x/bor: add target producer id in producer planned downtime

app/abci.go

@@ -95,12 +95,19 @@ func (app *HeimdallApp) NewPrepareProposalHandler() sdk.PrepareProposalHandler {
 						break
 					}
 				}
-				if _, ok := msg.(*borTypes.MsgSetProducerDowntime); ok {
+				if downtimeMsg, ok := msg.(*borTypes.MsgSetProducerDowntime); ok {
 					if err := app.BorKeeper.CanSetProducerDowntime(sdk.UnwrapSDKContext(ctx)); err != nil {
 						logger.Info("Skipping MsgSetProducerDowntime in PrepareProposal", "error", err)
 						shouldSkip = true
 						break
 					}
+					if downtimeMsg.TargetProducerId != borTypes.RoundRobinDefault {
+						if err := app.BorKeeper.CanUseTargetProducer(sdk.UnwrapSDKContext(ctx)); err != nil {
+							logger.Info("Skipping MsgSetProducerDowntime with TargetProducerId in PrepareProposal", "error", err)
+							shouldSkip = true
+							break
+						}
+					}
 				}
 			}
 
@@ -195,11 +202,17 @@ func (app *HeimdallApp) NewProcessProposalHandler() sdk.ProcessProposalHandler {
 						return &abci.ResponseProcessProposal{Status: abci.ResponseProcessProposal_REJECT}, nil
 					}
 				}
-				if _, ok := msg.(*borTypes.MsgSetProducerDowntime); ok {
+				if downtimeMsg, ok := msg.(*borTypes.MsgSetProducerDowntime); ok {
 					if err := app.BorKeeper.CanSetProducerDowntime(sdk.UnwrapSDKContext(ctx)); err != nil {
 						logger.Error("Rejecting proposal with invalid MsgSetProducerDowntime", "error", err)
 						return &abci.ResponseProcessProposal{Status: abci.ResponseProcessProposal_REJECT}, nil
 					}
+					if downtimeMsg.TargetProducerId != borTypes.RoundRobinDefault {
+						if err := app.BorKeeper.CanUseTargetProducer(sdk.UnwrapSDKContext(ctx)); err != nil {
+							logger.Error("Rejecting proposal with MsgSetProducerDowntime containing TargetProducerId before fork height", "error", err)
+							return &abci.ResponseProcessProposal{Status: abci.ResponseProcessProposal_REJECT}, nil
+						}
+					}
 				}
 			}
 
@@ -794,7 +807,7 @@ func (app *HeimdallApp) checkAndAddFutureSpan(ctx sdk.Context, majorityMilestone
 			return err
 		}
 
-		err = app.BorKeeper.AddNewVeBlopSpan(ctx, currentProducer, lastSpan.EndBlock+1, endBlock, lastSpan.BorChainId, supportingValidatorIDs, uint64(ctx.BlockHeight()))
+		err = app.BorKeeper.AddNewVeBlopSpan(ctx, currentProducer, lastSpan.EndBlock+1, endBlock, lastSpan.BorChainId, supportingValidatorIDs, uint64(ctx.BlockHeight()), borTypes.RoundRobinDefault)
 		if err != nil {
 			logger.Error("Error occurred while adding new veblop span", "error", err)
 			return err
@@ -902,7 +915,7 @@ func (app *HeimdallApp) checkAndRotateCurrentSpan(ctx sdk.Context) error {
 
 		delete(latestActiveProducer, currentProducer)
 
