on server " .
 893                                         $conn->getServer() . " from client host {$this->host}";
 894                                 $this->errorConnection = $conn;
 895                                 $conn = false;
 896                         } else {
 897                                 $conn->tablePrefix( $prefix );
 898                                 unset( $this->mConns[$connFreeKey][$i][$oldDomain] );
 899                                 $this->mConns[$connInUseKey][$i][$domain] = $conn;
 900                                 $this->connLogger->debug( __METHOD__ .
 901                                         ": reusing free connection from $oldDomain for $domain" );
 902                         }
 903                 } else {
 904                         if ( !isset( $this->mServers[$i] ) || !is_array( $this->mServers[$i] ) ) {
 905                                 throw new InvalidArgumentException( "No server with index '$i'." );
 906                         }
 907                         // Open a new connection
 908                         $server = $this->mServers[$i];
 909                         $server['serverIndex'] = $i;
 910                         $server['foreignPoolRefCount'] = 0;
 911                         $server['foreign'] = true;
 912                         $server['autoCommitOnly'] = $autoCommit;
 913                         $conn = $this->reallyOpenConnection( $server, $dbName );
 914                         if ( !$conn->isOpen() ) {
 915                                 $this->connLogger->warning( __METHOD__ . ": connection error for $i/$domain" );
 916                                 $this->errorConnection = $conn;
 917                                 $conn = false;
 918                         } else {
 919                                 $conn->tablePrefix( $prefix );
 920                                 $this->mConns[$connInUseKey][$i][$domain] = $conn;
 921                                 $this->connLogger->debug( __METHOD__ . ": opened new connection for $i/$domain" );
 922                         }
 923                 }
 924
 925                 // Increment reference count
 926                 if ( $conn instanceof IDatabase ) {
 927                         $refCount = $conn->getLBInfo( 'foreignPoolRefCount' );
 928                         $conn->setLBInfo( 'foreignPoolRefCount', $refCount + 1 );
 929                 }
 930
 931                 return $conn;
 932         }
 933
 934         /**
 935          * Test if the specified index represents an open connection
 936          *
 937          * @param int $index Server index
 938          * @access private
 939          * @return bool
 940          */
 941         private function isOpen( $index ) {
 942                 if ( !is_integer( $index ) ) {
 943                         return false;
 944                 }
 945
 946                 return (bool)$this->getAnyOpenConnection( $index );
 947         }
 948
 949         /**
 950          * Really opens a connection. Uncached.
 951          * Returns a Database object whether or not the connection was successful.
 952          * @access private
 953          *
 954          * @param array $server
 955          * @param string|bool $dbNameOverride Use "" to not select any database
 956          * @return Database
 957          * @throws DBAccessError
 958          * @throws InvalidArgumentException
 959          */
 960         protected function reallyOpenConnection( array $server, $dbNameOverride = false ) {
 961                 if ( $this->disabled ) {
 962                         throw new DBAccessError();
 963                 }
 964
 965                 if ( $dbNameOverride !== false ) {
 966                         $server['dbname'] = $dbNameOverride;
 967                 }
 968
 969                 // Let the handle know what the cluster master is (e.g. "db1052")
 970                 $masterName = $this->getServerName( $this->getWriterIndex() );
 971                 $server['clusterMasterHost'] = $masterName;
 972
 973                 // Log when many connection are made on requests
 974                 if ( ++$this->connsOpened >= self::CONN_HELD_WARN_THRESHOLD ) {
 975                         $this->perfLogger->warning( __METHOD__ . ": " .
 976                                 "{$this->connsOpened}+ connections made (master=$masterName)" );
 977                 }
 978
 979                 $server['srvCache'] = $this->srvCache;
 980                 // Set loggers and profilers
 981                 $server['connLogger'] = $this->connLogger;
 982                 $server['queryLogger'] = $this->queryLogger;
 983                 $server['errorLogger'] = $this->errorLogger;
 984                 $server['profiler'] = $this->profiler;
 985                 $server['trxProfiler'] = $this->trxProfiler;
 986                 // Use the same agent and PHP mode for all DB handles
 987                 $server['cliMode'] = $this->cliMode;
 988                 $server['agent'] = $this->agent;
 989                 // Use DBO_DEFAULT flags by default for LoadBalancer managed databases. Assume that the
 990                 // application calls LoadBalancer::commitMasterChanges() before the PHP script completes.
