Use lxc clone on trusty

Use lxc clone on trusty

This branch speeds up lxc containers for the local
provider only by creating a template as needed that
persists between environments, and this template is
then used as a basis for the machines created in the
environment using lxc-clone.

If /var/lib/lxc is a btrfs filesystem, the containers
use btrfs snapshots.  If not, the containers are
created using aufs snapshots.

In addition to this, the apt-get update/upgrade step
is skipped during cloud-init for the cloned machines.

Since the testing required a go routine to shut down
the template container, the mock containers had to be
made go routine safe for the state checking.

Certain extra info was also added for the mock containers,
being the config file and console log.

https://code.launchpad.net/~thumper/juju-core/fast-lxc-no-apt-upgrade/+merge/210536

Requires: https://code.launchpad.net/~thumper/juju-core/update-golxc-version/+merge/210492

(do not edit description out of merge proposal)

[thumper, 2014-03-12 04:59:07]

Please take a look.

[wallyworld, 2014-03-12 05:42:24]

I'm not fully across the finer details about lxc cloning. I think this looks
good. Perhaps a little more test coverage though. Specifically:
1. EnsureCloneTemplate behaves correctly if called when a template already
exists
2. The cloud init contents are devoid of apt stuff

https://codereview.appspot.com/74370044/diff/1/container/lxc/lxc.go
File container/lxc/lxc.go (right):

https://codereview.appspot.com/74370044/diff/1/container/lxc/lxc.go#newcode92
container/lxc/lxc.go:92: if conf["use-clone"] == "true" {
Is there a helper function for str -> bool?

https://codereview.appspot.com/74370044/diff/1/container/lxc/lxc_test.go
File container/lxc/lxc_test.go (right):

https://codereview.appspot.com/74370044/diff/1/container/lxc/lxc_test.go#newc...
container/lxc/lxc_test.go:165: func (s *LxcSuite) AssertEvent(c *gc.C, event
mock.Event, expected mock.Action, id string) {
does this need to be exported?

https://codereview.appspot.com/74370044/diff/1/container/lxc/lxc_test.go#newc...
container/lxc/lxc_test.go:203: c.Assert(template.Name(), gc.Equals, name)
Should we be checking (some key aspects of) the contents of the template?

[sidnei.da.silva, 2014-03-12 08:31:38]

https://codereview.appspot.com/74370044/diff/1/container/lxc/clonetemplate.go
File container/lxc/clonetemplate.go (right):

https://codereview.appspot.com/74370044/diff/1/container/lxc/clonetemplate.go...
container/lxc/clonetemplate.go:142: if backingFilesystem == Btrfs {
I find it odd that backingFilesystem is special-cased for btrfs, since the
version of lxc in trusty has support for picking the right backing filesystem if
-Bbest is specified, which would work for either btrfs or lvm thin provisioning.

[thumper, 2014-03-13 02:12:27]

Please take a look.

https://codereview.appspot.com/74370044/diff/1/container/lxc/clonetemplate.go
File container/lxc/clonetemplate.go (right):

https://codereview.appspot.com/74370044/diff/1/container/lxc/clonetemplate.go...
container/lxc/clonetemplate.go:142: if backingFilesystem == Btrfs {
On 2014/03/12 08:31:38, sidnei.da.silva wrote:
> I find it odd that backingFilesystem is special-cased for btrfs, since the
> version of lxc in trusty has support for picking the right backing filesystem
if
> -Bbest is specified, which would work for either btrfs or lvm thin
provisioning.

man lxc-create doesn't show this.

Post chat: yes -B best does exist, but not documented.  However, it looks for
the following in order: "btrfs", "zfs", "lvm", "dir".  Since we have no easy way
to determine when to use "aufs" if we are allowing "best", it is easier to be
explicit in our support with btrfs now, and have all others use aufs.
I'll talk with hallyn

https://codereview.appspot.com/74370044/diff/1/container/lxc/lxc.go
File container/lxc/lxc.go (right):

https://codereview.appspot.com/74370044/diff/1/container/lxc/lxc.go#newcode92
container/lxc/lxc.go:92: if conf["use-clone"] == "true" {
On 2014/03/12 05:42:25, wallyworld wrote:
> Is there a helper function for str -> bool?

Yes there is. Using it now.

https://codereview.appspot.com/74370044/diff/1/container/lxc/lxc_test.go
File container/lxc/lxc_test.go (right):

https://codereview.appspot.com/74370044/diff/1/container/lxc/lxc_test.go#newc...
container/lxc/lxc_test.go:165: func (s *LxcSuite) AssertEvent(c *gc.C, event
mock.Event, expected mock.Action, id string) {
On 2014/03/12 05:42:25, wallyworld wrote:
> does this need to be exported?

No it doesn't, but it fits with the other Assert statements.

Since "exporting" a test function has no meaning, I went with consistency.

https://codereview.appspot.com/74370044/diff/1/container/lxc/lxc_test.go#newc...
container/lxc/lxc_test.go:203: c.Assert(template.Name(), gc.Equals, name)
On 2014/03/12 05:42:25, wallyworld wrote:
> Should we be checking (some key aspects of) the contents of the template?

We could make sure that it isn't autostarting nor mounting the logdir by looking
at the config file.  Worth it?

[wallyworld, 2014-03-13 02:47:59]

LGTM. Let's get this landed, but I'd still like to see tests that the template
doesn't start etc.