区块链教程Fabric1.0源代码分析Peer（Endorser服务端），2018年下半年，区块链行业正逐渐褪去发展之初的浮躁、回归理性，表面上看相关人才需求与身价似乎正在回落。但事实上，正是初期泡沫的渐退，让人们更多的关注点放在了区块链真正的技术之上。

Fabric 1.0源代码笔记 之 Peer #EndorserServer（Endorser服务端）

1、EndorserServer概述

EndorserServer相关代码在protos/peer、core/endorser目录下。

• protos/peer/peer.pb.go，EndorserServer接口定义。
• core/endorser/endorser.go，EndorserServer接口实现，即Endorser结构体及方法，以及Endorser服务端ProcessProposal处理流程。

2、EndorserServer接口定义

2.1、EndorserServer接口定义

type EndorserServer interface {
    ProcessProposal(context.Context, *SignedProposal) (*ProposalResponse, error)
}
//代码在protos/peer/peer.pb.go

2.2、gRPC相关实现

var _Endorser_serviceDesc = grpc.ServiceDesc{
    ServiceName: "protos.Endorser",
    HandlerType: (*EndorserServer)(nil),
    Methods: []grpc.MethodDesc{
        {
            MethodName: "ProcessProposal",
            Handler:    _Endorser_ProcessProposal_Handler,
        },
    },
    Streams:  []grpc.StreamDesc{},
    Metadata: "peer/peer.proto",
}

func RegisterEndorserServer(s *grpc.Server, srv EndorserServer) {
    s.RegisterService(&_Endorser_serviceDesc, srv)
}

func _Endorser_ProcessProposal_Handler(srv interface{}, ctx context.Context, dec func(interface{}) error, interceptor grpc.UnaryServerInterceptor) (interface{}, error) {
    in := new(SignedProposal)
    if err := dec(in); err != nil {
        return nil, err
    }
    if interceptor == nil {
        return srv.(EndorserServer).ProcessProposal(ctx, in)
    }
    info := &grpc.UnaryServerInfo{
        Server:     srv,
        FullMethod: "/protos.Endorser/ProcessProposal",
    }
    handler := func(ctx context.Context, req interface{}) (interface{}, error) {
        return srv.(EndorserServer).ProcessProposal(ctx, req.(*SignedProposal))
    }
    return interceptor(ctx, in, info, handler)
}
//代码在protos/peer/peer.pb.go

3、EndorserServer接口实现

3.1、Endorser结构体及方法

type Endorser struct {
    policyChecker policy.PolicyChecker //策略检查器
}
//代码在core/endorser/endorser.go

涉及方法如下：

//构造Endorser
func NewEndorserServer() pb.EndorserServer
//执行提案
func (e *Endorser) ProcessProposal(ctx context.Context, signedProp *pb.SignedProposal) (*pb.ProposalResponse, error)

