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 $optionsWithArgs = RecompressTracked::getOptionsWithArgs();
  26 require __DIR__ . '/../commandLine.inc';
  27
  28 if ( count( $args ) < 1 ) {
  29         echo "Usage: php recompressTracked.php [options] <cluster> [... <cluster>...]
  30 Moves blobs indexed by trackBlobs.php to a specified list of destination clusters,
  31 and recompresses them in the process. Restartable.
  32
  33 Options:
  34         --procs <procs>       Set the number of child processes (default 1)
  35         --copy-only           Copy only, do not update the text table. Restart
  36                               without this option to complete.
  37         --debug-log <file>    Log debugging data to the specified file
  38         --info-log <file>     Log progress messages to the specified file
  39         --critical-log <file> Log error messages to the specified file
  40 ";
  41         exit( 1 );
  42 }
  43
  44 $job = RecompressTracked::newFromCommandLine( $args, $options );
  45 $job->execute();
  46
  47 /**
  48  * Maintenance script that moves blobs indexed by trackBlobs.php to a specified
  49  * list of destination clusters, and recompresses them in the process.
  50  *
  51  * @ingroup Maintenance ExternalStorage
  52  */
  53 class RecompressTracked {
  54         public $destClusters;
  55         public $batchSize = 1000;
  56         public $orphanBatchSize = 1000;
  57         public $reportingInterval = 10;
  58         public $numProcs = 1;
  59         public $useDiff, $pageBlobClass, $orphanBlobClass;
  60         public $slavePipes, $slaveProcs, $prevSlaveId;
  61         public $copyOnly = false;
  62         public $isChild = false;
  63         public $slaveId = false;
  64         public $noCount = false;
  65         public $debugLog, $infoLog, $criticalLog;
  66         public $store;
  67
  68         private static $optionsWithArgs = array(
  69                 'procs',
  70                 'slave-id',
  71                 'debug-log',
  72                 'info-log',
  73                 'critical-log'
  74         );
  75
  76         private static $cmdLineOptionMap = array(
  77                 'no-count' => 'noCount',
  78                 'procs' => 'numProcs',
  79                 'copy-only' => 'copyOnly',
  80                 'child' => 'isChild',
  81                 'slave-id' => 'slaveId',
  82                 'debug-log' => 'debugLog',
  83                 'info-log' => 'infoLog',
  84                 'critical-log' => 'criticalLog',
  85         );
  86
  87         static function getOptionsWithArgs() {
  88                 return self::$optionsWithArgs;
  89         }
  90
  91         static function newFromCommandLine( $args, $options ) {
  92                 $jobOptions = array( 'destClusters' => $args );
  93                 foreach ( self::$cmdLineOptionMap as $cmdOption => $classOption ) {
  94                         if ( isset( $options[$cmdOption] ) ) {
  95                                 $jobOptions[$classOption] = $options[$cmdOption];
  96                         }
  97                 }
  98
  99                 return new self( $jobOptions );
 100         }
 101
 102         function __construct( $options ) {
 103                 foreach ( $options as $name => $value ) {
 104                         $this->$name = $value;
 105                 }
 106                 $this->store = new ExternalStoreDB;
 107                 if ( !$this->isChild ) {
 108                         $GLOBALS['wgDebugLogPrefix'] = "RCT M: ";
 109                 } elseif ( $this->slaveId !== false ) {
 110                         $GLOBALS['wgDebugLogPrefix'] = "RCT {$this->slaveId}: ";
 111                 }
 112                 $this->useDiff = function_exists( 'xdiff_string_bdiff' );
 113                 $this->pageBlobClass = $this->useDiff ? 'DiffHistoryBlob' : 'ConcatenatedGzipHistoryBlob';
 114                 $this->orphanBlobClass = 'ConcatenatedGzipHistoryBlob';
 115         }
 116
 117         function debug( $msg ) {
 118                 wfDebug( "$msg\n" );
 119                 if ( $this->debugLog ) {
 120                         $this->logToFile( $msg, $this->debugLog );
 121                 }
 122         }
 123
 124         function info( $msg ) {
 125                 echo "$msg\n";
 126                 if ( $this->infoLog ) {
 127                         $this->logToFile( $msg, $this->infoLog );
 128                 }
 129         }
 130
 131         function critical( $msg ) {
 132                 echo "$msg\n";
 133                 if ( $this->criticalLog ) {
 134                         $this->logToFile( $msg, $this->criticalLog );
 135                 }
 136         }
 137
 138         function logToFile( $msg, $file ) {
 139                 $header = '[' . date( 'd\TH:i:s' ) . '] ' . wfHostname() . ' ' . posix_getpid();
 140                 if ( $this->slaveId !== false ) {
 141                         $header .= "({$this->slaveId})";
 142                 }
 143                 $header .= ' ' . wfWikiID();
 144                 wfErrorLog( sprintf( "%-50s %s\n", $header, $msg ), $file );
 145         }
 146
 147         /**
 148          * Wait until the selected slave has caught up to the master.
