etcd网络层(五)——Transporter接口实现

一、Transport结构体

type Transport struct {
	Logger *zap.Logger

	DialTimeout time.Duration // maximum duration before timing out dial of the request，dial的超时时间
	// DialRetryFrequency defines the frequency of streamReader dial retrial attempts;
	// a distinct rate limiter is created per every peer (default value: 10 events/sec)
	DialRetryFrequency rate.Limit   //定义streamReader dial 重试尝试的频率；每一个peer都有不同频率的限制

	TLSInfo transport.TLSInfo // TLS information used when creating connection  tls信息，创建连接时使用

	ID          types.ID   // local member ID  当前节点自己的ID
	URLs        types.URLs // local peer URLs  当前节点与集群中其他节点交互时使用的URL地址
	ClusterID   types.ID   // raft cluster ID for request validation  当前节点所在的集群的ID
	/*
	Raft是一个接口，其实现的底层封装了前面介绍的etcd-raft模块，当rafthttp.Transport收到消息之后，会将其交给Raft实例进行交互
	*/
	Raft        Raft       // raft state machine, to which the Transport forwards received messages and reports status
	Snapshotter *snap.Snapshotter  //负责管理快照文件
	
	ServerStats *stats.ServerStats // used to record general transportation statistics   用于统计一般的transportation统计
	// used to record transportation statistics with followers when
	// performing as leader in raft protocol
	LeaderStats *stats.LeaderStats    //raft协议中的leader节点统计followers节点的 transportation 状态
	// ErrorC is used to report detected critical errors, e.g.,
	// the member has been permanently removed from the cluster
	// When an error is received from ErrorC, user should stop raft state
	// machine and thus stop the Transport.
	ErrorC chan error

	streamRt   http.RoundTripper // roundTripper used by streams   Stream消息通道中使用http.RoundTripper实例,HTTP长连接
	pipelineRt http.RoundTripper // roundTripper used by pipelines  Pipeline消息通道中使用的http.RoundTripper实例,传输完成后会立即关闭连接，传输数据量较大、发送频率较低的消息，如MsgSnap消息

	mu      sync.RWMutex         // protect the remote and peer map
	//remote中只封装了pipeline实例，remote主要负责发送快照数据，帮助新加入的节点快速追上其他节点的数据
	remotes map[types.ID]*remote // remotes map that helps newly joined member to catch up
	/*
	Peer接口是当前节点对集群中其他节点的抽象表示。对于当前节点来说，集群中其他节点在本地都会有一个Peer实例与之对应，
	peers字段维护了节点ID到对应Peer实例之间的映射关系
	*/
	peers   map[types.ID]Peer    // peers map
	//用于探测Pipeline消息通道是否可用。
	prober probing.Prober
}

Transport实现了Transporter接口。它提供了向对等端发送raft消息的功能，并且接受其他节点的消息。

ID记录当前节点的ID

ClusterID记录当前节点的集群ID

Raft接口，用于和raft模块进行交互，etcd-raft前面已经介绍。

streamRt和pipelineRt 底层都是http.RoundTripper的默认实现http.Transport，完成HTTP事务。

remote remote中只封装了pipeline实例，remote主要负责发送快照数据，帮助新加入的节点快速追上其他节点的数据

peers 记录当前节点和集群中其他节点的对应关系(网络层)，Peer接口是当前节点对集群中其他节点的抽象表示。对于当前节点来说ÿ