includes/libs/rdbms/lbfactory/LBFactory.php

   1 <?php
   2 /**
   3  * Generator and manager of database load balancing objects
   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
  24 namespace Wikimedia\Rdbms;
  25
  26 use Psr\Log\LoggerInterface;
  27 use Psr\Log\NullLogger;
  28 use Wikimedia\ScopedCallback;
  29 use BagOStuff;
  30 use EmptyBagOStuff;
  31 use WANObjectCache;
  32 use Exception;
  33 use RuntimeException;
  34 use LogicException;
  35
  36 /**
  37  * An interface for generating database load balancers
  38  * @ingroup Database
  39  */
  40 abstract class LBFactory implements ILBFactory {
  41         /** @var ChronologyProtector */
  42         private $chronProt;
  43         /** @var object|string Class name or object With profileIn/profileOut methods */
  44         private $profiler;
  45         /** @var TransactionProfiler */
  46         private $trxProfiler;
  47         /** @var LoggerInterface */
  48         private $replLogger;
  49         /** @var LoggerInterface */
  50         private $connLogger;
  51         /** @var LoggerInterface */
  52         private $queryLogger;
  53         /** @var LoggerInterface */
  54         private $perfLogger;
  55         /** @var callable Error logger */
  56         private $errorLogger;
  57         /** @var callable Deprecation logger */
  58         private $deprecationLogger;
  59
  60         /** @var BagOStuff */
  61         protected $srvCache;
  62         /** @var BagOStuff */
  63         protected $memStash;
  64         /** @var WANObjectCache */
  65         protected $wanCache;
  66
  67         /** @var DatabaseDomain Local domain */
  68         protected $localDomain;
  69
  70         /** @var string Local hostname of the app server */
  71         private $hostname;
  72         /** @var array Web request information about the client */
  73         private $requestInfo;
  74         /** @var bool Whether this PHP instance is for a CLI script */
  75         private $cliMode;
  76         /** @var string Agent name for query profiling */
  77         private $agent;
  78         /** @var string Secret string for HMAC hashing */
  79         private $secret;
  80
  81         /** @var array[] $aliases Map of (table => (dbname, schema, prefix) map) */
  82         private $tableAliases = [];
  83         /** @var string[] Map of (index alias => index) */
  84         private $indexAliases = [];
  85         /** @var callable[] */
  86         private $replicationWaitCallbacks = [];
  87
  88         /** var int An identifier for this class instance */
  89         private $id;
  90         /** @var int|null Ticket used to delegate transaction ownership */
  91         private $ticket;
  92         /** @var string|bool String if a requested DBO_TRX transaction round is active */
  93         private $trxRoundId = false;
  94         /** @var string One of the ROUND_* class constants */
  95         private $trxRoundStage = self::ROUND_CURSORY;
  96
  97         /** @var string|bool Reason all LBs are read-only or false if not */
  98         protected $readOnlyReason = false;
  99
 100         /** @var string|null */
 101         private $defaultGroup = null;
 102
 103         /** @var int|null */
 104         protected $maxLag;
 105
 106         const ROUND_CURSORY = 'cursory';
 107         const ROUND_BEGINNING = 'within-begin';
 108         const ROUND_COMMITTING = 'within-commit';
 109         const ROUND_ROLLING_BACK = 'within-rollback';
 110         const ROUND_COMMIT_CALLBACKS = 'within-commit-callbacks';
 111         const ROUND_ROLLBACK_CALLBACKS = 'within-rollback-callbacks';
 112
 113         private static $loggerFields =
 114                 [ 'replLogger', 'connLogger', 'queryLogger', 'perfLogger' ];
 115
 116         public function __construct( array $conf ) {
 117                 $this->localDomain = isset( $conf['localDomain'] )
 118                         ? DatabaseDomain::newFromId( $conf['localDomain'] )
 119                         : DatabaseDomain::newUnspecified();
 120
 121                 $this->maxLag = $conf['maxLag'] ?? null;
 122                 if ( isset( $conf['readOnlyReason'] ) && is_string( $conf['readOnlyReason'] ) ) {
 123                         $this->readOnlyReason = $conf['readOnlyReason'];
 124                 }
 125
 126                 $this->srvCache = $conf['srvCache'] ?? new EmptyBagOStuff();
 127                 $this->memStash = $conf['memStash'] ?? new EmptyBagOStuff();
 128                 $this->wanCache = $conf['wanCache'] ?? WANObjectCache::newEmpty();
 129
