feat(api): Add block height to response headers (#24428)

Co-authored-by: Alex | Interchain Labs <alex@interchainlabs.io>

CHANGELOG.md

@@ -60,6 +60,7 @@ Ref: https://keepachangelog.com/en/1.0.0/
     * x/distribution can now utilize an externally managed community pool. NOTE: this will make the message handlers for FundCommunityPool and CommunityPoolSpend error, as well as the query handler for CommunityPool.
 * (client) [#18101](https://github.com/cosmos/cosmos-sdk/pull/18101) Add a `keyring-default-keyname` in `client.toml` for specifying a default key name, and skip the need to use the `--from` flag when signing transactions.
 * (x/gov) [#24355](https://github.com/cosmos/cosmos-sdk/pull/24355) Allow users to set a custom CalculateVoteResultsAndVotingPower function to be used in govkeeper.Tally.
+* (api) [#24428](https://github.com/cosmos/cosmos-sdk/pull/24428) Add block height to response headers
 
 ### Improvements
 

server/api/server.go

@@ -11,6 +11,7 @@ import (
 
 	tmrpcserver "github.com/cometbft/cometbft/rpc/jsonrpc/server"
 	gateway "github.com/cosmos/gogogateway"
+	"github.com/golang/protobuf/proto" //nolint:staticcheck // grpc-gateway uses deprecated golang/protobuf
 	"github.com/gorilla/handlers"
 	"github.com/gorilla/mux"
 	"github.com/grpc-ecosystem/grpc-gateway/runtime"
@@ -84,11 +85,23 @@ func New(clientCtx client.Context, logger log.Logger, grpcSrv *grpc.Server) *Ser
 			// Custom header matcher for mapping request headers to
 			// GRPC metadata
 			runtime.WithIncomingHeaderMatcher(CustomGRPCHeaderMatcher),
+
+			// extension to set custom response headers
+			runtime.WithForwardResponseOption(customGRPCResponseHeaders),
 		),
 		GRPCSrv: grpcSrv,
 	}
 }
 
+func customGRPCResponseHeaders(ctx context.Context, w http.ResponseWriter, _ proto.Message) error {
+	if meta, ok := runtime.ServerMetadataFromContext(ctx); ok {
+		if values := meta.HeaderMD.Get(grpctypes.GRPCBlockHeightHeader); len(values) == 1 {
+			w.Header().Set(grpctypes.GRPCBlockHeightHeader, values[0])
+		}
+	}
+	return nil
+}
+
 // Start starts the API server. Internally, the API server leverages CometBFT's
 // JSON RPC server. Configuration options are provided via config.APIConfig
 // and are delegated to the CometBFT JSON RPC server.

tests/e2e/distribution/grpc_query_suite.go

@@ -3,6 +3,9 @@ package distribution
 import (
 	"encoding/json"
 	"fmt"
+	"io"
+	"net/http"
+	"strconv"
 
 	"github.com/cosmos/gogoproto/proto"
 	"github.com/stretchr/testify/suite"
@@ -506,3 +509,60 @@ func (s *GRPCQueryTestSuite) TestQueryValidatorCommunityPoolGRPC() {
 		})
 	}
 }
+
+func (s *GRPCQueryTestSuite) TestQueryResponseMeta() {
+	val := s.network.Validators[0]
+	baseURL := val.APIAddress
+	startHeight, err := s.network.LatestHeight()
+	s.Require().NoError(err)
+	// wait 1 block to ensure state is committed
+	s.Require().NoError(s.network.WaitForNextBlock())
+	// when
+	queryURL := fmt.Sprintf("%s/cosmos/distribution/v1beta1/validators/%s", baseURL, val.ValAddress.String())
+	_, headers, err := doRequest(queryURL, map[string]string{})
+	// then latest height is used
+	s.Require().NoError(err)
+	const heightRespHeaderKey = "X-Cosmos-Block-Height"
+	s.Require().Contains(headers, heightRespHeaderKey)
+	gotHeight, err := strconv.Atoi(headers[heightRespHeaderKey][0])
+	s.Require().NoError(err)
+	s.Assert().GreaterOrEqual(gotHeight, int(startHeight))
+
+	// and when called with height header
+	_, headers, err = doRequest(queryURL, map[string]string{"X-Cosmos-Block-Height": strconv.Itoa(int(startHeight))})
+	// then
+	s.Require().NoError(err)
+	s.Require().Contains(headers, heightRespHeaderKey)
+	gotHeight, err = strconv.Atoi(headers[heightRespHeaderKey][0])
+	s.Require().NoError(err)
+	s.Assert().Equal(int(startHeight), gotHeight)
+}
+
+func doRequest(url string, headers map[string]string) ([]byte, http.Header, error) {
+	req, err := http.NewRequest("GET", url, nil)
+	if err != nil {
+		return nil, nil, err
+	}
+
+	client := &http.Client{}
+
+	for key, value := range headers {
+		req.Header.Set(key, value)
+	}
+
+	res, err := client.Do(req)
+	if err != nil {
+		return nil, nil, err
+	}
+
+	body, err := io.ReadAll(res.Body)
+	if err != nil {
+		return nil, nil, err
+	}
+
+	if err = res.Body.Close(); err != nil {
+		return nil, nil, err
+	}
+	fmt.Printf("headers: %v\n", res.Header)
+	return body, res.Header, nil
+}