includes/libs/rdbms/loadbalancer/LoadBalancer.php

   1 <?php
   2 /**
   3  * Database load balancing manager
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License as published by
   7  * the Free Software Foundation; either version 2 of the License, or
   8  * (at your option) any later version.
   9  *
  10  * This program is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  13  * GNU General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU General Public License along
  16  * with this program; if not, write to the Free Software Foundation, Inc.,
  17  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  18  * http://www.gnu.org/copyleft/gpl.html
  19  *
  20  * @file
  21  * @ingroup Database
  22  */
  23 use Psr\Log\LoggerInterface;
  24 use Psr\Log\NullLogger;
  25 use Wikimedia\ScopedCallback;
  26 use Wikimedia\Rdbms\TransactionProfiler;
  27 use Wikimedia\Rdbms\ILoadMonitor;
  28 use Wikimedia\Rdbms\DatabaseDomain;
  29 use Wikimedia\Rdbms\ILoadBalancer;
  30
  31 /**
  32  * Database connection, tracking, load balancing, and transaction manager for a cluster
  33  *
  34  * @ingroup Database
  35  */
  36 class LoadBalancer implements ILoadBalancer {
  37         /** @var array[] Map of (server index => server config array) */
  38         private $mServers;
  39         /** @var IDatabase[][][] Map of local/foreignUsed/foreignFree => server index => IDatabase array */
  40         private $mConns;
  41         /** @var float[] Map of (server index => weight) */
  42         private $mLoads;
  43         /** @var array[] Map of (group => server index => weight) */
  44         private $mGroupLoads;
  45         /** @var bool Whether to disregard replica DB lag as a factor in replica DB selection */
  46         private $mAllowLagged;
  47         /** @var integer Seconds to spend waiting on replica DB lag to resolve */
  48         private $mWaitTimeout;
  49         /** @var array The LoadMonitor configuration */
  50         private $loadMonitorConfig;
  51         /** @var array[] $aliases Map of (table => (dbname, schema, prefix) map) */
  52         private $tableAliases = [];
  53
  54         /** @var ILoadMonitor */
  55         private $loadMonitor;
  56         /** @var BagOStuff */
  57         private $srvCache;
  58         /** @var BagOStuff */
  59         private $memCache;
  60         /** @var WANObjectCache */
  61         private $wanCache;
  62         /** @var object|string Class name or object With profileIn/profileOut methods */
  63         protected $profiler;
  64         /** @var TransactionProfiler */
  65         protected $trxProfiler;
  66         /** @var LoggerInterface */
  67         protected $replLogger;
  68         /** @var LoggerInterface */
  69         protected $connLogger;
  70         /** @var LoggerInterface */
  71         protected $queryLogger;
  72         /** @var LoggerInterface */
  73         protected $perfLogger;
  74
  75         /** @var bool|IDatabase Database connection that caused a problem */
  76         private $mErrorConnection;
  77         /** @var integer The generic (not query grouped) replica DB index (of $mServers) */
  78         private $mReadIndex;
  79         /** @var bool|DBMasterPos False if not set */
  80         private $mWaitForPos;
  81         /** @var bool Whether the generic reader fell back to a lagged replica DB */
  82         private $laggedReplicaMode = false;
  83         /** @var bool Whether the generic reader fell back to a lagged replica DB */
  84         private $allReplicasDownMode = false;
  85         /** @var string The last DB selection or connection error */
  86         private $mLastError = 'Unknown error';
  87         /** @var string|bool Reason the LB is read-only or false if not */
  88         private $readOnlyReason = false;
  89         /** @var integer Total connections opened */
  90         private $connsOpened = 0;
  91         /** @var string|bool String if a requested DBO_TRX transaction round is active */
  92         private $trxRoundId = false;
  93         /** @var array[] Map of (name => callable) */
  94         private $trxRecurringCallbacks = [];
  95         /** @var DatabaseDomain Local Domain ID and default for selectDB() calls */
  96         private $localDomain;
  97         /** @var string Alternate ID string for the domain instead of DatabaseDomain::getId() */
  98         private $localDomainIdAlias;
  99         /** @var string Current server name */
 100         private $host;
 101         /** @var bool Whether this PHP instance is for a CLI script */
 102         protected $cliMode;
 103         /** @var string Agent name for query profiling */
 104         protected $agent;
 105
 106         /** @var callable Exception logger */
 107         private $errorLogger;
 108
 109         /** @var boolean */
 110         private $disabled = false;
 111
 112         /** @var integer Warn when this many connection are held */
 113         const CONN_HELD_WARN_THRESHOLD = 10;
 114
 115         /** @var integer Default 'max lag' when unspecified */
 116         const MAX_LAG_DEFAULT = 10;
 117         /** @var integer Seconds to cache master server read-only status */
 118         const TTL_CACHE_READONLY = 5;
 119
 120         public function __construct( array $params ) {
 121                 if ( !isset( $params['servers'] ) ) {
 122                         throw new InvalidArgumentException( __CLASS__ . ': missing servers parameter' );
 123                 }
 124                 $this->mServers = $params['servers'];
 125
 126                 $this->localDomain = isset( $params['localDomain'] )
 127                         ? DatabaseDomain::newFromId( $params['localDomain'] )
 128                         : DatabaseDomain::newUnspecified();
 129                 // In case a caller assumes that the domain ID is simply <db>-<prefix>, which is almost
 130                 // always true, gracefully handle the case when they fail to account for escaping.
 131                 if ( $this->localDomain->getTablePrefix() != '' ) {
 132                         $this->localDomainIdAlias =
 133                                 $this->localDomain->getDatabase() . '-' . $this->localDomain->getTablePrefix();
 134                 } else {
 135                         $this->localDomainIdAlias = $this->localDomain->getDatabase();
 136                 }
 137
 138                 $this->mWaitTimeout = isset( $params['waitTimeout'] ) ? $params['waitTimeout'] : 10;
 139
 140                 $this->mReadIndex = -1;
 141                 $this->mConns = [
 142                         'local'       => [],
 143                         'foreignUsed' => [],
 144                         'foreignFree' => []
 145                 ];
 146                 $this->mLoads = [];
 147                 $this->mWaitForPos = false;
 148                 $this->mErrorConnection = false;
 149                 $this->mAllowLagged = false;
 150
 151                 if ( isset( $params['readOnlyReason'] ) && is_string( $params['readOnlyReason'] ) ) {
 152                         $this->readOnlyReason = $params['readOnlyReason'];
 153                 }
 154
 155                 if ( isset( $params['loadMonitor'] ) ) {
 156                         $this->loadMonitorConfig = $params['loadMonitor'];
 157                 } else {
 158                         $this->loadMonitorConfig = [ 'class' => 'LoadMonitorNull' ];
 159                 }
 160
 161                 foreach ( $params['servers'] as $i => $server ) {
 162                         $this->mLoads[$i] = $server['load'];
 163                         if ( isset( $server['groupLoads'] ) ) {
 164                                 foreach ( $server['groupLoads'] as $group => $ratio ) {
 165                                         if ( !isset( $this->mGroupLoads[$group] ) ) {
 166                                                 $this->mGroupLoads[$group] = [];
 167                                         }
 168                                         $this->mGroupLoads[$group][$i] = $ratio;
 169                                 }
 170                         }
 171                 }
 172
 173                 if ( isset( $params['srvCache'] ) ) {
 174                         $this->srvCache = $params['srvCache'];
 175                 } else {
 176                         $this->srvCache = new EmptyBagOStuff();
 177                 }
 178                 if ( isset( $params['memCache'] ) ) {
 179                         $this->memCache = $params['memCache'];
 180                 } else {
 181                         $this->memCache = new EmptyBagOStuff();
 182                 }
 183                 if ( isset( $params['wanCache'] ) ) {
 184                         $this->wanCache = $params['wanCache'];
 185                 } else {
 186                         $this->wanCache = WANObjectCache::newEmpty();
 187                 }
 188                 $this->profiler = isset( $params['profiler'] ) ? $params['profiler'] : null;
 189                 if ( isset( $params['trxProfiler'] ) ) {
 190                         $this->trxProfiler = $params['trxProfiler'];
 191                 } else {
 192                         $this->trxProfiler = new TransactionProfiler();
 193                 }
 194
 195                 $this->errorLogger = isset( $params['errorLogger'] )
 196                         ? $params['errorLogger']
 197                         : function ( Exception $e ) {
 198                                 trigger_error( get_class( $e ) . ': ' . $e->getMessage(), E_USER_WARNING );
 199                         };
 200
 201                 foreach ( [ 'replLogger', 'connLogger', 'queryLogger', 'perfLogger' ] as $key ) {
 202                         $this->$key = isset( $params[$key] ) ? $params[$key] : new NullLogger();
 203                 }
 204
 205                 $this->host = isset( $params['hostname'] )
 206                         ? $params['hostname']
 207                         : ( gethostname() ?: 'unknown' );
 208                 $this->cliMode = isset( $params['cliMode'] ) ? $params['cliMode'] : PHP_SAPI === 'cli';