-		err = app.BorKeeper.AddNewVeBlopSpan(addSpanCtx, currentProducer, lastMilestone.EndBlock+1, endBlock, lastMilestone.BorChainId, latestActiveProducer, uint64(ctx.BlockHeight()))
+		err = app.BorKeeper.AddNewVeBlopSpan(addSpanCtx, currentProducer, lastMilestone.EndBlock+1, endBlock, lastMilestone.BorChainId, latestActiveProducer, uint64(ctx.BlockHeight()), borTypes.RoundRobinDefault)
 		if err != nil {
 			logger.Warn("Error occurred while adding new veblop span", "error", err)
 		} else {

app/app.go

@@ -509,7 +509,7 @@ func (app *HeimdallApp) CheckTx(req *abci.RequestCheckTx) (*abci.ResponseCheckTx
 						Log:  err.Error(),
 					}, nil
 				}
-			} else if _, ok := msg.(*borTypes.MsgSetProducerDowntime); ok {
+			} else if downtimeMsg, ok := msg.(*borTypes.MsgSetProducerDowntime); ok {
 				// Create a context for validation
 				ctx := app.NewUncachedContext(true, cmtproto.Header{Height: app.LastBlockHeight() + 1})
 				if err := app.BorKeeper.CanSetProducerDowntime(ctx); err != nil {
@@ -519,6 +519,15 @@ func (app *HeimdallApp) CheckTx(req *abci.RequestCheckTx) (*abci.ResponseCheckTx
 						Log:  err.Error(),
 					}, nil
 				}
+				if downtimeMsg.TargetProducerId != borTypes.RoundRobinDefault {
+					if err := app.BorKeeper.CanUseTargetProducer(ctx); err != nil {
+						app.Logger().Debug("Rejecting MsgSetProducerDowntime with TargetProducerId in CheckTx", "error", err)
+						return &abci.ResponseCheckTx{
+							Code: sdkerrors.ErrInvalidRequest.ABCICode(),
+							Log:  err.Error(),
+						}, nil
+					}
+				}
 			}
 		}
 	}

helper/config.go

@@ -94,7 +94,6 @@ const (
 	DefaultMilestonePollInterval = 30 * time.Second
 
 	// Self-healing defaults
-
 	DefaultEnableSH                = false
 	DefaultSHStateSyncedInterval   = 3 * time.Hour
 	DefaultSHStakeUpdateInterval   = 3 * time.Hour
@@ -238,6 +237,8 @@ var faultyMilestoneNumber int64 = 0
 
 var producerDowntimeHeight int64 = 0
 
+var targetProducerOverrideHeight int64 = 0
+
 type ChainManagerAddressMigration struct {
 	PolTokenAddress       string
 	RootChainAddress      string
@@ -485,6 +486,7 @@ func InitHeimdallConfigWith(homeDir string, heimdallConfigFileFromFlag string) {
 		disableValSetCheckHeight = 25723063
 		initialHeight = 24404501
 		producerDowntimeHeight = 34966593
+		targetProducerOverrideHeight = 0 // TBD
 	case MumbaiChain:
 		milestoneDeletionHeight = 0
 		faultyMilestoneNumber = -1
@@ -494,6 +496,7 @@ func InitHeimdallConfigWith(homeDir string, heimdallConfigFileFromFlag string) {
 		disableValSetCheckHeight = 0
 		initialHeight = 0
 		producerDowntimeHeight = 0
+		targetProducerOverrideHeight = 0 // TBD
 	case AmoyChain:
 		milestoneDeletionHeight = 0
 		faultyMilestoneNumber = -1
@@ -503,6 +506,7 @@ func InitHeimdallConfigWith(homeDir string, heimdallConfigFileFromFlag string) {
 		disableValSetCheckHeight = 10618299
 		initialHeight = 8788501
 		producerDowntimeHeight = 20457139
+		targetProducerOverrideHeight = 0 // TBD
 	default:
 		milestoneDeletionHeight = 0
 		faultyMilestoneNumber = -1
@@ -512,6 +516,7 @@ func InitHeimdallConfigWith(homeDir string, heimdallConfigFileFromFlag string) {
 		disableValSetCheckHeight = 0
 		initialHeight = 0
 		producerDowntimeHeight = 0
+		targetProducerOverrideHeight = 0
 	}
 }
 
@@ -692,6 +697,14 @@ func GetSetProducerDowntimeHeight() int64 {
 	return producerDowntimeHeight
 }
 
