Official Go implementation of the Ethereum protocol
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go-ethereum/consensus/ethash/sealer.go

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// Copyright 2017 The go-ethereum Authors
// This file is part of the go-ethereum library.
//
// The go-ethereum library is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// The go-ethereum library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
package ethash
import (
"bytes"
"context"
crand "crypto/rand"
"encoding/json"
"errors"
"math"
"math/big"
"math/rand"
"net/http"
"runtime"
"sync"
"time"
"github.com/ethereum/go-ethereum/common"
"github.com/ethereum/go-ethereum/common/hexutil"
"github.com/ethereum/go-ethereum/consensus"
"github.com/ethereum/go-ethereum/core/types"
)
const (
// staleThreshold is the maximum depth of the acceptable stale but valid ethash solution.
staleThreshold = 7
)
var (
errNoMiningWork = errors.New("no mining work available yet")
errInvalidSealResult = errors.New("invalid or stale proof-of-work solution")
)
// Seal implements consensus.Engine, attempting to find a nonce that satisfies
// the block's difficulty requirements.
func (ethash *Ethash) Seal(chain consensus.ChainHeaderReader, block *types.Block, results chan<- *types.Block, stop <-chan struct{}) error {
// If we're running a fake PoW, simply return a 0 nonce immediately
if ethash.config.PowMode == ModeFake || ethash.config.PowMode == ModeFullFake {
header := block.Header()
header.Nonce, header.MixDigest = types.BlockNonce{}, common.Hash{}
select {
case results <- block.WithSeal(header):
default:
ethash.config.Log.Warn("Sealing result is not read by miner", "mode", "fake", "sealhash", ethash.SealHash(block.Header()))
}
return nil
}
// If we're running a shared PoW, delegate sealing to it
if ethash.shared != nil {
return ethash.shared.Seal(chain, block, results, stop)
}
// Create a runner and the multiple search threads it directs
abort := make(chan struct{})
ethash.lock.Lock()
threads := ethash.threads
if ethash.rand == nil {
seed, err := crand.Int(crand.Reader, big.NewInt(math.MaxInt64))
if err != nil {
ethash.lock.Unlock()
return err
}
ethash.rand = rand.New(rand.NewSource(seed.Int64()))
}
ethash.lock.Unlock()
if threads == 0 {
threads = runtime.NumCPU()
}
if threads < 0 {
threads = 0 // Allows disabling local mining without extra logic around local/remote
}
// Push new work to remote sealer
if ethash.remote != nil {
ethash.remote.workCh <- &sealTask{block: block, results: results}
}
var (
pend sync.WaitGroup
locals = make(chan *types.Block)
)
for i := 0; i < threads; i++ {
pend.Add(1)
go func(id int, nonce uint64) {
defer pend.Done()
ethash.mine(block, id, nonce, abort, locals)
}(i, uint64(ethash.rand.Int63()))
}
// Wait until sealing is terminated or a nonce is found
go func() {
var result *types.Block
select {
case <-stop:
// Outside abort, stop all miner threads
close(abort)
case result = <-locals:
// One of the threads found a block, abort all others
select {
case results <- result:
default:
ethash.config.Log.Warn("Sealing result is not read by miner", "mode", "local", "sealhash", ethash.SealHash(block.Header()))
}
close(abort)
case <-ethash.update:
// Thread count was changed on user request, restart
close(abort)
if err := ethash.Seal(chain, block, results, stop); err != nil {
ethash.config.Log.Error("Failed to restart sealing after update", "err", err)
}
}
// Wait for all miners to terminate and return the block
pend.Wait()
}()
return nil
}
// mine is the actual proof-of-work miner that searches for a nonce starting from
// seed that results in correct final block difficulty.
func (ethash *Ethash) mine(block *types.Block, id int, seed uint64, abort chan struct{}, found chan *types.Block) {
// Extract some data from the header
var (
header = block.Header()
hash = ethash.SealHash(header).Bytes()
target = new(big.Int).Div(two256, header.Difficulty)
number = header.Number.Uint64()
dataset = ethash.dataset(number, false)
)
// Start generating random nonces until we abort or find a good one
var (
attempts = int64(0)
nonce = seed
powBuffer = new(big.Int)
)
logger := ethash.config.Log.New("miner", id)
logger.Trace("Started ethash search for new nonces", "seed", seed)
search:
for {
select {
case <-abort:
// Mining terminated, update stats and abort
logger.Trace("Ethash nonce search aborted", "attempts", nonce-seed)
ethash.hashrate.Mark(attempts)
break search
default:
// We don't have to update hash rate on every nonce, so update after after 2^X nonces
attempts++
if (attempts % (1 << 15)) == 0 {
ethash.hashrate.Mark(attempts)
attempts = 0
}
// Compute the PoW value of this nonce
digest, result := hashimotoFull(dataset.dataset, hash, nonce)
if powBuffer.SetBytes(result).Cmp(target) <= 0 {
// Correct nonce found, create a new header with it
header = types.CopyHeader(header)
header.Nonce = types.EncodeNonce(nonce)
header.MixDigest = common.BytesToHash(digest)
// Seal and return a block (if still needed)
select {
case found <- block.WithSeal(header):
logger.Trace("Ethash nonce found and reported", "attempts", nonce-seed, "nonce", nonce)
case <-abort:
logger.Trace("Ethash nonce found but discarded", "attempts", nonce-seed, "nonce", nonce)
}
break search
}
nonce++
}
}
// Datasets are unmapped in a finalizer. Ensure that the dataset stays live
// during sealing so it's not unmapped while being read.