 991                 $server['flags'] = isset( $server['flags'] ) ? $server['flags'] : IDatabase::DBO_DEFAULT;
 992
 993                 // Create a live connection object
 994                 try {
 995                         $db = Database::factory( $server['type'], $server );
 996                 } catch ( DBConnectionError $e ) {
 997                         // FIXME: This is probably the ugliest thing I have ever done to
 998                         // PHP. I'm half-expecting it to segfault, just out of disgust. -- TS
 999                         $db = $e->db;
1000                 }
1001
1002                 $db->setLBInfo( $server );
1003                 $db->setLazyMasterHandle(
1004                         $this->getLazyConnectionRef( self::DB_MASTER, [], $db->getDomainID() )
1005                 );
1006                 $db->setTableAliases( $this->tableAliases );
1007
1008                 if ( $server['serverIndex'] === $this->getWriterIndex() ) {
1009                         if ( $this->trxRoundId !== false ) {
1010                                 $this->applyTransactionRoundFlags( $db );
1011                         }
1012                         foreach ( $this->trxRecurringCallbacks as $name => $callback ) {
1013                                 $db->setTransactionListener( $name, $callback );
1014                         }
1015                 }
1016
1017                 return $db;
1018         }
1019
1020         /**
1021          * @throws DBConnectionError
1022          */
1023         private function reportConnectionError() {
1024                 $conn = $this->errorConnection; // the connection which caused the error
1025                 $context = [
1026                         'method' => __METHOD__,
1027                         'last_error' => $this->mLastError,
1028                 ];
1029
1030                 if ( $conn instanceof IDatabase ) {
1031                         $context['db_server'] = $conn->getServer();
1032                         $this->connLogger->warning(
1033                                 "Connection error: {last_error} ({db_server})",
1034                                 $context
1035                         );
1036
1037                         // throws DBConnectionError
1038                         $conn->reportConnectionError( "{$this->mLastError} ({$context['db_server']})" );
1039                 } else {
1040                         // No last connection, probably due to all servers being too busy
1041                         $this->connLogger->error(
1042                                 "LB failure with no last connection. Connection error: {last_error}",
1043                                 $context
1044                         );
1045
1046                         // If all servers were busy, mLastError will contain something sensible
1047                         throw new DBConnectionError( null, $this->mLastError );
1048                 }
1049         }
1050
1051         public function getWriterIndex() {
1052                 return 0;
1053         }
1054
1055         public function haveIndex( $i ) {
1056                 return array_key_exists( $i, $this->mServers );
1057         }
1058
1059         public function isNonZeroLoad( $i ) {
1060                 return array_key_exists( $i, $this->mServers ) && $this->mLoads[$i] != 0;
1061         }
1062
1063         public function getServerCount() {
1064                 return count( $this->mServers );
1065         }
1066
1067         public function getServerName( $i ) {
1068                 if ( isset( $this->mServers[$i]['hostName'] ) ) {
1069                         $name = $this->mServers[$i]['hostName'];
1070                 } elseif ( isset( $this->mServers[$i]['host'] ) ) {
1071                         $name = $this->mServers[$i]['host'];
1072                 } else {
1073                         $name = '';
1074                 }
1075
1076                 return ( $name != '' ) ? $name : 'localhost';
1077         }
1078
1079         public function getServerType( $i ) {
1080                 return isset( $this->mServers[$i]['type'] ) ? $this->mServers[$i]['type'] : 'unknown';
1081         }
1082
1083         /**
1084          * @deprecated Since 1.30, no alternative
1085          */
1086         public function getServerInfo( $i ) {
1087                 wfDeprecated( __METHOD__, '1.30' );
1088                 if ( isset( $this->mServers[$i] ) ) {
1089                         return $this->mServers[$i];
1090                 } else {
1091                         return false;
1092                 }
1093         }
1094
1095         /**
1096          * @deprecated Since 1.30, construct new object
1097          */
1098         public function setServerInfo( $i, array $serverInfo ) {
1099                 wfDeprecated( __METHOD__, '1.30' );
1100                 $this->mServers[$i] = $serverInfo;
1101         }
1102
1103         public function getMasterPos() {
1104                 # If this entire request was served from a replica DB without opening a connection to the
1105                 # master (however unlikely that may be), then we can fetch the position from the replica DB.