 209                 $this->agent = isset( $params['agent'] ) ? $params['agent'] : '';
 210         }
 211
 212         /**
 213          * Get a LoadMonitor instance
 214          *
 215          * @return ILoadMonitor
 216          */
 217         private function getLoadMonitor() {
 218                 if ( !isset( $this->loadMonitor ) ) {
 219                         $compat = [
 220                                 'LoadMonitor' => Wikimedia\Rdbms\LoadMonitor::class,
 221                                 'LoadMonitorNull' => Wikimedia\Rdbms\LoadMonitorNull::class,
 222                                 'LoadMonitorMySQL' => Wikimedia\Rdbms\LoadMonitorMySQL::class,
 223                         ];
 224
 225                         $class = $this->loadMonitorConfig['class'];
 226                         if ( isset( $compat[$class] ) ) {
 227                                 $class = $compat[$class];
 228                         }
 229
 230                         $this->loadMonitor = new $class(
 231                                 $this, $this->srvCache, $this->memCache, $this->loadMonitorConfig );
 232                         $this->loadMonitor->setLogger( $this->replLogger );
 233                 }
 234
 235                 return $this->loadMonitor;
 236         }
 237
 238         /**
 239          * @param array $loads
 240          * @param bool|string $domain Domain to get non-lagged for
 241          * @param int $maxLag Restrict the maximum allowed lag to this many seconds
 242          * @return bool|int|string
 243          */
 244         private function getRandomNonLagged( array $loads, $domain = false, $maxLag = INF ) {
 245                 $lags = $this->getLagTimes( $domain );
 246
 247                 # Unset excessively lagged servers
 248                 foreach ( $lags as $i => $lag ) {
 249                         if ( $i != 0 ) {
 250                                 # How much lag this server nominally is allowed to have
 251                                 $maxServerLag = isset( $this->mServers[$i]['max lag'] )
 252                                         ? $this->mServers[$i]['max lag']
 253                                         : self::MAX_LAG_DEFAULT; // default
 254                                 # Constrain that futher by $maxLag argument
 255                                 $maxServerLag = min( $maxServerLag, $maxLag );
 256
 257                                 $host = $this->getServerName( $i );
 258                                 if ( $lag === false && !is_infinite( $maxServerLag ) ) {
 259                                         $this->replLogger->error(
 260                                                 "Server {host} (#$i) is not replicating?", [ 'host' => $host ] );
 261                                         unset( $loads[$i] );
 262                                 } elseif ( $lag > $maxServerLag ) {
 263                                         $this->replLogger->warning(
 264                                                 "Server {host} (#$i) has {lag} seconds of lag (>= {maxlag})",
 265                                                 [ 'host' => $host, 'lag' => $lag, 'maxlag' => $maxServerLag ]
 266                                         );
 267                                         unset( $loads[$i] );
 268                                 }
 269                         }
 270                 }
 271
 272                 # Find out if all the replica DBs with non-zero load are lagged
 273                 $sum = 0;
 274                 foreach ( $loads as $load ) {
 275                         $sum += $load;
 276                 }
 277                 if ( $sum == 0 ) {
 278                         # No appropriate DB servers except maybe the master and some replica DBs with zero load
 279                         # Do NOT use the master
 280                         # Instead, this function will return false, triggering read-only mode,
 281                         # and a lagged replica DB will be used instead.
 282                         return false;
 283                 }
 284
 285                 if ( count( $loads ) == 0 ) {
 286                         return false;
 287                 }
 288
 289                 # Return a random representative of the remainder
 290                 return ArrayUtils::pickRandom( $loads );
 291         }
 292
 293         public function getReaderIndex( $group = false, $domain = false ) {
 294                 if ( count( $this->mServers ) == 1 ) {
 295                         # Skip the load balancing if there's only one server
 296                         return $this->getWriterIndex();
 297                 } elseif ( $group === false && $this->mReadIndex >= 0 ) {
 298                         # Shortcut if generic reader exists already
 299                         return $this->mReadIndex;
 300                 }
 301
 302                 # Find the relevant load array
 303                 if ( $group !== false ) {
 304                         if ( isset( $this->mGroupLoads[$group] ) ) {
 305                                 $nonErrorLoads = $this->mGroupLoads[$group];
 306                         } else {
 307                                 # No loads for this group, return false and the caller can use some other group
 308                                 $this->connLogger->info( __METHOD__ . ": no loads for group $group" );
 309
 310                                 return false;
 311                         }
 312                 } else {
 313                         $nonErrorLoads = $this->mLoads;
 314                 }
 315
 316                 if ( !count( $nonErrorLoads ) ) {
 317                         throw new InvalidArgumentException( "Empty server array given to LoadBalancer" );
 318                 }
 319
 320                 # Scale the configured load ratios according to the dynamic load if supported
 321                 $this->getLoadMonitor()->scaleLoads( $nonErrorLoads, $domain );
 322
 323                 $laggedReplicaMode = false;
 324
 325                 # No server found yet
 326                 $i = false;
 327                 # First try quickly looking through the available servers for a server that
 328                 # meets our criteria
 329                 $currentLoads = $nonErrorLoads;
 330                 while ( count( $currentLoads ) ) {
 331                         if ( $this->mAllowLagged || $laggedReplicaMode ) {
 332                                 $i = ArrayUtils::pickRandom( $currentLoads );
 333                         } else {
 334                                 $i = false;
 335                                 if ( $this->mWaitForPos && $this->mWaitForPos->asOfTime() ) {
 336                                         # ChronologyProtecter causes mWaitForPos to be set via sessions.
 337                                         # This triggers doWait() after connect, so it's especially good to
 338                                         # avoid lagged servers so as to avoid just blocking in that method.
 339                                         $ago = microtime( true ) - $this->mWaitForPos->asOfTime();
 340                                         # Aim for <= 1 second of waiting (being too picky can backfire)
 341                                         $i = $this->getRandomNonLagged( $currentLoads, $domain, $ago + 1 );
 342                                 }
 343                                 if ( $i === false ) {
 344                                         # Any server with less lag than it's 'max lag' param is preferable
 345                                         $i = $this->getRandomNonLagged( $currentLoads, $domain );
 346                                 }
 347                                 if ( $i === false && count( $currentLoads ) != 0 ) {
 348                                         # All replica DBs lagged. Switch to read-only mode
 349                                         $this->replLogger->error( "All replica DBs lagged. Switch to read-only mode" );
 350                                         $i = ArrayUtils::pickRandom( $currentLoads );
 351                                         $laggedReplicaMode = true;
 352                                 }
 353                         }
 354
 355                         if ( $i === false ) {
 356                                 # pickRandom() returned false
 357                                 # This is permanent and means the configuration or the load monitor
 358                                 # wants us to return false.
 359                                 $this->connLogger->debug( __METHOD__ . ": pickRandom() returned false" );
 360
 361                                 return false;
 362                         }
 363
 364                         $serverName = $this->getServerName( $i );
 365                         $this->connLogger->debug( __METHOD__ . ": Using reader #$i: $serverName..." );
 366
 367                         $conn = $this->openConnection( $i, $domain );
 368                         if ( !$conn ) {
 369                                 $this->connLogger->warning( __METHOD__ . ": Failed connecting to $i/$domain" );
 370                                 unset( $nonErrorLoads[$i] );
 371                                 unset( $currentLoads[$i] );
 372                                 $i = false;
 373                                 continue;
 374                         }
 375
 376                         // Decrement reference counter, we are finished with this connection.
 377                         // It will be incremented for the caller later.
 378                         if ( $domain !== false ) {
 379                                 $this->reuseConnection( $conn );
 380                         }
 381
 382                         # Return this server
 383                         break;
 384                 }
 385
 386                 # If all servers were down, quit now
 387                 if ( !count( $nonErrorLoads ) ) {
 388                         $this->connLogger->error( "All servers down" );
 389                 }
 390
 391                 if ( $i !== false ) {
 392                         # Replica DB connection successful.
