Generic-based internal HTTP API (#2626)

* Generic-based internal HTTP API (tested out on a few endpoints in the federation API)

* Add `PerformInvite`

* More tweaks

* Fix metric name

* Fix LookupStateIDs

* Lots of changes to clients

* Some serverside stuff

* Some error handling

* Use paths as metric names

* Revert "Use paths as metric names"

This reverts commit a9323a6a343f5ce6461a2e5bd570fe06465f1b15.

* Namespace metric names

* Remove duplicate entry

* Remove another duplicate entry

* Tweak error handling

* Some more tweaks

* Update error behaviour

* Some more error tweaking

* Fix API path for `PerformDeleteKeys`

* Fix another path

* Tweak federation client proxying

* Fix another path

* Don't return typed nils

* Some more tweaks, not that it makes any difference

* Tweak federation client proxying

* Maybe fix the key backup test

2 files changed, 282 insertions, 612 deletions

diff --git a/federationapi/inthttp/client.go b/federationapi/inthttp/client.go
index 295ddc49..812d3c6d 100644
--- a/federationapi/inthttp/client.go
+++ b/federationapi/inthttp/client.go
@@ -10,7 +10,6 @@ import (
 	"github.com/matrix-org/dendrite/internal/httputil"
 	"github.com/matrix-org/gomatrix"
 	"github.com/matrix-org/gomatrixserverlib"
-	"github.com/opentracing/opentracing-go"
 )
 
 // HTTP paths for the internal HTTP API
@@ -48,7 +47,11 @@ func NewFederationAPIClient(federationSenderURL string, httpClient *http.Client,
 	if httpClient == nil {
 		return nil, errors.New("NewFederationInternalAPIHTTP: httpClient is <nil>")
 	}
-	return &httpFederationInternalAPI{federationSenderURL, httpClient, cache}, nil
+	return &httpFederationInternalAPI{
+		federationAPIURL: federationSenderURL,
+		httpClient:       httpClient,
+		cache:            cache,
+	}, nil
 }
 
 type httpFederationInternalAPI struct {
@@ -63,11 +66,10 @@ func (h *httpFederationInternalAPI) PerformLeave(
 	request *api.PerformLeaveRequest,
 	response *api.PerformLeaveResponse,
 ) error {
-	span, ctx := opentracing.StartSpanFromContext(ctx, "PerformLeaveRequest")
-	defer span.Finish()
-
-	apiURL := h.federationAPIURL + FederationAPIPerformLeaveRequestPath
-	return httputil.PostJSON(ctx, span, h.httpClient, apiURL, request, response)
+	return httputil.CallInternalRPCAPI(
+		"PerformLeave", h.federationAPIURL+FederationAPIPerformLeaveRequestPath,
+		h.httpClient, ctx, request, response,
+	)
 }
 
 // Handle sending an invite to a remote server.
@@ -76,11 +78,10 @@ func (h *httpFederationInternalAPI) PerformInvite(
 	request *api.PerformInviteRequest,
 	response *api.PerformInviteResponse,
 ) error {
-	span, ctx := opentracing.StartSpanFromContext(ctx, "PerformInviteRequest")
-	defer span.Finish()
-
-	apiURL := h.federationAPIURL + FederationAPIPerformInviteRequestPath
-	return httputil.PostJSON(ctx, span, h.httpClient, apiURL, request, response)
+	return httputil.CallInternalRPCAPI(
+		"PerformInvite", h.federationAPIURL+FederationAPIPerformInviteRequestPath,
+		h.httpClient, ctx, request, response,
+	)
 }
 
 // Handle starting a peek on a remote server.
@@ -89,11 +90,10 @@ func (h *httpFederationInternalAPI) PerformOutboundPeek(
 	request *api.PerformOutboundPeekRequest,
 	response *api.PerformOutboundPeekResponse,
 ) error {
-	span, ctx := opentracing.StartSpanFromContext(ctx, "PerformOutboundPeekRequest")
-	defer span.Finish()
-
-	apiURL := h.federationAPIURL + FederationAPIPerformOutboundPeekRequestPath
-	return httputil.PostJSON(ctx, span, h.httpClient, apiURL, request, response)
+	return httputil.CallInternalRPCAPI(
+		"PerformOutboundPeek", h.federationAPIURL+FederationAPIPerformOutboundPeekRequestPath,
+		h.httpClient, ctx, request, response,
+	)
 }
 
 // QueryJoinedHostServerNamesInRoom implements FederationInternalAPI
@@ -102,11 +102,10 @@ func (h *httpFederationInternalAPI) QueryJoinedHostServerNamesInRoom(
 	request *api.QueryJoinedHostServerNamesInRoomRequest,
 	response *api.QueryJoinedHostServerNamesInRoomResponse,
 ) error {
-	span, ctx := opentracing.StartSpanFromContext(ctx, "QueryJoinedHostServerNamesInRoom")
-	defer span.Finish()
-
-	apiURL := h.federationAPIURL + FederationAPIQueryJoinedHostServerNamesInRoomPath
-	return httputil.PostJSON(ctx, span, h.httpClient, apiURL, request, response)
+	return httputil.CallInternalRPCAPI(
+		"QueryJoinedHostServerNamesInRoom", h.federationAPIURL+FederationAPIQueryJoinedHostServerNamesInRoomPath,
+		h.httpClient, ctx, request, response,
+	)
 }
 
 // Handle an instruction to make_join & send_join with a remote server.
@@ -115,12 +114,10 @@ func (h *httpFederationInternalAPI) PerformJoin(
 	request *api.PerformJoinRequest,
 	response *api.PerformJoinResponse,
 ) {
-	span, ctx := opentracing.StartSpanFromContext(ctx, "PerformJoinRequest")
-	defer span.Finish()
-
-	apiURL := h.federationAPIURL + FederationAPIPerformJoinRequestPath
-	err := httputil.PostJSON(ctx, span, h.httpClient, apiURL, request, response)
-	if err != nil {
+	if err := httputil.CallInternalRPCAPI(
+		"PerformJoinRequest", h.federationAPIURL+FederationAPIPerformJoinRequestPath,
+		h.httpClient, ctx, request, response,
+	); err != nil {
 		response.LastError = &gomatrix.HTTPError{
 			Message:      err.Error(),
 			Code:         0,
@@ -135,11 +132,10 @@ func (h *httpFederationInternalAPI) PerformDirectoryLookup(
 	request *api.PerformDirectoryLookupRequest,
 	response *api.PerformDirectoryLookupResponse,
 ) error {
-	span, ctx := opentracing.StartSpanFromContext(ctx, "PerformDirectoryLookup")
-	defer span.Finish()
-
-	apiURL := h.federationAPIURL + FederationAPIPerformDirectoryLookupRequestPath
-	return httputil.PostJSON(ctx, span, h.httpClient, apiURL, request, response)
+	return httputil.CallInternalRPCAPI(
+		"PerformDirectoryLookup", h.federationAPIURL+FederationAPIPerformDirectoryLookupRequestPath,
+		h.httpClient, ctx, request, response,
+	)
 }
 
