includes/libs/rdbms/loadbalancer/LoadBalancer.php

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