+func GetTargetProducerOverrideHeight() int64 {
+	return targetProducerOverrideHeight
+}
+
+func SetTargetProducerOverrideHeight(height int64) {
+	targetProducerOverrideHeight = height
+}
+
 func GetChainManagerAddressMigration(blockNum int64) (ChainManagerAddressMigration, bool) {
 	chainMigration := chainManagerAddressMigrations[conf.Custom.Chain]
 	if chainMigration == nil {

proto/heimdallv2/bor/tx.proto

@@ -109,6 +109,9 @@ message MsgSetProducerDowntime {
   // Block range during which the producer will be offline.
   BlockRange downtime_range = 2
       [ (gogoproto.nullable) = false, (amino.dont_omitempty) = true ];
+  // Validator ID of the preferred producer to replace the downtime producer.
+  // 0 = round-robin (default).
+  uint64 target_producer_id = 3;
 }
 
 // MsgSetProducerDowntimeResponse defines the response for

x/bor/client/cli/flags.go

@@ -9,4 +9,5 @@ const (
 	FlagStartTimestampUTC = "start-timestamp-utc"
 	FlagEndTimestampUTC   = "end-timestamp-utc"
 	FlagCalcOnly          = "calc-only"
+	FlagTargetProducerID  = "target-producer-id"
 )

x/bor/client/cli/tx.go

@@ -207,7 +207,8 @@ func NewProducerDowntimeCmd() *cobra.Command {
 				return nil
 			}
 
-			msg := types.NewMsgSetProducerDowntime(producerAddress, startBlock, endBlock)
+			targetProducerID := viper.GetUint64(FlagTargetProducerID)
+			msg := types.NewMsgSetProducerDowntime(producerAddress, startBlock, endBlock, targetProducerID)
 
 			return cli.BroadcastMsg(clientCtx, producerAddress, msg, logger)
 		},
@@ -217,6 +218,7 @@ func NewProducerDowntimeCmd() *cobra.Command {
 	cmd.Flags().Int(FlagStartTimestampUTC, 0, "--start-timestamp-utc=<start-timestamp-utc>")
 	cmd.Flags().Int(FlagEndTimestampUTC, 0, "--end-timestamp-utc=<end-timestamp-utc>")
 	cmd.Flags().Bool(FlagCalcOnly, false, "--calc-only=<true|false>")
+	cmd.Flags().Uint64(FlagTargetProducerID, 0, "--target-producer-id=<target-producer-id>")
 
 	if err := cmd.MarkFlagRequired(FlagProducerAddress); err != nil {
 		fmt.Printf("NewProducerDowntimeCmd | MarkFlagRequired | FlagProducerAddress Error: %v", err)

x/bor/keeper/keeper.go

@@ -596,14 +596,26 @@ func (k Keeper) CanVoteProducers(ctx context.Context) error {
 	return nil
 }
 
-// CanSetProducerDowntime checks if the current height is after the setProducerDowntimeHeight
+// CanSetProducerDowntime checks if the current height is after the setProducerDowntimeHeight.
 func (k Keeper) CanSetProducerDowntime(ctx sdk.Context) error {
-	if uint64(ctx.BlockHeight()) < uint64(helper.GetSetProducerDowntimeHeight()) {
+	if ctx.BlockHeight() < helper.GetSetProducerDowntimeHeight() {
 		return fmt.Errorf("MsgSetProducerDowntime not allowed: block %d is before the setProducerDowntimeHeight %d",
 			ctx.BlockHeight(),
-			helper.GetSetProducerDowntimeHeight())
+			helper.GetSetProducerDowntimeHeight(),
+		)
 	}
+	return nil
+}
 