1106                 $masterConn = $this->getAnyOpenConnection( $this->getWriterIndex() );
1107                 if ( !$masterConn ) {
1108                         $serverCount = count( $this->mServers );
1109                         for ( $i = 1; $i < $serverCount; $i++ ) {
1110                                 $conn = $this->getAnyOpenConnection( $i );
1111                                 if ( $conn ) {
1112                                         return $conn->getReplicaPos();
1113                                 }
1114                         }
1115                 } else {
1116                         return $masterConn->getMasterPos();
1117                 }
1118
1119                 return false;
1120         }
1121
1122         public function disable() {
1123                 $this->closeAll();
1124                 $this->disabled = true;
1125         }
1126
1127         public function closeAll() {
1128                 $this->forEachOpenConnection( function ( IDatabase $conn ) {
1129                         $host = $conn->getServer();
1130                         $this->connLogger->debug( "Closing connection to database '$host'." );
1131                         $conn->close();
1132                 } );
1133
1134                 $this->mConns = [
1135                         self::KEY_LOCAL => [],
1136                         self::KEY_FOREIGN_INUSE => [],
1137                         self::KEY_FOREIGN_FREE => [],
1138                         self::KEY_LOCAL_NOROUND => [],
1139                         self::KEY_FOREIGN_INUSE_NOROUND => [],
1140                         self::KEY_FOREIGN_FREE_NOROUND => []
1141                 ];
1142                 $this->connsOpened = 0;
1143         }
1144
1145         public function closeConnection( IDatabase $conn ) {
1146                 $serverIndex = $conn->getLBInfo( 'serverIndex' ); // second index level of mConns
1147                 foreach ( $this->mConns as $type => $connsByServer ) {
1148                         if ( !isset( $connsByServer[$serverIndex] ) ) {
1149                                 continue;
1150                         }
1151
1152                         foreach ( $connsByServer[$serverIndex] as $i => $trackedConn ) {
1153                                 if ( $conn === $trackedConn ) {
1154                                         $host = $this->getServerName( $i );
1155                                         $this->connLogger->debug( "Closing connection to database $i at '$host'." );
1156                                         unset( $this->mConns[$type][$serverIndex][$i] );
1157                                         --$this->connsOpened;
1158                                         break 2;
1159                                 }
1160                         }
1161                 }
1162
1163                 $conn->close();
1164         }
1165
1166         public function commitAll( $fname = __METHOD__ ) {
1167                 $failures = [];
1168
1169                 $restore = ( $this->trxRoundId !== false );
1170                 $this->trxRoundId = false;
1171                 $this->forEachOpenConnection(
1172                         function ( IDatabase $conn ) use ( $fname, $restore, &$failures ) {
1173                                 try {
1174                                         $conn->commit( $fname, $conn::FLUSHING_ALL_PEERS );
1175                                 } catch ( DBError $e ) {
1176                                         call_user_func( $this->errorLogger, $e );
1177                                         $failures[] = "{$conn->getServer()}: {$e->getMessage()}";
1178                                 }
1179                                 if ( $restore && $conn->getLBInfo( 'master' ) ) {
1180                                         $this->undoTransactionRoundFlags( $conn );
1181                                 }
1182                         }
1183                 );
1184
1185                 if ( $failures ) {
1186                         throw new DBExpectedError(
1187                                 null,
1188                                 "Commit failed on server(s) " . implode( "\n", array_unique( $failures ) )
1189                         );
1190                 }
1191         }
1192
1193         public function finalizeMasterChanges() {
1194                 $this->forEachOpenMasterConnection( function ( Database $conn ) {
1195                         // Any error should cause all DB transactions to be rolled back together
1196                         $conn->setTrxEndCallbackSuppression( false );
1197                         $conn->runOnTransactionPreCommitCallbacks();
1198                         // Defer post-commit callbacks until COMMIT finishes for all DBs
1199                         $conn->setTrxEndCallbackSuppression( true );
1200                 } );
1201         }
1202
1203         public function approveMasterChanges( array $options ) {
1204                 $limit = isset( $options['maxWriteDuration'] ) ? $options['maxWriteDuration'] : 0;
1205                 $this->forEachOpenMasterConnection( function ( IDatabase $conn ) use ( $limit ) {
1206                         // If atomic sections or explicit transactions are still open, some caller must have
1207                         // caught an exception but failed to properly rollback any changes. Detect that and
1208                         // throw and error (causing rollback).
1209                         if ( $conn->explicitTrxActive() ) {
1210                                 throw new DBTransactionError(
1211                                         $conn,
1212                                         "Explicit transaction still active. A caller may have caught an error."
