Graceful Reloading for Schema Changes - UWSGI - Gunicorn?

[Shapath Neupane]

Hello Djangonats,

How do you reload Django script changes with UWSGI? I know `touch-reload` exists with UWSGI however I was looking more into what uwsgi does when the schema(s) in the models change? How do you handle database changes without affecting or rebooting the server? Rebooting UWSGI does not sound like a good idea.

A Load Balancer (HAProxy) ?

More Questions

Does something like that exist in Gunicorn?

Regards,

Shapath.

[Stephen J. Butler]

I'm not familiar with uWSGI. On gunicorn you send it SIGHUP (kill -HUP
pid) and it will reload w/o interrupting requests. Looks like uWSGI
supports something similar:

https://uwsgi-docs.readthedocs.org/en/latest/Management.html#signals-for-controlling-uwsgi

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[Roberto De Ioris]

>
>
> Hello Djangonats,
>
> How do you reload Django script changes with UWSGI? I know `touch-reload

> <http://uwsgi-docs.readthedocs.org/en/latest/Options.html#touch-reload>`

> exists with UWSGI however I was looking more into what uwsgi does when the
> schema(s) in the models change? How do you handle database changes without
> affecting or rebooting the server? Rebooting UWSGI does not sound like a
> good idea.
>
> A Load Balancer (HAProxy) ?
>

> *More Questions*

>
> Does something like that exist in Gunicorn?
>
> Regards,
>
> Shapath.
>
>

The topic is huge and there are dozens of approaches, but basically every
WSGI server requires a new (updated) process address space after code
change
(included schema changes if the model is already loaded into memory).

So, even if it may look "extreme", reloading the whole WSGI server is the
only reliable solution (in fact used by everyone).

If you are scared about potential downtimes check this article:

http://uwsgi-docs.readthedocs.org/en/latest/articles/TheArtOfGracefulReloading.html

But take in account that 99% of the times/cases a simple graceful reload
is more than enough.


--
Roberto De Ioris
http://unbit.com