 // Handle an instruction to broadcast an EDU to all servers in rooms we are joined to.
@@ -148,101 +144,61 @@ func (h *httpFederationInternalAPI) PerformBroadcastEDU(
 	request *api.PerformBroadcastEDURequest,
 	response *api.PerformBroadcastEDUResponse,
 ) error {
-	span, ctx := opentracing.StartSpanFromContext(ctx, "PerformBroadcastEDU")
-	defer span.Finish()
-
-	apiURL := h.federationAPIURL + FederationAPIPerformBroadcastEDUPath
-	return httputil.PostJSON(ctx, span, h.httpClient, apiURL, request, response)
+	return httputil.CallInternalRPCAPI(
+		"PerformBroadcastEDU", h.federationAPIURL+FederationAPIPerformBroadcastEDUPath,
+		h.httpClient, ctx, request, response,
+	)
 }
 
 type getUserDevices struct {
 	S      gomatrixserverlib.ServerName
 	UserID string
-	Res    *gomatrixserverlib.RespUserDevices
-	Err    *api.FederationClientError
 }
 
 func (h *httpFederationInternalAPI) GetUserDevices(
 	ctx context.Context, s gomatrixserverlib.ServerName, userID string,
 ) (gomatrixserverlib.RespUserDevices, error) {
-	span, ctx := opentracing.StartSpanFromContext(ctx, "GetUserDevices")
-	defer span.Finish()
-
-	var result gomatrixserverlib.RespUserDevices
-	request := getUserDevices{
-		S:      s,
-		UserID: userID,
-	}
-	var response getUserDevices
-	apiURL := h.federationAPIURL + FederationAPIGetUserDevicesPath
-	err := httputil.PostJSON(ctx, span, h.httpClient, apiURL, &request, &response)
-	if err != nil {
-		return result, err
-	}
-	if response.Err != nil {
-		return result, response.Err
-	}
-	return *response.Res, nil
+	return httputil.CallInternalProxyAPI[getUserDevices, gomatrixserverlib.RespUserDevices, *api.FederationClientError](
+		"GetUserDevices", h.federationAPIURL+FederationAPIGetUserDevicesPath, h.httpClient,
+		ctx, &getUserDevices{
+			S:      s,
+			UserID: userID,
+		},
+	)
 }
 
 type claimKeys struct {
 	S           gomatrixserverlib.ServerName
 	OneTimeKeys map[string]map[string]string
-	Res         *gomatrixserverlib.RespClaimKeys
-	Err         *api.FederationClientError
 }
 
 func (h *httpFederationInternalAPI) ClaimKeys(
 	ctx context.Context, s gomatrixserverlib.ServerName, oneTimeKeys map[string]map[string]string,
 ) (gomatrixserverlib.RespClaimKeys, error) {
-	span, ctx := opentracing.StartSpanFromContext(ctx, "ClaimKeys")
-	defer span.Finish()
-
-	var result gomatrixserverlib.RespClaimKeys
-	request := claimKeys{
-		S:           s,
-		OneTimeKeys: oneTimeKeys,
-	}
-	var response claimKeys
-	apiURL := h.federationAPIURL + FederationAPIClaimKeysPath
-	err := httputil.PostJSON(ctx, span, h.httpClient, apiURL, &request, &response)
-	if err != nil {
-		return result, err
-	}
-	if response.Err != nil {
-		return result, response.Err
-	}
-	return *response.Res, nil
+	return httputil.CallInternalProxyAPI[claimKeys, gomatrixserverlib.RespClaimKeys, *api.FederationClientError](
+		"ClaimKeys", h.federationAPIURL+FederationAPIClaimKeysPath, h.httpClient,
+		ctx, &claimKeys{
+			S:           s,
+			OneTimeKeys: oneTimeKeys,
+		},
+	)
 }
 
 type queryKeys struct {
 	S    gomatrixserverlib.ServerName
 	Keys map[string][]string
-	Res  *gomatrixserverlib.RespQueryKeys
-	Err  *api.FederationClientError
 }
 
 func (h *httpFederationInternalAPI) QueryKeys(
 	ctx context.Context, s gomatrixserverlib.ServerName, keys map[string][]string,
 ) (gomatrixserverlib.RespQueryKeys, error) {
-	span, ctx := opentracing.StartSpanFromContext(ctx, "QueryKeys")
-	defer span.Finish()
-
-	var result gomatrixserverlib.RespQueryKeys
-	request := queryKeys{
-		S:    s,
-		Keys: keys,
-	}
-	var response queryKeys
-	apiURL := h.federationAPIURL + FederationAPIQueryKeysPath
-	err := httputil.PostJSON(ctx, span, h.httpClient, apiURL, &request, &response)
-	if err != nil {
-		return result, err
-	}
-	if response.Err != nil {
-		return result, response.Err
-	}
-	return *response.Res, nil
+	return httputil.CallInternalProxyAPI[queryKeys, gomatrixserverlib.RespQueryKeys, *api.FederationClientError](
+		"QueryKeys", h.federationAPIURL+FederationAPIQueryKeysPath, h.httpClient,
+		ctx, &queryKeys{
+			S:    s,
+			Keys: keys,
+		},
+	)
 }
 
 type backfill struct {
@@ -250,32 +206,20 @@ type backfill struct {
 	RoomID   string
 	Limit    int
 	EventIDs []string
-	Res      *gomatrixserverlib.Transaction
-	Err      *api.FederationClientError
 }
 
 func (h *httpFederationInternalAPI) Backfill(
 	ctx context.Context, s gomatrixserverlib.ServerName, roomID string, limit int, eventIDs []string,
 ) (gomatrixserverlib.Transaction, error) {
-	span, ctx := opentracing.StartSpanFromContext(ctx, "Backfill")
-	defer span.Finish()
-
-	request := backfill{
-		S:        s,
-		RoomID:   roomID,
-		Limit:    limit,
-		EventIDs: eventIDs,
-	}
-	var response backfill
-	apiURL := h.federationAPIURL + FederationAPIBackfillPath
-	err := httputil.PostJSON(ctx, span, h.httpClient, apiURL, &request, &response)
-	if err != nil {
-		return gomatrixserverlib.Transaction{}, err
-	}
-	if response.Err != nil {
-		return gomatrixserverlib.Transaction{}, response.Err
-	}
-	return *response.Res, nil
+	return httputil.CallInternalProxyAPI[backfill, gomatrixserverlib.Transaction, *api.FederationClientError](
+		"Backfill", h.federationAPIURL+FederationAPIBackfillPath, h.httpClient,
+		ctx, &backfill{
+			S:        s,
+			RoomID:   roomID,
+			Limit:    limit,
+			EventIDs: eventIDs,
+		},
+	)
 }
 
