[FFmpeg-devel] [PATCH] http: make caching of redirect url optional

[Eran Kornblau]

> > 
> > On Tue, 2 Nov 2021, Eran Kornblau wrote:
> > 
> > > Hi all,
> > >
> > > The attached patch makes the default behavior of caching HTTP redirects optional.
> > 
> > Is caching a redirected URL allowed per the HTTP spec? If not, then no caching should take place, or the caching should be optional, and not the default.
> > 
> From a quick search on this, it seems that browsers by default cache 301 redirects, while 302/307 are not cached by default.
> However, in both cases, the browser is expected to honor any Cache-Control/Expires headers.
> 
> Changing the implementation to imitate the behavior of a browser would be more complex, since currently there is only a single "slot" in the cache.
> For example, if we have a chain of redirects 307->301->200, and we want to cache the 301 but not the 307, we can't really do it.
> Solving this one would require a more complex data structure, and if we add expiration/TTL to the mix, it becomes even more complex...
> 
> Assuming we don't want to add a large chunk of code to handle this, the options I see are - 1. A simple boolean option - as proposed in this patch. We can argue about what the default should be :) but it felt safer to me to have the default behavior as it was before.
> 2. Cache only 301's directly linked to the original URL - e.g. if we have 301->301->307->301->200, we cache only the first 2 redirects.
> My concern here is that this would break/slow down applications that rely on the existing behavior of caching any redirect.
> 

Hi,

Looking for some guidance how to proceed with this...

On one side, we have the minimal alternative of adding an option to the http module (as in the patch I submitted),
on the other side we have the alternative of fully imitating the behavior of a browser - respect cache-control/expires,
and if these headers are missing, default according to status code (301/302/307).
We can also go with something in between - e.g., we can cache 301's that are returned directly from the original url,
and avoid caching any 302/307, as well as 301's that come after a 302/307.

Thank you

Eran

> Any thoughts/suggestions are welcome,
> 
> Thank you,
> 
> Eran
> 
> > Thanks,
> > Marton
> >
>