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'] )
 128                         ? $conf['cliMode']
 129                         : ( PHP_SAPI === 'cli' || PHP_SAPI === 'phpdbg' );
 130                 $this->hostname = isset( $conf['hostname'] ) ? $conf['hostname'] : gethostname();
 131                 $this->agent = isset( $conf['agent'] ) ? $conf['agent'] : '';
 132
 133                 $this->ticket = mt_rand();
 134         }
 135
 136         public function destroy() {
 137                 $this->shutdown( self::SHUTDOWN_NO_CHRONPROT );
 138                 $this->forEachLBCallMethod( 'disable' );
 139         }
 140
 141         public function shutdown(
 142                 $mode = self::SHUTDOWN_CHRONPROT_SYNC, callable $workCallback = null, &$cpIndex = null
 143         ) {
 144                 $chronProt = $this->getChronologyProtector();
 145                 if ( $mode === self::SHUTDOWN_CHRONPROT_SYNC ) {
 146                         $this->shutdownChronologyProtector( $chronProt, $workCallback, 'sync', $cpIndex );
 147                 } elseif ( $mode === self::SHUTDOWN_CHRONPROT_ASYNC ) {
 148                         $this->shutdownChronologyProtector( $chronProt, null, 'async', $cpIndex );
 149                 }
 150
 151                 $this->commitMasterChanges( __METHOD__ ); // sanity
 152         }
 153
 154         /**
 155          * @see ILBFactory::newMainLB()
 156          * @param bool $domain
 157          * @return LoadBalancer
 158          */
 159         abstract public function newMainLB( $domain = false );
 160
 161         /**
 162          * @see ILBFactory::getMainLB()
 163          * @param bool $domain
 164          * @return LoadBalancer
 165          */
 166         abstract public function getMainLB( $domain = false );
 167
 168         /**
 169          * @see ILBFactory::newExternalLB()
 170          * @param string $cluster
 171          * @return LoadBalancer
 172          */
 173         abstract public function newExternalLB( $cluster );
 174
 175         /**
 176          * @see ILBFactory::getExternalLB()
 177          * @param string $cluster
 178          * @return LoadBalancer
 179          */
 180         abstract public function getExternalLB( $cluster );
 181
 182         /**
 183          * Call a method of each tracked load balancer
 184          *
 185          * @param string $methodName
 186          * @param array $args
 187          */
 188         protected function forEachLBCallMethod( $methodName, array $args = [] ) {
 189                 $this->forEachLB(
 190                         function ( ILoadBalancer $loadBalancer, $methodName, array $args ) {
 191                                 call_user_func_array( [ $loadBalancer, $methodName ], $args );
 192                         },
 193                         [ $methodName, $args ]
 194                 );
 195         }
 196
 197         public function flushReplicaSnapshots( $fname = __METHOD__ ) {
 198                 $this->forEachLBCallMethod( 'flushReplicaSnapshots', [ $fname ] );
 199         }
 200
 201         public function commitAll( $fname = __METHOD__, array $options = [] ) {
 202                 $this->commitMasterChanges( $fname, $options );
 203                 $this->forEachLBCallMethod( 'commitAll', [ $fname ] );
 204         }
 205
 206         public function beginMasterChanges( $fname = __METHOD__ ) {
 207                 if ( $this->trxRoundId !== false ) {
 208                         throw new DBTransactionError(
 209                                 null,
 210                                 "$fname: transaction round '{$this->trxRoundId}' already started."
 211                         );
 212                 }
 213                 $this->trxRoundId = $fname;
 214                 // Set DBO_TRX flags on all appropriate DBs
 215                 $this->forEachLBCallMethod( 'beginMasterChanges', [ $fname ] );
 216         }
 217
 218         public function commitMasterChanges( $fname = __METHOD__, array $options = [] ) {
 219                 if ( $this->trxRoundId !== false && $this->trxRoundId !== $fname ) {
 220                         throw new DBTransactionError(
 221                                 null,
 222                                 "$fname: transaction round '{$this->trxRoundId}' still running."
