go-ethereum原始碼分析-consensus
阿新 • • 發佈:2019-02-18
原始碼包路徑:github.com/ethereum/go-ethereum/consensus/
共識演算法引擎介面的定義如下
type Engine interface { // Author retrieves the Ethereum address of the account that minted the given // block, which may be different from the header's coinbase if a consensus // engine is based on signatures. Author(header *types.Header) (common.Address,error) // VerifyHeader checks whether a header conforms to the consensus rules of a // given engine. Verifying the seal may be done optionally here, or explicitly // via the VerifySeal method. VerifyHeader(chain ChainReader, header *types.Header, seal bool) error // VerifyHeaders is similar to VerifyHeader, but verifies a batch of headers// concurrently. The method returns a quit channel to abort the operations and // a results channel to retrieve the async verifications (the order is that of // the input slice). VerifyHeaders(chain ChainReader, headers []*types.Header, seals []bool) (chan<- struct{}, <-chan error) // VerifyUncles verifies that the given block's uncles conform to the consensus// rules of a given engine. VerifyUncles(chain ChainReader, block *types.Block) error // VerifySeal checks whether the crypto seal on a header is valid according to // the consensus rules of the given engine. VerifySeal(chain ChainReader, header *types.Header) error // Prepare initializes the consensus fields of a block header according to the // rules of a particular engine. The changes are executed inline. Prepare(chain ChainReader, header *types.Header) error // Finalize runs any post-transaction state modifications (e.g. block rewards) // and assembles the final block. // Note: The block header and state database might be updated to reflect any // consensus rules that happen at finalization (e.g. block rewards). Finalize(chain ChainReader, header *types.Header, state *state.StateDB, txs []*types.Transaction, uncles []*types.Header, receipts []*types.Receipt) (*types.Block, error) // Seal generates a new block for the given input block with the local miner's // seal place on top. Seal(chain ChainReader, block *types.Block, stop <-chan struct{}) (*types.Block, error) // APIs returns the RPC APIs this consensus engine provides. APIs(chain ChainReader) []rpc.API } // PoW is a consensus engine based on proof-of-work. type PoW interface { Engine // Hashrate returns the current mining hashrate of a PoW consensus engine. Hashrate() float64 }
其中最主要的是
prepare 預處理當前區塊的頭資訊(比如 挖礦難度)(Homestead)
diff = (parent_diff + (parent_diff / 2048 * max(1 - (block_timestamp - parent_timestamp) / 10, -99)) ) + 2^(periodCount - 2)
- parent_diff :上一個區塊的難度
- block_timestamp :當前塊的時間戳
- parent_timestamp:上一個塊的時間戳
- periodCount :區塊num/100000
block_timestamp - parent_timestamp 差值小於10秒 變難
block_timestamp - parent_timestamp 差值10-20秒 不變
- block_timestamp - parent_timestamp 差值大於20秒 變容易,並且大的越多,越容易,但是又上限
- 總體上塊的難度是遞增的
seal 開始做挖礦的事情,“解題”直到成功或者退出
- 根據挖礦難度計算目標值
- 選取隨機數nonce+區塊頭(不包含nonce)的hash,再做一次hash,結果小於目標值,則退出,否則迴圈重試
- 如果外部退出了(比如已經收到這個塊了),則立馬放棄當前塊的打包
Finalize 做挖礦成功後最後善後的事情
- 計算礦工的獎勵:區塊獎勵,叔塊獎勵,
- 但是這裡沒有交易費~~
verifyHeader
- 校驗extra大小
- 校驗區塊時間戳,跟當前時間比
- 校驗難度值
- 校驗gaslimit上線
- 校驗區塊的總gasuserd小於 gaslimit
- 校驗區塊的gaslimit 是在合理範圍
- 特殊的校驗,比如dao分叉後的幾個塊extra裡面寫了特殊資料,來判斷一下
VerifySeal
- 校驗難度的有效性
- nonce是否小於目標值(解題成功)