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From "Xavier Hanin" <xavier.ha...@gmail.com>
Subject Re: machine local repositories and disconnected development
Date Mon, 29 Jan 2007 15:48:09 GMT
On 1/29/07, Eric Crahen <eric.crahen.lists@gmail.com> wrote:
> On 1/29/07, Xavier Hanin <xavier.hanin@gmail.com> wrote:
> >
> > Supporting this kind of graph
> > could be interesting, and what makes it difficult for Ivy is that Ivy
> > heavily relies on its cache mechanism, which makes it impossible to do
> > what you want (i.e. never put anything from your local repository to
> > the cache).
> >
> > This would be a very powerful feature to add. In 2.0, is there any reason
> for the cache to have to be so baked into everything? In otherwords, why not
> implement every resolver and all of the internal management w/ no caching
> what so ever baked in anywhere? Instead all caching is done in a decorator
> fashion by wrapping a caching resolver around any other resolver? In
> otherwords, the core of Ivy only knows about resolvers, no concept of cache
> exists in the heart of Ivy.
>
> It seems to me this would be much more flexible, and it would still be very
> possible to provide the syntactic sugar to make it very simple and even
> seemless to configure these wrappers by default. At the same time, people
> who will use the flexibility have the power to set up chains that might go
> something like.
>
> (logical chain)
>   localresolver
>   cacheresolver
>     httpresolver url="..."
>   cacheresolver
>     httpresolver url="..."
>
> There is no longer any need to have things like useLocal flags. Its already
> expressed that the local resolver is not cached because its just not wrapped
> in a caching resolver.
>
> I think this idiom should be applied to both artifact and metadata
> resolution.
>
> One cool thing about this, is that in this way, since all caching is simply
> a type of resolver we'd provide people who don't like the particular method
> we use to perform caching in the resolver we provide are free to provide
> their own. This would address lots of the issues that have been raised about
> caching, consistency, doing anything remotely fancy with local resolvers -
> right now its very hard to address any of that because caching is not very
> plugable as it stands.
>
> I think the only drawback is that it seems like its harder to configure out
> of the box because most people by default would want to wrap every resolver
> with a cacheresolver - but like I said, this is easily solvable by providing
> some simple syntactic sugar. For instance the simplehttpresolver might be
> the name of an undecorated resolver for power users, and the things named
> httpresolver would simple be an alias for the cacheresolver wrapped around
> the simplehttpresolver (or subclass, whatever is the most sensible choice)

Very interesting idea, indeed. With enough syntactic sugar, it could
even be backward compatible, really interesting. One thing to keep in
mind is to isolate the two parts of the cache: what is cached from
dependency resolvers (basically module descriptors and artifacts) and
what is cached for reusing latest resolve or for a deliver (basically
what lays at the root of the cache in current implementation). This is
worth an issue in JIRA, could you create it?

- Xavier

>
> --
>
> - Eric
>
>

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