fallback on bad request proxying (#4566)

Author: StekPerepolnen

ydb/core/viewer/json_autocomplete.h

@@ -425,7 +425,12 @@ class TJsonAutocomplete : public TViewerPipeClient<TJsonAutocomplete> {
     }
 
     void Handle(TEvViewer::TEvViewerResponse::TPtr& ev) {
-        ProxyResult = ev.Release()->Release();
+        if (ev.Get()->Get()->Record.HasAutocompleteResponse()) {
+            ProxyResult = ev.Release()->Release();
+        } else {
+            Direct = true;
+            SendSchemeCacheRequest(); // fallback
+        }
         RequestDone();
     }
 

ydb/core/viewer/json_query.h

@@ -420,7 +420,12 @@ class TJsonQuery : public TViewerPipeClient<TJsonQuery> {
     }
 
     void HandleReply(TEvViewer::TEvViewerResponse::TPtr& ev) {
-        Handle(*(ev.Get()->Get()->Record.MutableQueryResponse()));
+        auto& record = ev.Get()->Get()->Record;
+        if (record.HasQueryResponse()) {
+            Handle(*(ev.Get()->Get()->Record.MutableQueryResponse()));
+        } else {
+            SendKpqProxyRequest(); // fallback
+        }
     }
 
     void HandleReply(NKqp::TEvKqp::TEvAbortExecution::TPtr& ev) {

ydb/core/viewer/json_render.h

@@ -254,7 +254,12 @@ class TJsonRender : public TViewerPipeClient<TJsonRender> {
     }
 
     void Handle(TEvViewer::TEvViewerResponse::TPtr& ev) {
-        HandleRenderResponse(*(ev.Get()->Get()->Record.MutableRenderResponse()));
+        auto& record = ev.Get()->Get()->Record;
+        if (record.HasRenderResponse()) {
+            HandleRenderResponse(*(record.MutableRenderResponse()));
+        } else {
+            SendGraphRequest(); // fallback
+        }
     }
 
     void HandleTimeout() {