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          * Construct a manager of ILoadBalancer objects
  84          *
  85          * Sub-classes will extend the required keys in $conf with additional parameters
  86          *
  87          * @param $conf $params Array with keys:
  88          *  - localDomain: A DatabaseDomain or domain ID string.
  89          *  - readOnlyReason : Reason the master DB is read-only if so [optional]
  90          *  - srvCache : BagOStuff object for server cache [optional]
  91          *  - memCache : BagOStuff object for cluster memory cache [optional]
  92          *  - wanCache : WANObjectCache object [optional]
  93          *  - hostname : The name of the current server [optional]
  94          *  - cliMode: Whether the execution context is a CLI script. [optional]
  95          *  - profiler : Class name or instance with profileIn()/profileOut() methods. [optional]
  96          *  - trxProfiler: TransactionProfiler instance. [optional]
  97          *  - replLogger: PSR-3 logger instance. [optional]
  98          *  - connLogger: PSR-3 logger instance. [optional]
  99          *  - queryLogger: PSR-3 logger instance. [optional]
 100          *  - perfLogger: PSR-3 logger instance. [optional]
 101          *  - errorLogger : Callback that takes an Exception and logs it. [optional]
 102          * @throws InvalidArgumentException
 103          */
 104         public function __construct( array $conf ) {
 105                 $this->localDomain = isset( $conf['localDomain'] )
 106                         ? DatabaseDomain::newFromId( $conf['localDomain'] )
 107                         : DatabaseDomain::newUnspecified();
 108
 109                 if ( isset( $conf['readOnlyReason'] ) && is_string( $conf['readOnlyReason'] ) ) {
 110                         $this->readOnlyReason = $conf['readOnlyReason'];
 111                 }
 112
 113                 $this->srvCache = isset( $conf['srvCache'] ) ? $conf['srvCache'] : new EmptyBagOStuff();
 114                 $this->memCache = isset( $conf['memCache'] ) ? $conf['memCache'] : new EmptyBagOStuff();
 115                 $this->wanCache = isset( $conf['wanCache'] )
 116                         ? $conf['wanCache']
 117                         : WANObjectCache::newEmpty();
 118
 119                 foreach ( self::$loggerFields as $key ) {
 120                         $this->$key = isset( $conf[$key] ) ? $conf[$key] : new \Psr\Log\NullLogger();
 121                 }
 122                 $this->errorLogger = isset( $conf['errorLogger'] )
 123                         ? $conf['errorLogger']
 124                         : function ( Exception $e ) {
 125                                 trigger_error( E_WARNING, get_class( $e ) . ': ' . $e->getMessage() );
 126                         };
 127
 128                 $this->profiler = isset( $params['profiler'] ) ? $params['profiler'] : null;
 129                 $this->trxProfiler = isset( $conf['trxProfiler'] )
 130                         ? $conf['trxProfiler']
 131                         : new TransactionProfiler();
 132
 133                 $this->requestInfo = [
 134                         'IPAddress' => isset( $_SERVER[ 'REMOTE_ADDR' ] ) ? $_SERVER[ 'REMOTE_ADDR' ] : '',
 135                         'UserAgent' => isset( $_SERVER['HTTP_USER_AGENT'] ) ? $_SERVER['HTTP_USER_AGENT'] : '',
 136                         'ChronologyProtection' => 'true'
 137                 ];
 138
 139                 $this->cliMode = isset( $params['cliMode'] ) ? $params['cliMode'] : PHP_SAPI === 'cli';
 140                 $this->hostname = isset( $conf['hostname'] ) ? $conf['hostname'] : gethostname();
 141                 $this->agent = isset( $params['agent'] ) ? $params['agent'] : '';
 142
 143                 $this->ticket = mt_rand();
 144         }
 145
 146         /**
 147          * Disables all load balancers. All connections are closed, and any attempt to
 148          * open a new connection will result in a DBAccessError.
 149          * @see ILoadBalancer::disable()
 150          */
 151         public function destroy() {
 152                 $this->shutdown( self::SHUTDOWN_NO_CHRONPROT );
 153                 $this->forEachLBCallMethod( 'disable' );
 154         }
 155
 156         /**
 157          * Create a new load balancer object. The resulting object will be untracked,
 158          * not chronology-protected, and the caller is responsible for cleaning it up.
