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 BagOStuff;
  29 use EmptyBagOStuff;
  30 use WANObjectCache;
  31 use ArrayUtils;
  32 use InvalidArgumentException;
  33 use RuntimeException;
  34 use Exception;
  35
  36 /**
  37  * Database connection, tracking, load balancing, and transaction manager for a cluster
  38  *
  39  * @ingroup Database
  40  */
  41 class LoadBalancer implements ILoadBalancer {
  42         /** @var array[] Map of (server index => server config array) */
  43         private $mServers;
  44         /** @var Database[][][] Map of local/foreignUsed/foreignFree => server index => IDatabase[] */
  45         private $mConns;
  46         /** @var float[] Map of (server index => weight) */
  47         private $mLoads;
  48         /** @var array[] Map of (group => server index => weight) */
  49         private $mGroupLoads;
  50         /** @var bool Whether to disregard replica DB lag as a factor in replica DB selection */
  51         private $mAllowLagged;
  52         /** @var integer Seconds to spend waiting on replica DB lag to resolve */
  53         private $mWaitTimeout;
  54         /** @var array The LoadMonitor configuration */
  55         private $loadMonitorConfig;
  56         /** @var array[] $aliases Map of (table => (dbname, schema, prefix) map) */
  57         private $tableAliases = [];
  58
  59         /** @var ILoadMonitor */
  60         private $loadMonitor;
  61         /** @var ChronologyProtector|null */
  62         private $chronProt;
  63         /** @var BagOStuff */
  64         private $srvCache;
  65         /** @var BagOStuff */
  66         private $memCache;
  67         /** @var WANObjectCache */
  68         private $wanCache;
  69         /** @var object|string Class name or object With profileIn/profileOut methods */
  70         protected $profiler;
  71         /** @var TransactionProfiler */
  72         protected $trxProfiler;
  73         /** @var LoggerInterface */
  74         protected $replLogger;
  75         /** @var LoggerInterface */
  76         protected $connLogger;
  77         /** @var LoggerInterface */
  78         protected $queryLogger;
  79         /** @var LoggerInterface */
  80         protected $perfLogger;
  81
  82         /** @var Database DB connection object that caused a problem */
  83         private $errorConnection;
  84         /** @var integer The generic (not query grouped) replica DB index (of $mServers) */
  85         private $mReadIndex;
  86         /** @var bool|DBMasterPos False if not set */
  87         private $mWaitForPos;
  88         /** @var bool Whether the generic reader fell back to a lagged replica DB */
  89         private $laggedReplicaMode = false;
  90         /** @var bool Whether the generic reader fell back to a lagged replica DB */
  91         private $allReplicasDownMode = false;
  92         /** @var string The last DB selection or connection error */
  93         private $mLastError = 'Unknown error';
  94         /** @var string|bool Reason the LB is read-only or false if not */
  95         private $readOnlyReason = false;
  96         /** @var integer Total connections opened */
  97         private $connsOpened = 0;
  98         /** @var string|bool String if a requested DBO_TRX transaction round is active */
  99         private $trxRoundId = false;
 100         /** @var array[] Map of (name => callable) */
 101         private $trxRecurringCallbacks = [];
 102         /** @var DatabaseDomain Local Domain ID and default for selectDB() calls */
 103         private $localDomain;
 104         /** @var string Alternate ID string for the domain instead of DatabaseDomain::getId() */
 105         private $localDomainIdAlias;
 106         /** @var string Current server name */
 107         private $host;
 108         /** @var bool Whether this PHP instance is for a CLI script */
 109         protected $cliMode;
 110         /** @var string Agent name for query profiling */
 111         protected $agent;
 112
 113         /** @var callable Exception logger */
 114         private $errorLogger;
 115
 116         /** @var boolean */
 117         private $disabled = false;
 118         /** @var boolean */
 119         private $chronProtInitialized = false;
 120
 121         /** @var integer Warn when this many connection are held */
 122         const CONN_HELD_WARN_THRESHOLD = 10;
 123
 124         /** @var integer Default 'max lag' when unspecified */
 125         const MAX_LAG_DEFAULT = 10;
 126         /** @var integer Seconds to cache master server read-only status */
 127         const TTL_CACHE_READONLY = 5;
 128
 129         const KEY_LOCAL = 'local';
 130         const KEY_FOREIGN_FREE = 'foreignFree';
 131         const KEY_FOREIGN_INUSE = 'foreignInUse';
 132
 133         public function __construct( array $params ) {
 134                 if ( !isset( $params['servers'] ) ) {
 135                         throw new InvalidArgumentException( __CLASS__ . ': missing servers parameter' );
 136                 }
 137                 $this->mServers = $params['servers'];
 138
 139                 $this->localDomain = isset( $params['localDomain'] )
 140                         ? DatabaseDomain::newFromId( $params['localDomain'] )
 141                         : DatabaseDomain::newUnspecified();
 142                 // In case a caller assumes that the domain ID is simply <db>-<prefix>, which is almost
 143                 // always true, gracefully handle the case when they fail to account for escaping.
 144                 if ( $this->localDomain->getTablePrefix() != '' ) {
 145                         $this->localDomainIdAlias =
 146                                 $this->localDomain->getDatabase() . '-' . $this->localDomain->getTablePrefix();
 147                 } else {
 148                         $this->localDomainIdAlias = $this->localDomain->getDatabase();
 149                 }
 150
 151                 $this->mWaitTimeout = isset( $params['waitTimeout'] ) ? $params['waitTimeout'] : 10;
 152
 153                 $this->mReadIndex = -1;
 154                 $this->mConns = [
 155                         self::KEY_LOCAL => [],
 156                         self::KEY_FOREIGN_INUSE => [],
 157                         self::KEY_FOREIGN_FREE => []
 158                 ];
 159                 $this->mLoads = [];
 160                 $this->mWaitForPos = false;
 161                 $this->mAllowLagged = false;
 162
 163                 if ( isset( $params['readOnlyReason'] ) && is_string( $params['readOnlyReason'] ) ) {
 164                         $this->readOnlyReason = $params['readOnlyReason'];
 165                 }
 166
 167                 if ( isset( $params['loadMonitor'] ) ) {
 168                         $this->loadMonitorConfig = $params['loadMonitor'];
 169                 } else {
 170                         $this->loadMonitorConfig = [ 'class' => 'LoadMonitorNull' ];
 171                 }
 172
 173                 foreach ( $params['servers'] as $i => $server ) {
 174                         $this->mLoads[$i] = $server['load'];
 175                         if ( isset( $server['groupLoads'] ) ) {
 176                                 foreach ( $server['groupLoads'] as $group => $ratio ) {
 177                                         if ( !isset( $this->mGroupLoads[$group] ) ) {
 178                                                 $this->mGroupLoads[$group] = [];
 179                                         }
 180                                         $this->mGroupLoads[$group][$i] = $ratio;
 181                                 }
 182                         }
 183                 }
 184
 185                 if ( isset( $params['srvCache'] ) ) {
 186                         $this->srvCache = $params['srvCache'];
 187                 } else {
 188                         $this->srvCache = new EmptyBagOStuff();
 189                 }
 190                 if ( isset( $params['memCache'] ) ) {
 191                         $this->memCache = $params['memCache'];
 192                 } else {
 193                         $this->memCache = new EmptyBagOStuff();
 194                 }
 195                 if ( isset( $params['wanCache'] ) ) {
 196                         $this->wanCache = $params['wanCache'];
 197                 } else {
 198                         $this->wanCache = WANObjectCache::newEmpty();
 199                 }
 200                 $this->profiler = isset( $params['profiler'] ) ? $params['profiler'] : null;
 201                 if ( isset( $params['trxProfiler'] ) ) {
 202                         $this->trxProfiler = $params['trxProfiler'];
 203                 } else {
 204                         $this->trxProfiler = new TransactionProfiler();
 205                 }
 206
 207                 $this->errorLogger = isset( $params['errorLogger'] )
 208                         ? $params['errorLogger']
 209                         : function ( Exception $e ) {
 210                                 trigger_error( get_class( $e ) . ': ' . $e->getMessage(), E_USER_WARNING );
 211                         };
 212
 213                 foreach ( [ 'replLogger', 'connLogger', 'queryLogger', 'perfLogger' ] as $key ) {
 214                         $this->$key = isset( $params[$key] ) ? $params[$key] : new NullLogger();
 215                 }
 216
 217                 $this->host = isset( $params['hostname'] )
 218                         ? $params['hostname']
 219                         : ( gethostname() ?: 'unknown' );
 220                 $this->cliMode = isset( $params['cliMode'] ) ? $params['cliMode'] : PHP_SAPI === 'cli';
 221                 $this->agent = isset( $params['agent'] ) ? $params['agent'] : '';
 222
 223                 if ( isset( $params['chronologyProtector'] ) ) {
 224                         $this->chronProt = $params['chronologyProtector'];
 225                 }
 226         }
 227
 228         /**
 229          * Get a LoadMonitor instance
 230          *
 231          * @return ILoadMonitor
 232          */
 233         private function getLoadMonitor() {
 234                 if ( !isset( $this->loadMonitor ) ) {
 235                         $compat = [
 236                                 'LoadMonitor' => LoadMonitor::class,
 237                                 'LoadMonitorNull' => LoadMonitorNull::class,
 238                                 'LoadMonitorMySQL' => LoadMonitorMySQL::class,
 239                         ];
 240
 241                         $class = $this->loadMonitorConfig['class'];
 242                         if ( isset( $compat[$class] ) ) {
 243                                 $class = $compat[$class];
 244                         }
 245
 246                         $this->loadMonitor = new $class(
