Re: It's time to build "guix deploy"

[Thompson, David]

Hi Chris,

Here we go again, eh? :)

On Mon, Feb 11, 2019 at 8:31 AM Christopher Lemmer Webber
<address@hidden> wrote:
>
> Hi,
>
> This has come up several times.  A lot of us want "guix deploy".
> Personally, I'm running a variety of Debian servers and one Guix server
> and I am terrible at maintaining all of them.

I have just a single Linode VPS that I can't be bothered to maintain
most of the time. I would like to switch to Guix, as well.

> It's time for Guix Deploy... or it's time for me to give up and use
> something like Ansible + Debian.  (Egads!  I don't want to do that.)
>
> David's thoughts on this are below, and here's the original thread:
>
> Original thread can be found at the links below:
>   https://lists.gnu.org/archive/html/guix-devel/2015-04/msg00525.html

Wow, 2015. I was so young and full of hope then. ;)

>   https://lists.gnu.org/archive/html/guix-devel/2015-05/msg00007.html
>   https://lists.gnu.org/archive/html/guix-devel/2015-06/msg00006.html
>
> There is a heavily, heavily bitrotted branch named "wip-deploy" where
> David originally started exploring these ideas.  Conveniently, it's all
> in one commit:
>
>   
> https://git.savannah.gnu.org/cgit/guix.git/commit/?h=wip-deploy&id=fcd6fc84e493d05be1f7590ee77509c81ac315c2

Useful for context, but the code can probably be tossed at this point.

> That seems like a good starting point.  But I know David feels that with
> real-world experience in devops type work that actually things would be
> a bit different than what's described in his original email.  I'm not
> sure myself what would be different.  It would be helpful to hear Dave
> weigh in on that point.

Sure, since 2015 I've become the lead devops person at my company, so
I like to think I'm a bit wiser now.

> Maybe Dave and I can meet up IRL now that we're close enough to each
> other to chat about it.  But I know it's less fun than it used to be for
> Dave to consider this because now that's Dave's actual job... but all
> the more reason we need Dave's wisdom! :)

We could meet up IRL about this and I can try to make an earnest
effort to deal with this. I think what has stopped me in the past is
the sheer size of this project, and maybe dramatically scaling down
the scope will allow us to get *something* out the door.  Here are
some general use-cases I know about for deployments, roughly ordered
from small scale to large scale, and least complex to most complex:

* Managing a physical machine or two that have been given memorable
names that you update in-place (home scale)
* Managing a virtual machine or two that have been given memorable
names that you update in-place (blog scale)
* Managing a large number of virtual machines whose names don't matter
that you update in-place (proto-cloud scale)
* Managing a large number of virtual machines whose names don't matter
that are replaced when there is an update (cloud scale)
* Managing 1 or more clusters of physical machines (datacenter scale)
* Managing 1 or more clusters of physical machines and virtual
machines ("corporation with a datacenter that is moving some stuff to
the cloud" scale)

There are, of course, more scenarios to consider (haven't even touched
upon things like a Kubernetes cluster), but this is enough to
illustrate the point that is a great diversity in setups.  How many
machines are there? Are the bare metal, virtual machines, or a mix of
both? In the case of virtual machines, are updates applied in an
immutable fashion or not?  If immutable, which technique (blue-green,
rolling release, etc.)?  It makes my head spin to think about all the
use-cases.

So... let's start small. Can we write a tool that handles in-place
updates to machines (physical or virtual) whose name and IP address we
know well (our special pet servers) without precluding the possibility
of scaling up to more sophisticated architectures?  This would address
the "home" and "blog" scale items above, which is probably what most
of the people actually using Guix today would want.  I got stuck
trying to do in-place updates to remote machines years ago, but that
was before Ludo made it easy to connect to remote systems.

Other thoughts?

Yours in vaporware,

- Dave