throw 503 error when submit attestation and sync committee are called on syncing node + align changes to gRPC (#16152)

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**What type of PR is this?**

Bug fix


**What does this PR do? Why is it needed?**

Prysm starting throwing this error `Could not write response message"
error="write tcp 10.104.92.212:5052->10.104.92.196:41876: write: broken
pipe` because a validator got attestation data from a synced node and
submitted attestation to a syncing node, when the node couldn't replay
the state the validator context deadlined and disconnected but the
writer when it finally responded tries to write it gets this broken pipe
error.

applies to `/eth/v2/beacon/pool/attestations` and
`/eth/v1/beacon/pool/sync_committees`

the solution is 2 part.
1. we shouldn't allow submission of an attestation if the node is
syncing because we can't save the attestation without the state
information.
2. we were doing the expensive state call before broadcast before in
rest and now it should match gRPC where it happens afterward in its own
go routine.

Tested manually running kurtosis with rest validators

```
participants:
 # Super-nodes
 - el_type: nethermind
   cl_type: prysm
   cl_image: gcr.io/offchainlabs/prysm/beacon-chain:latest
   count: 2
   supernode: true
   cl_extra_params:
     - --subscribe-all-subnets
     - --verbosity=debug
   vc_extra_params:
     - --enable-beacon-rest-api
     - --verbosity=debug

 # Full-nodes
 - el_type: nethermind
   cl_type: prysm
   cl_image: gcr.io/offchainlabs/prysm/beacon-chain:latest
   validator_count: 63
   cl_extra_params:
     - --verbosity=debug
   vc_extra_params:
     - --enable-beacon-rest-api
     - --verbosity=debug

 - el_type: nethermind
   cl_type: prysm
   cl_image: gcr.io/offchainlabs/prysm/beacon-chain:latest
   cl_extra_params:
     - --verbosity=debug
   vc_extra_params:
     - --enable-beacon-rest-api
     - --verbosity=debug
   validator_count: 13

additional_services:
 - dora
 - spamoor

spamoor_params:
 image: ethpandaops/spamoor:master
 max_mem: 4000
 spammers:
   - scenario: eoatx
     config:
       throughput: 200
   - scenario: blobs
     config:
       throughput: 20

network_params:
  fulu_fork_epoch: 2
  bpo_1_epoch: 8
  bpo_1_max_blobs: 21
  withdrawal_type: "0x02"
  preset: mainnet
  seconds_per_slot: 6

global_log_level: debug
```

**Which issues(s) does this PR fix?**

Fixes #

**Other notes for review**

**Acknowledgements**

- [x] I have read
[CONTRIBUTING.md](https://github.com/prysmaticlabs/prysm/blob/develop/CONTRIBUTING.md).
- [x] I have included a uniquely named [changelog fragment
file](https://github.com/prysmaticlabs/prysm/blob/develop/CONTRIBUTING.md#maintaining-changelogmd).
- [x] I have added a description with sufficient context for reviewers
to understand this PR.
- [x] I have tested that my changes work as expected and I added a
testing plan to the PR description (if applicable).

beacon-chain/rpc/eth/beacon/handlers_pool.go

@@ -130,6 +130,10 @@ func (s *Server) SubmitAttestationsV2(w http.ResponseWriter, r *http.Request) {
 	ctx, span := trace.StartSpan(r.Context(), "beacon.SubmitAttestationsV2")
 	defer span.End()
 
+	if shared.IsSyncing(ctx, w, s.SyncChecker, s.HeadFetcher, s.TimeFetcher, s.OptimisticModeFetcher) {
+		return
+	}
+
 	versionHeader := r.Header.Get(api.VersionHeader)
 	if versionHeader == "" {
 		httputil.HandleError(w, api.VersionHeader+" header is required", http.StatusBadRequest)
@@ -238,22 +242,14 @@ func (s *Server) handleAttestationsElectra(
 			},
 		})
 