 393                         # Wait for the session master pos for a short time.
 394                         if ( $this->mWaitForPos && $i > 0 ) {
 395                                 $this->doWait( $i );
 396                         }
 397                         if ( $this->mReadIndex <= 0 && $this->mLoads[$i] > 0 && $group === false ) {
 398                                 $this->mReadIndex = $i;
 399                                 # Record if the generic reader index is in "lagged replica DB" mode
 400                                 if ( $laggedReplicaMode ) {
 401                                         $this->laggedReplicaMode = true;
 402                                 }
 403                         }
 404                         $serverName = $this->getServerName( $i );
 405                         $this->connLogger->debug(
 406                                 __METHOD__ . ": using server $serverName for group '$group'" );
 407                 }
 408
 409                 return $i;
 410         }
 411
 412         /**
 413          * @param DBMasterPos|false $pos
 414          */
 415         public function waitFor( $pos ) {
 416                 $this->mWaitForPos = $pos;
 417                 $i = $this->mReadIndex;
 418
 419                 if ( $i > 0 ) {
 420                         if ( !$this->doWait( $i ) ) {
 421                                 $this->laggedReplicaMode = true;
 422                         }
 423                 }
 424         }
 425
 426         public function waitForOne( $pos, $timeout = null ) {
 427                 $this->mWaitForPos = $pos;
 428
 429                 $i = $this->mReadIndex;
 430                 if ( $i <= 0 ) {
 431                         // Pick a generic replica DB if there isn't one yet
 432                         $readLoads = $this->mLoads;
 433                         unset( $readLoads[$this->getWriterIndex()] ); // replica DBs only
 434                         $readLoads = array_filter( $readLoads ); // with non-zero load
 435                         $i = ArrayUtils::pickRandom( $readLoads );
 436                 }
 437
 438                 if ( $i > 0 ) {
 439                         $ok = $this->doWait( $i, true, $timeout );
 440                 } else {
 441                         $ok = true; // no applicable loads
 442                 }
 443
 444                 return $ok;
 445         }
 446
 447         public function waitForAll( $pos, $timeout = null ) {
 448                 $this->mWaitForPos = $pos;
 449                 $serverCount = count( $this->mServers );
 450
 451                 $ok = true;
 452                 for ( $i = 1; $i < $serverCount; $i++ ) {
 453                         if ( $this->mLoads[$i] > 0 ) {
 454                                 $ok = $this->doWait( $i, true, $timeout ) && $ok;
 455                         }
 456                 }
 457
 458                 return $ok;
 459         }
 460
 461         /**
 462          * @param int $i
 463          * @return IDatabase|bool
 464          */
 465         public function getAnyOpenConnection( $i ) {
 466                 foreach ( $this->mConns as $connsByServer ) {
 467                         if ( !empty( $connsByServer[$i] ) ) {
 468                                 /** @var $serverConns IDatabase[] */
 469                                 $serverConns = $connsByServer[$i];
 470
 471                                 return reset( $serverConns );
 472                         }
 473                 }
 474
 475                 return false;
 476         }
 477
 478         /**
 479          * Wait for a given replica DB to catch up to the master pos stored in $this
 480          * @param int $index Server index
 481          * @param bool $open Check the server even if a new connection has to be made
 482          * @param int $timeout Max seconds to wait; default is mWaitTimeout
 483          * @return bool
 484          */
 485         protected function doWait( $index, $open = false, $timeout = null ) {
 486                 $close = false; // close the connection afterwards
 487
 488                 // Check if we already know that the DB has reached this point
 489                 $server = $this->getServerName( $index );
 490                 $key = $this->srvCache->makeGlobalKey( __CLASS__, 'last-known-pos', $server );
 491                 /** @var DBMasterPos $knownReachedPos */
 492                 $knownReachedPos = $this->srvCache->get( $key );
 493                 if ( $knownReachedPos && $knownReachedPos->hasReached( $this->mWaitForPos ) ) {
 494                         $this->replLogger->debug( __METHOD__ .
 495                                 ": replica DB $server known to be caught up (pos >= $knownReachedPos)." );
 496                         return true;
 497                 }
 498
 499                 // Find a connection to wait on, creating one if needed and allowed
 500                 $conn = $this->getAnyOpenConnection( $index );
 501                 if ( !$conn ) {
 502                         if ( !$open ) {
 503                                 $this->replLogger->debug( __METHOD__ . ": no connection open for $server" );
 504
 505                                 return false;
 506                         } else {
 507                                 $conn = $this->openConnection( $index, self::DOMAIN_ANY );
 508                                 if ( !$conn ) {
 509                                         $this->replLogger->warning( __METHOD__ . ": failed to connect to $server" );
 510
 511                                         return false;
 512                                 }
 513                                 // Avoid connection spam in waitForAll() when connections
 514                                 // are made just for the sake of doing this lag check.
 515                                 $close = true;
 516                         }
 517                 }
 518
 519                 $this->replLogger->info( __METHOD__ . ": Waiting for replica DB $server to catch up..." );
 520                 $timeout = $timeout ?: $this->mWaitTimeout;
 521                 $result = $conn->masterPosWait( $this->mWaitForPos, $timeout );
 522
 523                 if ( $result == -1 || is_null( $result ) ) {
 524                         // Timed out waiting for replica DB, use master instead
 525                         $this->replLogger->warning(
 526                                 __METHOD__ . ": Timed out waiting on {host} pos {$this->mWaitForPos}",
 527                                 [ 'host' => $server ]
 528                         );
 529                         $ok = false;
 530                 } else {
 531                         $this->replLogger->info( __METHOD__ . ": Done" );
 532                         $ok = true;
 533                         // Remember that the DB reached this point
 534                         $this->srvCache->set( $key, $this->mWaitForPos, BagOStuff::TTL_DAY );
 535                 }
 536
 537                 if ( $close ) {
 538                         $this->closeConnection( $conn );
 539                 }
 540
 541                 return $ok;
 542         }
 543
 544         /**
 545          * @see ILoadBalancer::getConnection()
 546          *
 547          * @param int $i
 548          * @param array $groups
 549          * @param bool $domain
 550          * @return Database
 551          * @throws DBConnectionError
 552          */
 553         public function getConnection( $i, $groups = [], $domain = false ) {
 554                 if ( $i === null || $i === false ) {
 555                         throw new InvalidArgumentException( 'Attempt to call ' . __METHOD__ .
 556                                 ' with invalid server index' );
 557                 }
 558
 559                 if ( $this->localDomain->equals( $domain ) || $domain === $this->localDomainIdAlias ) {
 560                         $domain = false; // local connection requested
 561                 }
 562
 563                 $groups = ( $groups === false || $groups === [] )
 564                         ? [ false ] // check one "group": the generic pool
 565                         : (array)$groups;
 566
 567                 $masterOnly = ( $i == self::DB_MASTER || $i == $this->getWriterIndex() );
 568                 $oldConnsOpened = $this->connsOpened; // connections open now
 569
 570                 if ( $i == self::DB_MASTER ) {
 571                         $i = $this->getWriterIndex();
 572                 } else {
 573                         # Try to find an available server in any the query groups (in order)
 574                         foreach ( $groups as $group ) {
 575                                 $groupIndex = $this->getReaderIndex( $group, $domain );
 576                                 if ( $groupIndex !== false ) {
 577                                         $i = $groupIndex;
 578                                         break;
 579                                 }
 580                         }
 581                 }
 582
 583                 # Operation-based index
 584                 if ( $i == self::DB_REPLICA ) {
 585                         $this->mLastError = 'Unknown error'; // reset error string
 586                         # Try the general server pool if $groups are unavailable.
 587                         $i = ( $groups === [ false ] )
 588                                 ? false // don't bother with this if that is what was tried above
 589                                 : $this->getReaderIndex( false, $domain );
 590                         # Couldn't find a working server in getReaderIndex()?
