Disable WAL for block storage DB

(Rocks) DB WAL adds overheads while using the DB for saving checkpoints
for block storage. Avoiding writing to WAL translates the write workload
(appending blocks to the blockfile) into a sequential disk writes.

This commit changes the way checkpoints are saved - checkpoints are
written to DB as before, however since WAL is disabled, the checkpoint
stays in-memory only. The in-memory checkpoint is flushed explicitly to
disk (via DB flush) at the time of new block file creation. The in-memory
checkpoint would implicitly also be flushed to memory at the time of DB
shutdown. However, if a crash takes place, the checkpoint available in the
DB would be behind the actual block file status. In order to handle this
crash scenario, this commit also adds code to perform a scan of the block
file beyond the last saved checkpoint and update the checkpoint.

Change-Id: Ie88646b225abaa50b595833f5e7ed8d4facae920
Signed-off-by: manish <[email protected]>

Author: manish-sethi

core/ledgernext/blkstorage/fsblkstorage/blockfile_mgr.go

@@ -64,11 +64,12 @@ func newBlockfileMgr(conf *Conf) *blockfileMgr {
 	}
 	if cpInfo == nil {
 		cpInfo = &checkpointInfo{latestFileChunkSuffixNum: 0, latestFileChunksize: 0}
-		err = mgr.saveCurrentInfo(cpInfo)
+		err = mgr.saveCurrentInfo(cpInfo, true)
 		if err != nil {
 			panic(fmt.Sprintf("Could not save next block file info to db: %s", err))
 		}
 	}
+	updateCPInfo(conf, cpInfo)
 	currentFileWriter, err := newBlockfileWriter(deriveBlockfilePath(rootDir, cpInfo.latestFileChunkSuffixNum))
 	if err != nil {
 		panic(fmt.Sprintf("Could not open writer to current file: %s", err))
@@ -81,9 +82,12 @@ func newBlockfileMgr(conf *Conf) *blockfileMgr {
 	mgr.index = newBlockIndex(db)
 	mgr.cpInfo = cpInfo
 	mgr.currentFileWriter = currentFileWriter
-
 	// init BlockchainInfo
-	bcInfo := &protos.BlockchainInfo{Height: 0, CurrentBlockHash: nil, PreviousBlockHash: nil}
+	bcInfo := &protos.BlockchainInfo{
+		Height:            0,
+		CurrentBlockHash:  nil,
+		PreviousBlockHash: nil}
+
 	if cpInfo.lastBlockNumber > 0 {
 		lastBlock, err := mgr.retrieveSerBlockByNumber(cpInfo.lastBlockNumber)
 		if err != nil {
@@ -104,11 +108,37 @@ func newBlockfileMgr(conf *Conf) *blockfileMgr {
 }
 
 func initDB(conf *Conf) *db.DB {
-	dbInst := db.CreateDB(&db.Conf{DBPath: conf.dbPath, CFNames: []string{blockIndexCF}})
+	dbInst := db.CreateDB(&db.Conf{
+		DBPath:     conf.dbPath,
+		CFNames:    []string{blockIndexCF},
+		DisableWAL: true})
+
 	dbInst.Open()
 	return dbInst
 }
 
+func updateCPInfo(conf *Conf, cpInfo *checkpointInfo) {
+	logger.Debugf("Starting checkpoint=%s", cpInfo)
+	rootDir := conf.blockfilesDir
+	filePath := deriveBlockfilePath(rootDir, cpInfo.latestFileChunkSuffixNum)
+	exists, size, err := util.FileExists(filePath)
+	if err != nil {
+		panic(fmt.Sprintf("Error in checking whether file [%s] exists: %s", filePath, err))
+	}
+	logger.Debugf("status of file [%s]: exists=[%t], size=[%d]", filePath, exists, size)
+	if !exists || int(size) == cpInfo.latestFileChunksize {
+		// check point info is in sync with the file on disk
+		return
+	}
+	endOffsetLastBlock, numBlocks, err := scanForLastCompleteBlock(filePath, int64(cpInfo.latestFileChunksize))
+	if err != nil {
+		panic(fmt.Sprintf("Could not open current file for detecting last block in the file: %s", err))
+	}
+	cpInfo.lastBlockNumber += uint64(numBlocks)
+	cpInfo.latestFileChunksize = int(endOffsetLastBlock)
+	logger.Debugf("Checkpoint after updates by scanning the last file segment:%s", cpInfo)
+}
+
 func deriveBlockfilePath(rootDir string, suffixNum int) string {
 	return rootDir + "/" + blockfilePrefix + fmt.Sprintf("%06d", suffixNum)
 }
@@ -123,13 +153,18 @@ func (mgr *blockfileMgr) close() {
 }
 
