兄弟连区块链教程Broadcast服务端
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。
## 2、AtomicBroadcastServer接口定义
### 2.1、AtomicBroadcastServer接口定义
```go
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
```go
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：
```go
type server struct {
bh broadcast.Handler
dh deliver.Handler
}
type broadcastSupport struct {
multichain.Manager
broadcast.ConfigUpdateProcessor
}
//代码在orderer/server.go
```
broadcast.Handler：
```go
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：
```go
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
```go
//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：
```go
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
```go
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：
```go
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
```go
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
```go
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。
```go
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)
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