Fabric 1.0源代码笔记 之 Orderer #ledger(Orderer Ledger)

1、Orderer Ledger概述

Orderer Ledger代码分布在orderer/ledger目录下,目录结构如下:

  • orderer/ledger目录:
         ledger.go,Factory、Iterator、Reader、Writer、ReadWriter等接口定义。
        
    util.go,Orderer Ledger工具函数,及NotFoundErrorIterator结构体定义。
         file目录,file类型ledger实现。
        
    json目录,json类型ledger实现。
        * ram目录,内存类型ledger实现。
        

    2、接口定义

Factory接口定义:

type Factory interface {
    //按chainID获取已存在的ledger,如不存在则创建
    GetOrCreate(chainID string) (ReadWriter, error)
    //获取ChainID列表
    ChainIDs() []string
    //关闭并释放所有资源
    Close()
}
//代码在orderer/ledger/ledger.go

ReadWriter接口定义:

type Reader interface {
    //按起始块号获取迭代器
    Iterator(startType *ab.SeekPosition) (Iterator, uint64)
    //获取ledger高度(即块数)
    Height() uint64
}

type Writer interface {
    //ledger向追加新块
    Append(block *cb.Block) error
}

type ReadWriter interface {
    Reader //嵌入Reader
    Writer //嵌入Writer
}

type Iterator interface {
    //获取下一个可用的块
    Next() (*cb.Block, cb.Status)
    //获取可用的通道
    ReadyChan() <-chan struct{}
}
//代码在orderer/ledger/ledger.go

3、file类型ledger实现

3.1、fileLedgerFactory结构体及方法(实现Factory接口)

type fileLedgerFactory struct {
    blkstorageProvider blkstorage.BlockStoreProvider //blkstorage
    ledgers            map[string]ledger.ReadWriter //多链
    mutex              sync.Mutex
}

//从ledgers中查找,如找到则返回,否则创建Ledger(即blkstorage)并构造fileLedger
func (flf *fileLedgerFactory) GetOrCreate(chainID string) (ledger.ReadWriter, error)
//获取已存在的Ledger列表,调取flf.blkstorageProvider.List()
func (flf *fileLedgerFactory) ChainIDs() []string
//关闭并释放资源flf.blkstorageProvider.Close()
func (flf *fileLedgerFactory) Close()
//构造fileLedgerFactory
func New(directory string) ledger.Factory
//代码在orderer/ledger/file/factory.go

blkstorage更详细内容,可参考:Fabric 1.0源代码笔记 之 Ledger #blkstorage(block文件存储)

3.2、fileLedger结构体及方法(实现ReadWriter接口)

type fileLedger struct {
    blockStore blkstorage.BlockStore //blkstorage
    signal     chan struct{}
}

//按起始块号获取迭代器
func (fl *fileLedger) Iterator(startPosition *ab.SeekPosition) (ledger.Iterator, uint64)
//获取ledger高度(即块数)
func (fl *fileLedger) Height() uint64
//ledger向追加新块
func (fl *fileLedger) Append(block *cb.Block) error
//代码在orderer/ledger/file/impl.go

3.3、fileLedgerIterator结构体及方法(实现Iterator接口)

type fileLedgerIterator struct {
    ledger      *fileLedger
    blockNumber uint64 //当前已迭代的块号
}
//获取下一个可用的块,如果没有可用的块则阻止
func (i *fileLedgerIterator) Next() (*cb.Block, cb.Status)
//获取可用的通道,如果块不可用返回signal,否则返回closedChan
func (i *fileLedgerIterator) ReadyChan() <-chan struct{}
//代码在orderer/ledger/file/impl.go

4、Orderer Ledger工具函数

//创建块
func CreateNextBlock(rl Reader, messages []*cb.Envelope) *cb.Block
func GetBlock(rl Reader, index uint64) *cb.Block
//地址在orderer/ledger/util.go

func CreateNextBlock(rl Reader, messages []cb.Envelope) cb.Block代码如下:

func CreateNextBlock(rl Reader, messages []*cb.Envelope) *cb.Block {
    var nextBlockNumber uint64
    var previousBlockHash []byte

    if rl.Height() > 0 {
        it, _ := rl.Iterator(&ab.SeekPosition{
            Type: &ab.SeekPosition_Newest{
                &ab.SeekNewest{},
            },
        })
        <-it.ReadyChan()
        block, status := it.Next() //获取前一个最新的块
        nextBlockNumber = block.Header.Number + 1
        previousBlockHash = block.Header.Hash() //前一个最新的块的哈希
    }

    data := &cb.BlockData{
        Data: make([][]byte, len(messages)),
    }

    var err error
    for i, msg := range messages {
        data.Data[i], err = proto.Marshal(msg) //逐一填充数据
    }

    block := cb.NewBlock(nextBlockNumber, previousBlockHash)
    block.Header.DataHash = data.Hash()
    block.Data = data

    return block
}
//地址在orderer/ledger/util.go