core, consensus: pluggable consensus engines (#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.

4 files changed, 27 insertions, 63 deletions

diff --git a/light/lightchain.go b/light/lightchain.go
index 98fb024f0..4073e39e5 100644
--- a/light/lightchain.go
+++ b/light/lightchain.go
@@ -24,13 +24,13 @@ import (
 	"time"
 
 	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/consensus"
 	"github.com/ethereum/go-ethereum/core"
 	"github.com/ethereum/go-ethereum/core/types"
 	"github.com/ethereum/go-ethereum/ethdb"
 	"github.com/ethereum/go-ethereum/event"
 	"github.com/ethereum/go-ethereum/log"
 	"github.com/ethereum/go-ethereum/params"
-	"github.com/ethereum/go-ethereum/pow"
 	"github.com/ethereum/go-ethereum/rlp"
 	"github.com/hashicorp/golang-lru"
 )
@@ -64,14 +64,13 @@ type LightChain struct {
 	procInterrupt int32 // interrupt signaler for block processing
 	wg            sync.WaitGroup
 
-	pow       pow.PoW
-	validator core.HeaderValidator
+	engine consensus.Engine
 }
 
 // NewLightChain returns a fully initialised light chain using information
 // available in the database. It initialises the default Ethereum header
 // validator.
-func NewLightChain(odr OdrBackend, config *params.ChainConfig, pow pow.PoW, mux *event.TypeMux) (*LightChain, error) {
+func NewLightChain(odr OdrBackend, config *params.ChainConfig, engine consensus.Engine, mux *event.TypeMux) (*LightChain, error) {
 	bodyCache, _ := lru.New(bodyCacheLimit)
 	bodyRLPCache, _ := lru.New(bodyCacheLimit)
 	blockCache, _ := lru.New(blockCacheLimit)
@@ -84,21 +83,17 @@ func NewLightChain(odr OdrBackend, config *params.ChainConfig, pow pow.PoW, mux
 		bodyCache:    bodyCache,
 		bodyRLPCache: bodyRLPCache,
 		blockCache:   blockCache,
-		pow:          pow,
+		engine:       engine,
 	}
-
 	var err error
-	bc.hc, err = core.NewHeaderChain(odr.Database(), config, bc.Validator, bc.getProcInterrupt)
-	bc.SetValidator(core.NewHeaderValidator(config, bc.hc, pow))
+	bc.hc, err = core.NewHeaderChain(odr.Database(), config, bc.engine, bc.getProcInterrupt)
 	if err != nil {
 		return nil, err
 	}
-
 	bc.genesisBlock, _ = bc.GetBlockByNumber(NoOdr, 0)
 	if bc.genesisBlock == nil {
 		return nil, core.ErrNoGenesis
 	}
-
 	if bc.genesisBlock.Hash() == params.MainNetGenesisHash {
 		// add trusted CHT
 		WriteTrustedCht(bc.chainDb, TrustedCht{Number: 805, Root: common.HexToHash("85e4286fe0a730390245c49de8476977afdae0eb5530b277f62a52b12313d50f")})
@@ -145,9 +140,6 @@ func (self *LightChain) loadLastState() error {
 	headerTd := self.GetTd(header.Hash(), header.Number.Uint64())
 	log.Info("Loaded most recent local header", "number", header.Number, "hash", header.Hash(), "td", headerTd)
 
-	// Try to be smart and issue a pow verification for the head to pre-generate caches
-	go self.pow.Verify(types.NewBlockWithHeader(header))
-
 	return nil
 }
 
@@ -188,20 +180,6 @@ func (self *LightChain) Status() (td *big.Int, currentBlock common.Hash, genesis
 	return self.GetTd(hash, header.Number.Uint64()), hash, self.genesisBlock.Hash()
 }
 
-// SetValidator sets the validator which is used to validate incoming headers.
-func (self *LightChain) SetValidator(validator core.HeaderValidator) {
-	self.procmu.Lock()
-	defer self.procmu.Unlock()
-	self.validator = validator
-}
-
-// Validator returns the current header validator.
-func (self *LightChain) Validator() core.HeaderValidator {
-	self.procmu.RLock()
-	defer self.procmu.RUnlock()
-	return self.validator
-}
-
 // State returns a new mutable state based on the current HEAD block.
 func (self *LightChain) State() *LightState {
 	return NewLightState(StateTrieID(self.hc.CurrentHeader()), self.odr)
diff --git a/light/lightchain_test.go b/light/lightchain_test.go
index e9236f1fd..41010cf57 100644
--- a/light/lightchain_test.go
+++ b/light/lightchain_test.go
@@ -23,12 +23,12 @@ import (
 	"testing"
 