//检查SignedProposal是否符合通道策略，调用e.policyChecker.CheckPolicy()
func (e *Endorser) checkACL(signedProp *pb.SignedProposal, chdr *common.ChannelHeader, shdr *common.SignatureHeader, hdrext *pb.ChaincodeHeaderExtension) error
//检查Escc和Vscc，暂未实现
func (*Endorser) checkEsccAndVscc(prop *pb.Proposal) error
//获取账本的交易模拟器，调用peer.GetLedger(ledgername).NewTxSimulator()
func (*Endorser) getTxSimulator(ledgername string) (ledger.TxSimulator, error)
//获取账本历史交易查询器，调用peer.GetLedger(ledgername).NewHistoryQueryExecutor()
func (*Endorser) getHistoryQueryExecutor(ledgername string) (ledger.HistoryQueryExecutor, error)
//执行链码
func (e *Endorser) callChaincode(ctxt context.Context, chainID string, version string, txid string, signedProp *pb.SignedProposal, prop *pb.Proposal, cis *pb.ChaincodeInvocationSpec, cid *pb.ChaincodeID, txsim ledger.TxSimulator) (*pb.Response, *pb.ChaincodeEvent, error)
func (e *Endorser) disableJavaCCInst(cid *pb.ChaincodeID, cis *pb.ChaincodeInvocationSpec) error
//通过调用chaincode来模拟提案
func (e *Endorser) simulateProposal(ctx context.Context, chainID string, txid string, signedProp *pb.SignedProposal, prop *pb.Proposal, cid *pb.ChaincodeID, txsim ledger.TxSimulator) (*ccprovider.ChaincodeData, *pb.Response, []byte, *pb.ChaincodeEvent, error)
//从LSCC获取链码数据
func (e *Endorser) getCDSFromLSCC(ctx context.Context, chainID string, txid string, signedProp *pb.SignedProposal, prop *pb.Proposal, chaincodeID string, txsim ledger.TxSimulator) (*ccprovider.ChaincodeData, error)
//提案背书
func (e *Endorser) endorseProposal(ctx context.Context, chainID string, txid string, signedProp *pb.SignedProposal, proposal *pb.Proposal, response *pb.Response, simRes []byte, event *pb.ChaincodeEvent, visibility []byte, ccid *pb.ChaincodeID, txsim ledger.TxSimulator, cd *ccprovider.ChaincodeData) (*pb.ProposalResponse, error)
//提交模拟交易，仅测试使用
func (e *Endorser) commitTxSimulation(proposal *pb.Proposal, chainID string, signer msp.SigningIdentity, pResp *pb.ProposalResponse, blockNumber uint64) error
//代码在core/endorser/endorser.go

3.2、Endorser服务端ProcessProposal处理流程

Endorser服务端ProcessProposal处理流程，即func (e Endorser) ProcessProposal(ctx context.Context, signedProp pb.SignedProposal) (*pb.ProposalResponse, error)方法实现。

3.2.1、校验SignedProposal合法性，并获取ChannelHeader和SignatureHeader

//校验SignedProposal合法性
prop, hdr, hdrExt, err := validation.ValidateProposalMessage(signedProp)
//获取ChannelHeader
chdr, err := putils.UnmarshalChannelHeader(hdr.ChannelHeader)
//获取SignatureHeader
shdr, err := putils.GetSignatureHeader(hdr.SignatureHeader)
//代码在core/endorser/endorser.go

validation.ValidateProposalMessage(signedProp)代码如下：

func ValidateProposalMessage(signedProp *pb.SignedProposal) (*pb.Proposal, *common.Header, *pb.ChaincodeHeaderExtension, error) {
    prop, err := utils.GetProposal(signedProp.ProposalBytes) //获取type Proposal struct
    hdr, err := utils.GetHeader(prop.Header) //获取Proposal.Header
    chdr, shdr, err := validateCommonHeader(hdr) //校验Proposal.Header
    //检查来自创建者的签名
    err = checkSignatureFromCreator(shdr.Creator, signedProp.Signature, signedProp.ProposalBytes, chdr.ChannelId)
    //校验交易TxID，TxID由Nonce和Creator构成
    err = utils.CheckProposalTxID(
        chdr.TxId, //ChannelHeader.TxId
        shdr.Nonce, //SignatureHeader.Nonce
        shdr.Creator) //SignatureHeader.Creator

    switch common.HeaderType(chdr.Type) {
    case common.HeaderType_CONFIG:
        fallthrough
    case common.HeaderType_ENDORSER_TRANSACTION:
        //校验ChaincodeHeaderExtension
        chaincodeHdrExt, err := validateChaincodeProposalMessage(prop, hdr)
        return prop, hdr, chaincodeHdrExt, err
    default:
        return nil, nil, nil, fmt.Errorf("Unsupported proposal type %d", common.HeaderType(chdr.Type))
    }
}
//代码在core/common/validation/msgvalidation.go

