以太坊源码分析-同步之Syncing接口
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内容来源：程序新视界
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。
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// 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
}
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。
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下面是同步信息对应的结构体的代码及注释。
// SyncProgress gives progress indications when the node is synchronising with
// the Ethereum network.
type SyncProgress struct {
StartingBlock uint64 // Block number where sync began
CurrentBlock uint64 // Current block number where sync is at
HighestBlock uint64 // Highest alleged block number in the chain
PulledStates uint64 // Number of state trie entries already downloaded
KnownStates uint64 // Total number of state trie entries known about
}
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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：
progress := s.b.Downloader().Progress()
可以看到如下代码：
// Progress retrieves the synchronisation boundaries, specifically the origin
// block where synchronisation started at (may have failed/suspended); the block
// or header sync is currently at; and the latest known block which the sync targets.
//
// In addition, during the state download phase of fast synchronisation the number
// of processed and the total number of known states are also returned. Otherwise
// these are zero.
func (d *Downloader) Progress() ethereum.SyncProgress {
// Lock the current stats and return the progress
d.syncStatsLock.RLock()
defer d.syncStatsLock.RUnlock()
current := uint64(0)
switch d.mode {
case FullSync:
current = d.blockchain.CurrentBlock().NumberU64()
case FastSync:
current = d.blockchain.CurrentFastBlock().NumberU64()
case LightSync:
current = d.lightchain.CurrentHeader().Number.Uint64()
}
return ethereum.SyncProgress{
StartingBlock: d.syncStatsChainOrigin,
CurrentBlock: current,
HighestBlock: d.syncStatsChainHeight,
PulledStates: d.syncStatsState.processed,
KnownStates: d.syncStatsState.processed + d.syncStatsState.pending,
}
}
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。
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