enforce backoff time for out-turn validator

consensus/parlia/parlia.go

@@ -48,8 +48,8 @@ const (
 	extraSeal   = 65 // Fixed number of extra-data suffix bytes reserved for signer seal
 
 	validatorBytesLength = common.AddressLength
-	wiggleTime           = 500 * time.Millisecond // Random delay (per signer) to allow concurrent signers
-	fixedBackOffTime     = 200 * time.Millisecond
+	wiggleTime           = uint64(1) // second, Random delay (per signer) to allow concurrent signers
+	initialBackOffTime   = uint64(1) // second
 
 	systemRewardPercent = 4 // it means 1/2^4 = 1/16 percentage of gas fee incoming will be distributed to system
 
@@ -81,7 +81,7 @@ var (
 		common.HexToAddress(GovHubContract):             true,
 		common.HexToAddress(TokenHubContract):           true,
 		common.HexToAddress(RelayerIncentivizeContract): true,
-		common.HexToAddress(CrossChainContract): true,
+		common.HexToAddress(CrossChainContract):         true,
 	}
 )
 
@@ -395,6 +395,15 @@ func (p *Parlia) verifyCascadingFields(chain consensus.ChainReader, header *type
 		return consensus.ErrUnknownAncestor
 	}
 
+	snap, err := p.snapshot(chain, number-1, header.ParentHash, parents)
+	if err != nil {
+		return err
+	}
+
+	if header.Time < parent.Time+p.config.Period+backOffTime(snap, header.Coinbase) {
+		return consensus.ErrFutureBlock
+	}
+
 	// Verify that the gas limit is <= 2^63-1
 	cap := uint64(0x7fffffffffffffff)
 	if header.GasLimit > cap {
@@ -570,7 +579,7 @@ func (p *Parlia) verifySeal(chain consensus.ChainReader, header *types.Header, p
 
 	// Ensure that the difficulty corresponds to the turn-ness of the signer
 	if !p.fakeDiff {
-		inturn := snap.inturn(header.Number.Uint64(), signer)
+		inturn := snap.inturn(signer)
 		if inturn && header.Difficulty.Cmp(diffInTurn) != 0 {
 			return errWrongDifficulty
 		}
@@ -626,8 +635,7 @@ func (p *Parlia) Prepare(chain consensus.ChainReader, header *types.Header) erro
 	if parent == nil {
 		return consensus.ErrUnknownAncestor
 	}
-
-	header.Time = parent.Time + p.config.Period
+	header.Time = parent.Time + p.config.Period + backOffTime(snap, p.val)
 	if header.Time < uint64(time.Now().Unix()) {
 		header.Time = uint64(time.Now().Unix())
 	}
@@ -810,13 +818,6 @@ func (p *Parlia) Seal(chain consensus.ChainReader, block *types.Block, results c
 
 	// Sweet, the protocol permits us to sign the block, wait for our time
 	delay := time.Unix(int64(header.Time), 0).Sub(time.Now()) // nolint: gosimple
-	if header.Difficulty.Cmp(diffNoTurn) == 0 {
-		// It's not our turn explicitly to sign, delay it a bit
-		wiggle := time.Duration(len(snap.Validators)/2+1) * wiggleTime
-		delay += time.Duration(fixedBackOffTime) + time.Duration(rand.Int63n(int64(wiggle)))
-
-		log.Trace("Out-of-turn signing requested", "wiggle", common.PrettyDuration(wiggle))
-	}
 
 	log.Info("Sealing block with", "number", number, "delay", delay, "headerDifficulty", header.Difficulty, "val", val.Hex())
 
@@ -861,7 +862,7 @@ func (p *Parlia) CalcDifficulty(chain consensus.ChainReader, time uint64, parent
 // that a new block should have based on the previous blocks in the chain and the
 // current signer.
 func CalcDifficulty(snap *Snapshot, signer common.Address) *big.Int {
-	if snap.inturn(snap.Number+1, signer) {
+	if snap.inturn(signer) {
 		return new(big.Int).Set(diffInTurn)
 	}
 	return new(big.Int).Set(diffNoTurn)
@@ -1140,6 +1141,26 @@ func encodeSigHeader(w io.Writer, header *types.Header, chainId *big.Int) {
 	}
 }
 
+func backOffTime(snap *Snapshot, val common.Address) uint64 {
+	if snap.inturn(val) {
+		return 0
+	} else {
+		dis := snap.distanceToInTurn(val)
+		s := rand.NewSource(int64(snap.Number))
+		r := rand.New(s)
+		n := len(snap.Validators)
+		backOffSteps := make([]uint64, 0, n)
+		for idx := uint64(0); idx < uint64(n); idx++ {
+			backOffSteps = append(backOffSteps, idx)
+		}
+		r.Shuffle(n, func(i, j int) {
+			backOffSteps[i], backOffSteps[j] = backOffSteps[j], backOffSteps[i]
+		})
+		delay := initialBackOffTime + backOffSteps[dis]*wiggleTime
+		return delay
+	}
+}
+
 // chain context
 type chainContext struct {
 	Chain  consensus.ChainReader
@@ -1194,4 +1215,3 @@ func applyMessage(
 	}
 	return msg.Gas() - returnGas, err
 }
-

consensus/parlia/parlia_test.go

@@ -4,7 +4,6 @@ import (
 	"fmt"
 	"math/rand"
 	"testing"
-	"time"
 