 130                 foreach ( self::$loggerFields as $key ) {
 131                         $this->$key = $conf[$key] ?? new NullLogger();
 132                 }
 133                 $this->errorLogger = $conf['errorLogger'] ?? function ( Exception $e ) {
 134                         trigger_error( get_class( $e ) . ': ' . $e->getMessage(), E_USER_WARNING );
 135                 };
 136                 $this->deprecationLogger = $conf['deprecationLogger'] ?? function ( $msg ) {
 137                         trigger_error( $msg, E_USER_DEPRECATED );
 138                 };
 139
 140                 $this->profiler = $conf['profiler'] ?? null;
 141                 $this->trxProfiler = $conf['trxProfiler'] ?? new TransactionProfiler();
 142
 143                 $this->requestInfo = [
 144                         'IPAddress' => $_SERVER[ 'REMOTE_ADDR' ] ?? '',
 145                         'UserAgent' => $_SERVER['HTTP_USER_AGENT'] ?? '',
 146                         // Headers application can inject via LBFactory::setRequestInfo()
 147                         'ChronologyProtection' => null,
 148                         'ChronologyClientId' => null, // prior $cpClientId value from LBFactory::shutdown()
 149                         'ChronologyPositionIndex' => null // prior $cpIndex value from LBFactory::shutdown()
 150                 ];
 151
 152                 $this->cliMode = $conf['cliMode'] ?? ( PHP_SAPI === 'cli' || PHP_SAPI === 'phpdbg' );
 153                 $this->hostname = $conf['hostname'] ?? gethostname();
 154                 $this->agent = $conf['agent'] ?? '';
 155                 $this->defaultGroup = $conf['defaultGroup'] ?? null;
 156                 $this->secret = $conf['secret'] ?? '';
 157
 158                 static $nextId, $nextTicket;
 159                 $this->id = $nextId = ( is_int( $nextId ) ? $nextId++ : mt_rand() );
 160                 $this->ticket = $nextTicket = ( is_int( $nextTicket ) ? $nextTicket++ : mt_rand() );
 161         }
 162
 163         public function destroy() {
 164                 $this->shutdown( self::SHUTDOWN_NO_CHRONPROT );
 165                 $this->forEachLBCallMethod( 'disable' );
 166         }
 167
 168         public function getLocalDomainID() {
 169                 return $this->localDomain->getId();
 170         }
 171
 172         public function resolveDomainID( $domain ) {
 173                 return ( $domain !== false ) ? (string)$domain : $this->getLocalDomainID();
 174         }
 175
 176         public function shutdown(
 177                 $mode = self::SHUTDOWN_CHRONPROT_SYNC,
 178                 callable $workCallback = null,
 179                 &$cpIndex = null,
 180                 &$cpClientId = null
 181         ) {
 182                 $chronProt = $this->getChronologyProtector();
 183                 if ( $mode === self::SHUTDOWN_CHRONPROT_SYNC ) {
 184                         $this->shutdownChronologyProtector( $chronProt, $workCallback, 'sync', $cpIndex );
 185                 } elseif ( $mode === self::SHUTDOWN_CHRONPROT_ASYNC ) {
 186                         $this->shutdownChronologyProtector( $chronProt, null, 'async', $cpIndex );
 187                 }
 188
 189                 $cpClientId = $chronProt->getClientId();
 190
 191                 $this->commitMasterChanges( __METHOD__ ); // sanity
 192         }
 193
 194         /**
 195          * @see ILBFactory::newMainLB()
 196          * @param bool $domain
 197          * @return ILoadBalancer
 198          */
 199         abstract public function newMainLB( $domain = false );
 200
 201         /**
 202          * @see ILBFactory::getMainLB()
 203          * @param bool $domain
 204          * @return ILoadBalancer
 205          */
 206         abstract public function getMainLB( $domain = false );
 207
 208         /**
 209          * @see ILBFactory::newExternalLB()
 210          * @param string $cluster
 211          * @return ILoadBalancer
 212          */
 213         abstract public function newExternalLB( $cluster );
 214
 215         /**
 216          * @see ILBFactory::getExternalLB()
 217          * @param string $cluster
 218          * @return ILoadBalancer
 219          */
 220         abstract public function getExternalLB( $cluster );
 221
 222         /**
 223          * Call a method of each tracked load balancer
 224          *
 225          * @param string $methodName
 226          * @param array $args
 227          */
 228         protected function forEachLBCallMethod( $methodName, array $args = [] ) {
 229                 $this->forEachLB(
