Reduce attester state copies (#6025)

* Test

* Fix

* Removed extra line

* Feature flag

* Gaz

beacon-chain/cache/BUILD.bazel

@@ -23,6 +23,7 @@ go_library(
     deps = [
         "//beacon-chain/state:go_default_library",
         "//proto/beacon/p2p/v1:go_default_library",
+        "//shared/featureconfig:go_default_library",
         "//shared/hashutil:go_default_library",
         "//shared/params:go_default_library",
         "//shared/sliceutil:go_default_library",

beacon-chain/cache/attestation_data.go

@@ -11,6 +11,8 @@ import (
 	"github.com/prometheus/client_golang/prometheus"
 	"github.com/prometheus/client_golang/prometheus/promauto"
 	ethpb "github.com/prysmaticlabs/ethereumapis/eth/v1alpha1"
+	"github.com/prysmaticlabs/prysm/beacon-chain/state"
+	"github.com/prysmaticlabs/prysm/shared/featureconfig"
 	"k8s.io/client-go/tools/cache"
 )
 
@@ -97,6 +99,9 @@ func (c *AttestationCache) Get(ctx context.Context, req *ethpb.AttestationDataRe
 
 	if exists && item != nil && item.(*attestationReqResWrapper).res != nil {
 		attestationCacheHit.Inc()
+		if featureconfig.Get().ReduceAttesterStateCopy {
+			return state.CopyAttestationData(item.(*attestationReqResWrapper).res), nil
+		}
 		return item.(*attestationReqResWrapper).res, nil
 	}
 	attestationCacheMiss.Inc()
@@ -162,6 +167,9 @@ func wrapperToKey(i interface{}) (string, error) {
 }
 
 func reqToKey(req *ethpb.AttestationDataRequest) (string, error) {
+	if featureconfig.Get().ReduceAttesterStateCopy {
+		return fmt.Sprintf("%d", req.Slot), nil
+	}
 	return fmt.Sprintf("%d-%d", req.CommitteeIndex, req.Slot), nil
 }
 

beacon-chain/rpc/validator/attester.go

@@ -47,6 +47,9 @@ func (vs *Server) GetAttestationData(ctx context.Context, req *ethpb.Attestation
 		return nil, status.Errorf(codes.Internal, "Could not retrieve data from attestation cache: %v", err)
 	}
 	if res != nil {
+		if featureconfig.Get().ReduceAttesterStateCopy {
+			res.CommitteeIndex = req.CommitteeIndex
+		}
 		return res, nil
 	}
 
@@ -59,6 +62,9 @@ func (vs *Server) GetAttestationData(ctx context.Context, req *ethpb.Attestation
 			if res == nil {
 				return nil, status.Error(codes.DataLoss, "A request was in progress and resolved to nil")
 			}
+			if featureconfig.Get().ReduceAttesterStateCopy {
+				res.CommitteeIndex = req.CommitteeIndex
+			}
 			return res, nil
 		}
 		return nil, status.Errorf(codes.Internal, "Could not mark attestation as in-progress: %v", err)

shared/featureconfig/config.go

@@ -58,6 +58,7 @@ type Flags struct {
 	WaitForSynced                              bool // WaitForSynced uses WaitForSynced in validator startup to ensure it can communicate with the beacon node as soon as possible.
 	SkipRegenHistoricalStates                  bool // SkipRegenHistoricalState skips regenerating historical states from genesis to last finalized. This enables a quick switch over to using new-state-mgmt.
 	EnableInitSyncWeightedRoundRobin           bool // EnableInitSyncWeightedRoundRobin enables weighted round robin fetching optimization in initial syncing.
+	ReduceAttesterStateCopy                    bool // ReduceAttesterStateCopy reduces head state copies for attester rpc.
 
 	// DisableForkChoice disables using LMD-GHOST fork choice to update
 	// the head of the chain based on attestations and instead accepts any valid received block
@@ -215,6 +216,10 @@ func ConfigureBeaconChain(ctx *cli.Context) {
 		log.Warn("Disabling state reference copy")
 		cfg.EnableStateRefCopy = false
 	}
+	if ctx.Bool(reduceAttesterStateCopy.Name) {
+		log.Warn("Enabling feature that reduces attester state copy")
+		cfg.ReduceAttesterStateCopy = true
+	}
 	Init(cfg)
 }
 

shared/featureconfig/flags.go

@@ -157,12 +157,17 @@ var (
 		Name:  "enable-init-sync-wrr",
 		Usage: "Enables weighted round robin fetching optimization",
 	}
+	reduceAttesterStateCopy = &cli.BoolFlag{
+		Name:  "reduce-attester-state-copy",
+		Usage: "Reduces the amount of state copies for attester rpc",
+	}
 )
 
 // devModeFlags holds list of flags that are set when development mode is on.
 var devModeFlags = []cli.Flag{
 	enableNewStateMgmt,
 	enableInitSyncWeightedRoundRobin,
+	reduceAttesterStateCopy,
 }
 
 // Deprecated flags list.
@@ -481,6 +486,7 @@ var BeaconChainFlags = append(deprecatedFlags, []cli.Flag{
 	enableInitSyncWeightedRoundRobin,
 	disableFieldTrie,
 	disableStateRefCopy,
+	reduceAttesterStateCopy,
 }...)
 
 // E2EBeaconChainFlags contains a list of the beacon chain feature flags to be tested in E2E.
@@ -490,4 +496,5 @@ var E2EBeaconChainFlags = []string{
 	"--check-head-state",
 	"--enable-new-state-mgmt",
 	"--enable-init-sync-wrr",
+	"--reduce-attester-state-copy",
 }