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 namespace Wikimedia\Rdbms;
  24
  25 use Psr\Log\LoggerInterface;
  26 use Psr\Log\NullLogger;
  27 use Wikimedia\ScopedCallback;
  28 use IDatabase;
  29 use Database;
  30 use DBConnRef;
  31 use MaintainableDBConnRef;
  32 use BagOStuff;
  33 use EmptyBagOStuff;
  34 use WANObjectCache;
  35 use ArrayUtils;
  36 use DBError;
  37 use DBAccessError;
  38 use DBExpectedError;
  39 use DBUnexpectedError;
  40 use DBTransactionError;
  41 use DBTransactionSizeError;
  42 use DBConnectionError;
  43 use InvalidArgumentException;
  44 use RuntimeException;
  45 use Exception;
  46
  47 /**
  48  * Database connection, tracking, load balancing, and transaction manager for a cluster
  49  *
  50  * @ingroup Database
  51  */
  52 class LoadBalancer implements ILoadBalancer {
  53         /** @var array[] Map of (server index => server config array) */
  54         private $mServers;
  55         /** @var \Database[][][] Map of local/foreignUsed/foreignFree => server index => IDatabase array */
  56         private $mConns;
  57         /** @var float[] Map of (server index => weight) */
  58         private $mLoads;
  59         /** @var array[] Map of (group => server index => weight) */
  60         private $mGroupLoads;
  61         /** @var bool Whether to disregard replica DB lag as a factor in replica DB selection */
  62         private $mAllowLagged;
  63         /** @var integer Seconds to spend waiting on replica DB lag to resolve */
  64         private $mWaitTimeout;
  65         /** @var array The LoadMonitor configuration */
  66         private $loadMonitorConfig;
  67         /** @var array[] $aliases Map of (table => (dbname, schema, prefix) map) */
  68         private $tableAliases = [];
  69
  70         /** @var ILoadMonitor */
  71         private $loadMonitor;
  72         /** @var BagOStuff */
  73         private $srvCache;
  74         /** @var BagOStuff */
  75         private $memCache;
  76         /** @var WANObjectCache */
  77         private $wanCache;
  78         /** @var object|string Class name or object With profileIn/profileOut methods */
  79         protected $profiler;
  80         /** @var TransactionProfiler */
  81         protected $trxProfiler;
  82         /** @var LoggerInterface */
  83         protected $replLogger;
  84         /** @var LoggerInterface */
  85         protected $connLogger;
  86         /** @var LoggerInterface */
  87         protected $queryLogger;
  88         /** @var LoggerInterface */
  89         protected $perfLogger;
  90
  91         /** @var \Database Database connection that caused a problem */
  92         private $errorConnection;
  93         /** @var integer The generic (not query grouped) replica DB index (of $mServers) */
  94         private $mReadIndex;
  95         /** @var bool|DBMasterPos False if not set */
  96         private $mWaitForPos;
  97         /** @var bool Whether the generic reader fell back to a lagged replica DB */
  98         private $laggedReplicaMode = false;
  99         /** @var bool Whether the generic reader fell back to a lagged replica DB */
 100         private $allReplicasDownMode = false;
 101         /** @var string The last DB selection or connection error */
 102         private $mLastError = 'Unknown error';
 103         /** @var string|bool Reason the LB is read-only or false if not */
 104         private $readOnlyReason = false;
 105         /** @var integer Total connections opened */
 106         private $connsOpened = 0;
 107         /** @var string|bool String if a requested DBO_TRX transaction round is active */
 108         private $trxRoundId = false;
 109         /** @var array[] Map of (name => callable) */
 110         private $trxRecurringCallbacks = [];
 111         /** @var DatabaseDomain Local Domain ID and default for selectDB() calls */
 112         private $localDomain;
 113         /** @var string Alternate ID string for the domain instead of DatabaseDomain::getId() */
 114         private $localDomainIdAlias;
 115         /** @var string Current server name */
 116         private $host;
 117         /** @var bool Whether this PHP instance is for a CLI script */
 118         protected $cliMode;
 119         /** @var string Agent name for query profiling */
 120         protected $agent;
 121
 122         /** @var callable Exception logger */
 123         private $errorLogger;
 124
 125         /** @var boolean */
 126         private $disabled = false;
 127
 128         /** @var integer Warn when this many connection are held */
 129         const CONN_HELD_WARN_THRESHOLD = 10;
 130
 131         /** @var integer Default 'max lag' when unspecified */
 132         const MAX_LAG_DEFAULT = 10;
 133         /** @var integer Seconds to cache master server read-only status */
 134         const TTL_CACHE_READONLY = 5;
 135
 136         public function __construct( array $params ) {
 137                 if ( !isset( $params['servers'] ) ) {
 138                         throw new InvalidArgumentException( __CLASS__ . ': missing servers parameter' );
 139                 }
 140                 $this->mServers = $params['servers'];
 141
 142                 $this->localDomain = isset( $params['localDomain'] )
 143                         ? DatabaseDomain::newFromId( $params['localDomain'] )
 144                         : DatabaseDomain::newUnspecified();
 145                 // In case a caller assumes that the domain ID is simply <db>-<prefix>, which is almost
 146                 // always true, gracefully handle the case when they fail to account for escaping.
 147                 if ( $this->localDomain->getTablePrefix() != '' ) {
 148                         $this->localDomainIdAlias =
 149                                 $this->localDomain->getDatabase() . '-' . $this->localDomain->getTablePrefix();
 150                 } else {
 151                         $this->localDomainIdAlias = $this->localDomain->getDatabase();
 152                 }
 153
 154                 $this->mWaitTimeout = isset( $params['waitTimeout'] ) ? $params['waitTimeout'] : 10;
 155
 156                 $this->mReadIndex = -1;
 157                 $this->mConns = [
 158                         'local'       => [],
 159                         'foreignUsed' => [],
 160                         'foreignFree' => []
 161                 ];
 162                 $this->mLoads = [];
 163                 $this->mWaitForPos = false;
 164                 $this->mAllowLagged = false;
 165
 166                 if ( isset( $params['readOnlyReason'] ) && is_string( $params['readOnlyReason'] ) ) {
 167                         $this->readOnlyReason = $params['readOnlyReason'];
 168                 }
 169
 170                 if ( isset( $params['loadMonitor'] ) ) {
 171                         $this->loadMonitorConfig = $params['loadMonitor'];
 172                 } else {
 173                         $this->loadMonitorConfig = [ 'class' => 'LoadMonitorNull' ];
 174                 }
 175
 176                 foreach ( $params['servers'] as $i => $server ) {
 177                         $this->mLoads[$i] = $server['load'];
 178                         if ( isset( $server['groupLoads'] ) ) {
 179                                 foreach ( $server['groupLoads'] as $group => $ratio ) {
 180                                         if ( !isset( $this->mGroupLoads[$group] ) ) {
 181                                                 $this->mGroupLoads[$group] = [];
 182                                         }
 183                                         $this->mGroupLoads[$group][$i] = $ratio;
 184                                 }
 185                         }
 186                 }
 187
 188                 if ( isset( $params['srvCache'] ) ) {
 189                         $this->srvCache = $params['srvCache'];
 190                 } else {
 191                         $this->srvCache = new EmptyBagOStuff();
 192                 }
 193                 if ( isset( $params['memCache'] ) ) {
 194                         $this->memCache = $params['memCache'];
 195                 } else {
 196                         $this->memCache = new EmptyBagOStuff();
 197                 }
 198                 if ( isset( $params['wanCache'] ) ) {
 199                         $this->wanCache = $params['wanCache'];
 200                 } else {
 201                         $this->wanCache = WANObjectCache::newEmpty();
 202                 }
 203                 $this->profiler = isset( $params['profiler'] ) ? $params['profiler'] : null;
 204                 if ( isset( $params['trxProfiler'] ) ) {
 205                         $this->trxProfiler = $params['trxProfiler'];
 206                 } else {
 207                         $this->trxProfiler = new TransactionProfiler();
 208                 }
 209
 210                 $this->errorLogger = isset( $params['errorLogger'] )
 211                         ? $params['errorLogger']
 212                         : function ( Exception $e ) {
 213                                 trigger_error( get_class( $e ) . ': ' . $e->getMessage(), E_USER_WARNING );
 214                         };
 215
 216                 foreach ( [ 'replLogger', 'connLogger', 'queryLogger', 'perfLogger' ] as $key ) {
 217                         $this->$key = isset( $params[$key] ) ? $params[$key] : new NullLogger();
 218                 }
 219
 220                 $this->host = isset( $params['hostname'] )
 221                         ? $params['hostname']
 222                         : ( gethostname() ?: 'unknown' );
 223                 $this->cliMode = isset( $params['cliMode'] ) ? $params['cliMode'] : PHP_SAPI === 'cli';
 224                 $this->agent = isset( $params['agent'] ) ? $params['agent'] : '';
 225         }
 226
 227         /**
 228          * Get a LoadMonitor instance
 229          *
 230          * @return ILoadMonitor
 231          */
 232         private function getLoadMonitor() {