 247                                 $this, $this->srvCache, $this->memCache, $this->loadMonitorConfig );
 248                         $this->loadMonitor->setLogger( $this->replLogger );
 249                 }
 250
 251                 return $this->loadMonitor;
 252         }
 253
 254         /**
 255          * @param array $loads
 256          * @param bool|string $domain Domain to get non-lagged for
 257          * @param int $maxLag Restrict the maximum allowed lag to this many seconds
 258          * @return bool|int|string
 259          */
 260         private function getRandomNonLagged( array $loads, $domain = false, $maxLag = INF ) {
 261                 $lags = $this->getLagTimes( $domain );
 262
 263                 # Unset excessively lagged servers
 264                 foreach ( $lags as $i => $lag ) {
 265                         if ( $i != 0 ) {
 266                                 # How much lag this server nominally is allowed to have
 267                                 $maxServerLag = isset( $this->mServers[$i]['max lag'] )
 268                                         ? $this->mServers[$i]['max lag']
 269                                         : self::MAX_LAG_DEFAULT; // default
 270                                 # Constrain that futher by $maxLag argument
 271                                 $maxServerLag = min( $maxServerLag, $maxLag );
 272
 273                                 $host = $this->getServerName( $i );
 274                                 if ( $lag === false && !is_infinite( $maxServerLag ) ) {
 275                                         $this->replLogger->error(
 276                                                 "Server {host} is not replicating?", [ 'host' => $host ] );
 277                                         unset( $loads[$i] );
 278                                 } elseif ( $lag > $maxServerLag ) {
 279                                         $this->replLogger->warning(
 280                                                 "Server {host} has {lag} seconds of lag (>= {maxlag})",
 281                                                 [ 'host' => $host, 'lag' => $lag, 'maxlag' => $maxServerLag ]
 282                                         );
 283                                         unset( $loads[$i] );
 284                                 }
 285                         }
 286                 }
 287
 288                 # Find out if all the replica DBs with non-zero load are lagged
 289                 $sum = 0;
 290                 foreach ( $loads as $load ) {
 291                         $sum += $load;
 292                 }
 293                 if ( $sum == 0 ) {
 294                         # No appropriate DB servers except maybe the master and some replica DBs with zero load
 295                         # Do NOT use the master
 296                         # Instead, this function will return false, triggering read-only mode,
 297                         # and a lagged replica DB will be used instead.
 298                         return false;
 299                 }
 300
 301                 if ( count( $loads ) == 0 ) {
 302                         return false;
 303                 }
 304
 305                 # Return a random representative of the remainder
 306                 return ArrayUtils::pickRandom( $loads );
 307         }
 308
 309         public function getReaderIndex( $group = false, $domain = false ) {
 310                 if ( count( $this->mServers ) == 1 ) {
 311                         // Skip the load balancing if there's only one server
 312                         return $this->getWriterIndex();
 313                 } elseif ( $group === false && $this->mReadIndex >= 0 ) {
 314                         // Shortcut if the generic reader index was already cached
 315                         return $this->mReadIndex;
 316                 }
 317
 318                 if ( $group !== false ) {
 319                         // Use the server weight array for this load group
 320                         if ( isset( $this->mGroupLoads[$group] ) ) {
 321                                 $loads = $this->mGroupLoads[$group];
 322                         } else {
 323                                 // No loads for this group, return false and the caller can use some other group
 324                                 $this->connLogger->info( __METHOD__ . ": no loads for group $group" );
 325
 326                                 return false;
 327                         }
 328                 } else {
 329                         // Use the generic load group
 330                         $loads = $this->mLoads;
 331                 }
 332
 333                 // Scale the configured load ratios according to each server's load and state
 334                 $this->getLoadMonitor()->scaleLoads( $loads, $domain );
 335
 336                 // Pick a server to use, accounting for weights, load, lag, and mWaitForPos
 337                 list( $i, $laggedReplicaMode ) = $this->pickReaderIndex( $loads, $domain );
 338                 if ( $i === false ) {
 339                         // Replica DB connection unsuccessful
 340                         return false;
 341                 }
 342
 343                 if ( $this->mWaitForPos && $i != $this->getWriterIndex() ) {
 344                         // Before any data queries are run, wait for the server to catch up to the
 345                         // specified position. This is used to improve session consistency. Note that
 346                         // when LoadBalancer::waitFor() sets mWaitForPos, the waiting triggers here,
 347                         // so update laggedReplicaMode as needed for consistency.
 348                         if ( !$this->doWait( $i ) ) {
 349                                 $laggedReplicaMode = true;
 350                         }
 351                 }
 352
 353                 if ( $this->mReadIndex <= 0 && $this->mLoads[$i] > 0 && $group === false ) {
 354                         // Cache the generic reader index for future ungrouped DB_REPLICA handles
 355                         $this->mReadIndex = $i;
 356                         // Record if the generic reader index is in "lagged replica DB" mode
 357                         if ( $laggedReplicaMode ) {
 358                                 $this->laggedReplicaMode = true;
 359                         }
 360                 }
 361
 362                 $serverName = $this->getServerName( $i );
 363                 $this->connLogger->debug( __METHOD__ . ": using server $serverName for group '$group'" );
 364
 365                 return $i;
 366         }
 367
 368         /**
 369          * @param array $loads List of server weights
 370          * @param string|bool $domain
 371          * @return array (reader index, lagged replica mode) or false on failure
 372          */
 373         private function pickReaderIndex( array $loads, $domain = false ) {
 374                 if ( !count( $loads ) ) {
 375                         throw new InvalidArgumentException( "Empty server array given to LoadBalancer" );
 376                 }
 377
 378                 /** @var $i int|bool Index of selected server */
 379                 $i = false;
 380                 /** @var $laggedReplicaMode bool Whether server is considered lagged */
 381                 $laggedReplicaMode = false;
 382
 383                 // Quickly look through the available servers for a server that meets criteria...
 384                 $currentLoads = $loads;
 385                 while ( count( $currentLoads ) ) {
 386                         if ( $this->mAllowLagged || $laggedReplicaMode ) {
 387                                 $i = ArrayUtils::pickRandom( $currentLoads );
 388                         } else {
 389                                 $i = false;
 390                                 if ( $this->mWaitForPos && $this->mWaitForPos->asOfTime() ) {
 391                                         // ChronologyProtecter sets mWaitForPos for session consistency.
 392                                         // This triggers doWait() after connect, so it's especially good to
 393                                         // avoid lagged servers so as to avoid excessive delay in that method.
 394                                         $ago = microtime( true ) - $this->mWaitForPos->asOfTime();
 395                                         // Aim for <= 1 second of waiting (being too picky can backfire)
 396                                         $i = $this->getRandomNonLagged( $currentLoads, $domain, $ago + 1 );
 397                                 }
 398                                 if ( $i === false ) {
 399                                         // Any server with less lag than it's 'max lag' param is preferable
 400                                         $i = $this->getRandomNonLagged( $currentLoads, $domain );
 401                                 }
 402                                 if ( $i === false && count( $currentLoads ) != 0 ) {
 403                                         // All replica DBs lagged. Switch to read-only mode
 404                                         $this->replLogger->error( "All replica DBs lagged. Switch to read-only mode" );
 405                                         $i = ArrayUtils::pickRandom( $currentLoads );
 406                                         $laggedReplicaMode = true;
 407                                 }
 408                         }
 409
 410                         if ( $i === false ) {
 411                                 // pickRandom() returned false.
 412                                 // This is permanent and means the configuration or the load monitor
 413                                 // wants us to return false.
 414                                 $this->connLogger->debug( __METHOD__ . ": pickRandom() returned false" );
 415
 416                                 return [ false, false ];
 417                         }
 418
 419                         $serverName = $this->getServerName( $i );
 420                         $this->connLogger->debug( __METHOD__ . ": Using reader #$i: $serverName..." );
 421
 422                         $conn = $this->openConnection( $i, $domain );
 423                         if ( !$conn ) {
 424                                 $this->connLogger->warning( __METHOD__ . ": Failed connecting to $i/$domain" );
 425                                 unset( $currentLoads[$i] ); // avoid this server next iteration
 426                                 $i = false;
 427                                 continue;
 428                         }
 429
 430                         // Decrement reference counter, we are finished with this connection.
