only install requirements you use

[Richard Hawkins]

A vanilla install of Swift should not install libraries that are not used. It would be nice to have a system of creating requirement files per capability so that an operator is not forced to install all the dependencies for all capabilities/middleware that gets added to the core Swift project.

[Tim Burke (1-tim-z)]

Which ones are semi-optional and which are actually required?

It looks like dnspython(3) is only necessary if you intend to use the cname_lookup middleware.

PyECLib shouldn't be strictly necessary unless you're using an EC storage policy, but I think it's currently too tightly coupled to just skip it entirely.

I think everything else really is required. I might be missing something, though; feel free to correct me.

[Richard Hawkins (richard-hawkins)]

Tim: Just for clarity, I didn't intend for this to be treated as a "bug", this was meant to be one of the new WISHLIST things, but I didn't have permissions to set the importance to "WISHLIST". So I am really just trying to start a discussion about it to see what the community thinks about it.

Right now PyECLib is the big one, if an operator has no interest in deploying EC, then I think it should be designed such that you don't have to have PyECLib installed.

I was also thinking about this from a future perspective. It seems like there is interest to get things added to the middleware within Swift's code base. For example the proposal to add zeromq middleware to Swift in a previous meeting. If there was a system in place to where this could have it's own dependencies, I would less hesitant to resist adding it.

[Thiago da Silva (thiagodasilva)]

I'm trying to think how much of this bug can be attributed to what can be done in Swift and how much just depends on how packagers. I'd like to think (and maybe I'm wrong) that most users install from packages as opposed to install from source, so I'm really not sure how much this is relevant to the Swift source.