1213                                 );
1214                         }
1215                         // Assert that the time to replicate the transaction will be sane.
1216                         // If this fails, then all DB transactions will be rollback back together.
1217                         $time = $conn->pendingWriteQueryDuration( $conn::ESTIMATE_DB_APPLY );
1218                         if ( $limit > 0 && $time > $limit ) {
1219                                 throw new DBTransactionSizeError(
1220                                         $conn,
1221                                         "Transaction spent $time second(s) in writes, exceeding the limit of $limit.",
1222                                         [ $time, $limit ]
1223                                 );
1224                         }
1225                         // If a connection sits idle while slow queries execute on another, that connection
1226                         // may end up dropped before the commit round is reached. Ping servers to detect this.
1227                         if ( $conn->writesOrCallbacksPending() && !$conn->ping() ) {
1228                                 throw new DBTransactionError(
1229                                         $conn,
1230                                         "A connection to the {$conn->getDBname()} database was lost before commit."
1231                                 );
1232                         }
1233                 } );
1234         }
1235
1236         public function beginMasterChanges( $fname = __METHOD__ ) {
1237                 if ( $this->trxRoundId !== false ) {
1238                         throw new DBTransactionError(
1239                                 null,
1240                                 "$fname: Transaction round '{$this->trxRoundId}' already started."
1241                         );
1242                 }
1243                 $this->trxRoundId = $fname;
1244
1245                 $failures = [];
1246                 $this->forEachOpenMasterConnection(
1247                         function ( Database $conn ) use ( $fname, &$failures ) {
1248                                 $conn->setTrxEndCallbackSuppression( true );
1249                                 try {
1250                                         $conn->flushSnapshot( $fname );
1251                                 } catch ( DBError $e ) {
1252                                         call_user_func( $this->errorLogger, $e );
1253                                         $failures[] = "{$conn->getServer()}: {$e->getMessage()}";
1254                                 }
1255                                 $conn->setTrxEndCallbackSuppression( false );
1256                                 $this->applyTransactionRoundFlags( $conn );
1257                         }
1258                 );
1259
1260                 if ( $failures ) {
1261                         throw new DBExpectedError(
1262                                 null,
1263                                 "$fname: Flush failed on server(s) " . implode( "\n", array_unique( $failures ) )
1264                         );
1265                 }
1266         }
1267
1268         public function commitMasterChanges( $fname = __METHOD__ ) {
1269                 $failures = [];
1270
1271                 /** @noinspection PhpUnusedLocalVariableInspection */
1272                 $scope = $this->getScopedPHPBehaviorForCommit(); // try to ignore client aborts
1273
1274                 $restore = ( $this->trxRoundId !== false );
1275                 $this->trxRoundId = false;
1276                 $this->forEachOpenMasterConnection(
1277                         function ( IDatabase $conn ) use ( $fname, $restore, &$failures ) {
1278                                 try {
1279                                         if ( $conn->writesOrCallbacksPending() ) {
1280                                                 $conn->commit( $fname, $conn::FLUSHING_ALL_PEERS );
1281                                         } elseif ( $restore ) {
1282                                                 $conn->flushSnapshot( $fname );
1283                                         }
1284                                 } catch ( DBError $e ) {
1285                                         call_user_func( $this->errorLogger, $e );
1286                                         $failures[] = "{$conn->getServer()}: {$e->getMessage()}";
1287                                 }
1288                                 if ( $restore ) {
1289                                         $this->undoTransactionRoundFlags( $conn );
1290                                 }
1291                         }
1292                 );
1293
1294                 if ( $failures ) {
1295                         throw new DBExpectedError(
1296                                 null,
1297                                 "$fname: Commit failed on server(s) " . implode( "\n", array_unique( $failures ) )
1298                         );
1299                 }
1300         }
1301
1302         public function runMasterPostTrxCallbacks( $type ) {
1303                 $e = null; // first exception
1304                 $this->forEachOpenMasterConnection( function ( Database $conn ) use ( $type, &$e ) {
1305                         $conn->setTrxEndCallbackSuppression( false );
1306                         if ( $conn->writesOrCallbacksPending() ) {
1307                                 // This happens if onTransactionIdle() callbacks leave callbacks on *another* DB
1308                                 // (which finished its callbacks already). Warn and recover in this case. Let the
1309                                 // callbacks run in the final commitMasterChanges() in LBFactory::shutdown().
