Containerisation using docker

Tue Apr 30 11:57:18 UTC 2013

Docker is pretty awesome and moving fast but another issue to add is we
need full containers which isn't really docker's goal as it focused more on
an being a flyweight app container.  ie. they don't run init. The
versioning capability is just aufs, though they put it together in a great
user experience, (diffs, sends, snapshots as commits).  The networking
isn't quite as flexible as lxc its port/firewall management is pretty
limited, we'd want the flexibility to physically map a net device to a
container. We should be able to import our cloud-images in directly, but i
ran into some issues which they mentioned as ext4 issue (albeit that was
two weeks ago).

An alternative to consider is go liblxc bindings, which are pretty
lightweight and closer to the 'metal'.. https://github.com/caglar10ur/lxc

cheers,

Kapil

On Tue, Apr 30, 2013 at 1:21 AM, Tim Penhey <tim.penhey at canonical.com>wrote:

> Hi all,
>
> I've spent a little time looking into docker.  Not much time at the
> moment, but I thought I'd share my thoughts so far.
>
> The promise seems awesome, but there are some interesting caveats.
>
> Docker wraps LXC and makes a nicer high level API.  I've been reading
> the docs, going through their examples, and chatting on the #docker IRC
> channel.
>
> I'll start with the good news:
>  * Written in Go, so fits our current language of choice
>  * Ubuntu is their default supported platform, but they also work on
> Arch, Windows, MacOS, and Amazon EC2 (I'm wondering if their last bullet
> point is really referring to the the default Amazon linux, not EC2 as a
> whole).
>  * Since it uses LXC, it gives us the isolation we would want for
> installing multiple units on a single machine.
>  * Containers can have snapshots taken and moved between machines
> (limited by architecture).  Consider the idea of someone deploying
> everything to one machine to try things out, then moving units to
> individual machines easily.  Obviously we'd have to make sure all the
> relationships get updated properly, but the potential it there.  Another
> potential would be using docker for the local provider, and moving the
> deployed units to another provider (ec2 or openstack).  Obviously again,
> there would be quite a bit of juju magic needed to make sure the state
> is kept up to date properly, but consider the test story (use local
> provider, set all things up, test, push all to ec2, and juju just works
> - obviously not in the short term, but potentially something we might
> want to consider).
>  * The API seems quite nice and simple, and at the first look, seems
> like it wouldn't be too hard to use
>
> Not so good news, but not necessarily bad.
>  * Big warning on the docker.io website saying "docker is under active
> development - do not use for production"
>  * The default images that you get with docker are quantal not precise.
>  I don't see this as a huge issue as I'm sure there is a way to define
> an image repository
>  * The images for ubuntu are around 100 meg each (a bit of an overhead
> to download initially) - probably not a huge problem for real
> deployments if we manage the image repositories
>  * We would have to manage some other images, not just use ec2 or
> openstack.  I'm not entirely sure of the implications of this yet
>  * One api call I made broke my terminal and failed to return for
> something that should be simple - I intend to file a bug for it,
> shouldn't be too much or too hard - heck I might even fix it and send
> them a pull-request.
>  * Docker is not in the official ubuntu repository yet, only in a ppa
> with a precise build.  I downloaded the source and built it to test.  If
> we end up tweaking, we have the potential to ship it with the tools
> (although not necessarily desirable). On the plus side, they do want to
> get docker into ubuntu officially.
>  * Documentation is still very light, kind of expected at this stage.
>
> Other comments:
>  * Only real requirement (that I've found so far) is to have LXC available.
>  * Should, theoretically at least, work on ARM.  Although this isn't
> mentioned anywhere, and is not built for ARM in the PPA
>  * We would obviously be an early adopter of docker with juju, so we'd
> have to go through the pain of discovery and I'm sure we'd hit edge
> cases that the current users/writers of docker haven't it.  This makes
> timing harder to predict as we can't be sure that things will "just
> work".  We can hope, but that's about it.
>
>
> Conclusion:
>
> The promise of docker fits very well with Juju.  I think it is
> definitely worth spending more time investigating.  I think it is likely
> to be easier to use than raw LXC.
>
> Tim
>
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