redis storage backend for shibbolet-sp

[Cantor, Scott]

> What would be the next step to be reviewed and
> incorporated into the mainline Shibboleth-SP? Andras is
> willing to share his work in a patch or pull request. 

While I appreciate the desire and the effort, I wish you'd have asked first.

The SP is for the most part, aside from the occasional bug fix or library update, frozen at this point while we work on a complete rewrite, and any sort of clustering there would be in Java based on the IdP's extension points, nothing in C++.

https://shibboleth.atlassian.net/wiki/spaces/DEV/pages/2981429255/Service+Provider+V4+Redesign

(We would be very happy with a contribution to support Redis on the IdP, which will extend to the SP in the future.)

I don't believe we'd have the cycles to do the work required to pull in such a complex contribution to the legacy code at this point, even were a member to ask. If multiple members push for it, then we'd have to at least consider it but it would be difficult to find the time given the roadmap we have planned.

I would also add that my suggestion would have been to stick with the persistent cookie session recovery feature to address this sort of issue, as it's much simpler in most cases and doesn't require server state.

-- Scott