 431                         // It will be incremented for the caller later.
 432                         if ( $domain !== false ) {
 433                                 $this->reuseConnection( $conn );
 434                         }
 435
 436                         // Return this server
 437                         break;
 438                 }
 439
 440                 // If all servers were down, quit now
 441                 if ( !count( $currentLoads ) ) {
 442                         $this->connLogger->error( "All servers down" );
 443                 }
 444
 445                 return [ $i, $laggedReplicaMode ];
 446         }
 447
 448         public function waitFor( $pos ) {
 449                 $oldPos = $this->mWaitForPos;
 450                 try {
 451                         $this->mWaitForPos = $pos;
 452                         // If a generic reader connection was already established, then wait now
 453                         $i = $this->mReadIndex;
 454                         if ( $i > 0 ) {
 455                                 if ( !$this->doWait( $i ) ) {
 456                                         $this->laggedReplicaMode = true;
 457                                 }
 458                         }
 459                 } finally {
 460                         // Restore the older position if it was higher since this is used for lag-protection
 461                         $this->setWaitForPositionIfHigher( $oldPos );
 462                 }
 463         }
 464
 465         public function waitForOne( $pos, $timeout = null ) {
 466                 $oldPos = $this->mWaitForPos;
 467                 try {
 468                         $this->mWaitForPos = $pos;
 469
 470                         $i = $this->mReadIndex;
 471                         if ( $i <= 0 ) {
 472                                 // Pick a generic replica DB if there isn't one yet
 473                                 $readLoads = $this->mLoads;
 474                                 unset( $readLoads[$this->getWriterIndex()] ); // replica DBs only
 475                                 $readLoads = array_filter( $readLoads ); // with non-zero load
 476                                 $i = ArrayUtils::pickRandom( $readLoads );
 477                         }
 478
 479                         if ( $i > 0 ) {
 480                                 $ok = $this->doWait( $i, true, $timeout );
 481                         } else {
 482                                 $ok = true; // no applicable loads
 483                         }
 484                 } finally {
 485                         # Restore the old position, as this is not used for lag-protection but for throttling
 486                         $this->mWaitForPos = $oldPos;
 487                 }
 488
 489                 return $ok;
 490         }
 491
 492         public function waitForAll( $pos, $timeout = null ) {
 493                 $oldPos = $this->mWaitForPos;
 494                 try {
 495                         $this->mWaitForPos = $pos;
 496                         $serverCount = count( $this->mServers );
 497
 498                         $ok = true;
 499                         for ( $i = 1; $i < $serverCount; $i++ ) {
 500                                 if ( $this->mLoads[$i] > 0 ) {
 501                                         $ok = $this->doWait( $i, true, $timeout ) && $ok;
 502                                 }
 503                         }
 504                 } finally {
 505                         # Restore the old position, as this is not used for lag-protection but for throttling
 506                         $this->mWaitForPos = $oldPos;
 507                 }
 508
 509                 return $ok;
 510         }
 511
 512         /**
 513          * @param DBMasterPos|bool $pos
 514          */
 515         private function setWaitForPositionIfHigher( $pos ) {
 516                 if ( !$pos ) {
 517                         return;
 518                 }
 519
 520                 if ( !$this->mWaitForPos || $pos->hasReached( $this->mWaitForPos ) ) {
 521                         $this->mWaitForPos = $pos;
 522                 }
 523         }
 524
 525         /**
 526          * @param int $i
 527          * @return IDatabase|bool
 528          */
 529         public function getAnyOpenConnection( $i ) {
 530                 foreach ( $this->mConns as $connsByServer ) {
 531                         if ( !empty( $connsByServer[$i] ) ) {
 532                                 /** @var $serverConns IDatabase[] */
 533                                 $serverConns = $connsByServer[$i];
 534
 535                                 return reset( $serverConns );
 536                         }
 537                 }
 538
 539                 return false;
 540         }
 541
 542         /**
 543          * Wait for a given replica DB to catch up to the master pos stored in $this
 544          * @param int $index Server index
 545          * @param bool $open Check the server even if a new connection has to be made
 546          * @param int $timeout Max seconds to wait; default is mWaitTimeout
 547          * @return bool
 548          */
 549         protected function doWait( $index, $open = false, $timeout = null ) {
 550                 $close = false; // close the connection afterwards
 551
 552                 // Check if we already know that the DB has reached this point
 553                 $server = $this->getServerName( $index );
 554                 $key = $this->srvCache->makeGlobalKey( __CLASS__, 'last-known-pos', $server, 'v1' );
 555                 /** @var DBMasterPos $knownReachedPos */
 556                 $knownReachedPos = $this->srvCache->get( $key );
 557                 if (
 558                         $knownReachedPos instanceof DBMasterPos &&
 559                         $knownReachedPos->hasReached( $this->mWaitForPos )
 560                 ) {
 561                         $this->replLogger->debug( __METHOD__ .
 562                                 ": replica DB $server known to be caught up (pos >= $knownReachedPos)." );
 563                         return true;
 564                 }
 565
 566                 // Find a connection to wait on, creating one if needed and allowed
 567                 $conn = $this->getAnyOpenConnection( $index );
 568                 if ( !$conn ) {
 569                         if ( !$open ) {
 570                                 $this->replLogger->debug( __METHOD__ . ": no connection open for $server" );
 571
 572                                 return false;
 573                         } else {
 574                                 $conn = $this->openConnection( $index, self::DOMAIN_ANY );
 575                                 if ( !$conn ) {
 576                                         $this->replLogger->warning( __METHOD__ . ": failed to connect to $server" );
 577
 578                                         return false;
 579                                 }
 580                                 // Avoid connection spam in waitForAll() when connections
 581                                 // are made just for the sake of doing this lag check.
 582                                 $close = true;
 583                         }
 584                 }
 585
 586                 $this->replLogger->info( __METHOD__ . ": Waiting for replica DB $server to catch up..." );
 587                 $timeout = $timeout ?: $this->mWaitTimeout;
 588                 $result = $conn->masterPosWait( $this->mWaitForPos, $timeout );
 589
 590                 if ( $result == -1 || is_null( $result ) ) {
 591                         // Timed out waiting for replica DB, use master instead
 592                         $this->replLogger->warning(
 593                                 __METHOD__ . ": Timed out waiting on {host} pos {$this->mWaitForPos}",
 594                                 [ 'host' => $server ]
 595                         );
 596                         $ok = false;
 597                 } else {
 598                         $this->replLogger->info( __METHOD__ . ": Done" );
 599                         $ok = true;
 600                         // Remember that the DB reached this point
 601                         $this->srvCache->set( $key, $this->mWaitForPos, BagOStuff::TTL_DAY );
 602                 }
 603
 604                 if ( $close ) {
 605                         $this->closeConnection( $conn );
 606                 }
 607
 608                 return $ok;
 609         }
 610
 611         /**
 612          * @see ILoadBalancer::getConnection()
 613          *
 614          * @param int $i
 615          * @param array $groups
 616          * @param bool $domain
 617          * @return Database
 618          * @throws DBConnectionError
 619          */
 620         public function getConnection( $i, $groups = [], $domain = false ) {
 621                 if ( $i === null || $i === false ) {
 622                         throw new InvalidArgumentException( 'Attempt to call ' . __METHOD__ .
 623                                 ' with invalid server index' );
 624                 }
 625
 626                 if ( $this->localDomain->equals( $domain ) || $domain === $this->localDomainIdAlias ) {
 627                         $domain = false; // local connection requested
 628                 }
 629
 630                 $groups = ( $groups === false || $groups === [] )
 631                         ? [ false ] // check one "group": the generic pool
 632                         : (array)$groups;
 633
 634                 $masterOnly = ( $i == self::DB_MASTER || $i == $this->getWriterIndex() );
 635                 $oldConnsOpened = $this->connsOpened; // connections open now
 636
 637                 if ( $i == self::DB_MASTER ) {
 638                         $i = $this->getWriterIndex();
 639                 } else {
 640                         # Try to find an available server in any the query groups (in order)
 641                         foreach ( $groups as $group ) {
 642                                 $groupIndex = $this->getReaderIndex( $group, $domain );
 643                                 if ( $groupIndex !== false ) {
 644                                         $i = $groupIndex;
 645                                         break;
 646                                 }
 647                         }
 648                 }
 649
 650                 # Operation-based index
 651                 if ( $i == self::DB_REPLICA ) {
 652                         $this->mLastError = 'Unknown error'; // reset error string
 653                         # Try the general server pool if $groups are unavailable.