 	"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/types"
 	"github.com/ethereum/go-ethereum/ethdb"
 	"github.com/ethereum/go-ethereum/event"
 	"github.com/ethereum/go-ethereum/params"
-	"github.com/ethereum/go-ethereum/pow"
 )
 
 // So we can deterministically seed different blockchains
@@ -49,18 +49,15 @@ func makeHeaderChain(parent *types.Header, n int, db ethdb.Database, seed int) [
 	return headers
 }
 
-func testChainConfig() *params.ChainConfig {
-	return &params.ChainConfig{HomesteadBlock: big.NewInt(0)}
-}
-
 // newCanonical creates a chain database, and injects a deterministic canonical
 // chain. Depending on the full flag, if creates either a full block chain or a
 // header only chain.
 func newCanonical(n int) (ethdb.Database, *LightChain, error) {
 	db, _ := ethdb.NewMemDatabase()
-	gspec := core.Genesis{Config: testChainConfig()}
+	gspec := core.Genesis{Config: params.TestChainConfig}
 	genesis := gspec.MustCommit(db)
-	blockchain, _ := NewLightChain(&dummyOdr{db: db}, gspec.Config, pow.FakePow{}, new(event.TypeMux))
+	blockchain, _ := NewLightChain(&dummyOdr{db: db}, gspec.Config, ethash.NewFaker(), new(event.TypeMux))
+
 	// Create and inject the requested chain
 	if n == 0 {
 		return db, blockchain, nil
@@ -76,14 +73,13 @@ func newTestLightChain() *LightChain {
 	db, _ := ethdb.NewMemDatabase()
 	gspec := &core.Genesis{
 		Difficulty: big.NewInt(1),
-		Config:     testChainConfig(),
+		Config:     params.TestChainConfig,
 	}
 	gspec.MustCommit(db)
-	lc, err := NewLightChain(&dummyOdr{db: db}, gspec.Config, pow.NewTestEthash(), new(event.TypeMux))
+	lc, err := NewLightChain(&dummyOdr{db: db}, gspec.Config, ethash.NewFullFaker(), new(event.TypeMux))
 	if err != nil {
 		panic(err)
 	}
-	lc.SetValidator(bproc{})
 	return lc
 }
 
@@ -130,17 +126,17 @@ func printChain(bc *LightChain) {
 
 // testHeaderChainImport tries to process a chain of header, writing them into
 // the database if successful.
-func testHeaderChainImport(chain []*types.Header, LightChain *LightChain) error {
+func testHeaderChainImport(chain []*types.Header, lightchain *LightChain) error {
 	for _, header := range chain {
 		// Try and validate the header
-		if err := LightChain.Validator().ValidateHeader(header, LightChain.GetHeaderByHash(header.ParentHash), false); err != nil {
+		if err := lightchain.engine.VerifyHeader(lightchain.hc, header, true); err != nil {
 			return err
 		}
 		// Manually insert the header into the database, but don't reorganize (allows subsequent testing)
-		LightChain.mu.Lock()
-		core.WriteTd(LightChain.chainDb, header.Hash(), header.Number.Uint64(), new(big.Int).Add(header.Difficulty, LightChain.GetTdByHash(header.ParentHash)))
-		core.WriteHeader(LightChain.chainDb, header)
-		LightChain.mu.Unlock()
+		lightchain.mu.Lock()
+		core.WriteTd(lightchain.chainDb, header.Hash(), header.Number.Uint64(), new(big.Int).Add(header.Difficulty, lightchain.GetTdByHash(header.ParentHash)))
+		core.WriteHeader(lightchain.chainDb, header)
+		lightchain.mu.Unlock()
 	}
 	return nil
 }
@@ -257,10 +253,6 @@ func TestBrokenHeaderChain(t *testing.T) {
 	}
 }
 
-type bproc struct{}
-
-func (bproc) ValidateHeader(*types.Header, *types.Header, bool) error { return nil }
-
 func makeHeaderChainWithDiff(genesis *types.Block, d []int, seed byte) []*types.Header {
 	var chain []*types.Header
 	for i, difficulty := range d {
@@ -359,7 +351,7 @@ func TestReorgBadHeaderHashes(t *testing.T) {
 	defer func() { delete(core.BadHashes, headers[3].Hash()) }()
 
 	// Create a new LightChain and check that it rolled back the state.
-	ncm, err := NewLightChain(&dummyOdr{db: bc.chainDb}, testChainConfig(), pow.FakePow{}, new(event.TypeMux))
+	ncm, err := NewLightChain(&dummyOdr{db: bc.chainDb}, params.TestChainConfig, ethash.NewFaker(), new(event.TypeMux))
 	if err != nil {
 		t.Fatalf("failed to create new chain manager: %v", err)
 	}
diff --git a/light/odr_test.go b/light/odr_test.go
index 37d999994..ca33db246 100644
--- a/light/odr_test.go
+++ b/light/odr_test.go
@@ -26,6 +26,7 @@ import (
 
