moveToExternal.php

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<?php
use MediaWiki\MainConfigNames;
use MediaWiki\Maintenance\UndoLog;
use MediaWiki\Storage\SqlBlobStore;
use Wikimedia\AtEase\AtEase;
 
require_once __DIR__ . '/../Maintenance.php';
 
class MoveToExternal extends Maintenance {
    private $resolveStubs;
    private $reportingInterval;
    private $minID;
    private $maxID;
    private $esType;
    private $esLocation;
    private $threshold;
    private $gzip;
    private $skipResolve;
    private $legacyEncoding;
    private $dryRun;
    private $undoLog;
 
    public function __construct() {
        parent::__construct();
 
        $this->setBatchSize( 1000 );
 
        $this->addOption( 'start', 'start old_id', false, true, 's' );
        $this->addOption( 'end', 'end old_id', false, true, 'e' );
        $this->addOption( 'threshold', 'minimum size in bytes', false, true );
        $this->addOption( 'reporting-interval',
            'show a message after this many revisions', false, true );
        $this->addOption( 'undo', 'filename for undo SQL', false, true );
 
        $this->addOption( 'skip-gzip', 'Don\'t compress individual revisions' );
        $this->addOption( 'skip-resolve',
            'Don\'t replace HistoryBlobStub objects with direct external store pointers' );
        $this->addOption( 'iconv', 'Resolve legacy character encoding' );
        $this->addOption( 'dry-run', 'Don\'t modify any rows' );
 
        $this->addArg( 'type', 'The external store type, e.g. "DB" or "mwstore"' );
        $this->addArg( 'location', 'e.g. "cluster12" or "global-swift"' );
    }
 
    public function execute() {
        $this->resolveStubs = new ResolveStubs;
        $this->esType = $this->getArg( 0 ); // e.g. "DB" or "mwstore"
        $this->esLocation = $this->getArg( 1 ); // e.g. "cluster12" or "global-swift"
        $dbw = $this->getPrimaryDB();
 
        $maxID = $this->getOption( 'end' );
        if ( $maxID === null ) {
            $maxID = $dbw->newSelectQueryBuilder()
                ->select( 'MAX(old_id)' )
                ->from( 'text' )
                ->caller( __METHOD__ )->fetchField();
        }
        $this->maxID = (int)$maxID;
        $this->minID = (int)$this->getOption( 'start', 1 );
 
        $this->reportingInterval = $this->getOption( 'reporting-interval', 100 );
        $this->threshold = (int)$this->getOption( 'threshold', 0 );
 
        if ( $this->getOption( 'skip-gzip' ) ) {
            $this->gzip = false;
        } elseif ( !function_exists( 'gzdeflate' ) ) {
            $this->fatalError( "gzdeflate() not found. " .
                "Please run with --skip-gzip if you don't want to compress revisions." );
        } else {
            $this->gzip = true;
        }
 
        $this->skipResolve = $this->getOption( 'skip-resolve' );
 
        if ( $this->getOption( 'iconv' ) ) {
            $legacyEncoding = $this->getConfig()->get( MainConfigNames::LegacyEncoding );
            if ( $legacyEncoding ) {
                $this->legacyEncoding = $legacyEncoding;
            } else {
                $this->output( "iconv requested but the wiki has no legacy encoding\n" );
            }
        }
        $this->dryRun = $this->getOption( 'dry-run', false );
 
        $undo = $this->getOption( 'undo' );
        try {
            $this->undoLog = new UndoLog( $undo, $dbw );
        } catch ( RuntimeException $e ) {
            $this->fatalError( "Unable to open undo log" );
        }
        $this->resolveStubs->setUndoLog( $this->undoLog );
 
        return $this->doMoveToExternal();
    }
 
    private function doMoveToExternal() {
        $success = true;
        $dbr = $this->getReplicaDB();
 
        $count = $this->maxID - $this->minID + 1;
        $blockSize = $this->getBatchSize();
        $numBlocks = ceil( $count / $blockSize );
        print "Moving text rows from {$this->minID} to {$this->maxID} to external storage\n";
 
        $esFactory = $this->getServiceContainer()->getExternalStoreFactory();
        $extStore = $esFactory->getStore( $this->esType );
        $numMoved = 0;
        $stubIDs = [];
 
        for ( $block = 0; $block < $numBlocks; $block++ ) {
            $blockStart = $block * $blockSize + $this->minID;
            $blockEnd = $blockStart + $blockSize - 1;
 
            if ( $this->reportingInterval && !( $block % $this->reportingInterval ) ) {
                $this->output( "oldid=$blockStart, moved=$numMoved\n" );
                $this->waitForReplication();
            }
 
            $res = $dbr->newSelectQueryBuilder()
                ->select( [ 'old_id', 'old_flags', 'old_text' ] )
                ->from( 'text' )
                ->where( $this->getConditions( $blockStart, $blockEnd, $dbr ) )
                ->caller( __METHOD__ )->fetchResultSet();
            foreach ( $res as $row ) {
                $text = $row->old_text;
                $id = $row->old_id;
                $flags = SqlBlobStore::explodeFlags( $row->old_flags );
                [ $text, $flags ] = $this->resolveText( $text, $flags );
 
                if ( $text === false ) {
                    $success = false;
                }
 
                if ( in_array( 'error', $flags ) ) {
                    continue;
                } elseif ( in_array( 'object', $flags ) ) {
                    $obj = unserialize( $text );
                    if ( $obj instanceof HistoryBlobStub ) {
                        // Handle later, after CGZ resolution
                        if ( !$this->skipResolve ) {
                            $stubIDs[] = $id;
                        }
                        continue;
                    } elseif ( $obj instanceof HistoryBlobCurStub ) {
                        // Copy cur text to ES
                        $newText = $obj->getText();
                        if ( $newText === false ) {
                            print "Warning: Could not fetch revision blob {$id}: {$text}\n";
                            $success = false;
                            continue;
                        }
 