3.2.2、校验是否系统链码且提案不可调用，获取chainID和TxId，获取Ledger并校验txid是否已存在，非系统链码校验提案权限（是否符合通道策略）

//校验是否系统链码且提案不可调用
if syscc.IsSysCCAndNotInvokableExternal(hdrExt.ChaincodeId.Name) {
    //如果是系统链码且提案不可调用
}
//获取chainID，即ChannelId
chainID := chdr.ChannelId
//获取交易TxId
txid := chdr.TxId
if chainID != "" {
    //获取Ledger
    lgr := peer.GetLedger(chainID)
    //校验txid是否已存在
    _, err := lgr.GetTransactionByID(txid)
    //非系统链码校验提案权限（是否符合通道策略）
    if !syscc.IsSysCC(hdrExt.ChaincodeId.Name) {
        err = e.checkACL(signedProp, chdr, shdr, hdrExt)
    }
}
//代码在core/endorser/endorser.go

3.2.3、获取账本的交易模拟器和历史记录查询器，并模拟提案执行

var txsim ledger.TxSimulator
var historyQueryExecutor ledger.HistoryQueryExecutor
if chainID != "" {
    //获取账本的交易模拟器
    txsim, err = e.getTxSimulator(chainID)
    //获取历史记录查询器
    historyQueryExecutor, err = e.getHistoryQueryExecutor(chainID)
    //HistoryQueryExecutorKey key = "historyqueryexecutorkey"
    //context.WithValue，将Key与对象建立关系
    ctx = context.WithValue(ctx, chaincode.HistoryQueryExecutorKey, historyQueryExecutor)
}
//模拟提案执行
cd, res, simulationResult, ccevent, err := e.simulateProposal(ctx, chainID, txid, signedProp, prop, hdrExt.ChaincodeId, txsim)
//代码在core/endorser/endorser.go

e.simulateProposal(ctx, chainID, txid, signedProp, prop, hdrExt.ChaincodeId, txsim)代码如下：模拟提案执行。

func (e *Endorser) simulateProposal(ctx context.Context, chainID string, txid string, signedProp *pb.SignedProposal, prop *pb.Proposal, cid *pb.ChaincodeID, txsim ledger.TxSimulator) (*ccprovider.ChaincodeData
, *pb.Response, []byte, *pb.ChaincodeEvent, error) {
    //获取ChaincodeInvocationSpec
    cis, err := putils.GetChaincodeInvocationSpec(prop)
    //禁用Java安装、实例化和立即升级
    err = e.disableJavaCCInst(cid, cis)
    //检查Escc和Vscc，暂未实现
    err = e.checkEsccAndVscc(prop)

    var cdLedger *ccprovider.ChaincodeData
    var version string
    if !syscc.IsSysCC(cid.Name) { //非系统链码
        //获取链码数据ChaincodeData
        cdLedger, err = e.getCDSFromLSCC(ctx, chainID, txid, signedProp, prop, cid.Name, txsim)
        //获取链码数据版本
        version = cdLedger.Version
        //检查链码实例化策略
        err = ccprovider.CheckInsantiationPolicy(cid.Name, version, cdLedger)
    } else {
        version = util.GetSysCCVersion() //获取系统链码版本
    }

    var simResult []byte
    var res *pb.Response
    var ccevent *pb.ChaincodeEvent
    //执行链码
    res, ccevent, err = e.callChaincode(ctx, chainID, version, txid, signedProp, prop, cis, cid, txsim)
    if txsim != nil {
        //获取交易模拟结果
        simResult, err = txsim.GetTxSimulationResults()
    }
    return cdLedger, res, simResult, ccevent, nil
}

//代码在core/endorser/endorser.go

e.endorseProposal(ctx, chainID, txid, signedProp, prop, res, simulationResult, ccevent, hdrExt.PayloadVisibility, hdrExt.ChaincodeId, txsim, cd)代码如下：为提案背书。

