Hello I am running into an `asyncio` exception when using `D

Question

Hello I am running into an `asyncio` exception when using `DaskTaskRunner` which leads to tasks hanging and not completing gt

Tim-Oliver · Answer

```13 44 03 390 | INFO | Task run run sofima 57be2d9c 1187 Compute mesh for section test experiment Sample s2098 g1 13 44 07 972 | ERROR | asyncio Exception in callback WorkerThread report result lt Future pendi c62b6bc40 gt gt None StopIteration handle lt Handle WorkerThread report result lt Future pendi c62b6bc40 gt gt None StopIteration gt Traceback most recent call last File tungstenfs scratch gmicro share prefect miniconda3 envs test gfriedri em alignment flows lib python3 9 asyncio events py line 80 in run self context run self callback self args File tungstenfs scratch gmicro share prefect miniconda3 envs test gfriedri em alignment flows lib python3 9 site packages anyio backends asyncio py line 849 in report result future set exception exc TypeError StopIteration interacts badly with generators and cannot be raised into a Future```

Tim-Oliver · Answer

The worker then continues to complete other tasks submitted to it But this failed tasks stays pending indefinitely which blocks the whole flow eventually

Tim-Oliver · Answer

Probably related to this <https github com agronholm anyio pull 477>

Bianca Hoch · Answer

I agree with your assessment that it is related to the error you posted It looks like <https github com tiangolo fastapi issues 966 issuecomment 1305615341|it may be fixed> in a future version of AnyIO ver 4 0 0

Tim-Oliver · Answer

For now I am catching the `StopIteration` exception inside the task and raise a `RunTime` exception Not sure if it makes sense to add this fix to the prefect task until AnyIO 4 0 is released

Kate Weber · Answer

< Tim Oliver> Can you help me understand this solution a little better I m wrapping the call to the function where it dies in `try except` and it s still dying on me

Kate Weber · Answer

This is happening with a relatively straight forward SequentialTaskRunner ```19 17 21 709 | ERROR | asyncio Exception in callback WorkerThread report result lt Future pendi 0fdcc64c0 gt gt None StopIteration handle lt Handle WorkerThread report result lt Future pendi 0fdcc64c0 gt gt None StopIteration gt Traceback most recent call last File usr lib python3 8 asyncio events py line 81 in run self context run self callback self args File big virtualenvs kate tooling lib python3 8 site packages anyio backends asyncio py line 849 in report result future set exception exc TypeError StopIteration interacts badly with generators and cannot be raised into a Future ```

Tim-Oliver · Answer

This is where I am wrapping the function call And here I call the task inside the flow I am using `DaskTaskRunner` and `map` This fix will only fix the issue I had with flows staying in a running state forever It turns the flow into a failed state due to the raised `RunTimeException` PS Please don t judge the code quality This repo is still under heavy construction in at least 5 places