Better comments for aggregator functions (#9053)

* Better comments for aggregator functions

* Naming returned value

validator/client/aggregate.go

@@ -49,7 +49,7 @@ func (v *validator) SubmitAggregateAndProof(ctx context.Context, slot types.Slot
 	v.aggregatedSlotCommitteeIDCache.Add(k, true)
 	v.aggregatedSlotCommitteeIDCacheLock.Unlock()
 
-	slotSig, err := v.signSlot(ctx, pubKey, slot)
+	slotSig, err := v.signSlotWithSelectionProof(ctx, pubKey, slot)
 	if err != nil {
 		log.Errorf("Could not sign slot: %v", err)
 		if v.emitAccountMetrics {
@@ -115,9 +115,8 @@ func (v *validator) SubmitAggregateAndProof(ctx context.Context, slot types.Slot
 
 }
 
-// This implements selection logic outlined in:
-// https://github.com/ethereum/eth2.0-specs/blob/v0.9.3/specs/validator/0_beacon-chain-validator.md#aggregation-selection
-func (v *validator) signSlot(ctx context.Context, pubKey [48]byte, slot types.Slot) ([]byte, error) {
+// Signs input slot with domain selection proof. This is used to create the signature for aggregator selection.
+func (v *validator) signSlotWithSelectionProof(ctx context.Context, pubKey [48]byte, slot types.Slot) (signature []byte, error error) {
 	domain, err := v.domainData(ctx, helpers.SlotToEpoch(slot), params.BeaconConfig().DomainSelectionProof[:])
 	if err != nil {
 		return nil, err

validator/client/validator.go

@@ -546,15 +546,15 @@ func (v *validator) GetKeymanager() keymanager.IKeymanager {
 	return v.keyManager
 }
 
-// isAggregator checks if a validator is an aggregator of a given slot, it uses the selection algorithm outlined in:
-// https://github.com/ethereum/eth2.0-specs/blob/v0.9.3/specs/validator/0_beacon-chain-validator.md#aggregation-selection
+// isAggregator checks if a validator is an aggregator of a given slot and committee,
+// it uses a modulo calculated by validator count in committee and samples randomness around it.
 func (v *validator) isAggregator(ctx context.Context, committee []types.ValidatorIndex, slot types.Slot, pubKey [48]byte) (bool, error) {
 	modulo := uint64(1)
 	if len(committee)/int(params.BeaconConfig().TargetAggregatorsPerCommittee) > 1 {
 		modulo = uint64(len(committee)) / params.BeaconConfig().TargetAggregatorsPerCommittee
 	}
 
-	slotSig, err := v.signSlot(ctx, pubKey, slot)
+	slotSig, err := v.signSlotWithSelectionProof(ctx, pubKey, slot)
 	if err != nil {
 		return false, err
 	}