[Yum-devel] [PATCH] implement reget=check_timestamp

[Zdenek Pavlas]

>  Ok, so what is the desire for both cases here. Above that we say:
> 
>   reget = None   [None|'simple'|'check_timestamp']
> 
>     whether to attempt to reget a partially-downloaded file.  Reget
>     only applies to .urlgrab and (obviously) only if there is a
>     partially downloaded file.  Reget has two modes:
> 
> ...which implies this is getting extra data or all data, the above
> kind of implies we are getting extra data or nothing (or maybe all data or
> nothing).  But there is a also a problem with the idea...

Yes, the idea is to use reget=simple when we have unique URLs,
and reget=check_timestamp for URLs where content changes over time.

>  This timestamp is going to be one of three things:
> 
> 1. The timestamp we last tried to download FOO, and stopped before we
> got it all.
> 
> 2. The timestamp we last downloaded all of FOO, but didn't have a
> last-modified.
> 
> 3. The timestamp of the server last-modified when we last downloaded
> all of FOO and had a last-modified so urlgrabber used utimes().
> 
> ...which is problematic.

1. This implies timestamp check fails for every partially downloaded
file.  That's why I ignore opts.range unless reget==simple.

2. We'd always reget the whole file (it's a special case of 1).

3. Yes, I rely on utime() being used on completed files only.
Why is that problematic?

> > +                        'If-Modified-Since: %a, %d %b %Y %H:%M:%S

>  This should be If-Range IMO.

If-Range should be used together with a Range header.
Because of 1) we can't use ranges, it's all or nothing.