Fix sleep logic for attesting (#2048)

* sleep before attesting

* Test

validator/client/validator_attest.go

@@ -22,6 +22,9 @@ var delay = params.BeaconConfig().SecondsPerSlot / 2
 func (v *validator) AttestToBlockHead(ctx context.Context, slot uint64) {
 	ctx, span := trace.StartSpan(ctx, "validator.AttestToBlockHead")
 	defer span.End()
+
+	v.waitToSlotMidpoint(ctx, slot)
+
 	// First the validator should construct attestation_data, an AttestationData
 	// object based upon the state at the assigned slot.
 	attData := &pbp2p.AttestationData{
@@ -118,11 +121,6 @@ func (v *validator) AttestToBlockHead(ctx context.Context, slot uint64) {
 		"slot":           slot - params.BeaconConfig().GenesisSlot,
 	}).Info("Attesting to beacon chain head...")
 
-	duration := time.Duration(slot*params.BeaconConfig().SecondsPerSlot+delay) * time.Second
-	timeToBroadcast := time.Unix(int64(v.genesisTime), 0).Add(duration)
-	_, sleepSpan := trace.StartSpan(ctx, "validator.AttestToBlockHead_sleepUntilTimeToBroadcast")
-	time.Sleep(time.Until(timeToBroadcast))
-	sleepSpan.End()
 	log.Debugf("Produced attestation: %v", attestation)
 	attResp, err := v.attesterClient.AttestHead(ctx, attestation)
 	if err != nil {
@@ -135,3 +133,16 @@ func (v *validator) AttestToBlockHead(ctx context.Context, slot uint64) {
 		"slot":            slot - params.BeaconConfig().GenesisSlot,
 	}).Info("Beacon node processed attestation successfully")
 }
+
+// waitToSlotMidpoint waits until halfway through the current slot period
+// such that any blocks from this slot have time to reach the beacon node
+// before creating the attestation.
+func (v *validator) waitToSlotMidpoint(ctx context.Context, slot uint64) {
+	_, span := trace.StartSpan(ctx, "validator.waitToSlotMidpoint")
+	defer span.End()
+
+	duration := time.Duration(slot*params.BeaconConfig().SecondsPerSlot+delay) * time.Second
+	timeToBroadcast := time.Unix(int64(v.genesisTime), 0).Add(duration)
+
+	time.Sleep(time.Until(timeToBroadcast))
+}

validator/client/validator_attest_test.go

@@ -178,52 +178,29 @@ func TestAttestToBlockHead_DoesNotAttestBeforeDelay(t *testing.T) {
 	validator, m, finish := setup(t)
 	defer finish()
 
-	var wg sync.WaitGroup
-	wg.Add(3)
-	defer wg.Wait()
-
 	validator.genesisTime = uint64(time.Now().Unix())
-	validatorIndex := uint64(5)
-	committee := []uint64{0, 3, 4, 2, validatorIndex, 6, 8, 9, 10}
 	m.validatorClient.EXPECT().CommitteeAssignment(
 		gomock.Any(), // ctx
 		gomock.AssignableToTypeOf(&pb.ValidatorEpochAssignmentsRequest{}),
-		gomock.Any(), // ctx
+		gomock.Any(),
-	).Return(&pb.CommitteeAssignmentResponse{
+	).Times(0)
-		Shard:     5,
-		Committee: committee,
-	}, nil).Do(func(arg0, arg1 interface{}) {
-		wg.Done()
-	})
 
 	m.attesterClient.EXPECT().AttestationDataAtSlot(
 		gomock.Any(), // ctx
 		gomock.AssignableToTypeOf(&pb.AttestationDataRequest{}),
-	).Return(&pb.AttestationDataResponse{
+	).Times(0)
-		BeaconBlockRootHash32:    []byte("A"),
-		EpochBoundaryRootHash32:  []byte("B"),
-		JustifiedBlockRootHash32: []byte("C"),
-		LatestCrosslink:          &pbp2p.Crosslink{CrosslinkDataRootHash32: []byte{'D'}},
-		JustifiedEpoch:           3,
-	}, nil).Do(func(arg0, arg1 interface{}) {
-		wg.Done()
-	})
 
 	m.validatorClient.EXPECT().ValidatorIndex(
 		gomock.Any(), // ctx
 		gomock.AssignableToTypeOf(&pb.ValidatorIndexRequest{}),
-	).Return(&pb.ValidatorIndexResponse{
+	).Times(0)
-		Index: uint64(validatorIndex),
-	}, nil).Do(func(arg0, arg1 interface{}) {
-		wg.Done()
-	})
 
 	m.attesterClient.EXPECT().AttestHead(
 		gomock.Any(), // ctx
 		gomock.AssignableToTypeOf(&pbp2p.Attestation{}),
 	).Return(&pb.AttestResponse{}, nil /* error */).Times(0)
 
-	delay = 2
+	delay = 5
 	go validator.AttestToBlockHead(context.Background(), 0)
 }