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