only initialize kzg if it will be used (#12803)

Co-authored-by: Kasey Kirkham <kasey@users.noreply.github.com>

beacon-chain/blockchain/service.go

@@ -103,9 +103,12 @@ type blobNotifier struct {
 // NewService instantiates a new block service instance that will
 // be registered into a running beacon node.
 func NewService(ctx context.Context, opts ...Option) (*Service, error) {
-	err := kzg.Start()
-	if err != nil {
-		return nil, errors.Wrap(err, "could not initialize go-kzg context")
+	var err error
+	if params.DenebEnabled() {
+		err = kzg.Start()
+		if err != nil {
+			return nil, errors.Wrap(err, "could not initialize go-kzg context")
+		}
 	}
 	ctx, cancel := context.WithCancel(ctx)
 	bn := &blobNotifier{

config/params/config.go

@@ -2,6 +2,7 @@
 package params
 
 import (
+	"math"
 	"time"
 
 	"github.com/ethereum/go-ethereum/common"
@@ -275,3 +276,10 @@ func (b *BeaconChainConfig) PreviousEpochAttestationsLength() uint64 {
 func (b *BeaconChainConfig) CurrentEpochAttestationsLength() uint64 {
 	return uint64(b.SlotsPerEpoch.Mul(b.MaxAttestations))
 }
+
+// DenebEnabled centralizes the check to determine if code paths
+// that are specific to deneb should be allowed to execute. This will make it easier to find call sites that do this
+// kind of check and remove them post-deneb.
+func DenebEnabled() bool {
+	return BeaconConfig().DenebForkEpoch < math.MaxUint64
+}