 	"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"
@@ -34,7 +35,6 @@ import (
 	"github.com/ethereum/go-ethereum/ethdb"
 	"github.com/ethereum/go-ethereum/event"
 	"github.com/ethereum/go-ethereum/params"
-	"github.com/ethereum/go-ethereum/pow"
 	"github.com/ethereum/go-ethereum/rlp"
 	"github.com/ethereum/go-ethereum/trie"
 )
@@ -248,7 +248,6 @@ func testChainGen(i int, block *core.BlockGen) {
 func testChainOdr(t *testing.T, protocol int, expFail uint64, fn odrTestFn) {
 	var (
 		evmux   = new(event.TypeMux)
-		pow     = new(pow.FakePow)
 		sdb, _  = ethdb.NewMemDatabase()
 		ldb, _  = ethdb.NewMemDatabase()
 		gspec   = core.Genesis{Alloc: core.GenesisAlloc{testBankAddress: {Balance: testBankFunds}}}
@@ -256,16 +255,14 @@ func testChainOdr(t *testing.T, protocol int, expFail uint64, fn odrTestFn) {
 	)
 	gspec.MustCommit(ldb)
 	// Assemble the test environment
-	blockchain, _ := core.NewBlockChain(sdb, testChainConfig(), pow, evmux, vm.Config{})
-	chainConfig := &params.ChainConfig{HomesteadBlock: new(big.Int)}
-	gchain, _ := core.GenerateChain(chainConfig, genesis, sdb, 4, testChainGen)
+	blockchain, _ := core.NewBlockChain(sdb, params.TestChainConfig, ethash.NewFullFaker(), evmux, vm.Config{})
+	gchain, _ := core.GenerateChain(params.TestChainConfig, genesis, sdb, 4, testChainGen)
 	if _, err := blockchain.InsertChain(gchain); err != nil {
 		panic(err)
 	}
 
 	odr := &testOdr{sdb: sdb, ldb: ldb}
-	lightchain, _ := NewLightChain(odr, testChainConfig(), pow, evmux)
-	lightchain.SetValidator(bproc{})
+	lightchain, _ := NewLightChain(odr, params.TestChainConfig, ethash.NewFullFaker(), evmux)
 	headers := make([]*types.Header, len(gchain))
 	for i, block := range gchain {
 		headers[i] = block.Header()
diff --git a/light/txpool_test.go b/light/txpool_test.go
index 2b5fa7116..f23832a41 100644
--- a/light/txpool_test.go
+++ b/light/txpool_test.go
@@ -24,13 +24,13 @@ import (
 	"time"
 
 	"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/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"
 )
 
 type testTxRelay struct {
@@ -83,7 +83,6 @@ func TestTxPool(t *testing.T) {
 
 	var (
 		evmux   = new(event.TypeMux)
-		pow     = new(pow.FakePow)
 		sdb, _  = ethdb.NewMemDatabase()
 		ldb, _  = ethdb.NewMemDatabase()
 		gspec   = core.Genesis{Alloc: core.GenesisAlloc{testBankAddress: {Balance: testBankFunds}}}
@@ -91,9 +90,8 @@ func TestTxPool(t *testing.T) {
 	)
 	gspec.MustCommit(ldb)
 	// Assemble the test environment
-	blockchain, _ := core.NewBlockChain(sdb, testChainConfig(), pow, evmux, vm.Config{})
-	chainConfig := &params.ChainConfig{HomesteadBlock: new(big.Int)}
-	gchain, _ := core.GenerateChain(chainConfig, genesis, sdb, poolTestBlocks, txPoolTestChainGen)
+	blockchain, _ := core.NewBlockChain(sdb, params.TestChainConfig, ethash.NewFullFaker(), evmux, vm.Config{})
+	gchain, _ := core.GenerateChain(params.TestChainConfig, genesis, sdb, poolTestBlocks, txPoolTestChainGen)
 	if _, err := blockchain.InsertChain(gchain); err != nil {
 		panic(err)
 	}
@@ -104,10 +102,9 @@ func TestTxPool(t *testing.T) {
 		discard: make(chan int, 1),
 		mined:   make(chan int, 1),
 	}
-	lightchain, _ := NewLightChain(odr, testChainConfig(), pow, evmux)
-	lightchain.SetValidator(bproc{})
+	lightchain, _ := NewLightChain(odr, params.TestChainConfig, ethash.NewFullFaker(), evmux)
 	txPermanent = 50
-	pool := NewTxPool(testChainConfig(), evmux, lightchain, relay)
+	pool := NewTxPool(params.TestChainConfig, evmux, lightchain, relay)
 	ctx, cancel := context.WithTimeout(context.Background(), 1*time.Second)
 	defer cancel()