Ensure queries are closed in API calls

Signed-off-by: beorn7 <beorn@grafana.com>

web/api/v1/api.go

@@ -317,7 +317,7 @@ func (api *API) options(r *http.Request) apiFuncResult {
 	return apiFuncResult{nil, nil, nil, nil}
 }
 
-func (api *API) query(r *http.Request) apiFuncResult {
+func (api *API) query(r *http.Request) (result apiFuncResult) {
 	ts, err := parseTimeParam(r, "time", api.now())
 	if err != nil {
 		return apiFuncResult{nil, &apiError{errorBadData, err}, nil, nil}
@@ -340,6 +340,14 @@ func (api *API) query(r *http.Request) apiFuncResult {
 		err = errors.Wrapf(err, "invalid parameter 'query'")
 		return apiFuncResult{nil, &apiError{errorBadData, err}, nil, nil}
 	}
+	// From now on, we must only return with a finalizer in the result (to
+	// be called by the caller) or call qry.Close ourselves (which is
+	// required in the case of a panic).
+	defer func() {
+		if result.finalizer == nil {
+			qry.Close()
+		}
+	}()
 
 	ctx = httputil.ContextFromRequest(ctx, r)
 
@@ -361,7 +369,7 @@ func (api *API) query(r *http.Request) apiFuncResult {
 	}, nil, res.Warnings, qry.Close}
 }
 
-func (api *API) queryRange(r *http.Request) apiFuncResult {
+func (api *API) queryRange(r *http.Request) (result apiFuncResult) {
 	start, err := parseTime(r.FormValue("start"))
 	if err != nil {
 		err = errors.Wrapf(err, "invalid parameter 'start'")
@@ -412,6 +420,14 @@ func (api *API) queryRange(r *http.Request) apiFuncResult {
 	if err != nil {
 		return apiFuncResult{nil, &apiError{errorBadData, err}, nil, nil}
 	}
+	// From now on, we must only return with a finalizer in the result (to
+	// be called by the caller) or call qry.Close ourselves (which is
+	// required in the case of a panic).
+	defer func() {
+		if result.finalizer == nil {
+			qry.Close()
+		}
+	}()
 
 	ctx = httputil.ContextFromRequest(ctx, r)
 
@@ -464,7 +480,7 @@ func (api *API) labelNames(r *http.Request) apiFuncResult {
 	return apiFuncResult{names, nil, warnings, nil}
 }
 
-func (api *API) labelValues(r *http.Request) apiFuncResult {
+func (api *API) labelValues(r *http.Request) (result apiFuncResult) {
 	ctx := r.Context()
 	name := route.Param(ctx, "name")
 
@@ -475,7 +491,14 @@ func (api *API) labelValues(r *http.Request) apiFuncResult {
 	if err != nil {
 		return apiFuncResult{nil, &apiError{errorExec, err}, nil, nil}
 	}
-
+	// From now on, we must only return with a finalizer in the result (to
+	// be called by the caller) or call q.Close ourselves (which is required
+	// in the case of a panic).
+	defer func() {
+		if result.finalizer == nil {
+			q.Close()
+		}
+	}()
 	closer := func() {
 		q.Close()
 	}