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 Wikimedia\ScopedCallback;
  28 use BagOStuff;
  29 use EmptyBagOStuff;
  30 use WANObjectCache;
  31 use Exception;
  32 use RuntimeException;
  33
  34 /**
  35  * An interface for generating database load balancers
  36  * @ingroup Database
  37  */
  38 abstract class LBFactory implements ILBFactory {
  39         /** @var ChronologyProtector */
  40         protected $chronProt;
  41         /** @var object|string Class name or object With profileIn/profileOut methods */
  42         protected $profiler;
  43         /** @var TransactionProfiler */
  44         protected $trxProfiler;
  45         /** @var LoggerInterface */
  46         protected $replLogger;
  47         /** @var LoggerInterface */
  48         protected $connLogger;
  49         /** @var LoggerInterface */
  50         protected $queryLogger;
  51         /** @var LoggerInterface */
  52         protected $perfLogger;
  53         /** @var callable Error logger */
  54         protected $errorLogger;
  55         /** @var BagOStuff */
  56         protected $srvCache;
  57         /** @var BagOStuff */
  58         protected $memStash;
  59         /** @var WANObjectCache */
  60         protected $wanCache;
  61
  62         /** @var DatabaseDomain Local domain */
  63         protected $localDomain;
  64         /** @var string Local hostname of the app server */
  65         protected $hostname;
  66         /** @var array Web request information about the client */
  67         protected $requestInfo;
  68
  69         /** @var mixed */
  70         protected $ticket;
  71         /** @var string|bool String if a requested DBO_TRX transaction round is active */
  72         protected $trxRoundId = false;
  73         /** @var string|bool Reason all LBs are read-only or false if not */
  74         protected $readOnlyReason = false;
  75         /** @var callable[] */
  76         protected $replicationWaitCallbacks = [];
  77
  78         /** @var array[] $aliases Map of (table => (dbname, schema, prefix) map) */
  79         protected $tableAliases = [];
  80         /** @var string[] Map of (index alias => index) */
  81         protected $indexAliases = [];
  82
  83         /** @var bool Whether this PHP instance is for a CLI script */
  84         protected $cliMode;
  85         /** @var string Agent name for query profiling */
  86         protected $agent;
  87
  88         private static $loggerFields =
  89                 [ 'replLogger', 'connLogger', 'queryLogger', 'perfLogger' ];
  90
  91         public function __construct( array $conf ) {
  92                 $this->localDomain = isset( $conf['localDomain'] )
  93                         ? DatabaseDomain::newFromId( $conf['localDomain'] )
  94                         : DatabaseDomain::newUnspecified();
  95
  96                 if ( isset( $conf['readOnlyReason'] ) && is_string( $conf['readOnlyReason'] ) ) {
  97                         $this->readOnlyReason = $conf['readOnlyReason'];
  98                 }
  99
 100                 $this->srvCache = isset( $conf['srvCache'] ) ? $conf['srvCache'] : new EmptyBagOStuff();
 101                 $this->memStash = isset( $conf['memStash'] ) ? $conf['memStash'] : new EmptyBagOStuff();
 102                 $this->wanCache = isset( $conf['wanCache'] )
 103                         ? $conf['wanCache']
 104                         : WANObjectCache::newEmpty();
 105
 106                 foreach ( self::$loggerFields as $key ) {
 107                         $this->$key = isset( $conf[$key] ) ? $conf[$key] : new \Psr\Log\NullLogger();
 108                 }
 109                 $this->errorLogger = isset( $conf['errorLogger'] )
 110                         ? $conf['errorLogger']
 111                         : function ( Exception $e ) {
 112                                 trigger_error( E_USER_WARNING, get_class( $e ) . ': ' . $e->getMessage() );
 113                         };
 114
 115                 $this->profiler = isset( $conf['profiler'] ) ? $conf['profiler'] : null;
 116                 $this->trxProfiler = isset( $conf['trxProfiler'] )
 117                         ? $conf['trxProfiler']
 118                         : new TransactionProfiler();
 119
 120                 $this->requestInfo = [
 121                         'IPAddress' => isset( $_SERVER[ 'REMOTE_ADDR' ] ) ? $_SERVER[ 'REMOTE_ADDR' ] : '',
 122                         'UserAgent' => isset( $_SERVER['HTTP_USER_AGENT'] ) ? $_SERVER['HTTP_USER_AGENT'] : '',