 func (mgr *blockfileMgr) moveToNextFile() {
-	nextFileInfo := &checkpointInfo{latestFileChunkSuffixNum: mgr.cpInfo.latestFileChunkSuffixNum + 1, latestFileChunksize: 0}
-	nextFileWriter, err := newBlockfileWriter(deriveBlockfilePath(mgr.rootDir, nextFileInfo.latestFileChunkSuffixNum))
+	nextFileInfo := &checkpointInfo{
+		latestFileChunkSuffixNum: mgr.cpInfo.latestFileChunkSuffixNum + 1,
+		latestFileChunksize:      0}
+
+	nextFileWriter, err := newBlockfileWriter(
+		deriveBlockfilePath(mgr.rootDir, nextFileInfo.latestFileChunkSuffixNum))
+
 	if err != nil {
 		panic(fmt.Sprintf("Could not open writer to next file: %s", err))
 	}
 	mgr.currentFileWriter.close()
-	err = mgr.saveCurrentInfo(nextFileInfo)
+	err = mgr.saveCurrentInfo(nextFileInfo, true)
 	if err != nil {
 		panic(fmt.Sprintf("Could not save next block file info to db: %s", err))
 	}
@@ -145,49 +180,44 @@ func (mgr *blockfileMgr) addBlock(block *protos.Block2) error {
 	blockBytes := serBlock.GetBytes()
 	blockHash := serBlock.ComputeHash()
 	txOffsets, err := serBlock.GetTxOffsets()
+	currentOffset := mgr.cpInfo.latestFileChunksize
 	if err != nil {
 		return fmt.Errorf("Error while serializing block: %s", err)
 	}
-	currentOffset := mgr.cpInfo.latestFileChunksize
-	length := len(blockBytes)
-	encodedLen := proto.EncodeVarint(uint64(length))
-	totalLen := length + len(encodedLen)
-	if currentOffset+totalLen > mgr.conf.maxBlockfileSize {
+	blockBytesLen := len(blockBytes)
+	blockBytesEncodedLen := proto.EncodeVarint(uint64(blockBytesLen))
+	totalBytesToAppend := blockBytesLen + len(blockBytesEncodedLen)
+
+	if currentOffset+totalBytesToAppend > mgr.conf.maxBlockfileSize {
 		mgr.moveToNextFile()
 		currentOffset = 0
 	}
-	err = mgr.currentFileWriter.append(encodedLen)
-	if err != nil {
-		err1 := mgr.currentFileWriter.truncateFile(mgr.cpInfo.latestFileChunksize)
-		if err1 != nil {
-			panic(fmt.Sprintf("Could not truncate current file to known size after an error while appending a block: %s", err))
-		}
-		return fmt.Errorf("Error while appending block to file: %s", err)
+	err = mgr.currentFileWriter.append(blockBytesEncodedLen, false)
+	if err == nil {
+		err = mgr.currentFileWriter.append(blockBytes, true)
 	}
-
-	err = mgr.currentFileWriter.append(blockBytes)
 	if err != nil {
-		err1 := mgr.currentFileWriter.truncateFile(mgr.cpInfo.latestFileChunksize)
-		if err1 != nil {
-			panic(fmt.Sprintf("Could not truncate current file to known size after an error while appending a block: %s", err))
+		truncateErr := mgr.currentFileWriter.truncateFile(mgr.cpInfo.latestFileChunksize)
+		if truncateErr != nil {
+			panic(fmt.Sprintf("Could not truncate current file to known size after an error during block append: %s", err))
 		}
 		return fmt.Errorf("Error while appending block to file: %s", err)
 	}
 
