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  * @ingroup Database
  22  */
  23 namespace Wikimedia\Rdbms;
  24
  25 use Psr\Log\LoggerInterface;
  26 use Psr\Log\NullLogger;
  27 use Wikimedia\ScopedCallback;
  28 use BagOStuff;
  29 use EmptyBagOStuff;
  30 use WANObjectCache;
  31 use ArrayUtils;
  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 array[] Map of (server index => server config array) */
  43         private $mServers;
  44         /** @var Database[][][] Map of (connection category => server index => IDatabase[]) */
  45         private $mConns;
  46         /** @var float[] Map of (server index => weight) */
  47         private $mLoads;
  48         /** @var array[] Map of (group => server index => weight) */
  49         private $mGroupLoads;
  50         /** @var bool Whether to disregard replica DB lag as a factor in replica DB selection */
  51         private $mAllowLagged;
  52         /** @var int Seconds to spend waiting on replica DB lag to resolve */
  53         private $mWaitTimeout;
  54         /** @var array The LoadMonitor configuration */
  55         private $loadMonitorConfig;
  56         /** @var array[] $aliases Map of (table => (dbname, schema, prefix) map) */
  57         private $tableAliases = [];
  58
  59         /** @var ILoadMonitor */
  60         private $loadMonitor;
  61         /** @var ChronologyProtector|null */
  62         private $chronProt;
  63         /** @var BagOStuff */
  64         private $srvCache;
  65         /** @var WANObjectCache */
  66         private $wanCache;
  67         /** @var object|string Class name or object With profileIn/profileOut methods */
  68         protected $profiler;
  69         /** @var TransactionProfiler */
  70         protected $trxProfiler;
  71         /** @var LoggerInterface */
  72         protected $replLogger;
  73         /** @var LoggerInterface */
  74         protected $connLogger;
  75         /** @var LoggerInterface */
  76         protected $queryLogger;
  77         /** @var LoggerInterface */
  78         protected $perfLogger;
  79
  80         /** @var Database DB connection object that caused a problem */
  81         private $errorConnection;
  82         /** @var int The generic (not query grouped) replica DB index (of $mServers) */
  83         private $mReadIndex;
  84         /** @var bool|DBMasterPos False if not set */
  85         private $mWaitForPos;
  86         /** @var bool Whether the generic reader fell back to a lagged replica DB */
  87         private $laggedReplicaMode = false;
  88         /** @var bool Whether the generic reader fell back to a lagged replica DB */
  89         private $allReplicasDownMode = false;
  90         /** @var string The last DB selection or connection error */
  91         private $mLastError = 'Unknown error';
  92         /** @var string|bool Reason the LB is read-only or false if not */
  93         private $readOnlyReason = false;
  94         /** @var int Total connections opened */
  95         private $connsOpened = 0;
  96         /** @var string|bool String if a requested DBO_TRX transaction round is active */
  97         private $trxRoundId = false;
  98         /** @var array[] Map of (name => callable) */
  99         private $trxRecurringCallbacks = [];
 100         /** @var DatabaseDomain Local Domain ID and default for selectDB() calls */
 101         private $localDomain;
 102         /** @var string Alternate ID string for the domain instead of DatabaseDomain::getId() */
 103         private $localDomainIdAlias;
 104         /** @var string Current server name */
 105         private $host;
 106         /** @var bool Whether this PHP instance is for a CLI script */
 107         protected $cliMode;
 108         /** @var string Agent name for query profiling */
 109         protected $agent;
 110
 111         /** @var callable Exception logger */
 112         private $errorLogger;
 113
 114         /** @var bool */
 115         private $disabled = false;
 116         /** @var bool */
 117         private $chronProtInitialized = false;
 118         /** @var int */
 119         private $maxLag = self::MAX_LAG_DEFAULT;
 120
 121         /** @var int Warn when this many connection are held */
 122         const CONN_HELD_WARN_THRESHOLD = 10;
 123
 124         /** @var int Default 'maxLag' when unspecified */
 125         const MAX_LAG_DEFAULT = 10;
 126         /** @var int Seconds to cache master server read-only status */
 127         const TTL_CACHE_READONLY = 5;
 128
 129         const KEY_LOCAL = 'local';
 130         const KEY_FOREIGN_FREE = 'foreignFree';
 131         const KEY_FOREIGN_INUSE = 'foreignInUse';
 132
 133         const KEY_LOCAL_NOROUND = 'localAutoCommit';
 134         const KEY_FOREIGN_FREE_NOROUND = 'foreignFreeAutoCommit';
 135         const KEY_FOREIGN_INUSE_NOROUND = 'foreignInUseAutoCommit';
 136
 137         public function __construct( array $params ) {
 138                 if ( !isset( $params['servers'] ) ) {
 139                         throw new InvalidArgumentException( __CLASS__ . ': missing servers parameter' );
 140                 }
 141                 $this->mServers = $params['servers'];
 142                 foreach ( $this->mServers as $i => $server ) {
 143                         if ( $i == 0 ) {
 144                                 $this->mServers[$i]['master'] = true;
 145                         } else {
 146                                 $this->mServers[$i]['replica'] = true;
 147                         }
 148                 }
 149
 150                 $this->localDomain = isset( $params['localDomain'] )
 151                         ? DatabaseDomain::newFromId( $params['localDomain'] )
 152                         : DatabaseDomain::newUnspecified();
 153                 // In case a caller assumes that the domain ID is simply <db>-<prefix>, which is almost
 154                 // always true, gracefully handle the case when they fail to account for escaping.
 155                 if ( $this->localDomain->getTablePrefix() != '' ) {
 156                         $this->localDomainIdAlias =
 157                                 $this->localDomain->getDatabase() . '-' . $this->localDomain->getTablePrefix();
 158                 } else {
 159                         $this->localDomainIdAlias = $this->localDomain->getDatabase();
 160                 }
 161
 162                 $this->mWaitTimeout = isset( $params['waitTimeout'] ) ? $params['waitTimeout'] : 10;
 163
 164                 $this->mReadIndex = -1;
 165                 $this->mConns = [
 166                         // Connection were transaction rounds may be applied
 167                         self::KEY_LOCAL => [],
 168                         self::KEY_FOREIGN_INUSE => [],
 169                         self::KEY_FOREIGN_FREE => [],
 170                         // Auto-committing counterpart connections that ignore transaction rounds
 171                         self::KEY_LOCAL_NOROUND => [],
 172                         self::KEY_FOREIGN_INUSE_NOROUND => [],
 173                         self::KEY_FOREIGN_FREE_NOROUND => []
 174                 ];
 175                 $this->mLoads = [];
 176                 $this->mWaitForPos = false;
 177                 $this->mAllowLagged = false;
 178
 179                 if ( isset( $params['readOnlyReason'] ) && is_string( $params['readOnlyReason'] ) ) {
 180                         $this->readOnlyReason = $params['readOnlyReason'];
 181                 }
 182
 183                 if ( isset( $params['maxLag'] ) ) {
 184                         $this->maxLag = $params['maxLag'];
 185                 }
 186
 187                 if ( isset( $params['loadMonitor'] ) ) {
 188                         $this->loadMonitorConfig = $params['loadMonitor'];
 189                 } else {
 190                         $this->loadMonitorConfig = [ 'class' => 'LoadMonitorNull' ];
 191                 }
 192                 $this->loadMonitorConfig += [ 'lagWarnThreshold' => $this->maxLag ];
 193
 194                 foreach ( $params['servers'] as $i => $server ) {
 195                         $this->mLoads[$i] = $server['load'];
 196                         if ( isset( $server['groupLoads'] ) ) {
 197                                 foreach ( $server['groupLoads'] as $group => $ratio ) {
 198                                         if ( !isset( $this->mGroupLoads[$group] ) ) {
 199                                                 $this->mGroupLoads[$group] = [];
 200                                         }
 201                                         $this->mGroupLoads[$group][$i] = $ratio;
 202                                 }
 203                         }
 204                 }
 205
 206                 if ( isset( $params['srvCache'] ) ) {
 207                         $this->srvCache = $params['srvCache'];
 208                 } else {
 209                         $this->srvCache = new EmptyBagOStuff();
 210                 }
 211                 if ( isset( $params['wanCache'] ) ) {
 212                         $this->wanCache = $params['wanCache'];
 213                 } else {
 214                         $this->wanCache = WANObjectCache::newEmpty();
 215                 }
 216                 $this->profiler = isset( $params['profiler'] ) ? $params['profiler'] : null;
 217                 if ( isset( $params['trxProfiler'] ) ) {
 218                         $this->trxProfiler = $params['trxProfiler'];
 219                 } else {
 220                         $this->trxProfiler = new TransactionProfiler();
 221                 }
 222
 223                 $this->errorLogger = isset( $params['errorLogger'] )
 224                         ? $params['errorLogger']
 225                         : function ( Exception $e ) {
 226                                 trigger_error( get_class( $e ) . ': ' . $e->getMessage(), E_USER_WARNING );
 227                         };
 228
 229                 foreach ( [ 'replLogger', 'connLogger', 'queryLogger', 'perfLogger' ] as $key ) {
 230                         $this->$key = isset( $params[$key] ) ? $params[$key] : new NullLogger();
 231                 }
 232
 233                 $this->host = isset( $params['hostname'] )
 234                         ? $params['hostname']
 235                         : ( gethostname() ?: 'unknown' );
 236                 $this->cliMode = isset( $params['cliMode'] ) ? $params['cliMode'] : PHP_SAPI === 'cli';
 237                 $this->agent = isset( $params['agent'] ) ? $params['agent'] : '';
 238
 239                 if ( isset( $params['chronologyProtector'] ) ) {
 240                         $this->chronProt = $params['chronologyProtector'];
 241                 }
 242         }
 243
 244         /**
 245          * Get a LoadMonitor instance
 246          *
 247          * @return ILoadMonitor
 248          */
 249         private function getLoadMonitor() {
 250                 if ( !isset( $this->loadMonitor ) ) {
 251                         $compat = [
 252                                 'LoadMonitor' => LoadMonitor::class,
 253                                 'LoadMonitorNull' => LoadMonitorNull::class,