+// CanUseTargetProducer checks if the current height is after the targetProducerOverrideHeight,
+// which gates the use of a non-default TargetProducerId in MsgSetProducerDowntime.
+func (k Keeper) CanUseTargetProducer(ctx sdk.Context) error {
+	if ctx.BlockHeight() < helper.GetTargetProducerOverrideHeight() {
+		return fmt.Errorf("MsgSetProducerDowntime with TargetProducerId not allowed: block %d is before the targetProducerOverrideHeight %d",
+			ctx.BlockHeight(),
+			helper.GetTargetProducerOverrideHeight(),
+		)
+	}
 	return nil
 }
 

x/bor/keeper/msg_server.go

@@ -259,7 +259,7 @@
 	return &types.MsgBackfillSpansResponse{}, nil
 }
 
 func (srv msgServer) SetProducerDowntime(ctx context.Context, msg *types.MsgSetProducerDowntime) (*types.MsgSetProducerDowntimeResponse, error) {
 	var err error
 	start := time.Now()
 	defer recordBorTransactionMetric(api.ProducerDowntimeMethod, start, &err)
@@ -325,6 +325,28 @@
 		return nil, fmt.Errorf("producer with address %s and id %d is not in the current producer set", msg.Producer, producerId)
 	}
 
+	// Reject non-default target before the fork height.
+	if msg.TargetProducerId != types.RoundRobinDefault && sdkCtx.BlockHeight() < helper.GetTargetProducerOverrideHeight() {
+		return nil, fmt.Errorf("target producer override is not enabled until height %d", helper.GetTargetProducerOverrideHeight())
+	}
+
+	// Validate target producer if it is not the round-robin default and the block height is greater than the target producer override height.
+	if msg.TargetProducerId != types.RoundRobinDefault && sdkCtx.BlockHeight() >= helper.GetTargetProducerOverrideHeight() {
+		if msg.TargetProducerId == producerId {
+			return nil, fmt.Errorf("target producer cannot be the same as the current producer")
+		}
+		targetInCandidates := false
+		for _, c := range candidates {
+			if c == msg.TargetProducerId {
+				targetInCandidates = true
+				break
+			}
+		}
+		if !targetInCandidates {
+			return nil, fmt.Errorf("target producer id %d is not in the current producer set", msg.TargetProducerId)
+		}
+	}
+
 	return &types.MsgSetProducerDowntimeResponse{}, nil
 }
 