 654                         $i = ( $groups === [ false ] )
 655                                 ? false // don't bother with this if that is what was tried above
 656                                 : $this->getReaderIndex( false, $domain );
 657                         # Couldn't find a working server in getReaderIndex()?
 658                         if ( $i === false ) {
 659                                 $this->mLastError = 'No working replica DB server: ' . $this->mLastError;
 660                                 // Throw an exception
 661                                 $this->reportConnectionError();
 662                                 return null; // not reached
 663                         }
 664                 }
 665
 666                 # Now we have an explicit index into the servers array
 667                 $conn = $this->openConnection( $i, $domain );
 668                 if ( !$conn ) {
 669                         // Throw an exception
 670                         $this->reportConnectionError();
 671                         return null; // not reached
 672                 }
 673
 674                 # Profile any new connections that happen
 675                 if ( $this->connsOpened > $oldConnsOpened ) {
 676                         $host = $conn->getServer();
 677                         $dbname = $conn->getDBname();
 678                         $this->trxProfiler->recordConnection( $host, $dbname, $masterOnly );
 679                 }
 680
 681                 if ( $masterOnly ) {
 682                         # Make master-requested DB handles inherit any read-only mode setting
 683                         $conn->setLBInfo( 'readOnlyReason', $this->getReadOnlyReason( $domain, $conn ) );
 684                 }
 685
 686                 return $conn;
 687         }
 688
 689         public function reuseConnection( $conn ) {
 690                 $serverIndex = $conn->getLBInfo( 'serverIndex' );
 691                 $refCount = $conn->getLBInfo( 'foreignPoolRefCount' );
 692                 if ( $serverIndex === null || $refCount === null ) {
 693                         /**
 694                          * This can happen in code like:
 695                          *   foreach ( $dbs as $db ) {
 696                          *     $conn = $lb->getConnection( $lb::DB_REPLICA, [], $db );
 697                          *     ...
 698                          *     $lb->reuseConnection( $conn );
 699                          *   }
 700                          * When a connection to the local DB is opened in this way, reuseConnection()
 701                          * should be ignored
 702                          */
 703                         return;
 704                 } elseif ( $conn instanceof DBConnRef ) {
 705                         // DBConnRef already handles calling reuseConnection() and only passes the live
 706                         // Database instance to this method. Any caller passing in a DBConnRef is broken.
 707                         $this->connLogger->error( __METHOD__ . ": got DBConnRef instance.\n" .
 708                                 ( new RuntimeException() )->getTraceAsString() );
 709
 710                         return;
 711                 }
 712
 713                 if ( $this->disabled ) {
 714                         return; // DBConnRef handle probably survived longer than the LoadBalancer
 715                 }
 716
 717                 $domain = $conn->getDomainID();
 718                 if ( !isset( $this->mConns[self::KEY_FOREIGN_INUSE][$serverIndex][$domain] ) ) {
 719                         throw new InvalidArgumentException( __METHOD__ .
 720                                 ": connection $serverIndex/$domain not found; it may have already been freed." );
 721                 } elseif ( $this->mConns[self::KEY_FOREIGN_INUSE][$serverIndex][$domain] !== $conn ) {
 722                         throw new InvalidArgumentException( __METHOD__ .
 723                                 ": connection $serverIndex/$domain mismatched; it may have already been freed." );
 724                 }
 725                 $conn->setLBInfo( 'foreignPoolRefCount', --$refCount );
 726                 if ( $refCount <= 0 ) {
 727                         $this->mConns[self::KEY_FOREIGN_FREE][$serverIndex][$domain] = $conn;
 728                         unset( $this->mConns[self::KEY_FOREIGN_INUSE][$serverIndex][$domain] );
 729                         if ( !$this->mConns[self::KEY_FOREIGN_INUSE][$serverIndex] ) {
 730                                 unset( $this->mConns[ self::KEY_FOREIGN_INUSE ][$serverIndex] ); // clean up
 731                         }
 732                         $this->connLogger->debug( __METHOD__ . ": freed connection $serverIndex/$domain" );
 733                 } else {
 734                         $this->connLogger->debug( __METHOD__ .
 735                                 ": reference count for $serverIndex/$domain reduced to $refCount" );
 736                 }
 737         }
 738
 739         public function getConnectionRef( $db, $groups = [], $domain = false ) {
 740                 $domain = ( $domain !== false ) ? $domain : $this->localDomain;
 741
 742                 return new DBConnRef( $this, $this->getConnection( $db, $groups, $domain ) );
 743         }
 744
 745         public function getLazyConnectionRef( $db, $groups = [], $domain = false ) {
 746                 $domain = ( $domain !== false ) ? $domain : $this->localDomain;
 747
 748                 return new DBConnRef( $this, [ $db, $groups, $domain ] );
 749         }
 750
 751         public function getMaintenanceConnectionRef( $db, $groups = [], $domain = false ) {
 752                 $domain = ( $domain !== false ) ? $domain : $this->localDomain;
 753
 754                 return new MaintainableDBConnRef( $this, $this->getConnection( $db, $groups, $domain ) );
 755         }
 756
 757         /**
 758          * @see ILoadBalancer::openConnection()
 759          *
 760          * @param int $i
 761          * @param bool $domain
 762          * @return bool|Database
 763          * @throws DBAccessError
 764          */
 765         public function openConnection( $i, $domain = false ) {
 766                 if ( $this->localDomain->equals( $domain ) || $domain === $this->localDomainIdAlias ) {
 767                         $domain = false; // local connection requested
 768                 }
 769
 770                 if ( !$this->chronProtInitialized && $this->chronProt ) {
 771                         $this->connLogger->debug( __METHOD__ . ': calling initLB() before first connection.' );
 772                         // Load CP positions before connecting so that doWait() triggers later if needed
 773                         $this->chronProtInitialized = true;
 774                         $this->chronProt->initLB( $this );
 775                 }
 776
 777                 if ( $domain !== false ) {
 778                         $conn = $this->openForeignConnection( $i, $domain );
 779                 } elseif ( isset( $this->mConns[self::KEY_LOCAL][$i][0] ) ) {
 780                         $conn = $this->mConns[self::KEY_LOCAL][$i][0];
 781                 } else {
 782                         if ( !isset( $this->mServers[$i] ) || !is_array( $this->mServers[$i] ) ) {
 783                                 throw new InvalidArgumentException( "No server with index '$i'." );
 784                         }
 785                         // Open a new connection
 786                         $server = $this->mServers[$i];
 787                         $server['serverIndex'] = $i;
 788                         $conn = $this->reallyOpenConnection( $server, false );
 789                         $serverName = $this->getServerName( $i );
 790                         if ( $conn->isOpen() ) {
 791                                 $this->connLogger->debug( "Connected to database $i at '$serverName'." );
 792                                 $this->mConns[self::KEY_LOCAL][$i][0] = $conn;
 793                         } else {
 794                                 $this->connLogger->warning( "Failed to connect to database $i at '$serverName'." );
 795                                 $this->errorConnection = $conn;
 796                                 $conn = false;
 797                         }
 798                 }
 799
 800                 if ( $conn instanceof IDatabase && !$conn->isOpen() ) {
 801                         // Connection was made but later unrecoverably lost for some reason.
 802                         // Do not return a handle that will just throw exceptions on use,
 803                         // but let the calling code (e.g. getReaderIndex) try another server.
 804                         // See DatabaseMyslBase::ping() for how this can happen.
 805                         $this->errorConnection = $conn;
 806                         $conn = false;
 807                 }
 808
 809                 return $conn;
 810         }
 811
 812         /**
 813          * Open a connection to a foreign DB, or return one if it is already open.
 814          *
 815          * Increments a reference count on the returned connection which locks the
 816          * connection to the requested domain. This reference count can be
 817          * decremented by calling reuseConnection().
 818          *
 819          * If a connection is open to the appropriate server already, but with the wrong
 820          * database, it will be switched to the right database and returned, as long as
 821          * it has been freed first with reuseConnection().
 822          *
 823          * On error, returns false, and the connection which caused the
 824          * error will be available via $this->errorConnection.
 825          *
 826          * @note If disable() was called on this LoadBalancer, this method will throw a DBAccessError.