 254                                 'LoadMonitorMySQL' => LoadMonitorMySQL::class,
 255                         ];
 256
 257                         $class = $this->loadMonitorConfig['class'];
 258                         if ( isset( $compat[$class] ) ) {
 259                                 $class = $compat[$class];
 260                         }
 261
 262                         $this->loadMonitor = new $class(
 263                                 $this, $this->srvCache, $this->wanCache, $this->loadMonitorConfig );
 264                         $this->loadMonitor->setLogger( $this->replLogger );
 265                 }
 266
 267                 return $this->loadMonitor;
 268         }
 269
 270         /**
 271          * @param array $loads
 272          * @param bool|string $domain Domain to get non-lagged for
 273          * @param int $maxLag Restrict the maximum allowed lag to this many seconds
 274          * @return bool|int|string
 275          */
 276         private function getRandomNonLagged( array $loads, $domain = false, $maxLag = INF ) {
 277                 $lags = $this->getLagTimes( $domain );
 278
 279                 # Unset excessively lagged servers
 280                 foreach ( $lags as $i => $lag ) {
 281                         if ( $i != 0 ) {
 282                                 # How much lag this server nominally is allowed to have
 283                                 $maxServerLag = isset( $this->mServers[$i]['max lag'] )
 284                                         ? $this->mServers[$i]['max lag']
 285                                         : $this->maxLag; // default
 286                                 # Constrain that futher by $maxLag argument
 287                                 $maxServerLag = min( $maxServerLag, $maxLag );
 288
 289                                 $host = $this->getServerName( $i );
 290                                 if ( $lag === false && !is_infinite( $maxServerLag ) ) {
 291                                         $this->replLogger->error(
 292                                                 "Server {host} is not replicating?", [ 'host' => $host ] );
 293                                         unset( $loads[$i] );
 294                                 } elseif ( $lag > $maxServerLag ) {
 295                                         $this->replLogger->info(
 296                                                 "Server {host} has {lag} seconds of lag (>= {maxlag})",
 297                                                 [ 'host' => $host, 'lag' => $lag, 'maxlag' => $maxServerLag ]
 298                                         );
 299                                         unset( $loads[$i] );
 300                                 }
 301                         }
 302                 }
 303
 304                 # Find out if all the replica DBs with non-zero load are lagged
 305                 $sum = 0;
 306                 foreach ( $loads as $load ) {
 307                         $sum += $load;
 308                 }
 309                 if ( $sum == 0 ) {
 310                         # No appropriate DB servers except maybe the master and some replica DBs with zero load
 311                         # Do NOT use the master
 312                         # Instead, this function will return false, triggering read-only mode,
 313                         # and a lagged replica DB will be used instead.
 314                         return false;
 315                 }
 316
 317                 if ( count( $loads ) == 0 ) {
 318                         return false;
 319                 }
 320
 321                 # Return a random representative of the remainder
 322                 return ArrayUtils::pickRandom( $loads );
 323         }
 324
 325         public function getReaderIndex( $group = false, $domain = false ) {
 326                 if ( count( $this->mServers ) == 1 ) {
 327                         // Skip the load balancing if there's only one server
 328                         return $this->getWriterIndex();
 329                 } elseif ( $group === false && $this->mReadIndex >= 0 ) {
 330                         // Shortcut if the generic reader index was already cached
 331                         return $this->mReadIndex;
 332                 }
 333
 334                 if ( $group !== false ) {
 335                         // Use the server weight array for this load group
 336                         if ( isset( $this->mGroupLoads[$group] ) ) {
 337                                 $loads = $this->mGroupLoads[$group];
 338                         } else {
 339                                 // No loads for this group, return false and the caller can use some other group
 340                                 $this->connLogger->info( __METHOD__ . ": no loads for group $group" );
 341
 342                                 return false;
 343                         }
 344                 } else {
 345                         // Use the generic load group
 346                         $loads = $this->mLoads;
 347                 }
 348
 349                 // Scale the configured load ratios according to each server's load and state
 350                 $this->getLoadMonitor()->scaleLoads( $loads, $domain );
 351
 352                 // Pick a server to use, accounting for weights, load, lag, and mWaitForPos
 353                 list( $i, $laggedReplicaMode ) = $this->pickReaderIndex( $loads, $domain );
 354                 if ( $i === false ) {
 355                         // Replica DB connection unsuccessful
 356                         return false;
 357                 }
 358
 359                 if ( $this->mWaitForPos && $i != $this->getWriterIndex() ) {
 360                         // Before any data queries are run, wait for the server to catch up to the
 361                         // specified position. This is used to improve session consistency. Note that
 362                         // when LoadBalancer::waitFor() sets mWaitForPos, the waiting triggers here,
 363                         // so update laggedReplicaMode as needed for consistency.
 364                         if ( !$this->doWait( $i ) ) {
 365                                 $laggedReplicaMode = true;
 366                         }
 367                 }
 368
 369                 if ( $this->mReadIndex <= 0 && $this->mLoads[$i] > 0 && $group === false ) {
 370                         // Cache the generic reader index for future ungrouped DB_REPLICA handles
 371                         $this->mReadIndex = $i;
 372                         // Record if the generic reader index is in "lagged replica DB" mode
 373                         if ( $laggedReplicaMode ) {
 374                                 $this->laggedReplicaMode = true;
 375                         }
 376                 }
 377
 378                 $serverName = $this->getServerName( $i );
 379                 $this->connLogger->debug( __METHOD__ . ": using server $serverName for group '$group'" );
 380
 381                 return $i;
 382         }
 383
 384         /**
 385          * @param array $loads List of server weights
 386          * @param string|bool $domain
 387          * @return array (reader index, lagged replica mode) or false on failure
 388          */
 389         private function pickReaderIndex( array $loads, $domain = false ) {
 390                 if ( !count( $loads ) ) {
 391                         throw new InvalidArgumentException( "Empty server array given to LoadBalancer" );
 392                 }
 393
 394                 /** @var int|bool $i Index of selected server */
 395                 $i = false;
 396                 /** @var bool $laggedReplicaMode Whether server is considered lagged */
 397                 $laggedReplicaMode = false;
 398
 399                 // Quickly look through the available servers for a server that meets criteria...
 400                 $currentLoads = $loads;
 401                 while ( count( $currentLoads ) ) {
 402                         if ( $this->mAllowLagged || $laggedReplicaMode ) {
 403                                 $i = ArrayUtils::pickRandom( $currentLoads );
 404                         } else {
 405                                 $i = false;
 406                                 if ( $this->mWaitForPos && $this->mWaitForPos->asOfTime() ) {
 407                                         // ChronologyProtecter sets mWaitForPos for session consistency.
 408                                         // This triggers doWait() after connect, so it's especially good to
 409                                         // avoid lagged servers so as to avoid excessive delay in that method.
 410                                         $ago = microtime( true ) - $this->mWaitForPos->asOfTime();
 411                                         // Aim for <= 1 second of waiting (being too picky can backfire)
 412                                         $i = $this->getRandomNonLagged( $currentLoads, $domain, $ago + 1 );
 413                                 }
 414                                 if ( $i === false ) {
 415                                         // Any server with less lag than it's 'max lag' param is preferable
 416                                         $i = $this->getRandomNonLagged( $currentLoads, $domain );
 417                                 }
 418                                 if ( $i === false && count( $currentLoads ) != 0 ) {
 419                                         // All replica DBs lagged. Switch to read-only mode
 420                                         $this->replLogger->error( "All replica DBs lagged. Switch to read-only mode" );
 421                                         $i = ArrayUtils::pickRandom( $currentLoads );
 422                                         $laggedReplicaMode = true;
 423                                 }
 424                         }
 425
 426                         if ( $i === false ) {
 427                                 // pickRandom() returned false.
 428                                 // This is permanent and means the configuration or the load monitor
 429                                 // wants us to return false.
 430                                 $this->connLogger->debug( __METHOD__ . ": pickRandom() returned false" );
 431
 432                                 return [ false, false ];
 433                         }
 434
 435                         $serverName = $this->getServerName( $i );
 436                         $this->connLogger->debug( __METHOD__ . ": Using reader #$i: $serverName..." );
 437
 438                         $conn = $this->openConnection( $i, $domain );
 439                         if ( !$conn ) {
 440                                 $this->connLogger->warning( __METHOD__ . ": Failed connecting to $i/$domain" );
 441                                 unset( $currentLoads[$i] ); // avoid this server next iteration
 442                                 $i = false;
 443                                 continue;
 444                         }
 445
 446                         // Decrement reference counter, we are finished with this connection.
