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 use MediaWiki\Shell\Shell;
  28 use Wikimedia\Rdbms\IDatabase;
  29
  30 $optionsWithArgs = RecompressTracked::getOptionsWithArgs();
  31 require __DIR__ . '/../commandLine.inc';
  32
  33 if ( count( $args ) < 1 ) {
  34         echo "Usage: php recompressTracked.php [options] <cluster> [... <cluster>...]
  35 Moves blobs indexed by trackBlobs.php to a specified list of destination clusters,
  36 and recompresses them in the process. Restartable.
  37
  38 Options:
  39         --procs <procs>       Set the number of child processes (default 1)
  40         --copy-only           Copy only, do not update the text table. Restart
  41                               without this option to complete.
  42         --debug-log <file>    Log debugging data to the specified file
  43         --info-log <file>     Log progress messages to the specified file
  44         --critical-log <file> Log error messages to the specified file
  45 ";
  46         exit( 1 );
  47 }
  48
  49 $job = RecompressTracked::newFromCommandLine( $args, $options );
  50 $job->execute();
  51
  52 /**
  53  * Maintenance script that moves blobs indexed by trackBlobs.php to a specified
  54  * list of destination clusters, and recompresses them in the process.
  55  *
  56  * @ingroup Maintenance ExternalStorage
  57  */
  58 class RecompressTracked {
  59         public $destClusters;
  60         public $batchSize = 1000;
  61         public $orphanBatchSize = 1000;
  62         public $reportingInterval = 10;
  63         public $numProcs = 1;
  64         public $numBatches = 0;
  65         public $pageBlobClass, $orphanBlobClass;
  66         public $replicaPipes, $replicaProcs, $prevReplicaId;
  67         public $copyOnly = false;
  68         public $isChild = false;
  69         public $replicaId = false;
  70         public $noCount = false;
  71         public $debugLog, $infoLog, $criticalLog;
  72         /** @var ExternalStoreDB */
  73         public $store;
  74
  75         private static $optionsWithArgs = [
  76                 'procs',
  77                 'replica-id',
  78                 'debug-log',
  79                 'info-log',
  80                 'critical-log'
  81         ];
  82
  83         private static $cmdLineOptionMap = [
  84                 'no-count' => 'noCount',
  85                 'procs' => 'numProcs',
  86                 'copy-only' => 'copyOnly',
  87                 'child' => 'isChild',
  88                 'replica-id' => 'replicaId',
  89                 'debug-log' => 'debugLog',
  90                 'info-log' => 'infoLog',
  91                 'critical-log' => 'criticalLog',
  92         ];
  93
  94         static function getOptionsWithArgs() {
  95                 return self::$optionsWithArgs;
  96         }
  97
  98         static function newFromCommandLine( $args, $options ) {
  99                 $jobOptions = [ 'destClusters' => $args ];
 100                 foreach ( self::$cmdLineOptionMap as $cmdOption => $classOption ) {
 101                         if ( isset( $options[$cmdOption] ) ) {
 102                                 $jobOptions[$classOption] = $options[$cmdOption];
 103                         }
 104                 }
 105
 106                 return new self( $jobOptions );
 107         }
 108
 109         function __construct( $options ) {
 110                 foreach ( $options as $name => $value ) {
 111                         $this->$name = $value;
 112                 }
 113                 $esFactory = MediaWikiServices::getInstance()->getExternalStoreFactory();
 114                 $this->store = $esFactory->getStore( 'DB' );
 115                 if ( !$this->isChild ) {
 116                         $GLOBALS['wgDebugLogPrefix'] = "RCT M: ";
 117                 } elseif ( $this->replicaId !== false ) {
 118                         $GLOBALS['wgDebugLogPrefix'] = "RCT {$this->replicaId}: ";
 119                 }
 120                 $this->pageBlobClass = function_exists( 'xdiff_string_bdiff' ) ?