 827          *
 828          * @param int $i Server index
 829          * @param string $domain Domain ID to open
 830          * @return Database
 831          */
 832         private function openForeignConnection( $i, $domain ) {
 833                 $domainInstance = DatabaseDomain::newFromId( $domain );
 834                 $dbName = $domainInstance->getDatabase();
 835                 $prefix = $domainInstance->getTablePrefix();
 836
 837                 if ( isset( $this->mConns[self::KEY_FOREIGN_INUSE][$i][$domain] ) ) {
 838                         // Reuse an in-use connection for the same domain that is not in-use
 839                         $conn = $this->mConns[self::KEY_FOREIGN_INUSE][$i][$domain];
 840                         $this->connLogger->debug( __METHOD__ . ": reusing connection $i/$domain" );
 841                 } elseif ( isset( $this->mConns[self::KEY_FOREIGN_FREE][$i][$domain] ) ) {
 842                         // Reuse a free connection for the same domain that is not in-use
 843                         $conn = $this->mConns[self::KEY_FOREIGN_FREE][$i][$domain];
 844                         unset( $this->mConns[self::KEY_FOREIGN_FREE][$i][$domain] );
 845                         $this->mConns[self::KEY_FOREIGN_INUSE][$i][$domain] = $conn;
 846                         $this->connLogger->debug( __METHOD__ . ": reusing free connection $i/$domain" );
 847                 } elseif ( !empty( $this->mConns[self::KEY_FOREIGN_FREE][$i] ) ) {
 848                         // Reuse a connection from another domain
 849                         $conn = reset( $this->mConns[self::KEY_FOREIGN_FREE][$i] );
 850                         $oldDomain = key( $this->mConns[self::KEY_FOREIGN_FREE][$i] );
 851                         // The empty string as a DB name means "don't care".
 852                         // DatabaseMysqlBase::open() already handle this on connection.
 853                         if ( strlen( $dbName ) && !$conn->selectDB( $dbName ) ) {
 854                                 $this->mLastError = "Error selecting database '$dbName' on server " .
 855                                         $conn->getServer() . " from client host {$this->host}";
 856                                 $this->errorConnection = $conn;
 857                                 $conn = false;
 858                         } else {
 859                                 $conn->tablePrefix( $prefix );
 860                                 unset( $this->mConns[self::KEY_FOREIGN_FREE][$i][$oldDomain] );
 861                                 $this->mConns[self::KEY_FOREIGN_INUSE][$i][$domain] = $conn;
 862                                 $this->connLogger->debug( __METHOD__ .
 863                                         ": reusing free connection from $oldDomain for $domain" );
 864                         }
 865                 } else {
 866                         if ( !isset( $this->mServers[$i] ) || !is_array( $this->mServers[$i] ) ) {
 867                                 throw new InvalidArgumentException( "No server with index '$i'." );
 868                         }
 869                         // Open a new connection
 870                         $server = $this->mServers[$i];
 871                         $server['serverIndex'] = $i;
 872                         $server['foreignPoolRefCount'] = 0;
 873                         $server['foreign'] = true;
 874                         $conn = $this->reallyOpenConnection( $server, $dbName );
 875                         if ( !$conn->isOpen() ) {
 876                                 $this->connLogger->warning( __METHOD__ . ": connection error for $i/$domain" );
 877                                 $this->errorConnection = $conn;
 878                                 $conn = false;
 879                         } else {
 880                                 $conn->tablePrefix( $prefix );
 881                                 $this->mConns[self::KEY_FOREIGN_INUSE][$i][$domain] = $conn;
 882                                 $this->connLogger->debug( __METHOD__ . ": opened new connection for $i/$domain" );
 883                         }
 884                 }
 885
 886                 // Increment reference count
 887                 if ( $conn instanceof IDatabase ) {
 888                         $refCount = $conn->getLBInfo( 'foreignPoolRefCount' );
 889                         $conn->setLBInfo( 'foreignPoolRefCount', $refCount + 1 );
 890                 }
 891
 892                 return $conn;
 893         }
 894
 895         /**
 896          * Test if the specified index represents an open connection
 897          *
 898          * @param int $index Server index
 899          * @access private
 900          * @return bool
 901          */
 902         private function isOpen( $index ) {
 903                 if ( !is_integer( $index ) ) {
 904                         return false;
 905                 }
 906
 907                 return (bool)$this->getAnyOpenConnection( $index );
 908         }
 909
 910         /**
 911          * Really opens a connection. Uncached.
 912          * Returns a Database object whether or not the connection was successful.
 913          * @access private
 914          *
 915          * @param array $server
 916          * @param string|bool $dbNameOverride Use "" to not select any database
 917          * @return Database
 918          * @throws DBAccessError
 919          * @throws InvalidArgumentException
 920          */
 921         protected function reallyOpenConnection( array $server, $dbNameOverride = false ) {
 922                 if ( $this->disabled ) {
 923                         throw new DBAccessError();
 924                 }
 925
 926                 if ( $dbNameOverride !== false ) {
 927                         $server['dbname'] = $dbNameOverride;
 928                 }
 929
 930                 // Let the handle know what the cluster master is (e.g. "db1052")
 931                 $masterName = $this->getServerName( $this->getWriterIndex() );
 932                 $server['clusterMasterHost'] = $masterName;
 933
 934                 // Log when many connection are made on requests
 935                 if ( ++$this->connsOpened >= self::CONN_HELD_WARN_THRESHOLD ) {
 936                         $this->perfLogger->warning( __METHOD__ . ": " .
 937                                 "{$this->connsOpened}+ connections made (master=$masterName)" );
 938                 }
 939
 940                 $server['srvCache'] = $this->srvCache;
 941                 // Set loggers and profilers
 942                 $server['connLogger'] = $this->connLogger;
 943                 $server['queryLogger'] = $this->queryLogger;
 944                 $server['errorLogger'] = $this->errorLogger;
 945                 $server['profiler'] = $this->profiler;
 946                 $server['trxProfiler'] = $this->trxProfiler;
 947                 // Use the same agent and PHP mode for all DB handles
 948                 $server['cliMode'] = $this->cliMode;
 949                 $server['agent'] = $this->agent;
 950                 // Use DBO_DEFAULT flags by default for LoadBalancer managed databases. Assume that the
 951                 // application calls LoadBalancer::commitMasterChanges() before the PHP script completes.
 952                 $server['flags'] = isset( $server['flags'] ) ? $server['flags'] : IDatabase::DBO_DEFAULT;
 953
 954                 // Create a live connection object
 955                 try {
 956                         $db = Database::factory( $server['type'], $server );
 957                 } catch ( DBConnectionError $e ) {
 958                         // FIXME: This is probably the ugliest thing I have ever done to
 959                         // PHP. I'm half-expecting it to segfault, just out of disgust. -- TS
 960                         $db = $e->db;
 961                 }
 962
 963                 $db->setLBInfo( $server );
 964                 $db->setLazyMasterHandle(
 965                         $this->getLazyConnectionRef( self::DB_MASTER, [], $db->getDomainID() )
 966                 );
 967                 $db->setTableAliases( $this->tableAliases );
 968
 969                 if ( $server['serverIndex'] === $this->getWriterIndex() ) {
 970                         if ( $this->trxRoundId !== false ) {
 971                                 $this->applyTransactionRoundFlags( $db );
 972                         }
 973                         foreach ( $this->trxRecurringCallbacks as $name => $callback ) {
 974                                 $db->setTransactionListener( $name, $callback );
 975                         }
 976                 }
 977
 978                 return $db;
 979         }
 980
 981         /**
 982          * @throws DBConnectionError
 983          */
 984         private function reportConnectionError() {
 985                 $conn = $this->errorConnection; // the connection which caused the error
 986                 $context = [
 987                         'method' => __METHOD__,
 988                         'last_error' => $this->mLastError,
 989                 ];
 990
 991                 if ( $conn instanceof IDatabase ) {
 992                         $context['db_server'] = $conn->getServer();
 993                         $this->connLogger->warning(
 994                                 "Connection error: {last_error} ({db_server})",
 995                                 $context
 996                         );
 997
 998                         // throws DBConnectionError
 999                         $conn->reportConnectionError( "{$this->mLastError} ({$context['db_server']})" );
1000                 } else {
1001                         // No last connection, probably due to all servers being too busy
1002                         $this->connLogger->error(
1003                                 "LB failure with no last connection. Connection error: {last_error}",
1004                                 $context
1005                         );
1006
1007                         // If all servers were busy, mLastError will contain something sensible
1008                         throw new DBConnectionError( null, $this->mLastError );
1009                 }
1010         }
1011
1012         public function getWriterIndex() {
1013                 return 0;
1014         }
1015
1016         public function haveIndex( $i ) {
1017                 return array_key_exists( $i, $this->mServers );
1018         }
1019
1020         public function isNonZeroLoad( $i ) {
1021                 return array_key_exists( $i, $this->mServers ) && $this->mLoads[$i] != 0;
1022         }
1023
1024         public function getServerCount() {
1025                 return count( $this->mServers );
1026         }
1027
1028         public function getServerName( $i ) {
1029                 if ( isset( $this->mServers[$i]['hostName'] ) ) {
1030                         $name = $this->mServers[$i]['hostName'];
1031                 } elseif ( isset( $this->mServers[$i]['host'] ) ) {
1032                         $name = $this->mServers[$i]['host'];
1033                 } else {
1034                         $name = '';
1035                 }
1036
1037                 return ( $name != '' ) ? $name : 'localhost';
1038         }
1039
1040         /**
1041          * @deprecated Since 1.30, no alternative
1042          */
1043         public function getServerInfo( $i ) {
1044                 wfDeprecated( __METHOD__, '1.30' );
1045                 if ( isset( $this->mServers[$i] ) ) {
1046                         return $this->mServers[$i];
1047                 } else {
1048                         return false;
1049                 }
1050         }
1051
1052         /**
1053          * @deprecated Since 1.30, construct new object
1054          */
1055         public function setServerInfo( $i, array $serverInfo ) {
1056                 wfDeprecated( __METHOD__, '1.30' );
1057                 $this->mServers[$i] = $serverInfo;
1058         }
1059
1060         public function getMasterPos() {
1061                 # If this entire request was served from a replica DB without opening a connection to the
1062                 # master (however unlikely that may be), then we can fetch the position from the replica DB.