 447                         // It will be incremented for the caller later.
 448                         if ( $domain !== false ) {
 449                                 $this->reuseConnection( $conn );
 450                         }
 451
 452                         // Return this server
 453                         break;
 454                 }
 455
 456                 // If all servers were down, quit now
 457                 if ( !count( $currentLoads ) ) {
 458                         $this->connLogger->error( "All servers down" );
 459                 }
 460
 461                 return [ $i, $laggedReplicaMode ];
 462         }
 463
 464         public function waitFor( $pos ) {
 465                 $oldPos = $this->mWaitForPos;
 466                 try {
 467                         $this->mWaitForPos = $pos;
 468                         // If a generic reader connection was already established, then wait now
 469                         $i = $this->mReadIndex;
 470                         if ( $i > 0 ) {
 471                                 if ( !$this->doWait( $i ) ) {
 472                                         $this->laggedReplicaMode = true;
 473                                 }
 474                         }
 475                 } finally {
 476                         // Restore the older position if it was higher since this is used for lag-protection
 477                         $this->setWaitForPositionIfHigher( $oldPos );
 478                 }
 479         }
 480
 481         public function waitForOne( $pos, $timeout = null ) {
 482                 $oldPos = $this->mWaitForPos;
 483                 try {
 484                         $this->mWaitForPos = $pos;
 485
 486                         $i = $this->mReadIndex;
 487                         if ( $i <= 0 ) {
 488                                 // Pick a generic replica DB if there isn't one yet
 489                                 $readLoads = $this->mLoads;
 490                                 unset( $readLoads[$this->getWriterIndex()] ); // replica DBs only
 491                                 $readLoads = array_filter( $readLoads ); // with non-zero load
 492                                 $i = ArrayUtils::pickRandom( $readLoads );
 493                         }
 494
 495                         if ( $i > 0 ) {
 496                                 $ok = $this->doWait( $i, true, $timeout );
 497                         } else {
 498                                 $ok = true; // no applicable loads
 499                         }
 500                 } finally {
 501                         # Restore the old position, as this is not used for lag-protection but for throttling
 502                         $this->mWaitForPos = $oldPos;
 503                 }
 504
 505                 return $ok;
 506         }
 507
 508         public function waitForAll( $pos, $timeout = null ) {
 509                 $oldPos = $this->mWaitForPos;
 510                 try {
 511                         $this->mWaitForPos = $pos;
 512                         $serverCount = count( $this->mServers );
 513
 514                         $ok = true;
 515                         for ( $i = 1; $i < $serverCount; $i++ ) {
 516                                 if ( $this->mLoads[$i] > 0 ) {
 517                                         $ok = $this->doWait( $i, true, $timeout ) && $ok;
 518                                 }
 519                         }
 520                 } finally {
 521                         # Restore the old position, as this is not used for lag-protection but for throttling
 522                         $this->mWaitForPos = $oldPos;
 523                 }
 524
 525                 return $ok;
 526         }
 527
 528         /**
 529          * @param DBMasterPos|bool $pos
 530          */
 531         private function setWaitForPositionIfHigher( $pos ) {
 532                 if ( !$pos ) {
 533                         return;
 534                 }
 535
 536                 if ( !$this->mWaitForPos || $pos->hasReached( $this->mWaitForPos ) ) {
 537                         $this->mWaitForPos = $pos;
 538                 }
 539         }
 540
 541         /**
 542          * @param int $i
 543          * @return IDatabase|bool
 544          */
 545         public function getAnyOpenConnection( $i ) {
 546                 foreach ( $this->mConns as $connsByServer ) {
 547                         if ( !empty( $connsByServer[$i] ) ) {
 548                                 /** @var IDatabase[] $serverConns */
 549                                 $serverConns = $connsByServer[$i];
 550
 551                                 return reset( $serverConns );
 552                         }
 553                 }
 554
 555                 return false;
 556         }
 557
 558         /**
 559          * Wait for a given replica DB to catch up to the master pos stored in $this
 560          * @param int $index Server index
 561          * @param bool $open Check the server even if a new connection has to be made
 562          * @param int $timeout Max seconds to wait; default is mWaitTimeout
 563          * @return bool
 564          */
 565         protected function doWait( $index, $open = false, $timeout = null ) {
 566                 $close = false; // close the connection afterwards
 567
 568                 // Check if we already know that the DB has reached this point
 569                 $server = $this->getServerName( $index );
 570                 $key = $this->srvCache->makeGlobalKey( __CLASS__, 'last-known-pos', $server, 'v1' );
 571                 /** @var DBMasterPos $knownReachedPos */
 572                 $knownReachedPos = $this->srvCache->get( $key );
 573                 if (
 574                         $knownReachedPos instanceof DBMasterPos &&
 575                         $knownReachedPos->hasReached( $this->mWaitForPos )
 576                 ) {
 577                         $this->replLogger->debug( __METHOD__ .
 578                                 ': replica DB {dbserver} known to be caught up (pos >= $knownReachedPos).',
 579                                 [ 'dbserver' => $server ] );
 580                         return true;
 581                 }
 582
 583                 // Find a connection to wait on, creating one if needed and allowed
 584                 $conn = $this->getAnyOpenConnection( $index );
 585                 if ( !$conn ) {
 586                         if ( !$open ) {
 587                                 $this->replLogger->debug( __METHOD__ . ': no connection open for {dbserver}',
 588                                         [ 'dbserver' => $server ] );
 589
 590                                 return false;
 591                         } else {
 592                                 $conn = $this->openConnection( $index, self::DOMAIN_ANY );
 593                                 if ( !$conn ) {
 594                                         $this->replLogger->warning( __METHOD__ . ': failed to connect to {dbserver}',
 595                                                 [ 'dbserver' => $server ] );
 596
 597                                         return false;
 598                                 }
 599                                 // Avoid connection spam in waitForAll() when connections
 600                                 // are made just for the sake of doing this lag check.
 601                                 $close = true;
 602                         }
 603                 }
 604
 605                 $this->replLogger->info( __METHOD__ . ': Waiting for replica DB {dbserver} to catch up...',
 606                         [ 'dbserver' => $server ] );
 607                 $timeout = $timeout ?: $this->mWaitTimeout;
 608                 $result = $conn->masterPosWait( $this->mWaitForPos, $timeout );
 609
 610                 if ( $result == -1 || is_null( $result ) ) {
 611                         // Timed out waiting for replica DB, use master instead
 612                         $this->replLogger->warning(
 613                                 __METHOD__ . ': Timed out waiting on {host} pos {pos}',
 614                                 [ 'host' => $server, 'pos' => $this->mWaitForPos ]
 615                         );
 616                         $ok = false;
 617                 } else {
 618                         $this->replLogger->info( __METHOD__ . ": Done" );
 619                         $ok = true;
 620                         // Remember that the DB reached this point
 621                         $this->srvCache->set( $key, $this->mWaitForPos, BagOStuff::TTL_DAY );
 622                 }
 623
 624                 if ( $close ) {
 625                         $this->closeConnection( $conn );
 626                 }
 627
 628                 return $ok;
 629         }
 630
 631         public function getConnection( $i, $groups = [], $domain = false, $flags = 0 ) {
 632                 if ( $i === null || $i === false ) {
 633                         throw new InvalidArgumentException( 'Attempt to call ' . __METHOD__ .
 634                                 ' with invalid server index' );
 635                 }
 636
 637                 if ( $this->localDomain->equals( $domain ) || $domain === $this->localDomainIdAlias ) {
 638                         $domain = false; // local connection requested
 639                 }
 640
 641                 $groups = ( $groups === false || $groups === [] )
 642                         ? [ false ] // check one "group": the generic pool
 643                         : (array)$groups;
 644
 645                 $masterOnly = ( $i == self::DB_MASTER || $i == $this->getWriterIndex() );
 646                 $oldConnsOpened = $this->connsOpened; // connections open now
 647
 648                 if ( $i == self::DB_MASTER ) {
 649                         $i = $this->getWriterIndex();
 650                 } else {
 651                         # Try to find an available server in any the query groups (in order)
 652                         foreach ( $groups as $group ) {
 653                                 $groupIndex = $this->getReaderIndex( $group, $domain );
 654                                 if ( $groupIndex !== false ) {
 655                                         $i = $groupIndex;
 656                                         break;
 657                                 }
 658                         }
 659                 }
 660
 661                 # Operation-based index
 662                 if ( $i == self::DB_REPLICA ) {
 663                         $this->mLastError = 'Unknown error'; // reset error string
 664                         # Try the general server pool if $groups are unavailable.
 665                         $i = ( $groups === [ false ] )
 666                                 ? false // don't bother with this if that is what was tried above
 667                                 : $this->getReaderIndex( false, $domain );
 668                         # Couldn't find a working server in getReaderIndex()?