 121                         DiffHistoryBlob::class : ConcatenatedGzipHistoryBlob::class;
 122                 $this->orphanBlobClass = ConcatenatedGzipHistoryBlob::class;
 123         }
 124
 125         function debug( $msg ) {
 126                 wfDebug( "$msg\n" );
 127                 if ( $this->debugLog ) {
 128                         $this->logToFile( $msg, $this->debugLog );
 129                 }
 130         }
 131
 132         function info( $msg ) {
 133                 echo "$msg\n";
 134                 if ( $this->infoLog ) {
 135                         $this->logToFile( $msg, $this->infoLog );
 136                 }
 137         }
 138
 139         function critical( $msg ) {
 140                 echo "$msg\n";
 141                 if ( $this->criticalLog ) {
 142                         $this->logToFile( $msg, $this->criticalLog );
 143                 }
 144         }
 145
 146         function logToFile( $msg, $file ) {
 147                 $header = '[' . date( 'd\TH:i:s' ) . '] ' . wfHostname() . ' ' . posix_getpid();
 148                 if ( $this->replicaId !== false ) {
 149                         $header .= "({$this->replicaId})";
 150                 }
 151                 $header .= ' ' . WikiMap::getCurrentWikiDbDomain()->getId();
 152                 LegacyLogger::emit( sprintf( "%-50s %s\n", $header, $msg ), $file );
 153         }
 154
 155         /**
 156          * Wait until the selected replica DB has caught up to the master.
 157          * This allows us to use the replica DB for things that were committed in a
 158          * previous part of this batch process.
 159          */
 160         function syncDBs() {
 161                 $dbw = wfGetDB( DB_MASTER );
 162                 $dbr = wfGetDB( DB_REPLICA );
 163                 $pos = $dbw->getMasterPos();
 164                 $dbr->masterPosWait( $pos, 100000 );
 165         }
 166
 167         /**
 168          * Execute parent or child depending on the isChild option
 169          */
 170         function execute() {
 171                 if ( $this->isChild ) {
 172                         $this->executeChild();
 173                 } else {
 174                         $this->executeParent();
 175                 }
 176         }
 177
 178         /**
 179          * Execute the parent process
 180          */
 181         function executeParent() {
 182                 if ( !$this->checkTrackingTable() ) {
 183                         return;
 184                 }
 185
 186                 $this->syncDBs();
 187                 $this->startReplicaProcs();
 188                 $this->doAllPages();
 189                 $this->doAllOrphans();
 190                 $this->killReplicaProcs();
 191         }
 192
 193         /**
 194          * Make sure the tracking table exists and isn't empty
 195          * @return bool
 196          */
 197         function checkTrackingTable() {
 198                 $dbr = wfGetDB( DB_REPLICA );
 199                 if ( !$dbr->tableExists( 'blob_tracking' ) ) {
 200                         $this->critical( "Error: blob_tracking table does not exist" );
 201
 202                         return false;
 203                 }
 204                 $row = $dbr->selectRow( 'blob_tracking', '*', '', __METHOD__ );
 205                 if ( !$row ) {
 206                         $this->info( "Warning: blob_tracking table contains no rows, skipping this wiki." );
 207
 208                         return false;
 209                 }
 210
 211                 return true;
 212         }
 213
 214         /**
 215          * Start the worker processes.
 216          * These processes will listen on stdin for commands.
 217          * This necessary because text recompression is slow: loading, compressing and
 218          * writing are all slow.
 219          */
 220         function startReplicaProcs() {
 221                 $wiki = WikiMap::getWikiIdFromDbDomain( WikiMap::getCurrentWikiDbDomain() );
 222
 223                 $cmd = 'php ' . Shell::escape( __FILE__ );
 224                 foreach ( self::$cmdLineOptionMap as $cmdOption => $classOption ) {
 225                         if ( $cmdOption == 'replica-id' ) {
 226                                 continue;
 227                         } elseif ( in_array( $cmdOption, self::$optionsWithArgs ) && isset( $this->$classOption ) ) {
 228                                 $cmd .= " --$cmdOption " . Shell::escape( $this->$classOption );
 229                         } elseif ( $this->$classOption ) {
 230                                 $cmd .= " --$cmdOption";
 231                         }
 232                 }
 233                 $cmd .= ' --child' .