 159          *
 160          * @param bool|string $domain Domain ID, or false for the current domain
 161          * @return ILoadBalancer
 162          */
 163         abstract public function newMainLB( $domain = false );
 164
 165         /**
 166          * Get a cached (tracked) load balancer object.
 167          *
 168          * @param bool|string $domain Domain ID, or false for the current domain
 169          * @return ILoadBalancer
 170          */
 171         abstract public function getMainLB( $domain = false );
 172
 173         /**
 174          * Create a new load balancer for external storage. The resulting object will be
 175          * untracked, not chronology-protected, and the caller is responsible for
 176          * cleaning it up.
 177          *
 178          * @param string $cluster External storage cluster, or false for core
 179          * @param bool|string $domain Domain ID, or false for the current domain
 180          * @return ILoadBalancer
 181          */
 182         abstract protected function newExternalLB( $cluster, $domain = false );
 183
 184         /**
 185          * Get a cached (tracked) load balancer for external storage
 186          *
 187          * @param string $cluster External storage cluster, or false for core
 188          * @param bool|string $domain Domain ID, or false for the current domain
 189          * @return ILoadBalancer
 190          */
 191         abstract public function getExternalLB( $cluster, $domain = false );
 192
 193         /**
 194          * Execute a function for each tracked load balancer
 195          * The callback is called with the load balancer as the first parameter,
 196          * and $params passed as the subsequent parameters.
 197          *
 198          * @param callable $callback
 199          * @param array $params
 200          */
 201         abstract public function forEachLB( $callback, array $params = [] );
 202
 203         /**
 204          * Prepare all tracked load balancers for shutdown
 205          * @param integer $mode One of the class SHUTDOWN_* constants
 206          * @param callable|null $workCallback Work to mask ChronologyProtector writes
 207          */
 208         public function shutdown(
 209                 $mode = self::SHUTDOWN_CHRONPROT_SYNC, callable $workCallback = null
 210         ) {
 211                 $chronProt = $this->getChronologyProtector();
 212                 if ( $mode === self::SHUTDOWN_CHRONPROT_SYNC ) {
 213                         $this->shutdownChronologyProtector( $chronProt, $workCallback, 'sync' );
 214                 } elseif ( $mode === self::SHUTDOWN_CHRONPROT_ASYNC ) {
 215                         $this->shutdownChronologyProtector( $chronProt, null, 'async' );
 216                 }
 217
 218                 $this->commitMasterChanges( __METHOD__ ); // sanity
 219         }
 220
 221         /**
 222          * Call a method of each tracked load balancer
 223          *
 224          * @param string $methodName
 225          * @param array $args
 226          */
 227         protected function forEachLBCallMethod( $methodName, array $args = [] ) {
 228                 $this->forEachLB(
 229                         function ( ILoadBalancer $loadBalancer, $methodName, array $args ) {
 230                                 call_user_func_array( [ $loadBalancer, $methodName ], $args );
 231                         },
 232                         [ $methodName, $args ]
 233                 );
 234         }
 235
 236         /**
 237          * Commit all replica DB transactions so as to flush any REPEATABLE-READ or SSI snapshot
 238          *
 239          * @param string $fname Caller name
 240          * @since 1.28
 241          */
 242         public function flushReplicaSnapshots( $fname = __METHOD__ ) {
 243                 $this->forEachLBCallMethod( 'flushReplicaSnapshots', [ $fname ] );
 244         }
 245
 246         /**
 247          * Commit on all connections. Done for two reasons:
 248          * 1. To commit changes to the masters.
 249          * 2. To release the snapshot on all connections, master and replica DB.
 250          * @param string $fname Caller name
 251          * @param array $options Options map:
 252          *   - maxWriteDuration: abort if more than this much time was spent in write queries
 253          */
 254         public function commitAll( $fname = __METHOD__, array $options = [] ) {
 255                 $this->commitMasterChanges( $fname, $options );
 256                 $this->forEachLBCallMethod( 'commitAll', [ $fname ] );
 257         }
 258
 259         /**
 260          * Flush any master transaction snapshots and set DBO_TRX (if DBO_DEFAULT is set)
 261          *
 262          * The DBO_TRX setting will be reverted to the default in each of these methods:
 263          *   - commitMasterChanges()
 264          *   - rollbackMasterChanges()
 265          *   - commitAll()
 266          *
 267          * This allows for custom transaction rounds from any outer transaction scope.
