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