maintenance/storage/recompressTracked.php

   1 <?php
   2 /**
   3  * Moves blobs indexed by trackBlobs.php to a specified list of destination
   4  * clusters, and recompresses them in the process.
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License as published by
   8  * the Free Software Foundation; either version 2 of the License, or
   9  * (at your option) any later version.
  10  *
  11  * This program is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  14  * GNU General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU General Public License along
  17  * with this program; if not, write to the Free Software Foundation, Inc.,
  18  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  19  * http://www.gnu.org/copyleft/gpl.html
  20  *
  21  * @file
  22  * @ingroup Maintenance ExternalStorage
  23  */
  24
  25 use MediaWiki\Logger\LegacyLogger;
  26 use MediaWiki\MediaWikiServices;
  27
  28 $optionsWithArgs = RecompressTracked::getOptionsWithArgs();
  29 require __DIR__ . '/../commandLine.inc';
  30
  31 if ( count( $args ) < 1 ) {
  32         echo "Usage: php recompressTracked.php [options] <cluster> [... <cluster>...]
  33 Moves blobs indexed by trackBlobs.php to a specified list of destination clusters,
  34 and recompresses them in the process. Restartable.
  35
  36 Options:
  37         --procs <procs>       Set the number of child processes (default 1)
  38         --copy-only           Copy only, do not update the text table. Restart
  39                               without this option to complete.
  40         --debug-log <file>    Log debugging data to the specified file
  41         --info-log <file>     Log progress messages to the specified file
  42         --critical-log <file> Log error messages to the specified file
  43 ";
  44         exit( 1 );
  45 }
  46
  47 $job = RecompressTracked::newFromCommandLine( $args, $options );
  48 $job->execute();
  49
  50 /**
  51  * Maintenance script that moves blobs indexed by trackBlobs.php to a specified
  52  * list of destination clusters, and recompresses them in the process.
  53  *
  54  * @ingroup Maintenance ExternalStorage
  55  */
  56 class RecompressTracked {
  57         public $destClusters;
  58         public $batchSize = 1000;
  59         public $orphanBatchSize = 1000;
  60         public $reportingInterval = 10;
  61         public $numProcs = 1;
  62         public $numBatches = 0;
  63         public $pageBlobClass, $orphanBlobClass;
  64         public $replicaPipes, $replicaProcs, $prevReplicaId;
  65         public $copyOnly = false;
  66         public $isChild = false;
  67         public $replicaId = false;
  68         public $noCount = false;
  69         public $debugLog, $infoLog, $criticalLog;
  70         public $store;
  71
  72         private static $optionsWithArgs = [
  73                 'procs',
  74                 'replica-id',
  75                 'debug-log',
  76                 'info-log',
  77                 'critical-log'
  78         ];
  79
  80         private static $cmdLineOptionMap = [
  81                 'no-count' => 'noCount',
  82                 'procs' => 'numProcs',
  83                 'copy-only' => 'copyOnly',
  84                 'child' => 'isChild',
  85                 'replica-id' => 'replicaId',
  86                 'debug-log' => 'debugLog',
  87                 'info-log' => 'infoLog',
  88                 'critical-log' => 'criticalLog',
  89         ];
  90
  91         static function getOptionsWithArgs() {
  92                 return self::$optionsWithArgs;
  93         }
  94
  95         static function newFromCommandLine( $args, $options ) {
  96                 $jobOptions = [ 'destClusters' => $args ];
  97                 foreach ( self::$cmdLineOptionMap as $cmdOption => $classOption ) {
  98                         if ( isset( $options[$cmdOption] ) ) {
  99                                 $jobOptions[$classOption] = $options[$cmdOption];
 100                         }
 101                 }
 102
 103                 return new self( $jobOptions );
 104         }
 105
 106         function __construct( $options ) {
 107                 foreach ( $options as $name => $value ) {
 108                         $this->$name = $value;
 109                 }
 110                 $this->store = new ExternalStoreDB;
 111                 if ( !$this->isChild ) {
 112                         $GLOBALS['wgDebugLogPrefix'] = "RCT M: ";
 113                 } elseif ( $this->replicaId !== false ) {
 114                         $GLOBALS['wgDebugLogPrefix'] = "RCT {$this->replicaId}: ";
 115                 }
 116                 $this->pageBlobClass = function_exists( 'xdiff_string_bdiff' ) ?
