Fabric 1.0源代码笔记 之 Ledger #historydb（历史数据库）

1、historydb概述

historydb，用于存储所有块读写集中写集的内容。
代码分布在core/ledger/kvledger/history/historydb目录下，目录结构如下：

• historydb.go，定义核心接口HistoryDBProvider和HistoryDB。
• histmgr_helper.go，historydb工具函数。
• historyleveldb目录，historydb基于leveldb的实现。
  • historyleveldb.go，HistoryDBProvider和HistoryDB接口实现，即historyleveldb.HistoryDBProvider和historyleveldb.historyDB结构体及方法。
  • historyleveldb_query_executer.go，定义LevelHistoryDBQueryExecutor和historyScanner结构体及方法。

2、核心接口定义

HistoryDBProvider接口定义：

type HistoryDBProvider interface {
    GetDBHandle(id string) (HistoryDB, error) //获取HistoryDB
    Close() //关闭所有HistoryDB
}
//代码在core/ledger/kvledger/history/historydb/historydb.go

HistoryDB接口定义：

type HistoryDB interface {
    //构造 LevelHistoryDBQueryExecutor
    NewHistoryQueryExecutor(blockStore blkstorage.BlockStore) (ledger.HistoryQueryExecutor, error)
    //提交Block入historyDB
    Commit(block *common.Block) error
    //获取savePointKey，即version.Height
    GetLastSavepoint() (*version.Height, error)
    //是否应该恢复，比较lastAvailableBlock和Savepoint
    ShouldRecover(lastAvailableBlock uint64) (bool, uint64, error)
    //提交丢失的块
    CommitLostBlock(block *common.Block) error
}
//代码在core/ledger/kvledger/history/historydb/historydb.go

补充ledger.HistoryQueryExecutor接口定义：执行历史记录查询。

type HistoryQueryExecutor interface {
    GetHistoryForKey(namespace string, key string) (commonledger.ResultsIterator, error) //按key查历史记录
}
//代码在core/ledger/ledger_interface.go

3、historydb工具函数

//构造复合HistoryKey，ns 0x00 key 0x00 blocknum trannum
func ConstructCompositeHistoryKey(ns string, key string, blocknum uint64, trannum uint64) []byte
//构造部分复合HistoryKey，ns 0x00 key 0x00 0xff
func ConstructPartialCompositeHistoryKey(ns string, key string, endkey bool) []byte 
//按分隔符separator，分割bytesToSplit
func SplitCompositeHistoryKey(bytesToSplit []byte, separator []byte) ([]byte, []byte) 
//代码在core/ledger/kvledger/history/historydb/histmgr_helper.go

4、HistoryDB接口实现

HistoryDB接口实现，即historyleveldb.historyDB结构体及方法。historyDB结构体定义如下：

type historyDB struct {
    db     *leveldbhelper.DBHandle //leveldb
    dbName string //dbName
}
//代码在core/ledger/kvledger/history/historydb/historyleveldb/historyleveldb.go

涉及方法如下：

//构造historyDB
func newHistoryDB(db *leveldbhelper.DBHandle, dbName string) *historyDB
//do nothing
func (historyDB *historyDB) Open() error
//do nothing
func (historyDB *historyDB) Close()
//提交Block入historyDB，将读写集中写集入库，并更新savePointKey
func (historyDB *historyDB) Commit(block *common.Block) error
//构造 LevelHistoryDBQueryExecutor
func (historyDB *historyDB) NewHistoryQueryExecutor(blockStore blkstorage.BlockStore) (ledger.HistoryQueryExecutor, error)
获取savePointKey，即version.Height
func (historyDB *historyDB) GetLastSavepoint() (*version.Height, error)
//是否应该恢复，比较lastAvailableBlock和Savepoint
func (historyDB *historyDB) ShouldRecover(lastAvailableBlock uint64) (bool, uint64, error)
//提交丢失的块，即调用historyDB.Commit(block)
func (historyDB *historyDB) CommitLostBlock(block *common.Block) error
//代码在core/ledger/kvledger/history/historydb/historyleveldb/historyleveldb.go

func (historyDB *historyDB) Commit(block *common.Block) error代码如下：

blockNo := block.Header.Number //区块编号
var tranNo uint64 //交易编号，初始化值为0
dbBatch := leveldbhelper.NewUpdateBatch() //leveldb批量更新