1310                                 $this->queryLogger->info( __METHOD__ . ": found writes/callbacks pending." );
1311                                 return;
1312                         } elseif ( $conn->trxLevel() ) {
1313                                 // This happens for single-DB setups where DB_REPLICA uses the master DB,
1314                                 // thus leaving an implicit read-only transaction open at this point. It
1315                                 // also happens if onTransactionIdle() callbacks leave implicit transactions
1316                                 // open on *other* DBs (which is slightly improper). Let these COMMIT on the
1317                                 // next call to commitMasterChanges(), possibly in LBFactory::shutdown().
1318                                 return;
1319                         }
1320                         try {
1321                                 $conn->runOnTransactionIdleCallbacks( $type );
1322                         } catch ( Exception $ex ) {
1323                                 $e = $e ?: $ex;
1324                         }
1325                         try {
1326                                 $conn->runTransactionListenerCallbacks( $type );
1327                         } catch ( Exception $ex ) {
1328                                 $e = $e ?: $ex;
1329                         }
1330                 } );
1331
1332                 return $e;
1333         }
1334
1335         public function rollbackMasterChanges( $fname = __METHOD__ ) {
1336                 $restore = ( $this->trxRoundId !== false );
1337                 $this->trxRoundId = false;
1338                 $this->forEachOpenMasterConnection(
1339                         function ( IDatabase $conn ) use ( $fname, $restore ) {
1340                                 if ( $conn->writesOrCallbacksPending() ) {
1341                                         $conn->rollback( $fname, $conn::FLUSHING_ALL_PEERS );
1342                                 }
1343                                 if ( $restore ) {
1344                                         $this->undoTransactionRoundFlags( $conn );
1345                                 }
1346                         }
1347                 );
1348         }
1349
1350         public function suppressTransactionEndCallbacks() {
1351                 $this->forEachOpenMasterConnection( function ( Database $conn ) {
1352                         $conn->setTrxEndCallbackSuppression( true );
1353                 } );
1354         }
1355
1356         /**
1357          * @param IDatabase $conn
1358          */
1359         private function applyTransactionRoundFlags( IDatabase $conn ) {
1360                 if ( $conn->getLBInfo( 'autoCommitOnly' ) ) {
1361                         return; // transaction rounds do not apply to these connections
1362                 }
1363
1364                 if ( $conn->getFlag( $conn::DBO_DEFAULT ) ) {
1365                         // DBO_TRX is controlled entirely by CLI mode presence with DBO_DEFAULT.
1366                         // Force DBO_TRX even in CLI mode since a commit round is expected soon.
1367                         $conn->setFlag( $conn::DBO_TRX, $conn::REMEMBER_PRIOR );
1368                         // If config has explicitly requested DBO_TRX be either on or off by not
1369                         // setting DBO_DEFAULT, then respect that. Forcing no transactions is useful
1370                         // for things like blob stores (ExternalStore) which want auto-commit mode.
1371                 }
1372         }
1373
1374         /**
1375          * @param IDatabase $conn
1376          */
1377         private function undoTransactionRoundFlags( IDatabase $conn ) {
1378                 if ( $conn->getLBInfo( 'autoCommitOnly' ) ) {
1379                         return; // transaction rounds do not apply to these connections
1380                 }
1381
1382                 if ( $conn->getFlag( $conn::DBO_DEFAULT ) ) {
1383                         $conn->restoreFlags( $conn::RESTORE_PRIOR );
1384                 }
1385         }
1386
1387         public function flushReplicaSnapshots( $fname = __METHOD__ ) {
1388                 $this->forEachOpenReplicaConnection( function ( IDatabase $conn ) {
1389                         $conn->flushSnapshot( __METHOD__ );
1390                 } );
1391         }
1392
1393         public function hasMasterConnection() {
1394                 return $this->isOpen( $this->getWriterIndex() );
1395         }
1396
1397         public function hasMasterChanges() {
1398                 $pending = 0;
1399                 $this->forEachOpenMasterConnection( function ( IDatabase $conn ) use ( &$pending ) {
1400                         $pending |= $conn->writesOrCallbacksPending();
1401                 } );
1402
1403                 return (bool)$pending;
1404         }
1405
1406         public function lastMasterChangeTimestamp() {
1407                 $lastTime = false;
1408                 $this->forEachOpenMasterConnection( function ( IDatabase $conn ) use ( &$lastTime ) {
1409                         $lastTime = max( $lastTime, $conn->lastDoneWrites() );
1410                 } );
1411
1412                 return $lastTime;
1413         }