-		targetState, err := s.AttestationStateFetcher.AttestationTargetState(ctx, singleAtt.Data.Target)
-		if err != nil {
-			return nil, nil, errors.Wrap(err, "could not get target state for attestation")
-		}
-		committee, err := corehelpers.BeaconCommitteeFromState(ctx, targetState, singleAtt.Data.Slot, singleAtt.CommitteeId)
-		if err != nil {
-			return nil, nil, errors.Wrap(err, "could not get committee for attestation")
-		}
-		att := singleAtt.ToAttestationElectra(committee)
-
-		wantedEpoch := slots.ToEpoch(att.Data.Slot)
+		// Broadcast first using CommitteeId directly (fast path)
+		// This matches gRPC behavior and avoids blocking on state fetching
+		wantedEpoch := slots.ToEpoch(singleAtt.Data.Slot)
 		vals, err := s.HeadFetcher.HeadValidatorsIndices(ctx, wantedEpoch)
 		if err != nil {
 			return nil, nil, errors.Wrap(err, "could not get head validator indices")
 		}
-		subnet := corehelpers.ComputeSubnetFromCommitteeAndSlot(uint64(len(vals)), att.GetCommitteeIndex(), att.Data.Slot)
+		subnet := corehelpers.ComputeSubnetFromCommitteeAndSlot(uint64(len(vals)), singleAtt.CommitteeId, singleAtt.Data.Slot)
 		if err = s.Broadcaster.BroadcastAttestation(ctx, subnet, singleAtt); err != nil {
 			failedBroadcasts = append(failedBroadcasts, &server.IndexedError{
 				Index:   i,
@@ -264,17 +260,35 @@ func (s *Server) handleAttestationsElectra(
 			}
 			continue
 		}
+	}
 
-		if features.Get().EnableExperimentalAttestationPool {
-			if err = s.AttestationCache.Add(att); err != nil {
-				log.WithError(err).Error("Could not save attestation")
+	// Save to pool after broadcast (slow path - requires state fetching)
+	// Run in goroutine to avoid blocking the HTTP response
+	go func() {
+		for _, singleAtt := range validAttestations {
+			targetState, err := s.AttestationStateFetcher.AttestationTargetState(context.Background(), singleAtt.Data.Target)
+			if err != nil {
+				log.WithError(err).Error("Could not get target state for attestation")
+				continue
 			}
-		} else {
-			if err = s.AttestationsPool.SaveUnaggregatedAttestation(att); err != nil {
-				log.WithError(err).Error("Could not save attestation")
+			committee, err := corehelpers.BeaconCommitteeFromState(context.Background(), targetState, singleAtt.Data.Slot, singleAtt.CommitteeId)
+			if err != nil {
+				log.WithError(err).Error("Could not get committee for attestation")
+				continue
+			}
+			att := singleAtt.ToAttestationElectra(committee)
+
+			if features.Get().EnableExperimentalAttestationPool {
+				if err = s.AttestationCache.Add(att); err != nil {
+					log.WithError(err).Error("Could not save attestation")
+				}
+			} else {
+				if err = s.AttestationsPool.SaveUnaggregatedAttestation(att); err != nil {
+					log.WithError(err).Error("Could not save attestation")
+				}
 			}
 		}
-	}
+	}()
 
 	if len(failedBroadcasts) > 0 {
 		log.WithFields(logrus.Fields{
@@ -470,6 +484,10 @@ func (s *Server) SubmitSyncCommitteeSignatures(w http.ResponseWriter, r *http.Re
 	ctx, span := trace.StartSpan(r.Context(), "beacon.SubmitPoolSyncCommitteeSignatures")
 	defer span.End()
 
+	if shared.IsSyncing(ctx, w, s.SyncChecker, s.HeadFetcher, s.TimeFetcher, s.OptimisticModeFetcher) {
+		return
+	}
+
 	var req structs.SubmitSyncCommitteeSignaturesRequest
 	err := json.NewDecoder(r.Body).Decode(&req.Data)
 	switch {