 268          *
 269          * @param string $fname
 270          * @throws DBTransactionError
 271          * @since 1.28
 272          */
 273         public function beginMasterChanges( $fname = __METHOD__ ) {
 274                 if ( $this->trxRoundId !== false ) {
 275                         throw new DBTransactionError(
 276                                 null,
 277                                 "$fname: transaction round '{$this->trxRoundId}' already started."
 278                         );
 279                 }
 280                 $this->trxRoundId = $fname;
 281                 // Set DBO_TRX flags on all appropriate DBs
 282                 $this->forEachLBCallMethod( 'beginMasterChanges', [ $fname ] );
 283         }
 284
 285         /**
 286          * Commit changes on all master connections
 287          * @param string $fname Caller name
 288          * @param array $options Options map:
 289          *   - maxWriteDuration: abort if more than this much time was spent in write queries
 290          * @throws Exception
 291          */
 292         public function commitMasterChanges( $fname = __METHOD__, array $options = [] ) {
 293                 if ( $this->trxRoundId !== false && $this->trxRoundId !== $fname ) {
 294                         throw new DBTransactionError(
 295                                 null,
 296                                 "$fname: transaction round '{$this->trxRoundId}' still running."
 297                         );
 298                 }
 299                 // Run pre-commit callbacks and suppress post-commit callbacks, aborting on failure
 300                 $this->forEachLBCallMethod( 'finalizeMasterChanges' );
 301                 $this->trxRoundId = false;
 302                 // Perform pre-commit checks, aborting on failure
 303                 $this->forEachLBCallMethod( 'approveMasterChanges', [ $options ] );
 304                 // Log the DBs and methods involved in multi-DB transactions
 305                 $this->logIfMultiDbTransaction();
 306                 // Actually perform the commit on all master DB connections and revert DBO_TRX
 307                 $this->forEachLBCallMethod( 'commitMasterChanges', [ $fname ] );
 308                 // Run all post-commit callbacks
 309                 /** @var Exception $e */
 310                 $e = null; // first callback exception
 311                 $this->forEachLB( function ( ILoadBalancer $lb ) use ( &$e ) {
 312                         $ex = $lb->runMasterPostTrxCallbacks( IDatabase::TRIGGER_COMMIT );
 313                         $e = $e ?: $ex;
 314                 } );
 315                 // Commit any dangling DBO_TRX transactions from callbacks on one DB to another DB
 316                 $this->forEachLBCallMethod( 'commitMasterChanges', [ $fname ] );
 317                 // Throw any last post-commit callback error
 318                 if ( $e instanceof Exception ) {
 319                         throw $e;
 320                 }
 321         }
 322
 323         /**
 324          * Rollback changes on all master connections
 325          * @param string $fname Caller name
 326          * @since 1.23
 327          */
 328         public function rollbackMasterChanges( $fname = __METHOD__ ) {
 329                 $this->trxRoundId = false;
 330                 $this->forEachLBCallMethod( 'suppressTransactionEndCallbacks' );
 331                 $this->forEachLBCallMethod( 'rollbackMasterChanges', [ $fname ] );
 332                 // Run all post-rollback callbacks
 333                 $this->forEachLB( function ( ILoadBalancer $lb ) {
 334                         $lb->runMasterPostTrxCallbacks( IDatabase::TRIGGER_ROLLBACK );
 335                 } );
 336         }
 337
 338         /**
 339          * Log query info if multi DB transactions are going to be committed now
 340          */
 341         private function logIfMultiDbTransaction() {
 342                 $callersByDB = [];
 343                 $this->forEachLB( function ( ILoadBalancer $lb ) use ( &$callersByDB ) {
 344                         $masterName = $lb->getServerName( $lb->getWriterIndex() );
 345                         $callers = $lb->pendingMasterChangeCallers();
 346                         if ( $callers ) {
 347                                 $callersByDB[$masterName] = $callers;
 348                         }
 349                 } );
 350
 351                 if ( count( $callersByDB ) >= 2 ) {
 352                         $dbs = implode( ', ', array_keys( $callersByDB ) );
 353                         $msg = "Multi-DB transaction [{$dbs}]:\n";
 354                         foreach ( $callersByDB as $db => $callers ) {
 355                                 $msg .= "$db: " . implode( '; ', $callers ) . "\n";
