[BCF-3381] - Add LatestHead to ChainService

pkg/loop/internal/pb/relayer.proto

@@ -5,6 +5,7 @@ option go_package = "github.com/smartcontractkit/chainlink-common/pkg/loop/inter
 package loop;
 
 import "google/protobuf/empty.proto";
+import "contract_reader.proto";
 
 service PluginRelayer {
   rpc NewRelayer (NewRelayerRequest) returns (NewRelayerReply) {}
@@ -46,6 +47,7 @@ service Relayer {
   rpc NewConfigProvider (NewConfigProviderRequest) returns (NewConfigProviderReply) {}
   rpc NewPluginProvider (NewPluginProviderRequest) returns (NewPluginProviderReply) {}
 
+  rpc LatestHead (LatestHeadRequest) returns (LatestHeadReply) {}
   rpc GetChainStatus (GetChainStatusRequest) returns (GetChainStatusReply) {}
   rpc ListNodeStatuses (ListNodeStatusesRequest) returns (ListNodeStatusesReply) {}
   rpc Transact (TransactionRequest) returns (google.protobuf.Empty) {}
@@ -108,6 +110,13 @@ message NewConfigProviderReply {
   uint32 configProviderID = 1;
 }
 
+message LatestHeadRequest {}
+
+// LatestHeadReply has return arguments for [github.com/smartcontractkit/chainlink-common/pkg/loop.Relayer.LatestHeadReply].
+message LatestHeadReply {
+  Head head = 1;
+}
+
 message GetChainStatusRequest {}
 
 // ChainStatusReply has return arguments for [github.com/smartcontractkit/chainlink-common/pkg/loop.Relayer.ChainStatus].

pkg/loop/internal/relayer/relayer.go

@@ -304,6 +304,19 @@ func (r *relayerClient) NewLLOProvider(ctx context.Context, rargs types.RelayArg
 	return nil, fmt.Errorf("llo provider not supported: %w", errors.ErrUnsupported)
 }
 
+func (r *relayerClient) LatestHead(ctx context.Context) (types.Head, error) {
+	reply, err := r.relayer.LatestHead(ctx, &pb.LatestHeadRequest{})
+	if err != nil {
+		return types.Head{}, err
+	}
+
+	return types.Head{
+		Identifier: reply.Head.Identifier,
+		Hash:       reply.Head.Hash,
+		Timestamp:  reply.Head.Timestamp,
+	}, nil
+}
+
 func (r *relayerClient) GetChainStatus(ctx context.Context) (types.ChainStatus, error) {
 	reply, err := r.relayer.GetChainStatus(ctx, &pb.GetChainStatusRequest{})
 	if err != nil {
@@ -657,6 +670,21 @@ func (r *relayerServer) newCommitProvider(ctx context.Context, relayArgs types.R
 	return id, err
 }
 
+func (r *relayerServer) LatestHead(ctx context.Context, _ *pb.LatestHeadRequest) (*pb.LatestHeadReply, error) {
+	head, err := r.impl.LatestHead(ctx)
+	if err != nil {
+		return nil, err
+	}
+
+	return &pb.LatestHeadReply{
+		Head: &pb.Head{
+			Identifier: head.Identifier,
+			Hash:       head.Hash,
+			Timestamp:  head.Timestamp,
+		},
+	}, nil
+}
+
 func (r *relayerServer) GetChainStatus(ctx context.Context, request *pb.GetChainStatusRequest) (*pb.GetChainStatusReply, error) {
 	chain, err := r.impl.GetChainStatus(ctx)
 	if err != nil {

pkg/loop/internal/relayer/test/relayer.go

@@ -233,6 +233,10 @@ func (s staticPluginRelayer) NewLLOProvider(ctx context.Context, r types.RelayAr
 	return nil, errors.New("not implemented")
 }
 
+func (s staticPluginRelayer) LatestHead(ctx context.Context) (types.Head, error) {
+	return types.Head{}, errors.New("not implemented")
+}
+
 func (s staticPluginRelayer) GetChainStatus(ctx context.Context) (types.ChainStatus, error) {
 	return s.chainStatus, nil
 }

pkg/loop/relayer_service.go

@@ -76,6 +76,13 @@ func (r *RelayerService) NewLLOProvider(ctx context.Context, rargs types.RelayAr
 	return r.Service.NewLLOProvider(ctx, rargs, pargs)
 }
 
+func (r *RelayerService) LatestHead(ctx context.Context) (types.Head, error) {
+	if err := r.WaitCtx(ctx); err != nil {
+		return types.Head{}, err
+	}
+	return r.Service.LatestHead(ctx)
+}
+
 func (r *RelayerService) GetChainStatus(ctx context.Context) (types.ChainStatus, error) {
 	if err := r.WaitCtx(ctx); err != nil {
 		return types.ChainStatus{}, err

pkg/types/relayer.go

@@ -81,6 +81,8 @@ type NodeStatus struct {
 type ChainService interface {
 	Service
 
+	// LatestHead returns the latest head for the underlying chain.
+	LatestHead(ctx context.Context) (Head, error)
 	// GetChainStatus returns the ChainStatus for this Relayer.
 	GetChainStatus(ctx context.Context) (ChainStatus, error)
 	// ListNodeStatuses returns the status of RPC nodes.