 234                         ' --wiki ' . Shell::escape( $wiki ) .
 235                         ' ' . Shell::escape( ...$this->destClusters );
 236
 237                 $this->replicaPipes = $this->replicaProcs = [];
 238                 for ( $i = 0; $i < $this->numProcs; $i++ ) {
 239                         $pipes = [];
 240                         $spec = [
 241                                 [ 'pipe', 'r' ],
 242                                 [ 'file', 'php://stdout', 'w' ],
 243                                 [ 'file', 'php://stderr', 'w' ]
 244                         ];
 245                         Wikimedia\suppressWarnings();
 246                         $proc = proc_open( "$cmd --replica-id $i", $spec, $pipes );
 247                         Wikimedia\restoreWarnings();
 248                         if ( !$proc ) {
 249                                 $this->critical( "Error opening replica DB process: $cmd" );
 250                                 exit( 1 );
 251                         }
 252                         $this->replicaProcs[$i] = $proc;
 253                         $this->replicaPipes[$i] = $pipes[0];
 254                 }
 255                 $this->prevReplicaId = -1;
 256         }
 257
 258         /**
 259          * Gracefully terminate the child processes
 260          */
 261         function killReplicaProcs() {
 262                 $this->info( "Waiting for replica DB processes to finish..." );
 263                 for ( $i = 0; $i < $this->numProcs; $i++ ) {
 264                         $this->dispatchToReplica( $i, 'quit' );
 265                 }
 266                 for ( $i = 0; $i < $this->numProcs; $i++ ) {
 267                         $status = proc_close( $this->replicaProcs[$i] );
 268                         if ( $status ) {
 269                                 $this->critical( "Warning: child #$i exited with status $status" );
 270                         }
 271                 }
 272                 $this->info( "Done." );
 273         }
 274
 275         /**
 276          * Dispatch a command to the next available replica DB.
 277          * This may block until a replica DB finishes its work and becomes available.
 278          */
 279         function dispatch( ...$args ) {
 280                 $pipes = $this->replicaPipes;
 281                 $x = [];
 282                 $y = [];
 283                 $numPipes = stream_select( $x, $pipes, $y, 3600 );
 284                 if ( !$numPipes ) {
 285                         $this->critical( "Error waiting to write to replica DBs. Aborting" );
 286                         exit( 1 );
 287                 }
 288                 for ( $i = 0; $i < $this->numProcs; $i++ ) {
 289                         $replicaId = ( $i + $this->prevReplicaId + 1 ) % $this->numProcs;
 290                         if ( isset( $pipes[$replicaId] ) ) {
 291                                 $this->prevReplicaId = $replicaId;
 292                                 $this->dispatchToReplica( $replicaId, $args );
 293
 294                                 return;
 295                         }
 296                 }
 297                 $this->critical( "Unreachable" );
 298                 exit( 1 );
 299         }
 300
 301         /**
 302          * Dispatch a command to a specified replica DB
 303          * @param int $replicaId
 304          * @param array|string $args
 305          */
 306         function dispatchToReplica( $replicaId, $args ) {
 307                 $args = (array)$args;
 308                 $cmd = implode( ' ', $args );
 309                 fwrite( $this->replicaPipes[$replicaId], "$cmd\n" );
 310         }
 311
 312         /**
 313          * Move all tracked pages to the new clusters
 314          */
 315         function doAllPages() {
 316                 $dbr = wfGetDB( DB_REPLICA );
 317                 $i = 0;
 318                 $startId = 0;
 319                 if ( $this->noCount ) {
 320                         $numPages = '[unknown]';
 321                 } else {
 322                         $numPages = $dbr->selectField( 'blob_tracking',
 323                                 'COUNT(DISTINCT bt_page)',
 324                                 # A condition is required so that this query uses the index
 325                                 [ 'bt_moved' => 0 ],
 326                                 __METHOD__
 327                         );
 328                 }
 329                 if ( $this->copyOnly ) {
 330                         $this->info( "Copying pages..." );
 331                 } else {
 332                         $this->info( "Moving pages..." );
 333                 }
 334                 while ( true ) {
