path: root/consensus/ethash/sealer.go

// 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/ava-labs/coreth/consensus"
	"github.com/ava-labs/coreth/core/types"
	"github.com/ethereum/go-ethereum/common"
	"github.com/ethereum/go-ethereum/common/hexutil"
)

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
	)
	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 new(big.Int).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,