 591                         if ( $i === false ) {
 592                                 $this->mLastError = 'No working replica DB server: ' . $this->mLastError;
 593                                 // Throw an exception
 594                                 $this->reportConnectionError();
 595                                 return null; // not reached
 596                         }
 597                 }
 598
 599                 # Now we have an explicit index into the servers array
 600                 $conn = $this->openConnection( $i, $domain );
 601                 if ( !$conn ) {
 602                         // Throw an exception
 603                         $this->reportConnectionError();
 604                         return null; // not reached
 605                 }
 606
 607                 # Profile any new connections that happen
 608                 if ( $this->connsOpened > $oldConnsOpened ) {
 609                         $host = $conn->getServer();
 610                         $dbname = $conn->getDBname();
 611                         $this->trxProfiler->recordConnection( $host, $dbname, $masterOnly );
 612                 }
 613
 614                 if ( $masterOnly ) {
 615                         # Make master-requested DB handles inherit any read-only mode setting
 616                         $conn->setLBInfo( 'readOnlyReason', $this->getReadOnlyReason( $domain, $conn ) );
 617                 }
 618
 619                 return $conn;
 620         }
 621
 622         public function reuseConnection( $conn ) {
 623                 $serverIndex = $conn->getLBInfo( 'serverIndex' );
 624                 $refCount = $conn->getLBInfo( 'foreignPoolRefCount' );
 625                 if ( $serverIndex === null || $refCount === null ) {
 626                         /**
 627                          * This can happen in code like:
 628                          *   foreach ( $dbs as $db ) {
 629                          *     $conn = $lb->getConnection( $lb::DB_REPLICA, [], $db );
 630                          *     ...
 631                          *     $lb->reuseConnection( $conn );
 632                          *   }
 633                          * When a connection to the local DB is opened in this way, reuseConnection()
 634                          * should be ignored
 635                          */
 636                         return;
 637                 } elseif ( $conn instanceof DBConnRef ) {
 638                         // DBConnRef already handles calling reuseConnection() and only passes the live
 639                         // Database instance to this method. Any caller passing in a DBConnRef is broken.
 640                         $this->connLogger->error( __METHOD__ . ": got DBConnRef instance.\n" .
 641                                 ( new RuntimeException() )->getTraceAsString() );
 642
 643                         return;
 644                 }
 645
 646                 if ( $this->disabled ) {
 647                         return; // DBConnRef handle probably survived longer than the LoadBalancer
 648                 }
 649
 650                 $domain = $conn->getDomainID();
 651                 if ( !isset( $this->mConns['foreignUsed'][$serverIndex][$domain] ) ) {
 652                         throw new InvalidArgumentException( __METHOD__ .
 653                                 ": connection $serverIndex/$domain not found; it may have already been freed." );
 654                 } elseif ( $this->mConns['foreignUsed'][$serverIndex][$domain] !== $conn ) {
 655                         throw new InvalidArgumentException( __METHOD__ .
 656                                 ": connection $serverIndex/$domain mismatched; it may have already been freed." );
 657                 }
 658                 $conn->setLBInfo( 'foreignPoolRefCount', --$refCount );
 659                 if ( $refCount <= 0 ) {
 660                         $this->mConns['foreignFree'][$serverIndex][$domain] = $conn;
 661                         unset( $this->mConns['foreignUsed'][$serverIndex][$domain] );
 662                         if ( !$this->mConns['foreignUsed'][$serverIndex] ) {
 663                                 unset( $this->mConns[ 'foreignUsed' ][$serverIndex] ); // clean up
 664                         }
 665                         $this->connLogger->debug( __METHOD__ . ": freed connection $serverIndex/$domain" );
 666                 } else {
 667                         $this->connLogger->debug( __METHOD__ .
 668                                 ": reference count for $serverIndex/$domain reduced to $refCount" );
 669                 }
 670         }
 671
 672         public function getConnectionRef( $db, $groups = [], $domain = false ) {
 673                 $domain = ( $domain !== false ) ? $domain : $this->localDomain;
 674
 675                 return new DBConnRef( $this, $this->getConnection( $db, $groups, $domain ) );
 676         }
 677
 678         public function getLazyConnectionRef( $db, $groups = [], $domain = false ) {
 679                 $domain = ( $domain !== false ) ? $domain : $this->localDomain;
 680
 681                 return new DBConnRef( $this, [ $db, $groups, $domain ] );
 682         }
 683
 684         public function getMaintenanceConnectionRef( $db, $groups = [], $domain = false ) {
 685                 $domain = ( $domain !== false ) ? $domain : $this->localDomain;
 686
 687                 return new MaintainableDBConnRef( $this, $this->getConnection( $db, $groups, $domain ) );
 688         }
 689
 690         /**
 691          * @see ILoadBalancer::openConnection()
 692          *
 693          * @param int $i
 694          * @param bool $domain
 695          * @return bool|Database
 696          * @throws DBAccessError
 697          */
 698         public function openConnection( $i, $domain = false ) {
 699                 if ( $this->localDomain->equals( $domain ) || $domain === $this->localDomainIdAlias ) {
 700                         $domain = false; // local connection requested
 701                 }
 702
 703                 if ( $domain !== false ) {
 704                         $conn = $this->openForeignConnection( $i, $domain );
 705                 } elseif ( isset( $this->mConns['local'][$i][0] ) ) {
 706                         $conn = $this->mConns['local'][$i][0];
 707                 } else {
 708                         if ( !isset( $this->mServers[$i] ) || !is_array( $this->mServers[$i] ) ) {
 709                                 throw new InvalidArgumentException( "No server with index '$i'." );
 710                         }
 711                         // Open a new connection
 712                         $server = $this->mServers[$i];
 713                         $server['serverIndex'] = $i;
 714                         $conn = $this->reallyOpenConnection( $server, false );
 715                         $serverName = $this->getServerName( $i );
 716                         if ( $conn->isOpen() ) {
 717                                 $this->connLogger->debug( "Connected to database $i at '$serverName'." );
 718                                 $this->mConns['local'][$i][0] = $conn;
 719                         } else {
 720                                 $this->connLogger->warning( "Failed to connect to database $i at '$serverName'." );
 721                                 $this->mErrorConnection = $conn;
 722                                 $conn = false;
 723                         }
 724                 }
 725
 726                 if ( $conn && !$conn->isOpen() ) {
 727                         // Connection was made but later unrecoverably lost for some reason.
 728                         // Do not return a handle that will just throw exceptions on use,
 729                         // but let the calling code (e.g. getReaderIndex) try another server.
 730                         // See DatabaseMyslBase::ping() for how this can happen.
 731                         $this->mErrorConnection = $conn;
 732                         $conn = false;
 733                 }
 734
 735                 return $conn;
 736         }
 737
 738         /**
 739          * Open a connection to a foreign DB, or return one if it is already open.
 740          *
 741          * Increments a reference count on the returned connection which locks the
 742          * connection to the requested domain. This reference count can be
 743          * decremented by calling reuseConnection().
 744          *
 745          * If a connection is open to the appropriate server already, but with the wrong
 746          * database, it will be switched to the right database and returned, as long as
 747          * it has been freed first with reuseConnection().
 748          *
 749          * On error, returns false, and the connection which caused the
 750          * error will be available via $this->mErrorConnection.
 751          *
 752          * @note If disable() was called on this LoadBalancer, this method will throw a DBAccessError.
 753          *
 754          * @param int $i Server index
 755          * @param string $domain Domain ID to open
 756          * @return Database
 757          */
 758         private function openForeignConnection( $i, $domain ) {
 759                 $domainInstance = DatabaseDomain::newFromId( $domain );
 760                 $dbName = $domainInstance->getDatabase();
 761                 $prefix = $domainInstance->getTablePrefix();
 762
 763                 if ( isset( $this->mConns['foreignUsed'][$i][$domain] ) ) {
 764                         // Reuse an already-used connection
 765                         $conn = $this->mConns['foreignUsed'][$i][$domain];
 766                         $this->connLogger->debug( __METHOD__ . ": reusing connection $i/$domain" );
 767                 } elseif ( isset( $this->mConns['foreignFree'][$i][$domain] ) ) {
 768                         // Reuse a free connection for the same domain
 769                         $conn = $this->mConns['foreignFree'][$i][$domain];
 770                         unset( $this->mConns['foreignFree'][$i][$domain] );
 771                         $this->mConns['foreignUsed'][$i][$domain] = $conn;
 772                         $this->connLogger->debug( __METHOD__ . ": reusing free connection $i/$domain" );
 773                 } elseif ( !empty( $this->mConns['foreignFree'][$i] ) ) {
 774                         // Reuse a connection from another domain
 775                         $conn = reset( $this->mConns['foreignFree'][$i] );
 776                         $oldDomain = key( $this->mConns['foreignFree'][$i] );
 777                         // The empty string as a DB name means "don't care".
