兄弟连区块链教程Fabric1.0源代码分析Orderer BroadcastServer，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 Orderer #BroadcastServer（Broadcast服务端）

1、BroadcastServer概述

BroadcastServer相关代码在protos/orderer、orderer目录下。

protos/orderer/ab.pb.go，AtomicBroadcastServer接口定义。
orderer/server.go，go，AtomicBroadcastServer接口实现。
有个图

2、AtomicBroadcastServer接口定义

2.1、AtomicBroadcastServer接口定义

type AtomicBroadcastServer interface {
    Broadcast(AtomicBroadcast_BroadcastServer) error
    Deliver(AtomicBroadcast_DeliverServer) error
}
//代码在protos/orderer/ab.pb.go
···

### 2.2、gRPC相关实现

var _AtomicBroadcast_serviceDesc = grpc.ServiceDesc{

ServiceName: "orderer.AtomicBroadcast",
HandlerType: (*AtomicBroadcastServer)(nil),
Methods:     []grpc.MethodDesc{},
Streams: []grpc.StreamDesc{
    {
        StreamName:    "Broadcast",
        Handler:       _AtomicBroadcast_Broadcast_Handler,
        ServerStreams: true,
        ClientStreams: true,
    },
    {
        StreamName:    "Deliver",
        Handler:       _AtomicBroadcast_Deliver_Handler,
        ServerStreams: true,
        ClientStreams: true,
    },
},
Metadata: "orderer/ab.proto",

}

func RegisterAtomicBroadcastServer(s *grpc.Server, srv AtomicBroadcastServer) {

s.RegisterService(&_AtomicBroadcast_serviceDesc, srv)

}

func _AtomicBroadcast_Broadcast_Handler(srv interface{}, stream grpc.ServerStream) error {

return srv.(AtomicBroadcastServer).Broadcast(&atomicBroadcastBroadcastServer{stream})

}

func _AtomicBroadcast_Deliver_Handler(srv interface{}, stream grpc.ServerStream) error {

return srv.(AtomicBroadcastServer).Deliver(&atomicBroadcastDeliverServer{stream})

}
//代码在protos/orderer/ab.pb.go

## 3、AtomicBroadcastServer接口实现

### 3.1、server结构体

server结构体：

type server struct {

bh broadcast.Handler
dh deliver.Handler

}

type broadcastSupport struct {

multichain.Manager
broadcast.ConfigUpdateProcessor

}
//代码在orderer/server.go

broadcast.Handler：

type Handler interface {

Handle(srv ab.AtomicBroadcast_BroadcastServer) error

}

type handlerImpl struct {

sm SupportManager

}

func NewHandlerImpl(sm SupportManager) Handler {

return &handlerImpl{
    sm: sm,
}

}

type SupportManager interface {

ConfigUpdateProcessor
GetChain(chainID string) (Support, bool)

}

type ConfigUpdateProcessor interface { //处理通道配置更新

Process(envConfigUpdate *cb.Envelope) (*cb.Envelope, error)

}
//代码在orderer/common/broadcast/broadcast.go

deliver.Handler：

type Handler interface {

Handle(srv ab.AtomicBroadcast_DeliverServer) error

}

type deliverServer struct {

sm SupportManager

}

type SupportManager interface {

GetChain(chainID string) (Support, bool)

}
//代码在orderer/common/deliver/deliver.go

### 3.2、server结构体相关方法

//构建server结构体
func NewServer(ml multichain.Manager, signer crypto.LocalSigner) ab.AtomicBroadcastServer
//s.bh.Handle(srv)
func (s *server) Broadcast(srv ab.AtomicBroadcast_BroadcastServer) error
//s.dh.Handle(srv)
func (s *server) Deliver(srv ab.AtomicBroadcast_DeliverServer) error
//代码在orderer/server.go

func NewServer(ml multichain.Manager, signer crypto.LocalSigner) ab.AtomicBroadcastServer代码如下：

func NewServer(ml multichain.Manager, signer crypto.LocalSigner) ab.AtomicBroadcastServer {

s := &server{
    dh: deliver.NewHandlerImpl(deliverSupport{Manager: ml}),
    bh: broadcast.NewHandlerImpl(broadcastSupport{
        Manager:               ml,
        ConfigUpdateProcessor: configupdate.New(ml.SystemChannelID(), configUpdateSupport{Manager: ml}, signer),
    }),
}
return s