-	mgr.cpInfo.latestFileChunksize += totalLen
+	mgr.cpInfo.latestFileChunksize += totalBytesToAppend
 	mgr.cpInfo.lastBlockNumber++
-	err = mgr.saveCurrentInfo(mgr.cpInfo)
+	err = mgr.saveCurrentInfo(mgr.cpInfo, false)
 	if err != nil {
-		mgr.cpInfo.latestFileChunksize -= totalLen
-		err1 := mgr.currentFileWriter.truncateFile(mgr.cpInfo.latestFileChunksize)
-		if err1 != nil {
-			panic(fmt.Sprintf("Could not truncate current file to known size after an error while appending a block: %s", err))
+		mgr.cpInfo.latestFileChunksize -= totalBytesToAppend
+		truncateErr := mgr.currentFileWriter.truncateFile(mgr.cpInfo.latestFileChunksize)
+		if truncateErr != nil {
+			panic(fmt.Sprintf("Error in truncating current file to known size after an error in saving checkpoint info: %s", err))
 		}
 		return fmt.Errorf("Error while saving current file info to db: %s", err)
 	}
 	blockFLP := &fileLocPointer{fileSuffixNum: mgr.cpInfo.latestFileChunkSuffixNum}
 	blockFLP.offset = currentOffset
-	mgr.index.indexBlock(mgr.cpInfo.lastBlockNumber, blockHash, blockFLP, length, len(encodedLen), txOffsets)
+	mgr.index.indexBlock(mgr.cpInfo.lastBlockNumber, blockHash, blockFLP, blockBytesLen, len(blockBytesEncodedLen), txOffsets)
 	mgr.updateBlockchainInfo(blockHash, block)
 	return nil
 }
@@ -198,7 +228,11 @@ func (mgr *blockfileMgr) getBlockchainInfo() *protos.BlockchainInfo {
 
 func (mgr *blockfileMgr) updateBlockchainInfo(latestBlockHash []byte, latestBlock *protos.Block2) {
 	currentBCInfo := mgr.getBlockchainInfo()
-	newBCInfo := &protos.BlockchainInfo{Height: currentBCInfo.Height + 1, CurrentBlockHash: latestBlockHash, PreviousBlockHash: latestBlock.PreviousBlockHash}
+	newBCInfo := &protos.BlockchainInfo{
+		Height:            currentBCInfo.Height + 1,
+		CurrentBlockHash:  latestBlockHash,
+		PreviousBlockHash: latestBlock.PreviousBlockHash}
+
 	mgr.bcInfo.Store(newBCInfo)
 }
 
@@ -315,33 +349,59 @@ func (mgr *blockfileMgr) fetchRawBytes(lp *fileLocPointer) ([]byte, error) {
 }
 
 func (mgr *blockfileMgr) loadCurrentInfo() (*checkpointInfo, error) {
-	b, err := mgr.db.Get(mgr.defaultCF, blkMgrInfoKey)
-	if err != nil {
-		return nil, err
-	}
-	if b == nil {
+	var b []byte
+	var err error
+	if b, err = mgr.db.Get(mgr.defaultCF, blkMgrInfoKey); b == nil || err != nil {
 		return nil, err
 	}
 	i := &checkpointInfo{}
 	if err = i.unmarshal(b); err != nil {
 		return nil, err
 	}
+	logger.Debugf("loaded checkpointInfo:%s", i)
 	return i, nil
 }
 
-func (mgr *blockfileMgr) saveCurrentInfo(i *checkpointInfo) error {
+func (mgr *blockfileMgr) saveCurrentInfo(i *checkpointInfo, flush bool) error {
 	b, err := i.marshal()
 	if err != nil {
 		return err
 	}
-	err = mgr.db.Put(mgr.defaultCF, blkMgrInfoKey, b)
-	if err != nil {
+	if err = mgr.db.Put(mgr.defaultCF, blkMgrInfoKey, b); err != nil {
 		return err
 	}
+	if flush {
+		if err = mgr.db.Flush(true); err != nil {
+			return err
+		}
+		logger.Debugf("saved checkpointInfo:%s", i)
+	}
 	return nil
 }
 