 233                 if ( !isset( $this->loadMonitor ) ) {
 234                         $compat = [
 235                                 'LoadMonitor' => LoadMonitor::class,
 236                                 'LoadMonitorNull' => LoadMonitorNull::class,
 237                                 'LoadMonitorMySQL' => LoadMonitorMySQL::class,
 238                         ];
 239
 240                         $class = $this->loadMonitorConfig['class'];
 241                         if ( isset( $compat[$class] ) ) {
 242                                 $class = $compat[$class];
 243                         }
 244
 245                         $this->loadMonitor = new $class(
 246                                 $this, $this->srvCache, $this->memCache, $this->loadMonitorConfig );
 247                         $this->loadMonitor->setLogger( $this->replLogger );
 248                 }
 249
 250                 return $this->loadMonitor;
 251         }
 252
 253         /**
 254          * @param array $loads
 255          * @param bool|string $domain Domain to get non-lagged for
 256          * @param int $maxLag Restrict the maximum allowed lag to this many seconds
 257          * @return bool|int|string
 258          */
 259         private function getRandomNonLagged( array $loads, $domain = false, $maxLag = INF ) {
 260                 $lags = $this->getLagTimes( $domain );
 261
 262                 # Unset excessively lagged servers
 263                 foreach ( $lags as $i => $lag ) {
 264                         if ( $i != 0 ) {
 265                                 # How much lag this server nominally is allowed to have
 266                                 $maxServerLag = isset( $this->mServers[$i]['max lag'] )
 267                                         ? $this->mServers[$i]['max lag']
 268                                         : self::MAX_LAG_DEFAULT; // default
 269                                 # Constrain that futher by $maxLag argument
 270                                 $maxServerLag = min( $maxServerLag, $maxLag );
 271
 272                                 $host = $this->getServerName( $i );
 273                                 if ( $lag === false && !is_infinite( $maxServerLag ) ) {
 274                                         $this->replLogger->error(
 275                                                 "Server {host} (#$i) is not replicating?", [ 'host' => $host ] );
 276                                         unset( $loads[$i] );
 277                                 } elseif ( $lag > $maxServerLag ) {
 278                                         $this->replLogger->warning(
 279                                                 "Server {host} (#$i) has {lag} seconds of lag (>= {maxlag})",
 280                                                 [ 'host' => $host, 'lag' => $lag, 'maxlag' => $maxServerLag ]
 281                                         );
 282                                         unset( $loads[$i] );
 283                                 }
 284                         }
 285                 }
 286
 287                 # Find out if all the replica DBs with non-zero load are lagged
 288                 $sum = 0;
 289                 foreach ( $loads as $load ) {
 290                         $sum += $load;
 291                 }
 292                 if ( $sum == 0 ) {
 293                         # No appropriate DB servers except maybe the master and some replica DBs with zero load
 294                         # Do NOT use the master
 295                         # Instead, this function will return false, triggering read-only mode,
 296                         # and a lagged replica DB will be used instead.
 297                         return false;
 298                 }
 299
 300                 if ( count( $loads ) == 0 ) {
 301                         return false;
 302                 }
 303
 304                 # Return a random representative of the remainder
 305                 return ArrayUtils::pickRandom( $loads );
 306         }
 307
 308         public function getReaderIndex( $group = false, $domain = false ) {
 309                 if ( count( $this->mServers ) == 1 ) {
 310                         # Skip the load balancing if there's only one server
 311                         return $this->getWriterIndex();
 312                 } elseif ( $group === false && $this->mReadIndex >= 0 ) {
 313                         # Shortcut if generic reader exists already
 314                         return $this->mReadIndex;
 315                 }
 316
 317                 # Find the relevant load array
 318                 if ( $group !== false ) {
 319                         if ( isset( $this->mGroupLoads[$group] ) ) {
 320                                 $nonErrorLoads = $this->mGroupLoads[$group];
 321                         } else {
 322                                 # No loads for this group, return false and the caller can use some other group
 323                                 $this->connLogger->info( __METHOD__ . ": no loads for group $group" );
 324
 325                                 return false;
 326                         }
 327                 } else {
 328                         $nonErrorLoads = $this->mLoads;
 329                 }
 330
 331                 if ( !count( $nonErrorLoads ) ) {
 332                         throw new InvalidArgumentException( "Empty server array given to LoadBalancer" );
 333                 }
 334
 335                 # Scale the configured load ratios according to the dynamic load if supported
 336                 $this->getLoadMonitor()->scaleLoads( $nonErrorLoads, $domain );
 337
 338                 $laggedReplicaMode = false;
 339
 340                 # No server found yet
 341                 $i = false;
 342                 # First try quickly looking through the available servers for a server that
 343                 # meets our criteria
 344                 $currentLoads = $nonErrorLoads;
 345                 while ( count( $currentLoads ) ) {
 346                         if ( $this->mAllowLagged || $laggedReplicaMode ) {
 347                                 $i = ArrayUtils::pickRandom( $currentLoads );
 348                         } else {
 349                                 $i = false;
 350                                 if ( $this->mWaitForPos && $this->mWaitForPos->asOfTime() ) {
 351                                         # ChronologyProtecter causes mWaitForPos to be set via sessions.
 352                                         # This triggers doWait() after connect, so it's especially good to
 353                                         # avoid lagged servers so as to avoid just blocking in that method.
 354                                         $ago = microtime( true ) - $this->mWaitForPos->asOfTime();
 355                                         # Aim for <= 1 second of waiting (being too picky can backfire)
 356                                         $i = $this->getRandomNonLagged( $currentLoads, $domain, $ago + 1 );
 357                                 }
 358                                 if ( $i === false ) {
 359                                         # Any server with less lag than it's 'max lag' param is preferable
 360                                         $i = $this->getRandomNonLagged( $currentLoads, $domain );
 361                                 }
 362                                 if ( $i === false && count( $currentLoads ) != 0 ) {
 363                                         # All replica DBs lagged. Switch to read-only mode
 364                                         $this->replLogger->error( "All replica DBs lagged. Switch to read-only mode" );
 365                                         $i = ArrayUtils::pickRandom( $currentLoads );
 366                                         $laggedReplicaMode = true;
 367                                 }
 368                         }
 369
 370                         if ( $i === false ) {
 371                                 # pickRandom() returned false
 372                                 # This is permanent and means the configuration or the load monitor
 373                                 # wants us to return false.
 374                                 $this->connLogger->debug( __METHOD__ . ": pickRandom() returned false" );
 375
 376                                 return false;
 377                         }
 378
 379                         $serverName = $this->getServerName( $i );
 380                         $this->connLogger->debug( __METHOD__ . ": Using reader #$i: $serverName..." );
 381
 382                         $conn = $this->openConnection( $i, $domain );
 383                         if ( !$conn ) {
 384                                 $this->connLogger->warning( __METHOD__ . ": Failed connecting to $i/$domain" );
 385                                 unset( $nonErrorLoads[$i] );
 386                                 unset( $currentLoads[$i] );
 387                                 $i = false;
 388                                 continue;
 389                         }
 390
 391                         // Decrement reference counter, we are finished with this connection.
 392                         // It will be incremented for the caller later.
 393                         if ( $domain !== false ) {
 394                                 $this->reuseConnection( $conn );
 395                         }
 396
 397                         # Return this server
 398                         break;
 399                 }
 400
 401                 # If all servers were down, quit now
 402                 if ( !count( $nonErrorLoads ) ) {
 403                         $this->connLogger->error( "All servers down" );
 404                 }
 405
 406                 if ( $i !== false ) {
 407                         # Replica DB connection successful.
 408                         # Wait for the session master pos for a short time.
