Hi folks,
I found today a key problem with the metrics gathering in the 2.6 branch of Juju.
If you have controllers where you are gathering metrics automatically and hooked up to prometheus, please avoid 2.6 until 2.6.4 is released next week. Otherwise you are likely to have your controllers panicing and restarting every time you try.
See bug #1831836 [2.6] controller panics collecting metrics.