beacon-chain/rpc/eth/beacon/handlers_pool_test.go

@@ -26,6 +26,7 @@ import (
 	"github.com/OffchainLabs/prysm/v7/beacon-chain/operations/voluntaryexits/mock"
 	p2pMock "github.com/OffchainLabs/prysm/v7/beacon-chain/p2p/testing"
 	"github.com/OffchainLabs/prysm/v7/beacon-chain/rpc/core"
+	mockSync "github.com/OffchainLabs/prysm/v7/beacon-chain/sync/initial-sync/testing"
 	state_native "github.com/OffchainLabs/prysm/v7/beacon-chain/state/state-native"
 	"github.com/OffchainLabs/prysm/v7/config/params"
 	"github.com/OffchainLabs/prysm/v7/consensus-types/primitives"
@@ -622,6 +623,8 @@ func TestSubmitAttestationsV2(t *testing.T) {
 		HeadFetcher:             chainService,
 		ChainInfoFetcher:        chainService,
 		TimeFetcher:             chainService,
+		OptimisticModeFetcher:   chainService,
+		SyncChecker:             &mockSync.Sync{IsSyncing: false},
 		OperationNotifier:       &blockchainmock.MockOperationNotifier{},
 		AttestationStateFetcher: chainService,
 	}
@@ -654,6 +657,7 @@ func TestSubmitAttestationsV2(t *testing.T) {
 			assert.Equal(t, primitives.Epoch(0), broadcaster.BroadcastAttestations[0].GetData().Source.Epoch)
 			assert.Equal(t, "0xcf8e0d4e9587369b2301d0790347320302cc0943d5a1884560367e8208d920f2", hexutil.Encode(broadcaster.BroadcastAttestations[0].GetData().Target.Root))
 			assert.Equal(t, primitives.Epoch(0), broadcaster.BroadcastAttestations[0].GetData().Target.Epoch)
+			time.Sleep(100 * time.Millisecond) // Wait for async pool save
 			assert.Equal(t, 1, s.AttestationsPool.UnaggregatedAttestationCount())
 		})
 		t.Run("multiple", func(t *testing.T) {
@@ -673,6 +677,7 @@ func TestSubmitAttestationsV2(t *testing.T) {
 			assert.Equal(t, http.StatusOK, writer.Code)
 			assert.Equal(t, true, broadcaster.BroadcastCalled.Load())
 			assert.Equal(t, 2, broadcaster.NumAttestations())
+			time.Sleep(100 * time.Millisecond) // Wait for async pool save
 			assert.Equal(t, 2, s.AttestationsPool.UnaggregatedAttestationCount())
 		})
 		t.Run("phase0 att post electra", func(t *testing.T) {
@@ -793,6 +798,7 @@ func TestSubmitAttestationsV2(t *testing.T) {
 			assert.Equal(t, primitives.Epoch(0), broadcaster.BroadcastAttestations[0].GetData().Source.Epoch)
 			assert.Equal(t, "0xcf8e0d4e9587369b2301d0790347320302cc0943d5a1884560367e8208d920f2", hexutil.Encode(broadcaster.BroadcastAttestations[0].GetData().Target.Root))
 			assert.Equal(t, primitives.Epoch(0), broadcaster.BroadcastAttestations[0].GetData().Target.Epoch)
+			time.Sleep(100 * time.Millisecond) // Wait for async pool save
 			assert.Equal(t, 1, s.AttestationsPool.UnaggregatedAttestationCount())
 		})
 		t.Run("multiple", func(t *testing.T) {
@@ -812,6 +818,7 @@ func TestSubmitAttestationsV2(t *testing.T) {
 			assert.Equal(t, http.StatusOK, writer.Code)
 			assert.Equal(t, true, broadcaster.BroadcastCalled.Load())
 			assert.Equal(t, 2, broadcaster.NumAttestations())
+			time.Sleep(100 * time.Millisecond) // Wait for async pool save
 			assert.Equal(t, 2, s.AttestationsPool.UnaggregatedAttestationCount())
 		})
 		t.Run("no body", func(t *testing.T) {
@@ -861,6 +868,27 @@ func TestSubmitAttestationsV2(t *testing.T) {
 			assert.Equal(t, true, strings.Contains(e.Failures[0].Message, "Incorrect attestation signature"))
 		})
 	})
+	t.Run("syncing", func(t *testing.T) {
+		chainService := &blockchainmock.ChainService{}
+		s := &Server{
+			HeadFetcher:           chainService,
+			TimeFetcher:           chainService,
+			OptimisticModeFetcher: chainService,
+			SyncChecker:           &mockSync.Sync{IsSyncing: true},
+		}
+
+		var body bytes.Buffer
+		_, err := body.WriteString(singleAtt)
+		require.NoError(t, err)
+		request := httptest.NewRequest(http.MethodPost, "http://example.com", &body)
+		request.Header.Set(api.VersionHeader, version.String(version.Phase0))
+		writer := httptest.NewRecorder()
+		writer.Body = &bytes.Buffer{}
+
+		s.SubmitAttestationsV2(writer, request)
+		assert.Equal(t, http.StatusServiceUnavailable, writer.Code)
+		assert.Equal(t, true, strings.Contains(writer.Body.String(), "Beacon node is currently syncing"))
+	})
 }
 