 778                         // DatabaseMysqlBase::open() already handle this on connection.
 779                         if ( strlen( $dbName ) && !$conn->selectDB( $dbName ) ) {
 780                                 $this->mLastError = "Error selecting database '$dbName' on server " .
 781                                         $conn->getServer() . " from client host {$this->host}";
 782                                 $this->mErrorConnection = $conn;
 783                                 $conn = false;
 784                         } else {
 785                                 $conn->tablePrefix( $prefix );
 786                                 unset( $this->mConns['foreignFree'][$i][$oldDomain] );
 787                                 $this->mConns['foreignUsed'][$i][$domain] = $conn;
 788                                 $this->connLogger->debug( __METHOD__ .
 789                                         ": reusing free connection from $oldDomain for $domain" );
 790                         }
 791                 } else {
 792                         if ( !isset( $this->mServers[$i] ) || !is_array( $this->mServers[$i] ) ) {
 793                                 throw new InvalidArgumentException( "No server with index '$i'." );
 794                         }
 795                         // Open a new connection
 796                         $server = $this->mServers[$i];
 797                         $server['serverIndex'] = $i;
 798                         $server['foreignPoolRefCount'] = 0;
 799                         $server['foreign'] = true;
 800                         $conn = $this->reallyOpenConnection( $server, $dbName );
 801                         if ( !$conn->isOpen() ) {
 802                                 $this->connLogger->warning( __METHOD__ . ": connection error for $i/$domain" );
 803                                 $this->mErrorConnection = $conn;
 804                                 $conn = false;
 805                         } else {
 806                                 $conn->tablePrefix( $prefix );
 807                                 $this->mConns['foreignUsed'][$i][$domain] = $conn;
 808                                 $this->connLogger->debug( __METHOD__ . ": opened new connection for $i/$domain" );
 809                         }
 810                 }
 811
 812                 // Increment reference count
 813                 if ( $conn ) {
 814                         $refCount = $conn->getLBInfo( 'foreignPoolRefCount' );
 815                         $conn->setLBInfo( 'foreignPoolRefCount', $refCount + 1 );
 816                 }
 817
 818                 return $conn;
 819         }
 820
 821         /**
 822          * Test if the specified index represents an open connection
 823          *
 824          * @param int $index Server index
 825          * @access private
 826          * @return bool
 827          */
 828         private function isOpen( $index ) {
 829                 if ( !is_integer( $index ) ) {
 830                         return false;
 831                 }
 832
 833                 return (bool)$this->getAnyOpenConnection( $index );
 834         }
 835
 836         /**
 837          * Really opens a connection. Uncached.
 838          * Returns a Database object whether or not the connection was successful.
 839          * @access private
 840          *
 841          * @param array $server
 842          * @param string|bool $dbNameOverride Use "" to not select any database
 843          * @return Database
 844          * @throws DBAccessError
 845          * @throws InvalidArgumentException
 846          */
 847         protected function reallyOpenConnection( array $server, $dbNameOverride = false ) {
 848                 if ( $this->disabled ) {
 849                         throw new DBAccessError();
 850                 }
 851
 852                 if ( $dbNameOverride !== false ) {
 853                         $server['dbname'] = $dbNameOverride;
 854                 }
 855
 856                 // Let the handle know what the cluster master is (e.g. "db1052")
 857                 $masterName = $this->getServerName( $this->getWriterIndex() );
 858                 $server['clusterMasterHost'] = $masterName;
 859
 860                 // Log when many connection are made on requests
 861                 if ( ++$this->connsOpened >= self::CONN_HELD_WARN_THRESHOLD ) {
 862                         $this->perfLogger->warning( __METHOD__ . ": " .
 863                                 "{$this->connsOpened}+ connections made (master=$masterName)" );
 864                 }
 865
 866                 $server['srvCache'] = $this->srvCache;
 867                 // Set loggers and profilers
 868                 $server['connLogger'] = $this->connLogger;
 869                 $server['queryLogger'] = $this->queryLogger;
 870                 $server['errorLogger'] = $this->errorLogger;
 871                 $server['profiler'] = $this->profiler;
 872                 $server['trxProfiler'] = $this->trxProfiler;
 873                 // Use the same agent and PHP mode for all DB handles
 874                 $server['cliMode'] = $this->cliMode;
 875                 $server['agent'] = $this->agent;
 876                 // Use DBO_DEFAULT flags by default for LoadBalancer managed databases. Assume that the
 877                 // application calls LoadBalancer::commitMasterChanges() before the PHP script completes.
 878                 $server['flags'] = isset( $server['flags'] ) ? $server['flags'] : IDatabase::DBO_DEFAULT;
 879
 880                 // Create a live connection object
 881                 try {
 882                         $db = Database::factory( $server['type'], $server );
 883                 } catch ( DBConnectionError $e ) {
 884                         // FIXME: This is probably the ugliest thing I have ever done to
 885                         // PHP. I'm half-expecting it to segfault, just out of disgust. -- TS
 886                         $db = $e->db;
 887                 }
 888
 889                 $db->setLBInfo( $server );
 890                 $db->setLazyMasterHandle(
 891                         $this->getLazyConnectionRef( self::DB_MASTER, [], $db->getDomainID() )
 892                 );
 893                 $db->setTableAliases( $this->tableAliases );
 894
 895                 if ( $server['serverIndex'] === $this->getWriterIndex() ) {
 896                         if ( $this->trxRoundId !== false ) {
 897                                 $this->applyTransactionRoundFlags( $db );
 898                         }
 899                         foreach ( $this->trxRecurringCallbacks as $name => $callback ) {
 900                                 $db->setTransactionListener( $name, $callback );
 901                         }
 902                 }
 903
 904                 return $db;
 905         }
 906
 907         /**
 908          * @throws DBConnectionError
 909          */
 910         private function reportConnectionError() {
 911                 $conn = $this->mErrorConnection; // the connection which caused the error
 912                 $context = [
 913                         'method' => __METHOD__,
 914                         'last_error' => $this->mLastError,
 915                 ];
 916
 917                 if ( !is_object( $conn ) ) {
 918                         // No last connection, probably due to all servers being too busy
 919                         $this->connLogger->error(
 920                                 "LB failure with no last connection. Connection error: {last_error}",
 921                                 $context
 922                         );
 923
 924                         // If all servers were busy, mLastError will contain something sensible
 925                         throw new DBConnectionError( null, $this->mLastError );
 926                 } else {
 927                         $context['db_server'] = $conn->getServer();
 928                         $this->connLogger->warning(
 929                                 "Connection error: {last_error} ({db_server})",
 930                                 $context
 931                         );
 932
 933                         // throws DBConnectionError
 934                         $conn->reportConnectionError( "{$this->mLastError} ({$context['db_server']})" );
 935                 }
 936         }
 937
 938         public function getWriterIndex() {
 939                 return 0;
 940         }
 941
 942         public function haveIndex( $i ) {
 943                 return array_key_exists( $i, $this->mServers );
 944         }
 945
 946         public function isNonZeroLoad( $i ) {
 947                 return array_key_exists( $i, $this->mServers ) && $this->mLoads[$i] != 0;
 948         }
 949
 950         public function getServerCount() {
 951                 return count( $this->mServers );
 952         }
 953
 954         public function getServerName( $i ) {
 955                 if ( isset( $this->mServers[$i]['hostName'] ) ) {
 956                         $name = $this->mServers[$i]['hostName'];
 957                 } elseif ( isset( $this->mServers[$i]['host'] ) ) {
 958                         $name = $this->mServers[$i]['host'];
 959                 } else {
 960                         $name = '';
 961                 }
 962
 963                 return ( $name != '' ) ? $name : 'localhost';
 964         }
 965
 966         public function getServerInfo( $i ) {
 967                 if ( isset( $this->mServers[$i] ) ) {
 968                         return $this->mServers[$i];
 969                 } else {
 970                         return false;
 971                 }
 972         }
 973
 974         public function setServerInfo( $i, array $serverInfo ) {
 975                 $this->mServers[$i] = $serverInfo;
 976         }
 977
 978         public function getMasterPos() {
 979                 # If this entire request was served from a replica DB without opening a connection to the
 980                 # master (however unlikely that may be), then we can fetch the position from the replica DB.