 type lookupState struct {
@@ -283,63 +227,39 @@ type lookupState struct {
 	RoomID      string
 	EventID     string
 	RoomVersion gomatrixserverlib.RoomVersion
-	Res         *gomatrixserverlib.RespState
-	Err         *api.FederationClientError
 }
 
 func (h *httpFederationInternalAPI) LookupState(
 	ctx context.Context, s gomatrixserverlib.ServerName, roomID, eventID string, roomVersion gomatrixserverlib.RoomVersion,
 ) (gomatrixserverlib.RespState, error) {
-	span, ctx := opentracing.StartSpanFromContext(ctx, "LookupState")
-	defer span.Finish()
-
-	request := lookupState{
-		S:           s,
-		RoomID:      roomID,
-		EventID:     eventID,
-		RoomVersion: roomVersion,
-	}
-	var response lookupState
-	apiURL := h.federationAPIURL + FederationAPILookupStatePath
-	err := httputil.PostJSON(ctx, span, h.httpClient, apiURL, &request, &response)
-	if err != nil {
-		return gomatrixserverlib.RespState{}, err
-	}
-	if response.Err != nil {
-		return gomatrixserverlib.RespState{}, response.Err
-	}
-	return *response.Res, nil
+	return httputil.CallInternalProxyAPI[lookupState, gomatrixserverlib.RespState, *api.FederationClientError](
+		"LookupState", h.federationAPIURL+FederationAPILookupStatePath, h.httpClient,
+		ctx, &lookupState{
+			S:           s,
+			RoomID:      roomID,
+			EventID:     eventID,
+			RoomVersion: roomVersion,
+		},
+	)
 }
 
 type lookupStateIDs struct {
 	S       gomatrixserverlib.ServerName
 	RoomID  string
 	EventID string
-	Res     *gomatrixserverlib.RespStateIDs
-	Err     *api.FederationClientError
 }
 
 func (h *httpFederationInternalAPI) LookupStateIDs(
 	ctx context.Context, s gomatrixserverlib.ServerName, roomID, eventID string,
 ) (gomatrixserverlib.RespStateIDs, error) {
-	span, ctx := opentracing.StartSpanFromContext(ctx, "LookupStateIDs")
-	defer span.Finish()
-
-	request := lookupStateIDs{
-		S:       s,
-		RoomID:  roomID,
-		EventID: eventID,
-	}
-	var response lookupStateIDs
-	apiURL := h.federationAPIURL + FederationAPILookupStateIDsPath
-	err := httputil.PostJSON(ctx, span, h.httpClient, apiURL, &request, &response)
-	if err != nil {
-		return gomatrixserverlib.RespStateIDs{}, err
-	}
-	if response.Err != nil {
-		return gomatrixserverlib.RespStateIDs{}, response.Err
-	}
-	return *response.Res, nil
+	return httputil.CallInternalProxyAPI[lookupStateIDs, gomatrixserverlib.RespStateIDs, *api.FederationClientError](
+		"LookupStateIDs", h.federationAPIURL+FederationAPILookupStateIDsPath, h.httpClient,
+		ctx, &lookupStateIDs{
+			S:       s,
+			RoomID:  roomID,
+			EventID: eventID,
+		},
+	)
 }
 
 type lookupMissingEvents struct {
@@ -347,64 +267,38 @@ type lookupMissingEvents struct {
 	RoomID      string
 	Missing     gomatrixserverlib.MissingEvents
 	RoomVersion gomatrixserverlib.RoomVersion
-	Res         struct {
-		Events []gomatrixserverlib.RawJSON `json:"events"`
-	}
-	Err *api.FederationClientError
 }
 
 func (h *httpFederationInternalAPI) LookupMissingEvents(
 	ctx context.Context, s gomatrixserverlib.ServerName, roomID string,
 	missing gomatrixserverlib.MissingEvents, roomVersion gomatrixserverlib.RoomVersion,
 ) (res gomatrixserverlib.RespMissingEvents, err error) {
-	span, ctx := opentracing.StartSpanFromContext(ctx, "LookupMissingEvents")
-	defer span.Finish()
-
-	request := lookupMissingEvents{
-		S:           s,
-		RoomID:      roomID,
-		Missing:     missing,
-		RoomVersion: roomVersion,
-	}
-	apiURL := h.federationAPIURL + FederationAPILookupMissingEventsPath
-	err = httputil.PostJSON(ctx, span, h.httpClient, apiURL, &request, &request)
-	if err != nil {
-		return res, err
-	}
-	if request.Err != nil {
-		return res, request.Err
-	}
-	res.Events = request.Res.Events
-	return res, nil
+	return httputil.CallInternalProxyAPI[lookupMissingEvents, gomatrixserverlib.RespMissingEvents, *api.FederationClientError](
+		"LookupMissingEvents", h.federationAPIURL+FederationAPILookupMissingEventsPath, h.httpClient,
+		ctx, &lookupMissingEvents{
+			S:           s,
+			RoomID:      roomID,
+			Missing:     missing,
+			RoomVersion: roomVersion,
+		},
+	)
 }
 
 type getEvent struct {
 	S       gomatrixserverlib.ServerName
 	EventID string
-	Res     *gomatrixserverlib.Transaction
-	Err     *api.FederationClientError
 }
 
 func (h *httpFederationInternalAPI) GetEvent(
 	ctx context.Context, s gomatrixserverlib.ServerName, eventID string,
 ) (gomatrixserverlib.Transaction, error) {
-	span, ctx := opentracing.StartSpanFromContext(ctx, "GetEvent")
-	defer span.Finish()
-
-	request := getEvent{
-		S:       s,
-		EventID: eventID,
-	}
-	var response getEvent
-	apiURL := h.federationAPIURL + FederationAPIGetEventPath
-	err := httputil.PostJSON(ctx, span, h.httpClient, apiURL, &request, &response)
-	if err != nil {
-		return gomatrixserverlib.Transaction{}, err
-	}
-	if response.Err != nil {
-		return gomatrixserverlib.Transaction{}, response.Err
-	}
-	return *response.Res, nil
+	return httputil.CallInternalProxyAPI[getEvent, gomatrixserverlib.Transaction, *api.FederationClientError](
+		"GetEvent", h.federationAPIURL+FederationAPIGetEventPath, h.httpClient,
+		ctx, &getEvent{
+			S:       s,
+			EventID: eventID,
+		},
+	)
 }
 
