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metalink support

From: Dr. Peter Poeml <poeml_at_suse.de>
Date: Mon, 7 Apr 2008 14:54:18 +0200

Hi!

You are probably aware of metalinks (http://metalinker.org), and how
they can be used to make downloas from HTTP, FTP and other sources (that
curl handles) better for users, by implementing failover and integrity
checking.

I personally haven't work with metalinks much, so far, but I have
implemented support for them in the openSUSE download redirector [1]
last week, and I think it is a really powerful addition. The redirector
can transparently create metalinks now, like for instance
http://download.opensuse.org/distribution/10.3/iso/dvd/openSUSE-10.3-GM-DVD-i386.iso?metalink
with up-to-date mirrors listed, as it would normally redirect clients
to. With that, we have a really good metalink generator now.

So obviously support in as many download clients as possible seems
desirable, of course.

But there is a special reason that I approach you on this list. The
reason is that the "main user" of download.opensuse.org is the openSUSE
installer (YaST/zypper/libzypp), which is using libcurl to do all the
work.

Since we would like to make downloads more robust, I actually wrote up a
proposal [2] how to implement something on _top_ of libcurl, to achieve
something similar as what can be achieved with metalinks.

In fact, it is an enthralling thought to me that libcurl could
understand and handle metalinks already, because all what I proposed in
[2] would come for free. (Well, free for libzypp that is. :-) But the
interesting thing is that lots of software uses libcurl, so it would all
benefit from such a capability.

For openSUSE, it would be so very beneficial that there is actually a
GSoC project about implementing the proposal from [2]. With metalink
support in libcurl it could be rather something which is generally
useful, though.

There are some ideas being discussed [3] how to handle metalinks more
transparently, which would make them even more easy to use.

What do you think about it? Wouldn't that be a very worthwhile thing?

Thanks,
Peter
[1] http://en.opensuse.org/Build_Service/Redirector
    http://www.poeml.de/~poeml/talks/redirector/
[2] http://en.opensuse.org/Libzypp/Failover
[3] http://groups.google.com/group/metalink-discussion/msg/24792f391b7f975d

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Received on 2008-04-07