 123                         'ChronologyProtection' => 'true',
 124                         'ChronologyPositionIndex' => isset( $_GET['cpPosIndex'] ) ? $_GET['cpPosIndex'] : null
 125                 ];
 126
 127                 $this->cliMode = isset( $conf['cliMode'] ) ? $conf['cliMode'] : PHP_SAPI === 'cli';
 128                 $this->hostname = isset( $conf['hostname'] ) ? $conf['hostname'] : gethostname();
 129                 $this->agent = isset( $conf['agent'] ) ? $conf['agent'] : '';
 130
 131                 $this->ticket = mt_rand();
 132         }
 133
 134         public function destroy() {
 135                 $this->shutdown( self::SHUTDOWN_NO_CHRONPROT );
 136                 $this->forEachLBCallMethod( 'disable' );
 137         }
 138
 139         public function shutdown(
 140                 $mode = self::SHUTDOWN_CHRONPROT_SYNC, callable $workCallback = null, &$cpIndex = null
 141         ) {
 142                 $chronProt = $this->getChronologyProtector();
 143                 if ( $mode === self::SHUTDOWN_CHRONPROT_SYNC ) {
 144                         $this->shutdownChronologyProtector( $chronProt, $workCallback, 'sync', $cpIndex );
 145                 } elseif ( $mode === self::SHUTDOWN_CHRONPROT_ASYNC ) {
 146                         $this->shutdownChronologyProtector( $chronProt, null, 'async', $cpIndex );
 147                 }
 148
 149                 $this->commitMasterChanges( __METHOD__ ); // sanity
 150         }
 151
 152         /**
 153          * @see ILBFactory::newMainLB()
 154          * @param bool $domain
 155          * @return LoadBalancer
 156          */
 157         abstract public function newMainLB( $domain = false );
 158
 159         /**
 160          * @see ILBFactory::getMainLB()
 161          * @param bool $domain
 162          * @return LoadBalancer
 163          */
 164         abstract public function getMainLB( $domain = false );
 165
 166         /**
 167          * @see ILBFactory::newExternalLB()
 168          * @param string $cluster
 169          * @return LoadBalancer
 170          */
 171         abstract public function newExternalLB( $cluster );
 172
 173         /**
 174          * @see ILBFactory::getExternalLB()
 175          * @param string $cluster
 176          * @return LoadBalancer
 177          */
 178         abstract public function getExternalLB( $cluster );
 179
 180         /**
 181          * Call a method of each tracked load balancer
 182          *
 183          * @param string $methodName
 184          * @param array $args
 185          */
 186         protected function forEachLBCallMethod( $methodName, array $args = [] ) {
 187                 $this->forEachLB(
 188                         function ( ILoadBalancer $loadBalancer, $methodName, array $args ) {
 189                                 call_user_func_array( [ $loadBalancer, $methodName ], $args );
 190                         },
 191                         [ $methodName, $args ]
 192                 );
 193         }
 194
 195         public function flushReplicaSnapshots( $fname = __METHOD__ ) {
 196                 $this->forEachLBCallMethod( 'flushReplicaSnapshots', [ $fname ] );
 197         }
 198
 199         public function commitAll( $fname = __METHOD__, array $options = [] ) {
 200                 $this->commitMasterChanges( $fname, $options );
 201                 $this->forEachLBCallMethod( 'commitAll', [ $fname ] );
 202         }
 203
 204         public function beginMasterChanges( $fname = __METHOD__ ) {
 205                 if ( $this->trxRoundId !== false ) {
 206                         throw new DBTransactionError(
 207                                 null,
 208                                 "$fname: transaction round '{$this->trxRoundId}' already started."
 209                         );
 210                 }
 211                 $this->trxRoundId = $fname;
 212                 // Set DBO_TRX flags on all appropriate DBs
 213                 $this->forEachLBCallMethod( 'beginMasterChanges', [ $fname ] );
 214         }
 215
 216         public function commitMasterChanges( $fname = __METHOD__, array $options = [] ) {
 217                 if ( $this->trxRoundId !== false && $this->trxRoundId !== $fname ) {
 218                         throw new DBTransactionError(
 219                                 null,
 220                                 "$fname: transaction round '{$this->trxRoundId}' still running."
