9ede6ae83e
This bumps the major version of the database module to v3. This is needed because the current code already has backwards incompatible changes.
119 lines
4.4 KiB
Go
119 lines
4.4 KiB
Go
// Copyright (c) 2015-2016 The btcsuite developers
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// Copyright (c) 2016-2020 The Decred developers
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// Use of this source code is governed by an ISC
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// license that can be found in the LICENSE file.
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package ffldb
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import (
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"fmt"
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"hash/crc32"
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"github.com/decred/dcrd/database/v3"
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)
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// The serialized write cursor location format is:
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//
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// [0:4] Block file (4 bytes)
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// [4:8] File offset (4 bytes)
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// [8:12] Castagnoli CRC-32 checksum (4 bytes)
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// serializeWriteRow serialize the current block file and offset where new
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// will be written into a format suitable for storage into the metadata.
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func serializeWriteRow(curBlockFileNum, curFileOffset uint32) []byte {
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var serializedRow [12]byte
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byteOrder.PutUint32(serializedRow[0:4], curBlockFileNum)
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byteOrder.PutUint32(serializedRow[4:8], curFileOffset)
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checksum := crc32.Checksum(serializedRow[:8], castagnoli)
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byteOrder.PutUint32(serializedRow[8:12], checksum)
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return serializedRow[:]
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}
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// deserializeWriteRow deserializes the write cursor location stored in the
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// metadata. Returns ErrCorruption if the checksum of the entry doesn't match.
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func deserializeWriteRow(writeRow []byte) (uint32, uint32, error) {
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// Ensure the checksum matches. The checksum is at the end.
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gotChecksum := crc32.Checksum(writeRow[:8], castagnoli)
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wantChecksumBytes := writeRow[8:12]
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wantChecksum := byteOrder.Uint32(wantChecksumBytes)
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if gotChecksum != wantChecksum {
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str := fmt.Sprintf("metadata for write cursor does not match "+
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"the expected checksum - got %d, want %d", gotChecksum,
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wantChecksum)
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return 0, 0, makeDbErr(database.ErrCorruption, str)
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}
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fileNum := byteOrder.Uint32(writeRow[0:4])
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fileOffset := byteOrder.Uint32(writeRow[4:8])
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return fileNum, fileOffset, nil
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}
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// reconcileDB reconciles the metadata with the flat block files on disk. It
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// will also initialize the underlying database if the create flag is set.
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func reconcileDB(pdb *db, create bool) (database.DB, error) {
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// Perform initial internal bucket and value creation during database
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// creation.
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if create {
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if err := initDB(pdb.cache.ldb); err != nil {
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return nil, err
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}
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}
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// Load the current write cursor position from the metadata.
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var curFileNum, curOffset uint32
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err := pdb.View(func(tx database.Tx) error {
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writeRow := tx.Metadata().Get(writeLocKeyName)
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if writeRow == nil {
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str := "write cursor does not exist"
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return makeDbErr(database.ErrCorruption, str)
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}
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var err error
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curFileNum, curOffset, err = deserializeWriteRow(writeRow)
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return err
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})
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if err != nil {
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return nil, err
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}
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// When the write cursor position found by scanning the block files on
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// disk is AFTER the position the metadata believes to be true, truncate
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// the files on disk to match the metadata. This can be a fairly common
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// occurrence in unclean shutdown scenarios while the block files are in
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// the middle of being written. Since the metadata isn't updated until
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// after the block data is written, this is effectively just a rollback
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// to the known good point before the unclean shutdown.
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wc := pdb.store.writeCursor
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if wc.curFileNum > curFileNum || (wc.curFileNum == curFileNum &&
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wc.curOffset > curOffset) {
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log.Info("Detected unclean shutdown - Repairing...")
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log.Debugf("Metadata claims file %d, offset %d. Block data is "+
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"at file %d, offset %d", curFileNum, curOffset,
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wc.curFileNum, wc.curOffset)
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pdb.store.handleRollback(curFileNum, curOffset)
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log.Infof("Database sync complete")
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}
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// When the write cursor position found by scanning the block files on
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// disk is BEFORE the position the metadata believes to be true, return
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// a corruption error. Since sync is called after each block is written
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// and before the metadata is updated, this should only happen in the
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// case of missing, deleted, or truncated block files, which generally
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// is not an easily recoverable scenario. In the future, it might be
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// possible to rescan and rebuild the metadata from the block files,
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// however, that would need to happen with coordination from a higher
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// layer since it could invalidate other metadata.
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if wc.curFileNum < curFileNum || (wc.curFileNum == curFileNum &&
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wc.curOffset < curOffset) {
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str := fmt.Sprintf("metadata claims file %d, offset %d, but "+
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"block data is at file %d, offset %d", curFileNum,
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curOffset, wc.curFileNum, wc.curOffset)
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log.Warnf("***Database corruption detected***: %v", str)
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return nil, makeDbErr(database.ErrCorruption, str)
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}
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return pdb, nil
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}
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