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, and recompresses them in the process. Restartable.
  31
  32 Options:
  33         --procs <procs>         Set the number of child processes (default 1)
  34         --copy-only             Copy only, do not update the text table. Restart without this option to complete.
  35         --debug-log <file>      Log debugging data to the specified file
  36         --info-log <file>       Log progress messages to the specified file
  37         --critical-log <file>   Log error messages to the specified file
  38 ";
  39         exit( 1 );
  40 }
  41
  42 $job = RecompressTracked::newFromCommandLine( $args, $options );
  43 $job->execute();
  44
  45 /**
  46  * Maintenance script that moves blobs indexed by trackBlobs.php to a specified
  47  * list of destination clusters, and recompresses them in the process.
  48  *
  49  * @ingroup Maintenance ExternalStorage
  50  */
  51 class RecompressTracked {
  52         public $destClusters;
  53         public $batchSize = 1000;
  54         public $orphanBatchSize = 1000;
  55         public $reportingInterval = 10;
  56         public $numProcs = 1;
  57         public $useDiff, $pageBlobClass, $orphanBlobClass;
  58         public $slavePipes, $slaveProcs, $prevSlaveId;
  59         public $copyOnly = false;
  60         public $isChild = false;
  61         public $slaveId = false;
  62         public $noCount = false;
  63         public $debugLog, $infoLog, $criticalLog;
  64         public $store;
  65
  66         static $optionsWithArgs = array( 'procs', 'slave-id', 'debug-log', 'info-log', 'critical-log' );
  67         static $cmdLineOptionMap = array(
  68                 'no-count' => 'noCount',
  69                 'procs' => 'numProcs',
  70                 'copy-only' => 'copyOnly',
  71                 'child' => 'isChild',
  72                 'slave-id' => 'slaveId',
  73                 'debug-log' => 'debugLog',
  74                 'info-log' => 'infoLog',
  75                 'critical-log' => 'criticalLog',
  76         );
  77
  78         static function getOptionsWithArgs() {
  79                 return self::$optionsWithArgs;
  80         }
  81
  82         static function newFromCommandLine( $args, $options ) {
  83                 $jobOptions = array( 'destClusters' => $args );
  84                 foreach ( self::$cmdLineOptionMap as $cmdOption => $classOption ) {
  85                         if ( isset( $options[$cmdOption] ) ) {
  86                                 $jobOptions[$classOption] = $options[$cmdOption];
  87                         }
  88                 }
  89                 return new self( $jobOptions );
  90         }
  91
  92         function __construct( $options ) {
  93                 foreach ( $options as $name => $value ) {
  94                         $this->$name = $value;
  95                 }
  96                 $this->store = new ExternalStoreDB;
  97                 if ( !$this->isChild ) {
  98                         $GLOBALS['wgDebugLogPrefix'] = "RCT M: ";
  99                 } elseif ( $this->slaveId !== false ) {
 100                         $GLOBALS['wgDebugLogPrefix'] = "RCT {$this->slaveId}: ";
 101                 }
 102                 $this->useDiff = function_exists( 'xdiff_string_bdiff' );
 103                 $this->pageBlobClass = $this->useDiff ? 'DiffHistoryBlob' : 'ConcatenatedGzipHistoryBlob';
 104                 $this->orphanBlobClass = 'ConcatenatedGzipHistoryBlob';
 105         }
 106
 107         function debug( $msg ) {
 108                 wfDebug( "$msg\n" );
 109                 if ( $this->debugLog ) {
 110                         $this->logToFile( $msg, $this->debugLog );
 111                 }
 112
 113         }
 114
 115         function info( $msg ) {
 116                 echo "$msg\n";
 117                 if ( $this->infoLog ) {
 118                         $this->logToFile( $msg, $this->infoLog );
 119                 }
 120         }
 121
 122         function critical( $msg ) {
 123                 echo "$msg\n";
 124                 if ( $this->criticalLog ) {
 125                         $this->logToFile( $msg, $this->criticalLog );
 126                 }
 127         }
 128
 129         function logToFile( $msg, $file ) {
 130                 $header = '[' . date( 'd\TH:i:s' ) . '] ' . wfHostname() . ' ' . posix_getpid();
 131                 if ( $this->slaveId !== false ) {
 132                         $header .= "({$this->slaveId})";
 133                 }
 134                 $header .= ' ' . wfWikiID();
 135                 wfErrorLog( sprintf( "%-50s %s\n", $header, $msg ), $file );
 136         }
 137
 138         /**
 139          * Wait until the selected slave has caught up to the master.
