After switching to latest flask, app timeouts on some requests

[pipozzz]

When I wanted to upgrade from 2.2.x to 2.3.x I encountered problem with timeouts on some requests, without any error log about it.

Any ideas please ? What can cause it?

• Python version: 3.10
• Flask version: 2.3.2
• gunicorn: 20.1.0
• gevent: 22.10.2
• nginx: 1.18.0

[davidism]

It is impossible to say with the lack of information. Be sure to provide a minimal reproducible example.

[pipozzz]

it's very hard to debug, because I see no errors just see that calls timeout, like broken event loop or so. In the frontend I see 499 error codes I think it's because of client connect timeout exceeded. One request is fine another timeouts. Everything started when I switched from 2.2.x to 2.3.x.

here is diff in requirements.txt

diff 2.2.3.txt latest.txt         
30c30
< Flask==2.2.5
---
> Flask==2.3.2
108c108
< Werkzeug==2.2.3
---
> Werkzeug==2.3.4

what else would you need I can provide you.

Thanks in advance.

[pipozzz]

Could you please give me some suggestion how to debug this or so? I'd appreciate any idea.

[cplpearce]

@pipozzz We just recently upgraded from Flask 2.2.2 to latest and I'm experiencing the same issue.

We use the following packages:

• Flask-Bcrypt
• Flask-Cors
• pylint-flask
• flask-session2
• flask-compress

I rolled Flask back to 2.2.2 and the issue has disappeared. I haven't had the time to debug it so I'm sorry I can't offer anything more!

[pipozzz]

I found my problem , It's combination of gunicorn + gevent + latest flask this is not working, I switched to uwsgi + gevent + latest flask and now it works