Re: "Squid" failed to cache from FTP sites that does not support RESUME

Squid does not parse directory listings to find modification times, is
uses the MDTM FTP command and if that fails it relies on refresh_pattern
settings.

The current recommended refresh_pattern settings to allow caching of FTP
objects from servers not supporting MDTM and Gopher objects is:
refresh_pattern ^ftp: 1440 20% 10080
refresh_pattern ^gopher: 1440 0% 1440

Squid versions prior to Squid 2.2 got away without this refresh pattern
due to a silly bug where FTP objects was modified "infinitely" ago if
MDTM isn't supported.

FTP and GOPHER are about the only refresh_pattern cases where a min age
>0 is safe and justified.

--
Henrik Nordstrom
Spare time Squid hacker
Dave J Woolley wrote:
> 
> > I think so. I _have_ seen this sort of behaviour before. I can think of
> > three possible causes:
> >
>         I still think that a directory listing format that it
>         can't parse is a real possibility; although I think there
>         are still some Unix ftpd's that don't support the
>         REST <byte-offset> hack, you are more likely to find
>         them on non-Unix systems, either because the system doesn't
>         have the simple Unix model of file structures (VMS?, IBM
>         mainframes) or because the feature was missed out in an
>         attempt to get to market quickly.
> 
>         Unless it can parse the directory listing, it can't
>         get a useable last modified date.