core, consensus: pluggable consensus engines (ethereum#3817)

This commit adds pluggable consensus engines to go-ethereum. In short, it
introduces a generic consensus interface, and refactors the entire codebase to
use this interface.

accounts/abi/bind/backends/simulated.go

@@ -27,14 +27,14 @@ import (
 	"github.com/ethereum/go-ethereum/accounts/abi/bind"
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/common/math"
+	"github.com/ethereum/go-ethereum/consensus/ethash"
 	"github.com/ethereum/go-ethereum/core"
 	"github.com/ethereum/go-ethereum/core/state"
 	"github.com/ethereum/go-ethereum/core/types"
 	"github.com/ethereum/go-ethereum/core/vm"
 	"github.com/ethereum/go-ethereum/ethdb"
 	"github.com/ethereum/go-ethereum/event"
 	"github.com/ethereum/go-ethereum/params"
-	"github.com/ethereum/go-ethereum/pow"
 )
 
 // This nil assignment ensures compile time that SimulatedBackend implements bind.ContractBackend.
@@ -61,7 +61,7 @@ func NewSimulatedBackend(alloc core.GenesisAlloc) *SimulatedBackend {
 	database, _ := ethdb.NewMemDatabase()
 	genesis := core.Genesis{Config: params.AllProtocolChanges, Alloc: alloc}
 	genesis.MustCommit(database)
-	blockchain, _ := core.NewBlockChain(database, genesis.Config, new(pow.FakePow), new(event.TypeMux), vm.Config{})
+	blockchain, _ := core.NewBlockChain(database, genesis.Config, ethash.NewFaker(), new(event.TypeMux), vm.Config{})
 	backend := &SimulatedBackend{database: database, blockchain: blockchain, config: genesis.Config}
 	backend.rollback()
 	return backend

cmd/evm/disasm.go

@@ -20,10 +20,10 @@ import (
 	"errors"
 	"fmt"
 	"io/ioutil"
+	"strings"
 
 	"github.com/ethereum/go-ethereum/core/asm"
 	cli "gopkg.in/urfave/cli.v1"
-	"strings"
 )
 
 var disasmCommand = cli.Command{

cmd/geth/main.go

@@ -303,7 +303,15 @@ func startNode(ctx *cli.Context, stack *node.Node) {
 		if err := stack.Service(&ethereum); err != nil {
 			utils.Fatalf("ethereum service not running: %v", err)
 		}
-		if err := ethereum.StartMining(ctx.GlobalInt(utils.MinerThreadsFlag.Name)); err != nil {
+		if threads := ctx.GlobalInt(utils.MinerThreadsFlag.Name); threads > 0 {
+			type threaded interface {
+				SetThreads(threads int)
+			}
+			if th, ok := ethereum.Engine().(threaded); ok {
+				th.SetThreads(threads)
+			}
+		}
+		if err := ethereum.StartMining(); err != nil {
 			utils.Fatalf("Failed to start mining: %v", err)
 		}
 	}

cmd/geth/misccmd.go

@@ -26,9 +26,9 @@ import (
 	"strings"
 
 	"github.com/ethereum/go-ethereum/cmd/utils"
+	"github.com/ethereum/go-ethereum/consensus/ethash"
 	"github.com/ethereum/go-ethereum/eth"
 	"github.com/ethereum/go-ethereum/params"
-	"github.com/ethereum/go-ethereum/pow"
 	"gopkg.in/urfave/cli.v1"
 )
 
@@ -87,7 +87,7 @@ func makedag(ctx *cli.Context) error {
 				utils.Fatalf("Can't find dir")
 			}
 			fmt.Println("making DAG, this could take awhile...")
-			pow.MakeDataset(blockNum, dir)
+			ethash.MakeDataset(blockNum, dir)
 		}
 	default:
 		wrongArgs()

cmd/utils/flags.go

@@ -32,6 +32,7 @@ import (
 	"github.com/ethereum/go-ethereum/accounts"
 	"github.com/ethereum/go-ethereum/accounts/keystore"
 	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/consensus/ethash"
 	"github.com/ethereum/go-ethereum/core"
 	"github.com/ethereum/go-ethereum/core/state"
 	"github.com/ethereum/go-ethereum/core/vm"
@@ -49,7 +50,6 @@ import (
 	"github.com/ethereum/go-ethereum/p2p/nat"
 	"github.com/ethereum/go-ethereum/p2p/netutil"
 	"github.com/ethereum/go-ethereum/params"
-	"github.com/ethereum/go-ethereum/pow"
 	"github.com/ethereum/go-ethereum/rpc"
 	whisper "github.com/ethereum/go-ethereum/whisper/whisperv2"
 	"gopkg.in/urfave/cli.v1"
@@ -149,7 +149,7 @@ var (
 	}
 	TestNetFlag = cli.BoolFlag{
 		Name:  "testnet",
-		Usage: "Ropsten network: pre-configured test network",
+		Usage: "Ropsten network: pre-configured proof-of-work test network",
 	}
 	DevModeFlag = cli.BoolFlag{
 		Name:  "dev",
@@ -921,16 +921,16 @@ func MakeChain(ctx *cli.Context, stack *node.Node) (chain *core.BlockChain, chai
 	var err error
 	chainDb = MakeChainDatabase(ctx, stack)
 