 140          * This allows us to use the slave for things that were committed in a
 141          * previous part of this batch process.
 142          */
 143         function syncDBs() {
 144                 $dbw = wfGetDB( DB_MASTER );
 145                 $dbr = wfGetDB( DB_SLAVE );
 146                 $pos = $dbw->getMasterPos();
 147                 $dbr->masterPosWait( $pos, 100000 );
 148         }
 149
 150         /**
 151          * Execute parent or child depending on the isChild option
 152          */
 153         function execute() {
 154                 if ( $this->isChild ) {
 155                         $this->executeChild();
 156                 } else {
 157                         $this->executeParent();
 158                 }
 159         }
 160
 161         /**
 162          * Execute the parent process
 163          */
 164         function executeParent() {
 165                 if ( !$this->checkTrackingTable() ) {
 166                         return;
 167                 }
 168
 169                 $this->syncDBs();
 170                 $this->startSlaveProcs();
 171                 $this->doAllPages();
 172                 $this->doAllOrphans();
 173                 $this->killSlaveProcs();
 174         }
 175
 176         /**
 177          * Make sure the tracking table exists and isn't empty
 178          * @return bool
 179          */
 180         function checkTrackingTable() {
 181                 $dbr = wfGetDB( DB_SLAVE );
 182                 if ( !$dbr->tableExists( 'blob_tracking' ) ) {
 183                         $this->critical( "Error: blob_tracking table does not exist" );
 184                         return false;
 185                 }
 186                 $row = $dbr->selectRow( 'blob_tracking', '*', false, __METHOD__ );
 187                 if ( !$row ) {
 188                         $this->info( "Warning: blob_tracking table contains no rows, skipping this wiki." );
 189                         return false;
 190                 }
 191                 return true;
 192         }
 193
 194         /**
 195          * Start the worker processes.
 196          * These processes will listen on stdin for commands.
 197          * This necessary because text recompression is slow: loading, compressing and
 198          * writing are all slow.
 199          */
 200         function startSlaveProcs() {
 201                 $cmd = 'php ' . wfEscapeShellArg( __FILE__ );
 202                 foreach ( self::$cmdLineOptionMap as $cmdOption => $classOption ) {
 203                         if ( $cmdOption == 'slave-id' ) {
 204                                 continue;
 205                         } elseif ( in_array( $cmdOption, self::$optionsWithArgs ) && isset( $this->$classOption ) ) {
 206                                 $cmd .= " --$cmdOption " . wfEscapeShellArg( $this->$classOption );
 207                         } elseif ( $this->$classOption ) {
 208                                 $cmd .= " --$cmdOption";
 209                         }
 210                 }
 211                 $cmd .= ' --child' .
 212                         ' --wiki ' . wfEscapeShellArg( wfWikiID() ) .
 213                         ' ' . call_user_func_array( 'wfEscapeShellArg', $this->destClusters );
 214
 215                 $this->slavePipes = $this->slaveProcs = array();
 216                 for ( $i = 0; $i < $this->numProcs; $i++ ) {
 217                         $pipes = false;
 218                         $spec = array(
 219                                 array( 'pipe', 'r' ),
 220                                 array( 'file', 'php://stdout', 'w' ),
 221                                 array( 'file', 'php://stderr', 'w' )
 222                         );
 223                         wfSuppressWarnings();
 224                         $proc = proc_open( "$cmd --slave-id $i", $spec, $pipes );
 225                         wfRestoreWarnings();
 226                         if ( !$proc ) {
 227                                 $this->critical( "Error opening slave process: $cmd" );
 228                                 exit( 1 );
 229                         }
 230                         $this->slaveProcs[$i] = $proc;
 231                         $this->slavePipes[$i] = $pipes[0];
 232                 }
 233                 $this->prevSlaveId = -1;
 234         }
 235
 236         /**
 237          * Gracefully terminate the child processes
 238          */
 239         function killSlaveProcs() {
 240                 $this->info( "Waiting for slave processes to finish..." );
 241                 for ( $i = 0; $i < $this->numProcs; $i++ ) {
 242                         $this->dispatchToSlave( $i, 'quit' );
 243                 }
 244                 for ( $i = 0; $i < $this->numProcs; $i++ ) {
 245                         $status = proc_close( $this->slaveProcs[$i] );
 246                         if ( $status ) {
 247                                 $this->critical( "Warning: child #$i exited with status $status" );
 248                         }
 249                 }
 250                 $this->info( "Done." );
 251         }
 252
 253         /**
 254          * Dispatch a command to the next available slave.
