Snapd 2.28 breaks the lxc interface

20:55 < jdstrand> niemeyer: hey, stgraber has a stop the line issue I think with lxd and 2.28 regression
20:55 < jdstrand> niemeyer: he can give the details
20:56 < stgraber> niemeyer: with the latest stable core snap update, the "lxd:lxd" interface is now considered invalid, causing anything that would otherwise be connected to it to be dropped
20:57 < stgraber> I just noticed it when the Ubuntu Core server running the backend for the online LXD demo dropped offline, investigating the reason I saw it rebooted an hour ago for a core snap change and lxd-demo-server couldn't 
                  connect to lxd anymore
20:58 < stgraber> as a workaround I just upgraded that server to the edge channel for the core snap which gives me a git build of snapd that includes jdstrand's fix
21:06 < jdstrand> niemeyer: that fix was

@niemeyer @mvo @jdstrand

I hit this through lxd-demo-server but anyone else using the lxd:lxd client interface would hit this.

Thanks for this problem report. We are working on a new 2.28.3 release with the fix from @jdstrand. We also added a new regression test for this in to ensure it won’t happen again. We will also investigate why this escaped our QA. A new core with the fix will be in beta today and pushed to candidate/stable ASAP.

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Sorry for the trouble, @stgraber, and thank you very much for addressing this so quickly, @mvo.

As a general suggestion for everyone working closely with snaps, unless you specifically depend on a different channel, please use candidate as the channel for core in your development machine, by running:

$ snap refresh --candidate core

This will help complementing the usual testing process that snapd always go through.

Please do not use that in production, though.