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。

1

Syncing方法源代码

1.  `// Syncing returns false in case the node is currently not syncing with the network. It can be up to date or has not`2.  `// yet received the latest block headers from its pears. In case it is synchronizing:`3.  `// - startingBlock: block number this node started to synchronise from`4.  `// - currentBlock:  block number this node is currently importing`5.  `// - highestBlock:  block number of the highest block header this node has received from peers`6.  `// - pulledStates:  number of state entries processed until now`7.  `// - knownStates:   number of known state entries that still need to be pulled`8.  `func (s *PublicEthereumAPI)  Syncing()  (interface{}, error)  {`9.  `progress := s.b.Downloader().Progress()`11.  `// Return not syncing if the synchronisation already completed`12.  `if progress.CurrentBlock  >= progress.HighestBlock  {`13.  `return  false,  nil`14.  `}`15.  `// Otherwise gather the block sync stats`16.  `return map[string]interface{}{`17.  `"startingBlock": hexutil.Uint64(progress.StartingBlock),`18.  `"currentBlock": hexutil.Uint64(progress.CurrentBlock),`19.  `"highestBlock": hexutil.Uint64(progress.HighestBlock),`20.  `"pulledStates": hexutil.Uint64(progress.PulledStates),`21.  `"knownStates": hexutil.Uint64(progress.KnownStates),`22.  `},  nil`23.  `}`

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.  `}`

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：

1.  `progress := s.b.Downloader().Progress()`

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.  `}`

从这端代码我们可以分析得出，curren

• full模式：返回当前区块的高度；

• fast模式：返回fast区块的高度；

• light模式：返回当前的header编号；

• 而KnownStates又是由PulledStates的值加上当前处于pending装的值获得。

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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