 221                         );
 222                 }
 223                 /** @noinspection PhpUnusedLocalVariableInspection */
 224                 $scope = $this->getScopedPHPBehaviorForCommit(); // try to ignore client aborts
 225                 // Run pre-commit callbacks and suppress post-commit callbacks, aborting on failure
 226                 $this->forEachLBCallMethod( 'finalizeMasterChanges' );
 227                 $this->trxRoundId = false;
 228                 // Perform pre-commit checks, aborting on failure
 229                 $this->forEachLBCallMethod( 'approveMasterChanges', [ $options ] );
 230                 // Log the DBs and methods involved in multi-DB transactions
 231                 $this->logIfMultiDbTransaction();
 232                 // Actually perform the commit on all master DB connections and revert DBO_TRX
 233                 $this->forEachLBCallMethod( 'commitMasterChanges', [ $fname ] );
 234                 // Run all post-commit callbacks
 235                 /** @var Exception $e */
 236                 $e = null; // first callback exception
 237                 $this->forEachLB( function ( ILoadBalancer $lb ) use ( &$e ) {
 238                         $ex = $lb->runMasterPostTrxCallbacks( IDatabase::TRIGGER_COMMIT );
 239                         $e = $e ?: $ex;
 240                 } );
 241                 // Commit any dangling DBO_TRX transactions from callbacks on one DB to another DB
 242                 $this->forEachLBCallMethod( 'commitMasterChanges', [ $fname ] );
 243                 // Throw any last post-commit callback error
 244                 if ( $e instanceof Exception ) {
 245                         throw $e;
 246                 }
 247         }
 248
 249         public function rollbackMasterChanges( $fname = __METHOD__ ) {
 250                 $this->trxRoundId = false;
 251                 $this->forEachLBCallMethod( 'suppressTransactionEndCallbacks' );
 252                 $this->forEachLBCallMethod( 'rollbackMasterChanges', [ $fname ] );
 253                 // Run all post-rollback callbacks
 254                 $this->forEachLB( function ( ILoadBalancer $lb ) {
 255                         $lb->runMasterPostTrxCallbacks( IDatabase::TRIGGER_ROLLBACK );
 256                 } );
 257         }
 258
 259         public function hasTransactionRound() {
 260                 return ( $this->trxRoundId !== false );
 261         }
 262
 263         /**
 264          * Log query info if multi DB transactions are going to be committed now
 265          */
 266         private function logIfMultiDbTransaction() {
 267                 $callersByDB = [];
 268                 $this->forEachLB( function ( ILoadBalancer $lb ) use ( &$callersByDB ) {
 269                         $masterName = $lb->getServerName( $lb->getWriterIndex() );
 270                         $callers = $lb->pendingMasterChangeCallers();
 271                         if ( $callers ) {
 272                                 $callersByDB[$masterName] = $callers;
 273                         }
 274                 } );
 275
 276                 if ( count( $callersByDB ) >= 2 ) {
 277                         $dbs = implode( ', ', array_keys( $callersByDB ) );
 278                         $msg = "Multi-DB transaction [{$dbs}]:\n";
 279                         foreach ( $callersByDB as $db => $callers ) {
 280                                 $msg .= "$db: " . implode( '; ', $callers ) . "\n";
 281                         }
 282                         $this->queryLogger->info( $msg );
 283                 }
 284         }
 285
 286         public function hasMasterChanges() {
 287                 $ret = false;
 288                 $this->forEachLB( function ( ILoadBalancer $lb ) use ( &$ret ) {
 289                         $ret = $ret || $lb->hasMasterChanges();
 290                 } );
 291
 292                 return $ret;
 293         }
 294
 295         public function laggedReplicaUsed() {
 296                 $ret = false;
 297                 $this->forEachLB( function ( ILoadBalancer $lb ) use ( &$ret ) {
 298                         $ret = $ret || $lb->laggedReplicaUsed();
 299                 } );
 300
 301                 return $ret;
 302         }
 303
 304         public function hasOrMadeRecentMasterChanges( $age = null ) {
 305                 $ret = false;
 306                 $this->forEachLB( function ( ILoadBalancer $lb ) use ( $age, &$ret ) {
 307                         $ret = $ret || $lb->hasOrMadeRecentMasterChanges( $age );
 308                 } );
 309                 return $ret;
 310         }
 311
 312         public function waitForReplication( array $opts = [] ) {