 230                         function ( ILoadBalancer $loadBalancer, $methodName, array $args ) {
 231                                 $loadBalancer->$methodName( ...$args );
 232                         },
 233                         [ $methodName, $args ]
 234                 );
 235         }
 236
 237         public function flushReplicaSnapshots( $fname = __METHOD__ ) {
 238                 if ( $this->trxRoundId !== false && $this->trxRoundId !== $fname ) {
 239                         $this->queryLogger->warning(
 240                                 "$fname: transaction round '{$this->trxRoundId}' still running",
 241                                 [ 'trace' => ( new RuntimeException() )->getTraceAsString() ]
 242                         );
 243                 }
 244                 $this->forEachLBCallMethod( 'flushReplicaSnapshots', [ $fname ] );
 245         }
 246
 247         final public function commitAll( $fname = __METHOD__, array $options = [] ) {
 248                 $this->commitMasterChanges( $fname, $options );
 249                 $this->forEachLBCallMethod( 'flushMasterSnapshots', [ $fname ] );
 250                 $this->forEachLBCallMethod( 'flushReplicaSnapshots', [ $fname ] );
 251         }
 252
 253         final public function beginMasterChanges( $fname = __METHOD__ ) {
 254                 $this->assertTransactionRoundStage( self::ROUND_CURSORY );
 255                 $this->trxRoundStage = self::ROUND_BEGINNING;
 256                 if ( $this->trxRoundId !== false ) {
 257                         throw new DBTransactionError(
 258                                 null,
 259                                 "$fname: transaction round '{$this->trxRoundId}' already started"
 260                         );
 261                 }
 262                 $this->trxRoundId = $fname;
 263                 // Set DBO_TRX flags on all appropriate DBs
 264                 $this->forEachLBCallMethod( 'beginMasterChanges', [ $fname, $this->id ] );
 265                 $this->trxRoundStage = self::ROUND_CURSORY;
 266         }
 267
 268         final public function commitMasterChanges( $fname = __METHOD__, array $options = [] ) {
 269                 $this->assertTransactionRoundStage( self::ROUND_CURSORY );
 270                 $this->trxRoundStage = self::ROUND_COMMITTING;
 271                 if ( $this->trxRoundId !== false && $this->trxRoundId !== $fname ) {
 272                         throw new DBTransactionError(
 273                                 null,
 274                                 "$fname: transaction round '{$this->trxRoundId}' still running"
 275                         );
 276                 }
 277                 /** @noinspection PhpUnusedLocalVariableInspection */
 278                 $scope = ScopedCallback::newScopedIgnoreUserAbort(); // try to ignore client aborts
 279                 // Run pre-commit callbacks and suppress post-commit callbacks, aborting on failure
 280                 do {
 281                         $count = 0; // number of callbacks executed this iteration
 282                         $this->forEachLB( function ( ILoadBalancer $lb ) use ( &$count, $fname ) {
 283                                 $count += $lb->finalizeMasterChanges( $fname, $this->id );
 284                         } );
 285                 } while ( $count > 0 );
 286                 $this->trxRoundId = false;
 287                 // Perform pre-commit checks, aborting on failure
 288                 $this->forEachLBCallMethod( 'approveMasterChanges', [ $options, $fname, $this->id ] );
 289                 // Log the DBs and methods involved in multi-DB transactions
 290                 $this->logIfMultiDbTransaction();
 291                 // Actually perform the commit on all master DB connections and revert DBO_TRX
 292                 $this->forEachLBCallMethod( 'commitMasterChanges', [ $fname, $this->id ] );
 293                 // Run all post-commit callbacks in a separate step
 294                 $this->trxRoundStage = self::ROUND_COMMIT_CALLBACKS;
 295                 $e = $this->executePostTransactionCallbacks();
 296                 $this->trxRoundStage = self::ROUND_CURSORY;
 297                 // Throw any last post-commit callback error
 298                 if ( $e instanceof Exception ) {
 299                         throw $e;
 300                 }
 301         }
 302
 303         final public function rollbackMasterChanges( $fname = __METHOD__ ) {
 304                 $this->trxRoundStage = self::ROUND_ROLLING_BACK;
 305                 $this->trxRoundId = false;