 223                         );
 224                 }
 225                 /** @noinspection PhpUnusedLocalVariableInspection */
 226                 $scope = $this->getScopedPHPBehaviorForCommit(); // try to ignore client aborts
 227                 // Run pre-commit callbacks and suppress post-commit callbacks, aborting on failure
 228                 $this->forEachLBCallMethod( 'finalizeMasterChanges' );
 229                 $this->trxRoundId = false;
 230                 // Perform pre-commit checks, aborting on failure
 231                 $this->forEachLBCallMethod( 'approveMasterChanges', [ $options ] );
 232                 // Log the DBs and methods involved in multi-DB transactions
 233                 $this->logIfMultiDbTransaction();
 234                 // Actually perform the commit on all master DB connections and revert DBO_TRX
 235                 $this->forEachLBCallMethod( 'commitMasterChanges', [ $fname ] );
 236                 // Run all post-commit callbacks
 237                 /** @var Exception $e */
 238                 $e = null; // first callback exception
 239                 $this->forEachLB( function ( ILoadBalancer $lb ) use ( &$e ) {
 240                         $ex = $lb->runMasterPostTrxCallbacks( IDatabase::TRIGGER_COMMIT );
 241                         $e = $e ?: $ex;
 242                 } );
 243                 // Commit any dangling DBO_TRX transactions from callbacks on one DB to another DB
 244                 $this->forEachLBCallMethod( 'commitMasterChanges', [ $fname ] );
 245                 // Throw any last post-commit callback error
 246                 if ( $e instanceof Exception ) {
 247                         throw $e;
 248                 }
 249         }
 250
 251         public function rollbackMasterChanges( $fname = __METHOD__ ) {
 252                 $this->trxRoundId = false;
 253                 $this->forEachLBCallMethod( 'suppressTransactionEndCallbacks' );
 254                 $this->forEachLBCallMethod( 'rollbackMasterChanges', [ $fname ] );
 255                 // Run all post-rollback callbacks
 256                 $this->forEachLB( function ( ILoadBalancer $lb ) {
 257                         $lb->runMasterPostTrxCallbacks( IDatabase::TRIGGER_ROLLBACK );
 258                 } );
 259         }
 260
 261         public function hasTransactionRound() {
 262                 return ( $this->trxRoundId !== false );
 263         }
 264
 265         /**
 266          * Log query info if multi DB transactions are going to be committed now
 267          */
 268         private function logIfMultiDbTransaction() {
 269                 $callersByDB = [];
 270                 $this->forEachLB( function ( ILoadBalancer $lb ) use ( &$callersByDB ) {
 271                         $masterName = $lb->getServerName( $lb->getWriterIndex() );
 272                         $callers = $lb->pendingMasterChangeCallers();
 273                         if ( $callers ) {
 274                                 $callersByDB[$masterName] = $callers;
 275                         }
 276                 } );
 277
 278                 if ( count( $callersByDB ) >= 2 ) {
 279                         $dbs = implode( ', ', array_keys( $callersByDB ) );
 280                         $msg = "Multi-DB transaction [{$dbs}]:\n";
 281                         foreach ( $callersByDB as $db => $callers ) {
 282                                 $msg .= "$db: " . implode( '; ', $callers ) . "\n";
 283                         }
 284                         $this->queryLogger->info( $msg );
 285                 }
 286         }
 287
 288         public function hasMasterChanges() {
 289                 $ret = false;
 290                 $this->forEachLB( function ( ILoadBalancer $lb ) use ( &$ret ) {
 291                         $ret = $ret || $lb->hasMasterChanges();
 292                 } );
 293
 294                 return $ret;
 295         }
 296
 297         public function laggedReplicaUsed() {
 298                 $ret = false;
 299                 $this->forEachLB( function ( ILoadBalancer $lb ) use ( &$ret ) {
 300                         $ret = $ret || $lb->laggedReplicaUsed();
 301                 } );
 302
 303                 return $ret;
 304         }
 305
 306         public function hasOrMadeRecentMasterChanges( $age = null ) {
 307                 $ret = false;
 308                 $this->forEachLB( function ( ILoadBalancer $lb ) use ( $age, &$ret ) {
 309                         $ret = $ret || $lb->hasOrMadeRecentMasterChanges( $age );
 310                 } );
 311                 return $ret;
 312         }
 313
 314         public function waitForReplication( array $opts = [] ) {