 335                         $res = $dbr->select( 'blob_tracking',
 336                                 [ 'bt_page' ],
 337                                 [
 338                                         'bt_moved' => 0,
 339                                         'bt_page > ' . $dbr->addQuotes( $startId )
 340                                 ],
 341                                 __METHOD__,
 342                                 [
 343                                         'DISTINCT',
 344                                         'ORDER BY' => 'bt_page',
 345                                         'LIMIT' => $this->batchSize,
 346                                 ]
 347                         );
 348                         if ( !$res->numRows() ) {
 349                                 break;
 350                         }
 351                         foreach ( $res as $row ) {
 352                                 $startId = $row->bt_page;
 353                                 $this->dispatch( 'doPage', $row->bt_page );
 354                                 $i++;
 355                         }
 356                         $this->report( 'pages', $i, $numPages );
 357                 }
 358                 $this->report( 'pages', $i, $numPages );
 359                 if ( $this->copyOnly ) {
 360                         $this->info( "All page copies queued." );
 361                 } else {
 362                         $this->info( "All page moves queued." );
 363                 }
 364         }
 365
 366         /**
 367          * Display a progress report
 368          * @param string $label
 369          * @param int $current
 370          * @param int $end
 371          */
 372         function report( $label, $current, $end ) {
 373                 $this->numBatches++;
 374                 if ( $current == $end || $this->numBatches >= $this->reportingInterval ) {
 375                         $this->numBatches = 0;
 376                         $this->info( "$label: $current / $end" );
 377                         MediaWikiServices::getInstance()->getDBLoadBalancerFactory()->waitForReplication();
 378                 }
 379         }
 380
 381         /**
 382          * Move all orphan text to the new clusters
 383          */
 384         function doAllOrphans() {
 385                 $dbr = wfGetDB( DB_REPLICA );
 386                 $startId = 0;
 387                 $i = 0;
 388                 if ( $this->noCount ) {
 389                         $numOrphans = '[unknown]';
 390                 } else {
 391                         $numOrphans = $dbr->selectField( 'blob_tracking',
 392                                 'COUNT(DISTINCT bt_text_id)',
 393                                 [ 'bt_moved' => 0, 'bt_page' => 0 ],
 394                                 __METHOD__ );
 395                         if ( !$numOrphans ) {
 396                                 return;
 397                         }
 398                 }
 399                 if ( $this->copyOnly ) {
 400                         $this->info( "Copying orphans..." );
 401                 } else {
 402                         $this->info( "Moving orphans..." );
 403                 }
 404
 405                 while ( true ) {
 406                         $res = $dbr->select( 'blob_tracking',
 407                                 [ 'bt_text_id' ],
 408                                 [
 409                                         'bt_moved' => 0,
 410                                         'bt_page' => 0,
 411                                         'bt_text_id > ' . $dbr->addQuotes( $startId )
 412                                 ],
 413                                 __METHOD__,
 414                                 [
 415                                         'DISTINCT',
 416                                         'ORDER BY' => 'bt_text_id',
 417                                         'LIMIT' => $this->batchSize
 418                                 ]
 419                         );
 420                         if ( !$res->numRows() ) {
 421                                 break;
 422                         }
 423                         $ids = [];
 424                         foreach ( $res as $row ) {
 425                                 $startId = $row->bt_text_id;
 426                                 $ids[] = $row->bt_text_id;
 427                                 $i++;
 428                         }
 429                         // Need to send enough orphan IDs to the child at a time to fill a blob,
 430                         // so orphanBatchSize needs to be at least ~100.
 431                         // batchSize can be smaller or larger.
