cmd/jujud/machineagent: install LXC on start

cmd/jujud/machineagent: install LXC on start

Related to bug #1199913. On startup we will 'apt-get install lxc' if we
need to. This uses the containers/lxc code to detect if we have lxc
available, and if it fails then we request to install it.

I've tested this live, and it does solve the immediate problem.

Also, the test suite still passes because all the things that call
MachineAgent.Run are already using the lxc.TestSuite and so the
containers code "provides" lxc via the MockFactory.

One test we could do is that we try to install lxc if we run
the machine agent (and inject a MockFactory that fails the List
request). But I felt live testing was appropriate for this.

https://code.launchpad.net/~jameinel/juju-core/api-connect-upgrade-1199915/+merge/174207

(do not edit description out of merge proposal)

[jameinel, 2013-07-11 13:53:33]

Please take a look.

[fwereade, 2013-07-11 14:03:11]

https://codereview.appspot.com/10986044/diff/1/cmd/jujud/machine.go
File cmd/jujud/machine.go (right):

https://codereview.appspot.com/10986044/diff/1/cmd/jujud/machine.go#newcode82
cmd/jujud/machine.go:82: log.Errorf("we were unable to install the lxc package,
unable to continue: %v", err)
Quibble quibble waffle waffle, this will break on other platforms. Unbreaks
upgrade for now though, so fair enough.

https://codereview.appspot.com/10986044/diff/1/utils/apt.go
File utils/apt.go (right):

https://codereview.appspot.com/10986044/diff/1/utils/apt.go#newcode18
utils/apt.go:18: //       apt concurrently, we should use that same locking here
We already have that. uniter.go:116

[dimitern, 2013-07-11 14:08:29]

LGTM

https://codereview.appspot.com/10986044/diff/1/cmd/jujud/machine.go
File cmd/jujud/machine.go (right):

https://codereview.appspot.com/10986044/diff/1/cmd/jujud/machine.go#newcode82
cmd/jujud/machine.go:82: log.Errorf("we were unable to install the lxc package,
unable to continue: %v", err)
On 2013/07/11 14:03:11, fwereade wrote:
> Quibble quibble waffle waffle, this will break on other platforms. Unbreaks
> upgrade for now though, so fair enough.

Add TODO describing this please.

[jameinel, 2013-07-11 14:58:57]

Please take a look.

[fwereade, 2013-07-11 15:08:23]

LGTM with verbose warnings; I would *really* appreciate a followup that somehow
tested this situation live, but I'm at a little bit of a loss how to do that
sanely.

https://codereview.appspot.com/10986044/diff/5002/cmd/jujud/upgradevalidation.go
File cmd/jujud/upgradevalidation.go (right):

https://codereview.appspot.com/10986044/diff/5002/cmd/jujud/upgradevalidation...
cmd/jujud/upgradevalidation.go:30: // Note: Should we try to do the install
anyway, just without the lock?
Yeah, I think so. Log a great big warning and see what you can do. If we fail,
we bomb out, and upstart gives us another try; eventually we'll mess with the
unit badly enough that we succeed, I suspect, and then we have a working machine
again... and at least the unit is somewhat user-fixable.

[dimitern, 2013-07-11 15:09:43]

LGTM, just remove a TODO about locks.

https://codereview.appspot.com/10986044/diff/5002/utils/apt.go
File utils/apt.go (right):

https://codereview.appspot.com/10986044/diff/5002/utils/apt.go#newcode17
utils/apt.go:17: // TODO: When we have a unit-level lock to avoid multiple unit
agents running
delete this now?