 669                         if ( $i === false ) {
 670                                 $this->mLastError = 'No working replica DB server: ' . $this->mLastError;
 671                                 // Throw an exception
 672                                 $this->reportConnectionError();
 673                                 return null; // not reached
 674                         }
 675                 }
 676
 677                 # Now we have an explicit index into the servers array
 678                 $conn = $this->openConnection( $i, $domain, $flags );
 679                 if ( !$conn ) {
 680                         // Throw an exception
 681                         $this->reportConnectionError();
 682                         return null; // not reached
 683                 }
 684
 685                 # Profile any new connections that happen
 686                 if ( $this->connsOpened > $oldConnsOpened ) {
 687                         $host = $conn->getServer();
 688                         $dbname = $conn->getDBname();
 689                         $this->trxProfiler->recordConnection( $host, $dbname, $masterOnly );
 690                 }
 691
 692                 if ( $masterOnly ) {
 693                         # Make master-requested DB handles inherit any read-only mode setting
 694                         $conn->setLBInfo( 'readOnlyReason', $this->getReadOnlyReason( $domain, $conn ) );
 695                 }
 696
 697                 return $conn;
 698         }
 699
 700         public function reuseConnection( $conn ) {
 701                 $serverIndex = $conn->getLBInfo( 'serverIndex' );
 702                 $refCount = $conn->getLBInfo( 'foreignPoolRefCount' );
 703                 if ( $serverIndex === null || $refCount === null ) {
 704                         /**
 705                          * This can happen in code like:
 706                          *   foreach ( $dbs as $db ) {
 707                          *     $conn = $lb->getConnection( $lb::DB_REPLICA, [], $db );
 708                          *     ...
 709                          *     $lb->reuseConnection( $conn );
 710                          *   }
 711                          * When a connection to the local DB is opened in this way, reuseConnection()
 712                          * should be ignored
 713                          */
 714                         return;
 715                 } elseif ( $conn instanceof DBConnRef ) {
 716                         // DBConnRef already handles calling reuseConnection() and only passes the live
 717                         // Database instance to this method. Any caller passing in a DBConnRef is broken.
 718                         $this->connLogger->error( __METHOD__ . ": got DBConnRef instance.\n" .
 719                                 ( new RuntimeException() )->getTraceAsString() );
 720
 721                         return;
 722                 }
 723
 724                 if ( $this->disabled ) {
 725                         return; // DBConnRef handle probably survived longer than the LoadBalancer
 726                 }
 727
 728                 if ( $conn->getLBInfo( 'autoCommitOnly' ) ) {
 729                         $connFreeKey = self::KEY_FOREIGN_FREE_NOROUND;
 730                         $connInUseKey = self::KEY_FOREIGN_INUSE_NOROUND;
 731                 } else {
 732                         $connFreeKey = self::KEY_FOREIGN_FREE;
 733                         $connInUseKey = self::KEY_FOREIGN_INUSE;
 734                 }
 735
 736                 $domain = $conn->getDomainID();
 737                 if ( !isset( $this->mConns[$connInUseKey][$serverIndex][$domain] ) ) {
 738                         throw new InvalidArgumentException( __METHOD__ .
 739                                 ": connection $serverIndex/$domain not found; it may have already been freed." );
 740                 } elseif ( $this->mConns[$connInUseKey][$serverIndex][$domain] !== $conn ) {
 741                         throw new InvalidArgumentException( __METHOD__ .
 742                                 ": connection $serverIndex/$domain mismatched; it may have already been freed." );
 743                 }
 744
 745                 $conn->setLBInfo( 'foreignPoolRefCount', --$refCount );
 746                 if ( $refCount <= 0 ) {
 747                         $this->mConns[$connFreeKey][$serverIndex][$domain] = $conn;
 748                         unset( $this->mConns[$connInUseKey][$serverIndex][$domain] );
 749                         if ( !$this->mConns[$connInUseKey][$serverIndex] ) {
 750                                 unset( $this->mConns[$connInUseKey][$serverIndex] ); // clean up
 751                         }
 752                         $this->connLogger->debug( __METHOD__ . ": freed connection $serverIndex/$domain" );
 753                 } else {
 754                         $this->connLogger->debug( __METHOD__ .
 755                                 ": reference count for $serverIndex/$domain reduced to $refCount" );
 756                 }
 757         }
 758
 759         public function getConnectionRef( $db, $groups = [], $domain = false, $flags = 0 ) {
 760                 $domain = ( $domain !== false ) ? $domain : $this->localDomain;
 761
 762                 return new DBConnRef( $this, $this->getConnection( $db, $groups, $domain, $flags ) );
 763         }
 764
 765         public function getLazyConnectionRef( $db, $groups = [], $domain = false, $flags = 0 ) {
 766                 $domain = ( $domain !== false ) ? $domain : $this->localDomain;
 767
 768                 return new DBConnRef( $this, [ $db, $groups, $domain, $flags ] );
 769         }
 770
 771         public function getMaintenanceConnectionRef( $db, $groups = [], $domain = false, $flags = 0 ) {
 772                 $domain = ( $domain !== false ) ? $domain : $this->localDomain;
 773
 774                 return new MaintainableDBConnRef(
 775                         $this, $this->getConnection( $db, $groups, $domain, $flags ) );
 776         }
 777
 778         public function openConnection( $i, $domain = false, $flags = 0 ) {
 779                 if ( $this->localDomain->equals( $domain ) || $domain === $this->localDomainIdAlias ) {
 780                         $domain = false; // local connection requested
 781                 }
 782
 783                 if ( !$this->chronProtInitialized && $this->chronProt ) {
 784                         $this->connLogger->debug( __METHOD__ . ': calling initLB() before first connection.' );
 785                         // Load CP positions before connecting so that doWait() triggers later if needed
 786                         $this->chronProtInitialized = true;
 787                         $this->chronProt->initLB( $this );
 788                 }
 789
 790                 // Check if an auto-commit connection is being requested. If so, it will not reuse the
 791                 // main set of DB connections but rather its own pool since:
 792                 // a) those are usually set to implicitly use transaction rounds via DBO_TRX
 793                 // b) those must support the use of explicit transaction rounds via beginMasterChanges()
 794                 $autoCommit = ( ( $flags & self::CONN_TRX_AUTO ) == self::CONN_TRX_AUTO );
 795
 796                 if ( $domain !== false ) {
 797                         // Connection is to a foreign domain
 798                         $conn = $this->openForeignConnection( $i, $domain, $flags );
 799                 } else {
 800                         // Connection is to the local domain
 801                         $connKey = $autoCommit ? self::KEY_LOCAL_NOROUND : self::KEY_LOCAL;
 802                         if ( isset( $this->mConns[$connKey][$i][0] ) ) {
 803                                 $conn = $this->mConns[$connKey][$i][0];
 804                         } else {
 805                                 if ( !isset( $this->mServers[$i] ) || !is_array( $this->mServers[$i] ) ) {
 806                                         throw new InvalidArgumentException( "No server with index '$i'." );
 807                                 }
 808                                 // Open a new connection
 809                                 $server = $this->mServers[$i];
 810                                 $server['serverIndex'] = $i;
 811                                 $server['autoCommitOnly'] = $autoCommit;
 812                                 $conn = $this->reallyOpenConnection( $server, false );
 813                                 $host = $this->getServerName( $i );
 814                                 if ( $conn->isOpen() ) {
 815                                         $this->connLogger->debug( "Connected to database $i at '$host'." );
 816                                         $this->mConns[$connKey][$i][0] = $conn;
 817                                 } else {
 818                                         $this->connLogger->warning( "Failed to connect to database $i at '$host'." );
 819                                         $this->errorConnection = $conn;
 820                                         $conn = false;
 821                                 }
 822                         }
 823                 }
 824
 825                 if ( $conn instanceof IDatabase && !$conn->isOpen() ) {
 826                         // Connection was made but later unrecoverably lost for some reason.
 827                         // Do not return a handle that will just throw exceptions on use,
 828                         // but let the calling code (e.g. getReaderIndex) try another server.
 829                         // See DatabaseMyslBase::ping() for how this can happen.
 830                         $this->errorConnection = $conn;
 831                         $conn = false;
 832                 }
 833
 834                 if ( $autoCommit && $conn instanceof IDatabase ) {
 835                         $conn->clearFlag( $conn::DBO_TRX ); // auto-commit mode
 836                 }
 837
 838                 return $conn;
 839         }
 840
 841         /**
 842          * Open a connection to a foreign DB, or return one if it is already open.
 843          *
 844          * Increments a reference count on the returned connection which locks the
 845          * connection to the requested domain. This reference count can be
 846          * decremented by calling reuseConnection().
 847          *
 848          * If a connection is open to the appropriate server already, but with the wrong
 849          * database, it will be switched to the right database and returned, as long as
 850          * it has been freed first with reuseConnection().
 851          *
 852          * On error, returns false, and the connection which caused the
 853          * error will be available via $this->errorConnection.
 854          *
 855          * @note If disable() was called on this LoadBalancer, this method will throw a DBAccessError.