 117                         'DiffHistoryBlob' : 'ConcatenatedGzipHistoryBlob';
 118                 $this->orphanBlobClass = 'ConcatenatedGzipHistoryBlob';
 119         }
 120
 121         function debug( $msg ) {
 122                 wfDebug( "$msg\n" );
 123                 if ( $this->debugLog ) {
 124                         $this->logToFile( $msg, $this->debugLog );
 125                 }
 126         }
 127
 128         function info( $msg ) {
 129                 echo "$msg\n";
 130                 if ( $this->infoLog ) {
 131                         $this->logToFile( $msg, $this->infoLog );
 132                 }
 133         }
 134
 135         function critical( $msg ) {
 136                 echo "$msg\n";
 137                 if ( $this->criticalLog ) {
 138                         $this->logToFile( $msg, $this->criticalLog );
 139                 }
 140         }
 141
 142         function logToFile( $msg, $file ) {
 143                 $header = '[' . date( 'd\TH:i:s' ) . '] ' . wfHostname() . ' ' . posix_getpid();
 144                 if ( $this->replicaId !== false ) {
 145                         $header .= "({$this->replicaId})";
 146                 }
 147                 $header .= ' ' . wfWikiID();
 148                 LegacyLogger::emit( sprintf( "%-50s %s\n", $header, $msg ), $file );
 149         }
 150
 151         /**
 152          * Wait until the selected replica DB has caught up to the master.
 153          * This allows us to use the replica DB for things that were committed in a
 154          * previous part of this batch process.
 155          */
 156         function syncDBs() {
 157                 $dbw = wfGetDB( DB_MASTER );
 158                 $dbr = wfGetDB( DB_REPLICA );
 159                 $pos = $dbw->getMasterPos();
 160                 $dbr->masterPosWait( $pos, 100000 );
 161         }
 162
 163         /**
 164          * Execute parent or child depending on the isChild option
 165          */
 166         function execute() {
 167                 if ( $this->isChild ) {
 168                         $this->executeChild();
 169                 } else {
 170                         $this->executeParent();
 171                 }
 172         }
 173
 174         /**
 175          * Execute the parent process
 176          */
 177         function executeParent() {
 178                 if ( !$this->checkTrackingTable() ) {
 179                         return;
 180                 }
 181
 182                 $this->syncDBs();
 183                 $this->startReplicaProcs();
 184                 $this->doAllPages();
 185                 $this->doAllOrphans();
 186                 $this->killReplicaProcs();
 187         }
 188
 189         /**
 190          * Make sure the tracking table exists and isn't empty
 191          * @return bool
 192          */
 193         function checkTrackingTable() {
 194                 $dbr = wfGetDB( DB_REPLICA );
 195                 if ( !$dbr->tableExists( 'blob_tracking' ) ) {
 196                         $this->critical( "Error: blob_tracking table does not exist" );
 197
 198                         return false;
 199                 }
 200                 $row = $dbr->selectRow( 'blob_tracking', '*', '', __METHOD__ );
 201                 if ( !$row ) {
 202                         $this->info( "Warning: blob_tracking table contains no rows, skipping this wiki." );
 203
 204                         return false;
 205                 }
 206
 207                 return true;
 208         }
 209
 210         /**
 211          * Start the worker processes.
 212          * These processes will listen on stdin for commands.
 213          * This necessary because text recompression is slow: loading, compressing and
 214          * writing are all slow.
