checkStorage.php

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<?php
use MediaWiki\MediaWikiServices;
use MediaWiki\Shell\Shell;

if ( !defined( 'MEDIAWIKI' ) ) {
    $optionsWithoutArgs = [ 'fix' ];
    require_once __DIR__ . '/../commandLine.inc';

    $cs = new CheckStorage;
    $fix = isset( $options['fix'] );
    $xml = $args[0] ?? false;
    $cs->check( $fix, $xml );
}

// ----------------------------------------------------------------------------------

class CheckStorage {
    const CONCAT_HEADER = 'O:27:"concatenatedgziphistoryblob"';
    public $oldIdMap, $errors;
    public $dbStore = null;

    public $errorDescriptions = [
        'restore text' => 'Damaged text, need to be restored from a backup',
        'restore revision' => 'Damaged revision row, need to be restored from a backup',
        'unfixable' => 'Unexpected errors with no automated fixing method',
        'fixed' => 'Errors already fixed',
        'fixable' => 'Errors which would already be fixed if --fix was specified',
    ];

    function check( $fix = false, $xml = '' ) {
        $dbr = wfGetDB( DB_REPLICA );
        if ( $fix ) {
            print "Checking, will fix errors if possible...\n";
        } else {
            print "Checking...\n";
        }
        $maxRevId = $dbr->selectField( 'revision', 'MAX(rev_id)', '', __METHOD__ );
        $chunkSize = 1000;
        $flagStats = [];
        $objectStats = [];
        $knownFlags = [ 'external', 'gzip', 'object', 'utf-8' ];
        $this->errors = [
            'restore text' => [],
            'restore revision' => [],
            'unfixable' => [],
            'fixed' => [],
            'fixable' => [],
        ];

        for ( $chunkStart = 1; $chunkStart < $maxRevId; $chunkStart += $chunkSize ) {
            $chunkEnd = $chunkStart + $chunkSize - 1;
            // print "$chunkStart of $maxRevId\n";

            // Fetch revision rows
            $this->oldIdMap = [];
            $dbr->ping();
            $res = $dbr->select( 'revision', [ 'rev_id', 'rev_text_id' ],
                [ "rev_id BETWEEN $chunkStart AND $chunkEnd" ], __METHOD__ );
            foreach ( $res as $row ) {
                $this->oldIdMap[$row->rev_id] = $row->rev_text_id;
            }

            if ( !count( $this->oldIdMap ) ) {
                continue;
            }

            // Fetch old_flags
            $missingTextRows = array_flip( $this->oldIdMap );
            $externalRevs = [];
            $objectRevs = [];
            $res = $dbr->select(
                'text',
                [ 'old_id', 'old_flags' ],
                [ 'old_id' => $this->oldIdMap ],
                __METHOD__
            );
            foreach ( $res as $row ) {
                $flags = $row->old_flags;
                $id = $row->old_id;

                // Create flagStats row if it doesn't exist
                $flagStats = $flagStats + [ $flags => 0 ];
                // Increment counter
                $flagStats[$flags]++;

                // Not missing
                unset( $missingTextRows[$row->old_id] );

                // Check for external or object
                if ( $flags == '' ) {
                    $flagArray = [];
                } else {
                    $flagArray = explode( ',', $flags );
                }
                if ( in_array( 'external', $flagArray ) ) {
                    $externalRevs[] = $id;
                } elseif ( in_array( 'object', $flagArray ) ) {
                    $objectRevs[] = $id;
                }

                // Check for unrecognised flags
                if ( $flags == '0' ) {
                    // This is a known bug from 2004
                    // It's safe to just erase the old_flags field
                    if ( $fix ) {
                        $this->addError( 'fixed', "Warning: old_flags set to 0", $id );
                        $dbw = wfGetDB( DB_MASTER );
                        $dbw->ping();
                        $dbw->update( 'text', [ 'old_flags' => '' ],
                            [ 'old_id' => $id ], __METHOD__ );
                        echo "Fixed\n";
                    } else {
                        $this->addError( 'fixable', "Warning: old_flags set to 0", $id );
                    }
                } elseif ( count( array_diff( $flagArray, $knownFlags ) ) ) {
                    $this->addError( 'unfixable', "Error: invalid flags field \"$flags\"", $id );
                }
            }

            // Output errors for any missing text rows
            foreach ( $missingTextRows as $oldId => $revId ) {
                $this->addError( 'restore revision', "Error: missing text row", $oldId );
            }