runtime.KeepAlive(dataset)
}
// This is the timeout for HTTP requests to notify external miners.
const remoteSealerTimeout = 1 * time.Second
type remoteSealer struct {
works map[common.Hash]*types.Block
rates map[common.Hash]hashrate
currentBlock *types.Block
currentWork [4]string
notifyCtx context.Context
cancelNotify context.CancelFunc // cancels all notification requests
reqWG sync.WaitGroup // tracks notification request goroutines
ethash *Ethash
noverify bool
notifyURLs []string
results chan<- *types.Block
workCh chan *sealTask // Notification channel to push new work and relative result channel to remote sealer
fetchWorkCh chan *sealWork // Channel used for remote sealer to fetch mining work
submitWorkCh chan *mineResult // Channel used for remote sealer to submit their mining result
fetchRateCh chan chan uint64 // Channel used to gather submitted hash rate for local or remote sealer.
submitRateCh chan *hashrate // Channel used for remote sealer to submit their mining hashrate
requestExit chan struct{}
exitCh chan struct{}
}
// sealTask wraps a seal block with relative result channel for remote sealer thread.
type sealTask struct {
block *types.Block
results chan<- *types.Block
}
// mineResult wraps the pow solution parameters for the specified block.
type mineResult struct {
nonce types.BlockNonce
mixDigest common.Hash
hash common.Hash
errc chan error
}
// hashrate wraps the hash rate submitted by the remote sealer.
type hashrate struct {
id common.Hash
ping time.Time
rate uint64
done chan struct{}
}
// sealWork wraps a seal work package for remote sealer.
type sealWork struct {
errc chan error
res chan [4]string
}
func startRemoteSealer(ethash *Ethash, urls []string, noverify bool) *remoteSealer {
ctx, cancel := context.WithCancel(context.Background())
s := &remoteSealer{
ethash: ethash,
noverify: noverify,
notifyURLs: urls,
notifyCtx: ctx,
cancelNotify: cancel,
works: make(map[common.Hash]*types.Block),
rates: make(map[common.Hash]hashrate),
workCh: make(chan *sealTask),
fetchWorkCh: make(chan *sealWork),
submitWorkCh: make(chan *mineResult),
fetchRateCh: make(chan chan uint64),
submitRateCh: make(chan *hashrate),
requestExit: make(chan struct{}),
exitCh: make(chan struct{}),
}
go s.loop()
return s
}
func (s *remoteSealer) loop() {
defer func() {
s.ethash.config.Log.Trace("Ethash remote sealer is exiting")
s.cancelNotify()
s.reqWG.Wait()
close(s.exitCh)
}()
ticker := time.NewTicker(5 * time.Second)
defer ticker.Stop()
for {
select {
case work := <-s.workCh:
// Update current work with new received block.
// Note same work can be past twice, happens when changing CPU threads.
s.results = work.results
s.makeWork(work.block)
s.notifyWork()
case work := <-s.fetchWorkCh:
// Return current mining work to remote miner.
if s.currentBlock == nil {
work.errc <- errNoMiningWork
} else {
work.res <- s.currentWork
}
case result := <-s.submitWorkCh:
// Verify submitted PoW solution based on maintained mining blocks.
if s.submitWork(result.nonce, result.mixDigest, result.hash) {
result.errc <- nil
} else {
result.errc <- errInvalidSealResult
}
case result := <-s.submitRateCh:
// Trace remote sealer's hash rate by submitted value.
s.rates[result.id] = hashrate{rate: result.rate, ping: time.Now()}
close(result.done)
case req := <-s.fetchRateCh:
// Gather all hash rate submitted by remote sealer.
var total uint64
for _, rate := range s.rates {
// this could overflow
total += rate.rate
}
req <- total
case <-ticker.C:
// Clear stale submitted hash rate.
for id, rate := range s.rates {
if time.Since(rate.ping) > 10*time.Second {
delete(s.rates, id)
}
}
// Clear stale pending blocks
if s.currentBlock != nil {
for hash, block := range s.works {
if block.NumberU64()+staleThreshold <= s.currentBlock.NumberU64() {
delete(s.works, hash)
}
}
}
case <-s.requestExit:
return
}
}
}
// makeWork creates a work package for external miner.