 149          * This allows us to use the slave for things that were committed in a
 150          * previous part of this batch process.
 151          */
 152         function syncDBs() {
 153                 $dbw = wfGetDB( DB_MASTER );
 154                 $dbr = wfGetDB( DB_SLAVE );
 155                 $pos = $dbw->getMasterPos();
 156                 $dbr->masterPosWait( $pos, 100000 );
 157         }
 158
 159         /**
 160          * Execute parent or child depending on the isChild option
 161          */
 162         function execute() {
 163                 if ( $this->isChild ) {
 164                         $this->executeChild();
 165                 } else {
 166                         $this->executeParent();
 167                 }
 168         }
 169
 170         /**
 171          * Execute the parent process
 172          */
 173         function executeParent() {
 174                 if ( !$this->checkTrackingTable() ) {
 175                         return;
 176                 }
 177
 178                 $this->syncDBs();
 179                 $this->startSlaveProcs();
 180                 $this->doAllPages();
 181                 $this->doAllOrphans();
 182                 $this->killSlaveProcs();
 183         }
 184
 185         /**
 186          * Make sure the tracking table exists and isn't empty
 187          * @return bool
 188          */
 189         function checkTrackingTable() {
 190                 $dbr = wfGetDB( DB_SLAVE );
 191                 if ( !$dbr->tableExists( 'blob_tracking' ) ) {
 192                         $this->critical( "Error: blob_tracking table does not exist" );
 193
 194                         return false;
 195                 }
 196                 $row = $dbr->selectRow( 'blob_tracking', '*', false, __METHOD__ );
 197                 if ( !$row ) {
 198                         $this->info( "Warning: blob_tracking table contains no rows, skipping this wiki." );
 199
 200                         return false;
 201                 }
 202
 203                 return true;
 204         }
 205
 206         /**
 207          * Start the worker processes.
 208          * These processes will listen on stdin for commands.
 209          * This necessary because text recompression is slow: loading, compressing and
 210          * writing are all slow.
 211          */
 212         function startSlaveProcs() {
 213                 $cmd = 'php ' . wfEscapeShellArg( __FILE__ );
 214                 foreach ( self::$cmdLineOptionMap as $cmdOption => $classOption ) {
 215                         if ( $cmdOption == 'slave-id' ) {
 216                                 continue;
 217                         } elseif ( in_array( $cmdOption, self::$optionsWithArgs ) && isset( $this->$classOption ) ) {
 218                                 $cmd .= " --$cmdOption " . wfEscapeShellArg( $this->$classOption );
 219                         } elseif ( $this->$classOption ) {
 220                                 $cmd .= " --$cmdOption";
 221                         }
 222                 }
 223                 $cmd .= ' --child' .
 224                         ' --wiki ' . wfEscapeShellArg( wfWikiID() ) .