 313                 $opts += [
 314                         'domain' => false,
 315                         'cluster' => false,
 316                         'timeout' => 60,
 317                         'ifWritesSince' => null
 318                 ];
 319
 320                 if ( $opts['domain'] === false && isset( $opts['wiki'] ) ) {
 321                         $opts['domain'] = $opts['wiki']; // b/c
 322                 }
 323
 324                 // Figure out which clusters need to be checked
 325                 /** @var ILoadBalancer[] $lbs */
 326                 $lbs = [];
 327                 if ( $opts['cluster'] !== false ) {
 328                         $lbs[] = $this->getExternalLB( $opts['cluster'] );
 329                 } elseif ( $opts['domain'] !== false ) {
 330                         $lbs[] = $this->getMainLB( $opts['domain'] );
 331                 } else {
 332                         $this->forEachLB( function ( ILoadBalancer $lb ) use ( &$lbs ) {
 333                                 $lbs[] = $lb;
 334                         } );
 335                         if ( !$lbs ) {
 336                                 return; // nothing actually used
 337                         }
 338                 }
 339
 340                 // Get all the master positions of applicable DBs right now.
 341                 // This can be faster since waiting on one cluster reduces the
 342                 // time needed to wait on the next clusters.
 343                 $masterPositions = array_fill( 0, count( $lbs ), false );
 344                 foreach ( $lbs as $i => $lb ) {
 345                         if ( $lb->getServerCount() <= 1 ) {
 346                                 // T29975 - Don't try to wait for replica DBs if there are none
 347                                 // Prevents permission error when getting master position
 348                                 continue;
 349                         } elseif ( $opts['ifWritesSince']
 350                                 && $lb->lastMasterChangeTimestamp() < $opts['ifWritesSince']
 351                         ) {
 352                                 continue; // no writes since the last wait
 353                         }
 354                         $masterPositions[$i] = $lb->getMasterPos();
 355                 }
 356
 357                 // Run any listener callbacks *after* getting the DB positions. The more
 358                 // time spent in the callbacks, the less time is spent in waitForAll().
 359                 foreach ( $this->replicationWaitCallbacks as $callback ) {
 360                         $callback();
 361                 }
 362
 363                 $failed = [];
 364                 foreach ( $lbs as $i => $lb ) {
 365                         if ( $masterPositions[$i] ) {
 366                                 // The RDBMS may not support getMasterPos()
 367                                 if ( !$lb->waitForAll( $masterPositions[$i], $opts['timeout'] ) ) {
 368                                         $failed[] = $lb->getServerName( $lb->getWriterIndex() );
 369                                 }
 370                         }
 371                 }
 372
 373                 if ( $failed ) {
 374                         throw new DBReplicationWaitError(
 375                                 null,
 376                                 "Could not wait for replica DBs to catch up to " .
 377                                 implode( ', ', $failed )
 378                         );
 379                 }
 380         }
 381
 382         public function setWaitForReplicationListener( $name, callable $callback = null ) {
 383                 if ( $callback ) {
 384                         $this->replicationWaitCallbacks[$name] = $callback;
 385                 } else {
 386                         unset( $this->replicationWaitCallbacks[$name] );
 387                 }
 388         }
 389
 390         public function getEmptyTransactionTicket( $fname ) {
 391                 if ( $this->hasMasterChanges() ) {
 392                         $this->queryLogger->error( __METHOD__ . ": $fname does not have outer scope.\n" .
 393                                 ( new RuntimeException() )->getTraceAsString() );
 394
 395                         return null;
 396                 }
 397
 398                 return $this->ticket;
 399         }
 400
 401         public function commitAndWaitForReplication( $fname, $ticket, array $opts = [] ) {
 402                 if ( $ticket !== $this->ticket ) {
 403                         $this->perfLogger->error( __METHOD__ . ": $fname does not have outer scope.\n" .