-	seal := pow.PoW(pow.FakePow{})
+	engine := ethash.NewFaker()
 	if !ctx.GlobalBool(FakePoWFlag.Name) {
-		seal = pow.NewFullEthash("", 1, 0, "", 1, 0)
+		engine = ethash.New("", 1, 0, "", 1, 0)
 	}
 	config, _, err := core.SetupGenesisBlock(chainDb, MakeGenesis(ctx))
 	if err != nil {
 		Fatalf("%v", err)
 	}
 	vmcfg := vm.Config{EnablePreimageRecording: ctx.GlobalBool(VMEnableDebugFlag.Name)}
-	chain, err = core.NewBlockChain(chainDb, config, seal, new(event.TypeMux), vmcfg)
+	chain, err = core.NewBlockChain(chainDb, config, engine, new(event.TypeMux), vmcfg)
 	if err != nil {
 		Fatalf("Can't create BlockChain: %v", err)
 	}

consensus/consensus.go

@@ -0,0 +1,94 @@
+// 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 consensus implements different Ethereum consensus engines.
+package consensus
+
+import (
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/core/state"
+	"github.com/ethereum/go-ethereum/core/types"
+	"github.com/ethereum/go-ethereum/params"
+	"github.com/ethereum/go-ethereum/rpc"
+)
+
+// ChainReader defines a small collection of methods needed to access the local
+// blockchain during header and/or uncle verification.
+type ChainReader interface {
+	// Config retrieves the blockchain's chain configuration.
+	Config() *params.ChainConfig
+
+	// CurrentHeader retrieves the current header from the local chain.
+	CurrentHeader() *types.Header
+
+	// GetHeader retrieves a block header from the database by hash and number.
+	GetHeader(hash common.Hash, number uint64) *types.Header
+
+	// GetHeaderByNumber retrieves a block header from the database by number.
+	GetHeaderByNumber(number uint64) *types.Header
+
+	// GetBlock retrieves a block from the database by hash and number.
+	GetBlock(hash common.Hash, number uint64) *types.Block
+}
+
+// Engine is an algorithm agnostic consensus engine.
+type Engine interface {
+	// 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
+}

pow/ethash_algo.go → consensus/ethash/algorithm.go

@@ -14,7 +14,7 @@
 // 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 pow
+package ethash
 
 import (
 	"encoding/binary"

pow/ethash_algo_go1.7.go → consensus/ethash/algorithm_go1.7.go

@@ -16,7 +16,7 @@
 
 // +build !go1.8
 
-package pow
+package ethash
 
 // cacheSize calculates and returns the size of the ethash verification cache that
 // belongs to a certain block number. The cache size grows linearly, however, we

pow/ethash_algo_go1.8.go → consensus/ethash/algorithm_go1.8.go

@@ -16,7 +16,7 @@
 
 // +build go1.8
 
-package pow
+package ethash
 
 import "math/big"
 

pow/ethash_algo_go1.8_test.go → consensus/ethash/algorithm_go1.8_test.go

@@ -16,7 +16,7 @@
 
 // +build go1.8
 
-package pow
+package ethash
 
 import "testing"
 

pow/ethash_algo_test.go → consensus/ethash/algorithm_test.go

@@ -14,7 +14,7 @@
 // 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 pow
+package ethash
 
 import (
 	"bytes"
@@ -704,26 +704,15 @@ func TestConcurrentDiskCacheGeneration(t *testing.T) {
 		go func(idx int) {
 			defer pend.Done()
 
-			ethash := NewFullEthash(cachedir, 0, 1, "", 0, 0)
-			if err := ethash.Verify(block); err != nil {
+			ethash := New(cachedir, 0, 1, "", 0, 0)
+			if err := ethash.VerifySeal(nil, block.Header()); err != nil {
 				t.Errorf("proc %d: block verification failed: %v", idx, err)
 			}
 		}(i)
 	}
 	pend.Wait()
 }
 
-func TestTestMode(t *testing.T) {
-	head := &types.Header{Difficulty: big.NewInt(100)}
-	ethash := NewTestEthash()
-	nonce, mix := ethash.Search(types.NewBlockWithHeader(head), nil)
-	head.Nonce = types.EncodeNonce(nonce)
-	copy(head.MixDigest[:], mix)
-	if err := ethash.Verify(types.NewBlockWithHeader(head)); err != nil {
-		t.Error("unexpected Verify error:", err)
-	}
-}
-
 // Benchmarks the cache generation performance.
 func BenchmarkCacheGeneration(b *testing.B) {
 	for i := 0; i < b.N; i++ {