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 use Psr\Log\LoggerInterface;
  25
  26 /**
  27  * An interface for generating database load balancers
  28  * @ingroup Database
  29  */
  30 abstract class LBFactory {
  31         /** @var ChronologyProtector */
  32         protected $chronProt;
  33         /** @var object|string Class name or object With profileIn/profileOut methods */
  34         protected $profiler;
  35         /** @var TransactionProfiler */
  36         protected $trxProfiler;
  37         /** @var LoggerInterface */
  38         protected $replLogger;
  39         /** @var LoggerInterface */
  40         protected $connLogger;
  41         /** @var LoggerInterface */
  42         protected $queryLogger;
  43         /** @var LoggerInterface */
  44         protected $perfLogger;
  45         /** @var callable Error logger */
  46         protected $errorLogger;
  47         /** @var BagOStuff */
  48         protected $srvCache;
  49         /** @var BagOStuff */
  50         protected $memCache;
  51         /** @var WANObjectCache */
  52         protected $wanCache;
  53
  54         /** @var DatabaseDomain Local domain */
  55         protected $localDomain;
  56         /** @var string Local hostname of the app server */
  57         protected $hostname;
  58         /** @var array Web request information about the client */
  59         protected $requestInfo;
  60
  61         /** @var mixed */
  62         protected $ticket;
  63         /** @var string|bool String if a requested DBO_TRX transaction round is active */
  64         protected $trxRoundId = false;
  65         /** @var string|bool Reason all LBs are read-only or false if not */
  66         protected $readOnlyReason = false;
  67         /** @var callable[] */
  68         protected $replicationWaitCallbacks = [];
  69
  70         /** @var bool Whether this PHP instance is for a CLI script */
  71         protected $cliMode;
  72         /** @var string Agent name for query profiling */
  73         protected $agent;
  74
  75         const SHUTDOWN_NO_CHRONPROT = 0; // don't save DB positions at all
  76         const SHUTDOWN_CHRONPROT_ASYNC = 1; // save DB positions, but don't wait on remote DCs
  77         const SHUTDOWN_CHRONPROT_SYNC = 2; // save DB positions, waiting on all DCs
  78
  79         private static $loggerFields =
  80                 [ 'replLogger', 'connLogger', 'queryLogger', 'perfLogger' ];
  81
  82         /**
  83          * @TODO: document base params here
  84          * @param array $conf
  85          */
  86         public function __construct( array $conf ) {
  87                 $this->localDomain = isset( $conf['localDomain'] )
  88                         ? DatabaseDomain::newFromId( $conf['localDomain'] )
  89                         : DatabaseDomain::newUnspecified();
  90
  91                 if ( isset( $conf['readOnlyReason'] ) && is_string( $conf['readOnlyReason'] ) ) {
  92                         $this->readOnlyReason = $conf['readOnlyReason'];
  93                 }
  94
  95                 $this->srvCache = isset( $conf['srvCache'] ) ? $conf['srvCache'] : new EmptyBagOStuff();
  96                 $this->memCache = isset( $conf['memCache'] ) ? $conf['memCache'] : new EmptyBagOStuff();
  97                 $this->wanCache = isset( $conf['wanCache'] )
  98                         ? $conf['wanCache']
  99                         : WANObjectCache::newEmpty();
 100
 101                 foreach ( self::$loggerFields as $key ) {
 102                         $this->$key = isset( $conf[$key] ) ? $conf[$key] : new \Psr\Log\NullLogger();
 103                 }
 104                 $this->errorLogger = isset( $conf['errorLogger'] )
 105                         ? $conf['errorLogger']
 106                         : function ( Exception $e ) {
 107                                 trigger_error( E_WARNING, get_class( $e ) . ': ' . $e->getMessage() );
 108                         };
 109
 110                 $this->chronProt = isset( $conf['chronProt'] ) ? $conf['chronProt'] : null;
 111
 112                 $this->profiler = isset( $params['profiler'] ) ? $params['profiler'] : null;
 113                 $this->trxProfiler = isset( $conf['trxProfiler'] )
 114                         ? $conf['trxProfiler']
 115                         : new TransactionProfiler();
 116
 117                 $this->requestInfo = [
 118                         'IPAddress' => isset( $_SERVER[ 'REMOTE_ADDR' ] ) ? $_SERVER[ 'REMOTE_ADDR' ] : '',
 119                         'UserAgent' => isset( $_SERVER['HTTP_USER_AGENT'] ) ? $_SERVER['HTTP_USER_AGENT'] : '',
 120                         'ChronologyProtection' => 'true'
 121                 ];
 122
 123                 $this->cliMode = isset( $params['cliMode'] ) ? $params['cliMode'] : PHP_SAPI === 'cli';
 124                 $this->hostname = isset( $conf['hostname'] ) ? $conf['hostname'] : gethostname();
 125                 $this->agent = isset( $params['agent'] ) ? $params['agent'] : '';
 126
 127                 $this->ticket = mt_rand();
 128         }
 129
 130         /**
 131          * Disables all load balancers. All connections are closed, and any attempt to
 132          * open a new connection will result in a DBAccessError.