 	"github.com/ethereum/go-ethereum/common"
 )
@@ -57,7 +56,7 @@ func simulateValidatorOutOfService(totalValidators int, downValidators int) {
 		return validators[idx]
 	}
 
-	downDelay := time.Duration(0)
+	downDelay := uint64(0)
 	for h := 1; h <= downBlocks; h++ {
 		if limit := uint64(totalValidators/2 + 1); uint64(h) >= limit {
 			delete(recents, uint64(h)-limit)
@@ -73,21 +72,21 @@ func simulateValidatorOutOfService(totalValidators int, downValidators int) {
 			if len(candidates) == 0 {
 				panic("can not test such case")
 			}
-			idx, delay := producerBlockDelay(candidates, totalValidators)
+			idx, delay := producerBlockDelay(candidates, h, totalValidators)
 			downDelay = downDelay + delay
 			recents[uint64(h)] = idx
 		} else {
 			recents[uint64(h)] = proposer
 		}
 	}
 	fmt.Printf("average delay is %v  when there is %d validators and %d is down \n",
-		downDelay/time.Duration(downBlocks), totalValidators, downValidators)
+		downDelay/uint64(downBlocks), totalValidators, downValidators)
 
 	for i := 0; i < downValidators; i++ {
 		validators[down[i]] = true
 	}
 
-	recoverDelay := time.Duration(0)
+	recoverDelay := uint64(0)
 	lastseen := downBlocks
 	for h := downBlocks + 1; h <= downBlocks+recoverBlocks; h++ {
 		if limit := uint64(totalValidators/2 + 1); uint64(h) >= limit {
@@ -105,7 +104,7 @@ func simulateValidatorOutOfService(totalValidators int, downValidators int) {
 			if len(candidates) == 0 {
 				panic("can not test such case")
 			}
-			idx, delay := producerBlockDelay(candidates, totalValidators)
+			idx, delay := producerBlockDelay(candidates, h, totalValidators)
 			recoverDelay = recoverDelay + delay
 			recents[uint64(h)] = idx
 		} else {
@@ -116,18 +115,28 @@ func simulateValidatorOutOfService(totalValidators int, downValidators int) {
 		recoverDelay, downValidators, lastseen)
 }
 
-func producerBlockDelay(candidates map[int]bool, numOfValidators int) (int, time.Duration) {
-	minDur := time.Duration(0)
-	minIdx := 0
-	wiggle := time.Duration(numOfValidators/2+1) * wiggleTime
-	for idx := range candidates {
-		sleepTime := rand.Int63n(int64(wiggle))
-		if int64(minDur) < sleepTime {
-			minDur = time.Duration(rand.Int63n(int64(wiggle)))
-			minIdx = idx
+func producerBlockDelay(candidates map[int]bool, height, numOfValidators int) (int, uint64) {
+
+	s := rand.NewSource(int64(height))
+	r := rand.New(s)
+	n := numOfValidators
+	backOffSteps := make([]int, 0, n)
+	for idx := 0; idx < n; idx++ {
+		backOffSteps = append(backOffSteps, idx)
+	}
+	r.Shuffle(n, func(i, j int) {
+		backOffSteps[i], backOffSteps[j] = backOffSteps[j], backOffSteps[i]
+	})
+	minDelay := numOfValidators
+	minCandidate := 0
+	for c := range candidates {
+		if minDelay > backOffSteps[c] {
+			minDelay = backOffSteps[c]
+			minCandidate = c
 		}
 	}
-	return minIdx, minDur
+	delay := initialBackOffTime + uint64(minDelay)*wiggleTime
+	return minCandidate, delay
 }
 
 func randomAddress() common.Address {

consensus/parlia/snapshot.go

@@ -210,12 +210,26 @@ func (s *Snapshot) validators() []common.Address {
 }
 
 // inturn returns if a validator at a given block height is in-turn or not.
-func (s *Snapshot) inturn(number uint64, validator common.Address) bool {
+func (s *Snapshot) inturn(validator common.Address) bool {
 	validators := s.validators()
-	offset := number % uint64(len(validators))
+	offset := (s.Number + 1) % uint64(len(validators))
 	return validators[offset] == validator
 }
 
+func (s *Snapshot) distanceToInTurn(validator common.Address) uint64 {
+	validators := s.validators()
+	offset := (s.Number + 1) % uint64(len(validators))
+	idx := uint64(0)
+	for idx < uint64(len(validator)) && validators[idx] != validator {
+		idx++
+	}
+	if offset > idx {
+		return uint64(len(validators)) + idx - offset
+	} else {
+		return idx - offset
+	}
+}
+
 func (s *Snapshot) supposeValidator() common.Address {
 	validators := s.validators()
 	index := (s.Number + 1) % uint64(len(validators))