 215          */
 216         function startReplicaProcs() {
 217                 $cmd = 'php ' . wfEscapeShellArg( __FILE__ );
 218                 foreach ( self::$cmdLineOptionMap as $cmdOption => $classOption ) {
 219                         if ( $cmdOption == 'replica-id' ) {
 220                                 continue;
 221                         } elseif ( in_array( $cmdOption, self::$optionsWithArgs ) && isset( $this->$classOption ) ) {
 222                                 $cmd .= " --$cmdOption " . wfEscapeShellArg( $this->$classOption );
 223                         } elseif ( $this->$classOption ) {
 224                                 $cmd .= " --$cmdOption";
 225                         }
 226                 }
 227                 $cmd .= ' --child' .
 228                         ' --wiki ' . wfEscapeShellArg( wfWikiID() ) .
 229                         ' ' . call_user_func_array( 'wfEscapeShellArg', $this->destClusters );
 230
 231                 $this->replicaPipes = $this->replicaProcs = [];
 232                 for ( $i = 0; $i < $this->numProcs; $i++ ) {
 233                         $pipes = [];
 234                         $spec = [
 235                                 [ 'pipe', 'r' ],
 236                                 [ 'file', 'php://stdout', 'w' ],
 237                                 [ 'file', 'php://stderr', 'w' ]
 238                         ];
 239                         MediaWiki\suppressWarnings();
 240                         $proc = proc_open( "$cmd --replica-id $i", $spec, $pipes );
 241                         MediaWiki\restoreWarnings();
 242                         if ( !$proc ) {
 243                                 $this->critical( "Error opening replica DB process: $cmd" );
 244                                 exit( 1 );
 245                         }
 246                         $this->replicaProcs[$i] = $proc;
 247                         $this->replicaPipes[$i] = $pipes[0];
 248                 }
 249                 $this->prevReplicaId = -1;
 250         }
 251
 252         /**
 253          * Gracefully terminate the child processes
 254          */
 255         function killReplicaProcs() {
 256                 $this->info( "Waiting for replica DB processes to finish..." );
 257                 for ( $i = 0; $i < $this->numProcs; $i++ ) {
 258                         $this->dispatchToReplica( $i, 'quit' );
 259                 }
 260                 for ( $i = 0; $i < $this->numProcs; $i++ ) {
 261                         $status = proc_close( $this->replicaProcs[$i] );
 262                         if ( $status ) {
 263                                 $this->critical( "Warning: child #$i exited with status $status" );
 264                         }
 265                 }
 266                 $this->info( "Done." );
 267         }
 268
 269         /**
 270          * Dispatch a command to the next available replica DB.
 271          * This may block until a replica DB finishes its work and becomes available.
 272          */
 273         function dispatch( /*...*/ ) {
 274                 $args = func_get_args();
 275                 $pipes = $this->replicaPipes;
 276                 $numPipes = stream_select( $x = [], $pipes, $y = [], 3600 );
 277                 if ( !$numPipes ) {
 278                         $this->critical( "Error waiting to write to replica DBs. Aborting" );
 279                         exit( 1 );
 280                 }
 281                 for ( $i = 0; $i < $this->numProcs; $i++ ) {
 282                         $replicaId = ( $i + $this->prevReplicaId + 1 ) % $this->numProcs;
 283                         if ( isset( $pipes[$replicaId] ) ) {
 284                                 $this->prevReplicaId = $replicaId;
 285                                 $this->dispatchToReplica( $replicaId, $args );
 286
 287                                 return;
 288                         }
 289                 }
 290                 $this->critical( "Unreachable" );
 291                 exit( 1 );
 292         }
 293
 294         /**
 295          * Dispatch a command to a specified replica DB
 296          * @param int $replicaId
 297          * @param array|string $args
 298          */
 299         function dispatchToReplica( $replicaId, $args ) {
 300                 $args = (array)$args;
 301                 $cmd = implode( ' ', $args );
 302                 fwrite( $this->replicaPipes[$replicaId], "$cmd\n" );
 303         }
 304
 305         /**
 306          * Move all tracked pages to the new clusters
 307          */
 308         function doAllPages() {
 309                 $dbr = wfGetDB( DB_REPLICA );
 310                 $i = 0;
 311                 $startId = 0;
 312                 if ( $this->noCount ) {
 313                         $numPages = '[unknown]';
 314                 } else {
 315                         $numPages = $dbr->selectField( 'blob_tracking',
 316                                 'COUNT(DISTINCT bt_page)',
 317                                 # A condition is required so that this query uses the index