 133          * @see LoadBalancer::disable()
 134          */
 135         public function destroy() {
 136                 $this->shutdown( self::SHUTDOWN_NO_CHRONPROT );
 137                 $this->forEachLBCallMethod( 'disable' );
 138         }
 139
 140         /**
 141          * Create a new load balancer object. The resulting object will be untracked,
 142          * not chronology-protected, and the caller is responsible for cleaning it up.
 143          *
 144          * @param bool|string $domain Domain ID, or false for the current domain
 145          * @return ILoadBalancer
 146          */
 147         abstract public function newMainLB( $domain = false );
 148
 149         /**
 150          * Get a cached (tracked) load balancer object.
 151          *
 152          * @param bool|string $domain Domain ID, or false for the current domain
 153          * @return ILoadBalancer
 154          */
 155         abstract public function getMainLB( $domain = false );
 156
 157         /**
 158          * Create a new load balancer for external storage. The resulting object will be
 159          * untracked, not chronology-protected, and the caller is responsible for
 160          * cleaning it up.
 161          *
 162          * @param string $cluster External storage cluster, or false for core
 163          * @param bool|string $domain Domain ID, or false for the current domain
 164          * @return ILoadBalancer
 165          */
 166         abstract protected function newExternalLB( $cluster, $domain = false );
 167
 168         /**
 169          * Get a cached (tracked) load balancer for external storage
 170          *
 171          * @param string $cluster External storage cluster, or false for core
 172          * @param bool|string $domain Domain ID, or false for the current domain
 173          * @return ILoadBalancer
 174          */
 175         abstract public function getExternalLB( $cluster, $domain = false );
 176
 177         /**
 178          * Execute a function for each tracked load balancer
 179          * The callback is called with the load balancer as the first parameter,
 180          * and $params passed as the subsequent parameters.
 181          *
 182          * @param callable $callback
 183          * @param array $params
 184          */
 185         abstract public function forEachLB( $callback, array $params = [] );
 186
 187         /**
 188          * Prepare all tracked load balancers for shutdown
 189          * @param integer $mode One of the class SHUTDOWN_* constants
 190          * @param callable|null $workCallback Work to mask ChronologyProtector writes
 191          */
 192         public function shutdown(
 193                 $mode = self::SHUTDOWN_CHRONPROT_SYNC, callable $workCallback = null
 194         ) {
 195                 $chronProt = $this->getChronologyProtector();
 196                 if ( $mode === self::SHUTDOWN_CHRONPROT_SYNC ) {
 197                         $this->shutdownChronologyProtector( $chronProt, $workCallback, 'sync' );
 198                 } elseif ( $mode === self::SHUTDOWN_CHRONPROT_ASYNC ) {
 199                         $this->shutdownChronologyProtector( $chronProt, null, 'async' );
 200                 }
 201
 202                 $this->commitMasterChanges( __METHOD__ ); // sanity
 203         }
 204
 205         /**
 206          * Call a method of each tracked load balancer
 207          *
 208          * @param string $methodName
 209          * @param array $args
 210          */
 211         protected function forEachLBCallMethod( $methodName, array $args = [] ) {
 212                 $this->forEachLB(
 213                         function ( ILoadBalancer $loadBalancer, $methodName, array $args ) {
 214                                 call_user_func_array( [ $loadBalancer, $methodName ], $args );
 215                         },
 216                         [ $methodName, $args ]
 217                 );
 218         }
 219
 220         /**
 221          * Commit all replica DB transactions so as to flush any REPEATABLE-READ or SSI snapshot
 222          *
 223          * @param string $fname Caller name
 224          * @since 1.28
 225          */
 226         public function flushReplicaSnapshots( $fname = __METHOD__ ) {
 227                 $this->forEachLBCallMethod( 'flushReplicaSnapshots', [ $fname ] );
 228         }
 229
 230         /**
 231          * Commit on all connections. Done for two reasons:
 232          * 1. To commit changes to the masters.