 306                 // Actually perform the rollback on all master DB connections and revert DBO_TRX
 307                 $this->forEachLBCallMethod( 'rollbackMasterChanges', [ $fname, $this->id ] );
 308                 // Run all post-commit callbacks in a separate step
 309                 $this->trxRoundStage = self::ROUND_ROLLBACK_CALLBACKS;
 310                 $this->executePostTransactionCallbacks();
 311                 $this->trxRoundStage = self::ROUND_CURSORY;
 312         }
 313
 314         /**
 315          * @return Exception|null
 316          */
 317         private function executePostTransactionCallbacks() {
 318                 $fname = __METHOD__;
 319                 // Run all post-commit callbacks until new ones stop getting added
 320                 $e = null; // first callback exception
 321                 do {
 322                         $this->forEachLB( function ( ILoadBalancer $lb ) use ( &$e, $fname ) {
 323                                 $ex = $lb->runMasterTransactionIdleCallbacks( $fname, $this->id );
 324                                 $e = $e ?: $ex;
 325                         } );
 326                 } while ( $this->hasMasterChanges() );
 327                 // Run all listener callbacks once
 328                 $this->forEachLB( function ( ILoadBalancer $lb ) use ( &$e, $fname ) {
 329                         $ex = $lb->runMasterTransactionListenerCallbacks( $fname, $this->id );
 330                         $e = $e ?: $ex;
 331                 } );
 332
 333                 return $e;
 334         }
 335
 336         public function hasTransactionRound() {
 337                 return ( $this->trxRoundId !== false );
 338         }
 339
 340         public function isReadyForRoundOperations() {
 341                 return ( $this->trxRoundStage === self::ROUND_CURSORY );
 342         }
 343
 344         /**
 345          * Log query info if multi DB transactions are going to be committed now
 346          */
 347         private function logIfMultiDbTransaction() {
 348                 $callersByDB = [];
 349                 $this->forEachLB( function ( ILoadBalancer $lb ) use ( &$callersByDB ) {
 350                         $masterName = $lb->getServerName( $lb->getWriterIndex() );
 351                         $callers = $lb->pendingMasterChangeCallers();
 352                         if ( $callers ) {
 353                                 $callersByDB[$masterName] = $callers;
 354                         }
 355                 } );
 356
 357                 if ( count( $callersByDB ) >= 2 ) {
 358                         $dbs = implode( ', ', array_keys( $callersByDB ) );
 359                         $msg = "Multi-DB transaction [{$dbs}]:\n";
 360                         foreach ( $callersByDB as $db => $callers ) {
 361                                 $msg .= "$db: " . implode( '; ', $callers ) . "\n";
 362                         }
 363                         $this->queryLogger->info( $msg );
 364                 }
 365         }
 366
 367         public function hasMasterChanges() {
 368                 $ret = false;
 369                 $this->forEachLB( function ( ILoadBalancer $lb ) use ( &$ret ) {
 370                         $ret = $ret || $lb->hasMasterChanges();
 371                 } );
 372
 373                 return $ret;
 374         }
 375
 376         public function laggedReplicaUsed() {
 377                 $ret = false;
 378                 $this->forEachLB( function ( ILoadBalancer $lb ) use ( &$ret ) {
 379                         $ret = $ret || $lb->laggedReplicaUsed();
 380                 } );
 381
 382                 return $ret;
 383         }
 384
 385         public function hasOrMadeRecentMasterChanges( $age = null ) {
 386                 $ret = false;
 387                 $this->forEachLB( function ( ILoadBalancer $lb ) use ( $age, &$ret ) {
 388                         $ret = $ret || $lb->hasOrMadeRecentMasterChanges( $age );
 389                 } );
 390                 return $ret;
 391         }
 392
 393         public function waitForReplication( array $opts = [] ) {
 394                 $opts += [
 395                         'domain' => false,
 396                         'cluster' => false,
 397                         'timeout' => $this->cliMode ? 60 : 1,
 398                         'ifWritesSince' => null
 399                 ];
 400
 401                 if ( $opts['domain'] === false && isset( $opts['wiki'] ) ) {
 402                         $opts['domain'] = $opts['wiki']; // b/c
 403                 }
 404
 405                 // Figure out which clusters need to be checked