 356                         }
 357                         $this->queryLogger->info( $msg );
 358                 }
 359         }
 360
 361         /**
 362          * Determine if any master connection has pending changes
 363          * @return bool
 364          * @since 1.23
 365          */
 366         public function hasMasterChanges() {
 367                 $ret = false;
 368                 $this->forEachLB( function ( ILoadBalancer $lb ) use ( &$ret ) {
 369                         $ret = $ret || $lb->hasMasterChanges();
 370                 } );
 371
 372                 return $ret;
 373         }
 374
 375         /**
 376          * Detemine if any lagged replica DB connection was used
 377          * @return bool
 378          * @since 1.28
 379          */
 380         public function laggedReplicaUsed() {
 381                 $ret = false;
 382                 $this->forEachLB( function ( ILoadBalancer $lb ) use ( &$ret ) {
 383                         $ret = $ret || $lb->laggedReplicaUsed();
 384                 } );
 385
 386                 return $ret;
 387         }
 388
 389         /**
 390          * Determine if any master connection has pending/written changes from this request
 391          * @param float $age How many seconds ago is "recent" [defaults to LB lag wait timeout]
 392          * @return bool
 393          * @since 1.27
 394          */
 395         public function hasOrMadeRecentMasterChanges( $age = null ) {
 396                 $ret = false;
 397                 $this->forEachLB( function ( ILoadBalancer $lb ) use ( $age, &$ret ) {
 398                         $ret = $ret || $lb->hasOrMadeRecentMasterChanges( $age );
 399                 } );
 400                 return $ret;
 401         }
 402
 403         /**
 404          * Waits for the replica DBs to catch up to the current master position
 405          *
 406          * Use this when updating very large numbers of rows, as in maintenance scripts,
 407          * to avoid causing too much lag. Of course, this is a no-op if there are no replica DBs.
 408          *
 409          * By default this waits on all DB clusters actually used in this request.
 410          * This makes sense when lag being waiting on is caused by the code that does this check.
 411          * In that case, setting "ifWritesSince" can avoid the overhead of waiting for clusters
 412          * that were not changed since the last wait check. To forcefully wait on a specific cluster
 413          * for a given domain, use the 'domain' parameter. To forcefully wait on an "external" cluster,
 414          * use the "cluster" parameter.
 415          *
 416          * Never call this function after a large DB write that is *still* in a transaction.
 417          * It only makes sense to call this after the possible lag inducing changes were committed.
 418          *
 419          * @param array $opts Optional fields that include:
 420          *   - domain : wait on the load balancer DBs that handles the given domain ID
 421          *   - cluster : wait on the given external load balancer DBs
 422          *   - timeout : Max wait time. Default: ~60 seconds
 423          *   - ifWritesSince: Only wait if writes were done since this UNIX timestamp
 424          * @throws DBReplicationWaitError If a timeout or error occured waiting on a DB cluster
 425          * @since 1.27
 426          */
 427         public function waitForReplication( array $opts = [] ) {
 428                 $opts += [
 429                         'domain' => false,
 430                         'cluster' => false,
 431                         'timeout' => 60,
 432                         'ifWritesSince' => null
 433                 ];
 434
 435                 if ( $opts['domain'] === false && isset( $opts['wiki'] ) ) {
 436                         $opts['domain'] = $opts['wiki']; // b/c
 437                 }
 438
 439                 // Figure out which clusters need to be checked
 440                 /** @var ILoadBalancer[] $lbs */
 441                 $lbs = [];
 442                 if ( $opts['cluster'] !== false ) {
 443                         $lbs[] = $this->getExternalLB( $opts['cluster'] );
 444                 } elseif ( $opts['domain'] !== false ) {
 445                         $lbs[] = $this->getMainLB( $opts['domain'] );
 446                 } else {
 447                         $this->forEachLB( function ( ILoadBalancer $lb ) use ( &$lbs ) {
 448                                 $lbs[] = $lb;
 449                         } );
 450                         if ( !$lbs ) {
 451                                 return; // nothing actually used
 452                         }
 453                 }
 454
 455                 // Get all the master positions of applicable DBs right now.