            // Verify external revisions
            $externalConcatBlobs = [];
            $externalNormalBlobs = [];
            if ( count( $externalRevs ) ) {
                $res = $dbr->select(
                    'text',
                    [ 'old_id', 'old_flags', 'old_text' ],
                    [ 'old_id' => $externalRevs ],
                    __METHOD__
                );
                foreach ( $res as $row ) {
                    $urlParts = explode( '://', $row->old_text, 2 );
                    if ( count( $urlParts ) !== 2 || $urlParts[1] == '' ) {
                        $this->addError( 'restore text', "Error: invalid URL \"{$row->old_text}\"", $row->old_id );
                        continue;
                    }
                    list( $proto, ) = $urlParts;
                    if ( $proto != 'DB' ) {
                        $this->addError(
                            'restore text',
                            "Error: invalid external protocol \"$proto\"",
                            $row->old_id );
                        continue;
                    }
                    $path = explode( '/', $row->old_text );
                    $cluster = $path[2];
                    $id = $path[3];
                    if ( isset( $path[4] ) ) {
                        $externalConcatBlobs[$cluster][$id][] = $row->old_id;
                    } else {
                        $externalNormalBlobs[$cluster][$id][] = $row->old_id;
                    }
                }
            }

            // Check external concat blobs for the right header
            $this->checkExternalConcatBlobs( $externalConcatBlobs );

            // Check external normal blobs for existence
            if ( count( $externalNormalBlobs ) ) {
                if ( is_null( $this->dbStore ) ) {
                    $this->dbStore = new ExternalStoreDB;
                }
                foreach ( $externalConcatBlobs as $cluster => $xBlobIds ) {
                    $blobIds = array_keys( $xBlobIds );
                    $extDb =& $this->dbStore->getSlave( $cluster );
                    $blobsTable = $this->dbStore->getTable( $extDb );
                    $res = $extDb->select( $blobsTable,
                        [ 'blob_id' ],
                        [ 'blob_id' => $blobIds ],
                        __METHOD__
                    );
                    foreach ( $res as $row ) {
                        unset( $xBlobIds[$row->blob_id] );
                    }
                    // Print errors for missing blobs rows
                    foreach ( $xBlobIds as $blobId => $oldId ) {
                        $this->addError(
                            'restore text',
                            "Error: missing target $blobId for one-part ES URL",
                            $oldId );
                    }
                }
            }

            // Check local objects
            $dbr->ping();
            $concatBlobs = [];
            $curIds = [];
            if ( count( $objectRevs ) ) {
                $headerLength = 300;
                $res = $dbr->select(
                    'text',
                    [ 'old_id', 'old_flags', "LEFT(old_text, $headerLength) AS header" ],
                    [ 'old_id' => $objectRevs ],
                    __METHOD__
                );
                foreach ( $res as $row ) {
                    $oldId = $row->old_id;
                    $matches = [];
                    if ( !preg_match( '/^O:(\d+):"(\w+)"/', $row->header, $matches ) ) {
                        $this->addError( 'restore text', "Error: invalid object header", $oldId );
                        continue;
                    }

                    $className = strtolower( $matches[2] );
                    if ( strlen( $className ) != $matches[1] ) {
                        $this->addError(
                            'restore text',
                            "Error: invalid object header, wrong class name length",
                            $oldId
                        );
                        continue;
                    }

                    $objectStats = $objectStats + [ $className => 0 ];
                    $objectStats[$className]++;

                    switch ( $className ) {
                        case 'concatenatedgziphistoryblob':
                            // Good
                            break;
                        case 'historyblobstub':
                        case 'historyblobcurstub':
                            if ( strlen( $row->header ) == $headerLength ) {
                                $this->addError( 'unfixable', "Error: overlong stub header", $oldId );
                                break;
                            }
                            $stubObj = unserialize( $row->header );
                            if ( !is_object( $stubObj ) ) {
                                $this->addError( 'restore text', "Error: unable to unserialize stub object", $oldId );
                                break;
                            }
                            if ( $className == 'historyblobstub' ) {
                                $concatBlobs[$stubObj->mOldId][] = $oldId;
                            } else {
                                $curIds[$stubObj->mCurId][] = $oldId;
                            }
                            break;
                        default:
                            $this->addError( 'unfixable', "Error: unrecognised object class \"$className\"", $oldId );
                    }
                }
            }

