1 files changed, 302 insertions, 0 deletions
diff --git a/core/utils/round-event.go b/core/utils/round-event.go
new file mode 100644
index 0000000..bab1d32
--- /dev/null
+++ b/core/utils/round-event.go
@@ -0,0 +1,302 @@
+// Copyright 2019 The dexon-consensus Authors
+// This file is part of the dexon-consensus library.
+//
+// The dexon-consensus 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 dexon-consensus 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 dexon-consensus library. If not, see
+// <http://www.gnu.org/licenses/>.
+
+package utils
+
+import (
+	"context"
+	"fmt"
+	"sync"
+	"time"
+
+	"github.com/dexon-foundation/dexon-consensus/common"
+	"github.com/dexon-foundation/dexon-consensus/core/types"
+	typesDKG "github.com/dexon-foundation/dexon-consensus/core/types/dkg"
+)
+
+// ErrUnmatchedBlockHeightWithGov is for invalid parameters for NewRoundEvent.
+type ErrUnmatchedBlockHeightWithGov struct {
+	round       uint64
+	reset       uint64
+	blockHeight uint64
+}
+
+func (e ErrUnmatchedBlockHeightWithGov) Error() string {
+	return fmt.Sprintf("unsynced block height and gov: round:%d reset:%d h:%d",
+		e.round, e.reset, e.blockHeight)
+}
+
+// RoundEventParam defines the parameters passed to event handlers of
+// RoundEvent.
+type RoundEventParam struct {
+	// 'Round' of next checkpoint, might be identical to previous checkpoint.
+	Round uint64
+	// the count of reset DKG for 'Round+1'.
+	Reset uint64
+	// the begin block height of this event, the end block height of this event
+	// would be BeginHeight + config.RoundLength.
+	BeginHeight uint64
+	// The configuration for 'Round'.
+	Config *types.Config
+	// The CRS for 'Round'.
+	CRS common.Hash
+}
+
+// NextRoundCheckpoint returns the height to check if the next round is ready.
+func (e RoundEventParam) NextRoundCheckpoint() uint64 {
+	return e.BeginHeight + e.Config.RoundLength*8/10
+}
+
+// roundEventFn defines the fingerprint of handlers of round events.
+type roundEventFn func([]RoundEventParam)
+
+// governanceAccessor is a subset of core.Governance to break the dependency
+// between core and utils package.
+type governanceAccessor interface {
+	// Configuration returns the configuration at a given round.
+	// Return the genesis configuration if round == 0.
+	Configuration(round uint64) *types.Config
+
+	// CRS returns the CRS for a given round.
+	// Return the genesis CRS if round == 0.
+	CRS(round uint64) common.Hash
+
+	// DKGComplaints gets all the DKGComplaints of round.
+	DKGComplaints(round uint64) []*typesDKG.Complaint
+
+	// DKGMasterPublicKeys gets all the DKGMasterPublicKey of round.
+	DKGMasterPublicKeys(round uint64) []*typesDKG.MasterPublicKey
+
+	// IsDKGFinal checks if DKG is final.
+	IsDKGFinal(round uint64) bool
+
+	// DKGResetCount returns the reset count for DKG of given round.
+	DKGResetCount(round uint64) uint64
+}
+
+// RoundEvent would be triggered when either:
+// - the next DKG set setup is ready.
+// - the next DKG set setup is failed, and previous DKG set already reset the
+//   CRS.
+type RoundEvent struct {
+	gov                     governanceAccessor
+	logger                  common.Logger
+	lock                    sync.Mutex
+	handlers                []roundEventFn
+	config                  RoundBasedConfig
+	lastTriggeredRound      uint64
+	lastTriggeredResetCount uint64
+	roundShift              uint64
+	ctx                     context.Context
+	ctxCancel               context.CancelFunc
+}
+
+// NewRoundEvent creates an RoundEvent instance.
+func NewRoundEvent(parentCtx context.Context, gov governanceAccessor,
+	logger common.Logger, initRound uint64,
+	initRoundBeginHeight, initBlockHeight uint64,
+	roundShift uint64) (*RoundEvent, error) {
+	// We need to generate valid ending block height of this round (taken
+	// DKG reset count into consideration).
+	e := &RoundEvent{
+		gov:                gov,
+		logger:             logger,
+		lastTriggeredRound: initRound,
+		roundShift:         roundShift,
+	}
+	e.ctx, e.ctxCancel = context.WithCancel(parentCtx)
+	e.config = RoundBasedConfig{}
+	e.config.SetupRoundBasedFields(initRound, GetConfigWithPanic(
+		gov, initRound, logger))
+	e.config.SetRoundBeginHeight(initRoundBeginHeight)
+	// Make sure the DKG reset count in current governance can cover the initial
+	// block height.
+	resetCount := gov.DKGResetCount(initRound + 1)
+	remains := resetCount
+	for ; resetCount > 0 && !e.config.Contains(initBlockHeight); remains-- {
+		e.config.ExtendLength()
+	}
+	if !e.config.Contains(initBlockHeight) {
+		return nil, ErrUnmatchedBlockHeightWithGov{
+			round:       initRound,
+			reset:       resetCount,
+			blockHeight: initBlockHeight,
+		}
+	}
+	e.lastTriggeredResetCount = resetCount - remains
+	return e, nil
+}
+
+// Register a handler to be called when new round is confirmed or new DKG reset
+// is detected.
+func (e *RoundEvent) Register(h roundEventFn) {
+	e.lock.Lock()
+	defer e.lock.Unlock()
+	e.handlers = append(e.handlers, h)
+}
+
+// ValidateNextRound validate if the DKG set for next round is ready to go or
+// failed to setup, all registered handlers would be called once some decision
+// is made on chain.