}
//代码在orderer/server.go

### 3.3、Broadcast服务端Broadcast处理流程

Broadcast服务端Broadcast处理流程，即broadcast.handlerImpl.Handle方法。

#### 3.3.1、接收Envelope消息，并获取Payload和ChannelHeader

msg, err := srv.Recv() //接收Envelope消息
payload, err := utils.UnmarshalPayload(msg.Payload) //反序列化获取Payload
chdr, err := utils.UnmarshalChannelHeader(payload.Header.ChannelHeader) //反序列化获取ChannelHeader
//代码在orderer/common/broadcast/broadcast.go

#### 3.3.2、如果消息类型为channel配置或更新，则使用multichain.Manager处理消息

if chdr.Type == int32(cb.HeaderType_CONFIG_UPDATE) { //如果是channel配置或更新

msg, err = bh.sm.Process(msg) //configupdate.Processor.Process方法

}
//代码在orderer/common/broadcast/broadcast.go

msg, err = bh.sm.Process(msg)代码如下：

func (p Processor) Process(envConfigUpdate cb.Envelope) (*cb.Envelope, error) {

channelID, err := channelID(envConfigUpdate) //获取ChannelHeader.ChannelId
//multichain.Manager.GetChain方法，获取chainSupport，以及chain是否存在
support, ok := p.manager.GetChain(channelID)
if ok {
    //已存在的channel配置，调取multichain.Manager.ProposeConfigUpdate方法
    return p.existingChannelConfig(envConfigUpdate, channelID, support)
}
//新channel配置，调取multichain.Manager.NewChannelConfig方法
return p.newChannelConfig(channelID, envConfigUpdate)

}
//代码在orderer/configupdate/configupdate.go

#### 3.3.3、其他消息类型或channel消息处理后，接受消息并加入排序

support, ok := bh.sm.GetChain(chdr.ChannelId) //获取chainSupport
_, filterErr := support.Filters().Apply(msg) //filter.RuleSet.Apply方法
//调取Chain.Enqueue方法，接受消息，加入排序
support.Enqueue(msg)
//代码在orderer/common/broadcast/broadcast.go

#### 3.3.4、向客户端发送响应信息

err = srv.Send(&ab.BroadcastResponse{Status: cb.Status_SUCCESS})
//代码在orderer/common/broadcast/broadcast.go

### 3.4、Broadcast服务端Deliver处理流程

Broadcast服务端Deliver处理流程，即deliver.deliverServer.Handle方法。

func (ds *deliverServer) Handle(srv ab.AtomicBroadcast_DeliverServer) error {

for {
    //接收客户端查询请求
    envelope, err := srv.Recv()
    payload, err := utils.UnmarshalPayload(envelope.Payload)
    chdr, err := utils.UnmarshalChannelHeader(payload.Header.ChannelHeader)
    chain, ok := ds.sm.GetChain(chdr.ChannelId)

    erroredChan := chain.Errored()
    select {
    case <-erroredChan:
        return sendStatusReply(srv, cb.Status_SERVICE_UNAVAILABLE)
    default:

    }

    lastConfigSequence := chain.Sequence()

    sf := sigfilter.New(policies.ChannelReaders, chain.PolicyManager())
    result, _ := sf.Apply(envelope)

    seekInfo := &ab.SeekInfo{}
    err = proto.Unmarshal(payload.Data, seekInfo)

    cursor, number := chain.Reader().Iterator(seekInfo.Start)
    var stopNum uint64
    switch stop := seekInfo.Stop.Type.(type) {
    case *ab.SeekPosition_Oldest:
        stopNum = number
    case *ab.SeekPosition_Newest:
        stopNum = chain.Reader().Height() - 1
    case *ab.SeekPosition_Specified:
        stopNum = stop.Specified.Number
        if stopNum < number {
            return sendStatusReply(srv, cb.Status_BAD_REQUEST)
        }
    }

    for {
        if seekInfo.Behavior == ab.SeekInfo_BLOCK_UNTIL_READY {
            select {
            case <-erroredChan:
                return sendStatusReply(srv, cb.Status_SERVICE_UNAVAILABLE)
            case <-cursor.ReadyChan():
            }
        } else {
            select {
            case <-cursor.ReadyChan():
            default:
                return sendStatusReply(srv, cb.Status_NOT_FOUND)
            }
        }

        currentConfigSequence := chain.Sequence()
        if currentConfigSequence > lastConfigSequence {
            lastConfigSequence = currentConfigSequence
            sf := sigfilter.New(policies.ChannelReaders, chain.PolicyManager())
            result, _ := sf.Apply(envelope)

        }

        block, status := cursor.Next()
        err := sendBlockReply(srv, block)
        if stopNum == block.Header.Number {
            break
        }
    }

    err := sendStatusReply(srv, cb.Status_SUCCESS)
}

}