 233          * 2. To release the snapshot on all connections, master and replica DB.
 234          * @param string $fname Caller name
 235          * @param array $options Options map:
 236          *   - maxWriteDuration: abort if more than this much time was spent in write queries
 237          */
 238         public function commitAll( $fname = __METHOD__, array $options = [] ) {
 239                 $this->commitMasterChanges( $fname, $options );
 240                 $this->forEachLBCallMethod( 'commitAll', [ $fname ] );
 241         }
 242
 243         /**
 244          * Flush any master transaction snapshots and set DBO_TRX (if DBO_DEFAULT is set)
 245          *
 246          * The DBO_TRX setting will be reverted to the default in each of these methods:
 247          *   - commitMasterChanges()
 248          *   - rollbackMasterChanges()
 249          *   - commitAll()
 250          *
 251          * This allows for custom transaction rounds from any outer transaction scope.
 252          *
 253          * @param string $fname
 254          * @throws DBTransactionError
 255          * @since 1.28
 256          */
 257         public function beginMasterChanges( $fname = __METHOD__ ) {
 258                 if ( $this->trxRoundId !== false ) {
 259                         throw new DBTransactionError(
 260                                 null,
 261                                 "$fname: transaction round '{$this->trxRoundId}' already started."
 262                         );
 263                 }
 264                 $this->trxRoundId = $fname;
 265                 // Set DBO_TRX flags on all appropriate DBs
 266                 $this->forEachLBCallMethod( 'beginMasterChanges', [ $fname ] );
 267         }
 268
 269         /**
 270          * Commit changes on all master connections
 271          * @param string $fname Caller name
 272          * @param array $options Options map:
 273          *   - maxWriteDuration: abort if more than this much time was spent in write queries
 274          * @throws Exception
 275          */
 276         public function commitMasterChanges( $fname = __METHOD__, array $options = [] ) {
 277                 if ( $this->trxRoundId !== false && $this->trxRoundId !== $fname ) {
 278                         throw new DBTransactionError(
 279                                 null,
 280                                 "$fname: transaction round '{$this->trxRoundId}' still running."
 281                         );
 282                 }
 283                 // Run pre-commit callbacks and suppress post-commit callbacks, aborting on failure
 284                 $this->forEachLBCallMethod( 'finalizeMasterChanges' );
 285                 $this->trxRoundId = false;
 286                 // Perform pre-commit checks, aborting on failure
 287                 $this->forEachLBCallMethod( 'approveMasterChanges', [ $options ] );
 288                 // Log the DBs and methods involved in multi-DB transactions
 289                 $this->logIfMultiDbTransaction();
 290                 // Actually perform the commit on all master DB connections and revert DBO_TRX
 291                 $this->forEachLBCallMethod( 'commitMasterChanges', [ $fname ] );
 292                 // Run all post-commit callbacks
 293                 /** @var Exception $e */
 294                 $e = null; // first callback exception
 295                 $this->forEachLB( function ( ILoadBalancer $lb ) use ( &$e ) {
 296                         $ex = $lb->runMasterPostTrxCallbacks( IDatabase::TRIGGER_COMMIT );
 297                         $e = $e ?: $ex;
 298                 } );
 299                 // Commit any dangling DBO_TRX transactions from callbacks on one DB to another DB
 300                 $this->forEachLBCallMethod( 'commitMasterChanges', [ $fname ] );
 301                 // Throw any last post-commit callback error
 302                 if ( $e instanceof Exception ) {
 303                         throw $e;
 304                 }
 305         }
 306
 307         /**
 308          * Rollback changes on all master connections
 309          * @param string $fname Caller name
 310          * @since 1.23
 311          */
 312         public function rollbackMasterChanges( $fname = __METHOD__ ) {
 313                 $this->trxRoundId = false;