 315                 $opts += [
 316                         'domain' => false,
 317                         'cluster' => false,
 318                         'timeout' => $this->cliMode ? 60 : 10,
 319                         'ifWritesSince' => null
 320                 ];
 321
 322                 if ( $opts['domain'] === false && isset( $opts['wiki'] ) ) {
 323                         $opts['domain'] = $opts['wiki']; // b/c
 324                 }
 325
 326                 // Figure out which clusters need to be checked
 327                 /** @var ILoadBalancer[] $lbs */
 328                 $lbs = [];
 329                 if ( $opts['cluster'] !== false ) {
 330                         $lbs[] = $this->getExternalLB( $opts['cluster'] );
 331                 } elseif ( $opts['domain'] !== false ) {
 332                         $lbs[] = $this->getMainLB( $opts['domain'] );
 333                 } else {
 334                         $this->forEachLB( function ( ILoadBalancer $lb ) use ( &$lbs ) {
 335                                 $lbs[] = $lb;
 336                         } );
 337                         if ( !$lbs ) {
 338                                 return; // nothing actually used
 339                         }
 340                 }
 341
 342                 // Get all the master positions of applicable DBs right now.
 343                 // This can be faster since waiting on one cluster reduces the
 344                 // time needed to wait on the next clusters.
 345                 $masterPositions = array_fill( 0, count( $lbs ), false );
 346                 foreach ( $lbs as $i => $lb ) {
 347                         if ( $lb->getServerCount() <= 1 ) {
 348                                 // T29975 - Don't try to wait for replica DBs if there are none
 349                                 // Prevents permission error when getting master position
 350                                 continue;
 351                         } elseif ( $opts['ifWritesSince']
 352                                 && $lb->lastMasterChangeTimestamp() < $opts['ifWritesSince']
 353                         ) {
 354                                 continue; // no writes since the last wait
 355                         }
 356                         $masterPositions[$i] = $lb->getMasterPos();
 357                 }
 358
 359                 // Run any listener callbacks *after* getting the DB positions. The more
 360                 // time spent in the callbacks, the less time is spent in waitForAll().
 361                 foreach ( $this->replicationWaitCallbacks as $callback ) {
 362                         $callback();
 363                 }
 364
 365                 $failed = [];
 366                 foreach ( $lbs as $i => $lb ) {
 367                         if ( $masterPositions[$i] ) {
 368                                 // The RDBMS may not support getMasterPos()
 369                                 if ( !$lb->waitForAll( $masterPositions[$i], $opts['timeout'] ) ) {
 370                                         $failed[] = $lb->getServerName( $lb->getWriterIndex() );
 371                                 }
 372                         }
 373                 }
 374
 375                 if ( $failed ) {
 376                         throw new DBReplicationWaitError(
 377                                 null,
 378                                 "Could not wait for replica DBs to catch up to " .
 379                                 implode( ', ', $failed )
 380                         );
 381                 }
 382         }
 383
 384         public function setWaitForReplicationListener( $name, callable $callback = null ) {
 385                 if ( $callback ) {
 386                         $this->replicationWaitCallbacks[$name] = $callback;
 387                 } else {
 388                         unset( $this->replicationWaitCallbacks[$name] );
 389                 }
 390         }
 391
 392         public function getEmptyTransactionTicket( $fname ) {
 393                 if ( $this->hasMasterChanges() ) {
 394                         $this->queryLogger->error( __METHOD__ . ": $fname does not have outer scope.\n" .
 395                                 ( new RuntimeException() )->getTraceAsString() );
 396
 397                         return null;
 398                 }
 399
 400                 return $this->ticket;
 401         }
 402
 403         public function commitAndWaitForReplication( $fname, $ticket, array $opts = [] ) {
 404                 if ( $ticket !== $this->ticket ) {
 405                         $this->perfLogger->error( __METHOD__ . ": $fname does not have outer scope.\n" .
