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