 225                         ' ' . call_user_func_array( 'wfEscapeShellArg', $this->destClusters );
 226
 227                 $this->slavePipes = $this->slaveProcs = array();
 228                 for ( $i = 0; $i < $this->numProcs; $i++ ) {
 229                         $pipes = false;
 230                         $spec = array(
 231                                 array( 'pipe', 'r' ),
 232                                 array( 'file', 'php://stdout', 'w' ),
 233                                 array( 'file', 'php://stderr', 'w' )
 234                         );
 235                         wfSuppressWarnings();
 236                         $proc = proc_open( "$cmd --slave-id $i", $spec, $pipes );
 237                         wfRestoreWarnings();
 238                         if ( !$proc ) {
 239                                 $this->critical( "Error opening slave process: $cmd" );
 240                                 exit( 1 );
 241                         }
 242                         $this->slaveProcs[$i] = $proc;
 243                         $this->slavePipes[$i] = $pipes[0];
 244                 }
 245                 $this->prevSlaveId = -1;
 246         }
 247
 248         /**
 249          * Gracefully terminate the child processes
 250          */
 251         function killSlaveProcs() {
 252                 $this->info( "Waiting for slave processes to finish..." );
 253                 for ( $i = 0; $i < $this->numProcs; $i++ ) {
 254                         $this->dispatchToSlave( $i, 'quit' );
 255                 }
 256                 for ( $i = 0; $i < $this->numProcs; $i++ ) {
 257                         $status = proc_close( $this->slaveProcs[$i] );
 258                         if ( $status ) {
 259                                 $this->critical( "Warning: child #$i exited with status $status" );
 260                         }
 261                 }
 262                 $this->info( "Done." );
 263         }
 264
 265         /**
 266          * Dispatch a command to the next available slave.
 267          * This may block until a slave finishes its work and becomes available.
 268          */
 269         function dispatch( /*...*/ ) {
 270                 $args = func_get_args();
 271                 $pipes = $this->slavePipes;
 272                 $numPipes = stream_select( $x = array(), $pipes, $y = array(), 3600 );
 273                 if ( !$numPipes ) {
 274                         $this->critical( "Error waiting to write to slaves. Aborting" );
 275                         exit( 1 );
 276                 }
 277                 for ( $i = 0; $i < $this->numProcs; $i++ ) {
 278                         $slaveId = ( $i + $this->prevSlaveId + 1 ) % $this->numProcs;
 279                         if ( isset( $pipes[$slaveId] ) ) {
 280                                 $this->prevSlaveId = $slaveId;
 281                                 $this->dispatchToSlave( $slaveId, $args );
 282
 283                                 return;
 284                         }
 285                 }
 286                 $this->critical( "Unreachable" );
 287                 exit( 1 );
 288         }
 289
 290         /**
 291          * Dispatch a command to a specified slave
 292          * @param int $slaveId
 293          * @param array|string $args
 294          */
 295         function dispatchToSlave( $slaveId, $args ) {
 296                 $args = (array)$args;
 297                 $cmd = implode( ' ', $args );
 298                 fwrite( $this->slavePipes[$slaveId], "$cmd\n" );
 299         }
 300
 301         /**
 302          * Move all tracked pages to the new clusters
 303          */
 304         function doAllPages() {
 305                 $dbr = wfGetDB( DB_SLAVE );
 306                 $i = 0;
 307                 $startId = 0;
 308                 if ( $this->noCount ) {
 309                         $numPages = '[unknown]';
 310                 } else {
 311                         $numPages = $dbr->selectField( 'blob_tracking',
 312                                 'COUNT(DISTINCT bt_page)',
 313                                 # A condition is required so that this query uses the index
 314                                 array( 'bt_moved' => 0 ),
 315                                 __METHOD__
 316                         );
 317                 }
 318                 if ( $this->copyOnly ) {
 319                         $this->info( "Copying pages..." );
 320                 } else {
 321                         $this->info( "Moving pages..." );
 322                 }
 323                 while ( true ) {