+//
+// This method would block until at least one event is triggered. Multiple
+// trigger in one call is possible.
+func (e *RoundEvent) ValidateNextRound(blockHeight uint64) {
+	// To make triggers continuous and sequential, the next validation should
+	// wait for previous one finishing. That's why I use mutex here directly.
+	var events []RoundEventParam
+	e.lock.Lock()
+	defer e.lock.Unlock()
+	e.logger.Info("ValidateNextRound",
+		"height", blockHeight,
+		"round", e.lastTriggeredRound,
+		"count", e.lastTriggeredResetCount)
+	defer func() {
+		if len(events) == 0 {
+			return
+		}
+		for _, h := range e.handlers {
+			// To make sure all handlers receive triggers sequentially, we can't
+			// raise go routines here.
+			h(events)
+		}
+	}()
+	startRound := e.lastTriggeredRound
+	for {
+		var (
+			dkgFailed, triggered bool
+			param                RoundEventParam
+			beginHeight          = blockHeight
+		)
+		for {
+			param, dkgFailed, triggered = e.check(beginHeight, startRound,
+				dkgFailed)
+			if !triggered {
+				break
+			}
+			events = append(events, param)
+			beginHeight = param.BeginHeight
+		}
+		if len(events) > 0 {
+			break
+		}
+		select {
+		case <-e.ctx.Done():
+			return
+		case <-time.After(500 * time.Millisecond):
+		}
+	}
+}
+
+func (e *RoundEvent) check(blockHeight, startRound uint64, lastDKGCheck bool) (
+	param RoundEventParam, dkgFailed bool, triggered bool) {
+	defer func() {
+		if !triggered {
+			return
+		}
+		// A simple assertion to make sure we didn't pick the wrong round.
+		if e.config.RoundID() != e.lastTriggeredRound {
+			panic(fmt.Errorf("triggered round not matched: %d, %d",
+				e.config.RoundID(), e.lastTriggeredRound))
+		}
+		param.Round = e.lastTriggeredRound
+		param.Reset = e.lastTriggeredResetCount
+		param.BeginHeight = e.config.LastPeriodBeginHeight()
+		param.CRS = GetCRSWithPanic(e.gov, e.lastTriggeredRound, e.logger)
+		param.Config = GetConfigWithPanic(e.gov, e.lastTriggeredRound, e.logger)
+		e.logger.Info("new RoundEvent triggered",
+			"round", e.lastTriggeredRound,
+			"reset", e.lastTriggeredResetCount,
+			"begin-height", e.config.LastPeriodBeginHeight(),
+			"crs", param.CRS.String()[:6],
+		)
+	}()
+	// Make sure current last config covers the blockHeight.
+	if !e.config.Contains(blockHeight) {
+		panic(ErrUnmatchedBlockHeightWithGov{
+			round:       e.lastTriggeredRound,
+			reset:       e.lastTriggeredResetCount,
+			blockHeight: blockHeight,
+		})
+	}
+	nextRound := e.lastTriggeredRound + 1
+	if nextRound >= startRound+e.roundShift {
+		// Avoid access configuration newer than last confirmed one over
+		// 'roundShift' rounds. Fullnode might crash if we access it before it
+		// knows.
+		return
+	}
+	nextCfg := GetConfigWithPanic(e.gov, nextRound, e.logger)
+	resetCount := e.gov.DKGResetCount(nextRound)
+	if resetCount > e.lastTriggeredResetCount {
+		e.lastTriggeredResetCount++
+		e.config.ExtendLength()
+		triggered = true
+		return
+	}
+	if lastDKGCheck {
+		// We know that DKG already failed, now wait for the DKG set from
+		// previous round to reset DKG and don't have to reconstruct the
+		// group public key again.
+		dkgFailed = true
+		return
+	}
+	if nextRound >= dkgDelayRound {
+		if !e.gov.IsDKGFinal(nextRound) {
+			e.logger.Debug("DKG is not final, waiting for DKG reset",
+				"round", nextRound,
+				"reset", e.lastTriggeredResetCount)
+			return
+		}
+		if _, err := typesDKG.NewGroupPublicKey(
+			nextRound,
+			e.gov.DKGMasterPublicKeys(nextRound),
+			e.gov.DKGComplaints(nextRound),
+			GetDKGThreshold(nextCfg)); err != nil {
+			e.logger.Debug(
+				"group public key setup failed, waiting for DKG reset",
+				"round", nextRound,
+				"reset", e.lastTriggeredResetCount)
+			dkgFailed = true
+			return
+		}
+	}
+	// The DKG set for next round is well prepared.
+	e.lastTriggeredRound = nextRound
+	e.lastTriggeredResetCount = 0
+	rCfg := RoundBasedConfig{}
+	rCfg.SetupRoundBasedFields(nextRound, nextCfg)
+	rCfg.AppendTo(e.config)
+	e.config = rCfg
+	triggered = true
+	return
+}
+
+// Stop the event source and block until last trigger returns.
+func (e *RoundEvent) Stop() {
+	e.ctxCancel()
+}
+
+// LastPeriod returns block height related info of the last period, including
+// begin height and round length.
+func (e *RoundEvent) LastPeriod() (begin uint64, length uint64) {
+	e.lock.Lock()
+	defer e.lock.Unlock()
+	begin = e.config.LastPeriodBeginHeight()
+	length = e.config.RoundEndHeight() - e.config.LastPeriodBeginHeight()
+	return
+}