Prepare next proposal (#4594)

* prepare next proposal

* address comment

* address comment

Author: envestcc

consensus/consensusfsm/fsm.go

@@ -466,7 +466,6 @@ func (m *ConsensusFSM) onReceiveBlock(evt fsm.Event) (fsm.State, error) {
 		m.ctx.Logger().Debug("Failed to generate proposal endorsement", zap.Error(err))
 		return sAcceptBlockProposal, nil
 	}
-
 	return sAcceptProposalEndorsement, nil
 }
 

consensus/scheme/rolldpos/rolldposctx.go

@@ -13,6 +13,7 @@ import (
 	"github.com/facebookgo/clock"
 	fsm "github.com/iotexproject/go-fsm"
 	"github.com/iotexproject/go-pkgs/crypto"
+	"github.com/iotexproject/go-pkgs/hash"
 	"github.com/pkg/errors"
 	"github.com/prometheus/client_golang/prometheus"
 	"go.uber.org/zap"
@@ -405,6 +406,37 @@ func (ctx *rollDPoSCtx) Proposal() (interface{}, error) {
 	return ctx.mintNewBlock(privateKey)
 }
 
+func (ctx *rollDPoSCtx) prepareNextProposal(prevHeight uint64, prevHash hash.Hash256) error {
+	var (
+		height    = prevHeight + 1
+		interval  = ctx.BlockInterval(height)
+		startTime = ctx.round.StartTime().Add(interval)
+		err       error
+	)
+	fork, err := ctx.chain.Fork(prevHash)
+	if err != nil {
+		return errors.Wrapf(err, "failed to check fork at block %d, hash %x", prevHeight, prevHash[:])
+	}
+	roundCalc := ctx.roundCalc.Fork(fork)
+	// check if the current node is the next proposer
+	nextProposer := roundCalc.Proposer(height, interval, startTime)
+	idx := slices.Index(ctx.encodedAddrs, nextProposer)
+	if idx < 0 {
+		return nil
+	}
+	privateKey := ctx.priKeys[idx]
+	ctx.logger().Debug("prepare next proposal", log.Hex("prevHash", prevHash[:]), zap.Uint64("height", ctx.round.height+1), zap.Time("timestamp", startTime), zap.String("nextproposer", nextProposer))
+	go func() {
+		blk, err := fork.MintNewBlock(startTime, privateKey, prevHash)
+		if err != nil {
+			ctx.logger().Error("failed to mint new block", zap.Error(err))
+			return
+		}
+		ctx.logger().Debug("prepared a new block", zap.Uint64("height", blk.Height()), zap.Time("timestamp", blk.Timestamp()))
+	}()
+	return nil
+}
+
 func (ctx *rollDPoSCtx) WaitUntilRoundStart() time.Duration {
 	ctx.mutex.RLock()
 	defer ctx.mutex.RUnlock()
@@ -454,9 +486,16 @@ func (ctx *rollDPoSCtx) NewProposalEndorsement(msg interface{}) (interface{}, er
 		if err := ctx.round.AddBlock(proposal.block); err != nil {
 			return nil, err
 		}
+		if err := ctx.prepareNextProposal(proposal.block.Height(), blkHash); err != nil {
+			ctx.loggerWithStats().Warn("failed to prepare next proposal", zap.Error(err), zap.Uint64("prevHeight", proposal.block.Height()))
+		}
 		ctx.loggerWithStats().Debug("accept block proposal", log.Hex("block", blockHash))
 	} else if ctx.round.IsLocked() {
 		blockHash = ctx.round.HashOfBlockInLock()
+	} else {
+		if err := ctx.prepareNextProposal(ctx.round.Height()-1, ctx.round.PrevHash()); err != nil {
+			ctx.loggerWithStats().Warn("failed to prepare next proposal", zap.Error(err), zap.Uint64("prevHeight", ctx.round.Height()-1))
+		}
 	}
 	// TODO: prepare next block if the current node will be a proposer