1414
1415         public function hasOrMadeRecentMasterChanges( $age = null ) {
1416                 $age = ( $age === null ) ? $this->mWaitTimeout : $age;
1417
1418                 return ( $this->hasMasterChanges()
1419                         || $this->lastMasterChangeTimestamp() > microtime( true ) - $age );
1420         }
1421
1422         public function pendingMasterChangeCallers() {
1423                 $fnames = [];
1424                 $this->forEachOpenMasterConnection( function ( IDatabase $conn ) use ( &$fnames ) {
1425                         $fnames = array_merge( $fnames, $conn->pendingWriteCallers() );
1426                 } );
1427
1428                 return $fnames;
1429         }
1430
1431         public function getLaggedReplicaMode( $domain = false ) {
1432                 // No-op if there is only one DB (also avoids recursion)
1433                 if ( !$this->laggedReplicaMode && $this->getServerCount() > 1 ) {
1434                         try {
1435                                 // See if laggedReplicaMode gets set
1436                                 $conn = $this->getConnection( self::DB_REPLICA, false, $domain );
1437                                 $this->reuseConnection( $conn );
1438                         } catch ( DBConnectionError $e ) {
1439                                 // Avoid expensive re-connect attempts and failures
1440                                 $this->allReplicasDownMode = true;
1441                                 $this->laggedReplicaMode = true;
1442                         }
1443                 }
1444
1445                 return $this->laggedReplicaMode;
1446         }
1447
1448         /**
1449          * @param bool $domain
1450          * @return bool
1451          * @deprecated 1.28; use getLaggedReplicaMode()
1452          */
1453         public function getLaggedSlaveMode( $domain = false ) {
1454                 return $this->getLaggedReplicaMode( $domain );
1455         }
1456
1457         public function laggedReplicaUsed() {
1458                 return $this->laggedReplicaMode;
1459         }
1460
1461         /**
1462          * @return bool
1463          * @since 1.27
1464          * @deprecated Since 1.28; use laggedReplicaUsed()
1465          */
1466         public function laggedSlaveUsed() {
1467                 return $this->laggedReplicaUsed();
1468         }
1469
1470         public function getReadOnlyReason( $domain = false, IDatabase $conn = null ) {
1471                 if ( $this->readOnlyReason !== false ) {
1472                         return $this->readOnlyReason;
1473                 } elseif ( $this->getLaggedReplicaMode( $domain ) ) {
1474                         if ( $this->allReplicasDownMode ) {
1475                                 return 'The database has been automatically locked ' .
1476                                         'until the replica database servers become available';
1477                         } else {
1478                                 return 'The database has been automatically locked ' .
1479                                         'while the replica database servers catch up to the master.';
1480                         }
1481                 } elseif ( $this->masterRunningReadOnly( $domain, $conn ) ) {
1482                         return 'The database master is running in read-only mode.';
1483                 }
1484
1485                 return false;
1486         }
1487
1488         /**
1489          * @param string $domain Domain ID, or false for the current domain
1490          * @param IDatabase|null $conn DB master connectionl used to avoid loops [optional]
1491          * @return bool
1492          */
1493         private function masterRunningReadOnly( $domain, IDatabase $conn = null ) {
1494                 $cache = $this->wanCache;
1495                 $masterServer = $this->getServerName( $this->getWriterIndex() );
1496
1497                 return (bool)$cache->getWithSetCallback(
1498                         $cache->makeGlobalKey( __CLASS__, 'server-read-only', $masterServer ),
1499                         self::TTL_CACHE_READONLY,
1500                         function () use ( $domain, $conn ) {
1501                                 $old = $this->trxProfiler->setSilenced( true );
1502                                 try {
1503                                         $dbw = $conn ?: $this->getConnection( self::DB_MASTER, [], $domain );
1504                                         $readOnly = (int)$dbw->serverIsReadOnly();
1505                                         if ( !$conn ) {
1506                                                 $this->reuseConnection( $dbw );
1507                                         }
1508                                 } catch ( DBError $e ) {
1509                                         $readOnly = 0;
1510                                 }
1511                                 $this->trxProfiler->setSilenced( $old );
1512                                 return $readOnly;
1513                         },
1514                         [ 'pcTTL' => $cache::TTL_PROC_LONG, 'busyValue' => 0 ]
1515                 );
1516         }
1517
1518         public function allowLagged( $mode = null ) {
