fix : queue could be blocked

[SkyTNT]

Description

Surround the code in gradio.queue.Queue.process_event with try...finally... to ensure that the processed events in the queue are cleared to avoid the queue being blocked.

Closes: #2261

Checklist:

• I have performed a self-review of my own code
• My code follows the style guidelines of this project
• I have commented my code in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes

[freddyaboulton]

It's hard to know what the best solution is since we don't have a reproducer. However, looking at the code for the Response class, the json_response_data is not set only if there is an exception raised while sending the request. Given that, I wonder if the better solution is to check whether response.is_valid() or response.has_exception prior to accessing the JSON and if it is not valid, send the following message

{"msg": "process_completed",
  "output": {"error": str(response.exception)}
 "success": False
 }

What do you think @aliabid94 @SkyTNT

[SkyTNT]

Sounds good. I think we also need to raise response.exception

[freddyaboulton]

Thank you for the contribution @SkyTNT ! We don't need to raise an exception as the front-end will automatically raise it for us. I added some unit tests too.

[nttstar]

Hello, when to update PyPI package to include this PR? It's very critical.

[abidlabs]

Hi @nttstar we should have a release out on Monday or Tuesday, but in the meantime you can try the beta release gradio==3.4b3

[liminghao1630]

Still exist in 3.27.0 @freddyaboulton

2023-04-24 15:39:59,997 - asyncio - ERROR - Task exception was never retrieved
future: <Task finished name='xnedbjj03d_1' coro=<Queue.process_events() done, defined at /Users/drhaogod/miniconda3/envs/daas/lib/python3.10/site-packages/gradio/queueing.py:343> exception=AttributeError("'AsyncRequest' object has no attribute '_json_response_data'")>
Traceback (most recent call last):
  File "/Users/drhaogod/miniconda3/envs/daas/lib/python3.10/site-packages/gradio/queueing.py", line 370, in process_events
    while response.json.get("is_generating", False):
  File "/Users/drhaogod/miniconda3/envs/daas/lib/python3.10/site-packages/gradio/utils.py", line 696, in json
    return self._json_response_data
AttributeError: 'AsyncRequest' object has no attribute '_json_response_data'

python -c "import gradio; print(gradio.__version__)"
3.27.0

[freddyaboulton]

How can we reproduce @liminghao1630 ?