 406                 /** @var ILoadBalancer[] $lbs */
 407                 $lbs = [];
 408                 if ( $opts['cluster'] !== false ) {
 409                         $lbs[] = $this->getExternalLB( $opts['cluster'] );
 410                 } elseif ( $opts['domain'] !== false ) {
 411                         $lbs[] = $this->getMainLB( $opts['domain'] );
 412                 } else {
 413                         $this->forEachLB( function ( ILoadBalancer $lb ) use ( &$lbs ) {
 414                                 $lbs[] = $lb;
 415                         } );
 416                         if ( !$lbs ) {
 417                                 return true; // nothing actually used
 418                         }
 419                 }
 420
 421                 // Get all the master positions of applicable DBs right now.
 422                 // This can be faster since waiting on one cluster reduces the
 423                 // time needed to wait on the next clusters.
 424                 $masterPositions = array_fill( 0, count( $lbs ), false );
 425                 foreach ( $lbs as $i => $lb ) {
 426                         if (
 427                                 // No writes to wait on getting replicated
 428                                 !$lb->hasMasterConnection() ||
 429                                 // No replication; avoid getMasterPos() permissions errors (T29975)
 430                                 !$lb->hasStreamingReplicaServers() ||
 431                                 // No writes since the last replication wait
 432                                 (
 433                                         $opts['ifWritesSince'] &&
 434                                         $lb->lastMasterChangeTimestamp() < $opts['ifWritesSince']
 435                                 )
 436                         ) {
 437                                 continue; // no need to wait
 438                         }
 439
 440                         $masterPositions[$i] = $lb->getMasterPos();
 441                 }
 442
 443                 // Run any listener callbacks *after* getting the DB positions. The more
 444                 // time spent in the callbacks, the less time is spent in waitForAll().
 445                 foreach ( $this->replicationWaitCallbacks as $callback ) {
 446                         $callback();
 447                 }
 448
 449                 $failed = [];
 450                 foreach ( $lbs as $i => $lb ) {
 451                         if ( $masterPositions[$i] ) {
 452                                 // The RDBMS may not support getMasterPos()
 453                                 if ( !$lb->waitForAll( $masterPositions[$i], $opts['timeout'] ) ) {
 454                                         $failed[] = $lb->getServerName( $lb->getWriterIndex() );
 455                                 }
 456                         }
 457                 }
 458
 459                 return !$failed;
 460         }
 461
 462         public function setWaitForReplicationListener( $name, callable $callback = null ) {
 463                 if ( $callback ) {
 464                         $this->replicationWaitCallbacks[$name] = $callback;
 465                 } else {
 466                         unset( $this->replicationWaitCallbacks[$name] );
 467                 }
 468         }
 469
 470         public function getEmptyTransactionTicket( $fname ) {
 471                 if ( $this->hasMasterChanges() ) {
 472                         $this->queryLogger->error(
 473                                 __METHOD__ . ": $fname does not have outer scope",
 474                                 [ 'trace' => ( new RuntimeException() )->getTraceAsString() ]
 475                         );
 476
 477                         return null;
 478                 }
 479
 480                 return $this->ticket;
 481         }
 482
 483         final public function commitAndWaitForReplication( $fname, $ticket, array $opts = [] ) {
 484                 if ( $ticket !== $this->ticket ) {
 485                         $this->perfLogger->error(
 486                                 __METHOD__ . ": $fname does not have outer scope",
 487                                 [ 'trace' => ( new RuntimeException() )->getTraceAsString() ]
 488                         );
 489
 490                         return false;
 491                 }
 492
 493                 // The transaction owner and any caller with the empty transaction ticket can commit
 494                 // so that getEmptyTransactionTicket() callers don't risk seeing DBTransactionError.