 456                 // This can be faster since waiting on one cluster reduces the
 457                 // time needed to wait on the next clusters.
 458                 $masterPositions = array_fill( 0, count( $lbs ), false );
 459                 foreach ( $lbs as $i => $lb ) {
 460                         if ( $lb->getServerCount() <= 1 ) {
 461                                 // Bug 27975 - Don't try to wait for replica DBs if there are none
 462                                 // Prevents permission error when getting master position
 463                                 continue;
 464                         } elseif ( $opts['ifWritesSince']
 465                                 && $lb->lastMasterChangeTimestamp() < $opts['ifWritesSince']
 466                         ) {
 467                                 continue; // no writes since the last wait
 468                         }
 469                         $masterPositions[$i] = $lb->getMasterPos();
 470                 }
 471
 472                 // Run any listener callbacks *after* getting the DB positions. The more
 473                 // time spent in the callbacks, the less time is spent in waitForAll().
 474                 foreach ( $this->replicationWaitCallbacks as $callback ) {
 475                         $callback();
 476                 }
 477
 478                 $failed = [];
 479                 foreach ( $lbs as $i => $lb ) {
 480                         if ( $masterPositions[$i] ) {
 481                                 // The DBMS may not support getMasterPos()
 482                                 if ( !$lb->waitForAll( $masterPositions[$i], $opts['timeout'] ) ) {
 483                                         $failed[] = $lb->getServerName( $lb->getWriterIndex() );
 484                                 }
 485                         }
 486                 }
 487
 488                 if ( $failed ) {
 489                         throw new DBReplicationWaitError(
 490                                 "Could not wait for replica DBs to catch up to " .
 491                                 implode( ', ', $failed )
 492                         );
 493                 }
 494         }
 495
 496         /**
 497          * Add a callback to be run in every call to waitForReplication() before waiting
 498          *
 499          * Callbacks must clear any transactions that they start
 500          *
 501          * @param string $name Callback name
 502          * @param callable|null $callback Use null to unset a callback
 503          * @since 1.28
 504          */
 505         public function setWaitForReplicationListener( $name, callable $callback = null ) {
 506                 if ( $callback ) {
 507                         $this->replicationWaitCallbacks[$name] = $callback;
 508                 } else {
 509                         unset( $this->replicationWaitCallbacks[$name] );
 510                 }
 511         }
 512
 513         /**
 514          * Get a token asserting that no transaction writes are active
 515          *
 516          * @param string $fname Caller name (e.g. __METHOD__)
 517          * @return mixed A value to pass to commitAndWaitForReplication()
 518          * @since 1.28
 519          */
 520         public function getEmptyTransactionTicket( $fname ) {
 521                 if ( $this->hasMasterChanges() ) {
 522                         $this->queryLogger->error( __METHOD__ . ": $fname does not have outer scope." );
 523                         return null;
 524                 }
 525
 526                 return $this->ticket;
 527         }
 528
 529         /**
 530          * Convenience method for safely running commitMasterChanges()/waitForReplication()
 531          *
 532          * This will commit and wait unless $ticket indicates it is unsafe to do so
 533          *
 534          * @param string $fname Caller name (e.g. __METHOD__)
 535          * @param mixed $ticket Result of getEmptyTransactionTicket()
 536          * @param array $opts Options to waitForReplication()
 537          * @throws DBReplicationWaitError
 538          * @since 1.28
 539          */
 540         public function commitAndWaitForReplication( $fname, $ticket, array $opts = [] ) {
 541                 if ( $ticket !== $this->ticket ) {
 542                         $this->perfLogger->error( __METHOD__ . ": $fname does not have outer scope." );
 543                         return;
 544                 }
 545
 546                 // The transaction owner and any caller with the empty transaction ticket can commit
 547                 // so that getEmptyTransactionTicket() callers don't risk seeing DBTransactionError.