1063                 $masterConn = $this->getAnyOpenConnection( $this->getWriterIndex() );
1064                 if ( !$masterConn ) {
1065                         $serverCount = count( $this->mServers );
1066                         for ( $i = 1; $i < $serverCount; $i++ ) {
1067                                 $conn = $this->getAnyOpenConnection( $i );
1068                                 if ( $conn ) {
1069                                         return $conn->getReplicaPos();
1070                                 }
1071                         }
1072                 } else {
1073                         return $masterConn->getMasterPos();
1074                 }
1075
1076                 return false;
1077         }
1078
1079         public function disable() {
1080                 $this->closeAll();
1081                 $this->disabled = true;
1082         }
1083
1084         public function closeAll() {
1085                 $this->forEachOpenConnection( function ( IDatabase $conn ) {
1086                         $host = $conn->getServer();
1087                         $this->connLogger->debug( "Closing connection to database '$host'." );
1088                         $conn->close();
1089                 } );
1090
1091                 $this->mConns = [
1092                         self::KEY_LOCAL => [],
1093                         self::KEY_FOREIGN_FREE => [],
1094                         self::KEY_FOREIGN_INUSE => [],
1095                 ];
1096                 $this->connsOpened = 0;
1097         }
1098
1099         public function closeConnection( IDatabase $conn ) {
1100                 $serverIndex = $conn->getLBInfo( 'serverIndex' ); // second index level of mConns
1101                 foreach ( $this->mConns as $type => $connsByServer ) {
1102                         if ( !isset( $connsByServer[$serverIndex] ) ) {
1103                                 continue;
1104                         }
1105
1106                         foreach ( $connsByServer[$serverIndex] as $i => $trackedConn ) {
1107                                 if ( $conn === $trackedConn ) {
1108                                         $host = $this->getServerName( $i );
1109                                         $this->connLogger->debug( "Closing connection to database $i at '$host'." );
1110                                         unset( $this->mConns[$type][$serverIndex][$i] );
1111                                         --$this->connsOpened;
1112                                         break 2;
1113                                 }
1114                         }
1115                 }
1116
1117                 $conn->close();
1118         }
1119
1120         public function commitAll( $fname = __METHOD__ ) {
1121                 $failures = [];
1122
1123                 $restore = ( $this->trxRoundId !== false );
1124                 $this->trxRoundId = false;
1125                 $this->forEachOpenConnection(
1126                         function ( IDatabase $conn ) use ( $fname, $restore, &$failures ) {
1127                                 try {
1128                                         $conn->commit( $fname, $conn::FLUSHING_ALL_PEERS );
1129                                 } catch ( DBError $e ) {
1130                                         call_user_func( $this->errorLogger, $e );
1131                                         $failures[] = "{$conn->getServer()}: {$e->getMessage()}";
1132                                 }
1133                                 if ( $restore && $conn->getLBInfo( 'master' ) ) {
1134                                         $this->undoTransactionRoundFlags( $conn );
1135                                 }
1136                         }
1137                 );
1138
1139                 if ( $failures ) {
1140                         throw new DBExpectedError(
1141                                 null,
1142                                 "Commit failed on server(s) " . implode( "\n", array_unique( $failures ) )
1143                         );
1144                 }
1145         }
1146
1147         public function finalizeMasterChanges() {
1148                 $this->forEachOpenMasterConnection( function ( Database $conn ) {
1149                         // Any error should cause all DB transactions to be rolled back together
1150                         $conn->setTrxEndCallbackSuppression( false );
1151                         $conn->runOnTransactionPreCommitCallbacks();
1152                         // Defer post-commit callbacks until COMMIT finishes for all DBs
1153                         $conn->setTrxEndCallbackSuppression( true );
1154                 } );
1155         }
1156
1157         public function approveMasterChanges( array $options ) {
1158                 $limit = isset( $options['maxWriteDuration'] ) ? $options['maxWriteDuration'] : 0;
1159                 $this->forEachOpenMasterConnection( function ( IDatabase $conn ) use ( $limit ) {
1160                         // If atomic sections or explicit transactions are still open, some caller must have
1161                         // caught an exception but failed to properly rollback any changes. Detect that and
1162                         // throw and error (causing rollback).
1163                         if ( $conn->explicitTrxActive() ) {
1164                                 throw new DBTransactionError(
1165                                         $conn,
1166                                         "Explicit transaction still active. A caller may have caught an error."
1167                                 );
1168                         }
1169                         // Assert that the time to replicate the transaction will be sane.
1170                         // If this fails, then all DB transactions will be rollback back together.
1171                         $time = $conn->pendingWriteQueryDuration( $conn::ESTIMATE_DB_APPLY );
1172                         if ( $limit > 0 && $time > $limit ) {
1173                                 throw new DBTransactionSizeError(
1174                                         $conn,
1175                                         "Transaction spent $time second(s) in writes, exceeding the $limit limit.",
1176                                         [ $time, $limit ]
1177                                 );
1178                         }
1179                         // If a connection sits idle while slow queries execute on another, that connection
1180                         // may end up dropped before the commit round is reached. Ping servers to detect this.
1181                         if ( $conn->writesOrCallbacksPending() && !$conn->ping() ) {
1182                                 throw new DBTransactionError(
1183                                         $conn,
1184                                         "A connection to the {$conn->getDBname()} database was lost before commit."
1185                                 );
1186                         }
1187                 } );
1188         }
1189
1190         public function beginMasterChanges( $fname = __METHOD__ ) {
1191                 if ( $this->trxRoundId !== false ) {
1192                         throw new DBTransactionError(
1193                                 null,
1194                                 "$fname: Transaction round '{$this->trxRoundId}' already started."
1195                         );
1196                 }
1197                 $this->trxRoundId = $fname;
1198
1199                 $failures = [];
1200                 $this->forEachOpenMasterConnection(
1201                         function ( Database $conn ) use ( $fname, &$failures ) {
1202                                 $conn->setTrxEndCallbackSuppression( true );
1203                                 try {
1204                                         $conn->flushSnapshot( $fname );
1205                                 } catch ( DBError $e ) {
1206                                         call_user_func( $this->errorLogger, $e );
1207                                         $failures[] = "{$conn->getServer()}: {$e->getMessage()}";
1208                                 }
1209                                 $conn->setTrxEndCallbackSuppression( false );
1210                                 $this->applyTransactionRoundFlags( $conn );
1211                         }
1212                 );
1213
1214                 if ( $failures ) {
1215                         throw new DBExpectedError(
1216                                 null,
1217                                 "$fname: Flush failed on server(s) " . implode( "\n", array_unique( $failures ) )
1218                         );
1219                 }
1220         }
1221
1222         public function commitMasterChanges( $fname = __METHOD__ ) {
1223                 $failures = [];
1224
1225                 /** @noinspection PhpUnusedLocalVariableInspection */
1226                 $scope = $this->getScopedPHPBehaviorForCommit(); // try to ignore client aborts
1227
1228                 $restore = ( $this->trxRoundId !== false );
1229                 $this->trxRoundId = false;
1230                 $this->forEachOpenMasterConnection(
1231                         function ( IDatabase $conn ) use ( $fname, $restore, &$failures ) {
1232                                 try {
1233                                         if ( $conn->writesOrCallbacksPending() ) {
1234                                                 $conn->commit( $fname, $conn::FLUSHING_ALL_PEERS );
1235                                         } elseif ( $restore ) {
1236                                                 $conn->flushSnapshot( $fname );
1237                                         }
1238                                 } catch ( DBError $e ) {
1239                                         call_user_func( $this->errorLogger, $e );
1240                                         $failures[] = "{$conn->getServer()}: {$e->getMessage()}";
1241                                 }
1242                                 if ( $restore ) {
1243                                         $this->undoTransactionRoundFlags( $conn );
1244                                 }
1245                         }
1246                 );
1247
1248                 if ( $failures ) {
1249                         throw new DBExpectedError(
1250                                 null,
1251                                 "$fname: Commit failed on server(s) " . implode( "\n", array_unique( $failures ) )
1252                         );
1253                 }
1254         }
1255
1256         public function runMasterPostTrxCallbacks( $type ) {
1257                 $e = null; // first exception
1258                 $this->forEachOpenMasterConnection( function ( Database $conn ) use ( $type, &$e ) {
1259                         $conn->setTrxEndCallbackSuppression( false );
1260                         if ( $conn->writesOrCallbacksPending() ) {
1261                                 // This happens if onTransactionIdle() callbacks leave callbacks on *another* DB
1262                                 // (which finished its callbacks already). Warn and recover in this case. Let the
1263                                 // callbacks run in the final commitMasterChanges() in LBFactory::shutdown().