 432                         while ( count( $ids ) > $this->orphanBatchSize ) {
 433                                 $args = array_slice( $ids, 0, $this->orphanBatchSize );
 434                                 $ids = array_slice( $ids, $this->orphanBatchSize );
 435                                 array_unshift( $args, 'doOrphanList' );
 436                                 $this->dispatch( ...$args );
 437                         }
 438                         if ( count( $ids ) ) {
 439                                 $args = $ids;
 440                                 array_unshift( $args, 'doOrphanList' );
 441                                 $this->dispatch( ...$args );
 442                         }
 443
 444                         $this->report( 'orphans', $i, $numOrphans );
 445                 }
 446                 $this->report( 'orphans', $i, $numOrphans );
 447                 $this->info( "All orphans queued." );
 448         }
 449
 450         /**
 451          * Main entry point for worker processes
 452          */
 453         function executeChild() {
 454                 $this->debug( 'starting' );
 455                 $this->syncDBs();
 456
 457                 while ( !feof( STDIN ) ) {
 458                         $line = rtrim( fgets( STDIN ) );
 459                         if ( $line == '' ) {
 460                                 continue;
 461                         }
 462                         $this->debug( $line );
 463                         $args = explode( ' ', $line );
 464                         $cmd = array_shift( $args );
 465                         switch ( $cmd ) {
 466                                 case 'doPage':
 467                                         $this->doPage( intval( $args[0] ) );
 468                                         break;
 469                                 case 'doOrphanList':
 470                                         $this->doOrphanList( array_map( 'intval', $args ) );
 471                                         break;
 472                                 case 'quit':
 473                                         return;
 474                         }
 475                         MediaWikiServices::getInstance()->getDBLoadBalancerFactory()->waitForReplication();
 476                 }
 477         }
 478
 479         /**
 480          * Move tracked text in a given page
 481          *
 482          * @param int $pageId
 483          */
 484         function doPage( $pageId ) {
 485                 $title = Title::newFromID( $pageId );
 486                 if ( $title ) {
 487                         $titleText = $title->getPrefixedText();
 488                 } else {
 489                         $titleText = '[deleted]';
 490                 }
 491                 $dbr = wfGetDB( DB_REPLICA );
 492
 493                 // Finish any incomplete transactions
 494                 if ( !$this->copyOnly ) {
 495                         $this->finishIncompleteMoves( [ 'bt_page' => $pageId ] );
 496                         $this->syncDBs();
 497                 }
 498
 499                 $startId = 0;
 500                 $trx = new CgzCopyTransaction( $this, $this->pageBlobClass );
 501
 502                 $lbFactory = MediaWikiServices::getInstance()->getDBLoadBalancerFactory();
 503                 while ( true ) {
 504                         $res = $dbr->select(
 505                                 [ 'blob_tracking', 'text' ],
 506                                 '*',
 507                                 [
 508                                         'bt_page' => $pageId,
 509                                         'bt_text_id > ' . $dbr->addQuotes( $startId ),
 510                                         'bt_moved' => 0,
 511                                         'bt_new_url IS NULL',
 512                                         'bt_text_id=old_id',
 513                                 ],
 514                                 __METHOD__,
 515                                 [
 516                                         'ORDER BY' => 'bt_text_id',
 517                                         'LIMIT' => $this->batchSize
 518                                 ]
 519                         );
 520                         if ( !$res->numRows() ) {
 521                                 break;
 522                         }
 523
 524                         $lastTextId = 0;
 525                         foreach ( $res as $row ) {
 526                                 $startId = $row->bt_text_id;
 527                                 if ( $lastTextId == $row->bt_text_id ) {
 528                                         // Duplicate (null edit)
 529                                         continue;
 530                                 }
 531                                 $lastTextId = $row->bt_text_id;
 532                                 // Load the text
 533                                 $text = Revision::getRevisionText( $row );
 534                                 if ( $text === false ) {
 535                                         $this->critical( "Error loading {$row->bt_rev_id}/{$row->bt_text_id}" );
 536                                         continue;
 537                                 }
 538
 539                                 // Queue it
 540                                 if ( !$trx->addItem( $text, $row->bt_text_id ) ) {
 541                                         $this->debug( "$titleText: committing blob with " . $trx->getSize() . " items" );
 542                                         $trx->commit();
 543                                         $trx = new CgzCopyTransaction( $this, $this->pageBlobClass );
 544                                         $lbFactory->waitForReplication();
 545                                 }
 546                         }
 547                 }
 548
 549                 $this->debug( "$titleText: committing blob with " . $trx->getSize() . " items" );
 550                 $trx->commit();
 551         }
 552
 553         /**
 554          * Atomic move operation.