 548                 if ( $this->trxRoundId !== false && $fname !== $this->trxRoundId ) {
 549                         $this->queryLogger->info( "$fname: committing on behalf of {$this->trxRoundId}." );
 550                         $fnameEffective = $this->trxRoundId;
 551                 } else {
 552                         $fnameEffective = $fname;
 553                 }
 554
 555                 $this->commitMasterChanges( $fnameEffective );
 556                 $this->waitForReplication( $opts );
 557                 // If a nested caller committed on behalf of $fname, start another empty $fname
 558                 // transaction, leaving the caller with the same empty transaction state as before.
 559                 if ( $fnameEffective !== $fname ) {
 560                         $this->beginMasterChanges( $fnameEffective );
 561                 }
 562         }
 563
 564         /**
 565          * @param string $dbName DB master name (e.g. "db1052")
 566          * @return float|bool UNIX timestamp when client last touched the DB or false if not recent
 567          * @since 1.28
 568          */
 569         public function getChronologyProtectorTouched( $dbName ) {
 570                 return $this->getChronologyProtector()->getTouched( $dbName );
 571         }
 572
 573         /**
 574          * Disable the ChronologyProtector for all load balancers
 575          *
 576          * This can be called at the start of special API entry points
 577          *
 578          * @since 1.27
 579          */
 580         public function disableChronologyProtection() {
 581                 $this->getChronologyProtector()->setEnabled( false );
 582         }
 583
 584         /**
 585          * @return ChronologyProtector
 586          */
 587         protected function getChronologyProtector() {
 588                 if ( $this->chronProt ) {
 589                         return $this->chronProt;
 590                 }
 591
 592                 $this->chronProt = new ChronologyProtector(
 593                         $this->memCache,
 594                         [
 595                                 'ip' => $this->requestInfo['IPAddress'],
 596                                 'agent' => $this->requestInfo['UserAgent'],
 597                         ],
 598                         isset( $_GET['cpPosTime'] ) ? $_GET['cpPosTime'] : null
 599                 );
 600                 $this->chronProt->setLogger( $this->replLogger );
 601
 602                 if ( $this->cliMode ) {
 603                         $this->chronProt->setEnabled( false );
 604                 } elseif ( $this->requestInfo['ChronologyProtection'] === 'false' ) {
 605                         // Request opted out of using position wait logic. This is useful for requests
 606                         // done by the job queue or background ETL that do not have a meaningful session.
 607                         $this->chronProt->setWaitEnabled( false );
 608                 }
 609
 610                 $this->replLogger->debug( __METHOD__ . ': using request info ' .
 611                         json_encode( $this->requestInfo, JSON_PRETTY_PRINT ) );
 612
 613                 return $this->chronProt;
 614         }
 615
 616         /**
 617          * Get and record all of the staged DB positions into persistent memory storage
 618          *
 619          * @param ChronologyProtector $cp
 620          * @param callable|null $workCallback Work to do instead of waiting on syncing positions
 621          * @param string $mode One of (sync, async); whether to wait on remote datacenters
 622          */
 623         protected function shutdownChronologyProtector(
 624                 ChronologyProtector $cp, $workCallback, $mode
 625         ) {
 626                 // Record all the master positions needed
 627                 $this->forEachLB( function ( ILoadBalancer $lb ) use ( $cp ) {
 628                         $cp->shutdownLB( $lb );
 629                 } );
 630                 // Write them to the persistent stash. Try to do something useful by running $work
 631                 // while ChronologyProtector waits for the stash write to replicate to all DCs.
 632                 $unsavedPositions = $cp->shutdown( $workCallback, $mode );
 633                 if ( $unsavedPositions && $workCallback ) {
 634                         // Invoke callback in case it did not cache the result yet
 635                         $workCallback(); // work now to block for less time in waitForAll()
 636                 }
 637                 // If the positions failed to write to the stash, at least wait on local datacenter
 638                 // replica DBs to catch up before responding. Even if there are several DCs, this increases
 639                 // the chance that the user will see their own changes immediately afterwards. As long
 640                 // as the sticky DC cookie applies (same domain), this is not even an issue.