                        [ $text, $flags ] = $this->resolveLegacyEncoding( $newText, [] );
 
                        if ( $text === false ) {
                            print "Warning: Could not decode legacy-encoded gzip\'ed revision blob {$id}: {$newText}\n";
                            $success = false;
                            continue;
                        }
 
                        [ $text, $flags ] = $this->compress( $text, $flags );
                    } elseif ( $obj instanceof ConcatenatedGzipHistoryBlob ) {
                        // Store as is
                    } else {
                        $className = get_class( $obj );
                        print "Warning: old_id=$id unrecognised object class \"$className\"\n";
                        $success = false;
                        continue;
                    }
                } elseif ( strlen( $text ) < $this->threshold ) {
                    // Don't move small revisions
                    continue;
                } else {
                    [ $text, $flags ] = $this->resolveLegacyEncoding( $text, $flags );
                    [ $newText, $flags ] = $this->compress( $text, $flags );
                    if ( $newText === false ) {
                        print "Warning: Could not compress revision blob {$id}: {$text}\n";
                        $success = false;
                        continue;
                    }
                    $text = $newText;
                }
                $flags[] = 'external';
                $flagsString = implode( ',', $flags );
 
                if ( $this->dryRun ) {
                    $this->output( "Move $id => $flagsString " .
                        addcslashes( substr( $text, 0, 30 ), "\0..\x1f\x7f..\xff" ) .
                        "\n"
                    );
                    continue;
                }
 
                $url = $extStore->store( $this->esLocation, $text );
                if ( !$url ) {
                    $this->fatalError( "Error writing to external storage" );
                }
                $moved = $this->undoLog->update(
                    'text',
                    [ 'old_flags' => $flagsString, 'old_text' => $url ],
                    (array)$row,
                    __METHOD__
                );
                if ( $moved ) {
                    $numMoved++;
                } else {
                    print "Update of old_id $id failed, affected zero rows\n";
                    $success = false;
                }
            }
        }
 
        if ( count( $stubIDs ) ) {
            $this->resolveStubs( $stubIDs );
        }
 
        return $success;
    }
 
    private function compress( $text, $flags ) {
        if ( $this->gzip && !in_array( 'gzip', $flags ) ) {
            $flags[] = 'gzip';
            $text = gzdeflate( $text );
        }
        return [ $text, $flags ];
    }
 
    private function resolveLegacyEncoding( $text, $flags ) {
        if ( $this->legacyEncoding !== null
            && !in_array( 'utf-8', $flags )
            && !in_array( 'utf8', $flags )
        ) {
            // First decompress the entry so we don't try to convert a binary gzip to utf-8
            if ( in_array( 'gzip', $flags ) ) {
                if ( !$this->gzip ) {
                    return [ $text, $flags ];
                }
                $flags = array_diff( $flags, [ 'gzip' ] );
                $newText = gzinflate( $text );
                if ( $newText === false ) {
                    return [ false, $flags ];
                }
                $text = $newText;
            }
            AtEase::suppressWarnings();
            $newText = iconv( $this->legacyEncoding, 'UTF-8//IGNORE', $text );
            AtEase::restoreWarnings();
            if ( $newText === false ) {
                return [ false, $flags ];
            }
            $text = $newText;
            $flags[] = 'utf-8';
        }
        return [ $text, $flags ];
    }
 
    private function resolveStubs( $stubIDs ) {
        if ( $this->dryRun ) {
            print "Note: resolving stubs in dry run mode is expected to fail, " .
                "because the main blobs have not been moved to external storage.\n";
        }
 
        $dbr = $this->getReplicaDB();
        $this->output( "Resolving " . count( $stubIDs ) . " stubs\n" );
        $numResolved = 0;
        $numTotal = 0;
        foreach ( array_chunk( $stubIDs, $this->getBatchSize() ) as $stubBatch ) {
            $res = $dbr->newSelectQueryBuilder()
                ->select( [ 'old_id', 'old_flags', 'old_text' ] )
                ->from( 'text' )
                ->where( [ 'old_id' => $stubBatch ] )
                ->caller( __METHOD__ )->fetchResultSet();
            foreach ( $res as $row ) {
                $numResolved += $this->resolveStubs->resolveStub( $row, $this->dryRun ) ? 1 : 0;
                $numTotal++;
                if ( $this->reportingInterval
                    && $numTotal % $this->reportingInterval == 0
                ) {
                    $this->output( "$numTotal stubs processed\n" );
                    $this->waitForReplication();
                }
            }
        }
        $this->output( "$numResolved of $numTotal stubs resolved\n" );
    }
 
    protected function getConditions( $blockStart, $blockEnd, $dbr ) {
        return [
            "old_id BETWEEN $blockStart AND $blockEnd",
            'old_flags NOT ' . $dbr->buildLike( $dbr->anyString(), 'external', $dbr->anyString() ),
        ];
    }
 
    protected function resolveText( $text, $flags ) {
        return [ $text, $flags ];
    }
}
 
$maintClass = MoveToExternal::class;
require_once RUN_MAINTENANCE_IF_MAIN;