 409                         if ( $this->mWaitForPos && $i > 0 ) {
 410                                 $this->doWait( $i );
 411                         }
 412                         if ( $this->mReadIndex <= 0 && $this->mLoads[$i] > 0 && $group === false ) {
 413                                 $this->mReadIndex = $i;
 414                                 # Record if the generic reader index is in "lagged replica DB" mode
 415                                 if ( $laggedReplicaMode ) {
 416                                         $this->laggedReplicaMode = true;
 417                                 }
 418                         }
 419                         $serverName = $this->getServerName( $i );
 420                         $this->connLogger->debug(
 421                                 __METHOD__ . ": using server $serverName for group '$group'" );
 422                 }
 423
 424                 return $i;
 425         }
 426
 427         /**
 428          * @param DBMasterPos|false $pos
 429          */
 430         public function waitFor( $pos ) {
 431                 $this->mWaitForPos = $pos;
 432                 $i = $this->mReadIndex;
 433
 434                 if ( $i > 0 ) {
 435                         if ( !$this->doWait( $i ) ) {
 436                                 $this->laggedReplicaMode = true;
 437                         }
 438                 }
 439         }
 440
 441         public function waitForOne( $pos, $timeout = null ) {
 442                 $this->mWaitForPos = $pos;
 443
 444                 $i = $this->mReadIndex;
 445                 if ( $i <= 0 ) {
 446                         // Pick a generic replica DB if there isn't one yet
 447                         $readLoads = $this->mLoads;
 448                         unset( $readLoads[$this->getWriterIndex()] ); // replica DBs only
 449                         $readLoads = array_filter( $readLoads ); // with non-zero load
 450                         $i = ArrayUtils::pickRandom( $readLoads );
 451                 }
 452
 453                 if ( $i > 0 ) {
 454                         $ok = $this->doWait( $i, true, $timeout );
 455                 } else {
 456                         $ok = true; // no applicable loads
 457                 }
 458
 459                 return $ok;
 460         }
 461
 462         public function waitForAll( $pos, $timeout = null ) {
 463                 $this->mWaitForPos = $pos;
 464                 $serverCount = count( $this->mServers );
 465
 466                 $ok = true;
 467                 for ( $i = 1; $i < $serverCount; $i++ ) {
 468                         if ( $this->mLoads[$i] > 0 ) {
 469                                 $ok = $this->doWait( $i, true, $timeout ) && $ok;
 470                         }
 471                 }
 472
 473                 return $ok;
 474         }
 475
 476         /**
 477          * @param int $i
 478          * @return IDatabase|bool
 479          */
 480         public function getAnyOpenConnection( $i ) {
 481                 foreach ( $this->mConns as $connsByServer ) {
 482                         if ( !empty( $connsByServer[$i] ) ) {
 483                                 /** @var $serverConns IDatabase[] */
 484                                 $serverConns = $connsByServer[$i];
 485
 486                                 return reset( $serverConns );
 487                         }
 488                 }
 489
 490                 return false;
 491         }
 492
 493         /**
 494          * Wait for a given replica DB to catch up to the master pos stored in $this
 495          * @param int $index Server index
 496          * @param bool $open Check the server even if a new connection has to be made
 497          * @param int $timeout Max seconds to wait; default is mWaitTimeout
 498          * @return bool
 499          */
 500         protected function doWait( $index, $open = false, $timeout = null ) {
 501                 $close = false; // close the connection afterwards
 502
 503                 // Check if we already know that the DB has reached this point
 504                 $server = $this->getServerName( $index );
 505                 $key = $this->srvCache->makeGlobalKey( __CLASS__, 'last-known-pos', $server, 'v1' );
 506                 /** @var DBMasterPos $knownReachedPos */
 507                 $knownReachedPos = $this->srvCache->get( $key );
 508                 if (
 509                         $knownReachedPos instanceof DBMasterPos &&
 510                         $knownReachedPos->hasReached( $this->mWaitForPos )
 511                 ) {
 512                         $this->replLogger->debug( __METHOD__ .
 513                                 ": replica DB $server known to be caught up (pos >= $knownReachedPos)." );
 514                         return true;
 515                 }
 516
 517                 // Find a connection to wait on, creating one if needed and allowed
 518                 $conn = $this->getAnyOpenConnection( $index );
 519                 if ( !$conn ) {
 520                         if ( !$open ) {
 521                                 $this->replLogger->debug( __METHOD__ . ": no connection open for $server" );
 522
 523                                 return false;
 524                         } else {
 525                                 $conn = $this->openConnection( $index, self::DOMAIN_ANY );
 526                                 if ( !$conn ) {
 527                                         $this->replLogger->warning( __METHOD__ . ": failed to connect to $server" );
 528
 529                                         return false;
 530                                 }
 531                                 // Avoid connection spam in waitForAll() when connections
 532                                 // are made just for the sake of doing this lag check.
 533                                 $close = true;
 534                         }
 535                 }
 536
 537                 $this->replLogger->info( __METHOD__ . ": Waiting for replica DB $server to catch up..." );
 538                 $timeout = $timeout ?: $this->mWaitTimeout;
 539                 $result = $conn->masterPosWait( $this->mWaitForPos, $timeout );
 540
 541                 if ( $result == -1 || is_null( $result ) ) {
 542                         // Timed out waiting for replica DB, use master instead
 543                         $this->replLogger->warning(
 544                                 __METHOD__ . ": Timed out waiting on {host} pos {$this->mWaitForPos}",
 545                                 [ 'host' => $server ]
 546                         );
 547                         $ok = false;
 548                 } else {
 549                         $this->replLogger->info( __METHOD__ . ": Done" );
 550                         $ok = true;
 551                         // Remember that the DB reached this point
 552                         $this->srvCache->set( $key, $this->mWaitForPos, BagOStuff::TTL_DAY );
 553                 }
 554
 555                 if ( $close ) {
 556                         $this->closeConnection( $conn );
 557                 }
 558
 559                 return $ok;
 560         }
 561
 562         /**
 563          * @see ILoadBalancer::getConnection()
 564          *
 565          * @param int $i
 566          * @param array $groups
 567          * @param bool $domain
 568          * @return Database
 569          * @throws DBConnectionError
 570          */
 571         public function getConnection( $i, $groups = [], $domain = false ) {
 572                 if ( $i === null || $i === false ) {
 573                         throw new InvalidArgumentException( 'Attempt to call ' . __METHOD__ .
 574                                 ' with invalid server index' );
 575                 }
 576
 577                 if ( $this->localDomain->equals( $domain ) || $domain === $this->localDomainIdAlias ) {
 578                         $domain = false; // local connection requested
 579                 }
 580
 581                 $groups = ( $groups === false || $groups === [] )
 582                         ? [ false ] // check one "group": the generic pool
 583                         : (array)$groups;
 584
 585                 $masterOnly = ( $i == self::DB_MASTER || $i == $this->getWriterIndex() );
 586                 $oldConnsOpened = $this->connsOpened; // connections open now
 587
 588                 if ( $i == self::DB_MASTER ) {
 589                         $i = $this->getWriterIndex();
 590                 } else {
 591                         # Try to find an available server in any the query groups (in order)
 592                         foreach ( $groups as $group ) {
 593                                 $groupIndex = $this->getReaderIndex( $group, $domain );
 594                                 if ( $groupIndex !== false ) {
 595                                         $i = $groupIndex;
 596                                         break;
 597                                 }
 598                         }
 599                 }
 600
 601                 # Operation-based index
 602                 if ( $i == self::DB_REPLICA ) {
 603                         $this->mLastError = 'Unknown error'; // reset error string
 604                         # Try the general server pool if $groups are unavailable.
 605                         $i = ( $groups === [ false ] )
 606                                 ? false // don't bother with this if that is what was tried above
 607                                 : $this->getReaderIndex( false, $domain );
 608                         # Couldn't find a working server in getReaderIndex()?
