兄弟连区块链教程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
```go
type EndorserServer interface {
ProcessProposal(context.Context, *SignedProposal) (*ProposalResponse, error)
}
//代码在protos/peer/peer.pb.go
```
### 2.2、gRPC相关实现
```go
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
```go
type Endorser struct {
policyChecker policy.PolicyChecker //策略检查器
}
//代码在core/endorser/endorser.go
```
涉及方法如下：
```go
//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
```go
//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：
```go
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）
```go
//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
```go
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。
```go
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。
```go
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
```go
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：
```go
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
```
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