 318                                 [ 'bt_moved' => 0 ],
 319                                 __METHOD__
 320                         );
 321                 }
 322                 if ( $this->copyOnly ) {
 323                         $this->info( "Copying pages..." );
 324                 } else {
 325                         $this->info( "Moving pages..." );
 326                 }
 327                 while ( true ) {
 328                         $res = $dbr->select( 'blob_tracking',
 329                                 [ 'bt_page' ],
 330                                 [
 331                                         'bt_moved' => 0,
 332                                         'bt_page > ' . $dbr->addQuotes( $startId )
 333                                 ],
 334                                 __METHOD__,
 335                                 [
 336                                         'DISTINCT',
 337                                         'ORDER BY' => 'bt_page',
 338                                         'LIMIT' => $this->batchSize,
 339                                 ]
 340                         );
 341                         if ( !$res->numRows() ) {
 342                                 break;
 343                         }
 344                         foreach ( $res as $row ) {
 345                                 $startId = $row->bt_page;
 346                                 $this->dispatch( 'doPage', $row->bt_page );
 347                                 $i++;
 348                         }
 349                         $this->report( 'pages', $i, $numPages );
 350                 }
 351                 $this->report( 'pages', $i, $numPages );
 352                 if ( $this->copyOnly ) {
 353                         $this->info( "All page copies queued." );
 354                 } else {
 355                         $this->info( "All page moves queued." );
 356                 }
 357         }
 358
 359         /**
 360          * Display a progress report
 361          * @param string $label
 362          * @param int $current
 363          * @param int $end
 364          */
 365         function report( $label, $current, $end ) {
 366                 $this->numBatches++;
 367                 if ( $current == $end || $this->numBatches >= $this->reportingInterval ) {
 368                         $this->numBatches = 0;
 369                         $this->info( "$label: $current / $end" );
 370                         MediaWikiServices::getInstance()->getDBLoadBalancerFactory()->waitForReplication();
 371                 }
 372         }
 373
 374         /**
 375          * Move all orphan text to the new clusters
 376          */
 377         function doAllOrphans() {
 378                 $dbr = wfGetDB( DB_REPLICA );
 379                 $startId = 0;
 380                 $i = 0;
 381                 if ( $this->noCount ) {
 382                         $numOrphans = '[unknown]';
 383                 } else {
 384                         $numOrphans = $dbr->selectField( 'blob_tracking',
 385                                 'COUNT(DISTINCT bt_text_id)',
 386                                 [ 'bt_moved' => 0, 'bt_page' => 0 ],
 387                                 __METHOD__ );
 388                         if ( !$numOrphans ) {
 389                                 return;
 390                         }
 391                 }
 392                 if ( $this->copyOnly ) {
 393                         $this->info( "Copying orphans..." );
 394                 } else {
 395                         $this->info( "Moving orphans..." );
 396                 }
 397
 398                 while ( true ) {
 399                         $res = $dbr->select( 'blob_tracking',
 400                                 [ 'bt_text_id' ],
 401                                 [
 402                                         'bt_moved' => 0,
 403                                         'bt_page' => 0,
 404                                         'bt_text_id > ' . $dbr->addQuotes( $startId )
 405                                 ],
 406                                 __METHOD__,
 407                                 [
 408                                         'DISTINCT',
 409                                         'ORDER BY' => 'bt_text_id',
 410                                         'LIMIT' => $this->batchSize
 411                                 ]
 412                         );
 413                         if ( !$res->numRows() ) {
 414                                 break;
 415                         }
 416                         $ids = [];
 417                         foreach ( $res as $row ) {
 418                                 $startId = $row->bt_text_id;
 419                                 $ids[] = $row->bt_text_id;
 420                                 $i++;
 421                         }
 422                         // Need to send enough orphan IDs to the child at a time to fill a blob,
 423                         // so orphanBatchSize needs to be at least ~100.
