区块链教程Fabric1.0源代码分析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

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