 255          * This may block until a slave finishes its work and becomes available.
 256          */
 257         function dispatch( /*...*/ ) {
 258                 $args = func_get_args();
 259                 $pipes = $this->slavePipes;
 260                 $numPipes = stream_select( $x = array(), $pipes, $y = array(), 3600 );
 261                 if ( !$numPipes ) {
 262                         $this->critical( "Error waiting to write to slaves. Aborting" );
 263                         exit( 1 );
 264                 }
 265                 for ( $i = 0; $i < $this->numProcs; $i++ ) {
 266                         $slaveId = ( $i + $this->prevSlaveId + 1 ) % $this->numProcs;
 267                         if ( isset( $pipes[$slaveId] ) ) {
 268                                 $this->prevSlaveId = $slaveId;
 269                                 $this->dispatchToSlave( $slaveId, $args );
 270                                 return;
 271                         }
 272                 }
 273                 $this->critical( "Unreachable" );
 274                 exit( 1 );
 275         }
 276
 277         /**
 278          * Dispatch a command to a specified slave
 279          */
 280         function dispatchToSlave( $slaveId, $args ) {
 281                 $args = (array)$args;
 282                 $cmd = implode( ' ', $args );
 283                 fwrite( $this->slavePipes[$slaveId], "$cmd\n" );
 284         }
 285
 286         /**
 287          * Move all tracked pages to the new clusters
 288          */
 289         function doAllPages() {
 290                 $dbr = wfGetDB( DB_SLAVE );
 291                 $i = 0;
 292                 $startId = 0;
 293                 if ( $this->noCount ) {
 294                         $numPages = '[unknown]';
 295                 } else {
 296                         $numPages = $dbr->selectField( 'blob_tracking',
 297                                 'COUNT(DISTINCT bt_page)',
 298                                 # A condition is required so that this query uses the index
 299                                 array( 'bt_moved' => 0 ),
 300                                 __METHOD__
 301                         );
 302                 }
 303                 if ( $this->copyOnly ) {
 304                         $this->info( "Copying pages..." );
 305                 } else {
 306                         $this->info( "Moving pages..." );
 307                 }
 308                 while ( true ) {
 309                         $res = $dbr->select( 'blob_tracking',
 310                                 array( 'bt_page' ),
 311                                 array(
 312                                         'bt_moved' => 0,
 313                                         'bt_page > ' . $dbr->addQuotes( $startId )
 314                                 ),
 315                                 __METHOD__,
 316                                 array(
 317                                         'DISTINCT',
 318                                         'ORDER BY' => 'bt_page',
 319                                         'LIMIT' => $this->batchSize,
 320                                 )
 321                         );
 322                         if ( !$res->numRows() ) {
 323                                 break;
 324                         }
 325                         foreach ( $res as $row ) {
 326                                 $this->dispatch( 'doPage', $row->bt_page );
 327                                 $i++;
 328                         }
 329                         $startId = $row->bt_page;
 330                         $this->report( 'pages', $i, $numPages );
 331                 }
 332                 $this->report( 'pages', $i, $numPages );
 333                 if ( $this->copyOnly ) {
 334                         $this->info( "All page copies queued." );
 335                 } else {
 336                         $this->info( "All page moves queued." );
 337                 }
 338         }
 339
 340         /**
 341          * Display a progress report
 342          */
 343         function report( $label, $current, $end ) {
 344                 $this->numBatches++;
 345                 if ( $current == $end || $this->numBatches >= $this->reportingInterval ) {
 346                         $this->numBatches = 0;
 347                         $this->info( "$label: $current / $end" );
 348                         $this->waitForSlaves();
 349                 }
 350         }
 351
 352         /**
 353          * Move all orphan text to the new clusters
 354          */
 355         function doAllOrphans() {
 356                 $dbr = wfGetDB( DB_SLAVE );
 357                 $startId = 0;
 358                 $i = 0;
 359                 if ( $this->noCount ) {
 360                         $numOrphans = '[unknown]';
 361                 } else {
 362                         $numOrphans = $dbr->selectField( 'blob_tracking',
