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