 424                         // batchSize can be smaller or larger.
 425                         while ( count( $ids ) > $this->orphanBatchSize ) {
 426                                 $args = array_slice( $ids, 0, $this->orphanBatchSize );
 427                                 $ids = array_slice( $ids, $this->orphanBatchSize );
 428                                 array_unshift( $args, 'doOrphanList' );
 429                                 call_user_func_array( [ $this, 'dispatch' ], $args );
 430                         }
 431                         if ( count( $ids ) ) {
 432                                 $args = $ids;
 433                                 array_unshift( $args, 'doOrphanList' );
 434                                 call_user_func_array( [ $this, 'dispatch' ], $args );
 435                         }
 436
 437                         $this->report( 'orphans', $i, $numOrphans );
 438                 }
 439                 $this->report( 'orphans', $i, $numOrphans );
 440                 $this->info( "All orphans queued." );
 441         }
 442
 443         /**
 444          * Main entry point for worker processes
 445          */
 446         function executeChild() {
 447                 $this->debug( 'starting' );
 448                 $this->syncDBs();
 449
 450                 while ( !feof( STDIN ) ) {
 451                         $line = rtrim( fgets( STDIN ) );
 452                         if ( $line == '' ) {
 453                                 continue;
 454                         }
 455                         $this->debug( $line );
 456                         $args = explode( ' ', $line );
 457                         $cmd = array_shift( $args );
 458                         switch ( $cmd ) {
 459                                 case 'doPage':
 460                                         $this->doPage( intval( $args[0] ) );
 461                                         break;
 462                                 case 'doOrphanList':
 463                                         $this->doOrphanList( array_map( 'intval', $args ) );
 464                                         break;
 465                                 case 'quit':
 466                                         return;
 467                         }
 468                         MediaWikiServices::getInstance()->getDBLoadBalancerFactory()->waitForReplication();
 469                 }
 470         }
 471
 472         /**
 473          * Move tracked text in a given page
 474          *
 475          * @param int $pageId
 476          */
 477         function doPage( $pageId ) {
 478                 $title = Title::newFromID( $pageId );
 479                 if ( $title ) {
 480                         $titleText = $title->getPrefixedText();
 481                 } else {
 482                         $titleText = '[deleted]';
 483                 }
 484                 $dbr = wfGetDB( DB_REPLICA );
 485
 486                 // Finish any incomplete transactions
 487                 if ( !$this->copyOnly ) {
 488                         $this->finishIncompleteMoves( [ 'bt_page' => $pageId ] );
 489                         $this->syncDBs();
 490                 }
 491
 492                 $startId = 0;
 493                 $trx = new CgzCopyTransaction( $this, $this->pageBlobClass );
 494
 495                 $lbFactory = MediaWikiServices::getInstance()->getDBLoadBalancerFactory();
 496                 while ( true ) {
 497                         $res = $dbr->select(
 498                                 [ 'blob_tracking', 'text' ],
 499                                 '*',
 500                                 [
 501                                         'bt_page' => $pageId,
 502                                         'bt_text_id > ' . $dbr->addQuotes( $startId ),
 503                                         'bt_moved' => 0,
 504                                         'bt_new_url IS NULL',
 505                                         'bt_text_id=old_id',
 506                                 ],
 507                                 __METHOD__,
 508                                 [
 509                                         'ORDER BY' => 'bt_text_id',
 510                                         'LIMIT' => $this->batchSize
 511                                 ]
 512                         );
 513                         if ( !$res->numRows() ) {
 514                                 break;
 515                         }
 516
 517                         $lastTextId = 0;
 518                         foreach ( $res as $row ) {
 519                                 $startId = $row->bt_text_id;
 520                                 if ( $lastTextId == $row->bt_text_id ) {
 521                                         // Duplicate (null edit)
 522                                         continue;
 523                                 }
 524                                 $lastTextId = $row->bt_text_id;
 525                                 // Load the text
 526                                 $text = Revision::getRevisionText( $row );
 527                                 if ( $text === false ) {
 528                                         $this->critical( "Error loading {$row->bt_rev_id}/{$row->bt_text_id}" );
 529                                         continue;
 530                                 }
 531
 532                                 // Queue it
 533                                 if ( !$trx->addItem( $text, $row->bt_text_id ) ) {
 534                                         $this->debug( "$titleText: committing blob with " . $trx->getSize() . " items" );
 535                                         $trx->commit();
 536                                         $trx = new CgzCopyTransaction( $this, $this->pageBlobClass );
 537                                         $lbFactory->waitForReplication();
 538                                 }
 539                         }
 540                 }
 541
 542                 $this->debug( "$titleText: committing blob with " . $trx->getSize() . " items" );
 543                 $trx->commit();
 544         }
 545
 546         /**
 547          * Atomic move operation.