 406                                 ( new RuntimeException() )->getTraceAsString() );
 407
 408                         return;
 409                 }
 410
 411                 // The transaction owner and any caller with the empty transaction ticket can commit
 412                 // so that getEmptyTransactionTicket() callers don't risk seeing DBTransactionError.
 413                 if ( $this->trxRoundId !== false && $fname !== $this->trxRoundId ) {
 414                         $this->queryLogger->info( "$fname: committing on behalf of {$this->trxRoundId}." );
 415                         $fnameEffective = $this->trxRoundId;
 416                 } else {
 417                         $fnameEffective = $fname;
 418                 }
 419
 420                 $this->commitMasterChanges( $fnameEffective );
 421                 $this->waitForReplication( $opts );
 422                 // If a nested caller committed on behalf of $fname, start another empty $fname
 423                 // transaction, leaving the caller with the same empty transaction state as before.
 424                 if ( $fnameEffective !== $fname ) {
 425                         $this->beginMasterChanges( $fnameEffective );
 426                 }
 427         }
 428
 429         public function getChronologyProtectorTouched( $dbName ) {
 430                 return $this->getChronologyProtector()->getTouched( $dbName );
 431         }
 432
 433         public function disableChronologyProtection() {
 434                 $this->getChronologyProtector()->setEnabled( false );
 435         }
 436
 437         /**
 438          * @return ChronologyProtector
 439          */
 440         protected function getChronologyProtector() {
 441                 if ( $this->chronProt ) {
 442                         return $this->chronProt;
 443                 }
 444
 445                 $this->chronProt = new ChronologyProtector(
 446                         $this->memStash,
 447                         [
 448                                 'ip' => $this->requestInfo['IPAddress'],
 449                                 'agent' => $this->requestInfo['UserAgent'],
 450                         ],
 451                         $this->requestInfo['ChronologyPositionIndex']
 452                 );
 453                 $this->chronProt->setLogger( $this->replLogger );
 454
 455                 if ( $this->cliMode ) {
 456                         $this->chronProt->setEnabled( false );
 457                 } elseif ( $this->requestInfo['ChronologyProtection'] === 'false' ) {
 458                         // Request opted out of using position wait logic. This is useful for requests
 459                         // done by the job queue or background ETL that do not have a meaningful session.
 460                         $this->chronProt->setWaitEnabled( false );
 461                 }
 462
 463                 $this->replLogger->debug( __METHOD__ . ': using request info ' .
 464                         json_encode( $this->requestInfo, JSON_PRETTY_PRINT ) );
 465
 466                 return $this->chronProt;
 467         }
 468
 469         /**
 470          * Get and record all of the staged DB positions into persistent memory storage
 471          *
 472          * @param ChronologyProtector $cp
 473          * @param callable|null $workCallback Work to do instead of waiting on syncing positions
 474          * @param string $mode One of (sync, async); whether to wait on remote datacenters
 475          * @param int|null &$cpIndex DB position key write counter; incremented on update
 476          */
 477         protected function shutdownChronologyProtector(
 478                 ChronologyProtector $cp, $workCallback, $mode, &$cpIndex = null
 479         ) {
 480                 // Record all the master positions needed
 481                 $this->forEachLB( function ( ILoadBalancer $lb ) use ( $cp ) {
 482                         $cp->shutdownLB( $lb );
 483                 } );
 484                 // Write them to the persistent stash. Try to do something useful by running $work
 485                 // while ChronologyProtector waits for the stash write to replicate to all DCs.
 486                 $unsavedPositions = $cp->shutdown( $workCallback, $mode, $cpIndex );
 487                 if ( $unsavedPositions && $workCallback ) {
 488                         // Invoke callback in case it did not cache the result yet
 489                         $workCallback(); // work now to block for less time in waitForAll()
 490                 }
 491                 // If the positions failed to write to the stash, at least wait on local datacenter
 492                 // replica DBs to catch up before responding. Even if there are several DCs, this increases
 493                 // the chance that the user will see their own changes immediately afterwards. As long
 494                 // as the sticky DC cookie applies (same domain), this is not even an issue.