 314                 $this->forEachLBCallMethod( 'suppressTransactionEndCallbacks' );
 315                 $this->forEachLBCallMethod( 'rollbackMasterChanges', [ $fname ] );
 316                 // Run all post-rollback callbacks
 317                 $this->forEachLB( function ( ILoadBalancer $lb ) {
 318                         $lb->runMasterPostTrxCallbacks( IDatabase::TRIGGER_ROLLBACK );
 319                 } );
 320         }
 321
 322         /**
 323          * Log query info if multi DB transactions are going to be committed now
 324          */
 325         private function logIfMultiDbTransaction() {
 326                 $callersByDB = [];
 327                 $this->forEachLB( function ( ILoadBalancer $lb ) use ( &$callersByDB ) {
 328                         $masterName = $lb->getServerName( $lb->getWriterIndex() );
 329                         $callers = $lb->pendingMasterChangeCallers();
 330                         if ( $callers ) {
 331                                 $callersByDB[$masterName] = $callers;
 332                         }
 333                 } );
 334
 335                 if ( count( $callersByDB ) >= 2 ) {
 336                         $dbs = implode( ', ', array_keys( $callersByDB ) );
 337                         $msg = "Multi-DB transaction [{$dbs}]:\n";
 338                         foreach ( $callersByDB as $db => $callers ) {
 339                                 $msg .= "$db: " . implode( '; ', $callers ) . "\n";
 340                         }
 341                         $this->queryLogger->info( $msg );
 342                 }
 343         }
 344
 345         /**
 346          * Determine if any master connection has pending changes
 347          * @return bool
 348          * @since 1.23
 349          */
 350         public function hasMasterChanges() {
 351                 $ret = false;
 352                 $this->forEachLB( function ( ILoadBalancer $lb ) use ( &$ret ) {
 353                         $ret = $ret || $lb->hasMasterChanges();
 354                 } );
 355
 356                 return $ret;
 357         }
 358
 359         /**
 360          * Detemine if any lagged replica DB connection was used
 361          * @return bool
 362          * @since 1.28
 363          */
 364         public function laggedReplicaUsed() {
 365                 $ret = false;
 366                 $this->forEachLB( function ( ILoadBalancer $lb ) use ( &$ret ) {
 367                         $ret = $ret || $lb->laggedReplicaUsed();
 368                 } );
 369
 370                 return $ret;
 371         }
 372
 373         /**
 374          * Determine if any master connection has pending/written changes from this request
 375          * @param float $age How many seconds ago is "recent" [defaults to LB lag wait timeout]
 376          * @return bool
 377          * @since 1.27
 378          */
 379         public function hasOrMadeRecentMasterChanges( $age = null ) {
 380                 $ret = false;
 381                 $this->forEachLB( function ( ILoadBalancer $lb ) use ( $age, &$ret ) {
 382                         $ret = $ret || $lb->hasOrMadeRecentMasterChanges( $age );
 383                 } );
 384                 return $ret;
 385         }
 386
 387         /**
 388          * Waits for the replica DBs to catch up to the current master position
 389          *
 390          * Use this when updating very large numbers of rows, as in maintenance scripts,
 391          * to avoid causing too much lag. Of course, this is a no-op if there are no replica DBs.
 392          *
 393          * By default this waits on all DB clusters actually used in this request.
 394          * This makes sense when lag being waiting on is caused by the code that does this check.
 395          * In that case, setting "ifWritesSince" can avoid the overhead of waiting for clusters
 396          * that were not changed since the last wait check. To forcefully wait on a specific cluster
 397          * for a given wiki, use the 'wiki' parameter. To forcefully wait on an "external" cluster,
 398          * use the "cluster" parameter.
 399          *
 400          * Never call this function after a large DB write that is *still* in a transaction.
 401          * It only makes sense to call this after the possible lag inducing changes were committed.