 548          *
 549          * Write the new URL to the text table and set the bt_moved flag.
 550          *
 551          * This is done in a single transaction to provide restartable behavior
 552          * without data loss.
 553          *
 554          * The transaction is kept short to reduce locking.
 555          *
 556          * @param int $textId
 557          * @param string $url
 558          */
 559         function moveTextRow( $textId, $url ) {
 560                 if ( $this->copyOnly ) {
 561                         $this->critical( "Internal error: can't call moveTextRow() in --copy-only mode" );
 562                         exit( 1 );
 563                 }
 564                 $dbw = wfGetDB( DB_MASTER );
 565                 $dbw->begin( __METHOD__ );
 566                 $dbw->update( 'text',
 567                         [ // set
 568                                 'old_text' => $url,
 569                                 'old_flags' => 'external,utf-8',
 570                         ],
 571                         [ // where
 572                                 'old_id' => $textId
 573                         ],
 574                         __METHOD__
 575                 );
 576                 $dbw->update( 'blob_tracking',
 577                         [ 'bt_moved' => 1 ],
 578                         [ 'bt_text_id' => $textId ],
 579                         __METHOD__
 580                 );
 581                 $dbw->commit( __METHOD__ );
 582         }
 583
 584         /**
 585          * Moves are done in two phases: bt_new_url and then bt_moved.
 586          *  - bt_new_url indicates that the text has been copied to the new cluster.
 587          *  - bt_moved indicates that the text table has been updated.
 588          *
 589          * This function completes any moves that only have done bt_new_url. This
 590          * can happen when the script is interrupted, or when --copy-only is used.
 591          *
 592          * @param array $conds
 593          */
 594         function finishIncompleteMoves( $conds ) {
 595                 $dbr = wfGetDB( DB_REPLICA );
 596                 $lbFactory = MediaWikiServices::getInstance()->getDBLoadBalancerFactory();
 597
 598                 $startId = 0;
 599                 $conds = array_merge( $conds, [
 600                         'bt_moved' => 0,
 601                         'bt_new_url IS NOT NULL'
 602                 ] );
 603                 while ( true ) {
 604                         $res = $dbr->select( 'blob_tracking',
 605                                 '*',
 606                                 array_merge( $conds, [ 'bt_text_id > ' . $dbr->addQuotes( $startId ) ] ),
 607                                 __METHOD__,
 608                                 [
 609                                         'ORDER BY' => 'bt_text_id',
 610                                         'LIMIT' => $this->batchSize,
 611                                 ]
 612                         );
 613                         if ( !$res->numRows() ) {
 614                                 break;
 615                         }
 616                         $this->debug( 'Incomplete: ' . $res->numRows() . ' rows' );
 617                         foreach ( $res as $row ) {
 618                                 $startId = $row->bt_text_id;
 619                                 $this->moveTextRow( $row->bt_text_id, $row->bt_new_url );
 620                                 if ( $row->bt_text_id % 10 == 0 ) {
 621                                         $lbFactory->waitForReplication();
 622                                 }
 623                         }
 624                 }
 625         }
 626
 627         /**
 628          * Returns the name of the next target cluster
 629          * @return string
 630          */
 631         function getTargetCluster() {
 632                 $cluster = next( $this->destClusters );
 633                 if ( $cluster === false ) {
 634                         $cluster = reset( $this->destClusters );
 635                 }
 636
 637                 return $cluster;
 638         }
 639
 640         /**
 641          * Gets a DB master connection for the given external cluster name
 642          * @param string $cluster
 643          * @return Database
 644          */
 645         function getExtDB( $cluster ) {
 646                 $lb = wfGetLBFactory()->getExternalLB( $cluster );