 981                 $masterConn = $this->getAnyOpenConnection( $this->getWriterIndex() );
 982                 if ( !$masterConn ) {
 983                         $serverCount = count( $this->mServers );
 984                         for ( $i = 1; $i < $serverCount; $i++ ) {
 985                                 $conn = $this->getAnyOpenConnection( $i );
 986                                 if ( $conn ) {
 987                                         return $conn->getReplicaPos();
 988                                 }
 989                         }
 990                 } else {
 991                         return $masterConn->getMasterPos();
 992                 }
 993
 994                 return false;
 995         }
 996
 997         public function disable() {
 998                 $this->closeAll();
 999                 $this->disabled = true;
1000         }
1001
1002         public function closeAll() {
1003                 $this->forEachOpenConnection( function ( IDatabase $conn ) {
1004                         $host = $conn->getServer();
1005                         $this->connLogger->debug( "Closing connection to database '$host'." );
1006                         $conn->close();
1007                 } );
1008
1009                 $this->mConns = [
1010                         'local' => [],
1011                         'foreignFree' => [],
1012                         'foreignUsed' => [],
1013                 ];
1014                 $this->connsOpened = 0;
1015         }
1016
1017         public function closeConnection( IDatabase $conn ) {
1018                 $serverIndex = $conn->getLBInfo( 'serverIndex' ); // second index level of mConns
1019                 foreach ( $this->mConns as $type => $connsByServer ) {
1020                         if ( !isset( $connsByServer[$serverIndex] ) ) {
1021                                 continue;
1022                         }
1023
1024                         foreach ( $connsByServer[$serverIndex] as $i => $trackedConn ) {
1025                                 if ( $conn === $trackedConn ) {
1026                                         $host = $this->getServerName( $i );
1027                                         $this->connLogger->debug( "Closing connection to database $i at '$host'." );
1028                                         unset( $this->mConns[$type][$serverIndex][$i] );
1029                                         --$this->connsOpened;
1030                                         break 2;
1031                                 }
1032                         }
1033                 }
1034
1035                 $conn->close();
1036         }
1037
1038         public function commitAll( $fname = __METHOD__ ) {
1039                 $failures = [];
1040
1041                 $restore = ( $this->trxRoundId !== false );
1042                 $this->trxRoundId = false;
1043                 $this->forEachOpenConnection(
1044                         function ( IDatabase $conn ) use ( $fname, $restore, &$failures ) {
1045                                 try {
1046                                         $conn->commit( $fname, $conn::FLUSHING_ALL_PEERS );
1047                                 } catch ( DBError $e ) {
1048                                         call_user_func( $this->errorLogger, $e );
1049                                         $failures[] = "{$conn->getServer()}: {$e->getMessage()}";
1050                                 }
1051                                 if ( $restore && $conn->getLBInfo( 'master' ) ) {
1052                                         $this->undoTransactionRoundFlags( $conn );
1053                                 }
1054                         }
1055                 );
1056
1057                 if ( $failures ) {
1058                         throw new DBExpectedError(
1059                                 null,
1060                                 "Commit failed on server(s) " . implode( "\n", array_unique( $failures ) )
1061                         );
1062                 }
1063         }
1064
1065         public function finalizeMasterChanges() {
1066                 $this->forEachOpenMasterConnection( function ( Database $conn ) {
1067                         // Any error should cause all DB transactions to be rolled back together
1068                         $conn->setTrxEndCallbackSuppression( false );
1069                         $conn->runOnTransactionPreCommitCallbacks();
1070                         // Defer post-commit callbacks until COMMIT finishes for all DBs
1071                         $conn->setTrxEndCallbackSuppression( true );
1072                 } );
1073         }
1074
1075         public function approveMasterChanges( array $options ) {
1076                 $limit = isset( $options['maxWriteDuration'] ) ? $options['maxWriteDuration'] : 0;
1077                 $this->forEachOpenMasterConnection( function ( IDatabase $conn ) use ( $limit ) {
1078                         // If atomic sections or explicit transactions are still open, some caller must have
1079                         // caught an exception but failed to properly rollback any changes. Detect that and
1080                         // throw and error (causing rollback).
1081                         if ( $conn->explicitTrxActive() ) {
1082                                 throw new DBTransactionError(
1083                                         $conn,
1084                                         "Explicit transaction still active. A caller may have caught an error."
1085                                 );
1086                         }
1087                         // Assert that the time to replicate the transaction will be sane.
1088                         // If this fails, then all DB transactions will be rollback back together.
1089                         $time = $conn->pendingWriteQueryDuration( $conn::ESTIMATE_DB_APPLY );
1090                         if ( $limit > 0 && $time > $limit ) {
1091                                 throw new DBTransactionSizeError(
1092                                         $conn,
1093                                         "Transaction spent $time second(s) in writes, exceeding the $limit limit.",
1094                                         [ $time, $limit ]
1095                                 );
1096                         }
1097                         // If a connection sits idle while slow queries execute on another, that connection
1098                         // may end up dropped before the commit round is reached. Ping servers to detect this.
1099                         if ( $conn->writesOrCallbacksPending() && !$conn->ping() ) {
1100                                 throw new DBTransactionError(
1101                                         $conn,
1102                                         "A connection to the {$conn->getDBname()} database was lost before commit."
1103                                 );
1104                         }
1105                 } );
1106         }
1107
1108         public function beginMasterChanges( $fname = __METHOD__ ) {
1109                 if ( $this->trxRoundId !== false ) {
1110                         throw new DBTransactionError(
1111                                 null,
1112                                 "$fname: Transaction round '{$this->trxRoundId}' already started."
1113                         );
1114                 }
1115                 $this->trxRoundId = $fname;
1116
1117                 $failures = [];
1118                 $this->forEachOpenMasterConnection(
1119                         function ( Database $conn ) use ( $fname, &$failures ) {
1120                                 $conn->setTrxEndCallbackSuppression( true );
1121                                 try {
1122                                         $conn->flushSnapshot( $fname );
1123                                 } catch ( DBError $e ) {
1124                                         call_user_func( $this->errorLogger, $e );
1125                                         $failures[] = "{$conn->getServer()}: {$e->getMessage()}";
1126                                 }
1127                                 $conn->setTrxEndCallbackSuppression( false );
1128                                 $this->applyTransactionRoundFlags( $conn );
1129                         }
1130                 );
1131
1132                 if ( $failures ) {
1133                         throw new DBExpectedError(
1134                                 null,
1135                                 "$fname: Flush failed on server(s) " . implode( "\n", array_unique( $failures ) )
1136                         );
1137                 }
1138         }
1139
1140         public function commitMasterChanges( $fname = __METHOD__ ) {
1141                 $failures = [];
1142
1143                 /** @noinspection PhpUnusedLocalVariableInspection */
1144                 $scope = $this->getScopedPHPBehaviorForCommit(); // try to ignore client aborts
1145
1146                 $restore = ( $this->trxRoundId !== false );
1147                 $this->trxRoundId = false;
1148                 $this->forEachOpenMasterConnection(
1149                         function ( IDatabase $conn ) use ( $fname, $restore, &$failures ) {
1150                                 try {
1151                                         if ( $conn->writesOrCallbacksPending() ) {
1152                                                 $conn->commit( $fname, $conn::FLUSHING_ALL_PEERS );
1153                                         } elseif ( $restore ) {
1154                                                 $conn->flushSnapshot( $fname );
1155                                         }
1156                                 } catch ( DBError $e ) {
1157                                         call_user_func( $this->errorLogger, $e );
1158                                         $failures[] = "{$conn->getServer()}: {$e->getMessage()}";
1159                                 }
1160                                 if ( $restore ) {
1161                                         $this->undoTransactionRoundFlags( $conn );
1162                                 }
1163                         }
1164                 );
1165
1166                 if ( $failures ) {
1167                         throw new DBExpectedError(
1168                                 null,
1169                                 "$fname: Commit failed on server(s) " . implode( "\n", array_unique( $failures ) )
1170                         );
1171                 }
1172         }
1173
1174         public function runMasterPostTrxCallbacks( $type ) {
1175                 $e = null; // first exception
1176                 $this->forEachOpenMasterConnection( function ( Database $conn ) use ( $type, &$e ) {
1177                         $conn->setTrxEndCallbackSuppression( false );
1178                         if ( $conn->writesOrCallbacksPending() ) {
1179                                 // This happens if onTransactionIdle() callbacks leave callbacks on *another* DB
1180                                 // (which finished its callbacks already). Warn and recover in this case. Let the
1181                                 // callbacks run in the final commitMasterChanges() in LBFactory::shutdown().