 495                 if ( $this->trxRoundId !== false && $fname !== $this->trxRoundId ) {
 496                         $this->queryLogger->info( "$fname: committing on behalf of {$this->trxRoundId}" );
 497                         $fnameEffective = $this->trxRoundId;
 498                 } else {
 499                         $fnameEffective = $fname;
 500                 }
 501
 502                 $this->commitMasterChanges( $fnameEffective );
 503                 $waitSucceeded = $this->waitForReplication( $opts );
 504                 // If a nested caller committed on behalf of $fname, start another empty $fname
 505                 // transaction, leaving the caller with the same empty transaction state as before.
 506                 if ( $fnameEffective !== $fname ) {
 507                         $this->beginMasterChanges( $fnameEffective );
 508                 }
 509
 510                 return $waitSucceeded;
 511         }
 512
 513         public function getChronologyProtectorTouched( $dbName ) {
 514                 return $this->getChronologyProtector()->getTouched( $dbName );
 515         }
 516
 517         public function disableChronologyProtection() {
 518                 $this->getChronologyProtector()->setEnabled( false );
 519         }
 520
 521         /**
 522          * @return ChronologyProtector
 523          */
 524         protected function getChronologyProtector() {
 525                 if ( $this->chronProt ) {
 526                         return $this->chronProt;
 527                 }
 528
 529                 $this->chronProt = new ChronologyProtector(
 530                         $this->memStash,
 531                         [
 532                                 'ip' => $this->requestInfo['IPAddress'],
 533                                 'agent' => $this->requestInfo['UserAgent'],
 534                                 'clientId' => $this->requestInfo['ChronologyClientId'] ?: null
 535                         ],
 536                         $this->requestInfo['ChronologyPositionIndex'],
 537                         $this->secret
 538                 );
 539                 $this->chronProt->setLogger( $this->replLogger );
 540
 541                 if ( $this->cliMode ) {
 542                         $this->chronProt->setEnabled( false );
 543                 } elseif ( $this->requestInfo['ChronologyProtection'] === 'false' ) {
 544                         // Request opted out of using position wait logic. This is useful for requests
 545                         // done by the job queue or background ETL that do not have a meaningful session.
 546                         $this->chronProt->setWaitEnabled( false );
 547                 } elseif ( $this->memStash instanceof EmptyBagOStuff ) {
 548                         // No where to store any DB positions and wait for them to appear
 549                         $this->chronProt->setEnabled( false );
 550                         $this->replLogger->info( 'Cannot use ChronologyProtector with EmptyBagOStuff' );
 551                 }
 552
 553                 $this->replLogger->debug(
 554                         __METHOD__ . ': request info ' .
 555                         json_encode( $this->requestInfo, JSON_PRETTY_PRINT )
 556                 );
 557
 558                 return $this->chronProt;
 559         }
 560
 561         /**
 562          * Get and record all of the staged DB positions into persistent memory storage
 563          *
 564          * @param ChronologyProtector $cp
 565          * @param callable|null $workCallback Work to do instead of waiting on syncing positions
 566          * @param string $mode One of (sync, async); whether to wait on remote datacenters
 567          * @param int|null &$cpIndex DB position key write counter; incremented on update
 568          */
 569         protected function shutdownChronologyProtector(
 570                 ChronologyProtector $cp, $workCallback, $mode, &$cpIndex = null
 571         ) {
 572                 // Record all the master positions needed
 573                 $this->forEachLB( function ( ILoadBalancer $lb ) use ( $cp ) {
 574                         $cp->storeSessionReplicationPosition( $lb );
 575                 } );
 576                 // Write them to the persistent stash. Try to do something useful by running $work
 577                 // while ChronologyProtector waits for the stash write to replicate to all DCs.
