Every expired group will raise RuntimeError

[nikita-davydov]

This code will raise error every time if if channels[other_key] < now is True.
I fixed it by raise group_expiry param in the config.

[nikita-davydov]

I have created pull request to fix it
#19

[adamhooper]

Thank you for reporting this error -- and thank you for the pull request!

As documented in README.rst, you were probably right to increase group_expiry. The setting and default only exist because the Channel Layer Specification requires it.

After thinking on it for a while, I've developed the opinion that the spec is wrong. I've filed django/channels#1371 to nix group_expiry from the Channel Layer Specification. I don't see a good reason to expire connections.

... but let me ask you, @ndavydovdev: how did you encounter this bug? Do you actually want groups to expire? If so, why?

[nikita-davydov]

@adamhooper Thank you for your response! We have the system which manages user sessions and when the user stays in the one session(one group, one connection) a long time -> his group expires -> got this error. I think nobody uses standard group_expiry or people fix this error by increasing to one year as recommended. in fact, this code will never work properly and if somebody wants to use this group_expiry with very small error, this person will get this every time

[adamhooper]

Awesome -- that's what I figured. Thanks for confirming.

I'll merge your pull request (and add a unit test). The expected result will be: the subscription disappears and nothing else breaks.

I'll also warn users on connect, if they're using the default value of group_expiry, to increase it. This advocacy may help change the specification.

[adamhooper]

I still haven't added a warning. I was waiting on Django-channels devs for feedback on the spec. I still haven't heard back....

[adamhooper]

... actually, come to think of it ... I'm going to disable this feature entirely. I don't think any user wants finite group_expiry. I consider it an error in the spec.