core: only qualified nodes can participant BA (#540)

* core: only qualified nodes can participant BA

* core: remove leader calculation from node set cache

3 files changed, 11 insertions, 40 deletions

diff --git a/core/utils/nodeset-cache.go b/core/utils/nodeset-cache.go
index 89ebd24..89dcfc8 100644
--- a/core/utils/nodeset-cache.go
+++ b/core/utils/nodeset-cache.go
@@ -36,10 +36,9 @@ var (
 )
 
 type sets struct {
-	crs        common.Hash
-	nodeSet    *types.NodeSet
-	notarySet  map[types.NodeID]struct{}
-	leaderNode map[uint64]types.NodeID
+	crs       common.Hash
+	nodeSet   *types.NodeSet
+	notarySet map[types.NodeID]struct{}
 }
 
 // NodeSetCacheInterface interface specifies interface used by NodeSetCache.
@@ -133,30 +132,6 @@ func (cache *NodeSetCache) GetNotarySet(
 	return cache.cloneMap(IDs.notarySet), nil
 }
 
-// GetLeaderNode returns the BA leader of the position.
-func (cache *NodeSetCache) GetLeaderNode(pos types.Position) (
-	types.NodeID, error) {
-	IDs, err := cache.getOrUpdate(pos.Round)
-	if err != nil {
-		return types.NodeID{}, err
-	}
-	cache.lock.Lock()
-	defer cache.lock.Unlock()
-	if _, exist := IDs.leaderNode[pos.Height]; !exist {
-		notarySet := types.NewNodeSetFromMap(IDs.notarySet)
-		leader := notarySet.GetSubSet(1, types.NewNodeLeaderTarget(
-			IDs.crs, pos.Height))
-		if len(leader) != 1 {
-			panic(errors.New("length of leader is not one"))
-		}
-		for nID := range leader {
-			IDs.leaderNode[pos.Height] = nID
-			break
-		}
-	}
-	return IDs.leaderNode[pos.Height], nil
-}
-
 // Purge a specific round.
 func (cache *NodeSetCache) Purge(rID uint64) {
 	cache.lock.Lock()
@@ -238,10 +213,9 @@ func (cache *NodeSetCache) update(round uint64) (nIDs *sets, err error) {
 		return
 	}
 	nIDs = &sets{
-		crs:        crs,
-		nodeSet:    nodeSet,
-		notarySet:  make(map[types.NodeID]struct{}),
-		leaderNode: make(map[uint64]types.NodeID, cfg.RoundLength),
+		crs:       crs,
+		nodeSet:   nodeSet,
+		notarySet: make(map[types.NodeID]struct{}),
 	}
 	nIDs.notarySet = nodeSet.GetSubSet(
 		int(cfg.NotarySetSize), types.NewNotarySetTarget(crs))
diff --git a/core/utils/nodeset-cache_test.go b/core/utils/nodeset-cache_test.go
index 0ee3883..b9052c8 100644
--- a/core/utils/nodeset-cache_test.go
+++ b/core/utils/nodeset-cache_test.go
@@ -90,14 +90,6 @@ func (s *NodeSetCacheTestSuite) TestBasicUsage() {
 	notarySet, err := cache.GetNotarySet(0)
 	req.NoError(err)
 	chk(cache, 0, notarySet)
-	leaderNode, err := cache.GetLeaderNode(types.Position{
-		Round:  uint64(0),
-		Height: uint64(10),
-	})
-	req.NoError(err)
-	chk(cache, 0, map[types.NodeID]struct{}{
-		leaderNode: struct{}{},
-	})
 	// Try to get round 1.
 	nodeSet1, err := cache.GetNodeSet(1)
 	req.NoError(err)
diff --git a/core/utils/utils.go b/core/utils/utils.go
index e6739ce..1a372c7 100644
--- a/core/utils/utils.go
+++ b/core/utils/utils.go
@@ -144,6 +144,11 @@ func GetDKGValidThreshold(config *types.Config) int {
 	return int(config.NotarySetSize * 5 / 6)
 }
 
+// GetBAThreshold return threshold for BA votes.
+func GetBAThreshold(config *types.Config) int {
+	return int(config.NotarySetSize*2/3 + 1)
+}
+
 // GetNextRoundValidationHeight returns the block height to check if the next
 // round is ready.
 func GetNextRoundValidationHeight(begin, length uint64) uint64 {