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