I appreciate the detailed reply, and the others as well. To address your questions and some of the others:
We can generally pin our entire fleet against whatever we want -- until we can't. One particular (very large, very important) dependency currently requires CentOS 6.5. Go figure.
As much as possible, I want to treat infrastructure as a commodity, so catering to specific versions (even LTR versions) breaks that goal. As another reply notes, if we lock in at Ubuntu 12.04 and it's predictable, that's excellent.
As another mentions, Upstart was easy to get a handle of quickly. As an aside, it bugs me that the (otherwise excellent and detailed) Upstart docs don't seem to mention that all of Upstart is now deprecated. Hence the original confusion! In general I don't want flexibility (not first and foremost), I want simple and consistent.
> One particular (very large, very important) dependency currently requires CentOS 6.5.
What dependency is that? And can you run it in a single-purpose virtual machine, rather than directly on real hardware, to make it easier to manage?
> As much as possible, I want to treat infrastructure as a commodity, so catering to specific versions (even LTR versions) breaks that goal. As another reply notes, if we lock in at Ubuntu 12.04 and it's predictable, that's excellent.
You definitely don't want to cater to specific versions any more than you have to; ideally you want as few versions across your entire fleet as you can. If you could get it down to just CentOS and the latest version of some up-to-date distribution, that would help; if you could make CentOS a virtual machine under that same up-to-date distribution, that's even better, insofar as you can then manage all the physical machines identically.
> As another mentions, Upstart was easy to get a handle of quickly. As an aside, it bugs me that the (otherwise excellent and detailed) Upstart docs don't seem to mention that all of Upstart is now deprecated. Hence the original confusion!
The Upstart docs aren't going to say that Upstart is deprecated. It's more a view of the Linux distribution ecosystem as a whole: the one distribution that primarily drove upstart usage and adoption is switching to systemd, so there won't be further momentum or resources behind upstart in the future. That doesn't make it instantly obsolete, but it does mean that starting a new project today around upstart is a bad idea.
(In fairness, there's one other notable distribution using upstart as well, namely Chrome OS; however, that's a bit of a special case in several ways, and in any case I hope to change that in the future.)
I'm wary of naming the dependency, because it's a vendor's solution and I'm not trying to call them out, but it's their ecosystem of tools and it has to run as the host OS, not virtualized. But all your comments are spot-on, and I appreciate it.
The Upstart thing is just somewhat odd, because it's a Canonical project, and Ubuntu is also Canonical's. At any rate, you're right that it's not immediately lost. But trying to pin against even the long-term releases of Ubuntu seems hopeless. I've been working on upgrading a 12.04 deployment to 14.04. There aren't any features that we're missing in the OS, so it's really only a concern from a security or support perspective. The shop I'm in was already using Ubuntu when I came on, but maybe the lesson here is to migrate to Debian, rather than bother upgrading to the newer Ubuntu release. (Migrating to CentOS would be somewhat more work.)
> The Upstart thing is just somewhat odd, because it's a Canonical project, and Ubuntu is also Canonical's.
That's why they pushed so hard for Debian to use Upstart. Once Debian switched to systemd instead, Canonical announced that they would too.
> The shop I'm in was already using Ubuntu when I came on, but maybe the lesson here is to migrate to Debian, rather than bother upgrading to the newer Ubuntu release.
I'd certainly recommend that myself. Unless you have a hard requirement for an "Enterprise" distribution (RHEL or SLES), I tend to advocate Debian stable rather than Ubuntu LTS, especially on a server.
We can generally pin our entire fleet against whatever we want -- until we can't. One particular (very large, very important) dependency currently requires CentOS 6.5. Go figure.
As much as possible, I want to treat infrastructure as a commodity, so catering to specific versions (even LTR versions) breaks that goal. As another reply notes, if we lock in at Ubuntu 12.04 and it's predictable, that's excellent.
As another mentions, Upstart was easy to get a handle of quickly. As an aside, it bugs me that the (otherwise excellent and detailed) Upstart docs don't seem to mention that all of Upstart is now deprecated. Hence the original confusion! In general I don't want flexibility (not first and foremost), I want simple and consistent.