 856          *
 857          * @param int $i Server index
 858          * @param string $domain Domain ID to open
 859          * @param int $flags Class CONN_* constant bitfield
 860          * @return Database
 861          */
 862         private function openForeignConnection( $i, $domain, $flags = 0 ) {
 863                 $domainInstance = DatabaseDomain::newFromId( $domain );
 864                 $dbName = $domainInstance->getDatabase();
 865                 $prefix = $domainInstance->getTablePrefix();
 866                 $autoCommit = ( ( $flags & self::CONN_TRX_AUTO ) == self::CONN_TRX_AUTO );
 867
 868                 if ( $autoCommit ) {
 869                         $connFreeKey = self::KEY_FOREIGN_FREE_NOROUND;
 870                         $connInUseKey = self::KEY_FOREIGN_INUSE_NOROUND;
 871                 } else {
 872                         $connFreeKey = self::KEY_FOREIGN_FREE;
 873                         $connInUseKey = self::KEY_FOREIGN_INUSE;
 874                 }
 875
 876                 if ( isset( $this->mConns[$connInUseKey][$i][$domain] ) ) {
 877                         // Reuse an in-use connection for the same domain
 878                         $conn = $this->mConns[$connInUseKey][$i][$domain];
 879                         $this->connLogger->debug( __METHOD__ . ": reusing connection $i/$domain" );
 880                 } elseif ( isset( $this->mConns[$connFreeKey][$i][$domain] ) ) {
 881                         // Reuse a free connection for the same domain
 882                         $conn = $this->mConns[$connFreeKey][$i][$domain];
 883                         unset( $this->mConns[$connFreeKey][$i][$domain] );
 884                         $this->mConns[$connInUseKey][$i][$domain] = $conn;
 885                         $this->connLogger->debug( __METHOD__ . ": reusing free connection $i/$domain" );
 886                 } elseif ( !empty( $this->mConns[$connFreeKey][$i] ) ) {
 887                         // Reuse a free connection from another domain
 888                         $conn = reset( $this->mConns[$connFreeKey][$i] );
 889                         $oldDomain = key( $this->mConns[$connFreeKey][$i] );
 890                         // The empty string as a DB name means "don't care".
 891                         // DatabaseMysqlBase::open() already handle this on connection.
 892                         if ( strlen( $dbName ) && !$conn->selectDB( $dbName ) ) {
 893                                 $this->mLastError = "Error selecting database '$dbName' on server " .
 894                                         $conn->getServer() . " from client host {$this->host}";
 895                                 $this->errorConnection = $conn;
 896                                 $conn = false;
 897                         } else {
 898                                 $conn->tablePrefix( $prefix );
 899                                 unset( $this->mConns[$connFreeKey][$i][$oldDomain] );
 900                                 $this->mConns[$connInUseKey][$i][$domain] = $conn;
 901                                 $this->connLogger->debug( __METHOD__ .
 902                                         ": reusing free connection from $oldDomain for $domain" );
 903                         }
 904                 } else {
 905                         if ( !isset( $this->mServers[$i] ) || !is_array( $this->mServers[$i] ) ) {
 906                                 throw new InvalidArgumentException( "No server with index '$i'." );
 907                         }
 908                         // Open a new connection
 909                         $server = $this->mServers[$i];
 910                         $server['serverIndex'] = $i;
 911                         $server['foreignPoolRefCount'] = 0;
 912                         $server['foreign'] = true;
 913                         $server['autoCommitOnly'] = $autoCommit;
 914                         $conn = $this->reallyOpenConnection( $server, $dbName );
 915                         if ( !$conn->isOpen() ) {
 916                                 $this->connLogger->warning( __METHOD__ . ": connection error for $i/$domain" );
 917                                 $this->errorConnection = $conn;
 918                                 $conn = false;
 919                         } else {
 920                                 $conn->tablePrefix( $prefix );
 921                                 $this->mConns[$connInUseKey][$i][$domain] = $conn;
 922                                 $this->connLogger->debug( __METHOD__ . ": opened new connection for $i/$domain" );
 923                         }
 924                 }
 925
 926                 // Increment reference count
 927                 if ( $conn instanceof IDatabase ) {
 928                         $refCount = $conn->getLBInfo( 'foreignPoolRefCount' );
 929                         $conn->setLBInfo( 'foreignPoolRefCount', $refCount + 1 );
 930                 }
 931
 932                 return $conn;
 933         }
 934
 935         /**
 936          * Test if the specified index represents an open connection
 937          *
 938          * @param int $index Server index
 939          * @access private
 940          * @return bool
 941          */
 942         private function isOpen( $index ) {
 943                 if ( !is_integer( $index ) ) {
 944                         return false;
 945                 }
 946
 947                 return (bool)$this->getAnyOpenConnection( $index );
 948         }
 949
 950         /**
 951          * Really opens a connection. Uncached.
 952          * Returns a Database object whether or not the connection was successful.
 953          * @access private
 954          *
 955          * @param array $server
 956          * @param string|bool $dbNameOverride Use "" to not select any database
 957          * @return Database
 958          * @throws DBAccessError
 959          * @throws InvalidArgumentException
 960          */
 961         protected function reallyOpenConnection( array $server, $dbNameOverride = false ) {
 962                 if ( $this->disabled ) {
 963                         throw new DBAccessError();
 964                 }
 965
 966                 if ( $dbNameOverride !== false ) {
 967                         $server['dbname'] = $dbNameOverride;
 968                 }
 969
 970                 // Let the handle know what the cluster master is (e.g. "db1052")
 971                 $masterName = $this->getServerName( $this->getWriterIndex() );
 972                 $server['clusterMasterHost'] = $masterName;
 973
 974                 // Log when many connection are made on requests
 975                 if ( ++$this->connsOpened >= self::CONN_HELD_WARN_THRESHOLD ) {
 976                         $this->perfLogger->warning( __METHOD__ . ": " .
 977                                 "{$this->connsOpened}+ connections made (master=$masterName)" );
 978                 }
 979
 980                 $server['srvCache'] = $this->srvCache;
 981                 // Set loggers and profilers
 982                 $server['connLogger'] = $this->connLogger;
 983                 $server['queryLogger'] = $this->queryLogger;
 984                 $server['errorLogger'] = $this->errorLogger;
 985                 $server['profiler'] = $this->profiler;
 986                 $server['trxProfiler'] = $this->trxProfiler;
 987                 // Use the same agent and PHP mode for all DB handles
 988                 $server['cliMode'] = $this->cliMode;
 989                 $server['agent'] = $this->agent;
 990                 // Use DBO_DEFAULT flags by default for LoadBalancer managed databases. Assume that the
 991                 // application calls LoadBalancer::commitMasterChanges() before the PHP script completes.
 992                 $server['flags'] = isset( $server['flags'] ) ? $server['flags'] : IDatabase::DBO_DEFAULT;
 993
 994                 // Create a live connection object
 995                 try {
 996                         $db = Database::factory( $server['type'], $server );
 997                 } catch ( DBConnectionError $e ) {
 998                         // FIXME: This is probably the ugliest thing I have ever done to
 999                         // PHP. I'm half-expecting it to segfault, just out of disgust. -- TS
1000                         $db = $e->db;
1001                 }
1002
1003                 $db->setLBInfo( $server );
1004                 $db->setLazyMasterHandle(
1005                         $this->getLazyConnectionRef( self::DB_MASTER, [], $db->getDomainID() )
1006                 );
1007                 $db->setTableAliases( $this->tableAliases );
1008
1009                 if ( $server['serverIndex'] === $this->getWriterIndex() ) {
1010                         if ( $this->trxRoundId !== false ) {
1011                                 $this->applyTransactionRoundFlags( $db );
1012                         }
1013                         foreach ( $this->trxRecurringCallbacks as $name => $callback ) {
1014                                 $db->setTransactionListener( $name, $callback );
1015                         }
1016                 }
1017
1018                 return $db;
1019         }
1020
1021         /**
1022          * @throws DBConnectionError
1023          */
1024         private function reportConnectionError() {
1025                 $conn = $this->errorConnection; // the connection which caused the error
1026                 $context = [
1027                         'method' => __METHOD__,
1028                         'last_error' => $this->mLastError,
1029                 ];
1030
1031                 if ( $conn instanceof IDatabase ) {
1032                         $context['db_server'] = $conn->getServer();
1033                         $this->connLogger->warning(
1034                                 "Connection error: {last_error} ({db_server})",
1035                                 $context
1036                         );
1037
1038                         // throws DBConnectionError
1039                         $conn->reportConnectionError( "{$this->mLastError} ({$context['db_server']})" );
1040                 } else {
1041                         // No last connection, probably due to all servers being too busy
1042                         $this->connLogger->error(
1043                                 "LB failure with no last connection. Connection error: {last_error}",
1044                                 $context
1045                         );
1046
1047                         // If all servers were busy, mLastError will contain something sensible
1048                         throw new DBConnectionError( null, $this->mLastError );
1049                 }
1050         }
1051
1052         public function getWriterIndex() {
1053                 return 0;
1054         }
1055
1056         public function haveIndex( $i ) {
1057                 return array_key_exists( $i, $this->mServers );
1058         }
1059
1060         public function isNonZeroLoad( $i ) {
1061                 return array_key_exists( $i, $this->mServers ) && $this->mLoads[$i] != 0;
1062         }
1063
1064         public function getServerCount() {
1065                 return count( $this->mServers );
1066         }
1067
1068         public function getServerName( $i ) {
1069                 if ( isset( $this->mServers[$i]['hostName'] ) ) {
1070                         $name = $this->mServers[$i]['hostName'];
1071                 } elseif ( isset( $this->mServers[$i]['host'] ) ) {
1072                         $name = $this->mServers[$i]['host'];
1073                 } else {
1074                         $name = '';
1075                 }
1076
1077                 return ( $name != '' ) ? $name : 'localhost';
1078         }
1079
1080         public function getServerType( $i ) {
1081                 return isset( $this->mServers[$i]['type'] ) ? $this->mServers[$i]['type'] : 'unknown';
1082         }
1083
1084         /**
1085          * @deprecated Since 1.30, no alternative
1086          */
1087         public function getServerInfo( $i ) {
1088                 wfDeprecated( __METHOD__, '1.30' );
1089                 if ( isset( $this->mServers[$i] ) ) {
1090                         return $this->mServers[$i];
1091                 } else {
1092                         return false;
1093                 }
1094         }
1095
1096         /**
1097          * @deprecated Since 1.30, construct new object
1098          */
1099         public function setServerInfo( $i, array $serverInfo ) {
1100                 wfDeprecated( __METHOD__, '1.30' );
1101                 $this->mServers[$i] = $serverInfo;
1102         }
1103
1104         public function getMasterPos() {
1105                 # If this entire request was served from a replica DB without opening a connection to the
1106                 # master (however unlikely that may be), then we can fetch the position from the replica DB.
