以太坊源码分析-同步之Syncing接口

image在节点同步的过程中，我们经常需要执行eth.syncing来查看当前的同步情况，本篇博客带领大家看一下syncing api的源代码实现。
1Syncing方法源代码

// Syncing returns false in case the node is currently not syncing with the network. It can be up to date or has not`// yet received the latest block headers from its pears. In case it is synchronizing:`// - startingBlock: block number this node started to synchronise from`// - currentBlock: block number this node is currently importing`// - highestBlock: block number of the highest block header this node has received from peers`// - pulledStates: number of state entries processed until now`// - knownStates: number of known state entries that still need to be pulled`func (s *PublicEthereumAPI) Syncing() (interface{}, error) {`progress := s.b.Downloader().Progress()`// Return not syncing if the synchronisation already completed`if progress.CurrentBlock >= progress.HighestBlock {`return false, nil`}`// Otherwise gather the block sync stats`return map[string]interface{}{`"startingBlock": hexutil.Uint64(progress.StartingBlock),`"currentBlock": hexutil.Uint64(progress.CurrentBlock),`"highestBlock": hexutil.Uint64(progress.HighestBlock),`"pulledStates": hexutil.Uint64(progress.PulledStates),`"knownStates": hexutil.Uint64(progress.KnownStates),`}, nil`}`

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Syncing方法的源代码很简单，注释说明也已经很清楚了。通过这段源代码我们可以得知一下信息：

当然CurrentBlock大于等于HighestBlock时返回false，这也正是通常所说的同步完成之后，再执行eth.syncing()函数会返回false的原因。
startingBlock：开始同步的起始区块编号；
currentBlock：当前正在导入的区块编号；
highestBlock：通过所链接的节点获得的当前最高的区块高度；
pulledStates：当前已经拉取的状态条目数；
knownStates：当前已知的待拉取的总状态条目数。

2对应的结构体代码下面是同步信息对应的结构体的代码及注释。

1. `// SyncProgress gives progress indications when the node is synchronising with`2. `// the Ethereum network.`3. `type SyncProgress struct {`4. `StartingBlock uint64 // Block number where sync began`5. `CurrentBlock uint64 // Current block number where sync is at`6. `HighestBlock uint64 // Highest alleged block number in the chain`7. `PulledStates uint64 // Number of state trie entries already downloaded`8. `KnownStates uint64 // Total number of state trie entries known about`9. `}`

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3结构体信息计算上面看到当执行eth.syncing返回结果信息的代码，再延伸一下看看这些数据从哪里来。进入下面Progress方法的内部实现：

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可以看到如下代码：

1. `// Progress retrieves the synchronisation boundaries, specifically the origin`2. `// block where synchronisation started at (may have failed/suspended); the block`3. `// or header sync is currently at; and the latest known block which the sync targets.`4. `//`5. `// In addition, during the state download phase of fast synchronisation the number`6. `// of processed and the total number of known states are also returned. Otherwise`7. `// these are zero.`8. `func (d *Downloader) Progress() ethereum.SyncProgress {`9. `// Lock the current stats and return the progress`10. `d.syncStatsLock.RLock()`11. `defer d.syncStatsLock.RUnlock()`13. `current := uint64(0)`14. `switch d.mode {`15. `case FullSync:`16. `current = d.blockchain.CurrentBlock().NumberU64()`17. `case FastSync:`18. `current = d.blockchain.CurrentFastBlock().NumberU64()`19. `case LightSync:`20. `current = d.lightchain.CurrentHeader().Number.Uint64()`21. `}`22. `return ethereum.SyncProgress{`23. `StartingBlock: d.syncStatsChainOrigin,`24. `CurrentBlock: current,`25. `HighestBlock: d.syncStatsChainHeight,`26. `PulledStates: d.syncStatsState.processed,`27. `KnownStates: d.syncStatsState.processed + d.syncStatsState.pending,`28. `}`29. `}`

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从这端代码我们可以分析得出，curren

4总结通过上面源代码分析，我们已经可以明了的看到当我们执行eth.sycing时返回不同的结果信息所代表的含义。欢迎大家关注微信公众号，获取最新的相关技术分享。

内容来源：程序新视界
作者：二师兄

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