 609                         if ( $i === false ) {
 610                                 $this->mLastError = 'No working replica DB server: ' . $this->mLastError;
 611                                 // Throw an exception
 612                                 $this->reportConnectionError();
 613                                 return null; // not reached
 614                         }
 615                 }
 616
 617                 # Now we have an explicit index into the servers array
 618                 $conn = $this->openConnection( $i, $domain );
 619                 if ( !$conn ) {
 620                         // Throw an exception
 621                         $this->reportConnectionError();
 622                         return null; // not reached
 623                 }
 624
 625                 # Profile any new connections that happen
 626                 if ( $this->connsOpened > $oldConnsOpened ) {
 627                         $host = $conn->getServer();
 628                         $dbname = $conn->getDBname();
 629                         $this->trxProfiler->recordConnection( $host, $dbname, $masterOnly );
 630                 }
 631
 632                 if ( $masterOnly ) {
 633                         # Make master-requested DB handles inherit any read-only mode setting
 634                         $conn->setLBInfo( 'readOnlyReason', $this->getReadOnlyReason( $domain, $conn ) );
 635                 }
 636
 637                 return $conn;
 638         }
 639
 640         public function reuseConnection( $conn ) {
 641                 $serverIndex = $conn->getLBInfo( 'serverIndex' );
 642                 $refCount = $conn->getLBInfo( 'foreignPoolRefCount' );
 643                 if ( $serverIndex === null || $refCount === null ) {
 644                         /**
 645                          * This can happen in code like:
 646                          *   foreach ( $dbs as $db ) {
 647                          *     $conn = $lb->getConnection( $lb::DB_REPLICA, [], $db );
 648                          *     ...
 649                          *     $lb->reuseConnection( $conn );
 650                          *   }
 651                          * When a connection to the local DB is opened in this way, reuseConnection()
 652                          * should be ignored
 653                          */
 654                         return;
 655                 } elseif ( $conn instanceof DBConnRef ) {
 656                         // DBConnRef already handles calling reuseConnection() and only passes the live
 657                         // Database instance to this method. Any caller passing in a DBConnRef is broken.
 658                         $this->connLogger->error( __METHOD__ . ": got DBConnRef instance.\n" .
 659                                 ( new RuntimeException() )->getTraceAsString() );
 660
 661                         return;
 662                 }
 663
 664                 if ( $this->disabled ) {
 665                         return; // DBConnRef handle probably survived longer than the LoadBalancer
 666                 }
 667
 668                 $domain = $conn->getDomainID();
 669                 if ( !isset( $this->mConns['foreignUsed'][$serverIndex][$domain] ) ) {
 670                         throw new InvalidArgumentException( __METHOD__ .
 671                                 ": connection $serverIndex/$domain not found; it may have already been freed." );
 672                 } elseif ( $this->mConns['foreignUsed'][$serverIndex][$domain] !== $conn ) {
 673                         throw new InvalidArgumentException( __METHOD__ .
 674                                 ": connection $serverIndex/$domain mismatched; it may have already been freed." );
 675                 }
 676                 $conn->setLBInfo( 'foreignPoolRefCount', --$refCount );
 677                 if ( $refCount <= 0 ) {
 678                         $this->mConns['foreignFree'][$serverIndex][$domain] = $conn;
 679                         unset( $this->mConns['foreignUsed'][$serverIndex][$domain] );
 680                         if ( !$this->mConns['foreignUsed'][$serverIndex] ) {
 681                                 unset( $this->mConns[ 'foreignUsed' ][$serverIndex] ); // clean up
 682                         }
 683                         $this->connLogger->debug( __METHOD__ . ": freed connection $serverIndex/$domain" );
 684                 } else {
 685                         $this->connLogger->debug( __METHOD__ .
 686                                 ": reference count for $serverIndex/$domain reduced to $refCount" );
 687                 }
 688         }
 689
 690         public function getConnectionRef( $db, $groups = [], $domain = false ) {
 691                 $domain = ( $domain !== false ) ? $domain : $this->localDomain;
 692
 693                 return new DBConnRef( $this, $this->getConnection( $db, $groups, $domain ) );
 694         }
 695
 696         public function getLazyConnectionRef( $db, $groups = [], $domain = false ) {
 697                 $domain = ( $domain !== false ) ? $domain : $this->localDomain;
 698
 699                 return new DBConnRef( $this, [ $db, $groups, $domain ] );
 700         }
 701
 702         public function getMaintenanceConnectionRef( $db, $groups = [], $domain = false ) {
 703                 $domain = ( $domain !== false ) ? $domain : $this->localDomain;
 704
 705                 return new MaintainableDBConnRef( $this, $this->getConnection( $db, $groups, $domain ) );
 706         }
 707
 708         /**
 709          * @see ILoadBalancer::openConnection()
 710          *
 711          * @param int $i
 712          * @param bool $domain
 713          * @return bool|Database
 714          * @throws DBAccessError
 715          */
 716         public function openConnection( $i, $domain = false ) {
 717                 if ( $this->localDomain->equals( $domain ) || $domain === $this->localDomainIdAlias ) {
 718                         $domain = false; // local connection requested
 719                 }
 720
 721                 if ( $domain !== false ) {
 722                         $conn = $this->openForeignConnection( $i, $domain );
 723                 } elseif ( isset( $this->mConns['local'][$i][0] ) ) {
 724                         $conn = $this->mConns['local'][$i][0];
 725                 } else {
 726                         if ( !isset( $this->mServers[$i] ) || !is_array( $this->mServers[$i] ) ) {
 727                                 throw new InvalidArgumentException( "No server with index '$i'." );
 728                         }
 729                         // Open a new connection
 730                         $server = $this->mServers[$i];
 731                         $server['serverIndex'] = $i;
 732                         $conn = $this->reallyOpenConnection( $server, false );
 733                         $serverName = $this->getServerName( $i );
 734                         if ( $conn->isOpen() ) {
 735                                 $this->connLogger->debug( "Connected to database $i at '$serverName'." );
 736                                 $this->mConns['local'][$i][0] = $conn;
 737                         } else {
 738                                 $this->connLogger->warning( "Failed to connect to database $i at '$serverName'." );
 739                                 $this->errorConnection = $conn;
 740                                 $conn = false;
 741                         }
 742                 }
 743
 744                 if ( $conn instanceof IDatabase && !$conn->isOpen() ) {
 745                         // Connection was made but later unrecoverably lost for some reason.
 746                         // Do not return a handle that will just throw exceptions on use,
 747                         // but let the calling code (e.g. getReaderIndex) try another server.
 748                         // See DatabaseMyslBase::ping() for how this can happen.
 749                         $this->errorConnection = $conn;
 750                         $conn = false;
 751                 }
 752
 753                 return $conn;
 754         }
 755
 756         /**
 757          * Open a connection to a foreign DB, or return one if it is already open.
 758          *
 759          * Increments a reference count on the returned connection which locks the
 760          * connection to the requested domain. This reference count can be
 761          * decremented by calling reuseConnection().
 762          *
 763          * If a connection is open to the appropriate server already, but with the wrong
 764          * database, it will be switched to the right database and returned, as long as
 765          * it has been freed first with reuseConnection().
 766          *
 767          * On error, returns false, and the connection which caused the
 768          * error will be available via $this->errorConnection.
 769          *
 770          * @note If disable() was called on this LoadBalancer, this method will throw a DBAccessError.
 771          *
 772          * @param int $i Server index
 773          * @param string $domain Domain ID to open
 774          * @return Database
 775          */
 776         private function openForeignConnection( $i, $domain ) {
 777                 $domainInstance = DatabaseDomain::newFromId( $domain );
 778                 $dbName = $domainInstance->getDatabase();
 779                 $prefix = $domainInstance->getTablePrefix();
 780
 781                 if ( isset( $this->mConns['foreignUsed'][$i][$domain] ) ) {
 782                         // Reuse an already-used connection
 783                         $conn = $this->mConns['foreignUsed'][$i][$domain];
 784                         $this->connLogger->debug( __METHOD__ . ": reusing connection $i/$domain" );
 785                 } elseif ( isset( $this->mConns['foreignFree'][$i][$domain] ) ) {
 786                         // Reuse a free connection for the same domain
 787                         $conn = $this->mConns['foreignFree'][$i][$domain];
 788                         unset( $this->mConns['foreignFree'][$i][$domain] );
 789                         $this->mConns['foreignUsed'][$i][$domain] = $conn;
 790                         $this->connLogger->debug( __METHOD__ . ": reusing free connection $i/$domain" );
 791                 } elseif ( !empty( $this->mConns['foreignFree'][$i] ) ) {
 792                         // Reuse a connection from another domain
 793                         $conn = reset( $this->mConns['foreignFree'][$i] );
 794                         $oldDomain = key( $this->mConns['foreignFree'][$i] );
 795                         // The empty string as a DB name means "don't care".
 796                         // DatabaseMysqlBase::open() already handle this on connection.