func (e *Endorser) callChaincode(ctxt context.Context, chainID string, version string, txid string, signedProp *pb.SignedProposal, prop *pb.Proposal, cis *pb.ChaincodeInvocationSpec, cid *pb.ChaincodeID, txsim ledger.TxSimulator) (*pb.Response, *pb.ChaincodeEvent, error) {
    var err error
    var res *pb.Response
    var ccevent *pb.ChaincodeEvent
    if txsim != nil {
        //TXSimulatorKey key = "txsimulatorkey"，key与对象建立关系
        ctxt = context.WithValue(ctxt, chaincode.TXSimulatorKey, txsim)
    }
    scc := syscc.IsSysCC(cid.Name) //是否系统链码
    cccid := ccprovider.NewCCContext(chainID, cid.Name, version, txid, scc, signedProp, prop)
    //执行链码
    res, ccevent, err = chaincode.ExecuteChaincode(ctxt, cccid, cis.ChaincodeSpec.Input.Args)
    //如果是生命周期管理系统链码，并且参数为实例化或升级
    if cid.Name == "lscc" && len(cis.ChaincodeSpec.Input.Args) >= 3 && (string(cis.ChaincodeSpec.Input.Args[0]) == "deploy" || string(cis.ChaincodeSpec.Input.Args[0]) == "upgrade") {
        var cds *pb.ChaincodeDeploymentSpec
        //获取ChaincodeDeploymentSpec
        cds, err = putils.GetChaincodeDeploymentSpec(cis.ChaincodeSpec.Input.Args[2])
        //待实例化或升级的链码执行实例化或升级
        cccid = ccprovider.NewCCContext(chainID, cds.ChaincodeSpec.ChaincodeId.Name, cds.ChaincodeSpec.ChaincodeId.Version, txid, false, signedProp, prop)
        _, _, err = chaincode.Execute(ctxt, cccid, cds)
    }
    return res, ccevent, err
}
//代码在core/endorser/endorser.go

Chaincode更详细内容，参考：Fabric 1.0源代码笔记 之 Chaincode（链码）

3.2.4、为提案背书，构造ProposalResponse并返回给Endorser客户端

var pResp *pb.ProposalResponse
//为提案背书，即调取escc系统链码
pResp, err = e.endorseProposal(ctx, chainID, txid, signedProp, prop, res, simulationResult, ccevent, hdrExt.PayloadVisibility, hdrExt.ChaincodeId, txsim, cd)
pResp.Response.Payload = res.Payload
return pResp, nil
//代码在core/endorser/endorser.go

e.endorseProposal(ctx, chainID, txid, signedProp, prop, res, simulationResult, ccevent, hdrExt.PayloadVisibility, hdrExt.ChaincodeId, txsim, cd)代码如下：

func (e *Endorser) endorseProposal(ctx context.Context, chainID string, txid string, signedProp *pb.SignedProposal, proposal *pb.Proposal, response *pb.Response, simRes []byte, event *pb.ChaincodeEvent, visibility []byte, ccid *pb.ChaincodeID, txsim ledger.TxSimulator, cd *ccprovider.ChaincodeData) (*pb.ProposalResponse, error) {
    isSysCC := cd == nil
    var escc string
    if isSysCC {
        escc = "escc"
    } else {
        escc = cd.Escc
    }

    var err error
    var eventBytes []byte
    if event != nil {
        eventBytes, err = putils.GetBytesChaincodeEvent(event)
    }

    resBytes, err := putils.GetBytesResponse(response)
    if isSysCC {
        ccid.Version = util.GetSysCCVersion()
    } else {
        ccid.Version = cd.Version
    }

    ccidBytes, err := putils.Marshal(ccid)
    args := [][]byte{[]byte(""), proposal.Header, proposal.Payload, ccidBytes, resBytes, simRes, eventBytes, visibility}
    version := util.GetSysCCVersion()
    ecccis := &pb.ChaincodeInvocationSpec{ChaincodeSpec: &pb.ChaincodeSpec{Type: pb.ChaincodeSpec_GOLANG, ChaincodeId: &pb.ChaincodeID{Name: escc}, Input: &pb.ChaincodeInput{Args: args}}}
    //执行escc系统链码
    res, _, err := e.callChaincode(ctx, chainID, version, txid, signedProp, proposal, ecccis, &pb.ChaincodeID{Name: escc}, txsim)
    prBytes := res.Payload
    pResp, err := putils.GetProposalResponse(prBytes)
    return pResp, nil
}

//代码在core/endorser/endorser.go