            // Check local concat blob validity
            $externalConcatBlobs = [];
            if ( count( $concatBlobs ) ) {
                $headerLength = 300;
                $res = $dbr->select(
                    'text',
                    [ 'old_id', 'old_flags', "LEFT(old_text, $headerLength) AS header" ],
                    [ 'old_id' => array_keys( $concatBlobs ) ],
                    __METHOD__
                );
                foreach ( $res as $row ) {
                    $flags = explode( ',', $row->old_flags );
                    if ( in_array( 'external', $flags ) ) {
                        // Concat blob is in external storage?
                        if ( in_array( 'object', $flags ) ) {
                            $urlParts = explode( '/', $row->header );
                            if ( $urlParts[0] != 'DB:' ) {
                                $this->addError(
                                    'unfixable',
                                    "Error: unrecognised external storage type \"{$urlParts[0]}",
                                    $row->old_id
                                );
                            } else {
                                $cluster = $urlParts[2];
                                $id = $urlParts[3];
                                if ( !isset( $externalConcatBlobs[$cluster][$id] ) ) {
                                    $externalConcatBlobs[$cluster][$id] = [];
                                }
                                $externalConcatBlobs[$cluster][$id] = array_merge(
                                    $externalConcatBlobs[$cluster][$id], $concatBlobs[$row->old_id]
                                );
                            }
                        } else {
                            $this->addError(
                                'unfixable',
                                "Error: invalid flags \"{$row->old_flags}\" on concat bulk row {$row->old_id}",
                                $concatBlobs[$row->old_id] );
                        }
                    } elseif ( strcasecmp(
                        substr( $row->header, 0, strlen( self::CONCAT_HEADER ) ),
                        self::CONCAT_HEADER
                    ) ) {
                        $this->addError(
                            'restore text',
                            "Error: Incorrect object header for concat bulk row {$row->old_id}",
                            $concatBlobs[$row->old_id]
                        );
                    } # else good

                    unset( $concatBlobs[$row->old_id] );
                }
            }

            // Check targets of unresolved stubs
            $this->checkExternalConcatBlobs( $externalConcatBlobs );
            // next chunk
        }

        print "\n\nErrors:\n";
        foreach ( $this->errors as $name => $errors ) {
            if ( count( $errors ) ) {
                $description = $this->errorDescriptions[$name];
                echo "$description: " . implode( ',', array_keys( $errors ) ) . "\n";
            }
        }

        if ( count( $this->errors['restore text'] ) && $fix ) {
            if ( (string)$xml !== '' ) {
                $this->restoreText( array_keys( $this->errors['restore text'] ), $xml );
            } else {
                echo "Can't fix text, no XML backup specified\n";
            }
        }

        print "\nFlag statistics:\n";
        $total = array_sum( $flagStats );
        foreach ( $flagStats as $flag => $count ) {
            printf( "%-30s %10d %5.2f%%\n", $flag, $count, $count / $total * 100 );
        }
        print "\nLocal object statistics:\n";
        $total = array_sum( $objectStats );
        foreach ( $objectStats as $className => $count ) {
            printf( "%-30s %10d %5.2f%%\n", $className, $count, $count / $total * 100 );
        }
    }

    function addError( $type, $msg, $ids ) {
        if ( is_array( $ids ) && count( $ids ) == 1 ) {
            $ids = reset( $ids );
        }
        if ( is_array( $ids ) ) {
            $revIds = [];
            foreach ( $ids as $id ) {
                $revIds = array_merge( $revIds, array_keys( $this->oldIdMap, $id ) );
            }
            print "$msg in text rows " . implode( ', ', $ids ) .
                ", revisions " . implode( ', ', $revIds ) . "\n";
        } else {
            $id = $ids;
            $revIds = array_keys( $this->oldIdMap, $id );
            if ( count( $revIds ) == 1 ) {
                print "$msg in old_id $id, rev_id {$revIds[0]}\n";
            } else {
                print "$msg in old_id $id, revisions " . implode( ', ', $revIds ) . "\n";
            }
        }
        $this->errors[$type] = $this->errors[$type] + array_flip( $revIds );
    }

    function checkExternalConcatBlobs( $externalConcatBlobs ) {
        if ( !count( $externalConcatBlobs ) ) {
            return;
        }

        if ( is_null( $this->dbStore ) ) {
            $this->dbStore = new ExternalStoreDB;
        }