 495                 $this->forEachLB( function ( ILoadBalancer $lb ) use ( $unsavedPositions ) {
 496                         $masterName = $lb->getServerName( $lb->getWriterIndex() );
 497                         if ( isset( $unsavedPositions[$masterName] ) ) {
 498                                 $lb->waitForAll( $unsavedPositions[$masterName] );
 499                         }
 500                 } );
 501         }
 502
 503         /**
 504          * Base parameters to LoadBalancer::__construct()
 505          * @return array
 506          */
 507         final protected function baseLoadBalancerParams() {
 508                 return [
 509                         'localDomain' => $this->localDomain,
 510                         'readOnlyReason' => $this->readOnlyReason,
 511                         'srvCache' => $this->srvCache,
 512                         'wanCache' => $this->wanCache,
 513                         'profiler' => $this->profiler,
 514                         'trxProfiler' => $this->trxProfiler,
 515                         'queryLogger' => $this->queryLogger,
 516                         'connLogger' => $this->connLogger,
 517                         'replLogger' => $this->replLogger,
 518                         'errorLogger' => $this->errorLogger,
 519                         'hostname' => $this->hostname,
 520                         'cliMode' => $this->cliMode,
 521                         'agent' => $this->agent,
 522                         'chronologyProtector' => $this->getChronologyProtector()
 523                 ];
 524         }
 525
 526         /**
 527          * @param ILoadBalancer $lb
 528          */
 529         protected function initLoadBalancer( ILoadBalancer $lb ) {
 530                 if ( $this->trxRoundId !== false ) {
 531                         $lb->beginMasterChanges( $this->trxRoundId ); // set DBO_TRX
 532                 }
 533
 534                 $lb->setTableAliases( $this->tableAliases );
 535                 $lb->setIndexAliases( $this->indexAliases );
 536         }
 537
 538         public function setTableAliases( array $aliases ) {
 539                 $this->tableAliases = $aliases;
 540         }
 541
 542         public function setIndexAliases( array $aliases ) {
 543                 $this->indexAliases = $aliases;
 544         }
 545
 546         public function setDomainPrefix( $prefix ) {
 547                 $this->localDomain = new DatabaseDomain(
 548                         $this->localDomain->getDatabase(),
 549                         null,
 550                         $prefix
 551                 );
 552
 553                 $this->forEachLB( function ( ILoadBalancer $lb ) use ( $prefix ) {
 554                         $lb->setDomainPrefix( $prefix );
 555                 } );
 556         }
 557
 558         public function closeAll() {
 559                 $this->forEachLBCallMethod( 'closeAll', [] );
 560         }
 561
 562         public function setAgentName( $agent ) {
 563                 $this->agent = $agent;
 564         }
 565
 566         public function appendShutdownCPIndexAsQuery( $url, $index ) {
 567                 $usedCluster = 0;
 568                 $this->forEachLB( function ( ILoadBalancer $lb ) use ( &$usedCluster ) {
 569                         $usedCluster |= ( $lb->getServerCount() > 1 );
 570                 } );
 571
 572                 if ( !$usedCluster ) {
 573                         return $url; // no master/replica clusters touched
 574                 }
 575
 576                 return strpos( $url, '?' ) === false ? "$url?cpPosIndex=$index" : "$url&cpPosIndex=$index";
 577         }
 578
 579         public function setRequestInfo( array $info ) {
 580                 $this->requestInfo = $info + $this->requestInfo;
 581         }
 582
 583         /**
 584          * Make PHP ignore user aborts/disconnects until the returned
 585          * value leaves scope. This returns null and does nothing in CLI mode.
 586          *
 587          * @return ScopedCallback|null
 588          */
 589         final protected function getScopedPHPBehaviorForCommit() {
 590                 if ( PHP_SAPI != 'cli' ) { // https://bugs.php.net/bug.php?id=47540
 591                         $old = ignore_user_abort( true ); // avoid half-finished operations
 592                         return new ScopedCallback( function () use ( $old ) {
 593                                 ignore_user_abort( $old );
 594                         } );
 595                 }
 596
 597                 return null;
 598         }
 599
 600         function __destruct() {
 601                 $this->destroy();
 602         }
 603 }
 604
 605 class_alias( LBFactory::class, 'LBFactory' );