 402          *
 403          * @param array $opts Optional fields that include:
 404          *   - wiki : wait on the load balancer DBs that handles the given wiki
 405          *   - cluster : wait on the given external load balancer DBs
 406          *   - timeout : Max wait time. Default: ~60 seconds
 407          *   - ifWritesSince: Only wait if writes were done since this UNIX timestamp
 408          * @throws DBReplicationWaitError If a timeout or error occured waiting on a DB cluster
 409          * @since 1.27
 410          */
 411         public function waitForReplication( array $opts = [] ) {
 412                 $opts += [
 413                         'wiki' => false,
 414                         'cluster' => false,
 415                         'timeout' => 60,
 416                         'ifWritesSince' => null
 417                 ];
 418
 419                 // Figure out which clusters need to be checked
 420                 /** @var ILoadBalancer[] $lbs */
 421                 $lbs = [];
 422                 if ( $opts['cluster'] !== false ) {
 423                         $lbs[] = $this->getExternalLB( $opts['cluster'] );
 424                 } elseif ( $opts['wiki'] !== false ) {
 425                         $lbs[] = $this->getMainLB( $opts['wiki'] );
 426                 } else {
 427                         $this->forEachLB( function ( ILoadBalancer $lb ) use ( &$lbs ) {
 428                                 $lbs[] = $lb;
 429                         } );
 430                         if ( !$lbs ) {
 431                                 return; // nothing actually used
 432                         }
 433                 }
 434
 435                 // Get all the master positions of applicable DBs right now.
 436                 // This can be faster since waiting on one cluster reduces the
 437                 // time needed to wait on the next clusters.
 438                 $masterPositions = array_fill( 0, count( $lbs ), false );
 439                 foreach ( $lbs as $i => $lb ) {
 440                         if ( $lb->getServerCount() <= 1 ) {
 441                                 // Bug 27975 - Don't try to wait for replica DBs if there are none
 442                                 // Prevents permission error when getting master position
 443                                 continue;
 444                         } elseif ( $opts['ifWritesSince']
 445                                 && $lb->lastMasterChangeTimestamp() < $opts['ifWritesSince']
 446                         ) {
 447                                 continue; // no writes since the last wait
 448                         }
 449                         $masterPositions[$i] = $lb->getMasterPos();
 450                 }
 451
 452                 // Run any listener callbacks *after* getting the DB positions. The more
 453                 // time spent in the callbacks, the less time is spent in waitForAll().
 454                 foreach ( $this->replicationWaitCallbacks as $callback ) {
 455                         $callback();
 456                 }
 457
 458                 $failed = [];
 459                 foreach ( $lbs as $i => $lb ) {
 460                         if ( $masterPositions[$i] ) {
 461                                 // The DBMS may not support getMasterPos()
 462                                 if ( !$lb->waitForAll( $masterPositions[$i], $opts['timeout'] ) ) {
 463                                         $failed[] = $lb->getServerName( $lb->getWriterIndex() );
 464                                 }
 465                         }
 466                 }
 467
 468                 if ( $failed ) {
 469                         throw new DBReplicationWaitError(
 470                                 "Could not wait for replica DBs to catch up to " .
 471                                 implode( ', ', $failed )
 472                         );
 473                 }
 474         }
 475
 476         /**
 477          * Add a callback to be run in every call to waitForReplication() before waiting
 478          *
 479          * Callbacks must clear any transactions that they start
 480          *
 481          * @param string $name Callback name
 482          * @param callable|null $callback Use null to unset a callback
 483          * @since 1.28
 484          */
 485         public function setWaitForReplicationListener( $name, callable $callback = null ) {
 486                 if ( $callback ) {
 487                         $this->replicationWaitCallbacks[$name] = $callback;
 488                 } else {
 489                         unset( $this->replicationWaitCallbacks[$name] );
 490                 }
 491         }
 492
 493         /**
 494          * Get a token asserting that no transaction writes are active
 495          *
 496          * @param string $fname Caller name (e.g. __METHOD__)
 497          * @return mixed A value to pass to commitAndWaitForReplication()
 498          * @since 1.28
 499          */
 500         public function getEmptyTransactionTicket( $fname ) {
 501                 if ( $this->hasMasterChanges() ) {
 502                         $this->queryLogger->error( __METHOD__ . ": $fname does not have outer scope." );
 503                         return null;
 504                 }
 505
 506                 return $this->ticket;
 507         }
 508
 509         /**
 510          * Convenience method for safely running commitMasterChanges()/waitForReplication()
 511          *
 512          * This will commit and wait unless $ticket indicates it is unsafe to do so
 513          *
 514          * @param string $fname Caller name (e.g. __METHOD__)
 515          * @param mixed $ticket Result of getEmptyTransactionTicket()
 516          * @param array $opts Options to waitForReplication()
 517          * @throws DBReplicationWaitError
 518          * @since 1.28
 519          */
 520         public function commitAndWaitForReplication( $fname, $ticket, array $opts = [] ) {
 521                 if ( $ticket !== $this->ticket ) {
 522                         $this->perfLogger->error( __METHOD__ . ": $fname does not have outer scope." );
 523                         return;
 524                 }
 525
 526                 // The transaction owner and any caller with the empty transaction ticket can commit
 527                 // so that getEmptyTransactionTicket() callers don't risk seeing DBTransactionError.
