[HAR-5] leader won't start consensus if not enough validators

Signed-off-by: Leo Chen <leo@harmony.one>

benchmark.go

@@ -92,6 +92,9 @@ func main() {
 	idcPort := flag.String("idc_port", "8080", "port of the identity chain")
 	peerDisvoery := flag.Bool("peer_discovery", false, "Enable Peer Discovery")
 
+	// Leader needs to have a minimal number of peers to start consensus
+	minPeers := flag.Int("min_peers", 100, "Minimal number of Peers in shard")
+
 	flag.Parse()
 
 	if *versionFlag {
@@ -165,6 +168,7 @@ func main() {
 
 	// Consensus object.
 	consensus := consensus.NewConsensus(*ip, *port, shardID, peers, leader)
+	consensus.MinPeers = *minPeers
 
 	// Start Profiler for leader if profile argument is on
 	if role == "leader" && (*profile || *metricsReportURL != "") {

consensus/consensus.go

@@ -39,6 +39,11 @@ type Consensus struct {
 	// However, we have assumed uint16 in consensus/consensus_leader.go:136
 	// we won't change it now
 	validators map[uint16]p2p.Peer
+
+	// Minimal number of peers in the shard
+	// If the number of validators is less than minPeers, the consensus won't start
+	MinPeers int
+
 	// Leader
 	leader p2p.Peer
 	// Public keys of the committee including leader and validators

consensus/consensus_leader.go

@@ -28,6 +28,13 @@ func (consensus *Consensus) WaitForNewBlock(blockChannel chan blockchain.Block)
 	consensus.Log.Debug("Waiting for block", "consensus", consensus)
 	for { // keep waiting for new blocks
 		newBlock := <-blockChannel
+
+		if !consensus.HasEnoughValidators() {
+			consensus.Log.Debug("Not enough validators", "# Validators", len(consensus.validators))
+			time.Sleep(500 * time.Millisecond)
+			continue
+		}
+
 		// TODO: think about potential race condition
 		startTime = time.Now()
 		consensus.Log.Debug("STARTING CONSENSUS", "consensus", consensus, "startTime", startTime)
@@ -452,3 +459,10 @@ func (consensus *Consensus) reportMetrics(block blockchain.Block) {
 	}
 	profiler.LogMetrics(metrics)
 }
+
+func (consensus *Consensus) HasEnoughValidators() bool {
+	if len(consensus.validators) < consensus.MinPeers {
+		return false
+	}
+	return true
+}