 555          *
 556          * Write the new URL to the text table and set the bt_moved flag.
 557          *
 558          * This is done in a single transaction to provide restartable behavior
 559          * without data loss.
 560          *
 561          * The transaction is kept short to reduce locking.
 562          *
 563          * @param int $textId
 564          * @param string $url
 565          */
 566         function moveTextRow( $textId, $url ) {
 567                 if ( $this->copyOnly ) {
 568                         $this->critical( "Internal error: can't call moveTextRow() in --copy-only mode" );
 569                         exit( 1 );
 570                 }
 571                 $dbw = wfGetDB( DB_MASTER );
 572                 $dbw->begin( __METHOD__ );
 573                 $dbw->update( 'text',
 574                         [ // set
 575                                 'old_text' => $url,
 576                                 'old_flags' => 'external,utf-8',
 577                         ],
 578                         [ // where
 579                                 'old_id' => $textId
 580                         ],
 581                         __METHOD__
 582                 );
 583                 $dbw->update( 'blob_tracking',
 584                         [ 'bt_moved' => 1 ],
 585                         [ 'bt_text_id' => $textId ],
 586                         __METHOD__
 587                 );
 588                 $dbw->commit( __METHOD__ );
 589         }
 590
 591         /**
 592          * Moves are done in two phases: bt_new_url and then bt_moved.
 593          *  - bt_new_url indicates that the text has been copied to the new cluster.
 594          *  - bt_moved indicates that the text table has been updated.
 595          *
 596          * This function completes any moves that only have done bt_new_url. This
 597          * can happen when the script is interrupted, or when --copy-only is used.
 598          *
 599          * @param array $conds
 600          */
 601         function finishIncompleteMoves( $conds ) {
 602                 $dbr = wfGetDB( DB_REPLICA );
 603                 $lbFactory = MediaWikiServices::getInstance()->getDBLoadBalancerFactory();
 604
 605                 $startId = 0;
 606                 $conds = array_merge( $conds, [
 607                         'bt_moved' => 0,
 608                         'bt_new_url IS NOT NULL'
 609                 ] );
 610                 while ( true ) {
 611                         $res = $dbr->select( 'blob_tracking',
 612                                 '*',
 613                                 array_merge( $conds, [ 'bt_text_id > ' . $dbr->addQuotes( $startId ) ] ),
 614                                 __METHOD__,
 615                                 [
 616                                         'ORDER BY' => 'bt_text_id',
 617                                         'LIMIT' => $this->batchSize,
 618                                 ]
 619                         );
 620                         if ( !$res->numRows() ) {
 621                                 break;
 622                         }
 623                         $this->debug( 'Incomplete: ' . $res->numRows() . ' rows' );
 624                         foreach ( $res as $row ) {
 625                                 $startId = $row->bt_text_id;
 626                                 $this->moveTextRow( $row->bt_text_id, $row->bt_new_url );
 627                                 if ( $row->bt_text_id % 10 == 0 ) {
 628                                         $lbFactory->waitForReplication();
 629                                 }
 630                         }
 631                 }
 632         }
 633
 634         /**
 635          * Returns the name of the next target cluster
 636          * @return string
 637          */
 638         function getTargetCluster() {
 639                 $cluster = next( $this->destClusters );
 640                 if ( $cluster === false ) {
 641                         $cluster = reset( $this->destClusters );
 642                 }
 643
 644                 return $cluster;
 645         }
 646
 647         /**
 648          * Gets a DB master connection for the given external cluster name
 649          * @param string $cluster
 650          * @return IDatabase
 651          */
 652         function getExtDB( $cluster ) {
 653                 $lbFactory = MediaWikiServices::getInstance()->getDBLoadBalancerFactory();
