Hyperledger-Fabric源码分析（底层存储-BlockStore）
这里将fabric存储部分最重要的blockstore剖析下，看下是怎样的实现能托管账本数据。
blockfileMgr
首先BlockStore对外的能力输出需要blockfileMgr来托管，看下它新建做些什么？
新建
func newBlockfileMgr(id string, conf *Conf, indexConfig *blkstorage.IndexConfig, indexStore *leveldbhelper.DBHandle) *blockfileMgr {
logger.Debugf("newBlockfileMgr() initializing file-based block storage for ledger: %s ", id)
//Determine the root directory for the blockfile storage, if it does not exist create it
rootDir := conf.getLedgerBlockDir(id)
_, err := util.CreateDirIfMissing(rootDir)
if err != nil {
panic(fmt.Sprintf("Error creating block storage root dir [%s]: %s", rootDir, err))
}
// Instantiate the manager, i.e. blockFileMgr structure
mgr := &blockfileMgr{rootDir: rootDir, conf: conf, db: indexStore}
// cp = checkpointInfo, retrieve from the database the file suffix or number of where blocks were stored.
// It also retrieves the current size of that file and the last block number that was written to that file.
// At init checkpointInfo:latestFileChunkSuffixNum=[0], latestFileChunksize=[0], lastBlockNumber=[0]
cpInfo, err := mgr.loadCurrentInfo()
if err != nil {
panic(fmt.Sprintf("Could not get block file info for current block file from db: %s", err))
}
if cpInfo == nil {
logger.Info(`Getting block information from block storage`)
if cpInfo, err = constructCheckpointInfoFromBlockFiles(rootDir); err != nil {
panic(fmt.Sprintf("Could not build checkpoint info from block files: %s", err))
}
logger.Debugf("Info constructed by scanning the blocks dir = %s", spew.Sdump(cpInfo))
} else {
logger.Debug(`Synching block information from block storage (if needed)`)
syncCPInfoFromFS(rootDir, cpInfo)
}
err = mgr.saveCurrentInfo(cpInfo, true)
if err != nil {
panic(fmt.Sprintf("Could not save next block file info to db: %s", err))
}
//Open a writer to the file identified by the number and truncate it to only contain the latest block
// that was completely saved (file system, index, cpinfo, etc)
currentFileWriter, err := newBlockfileWriter(deriveBlockfilePath(rootDir, cpInfo.latestFileChunkSuffixNum))
if err != nil {
panic(fmt.Sprintf("Could not open writer to current file: %s", err))
}
//Truncate the file to remove excess past last block
err = currentFileWriter.truncateFile(cpInfo.latestFileChunksize)
if err != nil {
panic(fmt.Sprintf("Could not truncate current file to known size in db: %s", err))
}
// Create a new KeyValue store database handler for the blocks index in the keyvalue database
if mgr.index, err = newBlockIndex(indexConfig, indexStore); err != nil {
panic(fmt.Sprintf("error in block index: %s", err))
}
// Update the manager with the checkpoint info and the file writer
mgr.cpInfo = cpInfo
mgr.currentFileWriter = currentFileWriter
// Create a checkpoint condition (event) variable, for the goroutine waiting for
// or announcing the occurrence of an event.
mgr.cpInfoCond = sync.NewCond(&sync.Mutex{})
// init BlockchainInfo for external API's
bcInfo := &common.BlockchainInfo{
Height: 0,
CurrentBlockHash: nil,
PreviousBlockHash: nil}
if !cpInfo.isChainEmpty {
//If start up is a restart of an existing storage, sync the index from block storage and update BlockchainInfo for external API's
mgr.syncIndex()
lastBlockHeader, err := mgr.retrieveBlockHeaderByNumber(cpInfo.lastBlockNumber)
if err != nil {
panic(fmt.Sprintf("Could not retrieve header of the last block form file: %s", err))
}
lastBlockHash := lastBlockHeader.Hash()
previousBlockHash := lastBlockHeader.PreviousHash
bcInfo = &common.BlockchainInfo{
Height: cpInfo.lastBlockNumber + 1,
CurrentBlockHash: lastBlockHash,
PreviousBlockHash: previousBlockHash}
}
mgr.bcInfo.Store(bcInfo)
return mgr
}
这里主要做几件事情
- 组装checkpoint，要不从账本文件中抽取，要不从db中拿到，要不就重新创建，如上，主要是记录block在底层存储文件中的位置。
- 组装blockchaininfo, 主要是记录前一个和当前block的hash，以及整个blockchain的高度。
- 新建writer，指定紧接着最新block后面的位置开始写入
- 将block按照各个维度，生成index，写入db
type checkpointInfo struct { latestFileChunkSuffixNum int 最新block所在的文件num latestFileChunksize int 下一个block在文件的起始位置 isChainEmpty bool 是否是空账本 lastBlockNumber uint64 最新的blocknum }
addBlock
func (mgr *blockfileMgr) addBlock(block *common.Block) error {
bcInfo := mgr.getBlockchainInfo()
if block.Header.Number != bcInfo.Height {
return errors.Errorf(
"block number should have been %d but was %d",
mgr.getBlockchainInfo().Height, block.Header.Number,
)
}
// Add the previous hash check - Though, not essential but may not be a bad idea to
// verify the field `block.Header.PreviousHash` present in the block.