 363                                 'COUNT(DISTINCT bt_text_id)',
 364                                 array( 'bt_moved' => 0, 'bt_page' => 0 ),
 365                                 __METHOD__ );
 366                         if ( !$numOrphans ) {
 367                                 return;
 368                         }
 369                 }
 370                 if ( $this->copyOnly ) {
 371                         $this->info( "Copying orphans..." );
 372                 } else {
 373                         $this->info( "Moving orphans..." );
 374                 }
 375
 376                 while ( true ) {
 377                         $res = $dbr->select( 'blob_tracking',
 378                                 array( 'bt_text_id' ),
 379                                 array(
 380                                         'bt_moved' => 0,
 381                                         'bt_page' => 0,
 382                                         'bt_text_id > ' . $dbr->addQuotes( $startId )
 383                                 ),
 384                                 __METHOD__,
 385                                 array(
 386                                         'DISTINCT',
 387                                         'ORDER BY' => 'bt_text_id',
 388                                         'LIMIT' => $this->batchSize
 389                                 )
 390                         );
 391                         if ( !$res->numRows() ) {
 392                                 break;
 393                         }
 394                         $ids = array();
 395                         foreach ( $res as $row ) {
 396                                 $ids[] = $row->bt_text_id;
 397                                 $i++;
 398                         }
 399                         // Need to send enough orphan IDs to the child at a time to fill a blob,
 400                         // so orphanBatchSize needs to be at least ~100.
 401                         // batchSize can be smaller or larger.
 402                         while ( count( $ids ) > $this->orphanBatchSize ) {
 403                                 $args = array_slice( $ids, 0, $this->orphanBatchSize );
 404                                 $ids = array_slice( $ids, $this->orphanBatchSize );
 405                                 array_unshift( $args, 'doOrphanList' );
 406                                 call_user_func_array( array( $this, 'dispatch' ), $args );
 407                         }
 408                         if ( count( $ids ) ) {
 409                                 $args = $ids;
 410                                 array_unshift( $args, 'doOrphanList' );
 411                                 call_user_func_array( array( $this, 'dispatch' ), $args );
 412                         }
 413
 414                         $startId = $row->bt_text_id;
 415                         $this->report( 'orphans', $i, $numOrphans );
 416                 }
 417                 $this->report( 'orphans', $i, $numOrphans );
 418                 $this->info( "All orphans queued." );
 419         }
 420
 421         /**
 422          * Main entry point for worker processes
 423          */
 424         function executeChild() {
 425                 $this->debug( 'starting' );
 426                 $this->syncDBs();
 427
 428                 while ( !feof( STDIN ) ) {
 429                         $line = rtrim( fgets( STDIN ) );
 430                         if ( $line == '' ) {
 431                                 continue;
 432                         }
 433                         $this->debug( $line );
 434                         $args = explode( ' ', $line );
 435                         $cmd = array_shift( $args );
 436                         switch ( $cmd ) {
 437                         case 'doPage':
 438                                 $this->doPage( intval( $args[0] ) );
 439                                 break;
 440                         case 'doOrphanList':
 441                                 $this->doOrphanList( array_map( 'intval', $args ) );
 442                                 break;
 443                         case 'quit':
 444                                 return;
 445                         }
 446                         $this->waitForSlaves();
 447                 }
 448         }
 449
 450         /**
 451          * Move tracked text in a given page
 452          */
 453         function doPage( $pageId ) {
 454                 $title = Title::newFromId( $pageId );
 455                 if ( $title ) {
 456                         $titleText = $title->getPrefixedText();
 457                 } else {
 458                         $titleText = '[deleted]';
 459                 }
 460                 $dbr = wfGetDB( DB_SLAVE );
 461
 462                 // Finish any incomplete transactions
 463                 if ( !$this->copyOnly ) {