 797                         if ( strlen( $dbName ) && !$conn->selectDB( $dbName ) ) {
 798                                 $this->mLastError = "Error selecting database '$dbName' on server " .
 799                                         $conn->getServer() . " from client host {$this->host}";
 800                                 $this->errorConnection = $conn;
 801                                 $conn = false;
 802                         } else {
 803                                 $conn->tablePrefix( $prefix );
 804                                 unset( $this->mConns['foreignFree'][$i][$oldDomain] );
 805                                 $this->mConns['foreignUsed'][$i][$domain] = $conn;
 806                                 $this->connLogger->debug( __METHOD__ .
 807                                         ": reusing free connection from $oldDomain for $domain" );
 808                         }
 809                 } else {
 810                         if ( !isset( $this->mServers[$i] ) || !is_array( $this->mServers[$i] ) ) {
 811                                 throw new InvalidArgumentException( "No server with index '$i'." );
 812                         }
 813                         // Open a new connection
 814                         $server = $this->mServers[$i];
 815                         $server['serverIndex'] = $i;
 816                         $server['foreignPoolRefCount'] = 0;
 817                         $server['foreign'] = true;
 818                         $conn = $this->reallyOpenConnection( $server, $dbName );
 819                         if ( !$conn->isOpen() ) {
 820                                 $this->connLogger->warning( __METHOD__ . ": connection error for $i/$domain" );
 821                                 $this->errorConnection = $conn;
 822                                 $conn = false;
 823                         } else {
 824                                 $conn->tablePrefix( $prefix );
 825                                 $this->mConns['foreignUsed'][$i][$domain] = $conn;
 826                                 $this->connLogger->debug( __METHOD__ . ": opened new connection for $i/$domain" );
 827                         }
 828                 }
 829
 830                 // Increment reference count
 831                 if ( $conn instanceof IDatabase ) {
 832                         $refCount = $conn->getLBInfo( 'foreignPoolRefCount' );
 833                         $conn->setLBInfo( 'foreignPoolRefCount', $refCount + 1 );
 834                 }
 835
 836                 return $conn;
 837         }
 838
 839         /**
 840          * Test if the specified index represents an open connection
 841          *
 842          * @param int $index Server index
 843          * @access private
 844          * @return bool
 845          */
 846         private function isOpen( $index ) {
 847                 if ( !is_integer( $index ) ) {
 848                         return false;
 849                 }
 850
 851                 return (bool)$this->getAnyOpenConnection( $index );
 852         }
 853
 854         /**
 855          * Really opens a connection. Uncached.
 856          * Returns a Database object whether or not the connection was successful.
 857          * @access private
 858          *
 859          * @param array $server
 860          * @param string|bool $dbNameOverride Use "" to not select any database
 861          * @return Database
 862          * @throws DBAccessError
 863          * @throws InvalidArgumentException
 864          */
 865         protected function reallyOpenConnection( array $server, $dbNameOverride = false ) {
 866                 if ( $this->disabled ) {
 867                         throw new DBAccessError();
 868                 }
 869
 870                 if ( $dbNameOverride !== false ) {
 871                         $server['dbname'] = $dbNameOverride;
 872                 }
 873
 874                 // Let the handle know what the cluster master is (e.g. "db1052")
 875                 $masterName = $this->getServerName( $this->getWriterIndex() );
 876                 $server['clusterMasterHost'] = $masterName;
 877
 878                 // Log when many connection are made on requests
 879                 if ( ++$this->connsOpened >= self::CONN_HELD_WARN_THRESHOLD ) {
 880                         $this->perfLogger->warning( __METHOD__ . ": " .
 881                                 "{$this->connsOpened}+ connections made (master=$masterName)" );
 882                 }
 883
 884                 $server['srvCache'] = $this->srvCache;
 885                 // Set loggers and profilers
 886                 $server['connLogger'] = $this->connLogger;
 887                 $server['queryLogger'] = $this->queryLogger;
 888                 $server['errorLogger'] = $this->errorLogger;
 889                 $server['profiler'] = $this->profiler;
 890                 $server['trxProfiler'] = $this->trxProfiler;
 891                 // Use the same agent and PHP mode for all DB handles
 892                 $server['cliMode'] = $this->cliMode;
 893                 $server['agent'] = $this->agent;
 894                 // Use DBO_DEFAULT flags by default for LoadBalancer managed databases. Assume that the
 895                 // application calls LoadBalancer::commitMasterChanges() before the PHP script completes.
 896                 $server['flags'] = isset( $server['flags'] ) ? $server['flags'] : IDatabase::DBO_DEFAULT;
 897
 898                 // Create a live connection object
 899                 try {
 900                         $db = Database::factory( $server['type'], $server );
 901                 } catch ( DBConnectionError $e ) {
 902                         // FIXME: This is probably the ugliest thing I have ever done to
 903                         // PHP. I'm half-expecting it to segfault, just out of disgust. -- TS
 904                         $db = $e->db;
 905                 }
 906
 907                 $db->setLBInfo( $server );
 908                 $db->setLazyMasterHandle(
 909                         $this->getLazyConnectionRef( self::DB_MASTER, [], $db->getDomainID() )
 910                 );
 911                 $db->setTableAliases( $this->tableAliases );
 912
 913                 if ( $server['serverIndex'] === $this->getWriterIndex() ) {
 914                         if ( $this->trxRoundId !== false ) {
 915                                 $this->applyTransactionRoundFlags( $db );
 916                         }
 917                         foreach ( $this->trxRecurringCallbacks as $name => $callback ) {
 918                                 $db->setTransactionListener( $name, $callback );
 919                         }
 920                 }
 921
 922                 return $db;
 923         }
 924
 925         /**
 926          * @throws DBConnectionError
 927          */
 928         private function reportConnectionError() {
 929                 $conn = $this->errorConnection; // the connection which caused the error
 930                 $context = [
 931                         'method' => __METHOD__,
 932                         'last_error' => $this->mLastError,
 933                 ];
 934
 935                 if ( $conn instanceof IDatabase ) {
 936                         $context['db_server'] = $conn->getServer();
 937                         $this->connLogger->warning(
 938                                 "Connection error: {last_error} ({db_server})",
 939                                 $context
 940                         );
 941
 942                         // throws DBConnectionError
 943                         $conn->reportConnectionError( "{$this->mLastError} ({$context['db_server']})" );
 944                 } else {
 945                         // No last connection, probably due to all servers being too busy
 946                         $this->connLogger->error(
 947                                 "LB failure with no last connection. Connection error: {last_error}",
 948                                 $context
 949                         );
 950
 951                         // If all servers were busy, mLastError will contain something sensible
 952                         throw new DBConnectionError( null, $this->mLastError );
 953                 }
 954         }
 955
 956         public function getWriterIndex() {
 957                 return 0;
 958         }
 959
 960         public function haveIndex( $i ) {
 961                 return array_key_exists( $i, $this->mServers );
 962         }
 963
 964         public function isNonZeroLoad( $i ) {
 965                 return array_key_exists( $i, $this->mServers ) && $this->mLoads[$i] != 0;
 966         }
 967
 968         public function getServerCount() {
 969                 return count( $this->mServers );
 970         }
 971
 972         public function getServerName( $i ) {
 973                 if ( isset( $this->mServers[$i]['hostName'] ) ) {
 974                         $name = $this->mServers[$i]['hostName'];
 975                 } elseif ( isset( $this->mServers[$i]['host'] ) ) {
 976                         $name = $this->mServers[$i]['host'];
 977                 } else {
 978                         $name = '';
 979                 }
 980
 981                 return ( $name != '' ) ? $name : 'localhost';
 982         }
 983
 984         public function getServerInfo( $i ) {
 985                 if ( isset( $this->mServers[$i] ) ) {
 986                         return $this->mServers[$i];
 987                 } else {
 988                         return false;
 989                 }
 990         }
 991
 992         public function setServerInfo( $i, array $serverInfo ) {
 993                 $this->mServers[$i] = $serverInfo;
 994         }
 995
 996         public function getMasterPos() {
 997                 # If this entire request was served from a replica DB without opening a connection to the
 998                 # master (however unlikely that may be), then we can fetch the position from the replica DB.