1264                                 $this->queryLogger->info( __METHOD__ . ": found writes/callbacks pending." );
1265                                 return;
1266                         } elseif ( $conn->trxLevel() ) {
1267                                 // This happens for single-DB setups where DB_REPLICA uses the master DB,
1268                                 // thus leaving an implicit read-only transaction open at this point. It
1269                                 // also happens if onTransactionIdle() callbacks leave implicit transactions
1270                                 // open on *other* DBs (which is slightly improper). Let these COMMIT on the
1271                                 // next call to commitMasterChanges(), possibly in LBFactory::shutdown().
1272                                 return;
1273                         }
1274                         try {
1275                                 $conn->runOnTransactionIdleCallbacks( $type );
1276                         } catch ( Exception $ex ) {
1277                                 $e = $e ?: $ex;
1278                         }
1279                         try {
1280                                 $conn->runTransactionListenerCallbacks( $type );
1281                         } catch ( Exception $ex ) {
1282                                 $e = $e ?: $ex;
1283                         }
1284                 } );
1285
1286                 return $e;
1287         }
1288
1289         public function rollbackMasterChanges( $fname = __METHOD__ ) {
1290                 $restore = ( $this->trxRoundId !== false );
1291                 $this->trxRoundId = false;
1292                 $this->forEachOpenMasterConnection(
1293                         function ( IDatabase $conn ) use ( $fname, $restore ) {
1294                                 if ( $conn->writesOrCallbacksPending() ) {
1295                                         $conn->rollback( $fname, $conn::FLUSHING_ALL_PEERS );
1296                                 }
1297                                 if ( $restore ) {
1298                                         $this->undoTransactionRoundFlags( $conn );
1299                                 }
1300                         }
1301                 );
1302         }
1303
1304         public function suppressTransactionEndCallbacks() {
1305                 $this->forEachOpenMasterConnection( function ( Database $conn ) {
1306                         $conn->setTrxEndCallbackSuppression( true );
1307                 } );
1308         }
1309
1310         /**
1311          * @param IDatabase $conn
1312          */
1313         private function applyTransactionRoundFlags( IDatabase $conn ) {
1314                 if ( $conn->getFlag( $conn::DBO_DEFAULT ) ) {
1315                         // DBO_TRX is controlled entirely by CLI mode presence with DBO_DEFAULT.
1316                         // Force DBO_TRX even in CLI mode since a commit round is expected soon.
1317                         $conn->setFlag( $conn::DBO_TRX, $conn::REMEMBER_PRIOR );
1318                         // If config has explicitly requested DBO_TRX be either on or off by not
1319                         // setting DBO_DEFAULT, then respect that. Forcing no transactions is useful
1320                         // for things like blob stores (ExternalStore) which want auto-commit mode.
1321                 }
1322         }
1323
1324         /**
1325          * @param IDatabase $conn
1326          */
1327         private function undoTransactionRoundFlags( IDatabase $conn ) {
1328                 if ( $conn->getFlag( $conn::DBO_DEFAULT ) ) {
1329                         $conn->restoreFlags( $conn::RESTORE_PRIOR );
1330                 }
1331         }
1332
1333         public function flushReplicaSnapshots( $fname = __METHOD__ ) {
1334                 $this->forEachOpenReplicaConnection( function ( IDatabase $conn ) {
1335                         $conn->flushSnapshot( __METHOD__ );
1336                 } );
1337         }
1338
1339         public function hasMasterConnection() {
1340                 return $this->isOpen( $this->getWriterIndex() );
1341         }
1342
1343         public function hasMasterChanges() {
1344                 $pending = 0;
1345                 $this->forEachOpenMasterConnection( function ( IDatabase $conn ) use ( &$pending ) {
1346                         $pending |= $conn->writesOrCallbacksPending();
1347                 } );
1348
1349                 return (bool)$pending;
1350         }
1351
1352         public function lastMasterChangeTimestamp() {
1353                 $lastTime = false;
1354                 $this->forEachOpenMasterConnection( function ( IDatabase $conn ) use ( &$lastTime ) {
1355                         $lastTime = max( $lastTime, $conn->lastDoneWrites() );
1356                 } );
1357
1358                 return $lastTime;
1359         }
1360
1361         public function hasOrMadeRecentMasterChanges( $age = null ) {
1362                 $age = ( $age === null ) ? $this->mWaitTimeout : $age;
1363
1364                 return ( $this->hasMasterChanges()
1365                         || $this->lastMasterChangeTimestamp() > microtime( true ) - $age );
1366         }
1367
1368         public function pendingMasterChangeCallers() {
1369                 $fnames = [];
1370                 $this->forEachOpenMasterConnection( function ( IDatabase $conn ) use ( &$fnames ) {
1371                         $fnames = array_merge( $fnames, $conn->pendingWriteCallers() );
1372                 } );
1373
1374                 return $fnames;
1375         }
1376
1377         public function getLaggedReplicaMode( $domain = false ) {
1378                 // No-op if there is only one DB (also avoids recursion)
1379                 if ( !$this->laggedReplicaMode && $this->getServerCount() > 1 ) {
1380                         try {
1381                                 // See if laggedReplicaMode gets set
1382                                 $conn = $this->getConnection( self::DB_REPLICA, false, $domain );
1383                                 $this->reuseConnection( $conn );
1384                         } catch ( DBConnectionError $e ) {
1385                                 // Avoid expensive re-connect attempts and failures
1386                                 $this->allReplicasDownMode = true;
1387                                 $this->laggedReplicaMode = true;
1388                         }
1389                 }
1390
1391                 return $this->laggedReplicaMode;
1392         }
1393
1394         /**
1395          * @param bool $domain
1396          * @return bool
1397          * @deprecated 1.28; use getLaggedReplicaMode()
1398          */
1399         public function getLaggedSlaveMode( $domain = false ) {
1400                 return $this->getLaggedReplicaMode( $domain );
1401         }
1402
1403         public function laggedReplicaUsed() {
1404                 return $this->laggedReplicaMode;
1405         }
1406
1407         /**
1408          * @return bool
1409          * @since 1.27
1410          * @deprecated Since 1.28; use laggedReplicaUsed()
1411          */
1412         public function laggedSlaveUsed() {
1413                 return $this->laggedReplicaUsed();
1414         }
1415
1416         public function getReadOnlyReason( $domain = false, IDatabase $conn = null ) {
1417                 if ( $this->readOnlyReason !== false ) {
1418                         return $this->readOnlyReason;
1419                 } elseif ( $this->getLaggedReplicaMode( $domain ) ) {
1420                         if ( $this->allReplicasDownMode ) {
1421                                 return 'The database has been automatically locked ' .
1422                                         'until the replica database servers become available';
1423                         } else {
1424                                 return 'The database has been automatically locked ' .