 578                 $unsavedPositions = $cp->shutdown( $workCallback, $mode, $cpIndex );
 579                 if ( $unsavedPositions && $workCallback ) {
 580                         // Invoke callback in case it did not cache the result yet
 581                         $workCallback(); // work now to block for less time in waitForAll()
 582                 }
 583                 // If the positions failed to write to the stash, at least wait on local datacenter
 584                 // replica DBs to catch up before responding. Even if there are several DCs, this increases
 585                 // the chance that the user will see their own changes immediately afterwards. As long
 586                 // as the sticky DC cookie applies (same domain), this is not even an issue.
 587                 $this->forEachLB( function ( ILoadBalancer $lb ) use ( $unsavedPositions ) {
 588                         $masterName = $lb->getServerName( $lb->getWriterIndex() );
 589                         if ( isset( $unsavedPositions[$masterName] ) ) {
 590                                 $lb->waitForAll( $unsavedPositions[$masterName] );
 591                         }
 592                 } );
 593         }
 594
 595         /**
 596          * Base parameters to ILoadBalancer::__construct()
 597          * @return array
 598          */
 599         final protected function baseLoadBalancerParams() {
 600                 if ( $this->trxRoundStage === self::ROUND_COMMIT_CALLBACKS ) {
 601                         $initStage = ILoadBalancer::STAGE_POSTCOMMIT_CALLBACKS;
 602                 } elseif ( $this->trxRoundStage === self::ROUND_ROLLBACK_CALLBACKS ) {
 603                         $initStage = ILoadBalancer::STAGE_POSTROLLBACK_CALLBACKS;
 604                 } else {
 605                         $initStage = null;
 606                 }
 607
 608                 return [
 609                         'localDomain' => $this->localDomain,
 610                         'readOnlyReason' => $this->readOnlyReason,
 611                         'srvCache' => $this->srvCache,
 612                         'wanCache' => $this->wanCache,
 613                         'profiler' => $this->profiler,
 614                         'trxProfiler' => $this->trxProfiler,
 615                         'queryLogger' => $this->queryLogger,
 616                         'connLogger' => $this->connLogger,
 617                         'replLogger' => $this->replLogger,
 618                         'errorLogger' => $this->errorLogger,
 619                         'deprecationLogger' => $this->deprecationLogger,
 620                         'hostname' => $this->hostname,
 621                         'cliMode' => $this->cliMode,
 622                         'agent' => $this->agent,
 623                         'maxLag' => $this->maxLag,
 624                         'defaultGroup' => $this->defaultGroup,
 625                         'chronologyCallback' => function ( ILoadBalancer $lb ) {
 626                                 // Defer ChronologyProtector construction in case setRequestInfo() ends up
 627                                 // being called later (but before the first connection attempt) (T192611)
 628                                 $this->getChronologyProtector()->applySessionReplicationPosition( $lb );
 629                         },
 630                         'roundStage' => $initStage,
 631                         'ownerId' => $this->id
 632                 ];
 633         }
 634
 635         /**
 636          * @param ILoadBalancer $lb
 637          */
 638         protected function initLoadBalancer( ILoadBalancer $lb ) {
 639                 if ( $this->trxRoundId !== false ) {
 640                         $lb->beginMasterChanges( $this->trxRoundId, $this->id ); // set DBO_TRX
 641                 }
 642
 643                 $lb->setTableAliases( $this->tableAliases );
 644                 $lb->setIndexAliases( $this->indexAliases );
 645         }
 646
 647         public function setTableAliases( array $aliases ) {
 648                 $this->tableAliases = $aliases;
 649         }
 650
 651         public function setIndexAliases( array $aliases ) {
 652                 $this->indexAliases = $aliases;
 653         }
 654
 655         public function setLocalDomainPrefix( $prefix ) {
 656                 $this->localDomain = new DatabaseDomain(