 999                 $masterConn = $this->getAnyOpenConnection( $this->getWriterIndex() );
1000                 if ( !$masterConn ) {
1001                         $serverCount = count( $this->mServers );
1002                         for ( $i = 1; $i < $serverCount; $i++ ) {
1003                                 $conn = $this->getAnyOpenConnection( $i );
1004                                 if ( $conn ) {
1005                                         return $conn->getReplicaPos();
1006                                 }
1007                         }
1008                 } else {
1009                         return $masterConn->getMasterPos();
1010                 }
1011
1012                 return false;
1013         }
1014
1015         public function disable() {
1016                 $this->closeAll();
1017                 $this->disabled = true;
1018         }
1019
1020         public function closeAll() {
1021                 $this->forEachOpenConnection( function ( IDatabase $conn ) {
1022                         $host = $conn->getServer();
1023                         $this->connLogger->debug( "Closing connection to database '$host'." );
1024                         $conn->close();
1025                 } );
1026
1027                 $this->mConns = [
1028                         'local' => [],
1029                         'foreignFree' => [],
1030                         'foreignUsed' => [],
1031                 ];
1032                 $this->connsOpened = 0;
1033         }
1034
1035         public function closeConnection( IDatabase $conn ) {
1036                 $serverIndex = $conn->getLBInfo( 'serverIndex' ); // second index level of mConns
1037                 foreach ( $this->mConns as $type => $connsByServer ) {
1038                         if ( !isset( $connsByServer[$serverIndex] ) ) {
1039                                 continue;
1040                         }
1041
1042                         foreach ( $connsByServer[$serverIndex] as $i => $trackedConn ) {
1043                                 if ( $conn === $trackedConn ) {
1044                                         $host = $this->getServerName( $i );
1045                                         $this->connLogger->debug( "Closing connection to database $i at '$host'." );
1046                                         unset( $this->mConns[$type][$serverIndex][$i] );
1047                                         --$this->connsOpened;
1048                                         break 2;
1049                                 }
1050                         }
1051                 }
1052
1053                 $conn->close();
1054         }
1055
1056         public function commitAll( $fname = __METHOD__ ) {
1057                 $failures = [];
1058
1059                 $restore = ( $this->trxRoundId !== false );
1060                 $this->trxRoundId = false;
1061                 $this->forEachOpenConnection(
1062                         function ( IDatabase $conn ) use ( $fname, $restore, &$failures ) {
1063                                 try {
1064                                         $conn->commit( $fname, $conn::FLUSHING_ALL_PEERS );
1065                                 } catch ( DBError $e ) {
1066                                         call_user_func( $this->errorLogger, $e );
1067                                         $failures[] = "{$conn->getServer()}: {$e->getMessage()}";
1068                                 }
1069                                 if ( $restore && $conn->getLBInfo( 'master' ) ) {
1070                                         $this->undoTransactionRoundFlags( $conn );
1071                                 }
1072                         }
1073                 );
1074
1075                 if ( $failures ) {
1076                         throw new DBExpectedError(
1077                                 null,
1078                                 "Commit failed on server(s) " . implode( "\n", array_unique( $failures ) )
1079                         );
1080                 }
1081         }
1082
1083         public function finalizeMasterChanges() {
1084                 $this->forEachOpenMasterConnection( function ( Database $conn ) {
1085                         // Any error should cause all DB transactions to be rolled back together
1086                         $conn->setTrxEndCallbackSuppression( false );
1087                         $conn->runOnTransactionPreCommitCallbacks();
1088                         // Defer post-commit callbacks until COMMIT finishes for all DBs
1089                         $conn->setTrxEndCallbackSuppression( true );
1090                 } );
1091         }
1092
1093         public function approveMasterChanges( array $options ) {
1094                 $limit = isset( $options['maxWriteDuration'] ) ? $options['maxWriteDuration'] : 0;
1095                 $this->forEachOpenMasterConnection( function ( IDatabase $conn ) use ( $limit ) {
1096                         // If atomic sections or explicit transactions are still open, some caller must have
1097                         // caught an exception but failed to properly rollback any changes. Detect that and
1098                         // throw and error (causing rollback).
1099                         if ( $conn->explicitTrxActive() ) {
1100                                 throw new DBTransactionError(
1101                                         $conn,
1102                                         "Explicit transaction still active. A caller may have caught an error."
1103                                 );
1104                         }
1105                         // Assert that the time to replicate the transaction will be sane.
1106                         // If this fails, then all DB transactions will be rollback back together.
1107                         $time = $conn->pendingWriteQueryDuration( $conn::ESTIMATE_DB_APPLY );
1108                         if ( $limit > 0 && $time > $limit ) {
1109                                 throw new DBTransactionSizeError(
1110                                         $conn,
1111                                         "Transaction spent $time second(s) in writes, exceeding the $limit limit.",
1112                                         [ $time, $limit ]
1113                                 );
1114                         }
1115                         // If a connection sits idle while slow queries execute on another, that connection
1116                         // may end up dropped before the commit round is reached. Ping servers to detect this.
1117                         if ( $conn->writesOrCallbacksPending() && !$conn->ping() ) {
1118                                 throw new DBTransactionError(
1119                                         $conn,
1120                                         "A connection to the {$conn->getDBname()} database was lost before commit."
1121                                 );
1122                         }
1123                 } );
1124         }
1125
1126         public function beginMasterChanges( $fname = __METHOD__ ) {
1127                 if ( $this->trxRoundId !== false ) {
1128                         throw new DBTransactionError(
1129                                 null,
1130                                 "$fname: Transaction round '{$this->trxRoundId}' already started."
1131                         );
1132                 }
1133                 $this->trxRoundId = $fname;
1134
1135                 $failures = [];
1136                 $this->forEachOpenMasterConnection(
1137                         function ( Database $conn ) use ( $fname, &$failures ) {
1138                                 $conn->setTrxEndCallbackSuppression( true );
1139                                 try {
1140                                         $conn->flushSnapshot( $fname );
1141                                 } catch ( DBError $e ) {
1142                                         call_user_func( $this->errorLogger, $e );
1143                                         $failures[] = "{$conn->getServer()}: {$e->getMessage()}";
1144                                 }
1145                                 $conn->setTrxEndCallbackSuppression( false );
1146                                 $this->applyTransactionRoundFlags( $conn );
1147                         }
1148                 );
1149
1150                 if ( $failures ) {
1151                         throw new DBExpectedError(
1152                                 null,
1153                                 "$fname: Flush failed on server(s) " . implode( "\n", array_unique( $failures ) )
1154                         );
1155                 }
1156         }
1157
1158         public function commitMasterChanges( $fname = __METHOD__ ) {
1159                 $failures = [];
1160
1161                 /** @noinspection PhpUnusedLocalVariableInspection */
1162                 $scope = $this->getScopedPHPBehaviorForCommit(); // try to ignore client aborts
1163
1164                 $restore = ( $this->trxRoundId !== false );
1165                 $this->trxRoundId = false;
1166                 $this->forEachOpenMasterConnection(
1167                         function ( IDatabase $conn ) use ( $fname, $restore, &$failures ) {
1168                                 try {
1169                                         if ( $conn->writesOrCallbacksPending() ) {
1170                                                 $conn->commit( $fname, $conn::FLUSHING_ALL_PEERS );
1171                                         } elseif ( $restore ) {
1172                                                 $conn->flushSnapshot( $fname );
1173                                         }
1174                                 } catch ( DBError $e ) {
1175                                         call_user_func( $this->errorLogger, $e );
1176                                         $failures[] = "{$conn->getServer()}: {$e->getMessage()}";
1177                                 }
1178                                 if ( $restore ) {
1179                                         $this->undoTransactionRoundFlags( $conn );
1180                                 }
1181                         }
1182                 );
1183
1184                 if ( $failures ) {
1185                         throw new DBExpectedError(
1186                                 null,
1187                                 "$fname: Commit failed on server(s) " . implode( "\n", array_unique( $failures ) )
1188                         );
1189                 }
1190         }
1191
1192         public function runMasterPostTrxCallbacks( $type ) {
1193                 $e = null; // first exception
1194                 $this->forEachOpenMasterConnection( function ( Database $conn ) use ( $type, &$e ) {
1195                         $conn->setTrxEndCallbackSuppression( false );
1196                         if ( $conn->writesOrCallbacksPending() ) {
1197                                 // This happens if onTransactionIdle() callbacks leave callbacks on *another* DB
1198                                 // (which finished its callbacks already). Warn and recover in this case. Let the
1199                                 // callbacks run in the final commitMasterChanges() in LBFactory::shutdown().
