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