 324                         $res = $dbr->select( 'blob_tracking',
 325                                 array( 'bt_page' ),
 326                                 array(
 327                                         'bt_moved' => 0,
 328                                         'bt_page > ' . $dbr->addQuotes( $startId )
 329                                 ),
 330                                 __METHOD__,
 331                                 array(
 332                                         'DISTINCT',
 333                                         'ORDER BY' => 'bt_page',
 334                                         'LIMIT' => $this->batchSize,
 335                                 )
 336                         );
 337                         if ( !$res->numRows() ) {
 338                                 break;
 339                         }
 340                         foreach ( $res as $row ) {
 341                                 $this->dispatch( 'doPage', $row->bt_page );
 342                                 $i++;
 343                         }
 344                         $startId = $row->bt_page;
 345                         $this->report( 'pages', $i, $numPages );
 346                 }
 347                 $this->report( 'pages', $i, $numPages );
 348                 if ( $this->copyOnly ) {
 349                         $this->info( "All page copies queued." );
 350                 } else {
 351                         $this->info( "All page moves queued." );
 352                 }
 353         }
 354
 355         /**
 356          * Display a progress report
 357          * @param string $label
 358          * @param int $current
 359          * @param int $end
 360          */
 361         function report( $label, $current, $end ) {
 362                 $this->numBatches++;
 363                 if ( $current == $end || $this->numBatches >= $this->reportingInterval ) {
 364                         $this->numBatches = 0;
 365                         $this->info( "$label: $current / $end" );
 366                         $this->waitForSlaves();
 367                 }
 368         }
 369
 370         /**
 371          * Move all orphan text to the new clusters
 372          */
 373         function doAllOrphans() {
 374                 $dbr = wfGetDB( DB_SLAVE );
 375                 $startId = 0;
 376                 $i = 0;
 377                 if ( $this->noCount ) {
 378                         $numOrphans = '[unknown]';
 379                 } else {
 380                         $numOrphans = $dbr->selectField( 'blob_tracking',
 381                                 'COUNT(DISTINCT bt_text_id)',
 382                                 array( 'bt_moved' => 0, 'bt_page' => 0 ),
 383                                 __METHOD__ );
 384                         if ( !$numOrphans ) {
 385                                 return;
 386                         }
 387                 }
 388                 if ( $this->copyOnly ) {
 389                         $this->info( "Copying orphans..." );
 390                 } else {
 391                         $this->info( "Moving orphans..." );
 392                 }
 393
 394                 while ( true ) {
 395                         $res = $dbr->select( 'blob_tracking',
 396                                 array( 'bt_text_id' ),
 397                                 array(
 398                                         'bt_moved' => 0,
 399                                         'bt_page' => 0,
 400                                         'bt_text_id > ' . $dbr->addQuotes( $startId )
 401                                 ),
 402                                 __METHOD__,
 403                                 array(
 404                                         'DISTINCT',
 405                                         'ORDER BY' => 'bt_text_id',
 406                                         'LIMIT' => $this->batchSize
 407                                 )
 408                         );
 409                         if ( !$res->numRows() ) {
 410                                 break;
 411                         }
 412                         $ids = array();
 413                         foreach ( $res as $row ) {
 414                                 $ids[] = $row->bt_text_id;
 415                                 $i++;
 416                         }
 417                         // Need to send enough orphan IDs to the child at a time to fill a blob,
 418                         // so orphanBatchSize needs to be at least ~100.
 419                         // batchSize can be smaller or larger.