//
// The work package consists of 3 strings:
//
// result[0], 32 bytes hex encoded current block header pow-hash
// result[1], 32 bytes hex encoded seed hash used for DAG
// result[2], 32 bytes hex encoded boundary condition ("target"), 2^256/difficulty
// result[3], hex encoded block number
func (s *remoteSealer) makeWork(block *types.Block) {
hash := s.ethash.SealHash(block.Header())
s.currentWork[0] = hash.Hex()
s.currentWork[1] = common.BytesToHash(SeedHash(block.NumberU64())).Hex()
s.currentWork[2] = common.BytesToHash(new(big.Int).Div(two256, block.Difficulty()).Bytes()).Hex()
s.currentWork[3] = hexutil.EncodeBig(block.Number())
// Trace the seal work fetched by remote sealer.
s.currentBlock = block
s.works[hash] = block
}
// notifyWork notifies all the specified mining endpoints of the availability of
// new work to be processed.
func (s *remoteSealer) notifyWork() {
work := s.currentWork
// Encode the JSON payload of the notification. When NotifyFull is set,
// this is the complete block header, otherwise it is a JSON array.
var blob []byte
if s.ethash.config.NotifyFull {
blob, _ = json.Marshal(s.currentBlock.Header())
} else {
blob, _ = json.Marshal(work)
}
s.reqWG.Add(len(s.notifyURLs))
for _, url := range s.notifyURLs {
go s.sendNotification(s.notifyCtx, url, blob, work)
}
}
func (s *remoteSealer) sendNotification(ctx context.Context, url string, json []byte, work [4]string) {
defer s.reqWG.Done()
req, err := http.NewRequest(http.MethodPost, url, bytes.NewReader(json))
if err != nil {
s.ethash.config.Log.Warn("Can't create remote miner notification", "err", err)
return
}
ctx, cancel := context.WithTimeout(ctx, remoteSealerTimeout)
defer cancel()
req = req.WithContext(ctx)
req.Header.Set("Content-Type", "application/json")
resp, err := http.DefaultClient.Do(req)
if err != nil {
s.ethash.config.Log.Warn("Failed to notify remote miner", "err", err)
} else {
s.ethash.config.Log.Trace("Notified remote miner", "miner", url, "hash", work[0], "target", work[2])
resp.Body.Close()
}
}
// submitWork verifies the submitted pow solution, returning
// whether the solution was accepted or not (not can be both a bad pow as well as
// any other error, like no pending work or stale mining result).
func (s *remoteSealer) submitWork(nonce types.BlockNonce, mixDigest common.Hash, sealhash common.Hash) bool {
if s.currentBlock == nil {
s.ethash.config.Log.Error("Pending work without block", "sealhash", sealhash)
return false
}
// Make sure the work submitted is present
block := s.works[sealhash]
if block == nil {
s.ethash.config.Log.Warn("Work submitted but none pending", "sealhash", sealhash, "curnumber", s.currentBlock.NumberU64())
return false
}
// Verify the correctness of submitted result.
header := block.Header()
header.Nonce = nonce
header.MixDigest = mixDigest
start := time.Now()
if !s.noverify {
if err := s.ethash.verifySeal(nil, header, true); err != nil {
s.ethash.config.Log.Warn("Invalid proof-of-work submitted", "sealhash", sealhash, "elapsed", common.PrettyDuration(time.Since(start)), "err", err)
return false
}
}
// Make sure the result channel is assigned.
if s.results == nil {
s.ethash.config.Log.Warn("Ethash result channel is empty, submitted mining result is rejected")
return false
}
s.ethash.config.Log.Trace("Verified correct proof-of-work", "sealhash", sealhash, "elapsed", common.PrettyDuration(time.Since(start)))
// Solutions seems to be valid, return to the miner and notify acceptance.
solution := block.WithSeal(header)
// The submitted solution is within the scope of acceptance.
if solution.NumberU64()+staleThreshold > s.currentBlock.NumberU64() {
select {
case s.results <- solution:
s.ethash.config.Log.Debug("Work submitted is acceptable", "number", solution.NumberU64(), "sealhash", sealhash, "hash", solution.Hash())
return true
default:
s.ethash.config.Log.Warn("Sealing result is not read by miner", "mode", "remote", "sealhash", sealhash)
return false
}
}
// The submitted block is too old to accept, drop it.
s.ethash.config.Log.Warn("Work submitted is too old", "number", solution.NumberU64(), "sealhash", sealhash, "hash", solution.Hash())
return false
}