 404                                 ( new RuntimeException() )->getTraceAsString() );
 405
 406                         return;
 407                 }
 408
 409                 // The transaction owner and any caller with the empty transaction ticket can commit
 410                 // so that getEmptyTransactionTicket() callers don't risk seeing DBTransactionError.
 411                 if ( $this->trxRoundId !== false && $fname !== $this->trxRoundId ) {
 412                         $this->queryLogger->info( "$fname: committing on behalf of {$this->trxRoundId}." );
 413                         $fnameEffective = $this->trxRoundId;
 414                 } else {
 415                         $fnameEffective = $fname;
 416                 }
 417
 418                 $this->commitMasterChanges( $fnameEffective );
 419                 $this->waitForReplication( $opts );
 420                 // If a nested caller committed on behalf of $fname, start another empty $fname
 421                 // transaction, leaving the caller with the same empty transaction state as before.
 422                 if ( $fnameEffective !== $fname ) {
 423                         $this->beginMasterChanges( $fnameEffective );
 424                 }
 425         }
 426
 427         public function getChronologyProtectorTouched( $dbName ) {
 428                 return $this->getChronologyProtector()->getTouched( $dbName );
 429         }
 430
 431         public function disableChronologyProtection() {
 432                 $this->getChronologyProtector()->setEnabled( false );
 433         }
 434
 435         /**
 436          * @return ChronologyProtector
 437          */
 438         protected function getChronologyProtector() {
 439                 if ( $this->chronProt ) {
 440                         return $this->chronProt;
 441                 }
 442
 443                 $this->chronProt = new ChronologyProtector(
 444                         $this->memStash,
 445                         [
 446                                 'ip' => $this->requestInfo['IPAddress'],
 447                                 'agent' => $this->requestInfo['UserAgent'],
 448                         ],
 449                         $this->requestInfo['ChronologyPositionIndex']
 450                 );
 451                 $this->chronProt->setLogger( $this->replLogger );
 452
 453                 if ( $this->cliMode ) {
 454                         $this->chronProt->setEnabled( false );
 455                 } elseif ( $this->requestInfo['ChronologyProtection'] === 'false' ) {
 456                         // Request opted out of using position wait logic. This is useful for requests
 457                         // done by the job queue or background ETL that do not have a meaningful session.
 458                         $this->chronProt->setWaitEnabled( false );
 459                 }
 460
 461                 $this->replLogger->debug( __METHOD__ . ': using request info ' .
 462                         json_encode( $this->requestInfo, JSON_PRETTY_PRINT ) );
 463
 464                 return $this->chronProt;
 465         }
 466
 467         /**
 468          * Get and record all of the staged DB positions into persistent memory storage
 469          *
 470          * @param ChronologyProtector $cp
 471          * @param callable|null $workCallback Work to do instead of waiting on syncing positions
 472          * @param string $mode One of (sync, async); whether to wait on remote datacenters
 473          * @param int|null &$cpIndex DB position key write counter; incremented on update
 474          */
 475         protected function shutdownChronologyProtector(
 476                 ChronologyProtector $cp, $workCallback, $mode, &$cpIndex = null
 477         ) {
 478                 // Record all the master positions needed
 479                 $this->forEachLB( function ( ILoadBalancer $lb ) use ( $cp ) {
 480                         $cp->shutdownLB( $lb );
 481                 } );
 482                 // Write them to the persistent stash. Try to do something useful by running $work
 483                 // while ChronologyProtector waits for the stash write to replicate to all DCs.
 484                 $unsavedPositions = $cp->shutdown( $workCallback, $mode, $cpIndex );
 485                 if ( $unsavedPositions && $workCallback ) {
 486                         // Invoke callback in case it did not cache the result yet
 487                         $workCallback(); // work now to block for less time in waitForAll()
 488                 }
 489                 // If the positions failed to write to the stash, at least wait on local datacenter
 490                 // replica DBs to catch up before responding. Even if there are several DCs, this increases
 491                 // the chance that the user will see their own changes immediately afterwards. As long
 492                 // as the sticky DC cookie applies (same domain), this is not even an issue.