1519                 if ( $mode === null ) {
1520                         return $this->mAllowLagged;
1521                 }
1522                 $this->mAllowLagged = $mode;
1523
1524                 return $this->mAllowLagged;
1525         }
1526
1527         public function pingAll() {
1528                 $success = true;
1529                 $this->forEachOpenConnection( function ( IDatabase $conn ) use ( &$success ) {
1530                         if ( !$conn->ping() ) {
1531                                 $success = false;
1532                         }
1533                 } );
1534
1535                 return $success;
1536         }
1537
1538         public function forEachOpenConnection( $callback, array $params = [] ) {
1539                 foreach ( $this->mConns as $connsByServer ) {
1540                         foreach ( $connsByServer as $serverConns ) {
1541                                 foreach ( $serverConns as $conn ) {
1542                                         $mergedParams = array_merge( [ $conn ], $params );
1543                                         call_user_func_array( $callback, $mergedParams );
1544                                 }
1545                         }
1546                 }
1547         }
1548
1549         public function forEachOpenMasterConnection( $callback, array $params = [] ) {
1550                 $masterIndex = $this->getWriterIndex();
1551                 foreach ( $this->mConns as $connsByServer ) {
1552                         if ( isset( $connsByServer[$masterIndex] ) ) {
1553                                 /** @var IDatabase $conn */
1554                                 foreach ( $connsByServer[$masterIndex] as $conn ) {
1555                                         $mergedParams = array_merge( [ $conn ], $params );
1556                                         call_user_func_array( $callback, $mergedParams );
1557                                 }
1558                         }
1559                 }
1560         }
1561
1562         public function forEachOpenReplicaConnection( $callback, array $params = [] ) {
1563                 foreach ( $this->mConns as $connsByServer ) {
1564                         foreach ( $connsByServer as $i => $serverConns ) {
1565                                 if ( $i === $this->getWriterIndex() ) {
1566                                         continue; // skip master
1567                                 }
1568                                 foreach ( $serverConns as $conn ) {
1569                                         $mergedParams = array_merge( [ $conn ], $params );
1570                                         call_user_func_array( $callback, $mergedParams );
1571                                 }
1572                         }
1573                 }
1574         }
1575
1576         public function getMaxLag( $domain = false ) {
1577                 $maxLag = -1;
1578                 $host = '';
1579                 $maxIndex = 0;
1580
1581                 if ( $this->getServerCount() <= 1 ) {
1582                         return [ $host, $maxLag, $maxIndex ]; // no replication = no lag
1583                 }
1584
1585                 $lagTimes = $this->getLagTimes( $domain );
1586                 foreach ( $lagTimes as $i => $lag ) {
1587                         if ( $this->mLoads[$i] > 0 && $lag > $maxLag ) {
1588                                 $maxLag = $lag;
1589                                 $host = $this->mServers[$i]['host'];
1590                                 $maxIndex = $i;
1591                         }
1592                 }
1593
1594                 return [ $host, $maxLag, $maxIndex ];
1595         }
1596
1597         public function getLagTimes( $domain = false ) {
1598                 if ( $this->getServerCount() <= 1 ) {
1599                         return [ $this->getWriterIndex() => 0 ]; // no replication = no lag
1600                 }
1601
1602                 $knownLagTimes = []; // map of (server index => 0 seconds)
1603                 $indexesWithLag = [];
1604                 foreach ( $this->mServers as $i => $server ) {
1605                         if ( empty( $server['is static'] ) ) {
1606                                 $indexesWithLag[] = $i; // DB server might have replication lag
1607                         } else {
1608                                 $knownLagTimes[$i] = 0; // DB server is a non-replicating and read-only archive
1609                         }
1610                 }
1611
1612                 return $this->getLoadMonitor()->getLagTimes( $indexesWithLag, $domain ) + $knownLagTimes;
1613         }
1614
1615         public function safeGetLag( IDatabase $conn ) {
1616                 if ( $this->getServerCount() <= 1 ) {
1617                         return 0;
1618                 } else {
1619                         return $conn->getLag();
1620                 }
1621         }
1622
1623         /**
1624          * @param IDatabase $conn
1625          * @param DBMasterPos|bool $pos
1626          * @param int $timeout
1627          * @return bool
1628          */
1629         public function safeWaitForMasterPos( IDatabase $conn, $pos = false, $timeout = 10 ) {
1630                 if ( $this->getServerCount() <= 1 || !$conn->getLBInfo( 'replica' ) ) {
