Proposer Service: Only return attestations within the last epoch (#1911)

* Only return attestations within the last epoch

* make array

* rename for clarity

beacon-chain/rpc/proposer_server.go

@@ -74,6 +74,19 @@ func (ps *ProposerServer) PendingAttestations(ctx context.Context, req *pb.Pendi
 	if err != nil {
 		return nil, fmt.Errorf("could not retrieve pending attestations from operations service: %v", err)
 	}
+
+	// Remove any attestation from the list if their slot is before the start of
+	// the previous epoch. This should be handled in the operationService cleanup
+	// method, but we should filter here in case it wasn't yet processed.
+	lastEpochStartSlot := helpers.StartSlot(helpers.PrevEpoch(beaconState))
+	attsSinceLastEpoch := make([]*pbp2p.Attestation, 0, len(atts))
+	for _, att := range atts {
+		if att.Data.Slot >= lastEpochStartSlot {
+			attsSinceLastEpoch = append(attsSinceLastEpoch, att)
+		}
+	}
+	atts = attsSinceLastEpoch
+
 	if req.FilterReadyForInclusion {
 		var attsReadyForInclusion []*pbp2p.Attestation
 		for _, val := range atts {

beacon-chain/rpc/proposer_server_test.go

@@ -147,6 +147,47 @@ func TestPendingAttestations_FiltersWithinInclusionDelay(t *testing.T) {
 	}
 }
 
+func TestPendingAttestations_FiltersExpiredAttestations(t *testing.T) {
+	db := internal.SetupDB(t)
+	defer internal.TeardownDB(t, db)
+	currentSlot := params.BeaconConfig().GenesisSlot + 100000
+	opService := &mockOperationService{
+		pendingAttestations: []*pbp2p.Attestation{
+			// Expired attestations
+			&pbp2p.Attestation{Data: &pbp2p.AttestationData{Slot: 0}},
+			&pbp2p.Attestation{Data: &pbp2p.AttestationData{Slot: currentSlot - 10000}},
+			&pbp2p.Attestation{Data: &pbp2p.AttestationData{Slot: currentSlot - 5000}},
+			&pbp2p.Attestation{Data: &pbp2p.AttestationData{Slot: currentSlot - 100}},
+			// Non-expired attestations
+			&pbp2p.Attestation{Data: &pbp2p.AttestationData{Slot: currentSlot - 5}},
+			&pbp2p.Attestation{Data: &pbp2p.AttestationData{Slot: currentSlot - 2}},
+			&pbp2p.Attestation{Data: &pbp2p.AttestationData{Slot: currentSlot}},
+		},
+	}
+	expectedNumberOfAttestations := 3
+	proposerServer := &ProposerServer{
+		operationService: opService,
+		beaconDB:         db,
+	}
+	beaconState := &pbp2p.BeaconState{
+		Slot: currentSlot,
+	}
+	if err := db.SaveState(beaconState); err != nil {
+		t.Fatal(err)
+	}
+	res, err := proposerServer.PendingAttestations(context.Background(), &pb.PendingAttestationsRequest{})
+	if err != nil {
+		t.Fatalf("Unexpected error fetching pending attestations: %v", err)
+	}
+	if len(res.PendingAttestations) != expectedNumberOfAttestations {
+		t.Errorf(
+			"Expected pending attestations list length %d, but was %d",
+			expectedNumberOfAttestations,
+			len(res.PendingAttestations),
+		)
+	}
+}
+
 func TestPendingAttestations_OK(t *testing.T) {
 	db := internal.SetupDB(t)
 	defer internal.TeardownDB(t, db)

beacon-chain/rpc/service_test.go

@@ -29,7 +29,9 @@ func (t *TestLogger) Errorf(format string, args ...interface{}) {
 	t.testMap["error"] = true
 }
 
-type mockOperationService struct{}
+type mockOperationService struct {
+	pendingAttestations []*pb.Attestation
+}
 
 func (ms *mockOperationService) IncomingAttFeed() *event.Feed {
 	return new(event.Feed)
@@ -40,6 +42,9 @@ func (ms *mockOperationService) IncomingExitFeed() *event.Feed {
 }
 
 func (ms *mockOperationService) PendingAttestations() ([]*pb.Attestation, error) {
+	if ms.pendingAttestations != nil {
+		return ms.pendingAttestations, nil
+	}
 	return []*pb.Attestation{
 		{
 			AggregationBitfield: []byte("A"),