// This check is a simple bytes comparison and hence does not cause any observable performance penalty
// and may help in detecting a rare scenario if there is any bug in the ordering service.
if !bytes.Equal(block.Header.PreviousHash, bcInfo.CurrentBlockHash) {
return errors.Errorf(
"unexpected Previous block hash. Expected PreviousHash = [%x], PreviousHash referred in the latest block= [%x]",
bcInfo.CurrentBlockHash, block.Header.PreviousHash,
)
}
blockBytes, info, err := serializeBlock(block)
if err != nil {
return errors.WithMessage(err, "error serializing block")
}
blockHash := block.Header.Hash()
//Get the location / offset where each transaction starts in the block and where the block ends
txOffsets := info.txOffsets
currentOffset := mgr.cpInfo.latestFileChunksize
blockBytesLen := len(blockBytes)
blockBytesEncodedLen := proto.EncodeVarint(uint64(blockBytesLen))
totalBytesToAppend := blockBytesLen + len(blockBytesEncodedLen)
//Determine if we need to start a new file since the size of this block
//exceeds the amount of space left in the current file
if currentOffset+totalBytesToAppend > mgr.conf.maxBlockfileSize {
mgr.moveToNextFile()
currentOffset = 0
}
//append blockBytesEncodedLen to the file
err = mgr.currentFileWriter.append(blockBytesEncodedLen, false)
if err == nil {
//append the actual block bytes to the file
err = mgr.currentFileWriter.append(blockBytes, true)
}
if err != nil {
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 errors.WithMessage(err, "error appending block to file")
}
//Update the checkpoint info with the results of adding the new block
currentCPInfo := mgr.cpInfo
newCPInfo := &checkpointInfo{
latestFileChunkSuffixNum: currentCPInfo.latestFileChunkSuffixNum,
latestFileChunksize: currentCPInfo.latestFileChunksize + totalBytesToAppend,
isChainEmpty: false,
lastBlockNumber: block.Header.Number}
//save the checkpoint information in the database
if err = mgr.saveCurrentInfo(newCPInfo, false); err != nil {
truncateErr := mgr.currentFileWriter.truncateFile(currentCPInfo.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 errors.WithMessage(err, "error saving current file info to db")
}
//Index block file location pointer updated with file suffex and offset for the new block
blockFLP := &fileLocPointer{fileSuffixNum: newCPInfo.latestFileChunkSuffixNum}
blockFLP.offset = currentOffset
// shift the txoffset because we prepend length of bytes before block bytes
for _, txOffset := range txOffsets {
txOffset.loc.offset += len(blockBytesEncodedLen)
}
//save the index in the database
if err = mgr.index.indexBlock(&blockIdxInfo{
blockNum: block.Header.Number, blockHash: blockHash,
flp: blockFLP, txOffsets: txOffsets, metadata: block.Metadata}); err != nil {
return err
}
//update the checkpoint info (for storage) and the blockchain info (for APIs) in the manager
mgr.updateCheckpoint(newCPInfo)
mgr.updateBlockchainInfo(blockHash, block)
return nil
}
这不，马上就用到了blockchaininfo。一上来就是两个判断，其实就是要保证block前后都必须连续。
这里又用到checkpointinfo，拿到最后那个文件我写到哪了。
计算该block的大小加当前文件的offset是否超过了单个文件size，换句话说就是最后那个block文件能不能放得下，放不下，就顺延到下个文件，从头开始。这里需要注意的是moveToNextFile这里会去更新checkpoint为下个文件的0位置。
又用到writer了，接下来正式将block写进去，过程中如果报错，那事情就大了，回滚掉这次写入。如果没有问题，更新checkpoint。这个东西实在重要，没它根本玩不转。甚至于block写成功了，cp如果没有成功入库，连block都要回滚掉。
更新block里面每个tx的offset，txOffset.loc.offset += len(blockBytesEncodedLen)，这里的技巧是txoffset写入的时候是相对blockbytes的位置, 而对应到blockfile的话就不一样，每个block是blocklen+blockbytes组成，txoffset的位置当然也要偏移blocklen才正确
新进来了block，索引当然也要做必要的更新，blockchaininfo也是，checkpointInfo很怪这里又更新一遍，记得么，前面写入文件后不是已经入库了么。
func (mgr *blockfileMgr) updateCheckpoint(cpInfo *checkpointInfo) { mgr.cpInfoCond.L.Lock() defer mgr.cpInfoCond.L.Unlock() mgr.cpInfo = cpInfo logger.Debugf("Broadcasting about update checkpointInfo: %s", cpInfo) mgr.cpInfoCond.Broadcast() } func (itr *blocksItr) waitForBlock(blockNum uint64) uint64 { itr.mgr.cpInfoCond.L.Lock() defer itr.mgr.cpInfoCond.L.Unlock() for itr.mgr.cpInfo.lastBlockNumber < blockNum && !itr.shouldClose() { logger.Debugf("Going to wait for newer blocks. maxAvailaBlockNumber=[%d], waitForBlockNum=[%d]", itr.mgr.cpInfo.lastBlockNumber, blockNum) itr.mgr.cpInfoCond.Wait() logger.Debugf("Came out of wait. maxAvailaBlockNumber=[%d]", itr.mgr.cpInfo.lastBlockNumber) } return itr.mgr.cpInfo.lastBlockNumber }
- 其实就是去唤醒所以等待block的地方，通知他们你们要的block到了，你们可以继续干活了。
镇楼图
仅供参考，生成自1.0
block-structure.png