 654                 $lb = $lbFactory->getExternalLB( $cluster );
 655
 656                 return $lb->getConnection( DB_MASTER );
 657         }
 658
 659         /**
 660          * Move an orphan text_id to the new cluster
 661          *
 662          * @param array $textIds
 663          */
 664         function doOrphanList( $textIds ) {
 665                 // Finish incomplete moves
 666                 if ( !$this->copyOnly ) {
 667                         $this->finishIncompleteMoves( [ 'bt_text_id' => $textIds ] );
 668                         $this->syncDBs();
 669                 }
 670
 671                 $trx = new CgzCopyTransaction( $this, $this->orphanBlobClass );
 672
 673                 $lbFactory = MediaWikiServices::getInstance()->getDBLoadBalancerFactory();
 674                 $res = wfGetDB( DB_REPLICA )->select(
 675                         [ 'text', 'blob_tracking' ],
 676                         [ 'old_id', 'old_text', 'old_flags' ],
 677                         [
 678                                 'old_id' => $textIds,
 679                                 'bt_text_id=old_id',
 680                                 'bt_moved' => 0,
 681                         ],
 682                         __METHOD__,
 683                         [ 'DISTINCT' ]
 684                 );
 685
 686                 foreach ( $res as $row ) {
 687                         $text = Revision::getRevisionText( $row );
 688                         if ( $text === false ) {
 689                                 $this->critical( "Error: cannot load revision text for old_id={$row->old_id}" );
 690                                 continue;
 691                         }
 692
 693                         if ( !$trx->addItem( $text, $row->old_id ) ) {
 694                                 $this->debug( "[orphan]: committing blob with " . $trx->getSize() . " rows" );
 695                                 $trx->commit();
 696                                 $trx = new CgzCopyTransaction( $this, $this->orphanBlobClass );
 697                                 $lbFactory->waitForReplication();
 698                         }
 699                 }
 700                 $this->debug( "[orphan]: committing blob with " . $trx->getSize() . " rows" );
 701                 $trx->commit();
 702         }
 703 }
 704
 705 /**
 706  * Class to represent a recompression operation for a single CGZ blob
 707  */
 708 class CgzCopyTransaction {
 709         /** @var RecompressTracked */
 710         public $parent;
 711         public $blobClass;
 712         /** @var ConcatenatedGzipHistoryBlob */
 713         public $cgz;
 714         public $referrers;
 715
 716         /**
 717          * Create a transaction from a RecompressTracked object
 718          * @param RecompressTracked $parent
 719          * @param string $blobClass
 720          */
 721         function __construct( $parent, $blobClass ) {
 722                 $this->blobClass = $blobClass;
 723                 $this->cgz = false;
 724                 $this->texts = [];
 725                 $this->parent = $parent;
 726         }
 727
 728         /**
 729          * Add text.
 730          * Returns false if it's ready to commit.
 731          * @param string $text
 732          * @param int $textId
 733          * @return bool
 734          */
 735         function addItem( $text, $textId ) {
 736                 if ( !$this->cgz ) {
 737                         $class = $this->blobClass;
 738                         $this->cgz = new $class;
 739                 }
 740                 $hash = $this->cgz->addItem( $text );
 741                 $this->referrers[$textId] = $hash;
 742                 $this->texts[$textId] = $text;
 743
 744                 return $this->cgz->isHappy();
 745         }
 746
 747         function getSize() {
 748                 return count( $this->texts );
 749         }
 750
 751         /**
 752          * Recompress text after some aberrant modification
 753          */
 754         function recompress() {
 755                 $class = $this->blobClass;
 756                 $this->cgz = new $class;
 757                 $this->referrers = [];
 758                 foreach ( $this->texts as $textId => $text ) {
 759                         $hash = $this->cgz->addItem( $text );
 760                         $this->referrers[$textId] = $hash;
 761                 }
 762         }
 763
 764         /**
 765          * Commit the blob.