1182                                 $this->queryLogger->error( __METHOD__ . ": found writes/callbacks pending." );
1183                                 return;
1184                         } elseif ( $conn->trxLevel() ) {
1185                                 // This happens for single-DB setups where DB_REPLICA uses the master DB,
1186                                 // thus leaving an implicit read-only transaction open at this point. It
1187                                 // also happens if onTransactionIdle() callbacks leave implicit transactions
1188                                 // open on *other* DBs (which is slightly improper). Let these COMMIT on the
1189                                 // next call to commitMasterChanges(), possibly in LBFactory::shutdown().
1190                                 return;
1191                         }
1192                         try {
1193                                 $conn->runOnTransactionIdleCallbacks( $type );
1194                         } catch ( Exception $ex ) {
1195                                 $e = $e ?: $ex;
1196                         }
1197                         try {
1198                                 $conn->runTransactionListenerCallbacks( $type );
1199                         } catch ( Exception $ex ) {
1200                                 $e = $e ?: $ex;
1201                         }
1202                 } );
1203
1204                 return $e;
1205         }
1206
1207         public function rollbackMasterChanges( $fname = __METHOD__ ) {
1208                 $restore = ( $this->trxRoundId !== false );
1209                 $this->trxRoundId = false;
1210                 $this->forEachOpenMasterConnection(
1211                         function ( IDatabase $conn ) use ( $fname, $restore ) {
1212                                 if ( $conn->writesOrCallbacksPending() ) {
1213                                         $conn->rollback( $fname, $conn::FLUSHING_ALL_PEERS );
1214                                 }
1215                                 if ( $restore ) {
1216                                         $this->undoTransactionRoundFlags( $conn );
1217                                 }
1218                         }
1219                 );
1220         }
1221
1222         public function suppressTransactionEndCallbacks() {
1223                 $this->forEachOpenMasterConnection( function ( Database $conn ) {
1224                         $conn->setTrxEndCallbackSuppression( true );
1225                 } );
1226         }
1227
1228         /**
1229          * @param IDatabase $conn
1230          */
1231         private function applyTransactionRoundFlags( IDatabase $conn ) {
1232                 if ( $conn->getFlag( $conn::DBO_DEFAULT ) ) {
1233                         // DBO_TRX is controlled entirely by CLI mode presence with DBO_DEFAULT.
1234                         // Force DBO_TRX even in CLI mode since a commit round is expected soon.
1235                         $conn->setFlag( $conn::DBO_TRX, $conn::REMEMBER_PRIOR );
1236                         // If config has explicitly requested DBO_TRX be either on or off by not
1237                         // setting DBO_DEFAULT, then respect that. Forcing no transactions is useful
1238                         // for things like blob stores (ExternalStore) which want auto-commit mode.
1239                 }
1240         }
1241
1242         /**
1243          * @param IDatabase $conn
1244          */
1245         private function undoTransactionRoundFlags( IDatabase $conn ) {
1246                 if ( $conn->getFlag( $conn::DBO_DEFAULT ) ) {
1247                         $conn->restoreFlags( $conn::RESTORE_PRIOR );
1248                 }
1249         }
1250
1251         public function flushReplicaSnapshots( $fname = __METHOD__ ) {
1252                 $this->forEachOpenReplicaConnection( function ( IDatabase $conn ) {
1253                         $conn->flushSnapshot( __METHOD__ );
1254                 } );
1255         }
1256
1257         public function hasMasterConnection() {
1258                 return $this->isOpen( $this->getWriterIndex() );
1259         }
1260
1261         public function hasMasterChanges() {
1262                 $pending = 0;
1263                 $this->forEachOpenMasterConnection( function ( IDatabase $conn ) use ( &$pending ) {
1264                         $pending |= $conn->writesOrCallbacksPending();
1265                 } );
1266
1267                 return (bool)$pending;
1268         }
1269
1270         public function lastMasterChangeTimestamp() {
1271                 $lastTime = false;
1272                 $this->forEachOpenMasterConnection( function ( IDatabase $conn ) use ( &$lastTime ) {
1273                         $lastTime = max( $lastTime, $conn->lastDoneWrites() );
1274                 } );
1275
1276                 return $lastTime;
1277         }
1278
1279         public function hasOrMadeRecentMasterChanges( $age = null ) {
1280                 $age = ( $age === null ) ? $this->mWaitTimeout : $age;
1281
1282                 return ( $this->hasMasterChanges()
1283                         || $this->lastMasterChangeTimestamp() > microtime( true ) - $age );
1284         }
1285
1286         public function pendingMasterChangeCallers() {
1287                 $fnames = [];
1288                 $this->forEachOpenMasterConnection( function ( IDatabase $conn ) use ( &$fnames ) {
1289                         $fnames = array_merge( $fnames, $conn->pendingWriteCallers() );
1290                 } );
1291
1292                 return $fnames;
1293         }
1294
1295         public function getLaggedReplicaMode( $domain = false ) {
1296                 // No-op if there is only one DB (also avoids recursion)
1297                 if ( !$this->laggedReplicaMode && $this->getServerCount() > 1 ) {
1298                         try {
1299                                 // See if laggedReplicaMode gets set
1300                                 $conn = $this->getConnection( self::DB_REPLICA, false, $domain );
1301                                 $this->reuseConnection( $conn );
1302                         } catch ( DBConnectionError $e ) {
1303                                 // Avoid expensive re-connect attempts and failures
1304                                 $this->allReplicasDownMode = true;
1305                                 $this->laggedReplicaMode = true;
1306                         }
1307                 }
1308
1309                 return $this->laggedReplicaMode;
1310         }
1311
1312         /**
1313          * @param bool $domain
1314          * @return bool
1315          * @deprecated 1.28; use getLaggedReplicaMode()
1316          */
1317         public function getLaggedSlaveMode( $domain = false ) {
1318                 return $this->getLaggedReplicaMode( $domain );
1319         }
1320
1321         public function laggedReplicaUsed() {
1322                 return $this->laggedReplicaMode;
1323         }
1324
1325         /**
1326          * @return bool
1327          * @since 1.27
1328          * @deprecated Since 1.28; use laggedReplicaUsed()
1329          */
1330         public function laggedSlaveUsed() {
1331                 return $this->laggedReplicaUsed();
1332         }
1333
1334         public function getReadOnlyReason( $domain = false, IDatabase $conn = null ) {
1335                 if ( $this->readOnlyReason !== false ) {
1336                         return $this->readOnlyReason;
1337                 } elseif ( $this->getLaggedReplicaMode( $domain ) ) {
1338                         if ( $this->allReplicasDownMode ) {
1339                                 return 'The database has been automatically locked ' .
1340                                         'until the replica database servers become available';
1341                         } else {
1342                                 return 'The database has been automatically locked ' .