 type getEventAuth struct {
@@ -412,135 +306,86 @@ type getEventAuth struct {
 	RoomVersion gomatrixserverlib.RoomVersion
 	RoomID      string
 	EventID     string
-	Res         *gomatrixserverlib.RespEventAuth
-	Err         *api.FederationClientError
 }
 
 func (h *httpFederationInternalAPI) GetEventAuth(
 	ctx context.Context, s gomatrixserverlib.ServerName,
 	roomVersion gomatrixserverlib.RoomVersion, roomID, eventID string,
 ) (gomatrixserverlib.RespEventAuth, error) {
-	span, ctx := opentracing.StartSpanFromContext(ctx, "GetEventAuth")
-	defer span.Finish()
-
-	request := getEventAuth{
-		S:           s,
-		RoomVersion: roomVersion,
-		RoomID:      roomID,
-		EventID:     eventID,
-	}
-	var response getEventAuth
-	apiURL := h.federationAPIURL + FederationAPIGetEventAuthPath
-	err := httputil.PostJSON(ctx, span, h.httpClient, apiURL, &request, &response)
-	if err != nil {
-		return gomatrixserverlib.RespEventAuth{}, err
-	}
-	if response.Err != nil {
-		return gomatrixserverlib.RespEventAuth{}, response.Err
-	}
-	return *response.Res, nil
+	return httputil.CallInternalProxyAPI[getEventAuth, gomatrixserverlib.RespEventAuth, *api.FederationClientError](
+		"GetEventAuth", h.federationAPIURL+FederationAPIGetEventAuthPath, h.httpClient,
+		ctx, &getEventAuth{
+			S:           s,
+			RoomVersion: roomVersion,
+			RoomID:      roomID,
+			EventID:     eventID,
+		},
+	)
 }
 
 func (h *httpFederationInternalAPI) QueryServerKeys(
 	ctx context.Context, req *api.QueryServerKeysRequest, res *api.QueryServerKeysResponse,
 ) error {
-	span, ctx := opentracing.StartSpanFromContext(ctx, "QueryServerKeys")
-	defer span.Finish()
-
-	apiURL := h.federationAPIURL + FederationAPIQueryServerKeysPath
-	return httputil.PostJSON(ctx, span, h.httpClient, apiURL, req, res)
+	return httputil.CallInternalRPCAPI(
+		"QueryServerKeys", h.federationAPIURL+FederationAPIQueryServerKeysPath,
+		h.httpClient, ctx, req, res,
+	)
 }
 
 type lookupServerKeys struct {
 	S           gomatrixserverlib.ServerName
 	KeyRequests map[gomatrixserverlib.PublicKeyLookupRequest]gomatrixserverlib.Timestamp
-	ServerKeys  []gomatrixserverlib.ServerKeys
-	Err         *api.FederationClientError
 }
 
 func (h *httpFederationInternalAPI) LookupServerKeys(
 	ctx context.Context, s gomatrixserverlib.ServerName, keyRequests map[gomatrixserverlib.PublicKeyLookupRequest]gomatrixserverlib.Timestamp,
 ) ([]gomatrixserverlib.ServerKeys, error) {
-	span, ctx := opentracing.StartSpanFromContext(ctx, "LookupServerKeys")
-	defer span.Finish()
-
-	request := lookupServerKeys{
-		S:           s,
-		KeyRequests: keyRequests,
-	}
-	var response lookupServerKeys
-	apiURL := h.federationAPIURL + FederationAPILookupServerKeysPath
-	err := httputil.PostJSON(ctx, span, h.httpClient, apiURL, &request, &response)
-	if err != nil {
-		return []gomatrixserverlib.ServerKeys{}, err
-	}
-	if response.Err != nil {
-		return []gomatrixserverlib.ServerKeys{}, response.Err
-	}
-	return response.ServerKeys, nil
+	return httputil.CallInternalProxyAPI[lookupServerKeys, []gomatrixserverlib.ServerKeys, *api.FederationClientError](
+		"LookupServerKeys", h.federationAPIURL+FederationAPILookupServerKeysPath, h.httpClient,
+		ctx, &lookupServerKeys{
+			S:           s,
+			KeyRequests: keyRequests,
+		},
+	)
 }
 
 type eventRelationships struct {
 	S       gomatrixserverlib.ServerName
 	Req     gomatrixserverlib.MSC2836EventRelationshipsRequest
 	RoomVer gomatrixserverlib.RoomVersion
-	Res     gomatrixserverlib.MSC2836EventRelationshipsResponse
-	Err     *api.FederationClientError
 }
 
 func (h *httpFederationInternalAPI) MSC2836EventRelationships(
 	ctx context.Context, s gomatrixserverlib.ServerName, r gomatrixserverlib.MSC2836EventRelationshipsRequest,
 	roomVersion gomatrixserverlib.RoomVersion,
 ) (res gomatrixserverlib.MSC2836EventRelationshipsResponse, err error) {
-	span, ctx := opentracing.StartSpanFromContext(ctx, "MSC2836EventRelationships")
-	defer span.Finish()
-
-	request := eventRelationships{
-		S:       s,
-		Req:     r,
-		RoomVer: roomVersion,
-	}
-	var response eventRelationships
-	apiURL := h.federationAPIURL + FederationAPIEventRelationshipsPath
-	err = httputil.PostJSON(ctx, span, h.httpClient, apiURL, &request, &response)
-	if err != nil {
-		return res, err
-	}
-	if response.Err != nil {
-		return res, response.Err
-	}
-	return response.Res, nil
+	return httputil.CallInternalProxyAPI[eventRelationships, gomatrixserverlib.MSC2836EventRelationshipsResponse, *api.FederationClientError](
+		"MSC2836EventRelationships", h.federationAPIURL+FederationAPIEventRelationshipsPath, h.httpClient,
+		ctx, &eventRelationships{
+			S:       s,
+			Req:     r,
+			RoomVer: roomVersion,
+		},
+	)
 }
 
 type spacesReq struct {
 	S             gomatrixserverlib.ServerName
 	SuggestedOnly bool
 	RoomID        string
-	Res           gomatrixserverlib.MSC2946SpacesResponse
-	Err           *api.FederationClientError
 }
 