 420                         while ( count( $ids ) > $this->orphanBatchSize ) {
 421                                 $args = array_slice( $ids, 0, $this->orphanBatchSize );
 422                                 $ids = array_slice( $ids, $this->orphanBatchSize );
 423                                 array_unshift( $args, 'doOrphanList' );
 424                                 call_user_func_array( array( $this, 'dispatch' ), $args );
 425                         }
 426                         if ( count( $ids ) ) {
 427                                 $args = $ids;
 428                                 array_unshift( $args, 'doOrphanList' );
 429                                 call_user_func_array( array( $this, 'dispatch' ), $args );
 430                         }
 431
 432                         $startId = $row->bt_text_id;
 433                         $this->report( 'orphans', $i, $numOrphans );
 434                 }
 435                 $this->report( 'orphans', $i, $numOrphans );
 436                 $this->info( "All orphans queued." );
 437         }
 438
 439         /**
 440          * Main entry point for worker processes
 441          */
 442         function executeChild() {
 443                 $this->debug( 'starting' );
 444                 $this->syncDBs();
 445
 446                 while ( !feof( STDIN ) ) {
 447                         $line = rtrim( fgets( STDIN ) );
 448                         if ( $line == '' ) {
 449                                 continue;
 450                         }
 451                         $this->debug( $line );
 452                         $args = explode( ' ', $line );
 453                         $cmd = array_shift( $args );
 454                         switch ( $cmd ) {
 455                                 case 'doPage':
 456                                         $this->doPage( intval( $args[0] ) );
 457                                         break;
 458                                 case 'doOrphanList':
 459                                         $this->doOrphanList( array_map( 'intval', $args ) );
 460                                         break;
 461                                 case 'quit':
 462                                         return;
 463                         }
 464                         $this->waitForSlaves();
 465                 }
 466         }
 467
 468         /**
 469          * Move tracked text in a given page
 470          *
 471          * @param int $pageId
 472          */
 473         function doPage( $pageId ) {
 474                 $title = Title::newFromId( $pageId );
 475                 if ( $title ) {
 476                         $titleText = $title->getPrefixedText();
 477                 } else {
 478                         $titleText = '[deleted]';
 479                 }
 480                 $dbr = wfGetDB( DB_SLAVE );
 481
 482                 // Finish any incomplete transactions
 483                 if ( !$this->copyOnly ) {
 484                         $this->finishIncompleteMoves( array( 'bt_page' => $pageId ) );
 485                         $this->syncDBs();
 486                 }
 487
 488                 $startId = 0;
 489                 $trx = new CgzCopyTransaction( $this, $this->pageBlobClass );
 490
 491                 while ( true ) {
 492                         $res = $dbr->select(
 493                                 array( 'blob_tracking', 'text' ),
 494                                 '*',
 495                                 array(
 496                                         'bt_page' => $pageId,
 497                                         'bt_text_id > ' . $dbr->addQuotes( $startId ),
 498                                         'bt_moved' => 0,
 499                                         'bt_new_url IS NULL',
 500                                         'bt_text_id=old_id',
 501                                 ),
 502                                 __METHOD__,
 503                                 array(
 504                                         'ORDER BY' => 'bt_text_id',
 505                                         'LIMIT' => $this->batchSize
 506                                 )
 507                         );
 508                         if ( !$res->numRows() ) {
 509                                 break;
 510                         }
 511
 512                         $lastTextId = 0;
 513                         foreach ( $res as $row ) {
 514                                 if ( $lastTextId == $row->bt_text_id ) {
 515                                         // Duplicate (null edit)
 516                                         continue;
 517                                 }
 518                                 $lastTextId = $row->bt_text_id;
 519                                 // Load the text
 520                                 $text = Revision::getRevisionText( $row );
 521                                 if ( $text === false ) {
 522                                         $this->critical( "Error loading {$row->bt_rev_id}/{$row->bt_text_id}" );
 523                                         continue;
 524                                 }
 525
 526                                 // Queue it
 527                                 if ( !$trx->addItem( $text, $row->bt_text_id ) ) {
 528                                         $this->debug( "$titleText: committing blob with " . $trx->getSize() . " items" );
 529                                         $trx->commit();
 530                                         $trx = new CgzCopyTransaction( $this, $this->pageBlobClass );
 531                                         $this->waitForSlaves();
 532                                 }
 533                         }
 534                         $startId = $row->bt_text_id;
 535                 }
 536
 537                 $this->debug( "$titleText: committing blob with " . $trx->getSize() . " items" );
 538                 $trx->commit();
 539         }
 540
 541         /**
 542          * Atomic move operation.
 543          *
 544          * Write the new URL to the text table and set the bt_moved flag.
 545          *
 546          * This is done in a single transaction to provide restartable behavior
 547          * without data loss.
 548          *
 549          * The transaction is kept short to reduce locking.