 528                 if ( $this->trxRoundId !== false && $fname !== $this->trxRoundId ) {
 529                         $this->queryLogger->info( "$fname: committing on behalf of {$this->trxRoundId}." );
 530                         $fnameEffective = $this->trxRoundId;
 531                 } else {
 532                         $fnameEffective = $fname;
 533                 }
 534
 535                 $this->commitMasterChanges( $fnameEffective );
 536                 $this->waitForReplication( $opts );
 537                 // If a nested caller committed on behalf of $fname, start another empty $fname
 538                 // transaction, leaving the caller with the same empty transaction state as before.
 539                 if ( $fnameEffective !== $fname ) {
 540                         $this->beginMasterChanges( $fnameEffective );
 541                 }
 542         }
 543
 544         /**
 545          * @param string $dbName DB master name (e.g. "db1052")
 546          * @return float|bool UNIX timestamp when client last touched the DB or false if not recent
 547          * @since 1.28
 548          */
 549         public function getChronologyProtectorTouched( $dbName ) {
 550                 return $this->getChronologyProtector()->getTouched( $dbName );
 551         }
 552
 553         /**
 554          * Disable the ChronologyProtector for all load balancers
 555          *
 556          * This can be called at the start of special API entry points
 557          *
 558          * @since 1.27
 559          */
 560         public function disableChronologyProtection() {
 561                 $this->getChronologyProtector()->setEnabled( false );
 562         }
 563
 564         /**
 565          * @return ChronologyProtector
 566          */
 567         protected function getChronologyProtector() {
 568                 if ( $this->chronProt ) {
 569                         return $this->chronProt;
 570                 }
 571
 572                 $this->chronProt = new ChronologyProtector(
 573                         $this->memCache,
 574                         [
 575                                 'ip' => $this->requestInfo['IPAddress'],
 576                                 'agent' => $this->requestInfo['UserAgent'],
 577                         ],
 578                         isset( $_GET['cpPosTime'] ) ? $_GET['cpPosTime'] : null
 579                 );
 580                 $this->chronProt->setLogger( $this->replLogger );
 581
 582                 if ( $this->cliMode ) {
 583                         $this->chronProt->setEnabled( false );
 584                 } elseif ( $this->requestInfo['ChronologyProtection'] === 'false' ) {
 585                         // Request opted out of using position wait logic. This is useful for requests
 586                         // done by the job queue or background ETL that do not have a meaningful session.
 587                         $this->chronProt->setWaitEnabled( false );
 588                 }
 589
 590                 $this->replLogger->debug( __METHOD__ . ': using request info ' .
 591                         json_encode( $this->requestInfo, JSON_PRETTY_PRINT ) );
 592
 593                 return $this->chronProt;
 594         }
 595
 596         /**
 597          * Get and record all of the staged DB positions into persistent memory storage
 598          *
 599          * @param ChronologyProtector $cp
 600          * @param callable|null $workCallback Work to do instead of waiting on syncing positions
 601          * @param string $mode One of (sync, async); whether to wait on remote datacenters
 602          */
 603         protected function shutdownChronologyProtector(
 604                 ChronologyProtector $cp, $workCallback, $mode
 605         ) {
 606                 // Record all the master positions needed
 607                 $this->forEachLB( function ( ILoadBalancer $lb ) use ( $cp ) {
 608                         $cp->shutdownLB( $lb );
 609                 } );
 610                 // Write them to the persistent stash. Try to do something useful by running $work
 611                 // while ChronologyProtector waits for the stash write to replicate to all DCs.
 612                 $unsavedPositions = $cp->shutdown( $workCallback, $mode );
 613                 if ( $unsavedPositions && $workCallback ) {
 614                         // Invoke callback in case it did not cache the result yet
 615                         $workCallback(); // work now to block for less time in waitForAll()
 616                 }
 617                 // If the positions failed to write to the stash, at least wait on local datacenter
 618                 // replica DBs to catch up before responding. Even if there are several DCs, this increases
 619                 // the chance that the user will see their own changes immediately afterwards. As long
 620                 // as the sticky DC cookie applies (same domain), this is not even an issue.