1200                                 $this->queryLogger->error( __METHOD__ . ": found writes/callbacks pending." );
1201                                 return;
1202                         } elseif ( $conn->trxLevel() ) {
1203                                 // This happens for single-DB setups where DB_REPLICA uses the master DB,
1204                                 // thus leaving an implicit read-only transaction open at this point. It
1205                                 // also happens if onTransactionIdle() callbacks leave implicit transactions
1206                                 // open on *other* DBs (which is slightly improper). Let these COMMIT on the
1207                                 // next call to commitMasterChanges(), possibly in LBFactory::shutdown().
1208                                 return;
1209                         }
1210                         try {
1211                                 $conn->runOnTransactionIdleCallbacks( $type );
1212                         } catch ( Exception $ex ) {
1213                                 $e = $e ?: $ex;
1214                         }
1215                         try {
1216                                 $conn->runTransactionListenerCallbacks( $type );
1217                         } catch ( Exception $ex ) {
1218                                 $e = $e ?: $ex;
1219                         }
1220                 } );
1221
1222                 return $e;
1223         }
1224
1225         public function rollbackMasterChanges( $fname = __METHOD__ ) {
1226                 $restore = ( $this->trxRoundId !== false );
1227                 $this->trxRoundId = false;
1228                 $this->forEachOpenMasterConnection(
1229                         function ( IDatabase $conn ) use ( $fname, $restore ) {
1230                                 if ( $conn->writesOrCallbacksPending() ) {
1231                                         $conn->rollback( $fname, $conn::FLUSHING_ALL_PEERS );
1232                                 }
1233                                 if ( $restore ) {
1234                                         $this->undoTransactionRoundFlags( $conn );
1235                                 }
1236                         }
1237                 );
1238         }
1239
1240         public function suppressTransactionEndCallbacks() {
1241                 $this->forEachOpenMasterConnection( function ( Database $conn ) {
1242                         $conn->setTrxEndCallbackSuppression( true );
1243                 } );
1244         }
1245
1246         /**
1247          * @param IDatabase $conn
1248          */
1249         private function applyTransactionRoundFlags( IDatabase $conn ) {
1250                 if ( $conn->getFlag( $conn::DBO_DEFAULT ) ) {
1251                         // DBO_TRX is controlled entirely by CLI mode presence with DBO_DEFAULT.
1252                         // Force DBO_TRX even in CLI mode since a commit round is expected soon.
1253                         $conn->setFlag( $conn::DBO_TRX, $conn::REMEMBER_PRIOR );
1254                         // If config has explicitly requested DBO_TRX be either on or off by not
1255                         // setting DBO_DEFAULT, then respect that. Forcing no transactions is useful
1256                         // for things like blob stores (ExternalStore) which want auto-commit mode.
1257                 }
1258         }
1259
1260         /**
1261          * @param IDatabase $conn
1262          */
1263         private function undoTransactionRoundFlags( IDatabase $conn ) {
1264                 if ( $conn->getFlag( $conn::DBO_DEFAULT ) ) {
1265                         $conn->restoreFlags( $conn::RESTORE_PRIOR );
1266                 }
1267         }
1268
1269         public function flushReplicaSnapshots( $fname = __METHOD__ ) {
1270                 $this->forEachOpenReplicaConnection( function ( IDatabase $conn ) {
1271                         $conn->flushSnapshot( __METHOD__ );
1272                 } );
1273         }
1274
1275         public function hasMasterConnection() {
1276                 return $this->isOpen( $this->getWriterIndex() );
1277         }
1278
1279         public function hasMasterChanges() {
1280                 $pending = 0;
1281                 $this->forEachOpenMasterConnection( function ( IDatabase $conn ) use ( &$pending ) {
1282                         $pending |= $conn->writesOrCallbacksPending();
1283                 } );
1284
1285                 return (bool)$pending;
1286         }
1287
1288         public function lastMasterChangeTimestamp() {
1289                 $lastTime = false;
1290                 $this->forEachOpenMasterConnection( function ( IDatabase $conn ) use ( &$lastTime ) {
1291                         $lastTime = max( $lastTime, $conn->lastDoneWrites() );
1292                 } );
1293
1294                 return $lastTime;
1295         }
1296
1297         public function hasOrMadeRecentMasterChanges( $age = null ) {
1298                 $age = ( $age === null ) ? $this->mWaitTimeout : $age;
1299
1300                 return ( $this->hasMasterChanges()
1301                         || $this->lastMasterChangeTimestamp() > microtime( true ) - $age );
1302         }
1303
1304         public function pendingMasterChangeCallers() {
1305                 $fnames = [];
1306                 $this->forEachOpenMasterConnection( function ( IDatabase $conn ) use ( &$fnames ) {
1307                         $fnames = array_merge( $fnames, $conn->pendingWriteCallers() );
1308                 } );
1309
1310                 return $fnames;
1311         }
1312
1313         public function getLaggedReplicaMode( $domain = false ) {
1314                 // No-op if there is only one DB (also avoids recursion)
1315                 if ( !$this->laggedReplicaMode && $this->getServerCount() > 1 ) {
1316                         try {
1317                                 // See if laggedReplicaMode gets set
1318                                 $conn = $this->getConnection( self::DB_REPLICA, false, $domain );
1319                                 $this->reuseConnection( $conn );
1320                         } catch ( DBConnectionError $e ) {
1321                                 // Avoid expensive re-connect attempts and failures
1322                                 $this->allReplicasDownMode = true;
1323                                 $this->laggedReplicaMode = true;
1324                         }
1325                 }
1326
1327                 return $this->laggedReplicaMode;
1328         }
1329
1330         /**
1331          * @param bool $domain
1332          * @return bool
1333          * @deprecated 1.28; use getLaggedReplicaMode()
1334          */
1335         public function getLaggedSlaveMode( $domain = false ) {
1336                 return $this->getLaggedReplicaMode( $domain );
1337         }
1338
1339         public function laggedReplicaUsed() {
1340                 return $this->laggedReplicaMode;
1341         }
1342
1343         /**
1344          * @return bool
1345          * @since 1.27
1346          * @deprecated Since 1.28; use laggedReplicaUsed()
1347          */
1348         public function laggedSlaveUsed() {
1349                 return $this->laggedReplicaUsed();
1350         }
1351
1352         public function getReadOnlyReason( $domain = false, IDatabase $conn = null ) {
1353                 if ( $this->readOnlyReason !== false ) {
1354                         return $this->readOnlyReason;
1355                 } elseif ( $this->getLaggedReplicaMode( $domain ) ) {
1356                         if ( $this->allReplicasDownMode ) {
1357                                 return 'The database has been automatically locked ' .
1358                                         'until the replica database servers become available';
1359                         } else {
1360                                 return 'The database has been automatically locked ' .