 func (h *httpFederationInternalAPI) MSC2946Spaces(
 	ctx context.Context, dst gomatrixserverlib.ServerName, roomID string, suggestedOnly bool,
 ) (res gomatrixserverlib.MSC2946SpacesResponse, err error) {
-	span, ctx := opentracing.StartSpanFromContext(ctx, "MSC2946Spaces")
-	defer span.Finish()
-
-	request := spacesReq{
-		S:             dst,
-		SuggestedOnly: suggestedOnly,
-		RoomID:        roomID,
-	}
-	var response spacesReq
-	apiURL := h.federationAPIURL + FederationAPISpacesSummaryPath
-	err = httputil.PostJSON(ctx, span, h.httpClient, apiURL, &request, &response)
-	if err != nil {
-		return res, err
-	}
-	if response.Err != nil {
-		return res, response.Err
-	}
-	return response.Res, nil
+	return httputil.CallInternalProxyAPI[spacesReq, gomatrixserverlib.MSC2946SpacesResponse, *api.FederationClientError](
+		"MSC2836EventRelationships", h.federationAPIURL+FederationAPISpacesSummaryPath, h.httpClient,
+		ctx, &spacesReq{
+			S:             dst,
+			SuggestedOnly: suggestedOnly,
+			RoomID:        roomID,
+		},
+	)
 }
 
 func (s *httpFederationInternalAPI) KeyRing() *gomatrixserverlib.KeyRing {
@@ -614,11 +459,10 @@ func (h *httpFederationInternalAPI) InputPublicKeys(
 	request *api.InputPublicKeysRequest,
 	response *api.InputPublicKeysResponse,
 ) error {
-	span, ctx := opentracing.StartSpanFromContext(ctx, "InputPublicKey")
-	defer span.Finish()
-
-	apiURL := h.federationAPIURL + FederationAPIInputPublicKeyPath
-	return httputil.PostJSON(ctx, span, h.httpClient, apiURL, request, response)
+	return httputil.CallInternalRPCAPI(
+		"InputPublicKey", h.federationAPIURL+FederationAPIInputPublicKeyPath,
+		h.httpClient, ctx, request, response,
+	)
 }
 
 func (h *httpFederationInternalAPI) QueryPublicKeys(
@@ -626,9 +470,8 @@ func (h *httpFederationInternalAPI) QueryPublicKeys(
 	request *api.QueryPublicKeysRequest,
 	response *api.QueryPublicKeysResponse,
 ) error {
-	span, ctx := opentracing.StartSpanFromContext(ctx, "QueryPublicKey")
-	defer span.Finish()
-
-	apiURL := h.federationAPIURL + FederationAPIQueryPublicKeyPath
-	return httputil.PostJSON(ctx, span, h.httpClient, apiURL, request, response)
+	return httputil.CallInternalRPCAPI(
+		"QueryPublicKeys", h.federationAPIURL+FederationAPIQueryPublicKeyPath,
+		h.httpClient, ctx, request, response,
+	)
 }
diff --git a/federationapi/inthttp/server.go b/federationapi/inthttp/server.go
index 28e52b32..a8b829a7 100644
--- a/federationapi/inthttp/server.go
+++ b/federationapi/inthttp/server.go
@@ -1,12 +1,14 @@
 package inthttp
 
 import (
+	"context"
 	"encoding/json"
 	"net/http"
 
 	"github.com/gorilla/mux"
 	"github.com/matrix-org/dendrite/federationapi/api"
 	"github.com/matrix-org/dendrite/internal/httputil"
+	"github.com/matrix-org/gomatrixserverlib"
 	"github.com/matrix-org/util"
 )
 