x/bor/keeper/msg_server_test.go

@@ -483,7 +483,6 @@ func (s *KeeperTestSuite) TestBackfillSpans() {
 		{
 			name: "mismatch between calculated and provided last span id",
 			backfillSpans: types.MsgBackfillSpans{
-
 				Proposer:        common.HexToAddress("someProposer").String(),
 				ChainId:         testChainParams.ChainParams.BorChainId,
 				LatestSpanId:    1,
@@ -699,7 +698,87 @@ func (s *KeeperTestSuite) TestSetProducerDowntime() {
 			seedVotes:  []uint64{id1, id2},
 			msg:        newMsg(val1.hexAddr, 600, 600+maxRange),
 		},
+		{
+			name:       "success - target zero accepted (round-robin default)",
+			validators: []staketypes.Validator{{ValId: val1.id, Signer: val1.hexAddr}, {ValId: val2.id, Signer: val2.hexAddr}},
+			seedVotes:  []uint64{id1, id2, id3},
+			msg: &types.MsgSetProducerDowntime{
+				Producer:         val1.hexAddr,
+				DowntimeRange:    types.BlockRange{StartBlock: 100, EndBlock: 100 + minRange},
+				TargetProducerId: types.RoundRobinDefault,
+			},
+		},
+		{
+			name:       "success - valid target in producer set",
+			validators: []staketypes.Validator{{ValId: val1.id, Signer: val1.hexAddr}, {ValId: val2.id, Signer: val2.hexAddr}, {ValId: val3.id, Signer: val3.hexAddr}},
+			seedVotes:  []uint64{id1, id2, id3},
+			msg: &types.MsgSetProducerDowntime{
+				Producer:         val1.hexAddr,
+				DowntimeRange:    types.BlockRange{StartBlock: 100, EndBlock: 100 + minRange},
+				TargetProducerId: id2,
+			},
+		},
+		{
+			name:       "error - target is the current producer",
+			validators: []staketypes.Validator{{ValId: val1.id, Signer: val1.hexAddr}, {ValId: val2.id, Signer: val2.hexAddr}},
+			seedVotes:  []uint64{id1, id2, id3},
+			msg: &types.MsgSetProducerDowntime{
+				Producer:         val1.hexAddr,
+				DowntimeRange:    types.BlockRange{StartBlock: 100, EndBlock: 100 + minRange},
+				TargetProducerId: id1,
+			},
+			expectErrSubstr: "target producer cannot be the same as the current producer",
+		},
+		{
+			name:       "error - target not in producer set",
+			validators: []staketypes.Validator{{ValId: val1.id, Signer: val1.hexAddr}, {ValId: val2.id, Signer: val2.hexAddr}, {ValId: val3.id, Signer: val3.hexAddr}},
+			seedVotes:  []uint64{id1, id2}, // only id1 and id2 qualify; id3 does not
+			msg: &types.MsgSetProducerDowntime{
+				Producer:         val1.hexAddr,
+				DowntimeRange:    types.BlockRange{StartBlock: 100, EndBlock: 100 + minRange},
+				TargetProducerId: id3,
+			},
+			expectErrSubstr: "target producer id 3 is not in the current producer set",
+		},
+		{
+			name:       "error - target is non-existent validator",
+			validators: []staketypes.Validator{{ValId: val1.id, Signer: val1.hexAddr}, {ValId: val2.id, Signer: val2.hexAddr}},
+			seedVotes:  []uint64{id1, id2, id3},
+			msg: &types.MsgSetProducerDowntime{
+				Producer:         val1.hexAddr,
+				DowntimeRange:    types.BlockRange{StartBlock: 100, EndBlock: 100 + minRange},
+				TargetProducerId: 999,
+			},
+			expectErrSubstr: "target producer id 999 is not in the current producer set",
+		},
+	}
+
+	// Pre-fork rejection: when targetProducerOverrideHeight is set high,
+	// non-zero target should be rejected.
+	preForkTests := []testCase{
+		{
+			name:       "error - target rejected before fork height",
+			validators: []staketypes.Validator{{ValId: val1.id, Signer: val1.hexAddr}, {ValId: val2.id, Signer: val2.hexAddr}, {ValId: val3.id, Signer: val3.hexAddr}},
+			seedVotes:  []uint64{id1, id2, id3},
+			msg: &types.MsgSetProducerDowntime{
+				Producer:         val1.hexAddr,
+				DowntimeRange:    types.BlockRange{StartBlock: 100, EndBlock: 100 + minRange},
+				TargetProducerId: id2,
+			},
+			expectErrSubstr: "target producer override is not enabled until height",
+		},
+		{
+			name:       "success - round-robin default accepted before fork height",
+			validators: []staketypes.Validator{{ValId: val1.id, Signer: val1.hexAddr}, {ValId: val2.id, Signer: val2.hexAddr}},
+			seedVotes:  []uint64{id1, id2, id3},
+			msg: &types.MsgSetProducerDowntime{
+				Producer:         val1.hexAddr,
+				DowntimeRange:    types.BlockRange{StartBlock: 100, EndBlock: 100 + minRange},
+				TargetProducerId: types.RoundRobinDefault,
+			},
+		},
 	}
+	tests = append(tests, preForkTests...)
 
 	for _, tc := range tests {
 		s.T().Run(tc.name, func(t *testing.T) {
@@ -708,6 +787,19 @@ func (s *KeeperTestSuite) TestSetProducerDowntime() {
 			ctx := s.ctx
 			msgServer := s.msgServer
 
+			// Set fork height high for pre-fork tests, restore after.
+			isPreFork := false
+			for _, pf := range preForkTests {
+				if pf.name == tc.name {
+					isPreFork = true
+					break
+				}
+			}
+			if isPreFork {
+				helper.SetTargetProducerOverrideHeight(999999)
+				defer helper.SetTargetProducerOverrideHeight(0)
+			}
+
 			// Prime mocks and seed producer votes controlling the producer set
 			primeStakeMocks(tc.validators)
 			setVotesForAll(tc.seedVotes)