ds-querier: handle response-headers explicitly (#107304)

pkg/registry/apis/query/client/plugin.go

@@ -18,6 +18,7 @@ import (
 	"github.com/grafana/grafana/pkg/plugins"
 	"github.com/grafana/grafana/pkg/registry/apis/query/clientapi"
 	"github.com/grafana/grafana/pkg/services/accesscontrol"
+	"github.com/grafana/grafana/pkg/services/contexthandler"
 	"github.com/grafana/grafana/pkg/services/datasources"
 	"github.com/grafana/grafana/pkg/services/pluginsintegration/adapters"
 	"github.com/grafana/grafana/pkg/services/pluginsintegration/plugincontext"
@@ -109,8 +110,34 @@ func getGrafanaDataSourceSettings(ctx context.Context) (*backend.DataSourceInsta
 	return adapters.ModelToInstanceSettings(ds, decryptFunc)
 }
 
+func (d *pluginClient) QueryData(ctx context.Context, req data.QueryDataRequest) (*clientapi.Response, error) {
+	// middlewares may set response-http-headers through context, so we need to do extra steps
+	// first we create an isolated context to be used by query-data
+	isolatedCtx := contexthandler.CopyWithReqContext(ctx)
+
+	qdr, err := d.innerQueryData(isolatedCtx, req)
+
+	if err != nil {
+		return nil, err
+	}
+
+	rsp := &clientapi.Response{
+		QDR:     qdr,
+		Headers: nil,
+	}
+
+	// we extract the response-headers from the isolated context, and return them explicitly
+	// in the clientapi.Response structure
+	reqCtx := contexthandler.FromContext(isolatedCtx)
+	if reqCtx != nil {
+		rsp.Headers = reqCtx.Resp.Header()
+	}
+
+	return rsp, nil
+}
+
 // ExecuteQueryData implements QueryHelper.
-func (d *pluginClient) QueryData(ctx context.Context, req data.QueryDataRequest) (*backend.QueryDataResponse, error) {
+func (d *pluginClient) innerQueryData(ctx context.Context, req data.QueryDataRequest) (*backend.QueryDataResponse, error) {
 	queries, dsRef, err := data.ToDataSourceQueries(req)
 	if err != nil {
 		return nil, err