 550          *
 551          * @param int $textId
 552          * @param string $url
 553          */
 554         function moveTextRow( $textId, $url ) {
 555                 if ( $this->copyOnly ) {
 556                         $this->critical( "Internal error: can't call moveTextRow() in --copy-only mode" );
 557                         exit( 1 );
 558                 }
 559                 $dbw = wfGetDB( DB_MASTER );
 560                 $dbw->begin( __METHOD__ );
 561                 $dbw->update( 'text',
 562                         array( // set
 563                                 'old_text' => $url,
 564                                 'old_flags' => 'external,utf-8',
 565                         ),
 566                         array( // where
 567                                 'old_id' => $textId
 568                         ),
 569                         __METHOD__
 570                 );
 571                 $dbw->update( 'blob_tracking',
 572                         array( 'bt_moved' => 1 ),
 573                         array( 'bt_text_id' => $textId ),
 574                         __METHOD__
 575                 );
 576                 $dbw->commit( __METHOD__ );
 577         }
 578
 579         /**
 580          * Moves are done in two phases: bt_new_url and then bt_moved.
 581          *  - bt_new_url indicates that the text has been copied to the new cluster.
 582          *  - bt_moved indicates that the text table has been updated.
 583          *
 584          * This function completes any moves that only have done bt_new_url. This
 585          * can happen when the script is interrupted, or when --copy-only is used.
 586          *
 587          * @param array $conds
 588          */
 589         function finishIncompleteMoves( $conds ) {
 590                 $dbr = wfGetDB( DB_SLAVE );
 591
 592                 $startId = 0;
 593                 $conds = array_merge( $conds, array(
 594                         'bt_moved' => 0,
 595                         'bt_new_url IS NOT NULL'
 596                 ) );
 597                 while ( true ) {
 598                         $res = $dbr->select( 'blob_tracking',
 599                                 '*',
 600                                 array_merge( $conds, array( 'bt_text_id > ' . $dbr->addQuotes( $startId ) ) ),
 601                                 __METHOD__,
 602                                 array(
 603                                         'ORDER BY' => 'bt_text_id',
 604                                         'LIMIT' => $this->batchSize,
 605                                 )
 606                         );
 607                         if ( !$res->numRows() ) {
 608                                 break;
 609                         }
 610                         $this->debug( 'Incomplete: ' . $res->numRows() . ' rows' );
 611                         foreach ( $res as $row ) {
 612                                 $this->moveTextRow( $row->bt_text_id, $row->bt_new_url );
 613                                 if ( $row->bt_text_id % 10 == 0 ) {
 614                                         $this->waitForSlaves();
 615                                 }
 616                         }
 617                         $startId = $row->bt_text_id;
 618                 }
 619         }
 620
 621         /**
 622          * Returns the name of the next target cluster
 623          * @return string
 624          */
 625         function getTargetCluster() {
 626                 $cluster = next( $this->destClusters );
 627                 if ( $cluster === false ) {
 628                         $cluster = reset( $this->destClusters );
 629                 }
 630
 631                 return $cluster;
 632         }
 633
 634         /**
 635          * Gets a DB master connection for the given external cluster name
 636          * @param string $cluster
 637          * @return DatabaseBase
 638          */
 639         function getExtDB( $cluster ) {
 640                 $lb = wfGetLBFactory()->getExternalLB( $cluster );
 641
 642                 return $lb->getConnection( DB_MASTER );
 643         }
 644
 645         /**
 646          * Move an orphan text_id to the new cluster
 647          *
 648          * @param array $textIds
 649          */
 650         function doOrphanList( $textIds ) {
 651                 // Finish incomplete moves
 652                 if ( !$this->copyOnly ) {
 653                         $this->finishIncompleteMoves( array( 'bt_text_id' => $textIds ) );
 654                         $this->syncDBs();
 655                 }
 656
 657                 $trx = new CgzCopyTransaction( $this, $this->orphanBlobClass );
 658
 659                 $res = wfGetDB( DB_SLAVE )->select(
 660                         array( 'text', 'blob_tracking' ),
 661                         array( 'old_id', 'old_text', 'old_flags' ),
 662                         array(
