以太坊源码分析(31)eth-downloader-peer源码分析

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我是靠谱客的博主眼睛大期待，最近开发中收集的这篇文章主要介绍以太坊源码分析(31)eth-downloader-peer源码分析，觉得挺不错的，现在分享给大家，希望可以做个参考。

概述

   peer模块包含了downloader使用的peer节点，封装了吞吐量，是否空闲，并记录了之前失败的信息。 
 
  ## peer 
 
       // peerConnection represents an active peer from which hashes and blocks are retrieved. 
 
       type peerConnection struct { 
 
           id string // Unique identifier of the peer 
 
           headerIdle int32 // Current header activity state of the peer (idle = 0, active = 1) 当前的header获取的工作状态。 
 
           blockIdle int32 // Current block activity state of the peer (idle = 0, active = 1)    当前的区块获取的工作状态 
 
           receiptIdle int32 // Current receipt activity state of the peer (idle = 0, active = 1) 当前的收据获取的工作状态 
 
           stateIdle int32 // Current node data activity state of the peer (idle = 0, active = 1) 当前节点状态的工作状态 
 
           headerThroughput float64 // Number of headers measured to be retrievable per second    //记录每秒能够接收多少个区块头的度量值 
 
           blockThroughput float64 // Number of blocks (bodies) measured to be retrievable per second //记录每秒能够接收多少个区块的度量值 
 
           receiptThroughput float64 // Number of receipts measured to be retrievable per second 记录每秒能够接收多少个收据的度量值 
 
           stateThroughput float64 // Number of node data pieces measured to be retrievable per second 记录每秒能够接收多少个账户状态的度量值 
 
           rtt time.Duration // Request round trip time to track responsiveness (QoS) 请求回应时间 
 
           headerStarted time.Time // Time instance when the last header fetch was started    记录最后一个header fetch的请求时间 
 
           blockStarted time.Time // Time instance when the last block (body) fetch was started 
 
           receiptStarted time.Time // Time instance when the last receipt fetch was started 
 
           stateStarted time.Time // Time instance when the last node data fetch was started 
 
           lacking map[common.Hash]struct{} // Set of hashes not to request (didn't have previously) 记录的Hash值不会去请求，一般是因为之前的请求失败 
 
           peer Peer           // eth的peer 
 
           version int // Eth protocol version number to switch strategies 
 
           log log.Logger // Contextual logger to add extra infos to peer logs 
 
           lock sync.RWMutex 
 
       } 
 
   FetchXXX 
 
   FetchHeaders FetchBodies等函数 主要调用了eth.peer的功能来进行发送数据请求。 
 
       // FetchHeaders sends a header retrieval request to the remote peer. 
 
       func (p *peerConnection) FetchHeaders(from uint64, count int) error { 
 
           // Sanity check the protocol version 
 
           if p.version < 62 { 
 
               panic(fmt.Sprintf("header fetch [eth/62+] requested on eth/%d", p.version)) 
 
           } 
 
           // Short circuit if the peer is already fetching 
 
           if !atomic.CompareAndSwapInt32(&p.headerIdle, 0, 1) { 
 
               return errAlreadyFetching 
 
           } 
 
           p.headerStarted = time.Now() 
 
           // Issue the header retrieval request (absolut upwards without gaps) 
 
           go p