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