mstate: all nodes have a lifecycle

mstate: all nodes have a lifecycle

As per Gustavo's proposal[1], all nodes have a lifecycle field used to
avoid race conditions and guarantee a consistent state.

[1] https://lists.ubuntu.com/archives/juju-dev/2012-July/000116.html

https://code.launchpad.net/~aramh/juju-core/mstate-lifecycle/+merge/113276

Requires: https://code.launchpad.net/~aramh/juju-core/mstate-units-subordinate/+merge/113016

(do not edit description out of merge proposal)

[aram, 2012-07-03 20:13:23]

Please take a look.

[niemeyer, 2012-07-03 20:29:24]

That's great. LGTM, assuming the two changes below are pushed on all spots
touched:

https://codereview.appspot.com/6350068/diff/2001/mstate/life/lifecycle.go
File mstate/life/lifecycle.go (right):

https://codereview.appspot.com/6350068/diff/2001/mstate/life/lifecycle.go#new...
mstate/life/lifecycle.go:1: package life
We don't need a package for that. Let's define:

type Life const {
    Alive Life = 1 + iota
    Dying
    Dead
}

Inside mstate itself. It's fine to have this exposed publicly too. In a second
moment we'll have these entities with explicit lifetime control on their
interface.

https://codereview.appspot.com/6350068/diff/2001/mstate/machine.go
File mstate/machine.go (right):

https://codereview.appspot.com/6350068/diff/2001/mstate/machine.go#newcode20
mstate/machine.go:20: LifeCycle  life.Cycle
Seeing this in code, and your suggestion of "life" as a package name, it's nicer
if we call this as Life and "life" (in queries) instead, all over. We know what
that means, and it's short and neat.

[aram, 2012-07-03 20:46:51]

Please take a look.

[aram, 2012-07-04 21:49:48]

Please take a look.

[niemeyer, 2012-07-06 14:28:02]

LGTM

[aram, 2012-07-10 23:50:44]

*** Submitted:

mstate: all nodes have a lifecycle

As per Gustavo's proposal[1], all nodes have a lifecycle field used to
avoid race conditions and guarantee a consistent state.

[1] https://lists.ubuntu.com/archives/juju-dev/2012-July/000116.html

R=niemeyer
CC=
https://codereview.appspot.com/6350068