        foreach ( $externalConcatBlobs as $cluster => $oldIds ) {
            $blobIds = array_keys( $oldIds );
            $extDb =& $this->dbStore->getSlave( $cluster );
            $blobsTable = $this->dbStore->getTable( $extDb );
            $headerLength = strlen( self::CONCAT_HEADER );
            $res = $extDb->select( $blobsTable,
                [ 'blob_id', "LEFT(blob_text, $headerLength) AS header" ],
                [ 'blob_id' => $blobIds ],
                __METHOD__
            );
            foreach ( $res as $row ) {
                if ( strcasecmp( $row->header, self::CONCAT_HEADER ) ) {
                    $this->addError(
                        'restore text',
                        "Error: invalid header on target $cluster/{$row->blob_id} of two-part ES URL",
                        $oldIds[$row->blob_id]
                    );
                }
                unset( $oldIds[$row->blob_id] );
            }

            // Print errors for missing blobs rows
            foreach ( $oldIds as $blobId => $oldIds2 ) {
                $this->addError(
                    'restore text',
                    "Error: missing target $cluster/$blobId for two-part ES URL",
                    $oldIds2
                );
            }
        }
    }

    function restoreText( $revIds, $xml ) {
        global $wgDBname;
        $tmpDir = wfTempDir();

        if ( !count( $revIds ) ) {
            return;
        }

        print "Restoring text from XML backup...\n";

        $revFileName = "$tmpDir/broken-revlist-$wgDBname";
        $filteredXmlFileName = "$tmpDir/filtered-$wgDBname.xml";

        // Write revision list
        if ( !file_put_contents( $revFileName, implode( "\n", $revIds ) ) ) {
            echo "Error writing revision list, can't restore text\n";

            return;
        }

        // Run mwdumper
        echo "Filtering XML dump...\n";
        $exitStatus = 0;
        passthru( 'mwdumper ' .
            Shell::escape(
                "--output=file:$filteredXmlFileName",
                "--filter=revlist:$revFileName",
                $xml
            ), $exitStatus
        );

        if ( $exitStatus ) {
            echo "mwdumper died with exit status $exitStatus\n";

            return;
        }

        $file = fopen( $filteredXmlFileName, 'r' );
        if ( !$file ) {
            echo "Unable to open filtered XML file\n";

            return;
        }

        $dbr = wfGetDB( DB_REPLICA );
        $dbw = wfGetDB( DB_MASTER );
        $dbr->ping();
        $dbw->ping();

        $source = new ImportStreamSource( $file );
        $importer = new WikiImporter(
            $source,
            MediaWikiServices::getInstance()->getMainConfig()
        );
        $importer->setRevisionCallback( [ $this, 'importRevision' ] );
        $importer->setNoticeCallback( function ( $msg, $params ) {
            echo wfMessage( $msg, $params )->text() . "\n";
        } );
        $importer->doImport();
    }

    function importRevision( &$revision, &$importer ) {
        $id = $revision->getID();
        $content = $revision->getContent( Revision::RAW );
        $id = $id ?: '';

        if ( $content === null ) {
            echo "Revision $id is broken, we have no content available\n";

            return;
        }

        $text = $content->serialize();
        if ( $text === '' ) {
            // This is what happens if the revision was broken at the time the
            // dump was made. Unfortunately, it also happens if the revision was
            // legitimately blank, so there's no way to tell the difference. To
            // be safe, we'll skip it and leave it broken

            echo "Revision $id is blank in the dump, may have been broken before export\n";

            return;
        }

        if ( !$id ) {
            // No ID, can't import
            echo "No id tag in revision, can't import\n";

            return;
        }

        // Find text row again
        $dbr = wfGetDB( DB_REPLICA );
        $oldId = $dbr->selectField( 'revision', 'rev_text_id', [ 'rev_id' => $id ], __METHOD__ );
        if ( !$oldId ) {
            echo "Missing revision row for rev_id $id\n";

            return;
        }

        // Compress the text
        $flags = Revision::compressRevisionText( $text );

        // Update the text row
        $dbw = wfGetDB( DB_MASTER );
        $dbw->update( 'text',
            [ 'old_flags' => $flags, 'old_text' => $text ],
            [ 'old_id' => $oldId ],
            __METHOD__, [ 'LIMIT' => 1 ]
        );

        // Remove it from the unfixed list and add it to the fixed list
        unset( $this->errors['restore text'][$id] );
        $this->errors['fixed'][$id] = true;
    }
}