1631                         return true; // server is not a replica DB
1632                 }
1633
1634                 if ( !$pos ) {
1635                         // Get the current master position, opening a connection if needed
1636                         $masterConn = $this->getAnyOpenConnection( $this->getWriterIndex() );
1637                         if ( $masterConn ) {
1638                                 $pos = $masterConn->getMasterPos();
1639                         } else {
1640                                 $masterConn = $this->openConnection( $this->getWriterIndex(), self::DOMAIN_ANY );
1641                                 $pos = $masterConn->getMasterPos();
1642                                 $this->closeConnection( $masterConn );
1643                         }
1644                 }
1645
1646                 if ( $pos instanceof DBMasterPos ) {
1647                         $result = $conn->masterPosWait( $pos, $timeout );
1648                         if ( $result == -1 || is_null( $result ) ) {
1649                                 $msg = __METHOD__ . ': Timed out waiting on {host} pos {pos}';
1650                                 $this->replLogger->warning( $msg,
1651                                         [ 'host' => $conn->getServer(), 'pos' => $pos ] );
1652                                 $ok = false;
1653                         } else {
1654                                 $this->replLogger->info( __METHOD__ . ': Done' );
1655                                 $ok = true;
1656                         }
1657                 } else {
1658                         $ok = false; // something is misconfigured
1659                         $this->replLogger->error( 'Could not get master pos for {host}',
1660                                 [ 'host' => $conn->getServer() ] );
1661                 }
1662
1663                 return $ok;
1664         }
1665
1666         public function setTransactionListener( $name, callable $callback = null ) {
1667                 if ( $callback ) {
1668                         $this->trxRecurringCallbacks[$name] = $callback;
1669                 } else {
1670                         unset( $this->trxRecurringCallbacks[$name] );
1671                 }
1672                 $this->forEachOpenMasterConnection(
1673                         function ( IDatabase $conn ) use ( $name, $callback ) {
1674                                 $conn->setTransactionListener( $name, $callback );
1675                         }
1676                 );
1677         }
1678
1679         public function setTableAliases( array $aliases ) {
1680                 $this->tableAliases = $aliases;
1681         }
1682
1683         public function setDomainPrefix( $prefix ) {
1684                 // Find connections to explicit foreign domains still marked as in-use...
1685                 $domainsInUse = [];
1686                 $this->forEachOpenConnection( function ( IDatabase $conn ) use ( &$domainsInUse ) {
1687                         // Once reuseConnection() is called on a handle, its reference count goes from 1 to 0.
1688                         // Until then, it is still in use by the caller (explicitly or via DBConnRef scope).
1689                         if ( $conn->getLBInfo( 'foreignPoolRefCount' ) > 0 ) {
1690                                 $domainsInUse[] = $conn->getDomainID();
1691                         }
1692                 } );
1693
1694                 // Do not switch connections to explicit foreign domains unless marked as safe
1695                 if ( $domainsInUse ) {
1696                         $domains = implode( ', ', $domainsInUse );
1697                         throw new DBUnexpectedError( null,
1698                                 "Foreign domain connections are still in use ($domains)." );
1699                 }
1700
1701                 $this->localDomain = new DatabaseDomain(
1702                         $this->localDomain->getDatabase(),
1703                         null,
1704                         $prefix
1705                 );
1706
1707                 $this->forEachOpenConnection( function ( IDatabase $db ) use ( $prefix ) {
1708                         $db->tablePrefix( $prefix );
1709                 } );
1710         }
1711
1712         /**
1713          * Make PHP ignore user aborts/disconnects until the returned
1714          * value leaves scope. This returns null and does nothing in CLI mode.
1715          *
1716          * @return ScopedCallback|null
1717          */
1718         final protected function getScopedPHPBehaviorForCommit() {
1719                 if ( PHP_SAPI != 'cli' ) { // https://bugs.php.net/bug.php?id=47540
1720                         $old = ignore_user_abort( true ); // avoid half-finished operations
1721                         return new ScopedCallback( function () use ( $old ) {
1722                                 ignore_user_abort( $old );
1723                         } );
1724                 }
1725
1726                 return null;
1727         }
1728
1729         function __destruct() {
1730                 // Avoid connection leaks for sanity
1731                 $this->disable();
1732         }
1733 }
1734
1735 class_alias( LoadBalancer::class, 'LoadBalancer' );