//交易验证代码，type TxValidationFlags []uint8
//交易筛选器
txsFilter := util.TxValidationFlags(block.Metadata.Metadata[common.BlockMetadataIndex_TRANSACTIONS_FILTER])
if len(txsFilter) == 0 {
    txsFilter = util.NewTxValidationFlags(len(block.Data.Data))
    block.Metadata.Metadata[common.BlockMetadataIndex_TRANSACTIONS_FILTER] = txsFilter
}
for _, envBytes := range block.Data.Data {
    if txsFilter.IsInvalid(int(tranNo)) { //检查指定的交易是否有效
        tranNo++
        continue
    }
    //[]byte反序列化为Envelope
    env, err := putils.GetEnvelopeFromBlock(envBytes)
    payload, err := putils.GetPayload(env) //e.Payload反序列化为Payload
    //[]byte反序列化为ChannelHeader
    chdr, err := putils.UnmarshalChannelHeader(payload.Header.ChannelHeader)

    if common.HeaderType(chdr.Type) == common.HeaderType_ENDORSER_TRANSACTION { //背书交易，type HeaderType int32
        respPayload, err := putils.GetActionFromEnvelope(envBytes) //获取ChaincodeAction
        txRWSet := &rwsetutil.TxRwSet{}
        err = txRWSet.FromProtoBytes(respPayload.Results) //[]byte反序列化后构造NsRwSet，加入txRWSet.NsRwSets
        for _, nsRWSet := range txRWSet.NsRwSets {
            ns := nsRWSet.NameSpace
            for _, kvWrite := range nsRWSet.KvRwSet.Writes {
                writeKey := kvWrite.Key
                //txRWSet中写集入库
                compositeHistoryKey := historydb.ConstructCompositeHistoryKey(ns, writeKey, blockNo, tranNo)
                dbBatch.Put(compositeHistoryKey, emptyValue)
            }
        }
    } else {
        logger.Debugf("Skipping transaction [%d] since it is not an endorsement transaction\n", tranNo)
    }
    tranNo++
}

height := version.NewHeight(blockNo, tranNo)
dbBatch.Put(savePointKey, height.ToBytes())
err := historyDB.db.WriteBatch(dbBatch, true)
//代码在core/ledger/kvledger/history/historydb/historyleveldb/historyleveldb.go

Tx（Transaction 交易）相关更详细内容，参考：Fabric 1.0源代码笔记 之 Tx（Transaction 交易）

5、HistoryDBProvider接口实现

HistoryDBProvider接口实现，即historyleveldb.HistoryDBProvider结构体和方法。

type HistoryDBProvider struct {
    dbProvider *leveldbhelper.Provider
}

//构造HistoryDBProvider
func NewHistoryDBProvider() *HistoryDBProvider
//获取HistoryDB
func (provider *HistoryDBProvider) GetDBHandle(dbName string) (historydb.HistoryDB, error)
//关闭所有HistoryDB句柄，调取provider.dbProvider.Close()
func (provider *HistoryDBProvider) Close()
//代码在core/ledger/kvledger/history/historydb/historyleveldb/historyleveldb.go

6、LevelHistoryDBQueryExecutor和historyScanner结构体及方法

LevelHistoryDBQueryExecutor结构体及方法：实现ledger.HistoryQueryExecutor接口。

type LevelHistoryDBQueryExecutor struct {
    historyDB  *historyDB
    blockStore blkstorage.BlockStore //用于传递给historyScanner
}
//按key查historyDB，调用q.historyDB.db.GetIterator(compositeStartKey, compositeEndKey)
func (q *LevelHistoryDBQueryExecutor) GetHistoryForKey(namespace string, key string) (commonledger.ResultsIterator, error) 
//代码在core/ledger/kvledger/history/historydb/historyleveldb/historyleveldb_query_executer.go

historyScanner结构体及方法：实现ledger.ResultsIterator接口。

type historyScanner struct {
    compositePartialKey []byte //ns 0x00 key 0x00
    namespace           string
    key                 string
    dbItr               iterator.Iterator //leveldb迭代器
    blockStore          blkstorage.BlockStore
}

//构造historyScanner
func newHistoryScanner(compositePartialKey []byte, namespace string, key string, dbItr iterator.Iterator, blockStore blkstorage.BlockStore) *historyScanner
//按迭代器中key取blockNum和tranNum，再按blockNum和tranNum从blockStore中取Envelope，然后从Envelope的txRWSet.NsRwSets中按key查找并构造queryresult.KeyModification
func (scanner *historyScanner) Next() (commonledger.QueryResult, error)
func (scanner *historyScanner) Close() //scanner.dbItr.Release()
从Envelope的txRWSet.NsRwSets中按key查找并构造queryresult.KeyModification
func getKeyModificationFromTran(tranEnvelope *common.Envelope, namespace string, key string) (commonledger.QueryResult, error)
//代码在core/ledger/kvledger/history/historydb/historyleveldb/historyleveldb_query_executer.go

补充queryresult.KeyModification：

type KeyModification struct {
    TxId      string //交易ID，ChannelHeader.TxId
    Value     []byte //读写集中Value，KVWrite.Value
    Timestamp *google_protobuf.Timestamp //ChannelHeader.Timestamp
    IsDelete  bool //KVWrite.IsDelete
}
//代码在protos/ledger/queryresult/kv_query_result.pb.go