[SOLVED] Uncatched exception in a function forces sync execution to wait till timeout to receive 500

For example the first one is just for bad json,
And you can try to send bad json to the function to see this error.

Also,
When you're executing this function what is happening?

what do you mean by higher level? After completing runZoneGuarded (finishes also after throw) response.body gettter should throw and error should be catched by the last catch braces

I see crash stacktrace in runtime container
but executor container is waiting till timeout

ok I found it

Okay,
So let's summarized,

These two exceptions has nothing to do with your server code

    } on FormatException catch (_) {
      return shelf.Response(500, body: jsonEncode({
        'stderr': 'Unable to properly load request body',
        'stdout': userLogs.join('\n')
      }), headers: headers);
    } catch (e) {
      return shelf.Response(500, body: jsonEncode({
        'stderr': e.toString(),
        'stdout': userLogs.join('\n'),
      }), headers: headers);
    }

They can be run only if the errro is before your code.

Your code is being executed inside a zone

      await runZonedGuarded(
        () async {
          await user_code.start(request, response);
        },
        (e, stackTrace) => print('$e $stackTrace'),
        zoneSpecification: ZoneSpecification(
          print: (Zone self, ZoneDelegate parent, Zone zone, String line) {
            userLogs.add(line);
          },
        ),
      );

So all of the exceptions made inside the function will be caught by the zone. and then they will be printed out

(e, stackTrace) => print('$e $stackTrace'),

While your output will be added to userLogs object.

Then, after your function as complete - in your case due to exception, then these lines will run

return shelf.Response.ok(
 jsonEncode({
   "response": response.body,
   "stdout": userLogs.join('\n'),
   "stderr": ""
  }),
 headers: headers);

So you can see that the shelf.Response.ok is sending the the response body

Which in your case is empty

this could be problem only with dart runtime, I will confirm that in js today

but consider this code

Then you shouldn't see this one

 print('error outside $e');

this prints:
error inside Instance of 'Error'

Exactly

so this stuck because of this zone

and response is never send back

And yes it's probably will be only in dart due to the way of the server runtime

The reason they use zone is to be able to collect the output of the user

 print: (Zone self, ZoneDelegate parent, Zone zone, String line) {
  userLogs.add(line);
 },

sure, but in the documentation this is described:

That's why the response is being return after the zone.
All the await are inside, and the return is outside.

just confirmed that works as expected on node runtime

Thanks for support, I will create issue in open runtimes repository

https://github.com/open-runtimes/open-runtimes/issues/174

[SOLVED] Uncatched exception in a function forces sync execution to wait till timeout to receive 500

this is fixed in https://github.com/open-runtimes/open-runtimes/pull/136