 func TestListVoluntaryExits(t *testing.T) {
@@ -1057,14 +1085,19 @@ func TestSubmitSyncCommitteeSignatures(t *testing.T) {
 
 	t.Run("single", func(t *testing.T) {
 		broadcaster := &p2pMock.MockBroadcaster{}
+		chainService := &blockchainmock.ChainService{
+			State:                st,
+			SyncCommitteeIndices: []primitives.CommitteeIndex{0},
+		}
 		s := &Server{
+			HeadFetcher:           chainService,
+			TimeFetcher:           chainService,
+			OptimisticModeFetcher: chainService,
+			SyncChecker:           &mockSync.Sync{IsSyncing: false},
 			CoreService: &core.Service{
 				SyncCommitteePool: synccommittee.NewStore(),
 				P2P:               broadcaster,
-				HeadFetcher: &blockchainmock.ChainService{
-					State:                st,
-					SyncCommitteeIndices: []primitives.CommitteeIndex{0},
-				},
+				HeadFetcher:       chainService,
 			},
 		}
 
@@ -1089,14 +1122,19 @@ func TestSubmitSyncCommitteeSignatures(t *testing.T) {
 	})
 	t.Run("multiple", func(t *testing.T) {
 		broadcaster := &p2pMock.MockBroadcaster{}
+		chainService := &blockchainmock.ChainService{
+			State:                st,
+			SyncCommitteeIndices: []primitives.CommitteeIndex{0},
+		}
 		s := &Server{
+			HeadFetcher:           chainService,
+			TimeFetcher:           chainService,
+			OptimisticModeFetcher: chainService,
+			SyncChecker:           &mockSync.Sync{IsSyncing: false},
 			CoreService: &core.Service{
 				SyncCommitteePool: synccommittee.NewStore(),
 				P2P:               broadcaster,
-				HeadFetcher: &blockchainmock.ChainService{
-					State:                st,
-					SyncCommitteeIndices: []primitives.CommitteeIndex{0},
-				},
+				HeadFetcher:       chainService,
 			},
 		}
 
@@ -1120,13 +1158,18 @@ func TestSubmitSyncCommitteeSignatures(t *testing.T) {
 	})
 	t.Run("invalid", func(t *testing.T) {
 		broadcaster := &p2pMock.MockBroadcaster{}
+		chainService := &blockchainmock.ChainService{
+			State: st,
+		}
 		s := &Server{
+			HeadFetcher:           chainService,
+			TimeFetcher:           chainService,
+			OptimisticModeFetcher: chainService,
+			SyncChecker:           &mockSync.Sync{IsSyncing: false},
 			CoreService: &core.Service{
 				SyncCommitteePool: synccommittee.NewStore(),
 				P2P:               broadcaster,
-				HeadFetcher: &blockchainmock.ChainService{
-					State: st,
-				},
+				HeadFetcher:       chainService,
 			},
 		}
 