 647
 648                 return $lb->getConnection( DB_MASTER );
 649         }
 650
 651         /**
 652          * Move an orphan text_id to the new cluster
 653          *
 654          * @param array $textIds
 655          */
 656         function doOrphanList( $textIds ) {
 657                 // Finish incomplete moves
 658                 if ( !$this->copyOnly ) {
 659                         $this->finishIncompleteMoves( [ 'bt_text_id' => $textIds ] );
 660                         $this->syncDBs();
 661                 }
 662
 663                 $trx = new CgzCopyTransaction( $this, $this->orphanBlobClass );
 664
 665                 $lbFactory = MediaWikiServices::getInstance()->getDBLoadBalancerFactory();
 666                 $res = wfGetDB( DB_REPLICA )->select(
 667                         [ 'text', 'blob_tracking' ],
 668                         [ 'old_id', 'old_text', 'old_flags' ],
 669                         [
 670                                 'old_id' => $textIds,
 671                                 'bt_text_id=old_id',
 672                                 'bt_moved' => 0,
 673                         ],
 674                         __METHOD__,
 675                         [ 'DISTINCT' ]
 676                 );
 677
 678                 foreach ( $res as $row ) {
 679                         $text = Revision::getRevisionText( $row );
 680                         if ( $text === false ) {
 681                                 $this->critical( "Error: cannot load revision text for old_id={$row->old_id}" );
 682                                 continue;
 683                         }
 684
 685                         if ( !$trx->addItem( $text, $row->old_id ) ) {
 686                                 $this->debug( "[orphan]: committing blob with " . $trx->getSize() . " rows" );
 687                                 $trx->commit();
 688                                 $trx = new CgzCopyTransaction( $this, $this->orphanBlobClass );
 689                                 $lbFactory->waitForReplication();
 690                         }
 691                 }
 692                 $this->debug( "[orphan]: committing blob with " . $trx->getSize() . " rows" );
 693                 $trx->commit();
 694         }
 695 }
 696
 697 /**
 698  * Class to represent a recompression operation for a single CGZ blob
 699  */
 700 class CgzCopyTransaction {
 701         /** @var RecompressTracked */
 702         public $parent;
 703         public $blobClass;
 704         /** @var ConcatenatedGzipHistoryBlob */
 705         public $cgz;
 706         public $referrers;
 707
 708         /**
 709          * Create a transaction from a RecompressTracked object
 710          * @param RecompressTracked $parent
 711          * @param string $blobClass
 712          */
 713         function __construct( $parent, $blobClass ) {
 714                 $this->blobClass = $blobClass;
 715                 $this->cgz = false;
 716                 $this->texts = [];
 717                 $this->parent = $parent;
 718         }
 719
 720         /**
 721          * Add text.
 722          * Returns false if it's ready to commit.
 723          * @param string $text
 724          * @param int $textId
 725          * @return bool
 726          */
 727         function addItem( $text, $textId ) {
 728                 if ( !$this->cgz ) {
 729                         $class = $this->blobClass;
 730                         $this->cgz = new $class;
 731                 }
 732                 $hash = $this->cgz->addItem( $text );
 733                 $this->referrers[$textId] = $hash;
 734                 $this->texts[$textId] = $text;
 735
 736                 return $this->cgz->isHappy();
 737         }
 738
 739         function getSize() {
 740                 return count( $this->texts );
 741         }
 742
 743         /**
 744          * Recompress text after some aberrant modification
 745          */
 746         function recompress() {
 747                 $class = $this->blobClass;
 748                 $this->cgz = new $class;
 749                 $this->referrers = [];
 750                 foreach ( $this->texts as $textId => $text ) {
 751                         $hash = $this->cgz->addItem( $text );
 752                         $this->referrers[$textId] = $hash;
 753                 }
 754         }
 755
 756         /**
 757          * Commit the blob.