1107                 $masterConn = $this->getAnyOpenConnection( $this->getWriterIndex() );
1108                 if ( !$masterConn ) {
1109                         $serverCount = count( $this->mServers );
1110                         for ( $i = 1; $i < $serverCount; $i++ ) {
1111                                 $conn = $this->getAnyOpenConnection( $i );
1112                                 if ( $conn ) {
1113                                         return $conn->getReplicaPos();
1114                                 }
1115                         }
1116                 } else {
1117                         return $masterConn->getMasterPos();
1118                 }
1119
1120                 return false;
1121         }
1122
1123         public function disable() {
1124                 $this->closeAll();
1125                 $this->disabled = true;
1126         }
1127
1128         public function closeAll() {
1129                 $this->forEachOpenConnection( function ( IDatabase $conn ) {
1130                         $host = $conn->getServer();
1131                         $this->connLogger->debug( "Closing connection to database '$host'." );
1132                         $conn->close();
1133                 } );
1134
1135                 $this->mConns = [
1136                         self::KEY_LOCAL => [],
1137                         self::KEY_FOREIGN_INUSE => [],
1138                         self::KEY_FOREIGN_FREE => [],
1139                         self::KEY_LOCAL_NOROUND => [],
1140                         self::KEY_FOREIGN_INUSE_NOROUND => [],
1141                         self::KEY_FOREIGN_FREE_NOROUND => []
1142                 ];
1143                 $this->connsOpened = 0;
1144         }
1145
1146         public function closeConnection( IDatabase $conn ) {
1147                 $serverIndex = $conn->getLBInfo( 'serverIndex' ); // second index level of mConns
1148                 foreach ( $this->mConns as $type => $connsByServer ) {
1149                         if ( !isset( $connsByServer[$serverIndex] ) ) {
1150                                 continue;
1151                         }
1152
1153                         foreach ( $connsByServer[$serverIndex] as $i => $trackedConn ) {
1154                                 if ( $conn === $trackedConn ) {
1155                                         $host = $this->getServerName( $i );
1156                                         $this->connLogger->debug( "Closing connection to database $i at '$host'." );
1157                                         unset( $this->mConns[$type][$serverIndex][$i] );
1158                                         --$this->connsOpened;
1159                                         break 2;
1160                                 }
1161                         }
1162                 }
1163
1164                 $conn->close();
1165         }
1166
1167         public function commitAll( $fname = __METHOD__ ) {
1168                 $failures = [];
1169
1170                 $restore = ( $this->trxRoundId !== false );
1171                 $this->trxRoundId = false;
1172                 $this->forEachOpenConnection(
1173                         function ( IDatabase $conn ) use ( $fname, $restore, &$failures ) {
1174                                 try {
1175                                         $conn->commit( $fname, $conn::FLUSHING_ALL_PEERS );
1176                                 } catch ( DBError $e ) {
1177                                         call_user_func( $this->errorLogger, $e );
1178                                         $failures[] = "{$conn->getServer()}: {$e->getMessage()}";
1179                                 }
1180                                 if ( $restore && $conn->getLBInfo( 'master' ) ) {
1181                                         $this->undoTransactionRoundFlags( $conn );
1182                                 }
1183                         }
1184                 );
1185
1186                 if ( $failures ) {
1187                         throw new DBExpectedError(
1188                                 null,
1189                                 "Commit failed on server(s) " . implode( "\n", array_unique( $failures ) )
1190                         );
1191                 }
1192         }
1193
1194         public function finalizeMasterChanges() {
1195                 $this->forEachOpenMasterConnection( function ( Database $conn ) {
1196                         // Any error should cause all DB transactions to be rolled back together
1197                         $conn->setTrxEndCallbackSuppression( false );
1198                         $conn->runOnTransactionPreCommitCallbacks();
1199                         // Defer post-commit callbacks until COMMIT finishes for all DBs
1200                         $conn->setTrxEndCallbackSuppression( true );
1201                 } );
1202         }
1203
1204         public function approveMasterChanges( array $options ) {
1205                 $limit = isset( $options['maxWriteDuration'] ) ? $options['maxWriteDuration'] : 0;
1206                 $this->forEachOpenMasterConnection( function ( IDatabase $conn ) use ( $limit ) {
1207                         // If atomic sections or explicit transactions are still open, some caller must have
1208                         // caught an exception but failed to properly rollback any changes. Detect that and
1209                         // throw and error (causing rollback).
1210                         if ( $conn->explicitTrxActive() ) {
1211                                 throw new DBTransactionError(
1212                                         $conn,
1213                                         "Explicit transaction still active. A caller may have caught an error."
1214                                 );
1215                         }
1216                         // Assert that the time to replicate the transaction will be sane.
1217                         // If this fails, then all DB transactions will be rollback back together.
1218                         $time = $conn->pendingWriteQueryDuration( $conn::ESTIMATE_DB_APPLY );
1219                         if ( $limit > 0 && $time > $limit ) {
1220                                 throw new DBTransactionSizeError(
1221                                         $conn,
1222                                         "Transaction spent $time second(s) in writes, exceeding the limit of $limit.",
1223                                         [ $time, $limit ]
1224                                 );
1225                         }
1226                         // If a connection sits idle while slow queries execute on another, that connection
1227                         // may end up dropped before the commit round is reached. Ping servers to detect this.
1228                         if ( $conn->writesOrCallbacksPending() && !$conn->ping() ) {
1229                                 throw new DBTransactionError(
1230                                         $conn,
1231                                         "A connection to the {$conn->getDBname()} database was lost before commit."
1232                                 );
1233                         }
1234                 } );
1235         }
1236
1237         public function beginMasterChanges( $fname = __METHOD__ ) {
1238                 if ( $this->trxRoundId !== false ) {
1239                         throw new DBTransactionError(
1240                                 null,
1241                                 "$fname: Transaction round '{$this->trxRoundId}' already started."
1242                         );
1243                 }
1244                 $this->trxRoundId = $fname;
1245
1246                 $failures = [];
1247                 $this->forEachOpenMasterConnection(
1248                         function ( Database $conn ) use ( $fname, &$failures ) {
1249                                 $conn->setTrxEndCallbackSuppression( true );
1250                                 try {
1251                                         $conn->flushSnapshot( $fname );
1252                                 } catch ( DBError $e ) {
1253                                         call_user_func( $this->errorLogger, $e );
1254                                         $failures[] = "{$conn->getServer()}: {$e->getMessage()}";
1255                                 }
1256                                 $conn->setTrxEndCallbackSuppression( false );
1257                                 $this->applyTransactionRoundFlags( $conn );
1258                         }
1259                 );
1260
1261                 if ( $failures ) {
1262                         throw new DBExpectedError(
1263                                 null,
1264                                 "$fname: Flush failed on server(s) " . implode( "\n", array_unique( $failures ) )
1265                         );
1266                 }
1267         }
1268
1269         public function commitMasterChanges( $fname = __METHOD__ ) {
1270                 $failures = [];
1271
1272                 /** @noinspection PhpUnusedLocalVariableInspection */
1273                 $scope = $this->getScopedPHPBehaviorForCommit(); // try to ignore client aborts
1274
1275                 $restore = ( $this->trxRoundId !== false );
1276                 $this->trxRoundId = false;
1277                 $this->forEachOpenMasterConnection(
1278                         function ( IDatabase $conn ) use ( $fname, $restore, &$failures ) {
1279                                 try {
1280                                         if ( $conn->writesOrCallbacksPending() ) {
1281                                                 $conn->commit( $fname, $conn::FLUSHING_ALL_PEERS );
1282                                         } elseif ( $restore ) {
1283                                                 $conn->flushSnapshot( $fname );
1284                                         }
1285                                 } catch ( DBError $e ) {
1286                                         call_user_func( $this->errorLogger, $e );
1287                                         $failures[] = "{$conn->getServer()}: {$e->getMessage()}";
1288                                 }
1289                                 if ( $restore ) {
1290                                         $this->undoTransactionRoundFlags( $conn );
1291                                 }
1292                         }
1293                 );
1294
1295                 if ( $failures ) {
1296                         throw new DBExpectedError(
1297                                 null,
1298                                 "$fname: Commit failed on server(s) " . implode( "\n", array_unique( $failures ) )
1299                         );
1300                 }
1301         }
1302
1303         public function runMasterPostTrxCallbacks( $type ) {
1304                 $e = null; // first exception
1305                 $this->forEachOpenMasterConnection( function ( Database $conn ) use ( $type, &$e ) {
1306                         $conn->setTrxEndCallbackSuppression( false );
1307                         if ( $conn->writesOrCallbacksPending() ) {
1308                                 // This happens if onTransactionIdle() callbacks leave callbacks on *another* DB
1309                                 // (which finished its callbacks already). Warn and recover in this case. Let the
1310                                 // callbacks run in the final commitMasterChanges() in LBFactory::shutdown().