 641                 $this->forEachLB( function ( ILoadBalancer $lb ) use ( $unsavedPositions ) {
 642                         $masterName = $lb->getServerName( $lb->getWriterIndex() );
 643                         if ( isset( $unsavedPositions[$masterName] ) ) {
 644                                 $lb->waitForAll( $unsavedPositions[$masterName] );
 645                         }
 646                 } );
 647         }
 648
 649         /**
 650          * Base parameters to LoadBalancer::__construct()
 651          * @return array
 652          */
 653         final protected function baseLoadBalancerParams() {
 654                 return [
 655                         'localDomain' => $this->localDomain,
 656                         'readOnlyReason' => $this->readOnlyReason,
 657                         'srvCache' => $this->srvCache,
 658                         'wanCache' => $this->wanCache,
 659                         'profiler' => $this->profiler,
 660                         'trxProfiler' => $this->trxProfiler,
 661                         'queryLogger' => $this->queryLogger,
 662                         'connLogger' => $this->connLogger,
 663                         'replLogger' => $this->replLogger,
 664                         'errorLogger' => $this->errorLogger,
 665                         'hostname' => $this->hostname,
 666                         'cliMode' => $this->cliMode,
 667                         'agent' => $this->agent
 668                 ];
 669         }
 670
 671         /**
 672          * @param ILoadBalancer $lb
 673          */
 674         protected function initLoadBalancer( ILoadBalancer $lb ) {
 675                 if ( $this->trxRoundId !== false ) {
 676                         $lb->beginMasterChanges( $this->trxRoundId ); // set DBO_TRX
 677                 }
 678         }
 679
 680         /**
 681          * Set a new table prefix for the existing local domain ID for testing
 682          *
 683          * @param string $prefix
 684          * @since 1.28
 685          */
 686         public function setDomainPrefix( $prefix ) {
 687                 $this->localDomain = new DatabaseDomain(
 688                         $this->localDomain->getDatabase(),
 689                         null,
 690                         $prefix
 691                 );
 692
 693                 $this->forEachLB( function( ILoadBalancer $lb ) use ( $prefix ) {
 694                         $lb->setDomainPrefix( $prefix );
 695                 } );
 696         }
 697
 698         /**
 699          * Close all open database connections on all open load balancers.
 700          * @since 1.28
 701          */
 702         public function closeAll() {
 703                 $this->forEachLBCallMethod( 'closeAll', [] );
 704         }
 705
 706         /**
 707          * @param string $agent Agent name for query profiling
 708          * @since 1.28
 709          */
 710         public function setAgentName( $agent ) {
 711                 $this->agent = $agent;
 712         }
 713
 714         /**
 715          * Append ?cpPosTime parameter to a URL for ChronologyProtector purposes if needed
 716          *
 717          * Note that unlike cookies, this works accross domains
 718          *
 719          * @param string $url
 720          * @param float $time UNIX timestamp just before shutdown() was called
 721          * @return string
 722          * @since 1.28
 723          */
 724         public function appendPreShutdownTimeAsQuery( $url, $time ) {
 725                 $usedCluster = 0;
 726                 $this->forEachLB( function ( ILoadBalancer $lb ) use ( &$usedCluster ) {
 727                         $usedCluster |= ( $lb->getServerCount() > 1 );
 728                 } );
 729
 730                 if ( !$usedCluster ) {
 731                         return $url; // no master/replica clusters touched
 732                 }
 733
 734                 return strpos( $url, '?' ) === false ? "$url?cpPosTime=$time" : "$url&cpPosTime=$time";
 735         }
 736
 737         /**
 738          * @param array $info Map of fields, including:
 739          *   - IPAddress : IP address
 740          *   - UserAgent : User-Agent HTTP header
 741          *   - ChronologyProtection : cookie/header value specifying ChronologyProtector usage
 742          * @since 1.28
 743          */
 744         public function setRequestInfo( array $info ) {
 745                 $this->requestInfo = $info + $this->requestInfo;
 746         }
 747
 748         function __destruct() {
 749                 $this->destroy();
 750         }
 751 }