 663                                 'old_id' => $textIds,
 664                                 'bt_text_id=old_id',
 665                                 'bt_moved' => 0,
 666                         ),
 667                         __METHOD__,
 668                         array( 'DISTINCT' )
 669                 );
 670
 671                 foreach ( $res as $row ) {
 672                         $text = Revision::getRevisionText( $row );
 673                         if ( $text === false ) {
 674                                 $this->critical( "Error: cannot load revision text for old_id={$row->old_id}" );
 675                                 continue;
 676                         }
 677
 678                         if ( !$trx->addItem( $text, $row->old_id ) ) {
 679                                 $this->debug( "[orphan]: committing blob with " . $trx->getSize() . " rows" );
 680                                 $trx->commit();
 681                                 $trx = new CgzCopyTransaction( $this, $this->orphanBlobClass );
 682                                 $this->waitForSlaves();
 683                         }
 684                 }
 685                 $this->debug( "[orphan]: committing blob with " . $trx->getSize() . " rows" );
 686                 $trx->commit();
 687         }
 688
 689         /**
 690          * Wait for slaves (quietly)
 691          */
 692         function waitForSlaves() {
 693                 $lb = wfGetLB();
 694                 while ( true ) {
 695                         list( $host, $maxLag ) = $lb->getMaxLag();
 696                         if ( $maxLag < 2 ) {
 697                                 break;
 698                         }
 699                         sleep( 5 );
 700                 }
 701         }
 702 }
 703
 704 /**
 705  * Class to represent a recompression operation for a single CGZ blob
 706  */
 707 class CgzCopyTransaction {
 708         public $parent;
 709         public $blobClass;
 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 = array();
 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 = array();
 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 slave, 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                 $dbw = wfGetDB( DB_MASTER );
 780                 $dbw->begin( __METHOD__ );
 781                 $res = $dbw->select( 'blob_tracking',
 782                         array( 'bt_text_id', 'bt_moved' ),
 783                         array( 'bt_text_id' => array_keys( $this->referrers ) ),
 784                         __METHOD__, array( '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->critical( "Warning: concurrent operation detected, are there two conflicting " .
 802                                                 "processes running, doing the same job?" );
 803                                 }
 804
 805                                 return;
 806                         }
 807                         $this->recompress();
 808                 }
 809
 810                 // Insert the data into the destination cluster
 811                 $targetCluster = $this->parent->getTargetCluster();
 812                 $store = $this->parent->store;
 813                 $targetDB = $store->getMaster( $targetCluster );
 814                 $targetDB->clearFlag( DBO_TRX ); // we manage the transactions
 815                 $targetDB->begin( __METHOD__ );
 816                 $baseUrl = $this->parent->store->store( $targetCluster, serialize( $this->cgz ) );
 817
 818                 // Write the new URLs to the blob_tracking table
 819                 foreach ( $this->referrers as $textId => $hash ) {
 820                         $url = $baseUrl . '/' . $hash;
 821                         $dbw->update( 'blob_tracking',
 822                                 array( 'bt_new_url' => $url ),
 823                                 array(
 824                                         'bt_text_id' => $textId,
 825                                         'bt_moved' => 0, # Check for concurrent conflicting update
 826                                 ),
 827                                 __METHOD__
 828                         );
 829                 }
 830
 831                 $targetDB->commit( __METHOD__ );
 832                 // Critical section here: interruption at this point causes blob duplication
 833                 // Reversing the order of the commits would cause data loss instead
 834                 $dbw->commit( __METHOD__ );
 835
 836                 // Write the new URLs to the text table and set the moved flag
 837                 if ( !$this->parent->copyOnly ) {
 838                         foreach ( $this->referrers as $textId => $hash ) {
 839                                 $url = $baseUrl . '/' . $hash;
 840                                 $this->parent->moveTextRow( $textId, $url );
 841                         }
 842                 }
 843         }
 844 }