 464                         $this->finishIncompleteMoves( array( 'bt_page' => $pageId ) );
 465                         $this->syncDBs();
 466                 }
 467
 468                 $startId = 0;
 469                 $trx = new CgzCopyTransaction( $this, $this->pageBlobClass );
 470
 471                 while ( true ) {
 472                         $res = $dbr->select(
 473                                 array( 'blob_tracking', 'text' ),
 474                                 '*',
 475                                 array(
 476                                         'bt_page' => $pageId,
 477                                         'bt_text_id > ' . $dbr->addQuotes( $startId ),
 478                                         'bt_moved' => 0,
 479                                         'bt_new_url IS NULL',
 480                                         'bt_text_id=old_id',
 481                                 ),
 482                                 __METHOD__,
 483                                 array(
 484                                         'ORDER BY' => 'bt_text_id',
 485                                         'LIMIT' => $this->batchSize
 486                                 )
 487                         );
 488                         if ( !$res->numRows() ) {
 489                                 break;
 490                         }
 491
 492                         $lastTextId = 0;
 493                         foreach ( $res as $row ) {
 494                                 if ( $lastTextId == $row->bt_text_id ) {
 495                                         // Duplicate (null edit)
 496                                         continue;
 497                                 }
 498                                 $lastTextId = $row->bt_text_id;
 499                                 // Load the text
 500                                 $text = Revision::getRevisionText( $row );
 501                                 if ( $text === false ) {
 502                                         $this->critical( "Error loading {$row->bt_rev_id}/{$row->bt_text_id}" );
 503                                         continue;
 504                                 }
 505
 506                                 // Queue it
 507                                 if ( !$trx->addItem( $text, $row->bt_text_id ) ) {
 508                                         $this->debug( "$titleText: committing blob with " . $trx->getSize() . " items" );
 509                                         $trx->commit();
 510                                         $trx = new CgzCopyTransaction( $this, $this->pageBlobClass );
 511                                         $this->waitForSlaves();
 512                                 }
 513                         }
 514                         $startId = $row->bt_text_id;
 515                 }
 516
 517                 $this->debug( "$titleText: committing blob with " . $trx->getSize() . " items" );
 518                 $trx->commit();
 519         }
 520
 521         /**
 522          * Atomic move operation.
 523          *
 524          * Write the new URL to the text table and set the bt_moved flag.
 525          *
 526          * This is done in a single transaction to provide restartable behavior
 527          * without data loss.
 528          *
 529          * The transaction is kept short to reduce locking.
 530          */
 531         function moveTextRow( $textId, $url ) {
 532                 if ( $this->copyOnly ) {
 533                         $this->critical( "Internal error: can't call moveTextRow() in --copy-only mode" );
 534                         exit( 1 );
 535                 }
 536                 $dbw = wfGetDB( DB_MASTER );
 537                 $dbw->begin( __METHOD__ );
 538                 $dbw->update( 'text',
 539                         array( // set
 540                                 'old_text' => $url,
 541                                 'old_flags' => 'external,utf-8',
 542                         ),
 543                         array( // where
 544                                 'old_id' => $textId
 545                         ),
 546                         __METHOD__
 547                 );
 548                 $dbw->update( 'blob_tracking',
 549                         array( 'bt_moved' => 1 ),
 550                         array( 'bt_text_id' => $textId ),
 551                         __METHOD__
 552                 );
 553                 $dbw->commit( __METHOD__ );
 554         }
 555
 556         /**
 557          * Moves are done in two phases: bt_new_url and then bt_moved.
 558          *  - bt_new_url indicates that the text has been copied to the new cluster.
 559          *  - bt_moved indicates that the text table has been updated.
 560          *
 561          * This function completes any moves that only have done bt_new_url. This
 562          * can happen when the script is interrupted, or when --copy-only is used.