 493                 $this->forEachLB( function ( ILoadBalancer $lb ) use ( $unsavedPositions ) {
 494                         $masterName = $lb->getServerName( $lb->getWriterIndex() );
 495                         if ( isset( $unsavedPositions[$masterName] ) ) {
 496                                 $lb->waitForAll( $unsavedPositions[$masterName] );
 497                         }
 498                 } );
 499         }
 500
 501         /**
 502          * Base parameters to LoadBalancer::__construct()
 503          * @return array
 504          */
 505         final protected function baseLoadBalancerParams() {
 506                 return [
 507                         'localDomain' => $this->localDomain,
 508                         'readOnlyReason' => $this->readOnlyReason,
 509                         'srvCache' => $this->srvCache,
 510                         'wanCache' => $this->wanCache,
 511                         'profiler' => $this->profiler,
 512                         'trxProfiler' => $this->trxProfiler,
 513                         'queryLogger' => $this->queryLogger,
 514                         'connLogger' => $this->connLogger,
 515                         'replLogger' => $this->replLogger,
 516                         'errorLogger' => $this->errorLogger,
 517                         'hostname' => $this->hostname,
 518                         'cliMode' => $this->cliMode,
 519                         'agent' => $this->agent,
 520                         'chronologyProtector' => $this->getChronologyProtector()
 521                 ];
 522         }
 523
 524         /**
 525          * @param ILoadBalancer $lb
 526          */
 527         protected function initLoadBalancer( ILoadBalancer $lb ) {
 528                 if ( $this->trxRoundId !== false ) {
 529                         $lb->beginMasterChanges( $this->trxRoundId ); // set DBO_TRX
 530                 }
 531
 532                 $lb->setTableAliases( $this->tableAliases );
 533                 $lb->setIndexAliases( $this->indexAliases );
 534         }
 535
 536         public function setTableAliases( array $aliases ) {
 537                 $this->tableAliases = $aliases;
 538         }
 539
 540         public function setIndexAliases( array $aliases ) {
 541                 $this->indexAliases = $aliases;
 542         }
 543
 544         public function setDomainPrefix( $prefix ) {
 545                 $this->localDomain = new DatabaseDomain(
 546                         $this->localDomain->getDatabase(),
 547                         null,
 548                         $prefix
 549                 );
 550
 551                 $this->forEachLB( function ( ILoadBalancer $lb ) use ( $prefix ) {
 552                         $lb->setDomainPrefix( $prefix );
 553                 } );
 554         }
 555
 556         public function closeAll() {
 557                 $this->forEachLBCallMethod( 'closeAll', [] );
 558         }
 559
 560         public function setAgentName( $agent ) {
 561                 $this->agent = $agent;
 562         }
 563
 564         public function appendShutdownCPIndexAsQuery( $url, $index ) {
 565                 $usedCluster = 0;
 566                 $this->forEachLB( function ( ILoadBalancer $lb ) use ( &$usedCluster ) {
 567                         $usedCluster |= ( $lb->getServerCount() > 1 );
 568                 } );
 569
 570                 if ( !$usedCluster ) {
 571                         return $url; // no master/replica clusters touched
 572                 }
 573
 574                 return strpos( $url, '?' ) === false ? "$url?cpPosIndex=$index" : "$url&cpPosIndex=$index";
 575         }
 576
 577         public function setRequestInfo( array $info ) {
 578                 $this->requestInfo = $info + $this->requestInfo;
 579         }
 580
 581         /**
 582          * Make PHP ignore user aborts/disconnects until the returned
 583          * value leaves scope. This returns null and does nothing in CLI mode.
 584          *
 585          * @return ScopedCallback|null
 586          */
 587         final protected function getScopedPHPBehaviorForCommit() {
 588                 if ( PHP_SAPI != 'cli' ) { // https://bugs.php.net/bug.php?id=47540
 589                         $old = ignore_user_abort( true ); // avoid half-finished operations
 590                         return new ScopedCallback( function () use ( $old ) {
 591                                 ignore_user_abort( $old );
 592                         } );
 593                 }
 594
 595                 return null;
 596         }
 597
 598         function __destruct() {
 599                 $this->destroy();
 600         }
 601 }
 602
 603 class_alias( LBFactory::class, 'LBFactory' );