@@ -1149,7 +1192,13 @@ func TestSubmitSyncCommitteeSignatures(t *testing.T) {
 		assert.Equal(t, false, broadcaster.BroadcastCalled.Load())
 	})
 	t.Run("empty", func(t *testing.T) {
-		s := &Server{}
+		chainService := &blockchainmock.ChainService{State: st}
+		s := &Server{
+			HeadFetcher:           chainService,
+			TimeFetcher:           chainService,
+			OptimisticModeFetcher: chainService,
+			SyncChecker:           &mockSync.Sync{IsSyncing: false},
+		}
 
 		var body bytes.Buffer
 		_, err := body.WriteString("[]")
@@ -1166,7 +1215,13 @@ func TestSubmitSyncCommitteeSignatures(t *testing.T) {
 		assert.Equal(t, true, strings.Contains(e.Message, "No data submitted"))
 	})
 	t.Run("no body", func(t *testing.T) {
-		s := &Server{}
+		chainService := &blockchainmock.ChainService{State: st}
+		s := &Server{
+			HeadFetcher:           chainService,
+			TimeFetcher:           chainService,
+			OptimisticModeFetcher: chainService,
+			SyncChecker:           &mockSync.Sync{IsSyncing: false},
+		}
 
 		request := httptest.NewRequest(http.MethodPost, "http://example.com", nil)
 		writer := httptest.NewRecorder()
@@ -1179,6 +1234,26 @@ func TestSubmitSyncCommitteeSignatures(t *testing.T) {
 		assert.Equal(t, http.StatusBadRequest, e.Code)
 		assert.Equal(t, true, strings.Contains(e.Message, "No data submitted"))
 	})
+	t.Run("syncing", func(t *testing.T) {
+		chainService := &blockchainmock.ChainService{State: st}
+		s := &Server{
+			HeadFetcher:           chainService,
+			TimeFetcher:           chainService,
+			OptimisticModeFetcher: chainService,
+			SyncChecker:           &mockSync.Sync{IsSyncing: true},
+		}
+
+		var body bytes.Buffer
+		_, err := body.WriteString(singleSyncCommitteeMsg)
+		require.NoError(t, err)
+		request := httptest.NewRequest(http.MethodPost, "http://example.com", &body)
+		writer := httptest.NewRecorder()
+		writer.Body = &bytes.Buffer{}
+
+		s.SubmitSyncCommitteeSignatures(writer, request)
+		assert.Equal(t, http.StatusServiceUnavailable, writer.Code)
+		assert.Equal(t, true, strings.Contains(writer.Body.String(), "Beacon node is currently syncing"))
+	})
 }
 
 func TestListBLSToExecutionChanges(t *testing.T) {

beacon-chain/rpc/prysm/v1alpha1/validator/attester.go

@@ -52,24 +52,27 @@ func (vs *Server) ProposeAttestation(ctx context.Context, att *ethpb.Attestation
 	ctx, span := trace.StartSpan(ctx, "AttesterServer.ProposeAttestation")
 	defer span.End()
 
+	if vs.SyncChecker.Syncing() {
+		return nil, status.Errorf(codes.Unavailable, "Syncing to latest head, not ready to respond")
+	}
+
 	resp, err := vs.proposeAtt(ctx, att, att.GetData().CommitteeIndex)
 	if err != nil {
 		return nil, err
 	}
 
-	if features.Get().EnableExperimentalAttestationPool {
-		if err = vs.AttestationCache.Add(att); err != nil {
-			log.WithError(err).Error("Could not save attestation")
-		}
-	} else {
-		go func() {
+	go func() {
+		if features.Get().EnableExperimentalAttestationPool {
+			if err := vs.AttestationCache.Add(att); err != nil {
+				log.WithError(err).Error("Could not save attestation")
+			}
+		} else {
 			attCopy := att.Copy()
 			if err := vs.AttPool.SaveUnaggregatedAttestation(attCopy); err != nil {
 				log.WithError(err).Error("Could not save unaggregated attestation")
-				return
 			}
-		}()
-	}
+		}
+	}()
 
 	return resp, nil
 }
@@ -82,6 +85,10 @@ func (vs *Server) ProposeAttestationElectra(ctx context.Context, singleAtt *ethp
 	ctx, span := trace.StartSpan(ctx, "AttesterServer.ProposeAttestationElectra")
 	defer span.End()
 