 563          */
 564         function finishIncompleteMoves( $conds ) {
 565                 $dbr = wfGetDB( DB_SLAVE );
 566
 567                 $startId = 0;
 568                 $conds = array_merge( $conds, array(
 569                         'bt_moved' => 0,
 570                         'bt_new_url IS NOT NULL'
 571                 ) );
 572                 while ( true ) {
 573                         $res = $dbr->select( 'blob_tracking',
 574                                 '*',
 575                                 array_merge( $conds, array( 'bt_text_id > ' . $dbr->addQuotes( $startId ) ) ),
 576                                 __METHOD__,
 577                                 array(
 578                                         'ORDER BY' => 'bt_text_id',
 579                                         'LIMIT' => $this->batchSize,
 580                                 )
 581                         );
 582                         if ( !$res->numRows() ) {
 583                                 break;
 584                         }
 585                         $this->debug( 'Incomplete: ' . $res->numRows() . ' rows' );
 586                         foreach ( $res as $row ) {
 587                                 $this->moveTextRow( $row->bt_text_id, $row->bt_new_url );
 588                                 if ( $row->bt_text_id % 10 == 0 ) {
 589                                         $this->waitForSlaves();
 590                                 }
 591                         }
 592                         $startId = $row->bt_text_id;
 593                 }
 594         }
 595
 596         /**
 597          * Returns the name of the next target cluster
 598          * @return string
 599          */
 600         function getTargetCluster() {
 601                 $cluster = next( $this->destClusters );
 602                 if ( $cluster === false ) {
 603                         $cluster = reset( $this->destClusters );
 604                 }
 605                 return $cluster;
 606         }
 607
 608         /**
 609          * Gets a DB master connection for the given external cluster name
 610          * @param $cluster string
 611          * @return DatabaseBase
 612          */
 613         function getExtDB( $cluster ) {
 614                 $lb = wfGetLBFactory()->getExternalLB( $cluster );
 615                 return $lb->getConnection( DB_MASTER );
 616         }
 617
 618         /**
 619          * Move an orphan text_id to the new cluster
 620          */
 621         function doOrphanList( $textIds ) {
 622                 // Finish incomplete moves
 623                 if ( !$this->copyOnly ) {
 624                         $this->finishIncompleteMoves( array( 'bt_text_id' => $textIds ) );
 625                         $this->syncDBs();
 626                 }
 627
 628                 $trx = new CgzCopyTransaction( $this, $this->orphanBlobClass );
 629
 630                 $res = wfGetDB( DB_SLAVE )->select(
 631                         array( 'text', 'blob_tracking' ),
 632                         array( 'old_id', 'old_text', 'old_flags' ),
 633                         array(
 634                                 'old_id' => $textIds,
 635                                 'bt_text_id=old_id',
 636                                 'bt_moved' => 0,
 637                         ),
 638                         __METHOD__,
 639                         array( 'DISTINCT' )
 640                 );
 641
 642                 foreach ( $res as $row ) {
 643                         $text = Revision::getRevisionText( $row );
 644                         if ( $text === false ) {
 645                                 $this->critical( "Error: cannot load revision text for old_id={$row->old_id}" );
 646                                 continue;
 647                         }
 648
 649                         if ( !$trx->addItem( $text, $row->old_id ) ) {
 650                                 $this->debug( "[orphan]: committing blob with " . $trx->getSize() . " rows" );
 651                                 $trx->commit();
 652                                 $trx = new CgzCopyTransaction( $this, $this->orphanBlobClass );
 653                                 $this->waitForSlaves();
 654                         }
 655                 }
 656                 $this->debug( "[orphan]: committing blob with " . $trx->getSize() . " rows" );
 657                 $trx->commit();
 658         }
 659
 660         /**
 661          * Wait for slaves (quietly)
 662          */
 663         function waitForSlaves() {
 664                 $lb = wfGetLB();
 665                 while ( true ) {
 666                         list( $host, $maxLag ) = $lb->getMaxLag();
 667                         if ( $maxLag < 2 ) {
 668                                 break;
 669                         }
 670                         sleep( 5 );
 671                 }
 672         }
 673 }
 674
 675 /**
 676  * Class to represent a recompression operation for a single CGZ blob
 677  */
 678 class CgzCopyTransaction {
 679         public $parent;
 680         public $blobClass;
 681         public $cgz;
 682         public $referrers;
 683
 684         /**
 685          * Create a transaction from a RecompressTracked object
 686          */
 687         function __construct( $parent, $blobClass ) {
 688                 $this->blobClass = $blobClass;
 689                 $this->cgz = false;
 690                 $this->texts = array();
 691                 $this->parent = $parent;
 692         }
 693
 694         /**
 695          * Add text.
 696          * Returns false if it's ready to commit.