 657                         $this->localDomain->getDatabase(),
 658                         $this->localDomain->getSchema(),
 659                         $prefix
 660                 );
 661
 662                 $this->forEachLB( function ( ILoadBalancer $lb ) use ( $prefix ) {
 663                         $lb->setLocalDomainPrefix( $prefix );
 664                 } );
 665         }
 666
 667         public function redefineLocalDomain( $domain ) {
 668                 $this->closeAll();
 669
 670                 $this->localDomain = DatabaseDomain::newFromId( $domain );
 671
 672                 $this->forEachLB( function ( ILoadBalancer $lb ) {
 673                         $lb->redefineLocalDomain( $this->localDomain );
 674                 } );
 675         }
 676
 677         public function closeAll() {
 678                 $this->forEachLBCallMethod( 'closeAll' );
 679         }
 680
 681         public function setAgentName( $agent ) {
 682                 $this->agent = $agent;
 683         }
 684
 685         public function appendShutdownCPIndexAsQuery( $url, $index ) {
 686                 $usedCluster = 0;
 687                 $this->forEachLB( function ( ILoadBalancer $lb ) use ( &$usedCluster ) {
 688                         $usedCluster |= $lb->hasStreamingReplicaServers();
 689                 } );
 690
 691                 if ( !$usedCluster ) {
 692                         return $url; // no master/replica clusters touched
 693                 }
 694
 695                 return strpos( $url, '?' ) === false ? "$url?cpPosIndex=$index" : "$url&cpPosIndex=$index";
 696         }
 697
 698         public function getChronologyProtectorClientId() {
 699                 return $this->getChronologyProtector()->getClientId();
 700         }
 701
 702         /**
 703          * @param int $index Write index
 704          * @param int $time UNIX timestamp; can be used to detect stale cookies (T190082)
 705          * @param string $clientId Agent ID hash from ILBFactory::shutdown()
 706          * @return string Timestamp-qualified write index of the form "<index>@<timestamp>#<hash>"
 707          * @since 1.32
 708          */
 709         public static function makeCookieValueFromCPIndex( $index, $time, $clientId ) {
 710                 return "$index@$time#$clientId";
 711         }
 712
 713         /**
 714          * @param string $value Possible result of LBFactory::makeCookieValueFromCPIndex()
 715          * @param int $minTimestamp Lowest UNIX timestamp that a non-expired value can have
 716          * @return array (index: int or null, clientId: string or null)
 717          * @since 1.32
 718          */
 719         public static function getCPInfoFromCookieValue( $value, $minTimestamp ) {
 720                 static $placeholder = [ 'index' => null, 'clientId' => null ];
 721
 722                 if ( !preg_match( '/^(\d+)@(\d+)#([0-9a-f]{32})$/', $value, $m ) ) {
 723                         return $placeholder; // invalid
 724                 }
 725
 726                 $index = (int)$m[1];
 727                 if ( $index <= 0 ) {
 728                         return $placeholder; // invalid
 729                 } elseif ( isset( $m[2] ) && $m[2] !== '' && (int)$m[2] < $minTimestamp ) {
 730                         return $placeholder; // expired
 731                 }
 732
 733                 $clientId = ( isset( $m[3] ) && $m[3] !== '' ) ? $m[3] : null;
 734
 735                 return [ 'index' => $index, 'clientId' => $clientId ];
 736         }
 737
 738         public function setRequestInfo( array $info ) {
 739                 if ( $this->chronProt ) {
 740                         throw new LogicException( 'ChronologyProtector already initialized' );
 741                 }
 742
 743                 $this->requestInfo = $info + $this->requestInfo;
 744         }
 745
 746         /**
 747          * @param string $stage
 748          */
 749         private function assertTransactionRoundStage( $stage ) {
 750                 if ( $this->trxRoundStage !== $stage ) {
 751                         throw new DBTransactionError(
 752                                 null,
 753                                 "Transaction round stage must be '$stage' (not '{$this->trxRoundStage}')"
 754                         );
 755                 }
 756         }
 757
 758         function __destruct() {
 759                 $this->destroy();
 760         }
 761 }