 758          * Does nothing if no text items have been added.
 759          * May skip the move if --copy-only is set.
 760          */
 761         function commit() {
 762                 $originalCount = count( $this->texts );
 763                 if ( !$originalCount ) {
 764                         return;
 765                 }
 766
 767                 /* Check to see if the target text_ids have been moved already.
 768                  *
 769                  * We originally read from the replica DB, so this can happen when a single
 770                  * text_id is shared between multiple pages. It's rare, but possible
 771                  * if a delete/move/undelete cycle splits up a null edit.
 772                  *
 773                  * We do a locking read to prevent closer-run race conditions.
 774                  */
 775                 $dbw = wfGetDB( DB_MASTER );
 776                 $dbw->begin( __METHOD__ );
 777                 $res = $dbw->select( 'blob_tracking',
 778                         [ 'bt_text_id', 'bt_moved' ],
 779                         [ 'bt_text_id' => array_keys( $this->referrers ) ],
 780                         __METHOD__, [ 'FOR UPDATE' ] );
 781                 $dirty = false;
 782                 foreach ( $res as $row ) {
 783                         if ( $row->bt_moved ) {
 784                                 # This row has already been moved, remove it
 785                                 $this->parent->debug( "TRX: conflict detected in old_id={$row->bt_text_id}" );
 786                                 unset( $this->texts[$row->bt_text_id] );
 787                                 $dirty = true;
 788                         }
 789                 }
 790
 791                 // Recompress the blob if necessary
 792                 if ( $dirty ) {
 793                         if ( !count( $this->texts ) ) {
 794                                 // All have been moved already
 795                                 if ( $originalCount > 1 ) {
 796                                         // This is suspcious, make noise
 797                                         $this->parent->critical(
 798                                                 "Warning: concurrent operation detected, are there two conflicting " .
 799                                                 "processes running, doing the same job?" );
 800                                 }
 801
 802                                 return;
 803                         }
 804                         $this->recompress();
 805                 }
 806
 807                 // Insert the data into the destination cluster
 808                 $targetCluster = $this->parent->getTargetCluster();
 809                 $store = $this->parent->store;
 810                 $targetDB = $store->getMaster( $targetCluster );
 811                 $targetDB->clearFlag( DBO_TRX ); // we manage the transactions
 812                 $targetDB->begin( __METHOD__ );
 813                 $baseUrl = $this->parent->store->store( $targetCluster, serialize( $this->cgz ) );
 814
 815                 // Write the new URLs to the blob_tracking table
 816                 foreach ( $this->referrers as $textId => $hash ) {
 817                         $url = $baseUrl . '/' . $hash;
 818                         $dbw->update( 'blob_tracking',
 819                                 [ 'bt_new_url' => $url ],
 820                                 [
 821                                         'bt_text_id' => $textId,
 822                                         'bt_moved' => 0, # Check for concurrent conflicting update
 823                                 ],
 824                                 __METHOD__
 825                         );
 826                 }
 827
 828                 $targetDB->commit( __METHOD__ );
 829                 // Critical section here: interruption at this point causes blob duplication
 830                 // Reversing the order of the commits would cause data loss instead
 831                 $dbw->commit( __METHOD__ );
 832
 833                 // Write the new URLs to the text table and set the moved flag
 834                 if ( !$this->parent->copyOnly ) {
 835                         foreach ( $this->referrers as $textId => $hash ) {
 836                                 $url = $baseUrl . '/' . $hash;
 837                                 $this->parent->moveTextRow( $textId, $url );
 838                         }
 839                 }
 840         }
 841 }