 697          * @param $text string
 698          * @param $textId
 699          * @return bool
 700          */
 701         function addItem( $text, $textId ) {
 702                 if ( !$this->cgz ) {
 703                         $class = $this->blobClass;
 704                         $this->cgz = new $class;
 705                 }
 706                 $hash = $this->cgz->addItem( $text );
 707                 $this->referrers[$textId] = $hash;
 708                 $this->texts[$textId] = $text;
 709                 return $this->cgz->isHappy();
 710         }
 711
 712         function getSize() {
 713                 return count( $this->texts );
 714         }
 715
 716         /**
 717          * Recompress text after some aberrant modification
 718          */
 719         function recompress() {
 720                 $class = $this->blobClass;
 721                 $this->cgz = new $class;
 722                 $this->referrers = array();
 723                 foreach ( $this->texts as $textId => $text ) {
 724                         $hash = $this->cgz->addItem( $text );
 725                         $this->referrers[$textId] = $hash;
 726                 }
 727         }
 728
 729         /**
 730          * Commit the blob.
 731          * Does nothing if no text items have been added.
 732          * May skip the move if --copy-only is set.
 733          */
 734         function commit() {
 735                 $originalCount = count( $this->texts );
 736                 if ( !$originalCount ) {
 737                         return;
 738                 }
 739
 740                 // Check to see if the target text_ids have been moved already.
 741                 //
 742                 // We originally read from the slave, so this can happen when a single
 743                 // text_id is shared between multiple pages. It's rare, but possible
 744                 // if a delete/move/undelete cycle splits up a null edit.
 745                 //
 746                 // We do a locking read to prevent closer-run race conditions.
 747                 $dbw = wfGetDB( DB_MASTER );
 748                 $dbw->begin( __METHOD__ );
 749                 $res = $dbw->select( 'blob_tracking',
 750                         array( 'bt_text_id', 'bt_moved' ),
 751                         array( 'bt_text_id' => array_keys( $this->referrers ) ),
 752                         __METHOD__, array( 'FOR UPDATE' ) );
 753                 $dirty = false;
 754                 foreach ( $res as $row ) {
 755                         if ( $row->bt_moved ) {
 756                                 # This row has already been moved, remove it
 757                                 $this->parent->debug( "TRX: conflict detected in old_id={$row->bt_text_id}" );
 758                                 unset( $this->texts[$row->bt_text_id] );
 759                                 $dirty = true;
 760                         }
 761                 }
 762
 763                 // Recompress the blob if necessary
 764                 if ( $dirty ) {
 765                         if ( !count( $this->texts ) ) {
 766                                 // All have been moved already
 767                                 if ( $originalCount > 1 ) {
 768                                         // This is suspcious, make noise
 769                                         $this->critical( "Warning: concurrent operation detected, are there two conflicting " .
 770                                                 "processes running, doing the same job?" );
 771                                 }
 772                                 return;
 773                         }
 774                         $this->recompress();
 775                 }
 776
 777                 // Insert the data into the destination cluster
 778                 $targetCluster = $this->parent->getTargetCluster();
 779                 $store = $this->parent->store;
 780                 $targetDB = $store->getMaster( $targetCluster );
 781                 $targetDB->clearFlag( DBO_TRX ); // we manage the transactions
 782                 $targetDB->begin( __METHOD__ );
 783                 $baseUrl = $this->parent->store->store( $targetCluster, serialize( $this->cgz ) );
 784
 785                 // Write the new URLs to the blob_tracking table
 786                 foreach ( $this->referrers as $textId => $hash ) {
 787                         $url = $baseUrl . '/' . $hash;
 788                         $dbw->update( 'blob_tracking',
 789                                 array( 'bt_new_url' => $url ),
 790                                 array(
 791                                         'bt_text_id' => $textId,
 792                                         'bt_moved' => 0, # Check for concurrent conflicting update
 793                                 ),
 794                                 __METHOD__
 795                         );
 796                 }
 797
 798                 $targetDB->commit( __METHOD__ );
 799                 // Critical section here: interruption at this point causes blob duplication
 800                 // Reversing the order of the commits would cause data loss instead
 801                 $dbw->commit( __METHOD__ );
 802
 803                 // Write the new URLs to the text table and set the moved flag
 804                 if ( !$this->parent->copyOnly ) {
 805                         foreach ( $this->referrers as $textId => $hash ) {
 806                                 $url = $baseUrl . '/' . $hash;
 807                                 $this->parent->moveTextRow( $textId, $url );
 808                         }
 809                 }
 810         }
 811 }