Optimize ListBeaconCommittees to use committees cache (prysmaticlabs#…

…4464)

beacon-chain/blockchain/service.go

@@ -195,7 +195,6 @@ func (s *Service) initializeBeaconChain(
 	eth1data *ethpb.Eth1Data) error {
 	_, span := trace.StartSpan(context.Background(), "beacon-chain.Service.initializeBeaconChain")
 	defer span.End()
-	log.Info("Genesis time reached, starting the beacon chain")
 	s.genesisTime = genesisTime
 	unixTime := uint64(genesisTime.Unix())
 
@@ -208,6 +207,8 @@ func (s *Service) initializeBeaconChain(
 		return errors.Wrap(err, "could not save genesis data")
 	}
 
+	log.Info("Initialized beacon chain genesis state")
+
 	// Update committee shuffled indices for genesis epoch.
 	if featureconfig.Get().EnableNewCache {
 		if err := helpers.UpdateCommitteeCache(genesisState, 0 /* genesis epoch */); err != nil {

beacon-chain/blockchain/service_test.go

@@ -176,7 +176,7 @@ func TestChainStartStop_Uninitialized(t *testing.T) {
 		t.Error("Context was not canceled")
 	}
 	testutil.AssertLogsContain(t, hook, "Waiting")
-	testutil.AssertLogsContain(t, hook, "Genesis time reached")
+	testutil.AssertLogsContain(t, hook, "Initialized beacon chain genesis state")
 }
 
 func TestChainStartStop_Initialized(t *testing.T) {

beacon-chain/rpc/beacon/committees.go

@@ -105,10 +105,8 @@ func (bs *Server) ListBeaconCommittees(
 			countAtSlot = 1
 		}
 		committeeItems := make([]*ethpb.BeaconCommittees_CommitteeItem, countAtSlot)
-		for i := uint64(0); i < countAtSlot; i++ {
-			epochOffset := i + (slot%params.BeaconConfig().SlotsPerEpoch)*countAtSlot
-			totalCount := countAtSlot * params.BeaconConfig().SlotsPerEpoch
-			committee, err := helpers.ComputeCommittee(activeIndices, attesterSeed, epochOffset, totalCount)
+		for committeeIndex := uint64(0); committeeIndex < countAtSlot; committeeIndex++ {
+			committee, err := helpers.BeaconCommittee(activeIndices, attesterSeed, slot, committeeIndex)
 			if err != nil {
 				return nil, status.Errorf(
 					codes.Internal,
@@ -117,7 +115,7 @@ func (bs *Server) ListBeaconCommittees(
 					err,
 				)
 			}
-			committeeItems[i] = &ethpb.BeaconCommittees_CommitteeItem{
+			committeeItems[committeeIndex] = &ethpb.BeaconCommittees_CommitteeItem{
 				ValidatorIndices: committee,
 			}
 		}