Reduce cost of BLS key serialization over gRPC (#1343)

Author: hexfusion

snow/validators/gvalidators/validator_state_client.go

@@ -5,6 +5,7 @@ package gvalidators
 
 import (
 	"context"
+	"errors"
 
 	"google.golang.org/protobuf/types/known/emptypb"
 
@@ -15,7 +16,10 @@ import (
 	pb "github.com/ava-labs/avalanchego/proto/pb/validatorstate"
 )
 
-var _ validators.State = (*Client)(nil)
+var (
+	_                             validators.State = (*Client)(nil)
+	errFailedPublicKeyDeserialize                  = errors.New("couldn't deserialize public key")
+)
 
 type Client struct {
 	client pb.ValidatorStateClient
@@ -72,9 +76,13 @@ func (c *Client) GetValidatorSet(
 		}
 		var publicKey *bls.PublicKey
 		if len(validator.PublicKey) > 0 {
-			publicKey, err = bls.PublicKeyFromBytes(validator.PublicKey)
-			if err != nil {
-				return nil, err
+			// This is a performance optimization to avoid the cost of compression
+			// and key re-verification with PublicKeyFromBytes. We can safely
+			// assume that the BLS Public Keys are verified before being added
+			// to the P-Chain and served by the gRPC server.
+			publicKey = new(bls.PublicKey).Deserialize(validator.PublicKey)
+			if publicKey == nil {
+				return nil, errFailedPublicKeyDeserialize
 			}
 		}
 		vdrs[nodeID] = &validators.GetValidatorOutput{

snow/validators/gvalidators/validator_state_server.go

@@ -10,7 +10,6 @@ import (
 
 	"github.com/ava-labs/avalanchego/ids"
 	"github.com/ava-labs/avalanchego/snow/validators"
-	"github.com/ava-labs/avalanchego/utils/crypto/bls"
 
 	pb "github.com/ava-labs/avalanchego/proto/pb/validatorstate"
 )
@@ -70,7 +69,9 @@ func (s *Server) GetValidatorSet(ctx context.Context, req *pb.GetValidatorSetReq
 			Weight: vdr.Weight,
 		}
 		if vdr.PublicKey != nil {
-			vdrPB.PublicKey = bls.PublicKeyToBytes(vdr.PublicKey)
+			// This is a performance optimization to avoid the cost of compression
+			// from PublicKeyToBytes.
+			vdrPB.PublicKey = vdr.PublicKey.Serialize()
 		}
 		resp.Validators[i] = vdrPB
 		i++

snow/validators/gvalidators/validator_state_test.go

@@ -183,6 +183,19 @@ func TestGetValidatorSet(t *testing.T) {
 	require.Error(err)
 }
 
+func TestPublicKeyDeserialize(t *testing.T) {
+	require := require.New(t)
+
+	sk, err := bls.NewSecretKey()
+	require.NoError(err)
+	pk := bls.PublicFromSecretKey(sk)
+
+	pkBytes := pk.Serialize()
+	pkDe := new(bls.PublicKey).Deserialize(pkBytes)
+	require.NotNil(pkDe)
+	require.EqualValues(pk, pkDe)
+}
+
 // BenchmarkGetValidatorSet measures the time it takes complete a gRPC client
 // request based on a mocked validator set.
 func BenchmarkGetValidatorSet(b *testing.B) {