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