1361                                         'while the replica database servers catch up to the master.';
1362                         }
1363                 } elseif ( $this->masterRunningReadOnly( $domain, $conn ) ) {
1364                         return 'The database master is running in read-only mode.';
1365                 }
1366
1367                 return false;
1368         }
1369
1370         /**
1371          * @param string $domain Domain ID, or false for the current domain
1372          * @param IDatabase|null $conn DB master connectionl used to avoid loops [optional]
1373          * @return bool
1374          */
1375         private function masterRunningReadOnly( $domain, IDatabase $conn = null ) {
1376                 $cache = $this->wanCache;
1377                 $masterServer = $this->getServerName( $this->getWriterIndex() );
1378
1379                 return (bool)$cache->getWithSetCallback(
1380                         $cache->makeGlobalKey( __CLASS__, 'server-read-only', $masterServer ),
1381                         self::TTL_CACHE_READONLY,
1382                         function () use ( $domain, $conn ) {
1383                                 $old = $this->trxProfiler->setSilenced( true );
1384                                 try {
1385                                         $dbw = $conn ?: $this->getConnection( self::DB_MASTER, [], $domain );
1386                                         $readOnly = (int)$dbw->serverIsReadOnly();
1387                                         if ( !$conn ) {
1388                                                 $this->reuseConnection( $dbw );
1389                                         }
1390                                 } catch ( DBError $e ) {
1391                                         $readOnly = 0;
1392                                 }
1393                                 $this->trxProfiler->setSilenced( $old );
1394                                 return $readOnly;
1395                         },
1396                         [ 'pcTTL' => $cache::TTL_PROC_LONG, 'busyValue' => 0 ]
1397                 );
1398         }
1399
1400         public function allowLagged( $mode = null ) {
1401                 if ( $mode === null ) {
1402                         return $this->mAllowLagged;
1403                 }
1404                 $this->mAllowLagged = $mode;
1405
1406                 return $this->mAllowLagged;
1407         }
1408
1409         public function pingAll() {
1410                 $success = true;
1411                 $this->forEachOpenConnection( function ( IDatabase $conn ) use ( &$success ) {
1412                         if ( !$conn->ping() ) {
1413                                 $success = false;
1414                         }
1415                 } );
1416
1417                 return $success;
1418         }
1419
1420         public function forEachOpenConnection( $callback, array $params = [] ) {
1421                 foreach ( $this->mConns as $connsByServer ) {
1422                         foreach ( $connsByServer as $serverConns ) {
1423                                 foreach ( $serverConns as $conn ) {
1424                                         $mergedParams = array_merge( [ $conn ], $params );
1425                                         call_user_func_array( $callback, $mergedParams );
1426                                 }
1427                         }
1428                 }
1429         }
1430
1431         public function forEachOpenMasterConnection( $callback, array $params = [] ) {
1432                 $masterIndex = $this->getWriterIndex();
1433                 foreach ( $this->mConns as $connsByServer ) {
1434                         if ( isset( $connsByServer[$masterIndex] ) ) {
1435                                 /** @var IDatabase $conn */
1436                                 foreach ( $connsByServer[$masterIndex] as $conn ) {
1437                                         $mergedParams = array_merge( [ $conn ], $params );
1438                                         call_user_func_array( $callback, $mergedParams );
1439                                 }
1440                         }
1441                 }
1442         }
1443
1444         public function forEachOpenReplicaConnection( $callback, array $params = [] ) {
1445                 foreach ( $this->mConns as $connsByServer ) {
1446                         foreach ( $connsByServer as $i => $serverConns ) {
1447                                 if ( $i === $this->getWriterIndex() ) {
1448                                         continue; // skip master
1449                                 }
1450                                 foreach ( $serverConns as $conn ) {
1451                                         $mergedParams = array_merge( [ $conn ], $params );
1452                                         call_user_func_array( $callback, $mergedParams );
1453                                 }
1454                         }
1455                 }
1456         }
1457
1458         public function getMaxLag( $domain = false ) {
1459                 $maxLag = -1;
1460                 $host = '';
1461                 $maxIndex = 0;
1462
1463                 if ( $this->getServerCount() <= 1 ) {
1464                         return [ $host, $maxLag, $maxIndex ]; // no replication = no lag
1465                 }
1466
1467                 $lagTimes = $this->getLagTimes( $domain );
1468                 foreach ( $lagTimes as $i => $lag ) {
1469                         if ( $this->mLoads[$i] > 0 && $lag > $maxLag ) {
1470                                 $maxLag = $lag;
1471                                 $host = $this->mServers[$i]['host'];
1472                                 $maxIndex = $i;
1473                         }
1474                 }
1475
1476                 return [ $host, $maxLag, $maxIndex ];
1477         }
1478
1479         public function getLagTimes( $domain = false ) {
1480                 if ( $this->getServerCount() <= 1 ) {
1481                         return [ $this->getWriterIndex() => 0 ]; // no replication = no lag
1482                 }
1483
1484                 $knownLagTimes = []; // map of (server index => 0 seconds)
1485                 $indexesWithLag = [];
1486                 foreach ( $this->mServers as $i => $server ) {
1487                         if ( empty( $server['is static'] ) ) {
1488                                 $indexesWithLag[] = $i; // DB server might have replication lag
1489                         } else {
1490                                 $knownLagTimes[$i] = 0; // DB server is a non-replicating and read-only archive
1491                         }
1492                 }
1493
1494                 return $this->getLoadMonitor()->getLagTimes( $indexesWithLag, $domain ) + $knownLagTimes;
1495         }
1496
1497         public function safeGetLag( IDatabase $conn ) {
1498                 if ( $this->getServerCount() <= 1 ) {
1499                         return 0;
1500                 } else {
1501                         return $conn->getLag();
1502                 }
1503         }
1504
1505         /**
1506          * @param IDatabase $conn
1507          * @param DBMasterPos|bool $pos
1508          * @param int $timeout
1509          * @return bool
1510          */
1511         public function safeWaitForMasterPos( IDatabase $conn, $pos = false, $timeout = 10 ) {
1512                 if ( $this->getServerCount() <= 1 || !$conn->getLBInfo( 'replica' ) ) {
1513                         return true; // server is not a replica DB
1514                 }
1515
1516                 if ( !$pos ) {
1517                         // Get the current master position, opening a connection if needed
1518                         $masterConn = $this->getAnyOpenConnection( $this->getWriterIndex() );
1519                         if ( $masterConn ) {
1520                                 $pos = $masterConn->getMasterPos();
1521                         } else {
1522                                 $masterConn = $this->openConnection( $this->getWriterIndex(), self::DOMAIN_ANY );
1523                                 $pos = $masterConn->getMasterPos();
1524                                 $this->closeConnection( $masterConn );
1525                         }
1526                 }
1527
1528                 if ( $pos instanceof DBMasterPos ) {
1529                         $result = $conn->masterPosWait( $pos, $timeout );
1530                         if ( $result == -1 || is_null( $result ) ) {
1531                                 $msg = __METHOD__ . ": Timed out waiting on {$conn->getServer()} pos {$pos}";
1532                                 $this->replLogger->warning( "$msg" );
1533                                 $ok = false;
1534                         } else {
1535                                 $this->replLogger->info( __METHOD__ . ": Done" );
1536                                 $ok = true;
1537                         }
1538                 } else {
1539                         $ok = false; // something is misconfigured
1540                         $this->replLogger->error( "Could not get master pos for {$conn->getServer()}." );
1541                 }
1542
1543                 return $ok;
1544         }
1545
1546         public function setTransactionListener( $name, callable $callback = null ) {
1547                 if ( $callback ) {
1548                         $this->trxRecurringCallbacks[$name] = $callback;
1549                 } else {
1550                         unset( $this->trxRecurringCallbacks[$name] );
1551                 }
1552                 $this->forEachOpenMasterConnection(
1553                         function ( IDatabase $conn ) use ( $name, $callback ) {
1554                                 $conn->setTransactionListener( $name, $callback );
1555                         }
1556                 );
1557         }
1558
1559         public function setTableAliases( array $aliases ) {
1560                 $this->tableAliases = $aliases;
1561         }
1562
1563         public function setDomainPrefix( $prefix ) {
1564                 if ( $this->mConns['foreignUsed'] ) {
1565                         // Do not switch connections to explicit foreign domains unless marked as free
1566                         $domains = [];
1567                         foreach ( $this->mConns['foreignUsed'] as $i => $connsByDomain ) {
1568                                 $domains = array_merge( $domains, array_keys( $connsByDomain ) );
1569                         }
1570                         $domains = implode( ', ', $domains );
1571                         throw new DBUnexpectedError( null,
1572                                 "Foreign domain connections are still in use ($domains)." );
1573                 }
1574
1575                 $this->localDomain = new DatabaseDomain(
1576                         $this->localDomain->getDatabase(),
1577                         null,
1578                         $prefix
1579                 );
1580
1581                 $this->forEachOpenConnection( function ( IDatabase $db ) use ( $prefix ) {
1582                         $db->tablePrefix( $prefix );
1583                 } );
1584         }
1585
1586         /**
1587          * Make PHP ignore user aborts/disconnects until the returned
1588          * value leaves scope. This returns null and does nothing in CLI mode.
1589          *
1590          * @return ScopedCallback|null
1591          */
1592         final protected function getScopedPHPBehaviorForCommit() {
1593                 if ( PHP_SAPI != 'cli' ) { // https://bugs.php.net/bug.php?id=47540
1594                         $old = ignore_user_abort( true ); // avoid half-finished operations
1595                         return new ScopedCallback( function () use ( $old ) {
1596                                 ignore_user_abort( $old );
1597                         } );
1598                 }
1599
1600                 return null;
1601         }
1602
1603         function __destruct() {
1604                 // Avoid connection leaks for sanity
1605                 $this->disable();
1606         }
1607 }
1608
1609 class_alias( LoadBalancer::class, 'LoadBalancer' );