Fix LatestBeaconRound in Drand

beacon/drand/drand.go

@@ -29,18 +29,6 @@ var log = logrus.WithFields(logrus.Fields{
 	"subsystem": "drand",
 })
 
-// DrandResponse structure representing response from drand network
-type DrandResponse struct {
-	// PreviousSig is the previous signature generated
-	PreviousSig []byte
-	// Round is the round number this beacon is tied to
-	Round uint64
-	// Signature is the BLS deterministic signature over Round || PreviousRand
-	Signature []byte
-	// Randomness for specific round generated by Drand
-	Randomness []byte
-}
-
 type DrandBeacon struct {
 	DrandClient        client.Client
 	PublicKey          kyber.Point
@@ -48,6 +36,7 @@ type DrandBeacon struct {
 
 	cacheLock        sync.Mutex
 	localCache       map[uint64]types.BeaconEntry
+	latestDrandRound uint64
 }
 
 func NewDrandBeacon(ps *pubsub.PubSub) (*DrandBeacon, error) {
@@ -96,12 +85,26 @@ func NewDrandBeacon(ps *pubsub.PubSub) (*DrandBeacon, error) {
 	db.PublicKey = drandChain.PublicKey
 
 	db.drandResultChannel = db.DrandClient.Watch(context.TODO())
-
+	err = db.getLatestDrandResult()
+	if err != nil {
+		return nil, err
+	}
 	go db.loop(context.TODO())
 
 	return db, nil
 }
 
+func (db *DrandBeacon) getLatestDrandResult() error {
+	latestDround, err := db.DrandClient.Get(context.TODO(), 0)
+	if err != nil {
+		log.Errorf("failed to get latest drand round: %v", err)
+		return err
+	}
+	db.cacheValue(newBeaconResultFromDrandResult(latestDround))
+	db.updateLatestDrandRound(latestDround.Round())
+	return nil
+}
+
 func (db *DrandBeacon) loop(ctx context.Context) {
 	for {
 		select {
@@ -111,7 +114,8 @@ func (db *DrandBeacon) loop(ctx context.Context) {
 			}
 		case res := <-db.drandResultChannel:
 			{
-				db.cacheValue(types.NewBeaconEntry(res.Round(), res.Randomness(), map[string]interface{}{"signature": res.Signature()}))
+				db.cacheValue(newBeaconResultFromDrandResult(res))
+				db.updateLatestDrandRound(res.Round())
 			}
 		}
 	}
@@ -163,6 +167,12 @@ func (db *DrandBeacon) getCachedValue(round uint64) *types.BeaconEntry {
 	return &v
 }
 
+func (db *DrandBeacon) updateLatestDrandRound(round uint64) {
+	db.cacheLock.Lock()
+	defer db.cacheLock.Unlock()
+	db.latestDrandRound = round
+}
+
 func (db *DrandBeacon) VerifyEntry(curr, prev types.BeaconEntry) error {
 	if prev.Round == 0 {
 		return nil
@@ -179,11 +189,13 @@ func (db *DrandBeacon) VerifyEntry(curr, prev types.BeaconEntry) error {
 }
 
 func (db *DrandBeacon) LatestBeaconRound() uint64 {
-	latestDround, err := db.DrandClient.Get(context.TODO(), 0)
+	db.cacheLock.Lock()
-	if err != nil {
+	defer db.cacheLock.Unlock()
-		log.Errorf("failed to get latest drand round: %w", err)
+	return db.latestDrandRound
-	}
+}
-	return latestDround.Round()
+
+func newBeaconResultFromDrandResult(res client.Result) types.BeaconEntry {
+	return types.NewBeaconEntry(res.Round(), res.Randomness(), map[string]interface{}{"signature": res.Signature()})
 }
 
 var _ beacon.BeaconAPI = (*DrandBeacon)(nil)