1311                                 $this->queryLogger->info( __METHOD__ . ": found writes/callbacks pending." );
1312                                 return;
1313                         } elseif ( $conn->trxLevel() ) {
1314                                 // This happens for single-DB setups where DB_REPLICA uses the master DB,
1315                                 // thus leaving an implicit read-only transaction open at this point. It
1316                                 // also happens if onTransactionIdle() callbacks leave implicit transactions
1317                                 // open on *other* DBs (which is slightly improper). Let these COMMIT on the
1318                                 // next call to commitMasterChanges(), possibly in LBFactory::shutdown().
1319                                 return;
1320                         }
1321                         try {
1322                                 $conn->runOnTransactionIdleCallbacks( $type );
1323                         } catch ( Exception $ex ) {
1324                                 $e = $e ?: $ex;
1325                         }
1326                         try {
1327                                 $conn->runTransactionListenerCallbacks( $type );
1328                         } catch ( Exception $ex ) {
1329                                 $e = $e ?: $ex;
1330                         }
1331                 } );
1332
1333                 return $e;
1334         }
1335
1336         public function rollbackMasterChanges( $fname = __METHOD__ ) {
1337                 $restore = ( $this->trxRoundId !== false );
1338                 $this->trxRoundId = false;
1339                 $this->forEachOpenMasterConnection(
1340                         function ( IDatabase $conn ) use ( $fname, $restore ) {
1341                                 if ( $conn->writesOrCallbacksPending() ) {
1342                                         $conn->rollback( $fname, $conn::FLUSHING_ALL_PEERS );
1343                                 }
1344                                 if ( $restore ) {
1345                                         $this->undoTransactionRoundFlags( $conn );
1346                                 }
1347                         }
1348                 );
1349         }
1350
1351         public function suppressTransactionEndCallbacks() {
1352                 $this->forEachOpenMasterConnection( function ( Database $conn ) {
1353                         $conn->setTrxEndCallbackSuppression( true );
1354                 } );
1355         }
1356
1357         /**
1358          * @param IDatabase $conn
1359          */
1360         private function applyTransactionRoundFlags( IDatabase $conn ) {
1361                 if ( $conn->getLBInfo( 'autoCommitOnly' ) ) {
1362                         return; // transaction rounds do not apply to these connections
1363                 }
1364
1365                 if ( $conn->getFlag( $conn::DBO_DEFAULT ) ) {
1366                         // DBO_TRX is controlled entirely by CLI mode presence with DBO_DEFAULT.
1367                         // Force DBO_TRX even in CLI mode since a commit round is expected soon.
1368                         $conn->setFlag( $conn::DBO_TRX, $conn::REMEMBER_PRIOR );
1369                         // If config has explicitly requested DBO_TRX be either on or off by not
1370                         // setting DBO_DEFAULT, then respect that. Forcing no transactions is useful
1371                         // for things like blob stores (ExternalStore) which want auto-commit mode.
1372                 }
1373         }
1374
1375         /**
1376          * @param IDatabase $conn
1377          */
1378         private function undoTransactionRoundFlags( IDatabase $conn ) {
1379                 if ( $conn->getLBInfo( 'autoCommitOnly' ) ) {
1380                         return; // transaction rounds do not apply to these connections
1381                 }
1382
1383                 if ( $conn->getFlag( $conn::DBO_DEFAULT ) ) {
1384                         $conn->restoreFlags( $conn::RESTORE_PRIOR );
1385                 }
1386         }
1387
1388         public function flushReplicaSnapshots( $fname = __METHOD__ ) {
1389                 $this->forEachOpenReplicaConnection( function ( IDatabase $conn ) {
1390                         $conn->flushSnapshot( __METHOD__ );
1391                 } );
1392         }
1393
1394         public function hasMasterConnection() {
1395                 return $this->isOpen( $this->getWriterIndex() );
1396         }
1397
1398         public function hasMasterChanges() {
1399                 $pending = 0;
1400                 $this->forEachOpenMasterConnection( function ( IDatabase $conn ) use ( &$pending ) {
1401                         $pending |= $conn->writesOrCallbacksPending();
1402                 } );
1403
1404                 return (bool)$pending;
1405         }
1406
1407         public function lastMasterChangeTimestamp() {
1408                 $lastTime = false;
1409                 $this->forEachOpenMasterConnection( function ( IDatabase $conn ) use ( &$lastTime ) {
1410                         $lastTime = max( $lastTime, $conn->lastDoneWrites() );
1411                 } );
1412
1413                 return $lastTime;
1414         }
1415
1416         public function hasOrMadeRecentMasterChanges( $age = null ) {
1417                 $age = ( $age === null ) ? $this->mWaitTimeout : $age;
1418
1419                 return ( $this->hasMasterChanges()
1420                         || $this->lastMasterChangeTimestamp() > microtime( true ) - $age );
1421         }
1422
1423         public function pendingMasterChangeCallers() {
1424                 $fnames = [];
1425                 $this->forEachOpenMasterConnection( function ( IDatabase $conn ) use ( &$fnames ) {
1426                         $fnames = array_merge( $fnames, $conn->pendingWriteCallers() );
1427                 } );
1428
1429                 return $fnames;
1430         }
1431
1432         public function getLaggedReplicaMode( $domain = false ) {
1433                 // No-op if there is only one DB (also avoids recursion)
1434                 if ( !$this->laggedReplicaMode && $this->getServerCount() > 1 ) {
1435                         try {
1436                                 // See if laggedReplicaMode gets set
1437                                 $conn = $this->getConnection( self::DB_REPLICA, false, $domain );
1438                                 $this->reuseConnection( $conn );
1439                         } catch ( DBConnectionError $e ) {
1440                                 // Avoid expensive re-connect attempts and failures
1441                                 $this->allReplicasDownMode = true;
1442                                 $this->laggedReplicaMode = true;
1443                         }
1444                 }
1445
1446                 return $this->laggedReplicaMode;
1447         }
1448
1449         /**
1450          * @param bool $domain
1451          * @return bool
1452          * @deprecated 1.28; use getLaggedReplicaMode()
1453          */
1454         public function getLaggedSlaveMode( $domain = false ) {
1455                 return $this->getLaggedReplicaMode( $domain );
1456         }
1457
1458         public function laggedReplicaUsed() {
1459                 return $this->laggedReplicaMode;
1460         }
1461
1462         /**
1463          * @return bool
1464          * @since 1.27
1465          * @deprecated Since 1.28; use laggedReplicaUsed()
1466          */
1467         public function laggedSlaveUsed() {
1468                 return $this->laggedReplicaUsed();
1469         }
1470
1471         public function getReadOnlyReason( $domain = false, IDatabase $conn = null ) {
1472                 if ( $this->readOnlyReason !== false ) {
1473                         return $this->readOnlyReason;
1474                 } elseif ( $this->getLaggedReplicaMode( $domain ) ) {
1475                         if ( $this->allReplicasDownMode ) {
1476                                 return 'The database has been automatically locked ' .
1477                                         'until the replica database servers become available';
1478                         } else {
1479                                 return 'The database has been automatically locked ' .