@@ -15,372 +17,180 @@ import (
 func AddRoutes(intAPI api.FederationInternalAPI, internalAPIMux *mux.Router) {
 	internalAPIMux.Handle(
 		FederationAPIQueryJoinedHostServerNamesInRoomPath,
-		httputil.MakeInternalAPI("QueryJoinedHostServerNamesInRoom", func(req *http.Request) util.JSONResponse {
-			var request api.QueryJoinedHostServerNamesInRoomRequest
-			var response api.QueryJoinedHostServerNamesInRoomResponse
-			if err := json.NewDecoder(req.Body).Decode(&request); err != nil {
-				return util.ErrorResponse(err)
-			}
-			if err := intAPI.QueryJoinedHostServerNamesInRoom(req.Context(), &request, &response); err != nil {
-				return util.ErrorResponse(err)
-			}
-			return util.JSONResponse{Code: http.StatusOK, JSON: &response}
-		}),
+		httputil.MakeInternalRPCAPI("FederationAPIQueryJoinedHostServerNamesInRoom", intAPI.QueryJoinedHostServerNamesInRoom),
 	)
+
 	internalAPIMux.Handle(
-		FederationAPIPerformJoinRequestPath,
-		httputil.MakeInternalAPI("PerformJoinRequest", func(req *http.Request) util.JSONResponse {
-			var request api.PerformJoinRequest
-			var response api.PerformJoinResponse
-			if err := json.NewDecoder(req.Body).Decode(&request); err != nil {
-				return util.MessageResponse(http.StatusBadRequest, err.Error())
-			}
-			intAPI.PerformJoin(req.Context(), &request, &response)
-			return util.JSONResponse{Code: http.StatusOK, JSON: &response}
-		}),
+		FederationAPIPerformInviteRequestPath,
+		httputil.MakeInternalRPCAPI("FederationAPIPerformInvite", intAPI.PerformInvite),
 	)
+
 	internalAPIMux.Handle(
 		FederationAPIPerformLeaveRequestPath,
-		httputil.MakeInternalAPI("PerformLeaveRequest", func(req *http.Request) util.JSONResponse {
-			var request api.PerformLeaveRequest
-			var response api.PerformLeaveResponse
-			if err := json.NewDecoder(req.Body).Decode(&request); err != nil {
-				return util.MessageResponse(http.StatusBadRequest, err.Error())
-			}
-			if err := intAPI.PerformLeave(req.Context(), &request, &response); err != nil {
-				return util.ErrorResponse(err)
-			}
-			return util.JSONResponse{Code: http.StatusOK, JSON: &response}
-		}),
-	)
-	internalAPIMux.Handle(
-		FederationAPIPerformInviteRequestPath,
-		httputil.MakeInternalAPI("PerformInviteRequest", func(req *http.Request) util.JSONResponse {
-			var request api.PerformInviteRequest
-			var response api.PerformInviteResponse
-			if err := json.NewDecoder(req.Body).Decode(&request); err != nil {
-				return util.MessageResponse(http.StatusBadRequest, err.Error())
-			}
-			if err := intAPI.PerformInvite(req.Context(), &request, &response); err != nil {
-				return util.ErrorResponse(err)
-			}
-			return util.JSONResponse{Code: http.StatusOK, JSON: &response}
-		}),
+		httputil.MakeInternalRPCAPI("FederationAPIPerformLeave", intAPI.PerformLeave),
 	)
+
 	internalAPIMux.Handle(
 		FederationAPIPerformDirectoryLookupRequestPath,
-		httputil.MakeInternalAPI("PerformDirectoryLookupRequest", func(req *http.Request) util.JSONResponse {
-			var request api.PerformDirectoryLookupRequest
-			var response api.PerformDirectoryLookupResponse
-			if err := json.NewDecoder(req.Body).Decode(&request); err != nil {
-				return util.MessageResponse(http.StatusBadRequest, err.Error())
-			}
-			if err := intAPI.PerformDirectoryLookup(req.Context(), &request, &response); err != nil {
-				return util.ErrorResponse(err)
-			}
-			return util.JSONResponse{Code: http.StatusOK, JSON: &response}
-		}),
+		httputil.MakeInternalRPCAPI("FederationAPIPerformDirectoryLookupRequest", intAPI.PerformDirectoryLookup),
 	)
+
 	internalAPIMux.Handle(
 		FederationAPIPerformBroadcastEDUPath,
-		httputil.MakeInternalAPI("PerformBroadcastEDU", func(req *http.Request) util.JSONResponse {
-			var request api.PerformBroadcastEDURequest
-			var response api.PerformBroadcastEDUResponse
-			if err := json.NewDecoder(req.Body).Decode(&request); err != nil {
-				return util.MessageResponse(http.StatusBadRequest, err.Error())
-			}
-			if err := intAPI.PerformBroadcastEDU(req.Context(), &request, &response); err != nil {
-				return util.ErrorResponse(err)
-			}
-			return util.JSONResponse{Code: http.StatusOK, JSON: &response}
-		}),
+		httputil.MakeInternalRPCAPI("FederationAPIPerformBroadcastEDU", intAPI.PerformBroadcastEDU),
 	)
+
+	internalAPIMux.Handle(
+		FederationAPIPerformJoinRequestPath,
+		httputil.MakeInternalRPCAPI(
+			"FederationAPIPerformJoinRequest",
+			func(ctx context.Context, req *api.PerformJoinRequest, res *api.PerformJoinResponse) error {
+				intAPI.PerformJoin(ctx, req, res)
+				return nil
+			},
+		),
+	)
+
 	internalAPIMux.Handle(
 		FederationAPIGetUserDevicesPath,
-		httputil.MakeInternalAPI("GetUserDevices", func(req *http.Request) util.JSONResponse {
-			var request getUserDevices
-			if err := json.NewDecoder(req.Body).Decode(&request); err != nil {
-				return util.MessageResponse(http.StatusBadRequest, err.Error())
-			}
-			res, err := intAPI.GetUserDevices(req.Context(), request.S, request.UserID)
-			if err != nil {
-				ferr, ok := err.(*api.FederationClientError)
-				if ok {
-					request.Err = ferr
-				} else {
-					request.Err = &api.FederationClientError{
-						Err: err.Error(),
-					}
-				}
-			}
-			request.Res = &res
-			return util.JSONResponse{Code: http.StatusOK, JSON: request}
-		}),
+		httputil.MakeInternalProxyAPI(
+			"FederationAPIGetUserDevices",
+			func(ctx context.Context, req *getUserDevices) (*gomatrixserverlib.RespUserDevices, error) {
+				res, err := intAPI.GetUserDevices(ctx, req.S, req.UserID)
+				return &res, federationClientError(err)
+			},
+		),
 	)
+
 	internalAPIMux.Handle(
 		FederationAPIClaimKeysPath,
-		httputil.MakeInternalAPI("ClaimKeys", func(req *http.Request) util.JSONResponse {
-			var request claimKeys
-			if err := json.NewDecoder(req.Body).Decode(&request); err != nil {
-				return util.MessageResponse(http.StatusBadRequest, err.Error())
-			}
-			res, err := intAPI.ClaimKeys(req.Context(), request.S, request.OneTimeKeys)
-			if err != nil {
-				ferr, ok := err.(*api.FederationClientError)
-				if ok {
-					request.Err = ferr
-				} else {
-					request.Err = &api.FederationClientError{
-						Err: err.Error(),
-					}
-				}
-			}
-			request.Res = &res
-			return util.JSONResponse{Code: http.StatusOK, JSON: request}
-		}),
+		httputil.MakeInternalProxyAPI(
+			"FederationAPIClaimKeys",
+			func(ctx context.Context, req *claimKeys) (*gomatrixserverlib.RespClaimKeys, error) {
