Our current HTTP frontend fleet (frontend & backend Varnishes for routing & caching, nginx for SSL termination) runs on Ubuntu 12.04 (precise).
Mainly motivated by HTTPS improvements (newer libssl, nginx) and IPsec rollouts, we need to start moving our fleet to a newer platform. Debian jessie is a good candidate for this, as this is the next Wikimedia OS. This work is expected to happen by the end of FY Q3 2015.
For this we'll need to:
[x] Prepare infrastructure for jessie boxes (already done as part of a separate goal)
[x] Upgrade one canary box to jessie (cp1008)
[x] Rebuild custom-made packages for jessie, notably Varnish 3 (jessie ships with 4), varnishkafka; port upstart service files to systemd
[x] Reinstall one server of each type role (text, mobile, upload, bits) in production for live testing
[ ] Make sure that everything works, new kernel in particular.
[ ] Reinstall all servers across all datacenters
Note that related to this, we'll also need the availability of jessie images for Labs so that we can perform tests and so that Beta can keep up with production. For this, the availability of jessie images in Labs, T75592, is a blocker.