-// blkMgrInfo
+func scanForLastCompleteBlock(filePath string, startingOffset int64) (int64, int, error) {
+	logger.Debugf("scanForLastCompleteBlock(): filePath=[%s], startingOffset=[%d]", filePath, startingOffset)
+	numBlocks := 0
+	blockStream, err := newBlockStream(filePath, startingOffset)
+	if err != nil {
+		return 0, 0, err
+	}
+	defer blockStream.close()
+	for {
+		blockBytes, err := blockStream.nextBlockBytes()
+		if blockBytes == nil || err != nil {
+			logger.Debugf(`scanForLastCompleteBlock(): error=[%s].
+			This may happen if a crash has happened during block appending.
+			Returning current offset as a last complete block's end offset`, err)
+			break
+		}
+		numBlocks++
+	}
+	logger.Debugf("scanForLastCompleteBlock(): last complete block ends at offset=[%d]", blockStream.currentFileOffset)
+	return blockStream.currentFileOffset, numBlocks, err
+}
+
+// checkpointInfo
 type checkpointInfo struct {
 	latestFileChunkSuffixNum int
 	latestFileChunksize      int
@@ -385,3 +445,8 @@ func (i *checkpointInfo) unmarshal(b []byte) error {
 
 	return nil
 }
+
+func (i *checkpointInfo) String() string {
+	return fmt.Sprintf("latestFileChunkSuffixNum=[%d], latestFileChunksize=[%d], lastBlockNumber=[%d]",
+		i.latestFileChunkSuffixNum, i.latestFileChunksize, i.lastBlockNumber)
+}

core/ledgernext/blkstorage/fsblkstorage/blockfile_mgr_test.go

@@ -36,23 +36,83 @@ func TestBlockfileMgrBlockReadWrite(t *testing.T) {
 	blkfileMgrWrapper.testGetBlockByNumber(blocks, 1)
 }
 
+func TestBlockfileMgrCrashDuringWriting(t *testing.T) {
+	testBlockfileMgrCrashDuringWriting(t, 10, 2, 1000, 10)
+	testBlockfileMgrCrashDuringWriting(t, 10, 2, 1000, 1)
+	testBlockfileMgrCrashDuringWriting(t, 10, 2, 1000, 0)
+	testBlockfileMgrCrashDuringWriting(t, 0, 0, 1000, 10)
+}
+
+func testBlockfileMgrCrashDuringWriting(t *testing.T, numBlocksBeforeCheckpoint int,
+	numBlocksAfterCheckpoint int, numLastBlockBytes int, numPartialBytesToWrite int) {
+	env := newTestEnv(t)
+	defer env.Cleanup()
+	blkfileMgrWrapper := newTestBlockfileWrapper(t, env)
+	blocksBeforeCP := testutil.ConstructTestBlocks(t, numBlocksBeforeCheckpoint)
+	blkfileMgrWrapper.addBlocks(blocksBeforeCP)
+	currentCPInfo := blkfileMgrWrapper.blockfileMgr.cpInfo
+	cpInfo1 := &checkpointInfo{
+		currentCPInfo.latestFileChunkSuffixNum,
+		currentCPInfo.latestFileChunksize,
+		currentCPInfo.lastBlockNumber}
+
+	blocksAfterCP := testutil.ConstructTestBlocks(t, numBlocksAfterCheckpoint)
+	blkfileMgrWrapper.addBlocks(blocksAfterCP)
+	cpInfo2 := blkfileMgrWrapper.blockfileMgr.cpInfo
+
+	// simulate a crash scenario
+	lastBlockBytes := []byte{}
+	encodedLen := proto.EncodeVarint(uint64(numLastBlockBytes))
+	randomBytes := testutil.ConstructRandomBytes(t, numLastBlockBytes)
+	lastBlockBytes = append(lastBlockBytes, encodedLen...)
+	lastBlockBytes = append(lastBlockBytes, randomBytes...)
+	partialBytes := lastBlockBytes[:numPartialBytesToWrite]
+	blkfileMgrWrapper.blockfileMgr.currentFileWriter.append(partialBytes, true)
+	blkfileMgrWrapper.blockfileMgr.saveCurrentInfo(cpInfo1, true)
+	blkfileMgrWrapper.close()
+
+	// simulate a start after a crash
+	blkfileMgrWrapper = newTestBlockfileWrapper(t, env)
+	defer blkfileMgrWrapper.close()
+	cpInfo3 := blkfileMgrWrapper.blockfileMgr.cpInfo
+	testutil.AssertEquals(t, cpInfo3, cpInfo2)
+
+	// add fresh blocks after restart
+	numBlocksAfterRestart := 2
+	blocksAfterRestart := testutil.ConstructTestBlocks(t, numBlocksAfterRestart)
+	blkfileMgrWrapper.addBlocks(blocksAfterRestart)
+
+	// itrerate for all blocks
+	allBlocks := []*protos.Block2{}
+	allBlocks = append(allBlocks, blocksBeforeCP...)
+	allBlocks = append(allBlocks, blocksAfterCP...)
+	allBlocks = append(allBlocks, blocksAfterRestart...)
+	numTotalBlocks := len(allBlocks)
+	testBlockfileMgrBlockIterator(t, blkfileMgrWrapper.blockfileMgr, 1, numTotalBlocks, allBlocks)
+}
+
 func TestBlockfileMgrBlockIterator(t *testing.T) {
 	env := newTestEnv(t)
 	defer env.Cleanup()
 	blkfileMgrWrapper := newTestBlockfileWrapper(t, env)
 	defer blkfileMgrWrapper.close()
 	blocks := testutil.ConstructTestBlocks(t, 10)
 	blkfileMgrWrapper.addBlocks(blocks)
-	itr, err := blkfileMgrWrapper.blockfileMgr.retrieveBlocks(1, 8)
+	testBlockfileMgrBlockIterator(t, blkfileMgrWrapper.blockfileMgr, 1, 8, blocks[0:8])
+}
+
+func testBlockfileMgrBlockIterator(t *testing.T, blockfileMgr *blockfileMgr,
+	firstBlockNum int, lastBlockNum int, expectedBlocks []*protos.Block2) {
+	itr, err := blockfileMgr.retrieveBlocks(uint64(firstBlockNum), uint64(lastBlockNum))
 	defer itr.Close()
 	testutil.AssertNoError(t, err, "Error while getting blocks iterator")
 	numBlocksItrated := 0
 	for ; itr.Next(); numBlocksItrated++ {
 		block, err := itr.Get()
 		testutil.AssertNoError(t, err, fmt.Sprintf("Error while getting block number [%d] from iterator", numBlocksItrated))
-		testutil.AssertEquals(t, block.(*BlockHolder).GetBlock(), blocks[numBlocksItrated])
+		testutil.AssertEquals(t, block.(*BlockHolder).GetBlock(), expectedBlocks[numBlocksItrated])
 	}
-	testutil.AssertEquals(t, numBlocksItrated, 8)
+	testutil.AssertEquals(t, numBlocksItrated, lastBlockNum-firstBlockNum+1)
 }
 