1480                                         'while the replica database servers catch up to the master.';
1481                         }
1482                 } elseif ( $this->masterRunningReadOnly( $domain, $conn ) ) {
1483                         return 'The database master is running in read-only mode.';
1484                 }
1485
1486                 return false;
1487         }
1488
1489         /**
1490          * @param string $domain Domain ID, or false for the current domain
1491          * @param IDatabase|null $conn DB master connectionl used to avoid loops [optional]
1492          * @return bool
1493          */
1494         private function masterRunningReadOnly( $domain, IDatabase $conn = null ) {
1495                 $cache = $this->wanCache;
1496                 $masterServer = $this->getServerName( $this->getWriterIndex() );
1497
1498                 return (bool)$cache->getWithSetCallback(
1499                         $cache->makeGlobalKey( __CLASS__, 'server-read-only', $masterServer ),
1500                         self::TTL_CACHE_READONLY,
1501                         function () use ( $domain, $conn ) {
1502                                 $old = $this->trxProfiler->setSilenced( true );
1503                                 try {
1504                                         $dbw = $conn ?: $this->getConnection( self::DB_MASTER, [], $domain );
1505                                         $readOnly = (int)$dbw->serverIsReadOnly();
1506                                         if ( !$conn ) {
1507                                                 $this->reuseConnection( $dbw );
1508                                         }
1509                                 } catch ( DBError $e ) {
1510                                         $readOnly = 0;
1511                                 }
1512                                 $this->trxProfiler->setSilenced( $old );
1513                                 return $readOnly;
1514                         },
1515                         [ 'pcTTL' => $cache::TTL_PROC_LONG, 'busyValue' => 0 ]
1516                 );
1517         }
1518
1519         public function allowLagged( $mode = null ) {
1520                 if ( $mode === null ) {
1521                         return $this->mAllowLagged;
1522                 }
1523                 $this->mAllowLagged = $mode;
1524
1525                 return $this->mAllowLagged;
1526         }
1527
1528         public function pingAll() {
1529                 $success = true;
1530                 $this->forEachOpenConnection( function ( IDatabase $conn ) use ( &$success ) {
1531                         if ( !$conn->ping() ) {
1532                                 $success = false;
1533                         }
1534                 } );
1535
1536                 return $success;
1537         }
1538
1539         public function forEachOpenConnection( $callback, array $params = [] ) {
1540                 foreach ( $this->mConns as $connsByServer ) {
1541                         foreach ( $connsByServer as $serverConns ) {
1542                                 foreach ( $serverConns as $conn ) {
1543                                         $mergedParams = array_merge( [ $conn ], $params );
1544                                         call_user_func_array( $callback, $mergedParams );
1545                                 }
1546                         }
1547                 }
1548         }
1549
1550         public function forEachOpenMasterConnection( $callback, array $params = [] ) {
1551                 $masterIndex = $this->getWriterIndex();
1552                 foreach ( $this->mConns as $connsByServer ) {
1553                         if ( isset( $connsByServer[$masterIndex] ) ) {
1554                                 /** @var IDatabase $conn */
1555                                 foreach ( $connsByServer[$masterIndex] as $conn ) {
1556                                         $mergedParams = array_merge( [ $conn ], $params );
1557                                         call_user_func_array( $callback, $mergedParams );
1558                                 }
1559                         }
1560                 }
1561         }
1562
1563         public function forEachOpenReplicaConnection( $callback, array $params = [] ) {
1564                 foreach ( $this->mConns as $connsByServer ) {
1565                         foreach ( $connsByServer as $i => $serverConns ) {
1566                                 if ( $i === $this->getWriterIndex() ) {
1567                                         continue; // skip master
1568                                 }
1569                                 foreach ( $serverConns as $conn ) {
1570                                         $mergedParams = array_merge( [ $conn ], $params );
1571                                         call_user_func_array( $callback, $mergedParams );
1572                                 }
1573                         }
1574                 }
1575         }
1576
1577         public function getMaxLag( $domain = false ) {
1578                 $maxLag = -1;
1579                 $host = '';
1580                 $maxIndex = 0;
1581
1582                 if ( $this->getServerCount() <= 1 ) {
1583                         return [ $host, $maxLag, $maxIndex ]; // no replication = no lag
1584                 }
1585
1586                 $lagTimes = $this->getLagTimes( $domain );
1587                 foreach ( $lagTimes as $i => $lag ) {
1588                         if ( $this->mLoads[$i] > 0 && $lag > $maxLag ) {
1589                                 $maxLag = $lag;
1590                                 $host = $this->mServers[$i]['host'];
1591                                 $maxIndex = $i;
1592                         }
1593                 }
1594
1595                 return [ $host, $maxLag, $maxIndex ];
1596         }
1597
1598         public function getLagTimes( $domain = false ) {
1599                 if ( $this->getServerCount() <= 1 ) {
1600                         return [ $this->getWriterIndex() => 0 ]; // no replication = no lag
1601                 }
1602
1603                 $knownLagTimes = []; // map of (server index => 0 seconds)
1604                 $indexesWithLag = [];
1605                 foreach ( $this->mServers as $i => $server ) {
1606                         if ( empty( $server['is static'] ) ) {
1607                                 $indexesWithLag[] = $i; // DB server might have replication lag
1608                         } else {
1609                                 $knownLagTimes[$i] = 0; // DB server is a non-replicating and read-only archive
1610                         }
1611                 }
1612
1613                 return $this->getLoadMonitor()->getLagTimes( $indexesWithLag, $domain ) + $knownLagTimes;
1614         }
1615
1616         public function safeGetLag( IDatabase $conn ) {
1617                 if ( $this->getServerCount() <= 1 ) {
1618                         return 0;
1619                 } else {
1620                         return $conn->getLag();
1621                 }
1622         }
1623
1624         /**
1625          * @param IDatabase $conn
1626          * @param DBMasterPos|bool $pos
1627          * @param int $timeout
1628          * @return bool
1629          */
1630         public function safeWaitForMasterPos( IDatabase $conn, $pos = false, $timeout = 10 ) {
1631                 if ( $this->getServerCount() <= 1 || !$conn->getLBInfo( 'replica' ) ) {
1632                         return true; // server is not a replica DB
1633                 }
1634
1635                 if ( !$pos ) {
1636                         // Get the current master position, opening a connection if needed
1637                         $masterConn = $this->getAnyOpenConnection( $this->getWriterIndex() );
1638                         if ( $masterConn ) {
1639                                 $pos = $masterConn->getMasterPos();
1640                         } else {
1641                                 $masterConn = $this->openConnection( $this->getWriterIndex(), self::DOMAIN_ANY );
1642                                 $pos = $masterConn->getMasterPos();
1643                                 $this->closeConnection( $masterConn );
1644                         }
1645                 }
1646
1647                 if ( $pos instanceof DBMasterPos ) {
1648                         $result = $conn->masterPosWait( $pos, $timeout );
1649                         if ( $result == -1 || is_null( $result ) ) {
1650                                 $msg = __METHOD__ . ': Timed out waiting on {host} pos {pos}';
1651                                 $this->replLogger->warning( $msg,
1652                                         [ 'host' => $conn->getServer(), 'pos' => $pos ] );
1653                                 $ok = false;
1654                         } else {
1655                                 $this->replLogger->info( __METHOD__ . ': Done' );
1656                                 $ok = true;
1657                         }
1658                 } else {
1659                         $ok = false; // something is misconfigured
1660                         $this->replLogger->error( 'Could not get master pos for {host}',
1661                                 [ 'host' => $conn->getServer() ] );
1662                 }
1663
1664                 return $ok;
1665         }
1666
1667         public function setTransactionListener( $name, callable $callback = null ) {
1668                 if ( $callback ) {
1669                         $this->trxRecurringCallbacks[$name] = $callback;
1670                 } else {
1671                         unset( $this->trxRecurringCallbacks[$name] );
1672                 }
1673                 $this->forEachOpenMasterConnection(
1674                         function ( IDatabase $conn ) use ( $name, $callback ) {
1675                                 $conn->setTransactionListener( $name, $callback );
1676                         }
1677                 );
1678         }
1679
1680         public function setTableAliases( array $aliases ) {
1681                 $this->tableAliases = $aliases;
1682         }
1683
1684         public function setDomainPrefix( $prefix ) {
1685                 // Find connections to explicit foreign domains still marked as in-use...
1686                 $domainsInUse = [];
1687                 $this->forEachOpenConnection( function ( IDatabase $conn ) use ( &$domainsInUse ) {
1688                         // Once reuseConnection() is called on a handle, its reference count goes from 1 to 0.
1689                         // Until then, it is still in use by the caller (explicitly or via DBConnRef scope).
1690                         if ( $conn->getLBInfo( 'foreignPoolRefCount' ) > 0 ) {
1691                                 $domainsInUse[] = $conn->getDomainID();
1692                         }
1693                 } );
1694
1695                 // Do not switch connections to explicit foreign domains unless marked as safe
1696                 if ( $domainsInUse ) {
1697                         $domains = implode( ', ', $domainsInUse );
1698                         throw new DBUnexpectedError( null,
1699                                 "Foreign domain connections are still in use ($domains)." );
1700                 }
1701
1702                 $this->localDomain = new DatabaseDomain(
1703                         $this->localDomain->getDatabase(),
1704                         null,
1705                         $prefix
1706                 );
1707
1708                 $this->forEachOpenConnection( function ( IDatabase $db ) use ( $prefix ) {
1709                         $db->tablePrefix( $prefix );
1710                 } );
1711         }
1712
1713         /**
1714          * Make PHP ignore user aborts/disconnects until the returned
1715          * value leaves scope. This returns null and does nothing in CLI mode.
1716          *
1717          * @return ScopedCallback|null
1718          */
1719         final protected function getScopedPHPBehaviorForCommit() {
1720                 if ( PHP_SAPI != 'cli' ) { // https://bugs.php.net/bug.php?id=47540
1721                         $old = ignore_user_abort( true ); // avoid half-finished operations
1722                         return new ScopedCallback( function () use ( $old ) {
1723                                 ignore_user_abort( $old );
1724                         } );
1725                 }
1726
1727                 return null;
1728         }
1729
1730         function __destruct() {
1731                 // Avoid connection leaks for sanity
1732                 $this->disable();
1733         }
1734 }
1735
1736 class_alias( LoadBalancer::class, 'LoadBalancer' );