+				res, err := intAPI.ClaimKeys(ctx, req.S, req.OneTimeKeys)
+				return &res, federationClientError(err)
+			},
+		),
 	)
+
 	internalAPIMux.Handle(
 		FederationAPIQueryKeysPath,
-		httputil.MakeInternalAPI("QueryKeys", func(req *http.Request) util.JSONResponse {
-			var request queryKeys
-			if err := json.NewDecoder(req.Body).Decode(&request); err != nil {
-				return util.MessageResponse(http.StatusBadRequest, err.Error())
-			}
-			res, err := intAPI.QueryKeys(req.Context(), request.S, request.Keys)
-			if err != nil {
-				ferr, ok := err.(*api.FederationClientError)
-				if ok {
-					request.Err = ferr
-				} else {
-					request.Err = &api.FederationClientError{
-						Err: err.Error(),
-					}
-				}
-			}
-			request.Res = &res
-			return util.JSONResponse{Code: http.StatusOK, JSON: request}
-		}),
+		httputil.MakeInternalProxyAPI(
+			"FederationAPIQueryKeys",
+			func(ctx context.Context, req *queryKeys) (*gomatrixserverlib.RespQueryKeys, error) {
+				res, err := intAPI.QueryKeys(ctx, req.S, req.Keys)
+				return &res, federationClientError(err)
+			},
+		),
 	)
+
 	internalAPIMux.Handle(
 		FederationAPIBackfillPath,
-		httputil.MakeInternalAPI("Backfill", func(req *http.Request) util.JSONResponse {
-			var request backfill
-			if err := json.NewDecoder(req.Body).Decode(&request); err != nil {
-				return util.MessageResponse(http.StatusBadRequest, err.Error())
-			}
-			res, err := intAPI.Backfill(req.Context(), request.S, request.RoomID, request.Limit, request.EventIDs)
-			if err != nil {
-				ferr, ok := err.(*api.FederationClientError)
-				if ok {
-					request.Err = ferr
-				} else {
-					request.Err = &api.FederationClientError{
-						Err: err.Error(),
-					}
-				}
-			}
-			request.Res = &res
-			return util.JSONResponse{Code: http.StatusOK, JSON: request}
-		}),
+		httputil.MakeInternalProxyAPI(
+			"FederationAPIBackfill",
+			func(ctx context.Context, req *backfill) (*gomatrixserverlib.Transaction, error) {
+				res, err := intAPI.Backfill(ctx, req.S, req.RoomID, req.Limit, req.EventIDs)
+				return &res, federationClientError(err)
+			},
+		),
 	)
+
 	internalAPIMux.Handle(
 		FederationAPILookupStatePath,
-		httputil.MakeInternalAPI("LookupState", func(req *http.Request) util.JSONResponse {
-			var request lookupState
-			if err := json.NewDecoder(req.Body).Decode(&request); err != nil {
-				return util.MessageResponse(http.StatusBadRequest, err.Error())
-			}
-			res, err := intAPI.LookupState(req.Context(), request.S, request.RoomID, request.EventID, request.RoomVersion)
-			if err != nil {
-				ferr, ok := err.(*api.FederationClientError)
-				if ok {
-					request.Err = ferr
-				} else {
-					request.Err = &api.FederationClientError{
-						Err: err.Error(),
-					}
-				}
-			}
-			request.Res = &res
-			return util.JSONResponse{Code: http.StatusOK, JSON: request}
-		}),
+		httputil.MakeInternalProxyAPI(
+			"FederationAPILookupState",
+			func(ctx context.Context, req *lookupState) (*gomatrixserverlib.RespState, error) {
+				res, err := intAPI.LookupState(ctx, req.S, req.RoomID, req.EventID, req.RoomVersion)
+				return &res, federationClientError(err)
+			},
+		),
 	)
+
 	internalAPIMux.Handle(
 		FederationAPILookupStateIDsPath,
-		httputil.MakeInternalAPI("LookupStateIDs", func(req *http.Request) util.JSONResponse {
-			var request lookupStateIDs
-			if err := json.NewDecoder(req.Body).Decode(&request); err != nil {
-				return util.MessageResponse(http.StatusBadRequest, err.Error())
-			}
-			res, err := intAPI.LookupStateIDs(req.Context(), request.S, request.RoomID, request.EventID)
-			if err != nil {
-				ferr, ok := err.(*api.FederationClientError)
-				if ok {
-					request.Err = ferr
-				} else {
-					request.Err = &api.FederationClientError{
-						Err: err.Error(),
-					}
-				}
-			}
-			request.Res = &res
-			return util.JSONResponse{Code: http.StatusOK, JSON: request}
-		}),
+		httputil.MakeInternalProxyAPI(
+			"FederationAPILookupStateIDs",
+			func(ctx context.Context, req *lookupStateIDs) (*gomatrixserverlib.RespStateIDs, error) {
+				res, err := intAPI.LookupStateIDs(ctx, req.S, req.RoomID, req.EventID)
+				return &res, federationClientError(err)
+			},
+		),
 	)
+
 	internalAPIMux.Handle(
 		FederationAPILookupMissingEventsPath,
-		httputil.MakeInternalAPI("LookupMissingEvents", func(req *http.Request) util.JSONResponse {
-			var request lookupMissingEvents
-			if err := json.NewDecoder(req.Body).Decode(&request); err != nil {
-				return util.MessageResponse(http.StatusBadRequest, err.Error())
-			}
-			res, err := intAPI.LookupMissingEvents(req.Context(), request.S, request.RoomID, request.Missing, request.RoomVersion)
-			if err != nil {
-				ferr, ok := err.(*api.FederationClientError)
-				if ok {
-					request.Err = ferr
-				} else {
-					request.Err = &api.FederationClientError{
-						Err: err.Error(),
-					}
-				}
-			}
-			for _, event := range res.Events {
-				js, err := json.Marshal(event)
-				if err != nil {
-					return util.MessageResponse(http.StatusInternalServerError, err.Error())
-				}
-				request.Res.Events = append(request.Res.Events, js)
-			}
-			return util.JSONResponse{Code: http.StatusOK, JSON: request}
-		}),
+		httputil.MakeInternalProxyAPI(
+			"FederationAPILookupMissingEvents",
+			func(ctx context.Context, req *lookupMissingEvents) (*gomatrixserverlib.RespMissingEvents, error) {
+				res, err := intAPI.LookupMissingEvents(ctx, req.S, req.RoomID, req.Missing, req.RoomVersion)
+				return &res, federationClientError(err)
+			},
+		),
 	)
+
 	internalAPIMux.Handle(
 		FederationAPIGetEventPath,
-		httputil.MakeInternalAPI("GetEvent", func(req *http.Request) util.JSONResponse {
-			var request getEvent
-			if err := json.NewDecoder(req.Body).Decode(&request); err != nil {
-				return util.MessageResponse(http.StatusBadRequest, err.Error())
-			}
-			res, err := intAPI.GetEvent(req.Context(), request.S, request.EventID)
-			if err != nil {
-				ferr, ok := err.(*api.FederationClientError)
-				if ok {
-					request.Err = ferr
-				} else {
-					request.Err = &api.FederationClientError{
-						Err: err.Error(),
-					}
-				}
-			}
-			request.Res = &res
-			return util.JSONResponse{Code: http.StatusOK, JSON: request}
-		}),
+		httputil.MakeInternalProxyAPI(
+			"FederationAPIGetEvent",
+			func(ctx context.Context, req *getEvent) (*gomatrixserverlib.Transaction, error) {
+				res, err := intAPI.GetEvent(ctx, req.S, req.EventID)