 621                 $this->forEachLB( function ( ILoadBalancer $lb ) use ( $unsavedPositions ) {
 622                         $masterName = $lb->getServerName( $lb->getWriterIndex() );
 623                         if ( isset( $unsavedPositions[$masterName] ) ) {
 624                                 $lb->waitForAll( $unsavedPositions[$masterName] );
 625                         }
 626                 } );
 627         }
 628
 629         /**
 630          * Base parameters to LoadBalancer::__construct()
 631          * @return array
 632          */
 633         final protected function baseLoadBalancerParams() {
 634                 return [
 635                         'localDomain' => $this->localDomain,
 636                         'readOnlyReason' => $this->readOnlyReason,
 637                         'srvCache' => $this->srvCache,
 638                         'wanCache' => $this->wanCache,
 639                         'profiler' => $this->profiler,
 640                         'trxProfiler' => $this->trxProfiler,
 641                         'queryLogger' => $this->queryLogger,
 642                         'connLogger' => $this->connLogger,
 643                         'replLogger' => $this->replLogger,
 644                         'errorLogger' => $this->errorLogger,
 645                         'hostname' => $this->hostname,
 646                         'cliMode' => $this->cliMode,
 647                         'agent' => $this->agent
 648                 ];
 649         }
 650
 651         /**
 652          * @param ILoadBalancer $lb
 653          */
 654         protected function initLoadBalancer( ILoadBalancer $lb ) {
 655                 if ( $this->trxRoundId !== false ) {
 656                         $lb->beginMasterChanges( $this->trxRoundId ); // set DBO_TRX
 657                 }
 658         }
 659
 660         /**
 661          * Set a new table prefix for the existing local domain ID for testing
 662          *
 663          * @param string $prefix
 664          * @since 1.28
 665          */
 666         public function setDomainPrefix( $prefix ) {
 667                 $this->localDomain = new DatabaseDomain(
 668                         $this->localDomain->getDatabase(),
 669                         null,
 670                         $prefix
 671                 );
 672
 673                 $this->forEachLB( function( LoadBalancer $lb ) use ( $prefix ) {
 674                         $lb->setDomainPrefix( $prefix );
 675                 } );
 676         }
 677
 678         /**
 679          * Close all open database connections on all open load balancers.
 680          * @since 1.28
 681          */
 682         public function closeAll() {
 683                 $this->forEachLBCallMethod( 'closeAll', [] );
 684         }
 685
 686         /**
 687          * @param string $agent Agent name for query profiling
 688          * @since 1.28
 689          */
 690         public function setAgentName( $agent ) {
 691                 $this->agent = $agent;
 692         }
 693
 694         /**
 695          * Append ?cpPosTime parameter to a URL for ChronologyProtector purposes if needed
 696          *
 697          * Note that unlike cookies, this works accross domains
 698          *
 699          * @param string $url
 700          * @param float $time UNIX timestamp just before shutdown() was called
 701          * @return string
 702          * @since 1.28
 703          */
 704         public function appendPreShutdownTimeAsQuery( $url, $time ) {
 705                 $usedCluster = 0;
 706                 $this->forEachLB( function ( ILoadBalancer $lb ) use ( &$usedCluster ) {
 707                         $usedCluster |= ( $lb->getServerCount() > 1 );
 708                 } );
 709
 710                 if ( !$usedCluster ) {
 711                         return $url; // no master/replica clusters touched
 712                 }
 713
 714                 return strpos( $url, '?' ) === false ? "$url?cpPosTime=$time" : "$url&cpPosTime=$time";
 715         }
 716
 717         /**
 718          * @param array $info Map of fields, including:
 719          *   - IPAddress : IP address
 720          *   - UserAgent : User-Agent HTTP header
 721          *   - ChronologyProtection : cookie/header value specifying ChronologyProtector usage
 722          * @since 1.28
 723          */
 724         public function setRequestInfo( array $info ) {
 725                 $this->requestInfo = $info + $this->requestInfo;
 726         }
 727
 728         function __destruct() {
 729                 $this->destroy();
 730         }
 731 }