 func TestBlockfileMgrBlockchainInfo(t *testing.T) {

core/ledgernext/blkstorage/fsblkstorage/blockfile_rw.go

@@ -47,12 +47,14 @@ func (w *blockfileWriter) truncateFile(targetSize int) error {
 	return nil
 }
 
-func (w *blockfileWriter) append(b []byte) error {
+func (w *blockfileWriter) append(b []byte, sync bool) error {
 	_, err := w.file.Write(b)
 	if err != nil {
 		return err
 	}
-	w.file.Sync()
+	if sync {
+		return w.file.Sync()
+	}
 	return nil
 }
 
@@ -97,8 +99,9 @@ func (r *blockfileReader) close() error {
 }
 
 type blockStream struct {
-	file   *os.File
-	reader *bufio.Reader
+	file              *os.File
+	reader            *bufio.Reader
+	currentFileOffset int64
 }
 
 func newBlockStream(filePath string, offset int64) (*blockStream, error) {
@@ -115,7 +118,7 @@ func newBlockStream(filePath string, offset int64) (*blockStream, error) {
 	if newPosition != offset {
 		panic(fmt.Sprintf("Could not seek file [%s] to given offset [%d]. New position = [%d]", filePath, offset, newPosition))
 	}
-	s := &blockStream{file, bufio.NewReader(file)}
+	s := &blockStream{file, bufio.NewReader(file), offset}
 	return s, nil
 }
 
@@ -133,6 +136,7 @@ func (s *blockStream) nextBlockBytes() ([]byte, error) {
 	if _, err = io.ReadAtLeast(s.reader, blockBytes, int(len)); err != nil {
 		return nil, err
 	}
+	s.currentFileOffset += int64(n) + int64(len)
 	return blockBytes, nil
 }