+	if vs.SyncChecker.Syncing() {
+		return nil, status.Errorf(codes.Unavailable, "Syncing to latest head, not ready to respond")
+	}
+
 	resp, err := vs.proposeAtt(ctx, singleAtt, singleAtt.GetCommitteeIndex())
 	if err != nil {
 		return nil, err
@@ -98,18 +105,17 @@ func (vs *Server) ProposeAttestationElectra(ctx context.Context, singleAtt *ethp
 
 	singleAttCopy := singleAtt.Copy()
 	att := singleAttCopy.ToAttestationElectra(committee)
-	if features.Get().EnableExperimentalAttestationPool {
-		if err = vs.AttestationCache.Add(att); err != nil {
-			log.WithError(err).Error("Could not save attestation")
-		}
-	} else {
-		go func() {
+	go func() {
+		if features.Get().EnableExperimentalAttestationPool {
+			if err := vs.AttestationCache.Add(att); err != nil {
+				log.WithError(err).Error("Could not save attestation")
+			}
+		} else {
 			if err := vs.AttPool.SaveUnaggregatedAttestation(att); err != nil {
 				log.WithError(err).Error("Could not save unaggregated attestation")
-				return
 			}
-		}()
-	}
+		}
+	}()
 
 	return resp, nil
 }

beacon-chain/rpc/prysm/v1alpha1/validator/attester_test.go

@@ -38,6 +38,7 @@ func TestProposeAttestation(t *testing.T) {
 		OperationNotifier:       (&mock.ChainService{}).OperationNotifier(),
 		TimeFetcher:             chainService,
 		AttestationStateFetcher: chainService,
+		SyncChecker:             &mockSync.Sync{IsSyncing: false},
 	}
 	head := util.NewBeaconBlock()
 	head.Block.Slot = 999
@@ -141,6 +142,7 @@ func TestProposeAttestation_IncorrectSignature(t *testing.T) {
 		P2P:               &mockp2p.MockBroadcaster{},
 		AttPool:           attestations.NewPool(),
 		OperationNotifier: (&mock.ChainService{}).OperationNotifier(),
+		SyncChecker:       &mockSync.Sync{IsSyncing: false},
 	}
 
 	req := util.HydrateAttestation(&ethpb.Attestation{})
@@ -149,6 +151,37 @@ func TestProposeAttestation_IncorrectSignature(t *testing.T) {
 	assert.ErrorContains(t, wanted, err)
 }
 
+func TestProposeAttestation_Syncing(t *testing.T) {
+	attesterServer := &Server{
+		SyncChecker: &mockSync.Sync{IsSyncing: true},
+	}
+
+	req := util.HydrateAttestation(&ethpb.Attestation{})
+	_, err := attesterServer.ProposeAttestation(t.Context(), req)
+	assert.ErrorContains(t, "Syncing to latest head", err)
+	s, ok := status.FromError(err)
+	require.Equal(t, true, ok)
+	assert.Equal(t, codes.Unavailable, s.Code())
+}
+
+func TestProposeAttestationElectra_Syncing(t *testing.T) {
+	attesterServer := &Server{
+		SyncChecker: &mockSync.Sync{IsSyncing: true},
+	}
+
+	req := &ethpb.SingleAttestation{
+		Data: &ethpb.AttestationData{
+			Source: &ethpb.Checkpoint{Root: make([]byte, 32)},
+			Target: &ethpb.Checkpoint{Root: make([]byte, 32)},
+		},
+	}
+	_, err := attesterServer.ProposeAttestationElectra(t.Context(), req)
+	assert.ErrorContains(t, "Syncing to latest head", err)
+	s, ok := status.FromError(err)
+	require.Equal(t, true, ok)
+	assert.Equal(t, codes.Unavailable, s.Code())
+}
+
 func TestGetAttestationData_OK(t *testing.T) {
 	block := util.NewBeaconBlock()
 	block.Block.Slot = 3*params.BeaconConfig().SlotsPerEpoch + 1

changelog/james-prysm_align-atter-pool-apis.md

@@ -0,0 +1,3 @@
+### Changed
+
+- the /eth/v2/beacon/pool/attestations and /eth/v1/beacon/pool/sync_committees now returns a 503 error if the node is still syncing, the rest api is also working in a similar process to gRPC broadcasting immediately now.