1425                                         'while the replica database servers catch up to the master.';
1426                         }
1427                 } elseif ( $this->masterRunningReadOnly( $domain, $conn ) ) {
1428                         return 'The database master is running in read-only mode.';
1429                 }
1430
1431                 return false;
1432         }
1433
1434         /**
1435          * @param string $domain Domain ID, or false for the current domain
1436          * @param IDatabase|null $conn DB master connectionl used to avoid loops [optional]
1437          * @return bool
1438          */
1439         private function masterRunningReadOnly( $domain, IDatabase $conn = null ) {
1440                 $cache = $this->wanCache;
1441                 $masterServer = $this->getServerName( $this->getWriterIndex() );
1442
1443                 return (bool)$cache->getWithSetCallback(
1444                         $cache->makeGlobalKey( __CLASS__, 'server-read-only', $masterServer ),
1445                         self::TTL_CACHE_READONLY,
1446                         function () use ( $domain, $conn ) {
1447                                 $old = $this->trxProfiler->setSilenced( true );
1448                                 try {
1449                                         $dbw = $conn ?: $this->getConnection( self::DB_MASTER, [], $domain );
1450                                         $readOnly = (int)$dbw->serverIsReadOnly();
1451                                         if ( !$conn ) {
1452                                                 $this->reuseConnection( $dbw );
1453                                         }
1454                                 } catch ( DBError $e ) {
1455                                         $readOnly = 0;
1456                                 }
1457                                 $this->trxProfiler->setSilenced( $old );
1458                                 return $readOnly;
1459                         },
1460                         [ 'pcTTL' => $cache::TTL_PROC_LONG, 'busyValue' => 0 ]
1461                 );
1462         }
1463
1464         public function allowLagged( $mode = null ) {
1465                 if ( $mode === null ) {
1466                         return $this->mAllowLagged;
1467                 }
1468                 $this->mAllowLagged = $mode;
1469
1470                 return $this->mAllowLagged;
1471         }
1472
1473         public function pingAll() {
1474                 $success = true;
1475                 $this->forEachOpenConnection( function ( IDatabase $conn ) use ( &$success ) {
1476                         if ( !$conn->ping() ) {
1477                                 $success = false;
1478                         }
1479                 } );
1480
1481                 return $success;
1482         }
1483
1484         public function forEachOpenConnection( $callback, array $params = [] ) {
1485                 foreach ( $this->mConns as $connsByServer ) {
1486                         foreach ( $connsByServer as $serverConns ) {
1487                                 foreach ( $serverConns as $conn ) {
1488                                         $mergedParams = array_merge( [ $conn ], $params );
1489                                         call_user_func_array( $callback, $mergedParams );
1490                                 }
1491                         }
1492                 }
1493         }
1494
1495         public function forEachOpenMasterConnection( $callback, array $params = [] ) {
1496                 $masterIndex = $this->getWriterIndex();
1497                 foreach ( $this->mConns as $connsByServer ) {
1498                         if ( isset( $connsByServer[$masterIndex] ) ) {
1499                                 /** @var IDatabase $conn */
1500                                 foreach ( $connsByServer[$masterIndex] as $conn ) {
1501                                         $mergedParams = array_merge( [ $conn ], $params );
1502                                         call_user_func_array( $callback, $mergedParams );
1503                                 }
1504                         }
1505                 }
1506         }
1507
1508         public function forEachOpenReplicaConnection( $callback, array $params = [] ) {
1509                 foreach ( $this->mConns as $connsByServer ) {
1510                         foreach ( $connsByServer as $i => $serverConns ) {
1511                                 if ( $i === $this->getWriterIndex() ) {
1512                                         continue; // skip master
1513                                 }
1514                                 foreach ( $serverConns as $conn ) {
1515                                         $mergedParams = array_merge( [ $conn ], $params );
1516                                         call_user_func_array( $callback, $mergedParams );
1517                                 }
1518                         }
1519                 }
1520         }
1521
1522         public function getMaxLag( $domain = false ) {
1523                 $maxLag = -1;
1524                 $host = '';
1525                 $maxIndex = 0;
1526
1527                 if ( $this->getServerCount() <= 1 ) {
1528                         return [ $host, $maxLag, $maxIndex ]; // no replication = no lag
1529                 }
1530
1531                 $lagTimes = $this->getLagTimes( $domain );
1532                 foreach ( $lagTimes as $i => $lag ) {
1533                         if ( $this->mLoads[$i] > 0 && $lag > $maxLag ) {
1534                                 $maxLag = $lag;
1535                                 $host = $this->mServers[$i]['host'];
1536                                 $maxIndex = $i;
1537                         }
1538                 }
1539
1540                 return [ $host, $maxLag, $maxIndex ];
1541         }
1542
1543         public function getLagTimes( $domain = false ) {
1544                 if ( $this->getServerCount() <= 1 ) {
1545                         return [ $this->getWriterIndex() => 0 ]; // no replication = no lag
1546                 }
1547
1548                 $knownLagTimes = []; // map of (server index => 0 seconds)
1549                 $indexesWithLag = [];
1550                 foreach ( $this->mServers as $i => $server ) {
1551                         if ( empty( $server['is static'] ) ) {
1552                                 $indexesWithLag[] = $i; // DB server might have replication lag
1553                         } else {
1554                                 $knownLagTimes[$i] = 0; // DB server is a non-replicating and read-only archive
1555                         }
1556                 }
1557
1558                 return $this->getLoadMonitor()->getLagTimes( $indexesWithLag, $domain ) + $knownLagTimes;
1559         }
1560
1561         public function safeGetLag( IDatabase $conn ) {
1562                 if ( $this->getServerCount() <= 1 ) {
1563                         return 0;
1564                 } else {
1565                         return $conn->getLag();
1566                 }
1567         }
1568
1569         /**
1570          * @param IDatabase $conn
1571          * @param DBMasterPos|bool $pos
1572          * @param int $timeout
1573          * @return bool
1574          */
1575         public function safeWaitForMasterPos( IDatabase $conn, $pos = false, $timeout = 10 ) {
1576                 if ( $this->getServerCount() <= 1 || !$conn->getLBInfo( 'replica' ) ) {
1577                         return true; // server is not a replica DB
1578                 }
1579
1580                 if ( !$pos ) {
1581                         // Get the current master position, opening a connection if needed
1582                         $masterConn = $this->getAnyOpenConnection( $this->getWriterIndex() );
1583                         if ( $masterConn ) {
1584                                 $pos = $masterConn->getMasterPos();
1585                         } else {
1586                                 $masterConn = $this->openConnection( $this->getWriterIndex(), self::DOMAIN_ANY );
1587                                 $pos = $masterConn->getMasterPos();
1588                                 $this->closeConnection( $masterConn );
1589                         }
1590                 }
1591
1592                 if ( $pos instanceof DBMasterPos ) {
1593                         $result = $conn->masterPosWait( $pos, $timeout );
1594                         if ( $result == -1 || is_null( $result ) ) {
1595                                 $msg = __METHOD__ . ": Timed out waiting on {$conn->getServer()} pos {$pos}";
1596                                 $this->replLogger->warning( "$msg" );
1597                                 $ok = false;
1598                         } else {
1599                                 $this->replLogger->info( __METHOD__ . ": Done" );
1600                                 $ok = true;
1601                         }
1602                 } else {
1603                         $ok = false; // something is misconfigured
1604                         $this->replLogger->error( "Could not get master pos for {$conn->getServer()}." );
1605                 }
1606
1607                 return $ok;
1608         }
1609
1610         public function setTransactionListener( $name, callable $callback = null ) {
1611                 if ( $callback ) {
1612                         $this->trxRecurringCallbacks[$name] = $callback;
1613                 } else {
1614                         unset( $this->trxRecurringCallbacks[$name] );
1615                 }
1616                 $this->forEachOpenMasterConnection(
1617                         function ( IDatabase $conn ) use ( $name, $callback ) {
1618                                 $conn->setTransactionListener( $name, $callback );
1619                         }
1620                 );
1621         }
1622
1623         public function setTableAliases( array $aliases ) {
1624                 $this->tableAliases = $aliases;
1625         }
1626
1627         public function setDomainPrefix( $prefix ) {
1628                 // Find connections to explicit foreign domains still marked as in-use...
1629                 $domainsInUse = [];
1630                 $this->forEachOpenConnection( function ( IDatabase $conn ) use ( &$domainsInUse ) {
1631                         // Once reuseConnection() is called on a handle, its reference count goes from 1 to 0.
1632                         // Until then, it is still in use by the caller (explicitly or via DBConnRef scope).
1633                         if ( $conn->getLBInfo( 'foreignPoolRefCount' ) > 0 ) {
1634                                 $domainsInUse[] = $conn->getDomainID();
1635                         }
1636                 } );
1637
1638                 // Do not switch connections to explicit foreign domains unless marked as safe
1639                 if ( $domainsInUse ) {
1640                         $domains = implode( ', ', $domainsInUse );
1641                         throw new DBUnexpectedError( null,
1642                                 "Foreign domain connections are still in use ($domains)." );
1643                 }
1644
1645                 $this->localDomain = new DatabaseDomain(
1646                         $this->localDomain->getDatabase(),
1647                         null,
1648                         $prefix
1649                 );
1650
1651                 $this->forEachOpenConnection( function ( IDatabase $db ) use ( $prefix ) {
1652                         $db->tablePrefix( $prefix );
1653                 } );
1654         }
1655
1656         /**
1657          * Make PHP ignore user aborts/disconnects until the returned
1658          * value leaves scope. This returns null and does nothing in CLI mode.
1659          *
1660          * @return ScopedCallback|null
1661          */
1662         final protected function getScopedPHPBehaviorForCommit() {
1663                 if ( PHP_SAPI != 'cli' ) { // https://bugs.php.net/bug.php?id=47540
1664                         $old = ignore_user_abort( true ); // avoid half-finished operations
1665                         return new ScopedCallback( function () use ( $old ) {
1666                                 ignore_user_abort( $old );
1667                         } );
1668                 }
1669
1670                 return null;
1671         }
1672
1673         function __destruct() {
1674                 // Avoid connection leaks for sanity
1675                 $this->disable();
1676         }
1677 }
1678
1679 class_alias( LoadBalancer::class, 'LoadBalancer' );