+				return &res, federationClientError(err)
+			},
+		),
 	)
+
 	internalAPIMux.Handle(
 		FederationAPIGetEventAuthPath,
-		httputil.MakeInternalAPI("GetEventAuth", func(req *http.Request) util.JSONResponse {
-			var request getEventAuth
-			if err := json.NewDecoder(req.Body).Decode(&request); err != nil {
-				return util.MessageResponse(http.StatusBadRequest, err.Error())
-			}
-			res, err := intAPI.GetEventAuth(req.Context(), request.S, request.RoomVersion, request.RoomID, request.EventID)
-			if err != nil {
-				ferr, ok := err.(*api.FederationClientError)
-				if ok {
-					request.Err = ferr
-				} else {
-					request.Err = &api.FederationClientError{
-						Err: err.Error(),
-					}
-				}
-			}
-			request.Res = &res
-			return util.JSONResponse{Code: http.StatusOK, JSON: request}
-		}),
+		httputil.MakeInternalProxyAPI(
+			"FederationAPIGetEventAuth",
+			func(ctx context.Context, req *getEventAuth) (*gomatrixserverlib.RespEventAuth, error) {
+				res, err := intAPI.GetEventAuth(ctx, req.S, req.RoomVersion, req.RoomID, req.EventID)
+				return &res, federationClientError(err)
+			},
+		),
 	)
+
 	internalAPIMux.Handle(
 		FederationAPIQueryServerKeysPath,
-		httputil.MakeInternalAPI("QueryServerKeys", func(req *http.Request) util.JSONResponse {
-			var request api.QueryServerKeysRequest
-			var response api.QueryServerKeysResponse
-			if err := json.NewDecoder(req.Body).Decode(&request); err != nil {
-				return util.MessageResponse(http.StatusBadRequest, err.Error())
-			}
-			if err := intAPI.QueryServerKeys(req.Context(), &request, &response); err != nil {
-				return util.ErrorResponse(err)
-			}
-			return util.JSONResponse{Code: http.StatusOK, JSON: &response}
-		}),
+		httputil.MakeInternalRPCAPI("FederationAPIQueryServerKeys", intAPI.QueryServerKeys),
 	)
+
 	internalAPIMux.Handle(
 		FederationAPILookupServerKeysPath,
-		httputil.MakeInternalAPI("LookupServerKeys", func(req *http.Request) util.JSONResponse {
-			var request lookupServerKeys
-			if err := json.NewDecoder(req.Body).Decode(&request); err != nil {
-				return util.MessageResponse(http.StatusBadRequest, err.Error())
-			}
-			res, err := intAPI.LookupServerKeys(req.Context(), request.S, request.KeyRequests)
-			if err != nil {
-				ferr, ok := err.(*api.FederationClientError)
-				if ok {
-					request.Err = ferr
-				} else {
-					request.Err = &api.FederationClientError{
-						Err: err.Error(),
-					}
-				}
-			}
-			request.ServerKeys = res
-			return util.JSONResponse{Code: http.StatusOK, JSON: request}
-		}),
+		httputil.MakeInternalProxyAPI(
+			"FederationAPILookupServerKeys",
+			func(ctx context.Context, req *lookupServerKeys) (*[]gomatrixserverlib.ServerKeys, error) {
+				res, err := intAPI.LookupServerKeys(ctx, req.S, req.KeyRequests)
+				return &res, federationClientError(err)
+			},
+		),
 	)
+
 	internalAPIMux.Handle(
 		FederationAPIEventRelationshipsPath,
-		httputil.MakeInternalAPI("MSC2836EventRelationships", func(req *http.Request) util.JSONResponse {
-			var request eventRelationships
-			if err := json.NewDecoder(req.Body).Decode(&request); err != nil {
-				return util.MessageResponse(http.StatusBadRequest, err.Error())
-			}
-			res, err := intAPI.MSC2836EventRelationships(req.Context(), request.S, request.Req, request.RoomVer)
-			if err != nil {
-				ferr, ok := err.(*api.FederationClientError)
-				if ok {
-					request.Err = ferr
-				} else {
-					request.Err = &api.FederationClientError{
-						Err: err.Error(),
-					}
-				}
-			}
-			request.Res = res
-			return util.JSONResponse{Code: http.StatusOK, JSON: request}
-		}),
+		httputil.MakeInternalProxyAPI(
+			"FederationAPIMSC2836EventRelationships",
+			func(ctx context.Context, req *eventRelationships) (*gomatrixserverlib.MSC2836EventRelationshipsResponse, error) {
+				res, err := intAPI.MSC2836EventRelationships(ctx, req.S, req.Req, req.RoomVer)
+				return &res, federationClientError(err)
+			},
+		),
 	)
+
 	internalAPIMux.Handle(
 		FederationAPISpacesSummaryPath,
-		httputil.MakeInternalAPI("MSC2946SpacesSummary", func(req *http.Request) util.JSONResponse {
-			var request spacesReq
-			if err := json.NewDecoder(req.Body).Decode(&request); err != nil {
-				return util.MessageResponse(http.StatusBadRequest, err.Error())
-			}
-			res, err := intAPI.MSC2946Spaces(req.Context(), request.S, request.RoomID, request.SuggestedOnly)
-			if err != nil {
-				ferr, ok := err.(*api.FederationClientError)
-				if ok {
-					request.Err = ferr
-				} else {
-					request.Err = &api.FederationClientError{
-						Err: err.Error(),
-					}
-				}
-			}
-			request.Res = res
-			return util.JSONResponse{Code: http.StatusOK, JSON: request}
-		}),
+		httputil.MakeInternalProxyAPI(
+			"FederationAPIMSC2946SpacesSummary",
+			func(ctx context.Context, req *spacesReq) (*gomatrixserverlib.MSC2946SpacesResponse, error) {
+				res, err := intAPI.MSC2946Spaces(ctx, req.S, req.RoomID, req.SuggestedOnly)
+				return &res, federationClientError(err)
+			},
+		),
 	)
+
+	// TODO: Look at this shape
 	internalAPIMux.Handle(FederationAPIQueryPublicKeyPath,
-		httputil.MakeInternalAPI("queryPublicKeys", func(req *http.Request) util.JSONResponse {
+		httputil.MakeInternalAPI("FederationAPIQueryPublicKeys", func(req *http.Request) util.JSONResponse {
 			request := api.QueryPublicKeysRequest{}
 			response := api.QueryPublicKeysResponse{}
 			if err := json.NewDecoder(req.Body).Decode(&request); err != nil {
@@ -394,8 +204,10 @@ func AddRoutes(intAPI api.FederationInternalAPI, internalAPIMux *mux.Router) {
 			return util.JSONResponse{Code: http.StatusOK, JSON: &response}
 		}),
 	)
+
+	// TODO: Look at this shape
 	internalAPIMux.Handle(FederationAPIInputPublicKeyPath,
-		httputil.MakeInternalAPI("inputPublicKeys", func(req *http.Request) util.JSONResponse {
+		httputil.MakeInternalAPI("FederationAPIInputPublicKeys", func(req *http.Request) util.JSONResponse {
 			request := api.InputPublicKeysRequest{}
 			response := api.InputPublicKeysResponse{}
 			if err := json.NewDecoder(req.Body).Decode(&request); err != nil {
@@ -408,3 +220,18 @@ func AddRoutes(intAPI api.FederationInternalAPI, internalAPIMux *mux.Router) {
 		}),
 	)
 }
+
+func federationClientError(err error) error {
+	switch ferr := err.(type) {
+	case nil:
+		return nil
+	case api.FederationClientError:
+		return &ferr
+	case *api.FederationClientError:
+		return ferr
+	default:
+		return &api.FederationClientError{
+			Err: err.Error(),
+		}
+	}
+}