 766          * Does nothing if no text items have been added.
 767          * May skip the move if --copy-only is set.
 768          */
 769         function commit() {
 770                 $originalCount = count( $this->texts );
 771                 if ( !$originalCount ) {
 772                         return;
 773                 }
 774
 775                 /* Check to see if the target text_ids have been moved already.
 776                  *
 777                  * We originally read from the replica DB, so this can happen when a single
 778                  * text_id is shared between multiple pages. It's rare, but possible
 779                  * if a delete/move/undelete cycle splits up a null edit.
 780                  *
 781                  * We do a locking read to prevent closer-run race conditions.
 782                  */
 783                 $dbw = wfGetDB( DB_MASTER );
 784                 $dbw->begin( __METHOD__ );
 785                 $res = $dbw->select( 'blob_tracking',
 786                         [ 'bt_text_id', 'bt_moved' ],
 787                         [ 'bt_text_id' => array_keys( $this->referrers ) ],
 788                         __METHOD__, [ 'FOR UPDATE' ] );
 789                 $dirty = false;
 790                 foreach ( $res as $row ) {
 791                         if ( $row->bt_moved ) {
 792                                 # This row has already been moved, remove it
 793                                 $this->parent->debug( "TRX: conflict detected in old_id={$row->bt_text_id}" );
 794                                 unset( $this->texts[$row->bt_text_id] );
 795                                 $dirty = true;
 796                         }
 797                 }
 798
 799                 // Recompress the blob if necessary
 800                 if ( $dirty ) {
 801                         if ( !count( $this->texts ) ) {
 802                                 // All have been moved already
 803                                 if ( $originalCount > 1 ) {
 804                                         // This is suspcious, make noise
 805                                         $this->parent->critical(
 806                                                 "Warning: concurrent operation detected, are there two conflicting " .
 807                                                 "processes running, doing the same job?" );
 808                                 }
 809
 810                                 return;
 811                         }
 812                         $this->recompress();
 813                 }
 814
 815                 // Insert the data into the destination cluster
 816                 $targetCluster = $this->parent->getTargetCluster();
 817                 $store = $this->parent->store;
 818                 $targetDB = $store->getMaster( $targetCluster );
 819                 $targetDB->clearFlag( DBO_TRX ); // we manage the transactions
 820                 $targetDB->begin( __METHOD__ );
 821                 $baseUrl = $this->parent->store->store( $targetCluster, serialize( $this->cgz ) );
 822
 823                 // Write the new URLs to the blob_tracking table
 824                 foreach ( $this->referrers as $textId => $hash ) {
 825                         $url = $baseUrl . '/' . $hash;
 826                         $dbw->update( 'blob_tracking',
 827                                 [ 'bt_new_url' => $url ],
 828                                 [
 829                                         'bt_text_id' => $textId,
 830                                         'bt_moved' => 0, # Check for concurrent conflicting update
 831                                 ],
 832                                 __METHOD__
 833                         );
 834                 }
 835
 836                 $targetDB->commit( __METHOD__ );
 837                 // Critical section here: interruption at this point causes blob duplication
 838                 // Reversing the order of the commits would cause data loss instead
 839                 $dbw->commit( __METHOD__ );
 840
 841                 // Write the new URLs to the text table and set the moved flag
 842                 if ( !$this->parent->copyOnly ) {
 843                         foreach ( $this->referrers as $textId => $hash ) {
 844                                 $url = $baseUrl . '/' . $hash;
 845                                 $this->parent->moveTextRow( $textId, $url );
 846                         }
 847                 }
 848         }
 849 }