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