1343                                         'while the replica database servers catch up to the master.';
1344                         }
1345                 } elseif ( $this->masterRunningReadOnly( $domain, $conn ) ) {
1346                         return 'The database master is running in read-only mode.';
1347                 }
1348
1349                 return false;
1350         }
1351
1352         /**
1353          * @param string $domain Domain ID, or false for the current domain
1354          * @param IDatabase|null DB master connectionl used to avoid loops [optional]
1355          * @return bool
1356          */
1357         private function masterRunningReadOnly( $domain, IDatabase $conn = null ) {
1358                 $cache = $this->wanCache;
1359                 $masterServer = $this->getServerName( $this->getWriterIndex() );
1360
1361                 return (bool)$cache->getWithSetCallback(
1362                         $cache->makeGlobalKey( __CLASS__, 'server-read-only', $masterServer ),
1363                         self::TTL_CACHE_READONLY,
1364                         function () use ( $domain, $conn ) {
1365                                 $old = $this->trxProfiler->setSilenced( true );
1366                                 try {
1367                                         $dbw = $conn ?: $this->getConnection( self::DB_MASTER, [], $domain );
1368                                         $readOnly = (int)$dbw->serverIsReadOnly();
1369                                         if ( !$conn ) {
1370                                                 $this->reuseConnection( $dbw );
1371                                         }
1372                                 } catch ( DBError $e ) {
1373                                         $readOnly = 0;
1374                                 }
1375                                 $this->trxProfiler->setSilenced( $old );
1376                                 return $readOnly;
1377                         },
1378                         [ 'pcTTL' => $cache::TTL_PROC_LONG, 'busyValue' => 0 ]
1379                 );
1380         }
1381
1382         public function allowLagged( $mode = null ) {
1383                 if ( $mode === null ) {
1384                         return $this->mAllowLagged;
1385                 }
1386                 $this->mAllowLagged = $mode;
1387
1388                 return $this->mAllowLagged;
1389         }
1390
1391         public function pingAll() {
1392                 $success = true;
1393                 $this->forEachOpenConnection( function ( IDatabase $conn ) use ( &$success ) {
1394                         if ( !$conn->ping() ) {
1395                                 $success = false;
1396                         }
1397                 } );
1398
1399                 return $success;
1400         }
1401
1402         public function forEachOpenConnection( $callback, array $params = [] ) {
1403                 foreach ( $this->mConns as $connsByServer ) {
1404                         foreach ( $connsByServer as $serverConns ) {
1405                                 foreach ( $serverConns as $conn ) {
1406                                         $mergedParams = array_merge( [ $conn ], $params );
1407                                         call_user_func_array( $callback, $mergedParams );
1408                                 }
1409                         }
1410                 }
1411         }
1412
1413         public function forEachOpenMasterConnection( $callback, array $params = [] ) {
1414                 $masterIndex = $this->getWriterIndex();
1415                 foreach ( $this->mConns as $connsByServer ) {
1416                         if ( isset( $connsByServer[$masterIndex] ) ) {
1417                                 /** @var IDatabase $conn */
1418                                 foreach ( $connsByServer[$masterIndex] as $conn ) {
1419                                         $mergedParams = array_merge( [ $conn ], $params );
1420                                         call_user_func_array( $callback, $mergedParams );
1421                                 }
1422                         }
1423                 }
1424         }
1425
1426         public function forEachOpenReplicaConnection( $callback, array $params = [] ) {
1427                 foreach ( $this->mConns as $connsByServer ) {
1428                         foreach ( $connsByServer as $i => $serverConns ) {
1429                                 if ( $i === $this->getWriterIndex() ) {
1430                                         continue; // skip master
1431                                 }
1432                                 foreach ( $serverConns as $conn ) {
1433                                         $mergedParams = array_merge( [ $conn ], $params );
1434                                         call_user_func_array( $callback, $mergedParams );
1435                                 }
1436                         }
1437                 }
1438         }
1439
1440         public function getMaxLag( $domain = false ) {
1441                 $maxLag = -1;
1442                 $host = '';
1443                 $maxIndex = 0;
1444
1445                 if ( $this->getServerCount() <= 1 ) {
1446                         return [ $host, $maxLag, $maxIndex ]; // no replication = no lag
1447                 }
1448
1449                 $lagTimes = $this->getLagTimes( $domain );
1450                 foreach ( $lagTimes as $i => $lag ) {
1451                         if ( $this->mLoads[$i] > 0 && $lag > $maxLag ) {
1452                                 $maxLag = $lag;
1453                                 $host = $this->mServers[$i]['host'];
1454                                 $maxIndex = $i;
1455                         }
1456                 }
1457
1458                 return [ $host, $maxLag, $maxIndex ];
1459         }
1460
1461         public function getLagTimes( $domain = false ) {
1462                 if ( $this->getServerCount() <= 1 ) {
1463                         return [ $this->getWriterIndex() => 0 ]; // no replication = no lag
1464                 }
1465
1466                 $knownLagTimes = []; // map of (server index => 0 seconds)
1467                 $indexesWithLag = [];
1468                 foreach ( $this->mServers as $i => $server ) {
1469                         if ( empty( $server['is static'] ) ) {
1470                                 $indexesWithLag[] = $i; // DB server might have replication lag
1471                         } else {
1472                                 $knownLagTimes[$i] = 0; // DB server is a non-replicating and read-only archive
1473                         }
1474                 }
1475
1476                 return $this->getLoadMonitor()->getLagTimes( $indexesWithLag, $domain ) + $knownLagTimes;
1477         }
1478
1479         public function safeGetLag( IDatabase $conn ) {
1480                 if ( $this->getServerCount() <= 1 ) {
1481                         return 0;
1482                 } else {
1483                         return $conn->getLag();
1484                 }
1485         }
1486
1487         /**
1488          * @param IDatabase $conn
1489          * @param DBMasterPos|bool $pos
1490          * @param int $timeout
1491          * @return bool
1492          */
1493         public function safeWaitForMasterPos( IDatabase $conn, $pos = false, $timeout = 10 ) {
1494                 if ( $this->getServerCount() <= 1 || !$conn->getLBInfo( 'replica' ) ) {
1495                         return true; // server is not a replica DB
1496                 }
1497
1498                 if ( !$pos ) {
1499                         // Get the current master position, opening a connection if needed
1500                         $masterConn = $this->getAnyOpenConnection( $this->getWriterIndex() );
1501                         if ( $masterConn ) {
1502                                 $pos = $masterConn->getMasterPos();
1503                         } else {
1504                                 $masterConn = $this->openConnection( $this->getWriterIndex(), self::DOMAIN_ANY );
1505                                 $pos = $masterConn->getMasterPos();
1506                                 $this->closeConnection( $masterConn );
1507                         }
1508                 }
1509
1510                 if ( $pos instanceof DBMasterPos ) {
1511                         $result = $conn->masterPosWait( $pos, $timeout );
1512                         if ( $result == -1 || is_null( $result ) ) {
1513                                 $msg = __METHOD__ . ": Timed out waiting on {$conn->getServer()} pos {$pos}";
1514                                 $this->replLogger->warning( "$msg" );
1515                                 $ok = false;
1516                         } else {
1517                                 $this->replLogger->info( __METHOD__ . ": Done" );
1518                                 $ok = true;
1519                         }
1520                 } else {
1521                         $ok = false; // something is misconfigured
1522                         $this->replLogger->error( "Could not get master pos for {$conn->getServer()}." );
1523                 }
1524
1525                 return $ok;
1526         }
1527
1528         public function setTransactionListener( $name, callable $callback = null ) {
1529                 if ( $callback ) {
1530                         $this->trxRecurringCallbacks[$name] = $callback;
1531                 } else {
1532                         unset( $this->trxRecurringCallbacks[$name] );
1533                 }
1534                 $this->forEachOpenMasterConnection(
1535                         function ( IDatabase $conn ) use ( $name, $callback ) {
1536                                 $conn->setTransactionListener( $name, $callback );
1537                         }
1538                 );
1539         }
1540
1541         public function setTableAliases( array $aliases ) {
1542                 $this->tableAliases = $aliases;
1543         }
1544
1545         public function setDomainPrefix( $prefix ) {
1546                 if ( $this->mConns['foreignUsed'] ) {
1547                         // Do not switch connections to explicit foreign domains unless marked as free
1548                         $domains = [];
1549                         foreach ( $this->mConns['foreignUsed'] as $i => $connsByDomain ) {
1550                                 $domains = array_merge( $domains, array_keys( $connsByDomain ) );
1551                         }
1552                         $domains = implode( ', ', $domains );
1553                         throw new DBUnexpectedError( null,
1554                                 "Foreign domain connections are still in use ($domains)." );
1555                 }
1556
1557                 $this->localDomain = new DatabaseDomain(
1558                         $this->localDomain->getDatabase(),
1559                         null,
1560                         $prefix
1561                 );
1562
1563                 $this->forEachOpenConnection( function ( IDatabase $db ) use ( $prefix ) {
1564                         $db->tablePrefix( $prefix );
1565                 } );
1566         }
1567
1568         /**
1569          * Make PHP ignore user aborts/disconnects until the returned
1570          * value leaves scope. This returns null and does nothing in CLI mode.
1571          *
1572          * @return ScopedCallback|null
1573          */
1574         final protected function getScopedPHPBehaviorForCommit() {
1575                 if ( PHP_SAPI != 'cli' ) { // https://bugs.php.net/bug.php?id=47540
1576                         $old = ignore_user_abort( true ); // avoid half-finished operations
1577                         return new ScopedCallback( function () use ( $old ) {
1578                                 ignore_user_abort( $old );
1579                         } );
1580                 }
1581
1582                 return null;
1583         }
1584
1585         function __destruct() {
1586                 // Avoid connection leaks for sanity
1587                 $this->disable();
1588         }
1589 }