A (Very) Minimal Charm

[Casey Marshall]

On Thu, Dec 1, 2016 at 6:53 AM, Marco Ceppi <marco.ceppi at canonical.com>
wrote:

> On Thu, Dec 1, 2016 at 5:00 AM Adam Collard <adam.collard at canonical.com>
> wrote:
>
>> On Thu, 1 Dec 2016 at 04:02 Nate Finch <nate.finch at canonical.com> wrote:
>>
>> On IRC, someone was lamenting the fact that the Ubuntu charm takes longer
>> to deploy now, because it has been updated to exercise more of Juju's
>> features.  My response was - just make a minimal charm, it's easy.  And
>> then of course, I had to figure out how minimal you can get.  Here it is:
>>
>> It's just a directory with a metadata.yaml in it with these contents:
>>
>> name: min
>> summary: nope
>> description: nope
>> series:
>>   - xenial
>>
>> (obviously you can set the series to whatever you want)
>> No other files or directories are needed.
>>
>>
>> This is neat, but doesn't detract from the bloat in the ubuntu charm.
>>
>
> I'm happy to work though changes to the Ubuntu charm to decrease "bloat".
>
>
>> IMHO the bloat in the ubuntu charm isn't from support for Juju features,
>> but the switch to reactive plus conflicts in layer-base wanting to a)
>> support lots of toolchains to allow layers above it to be slimmer and b) be
>> a suitable base for "just deploy me" ubuntu.
>>
>
> But it is to support the reactive framework, where we utilize newer Juju
> features, like status and application-version to make the charm rich
> despite it's minimal goal set. Honestly, a handful of cached wheelhouses
> and some apt packages don't strike me as bloat, but I do want to make sure
> the Ubuntu charm works for those using it. So,
>

I think a minimal wheelhouse to provide a consistent charm hook runtime is
very reasonable and definitely not the problem here.

There are too many packages that get installed by default with the reactive
framework that most charms don't need. When I deploy the ubuntu charm (but
this applies to any charm built with reactive and layer:basic), I also get:

2016-12-01 17:45:47 INFO install The following NEW packages will be
installed:
2016-12-01 17:45:47 INFO install   binutils build-essential cpp cpp-5
dpkg-dev fakeroot g++ g++-5 gc
c gcc-5
2016-12-01 17:45:47 INFO install   libalgorithm-diff-perl
libalgorithm-diff-xs-perl libalgorithm-mer
ge-perl
2016-12-01 17:45:47 INFO install   libasan2 libatomic1 libc-dev-bin
libc6-dev libcc1-0 libcilkrts5 l
ibdpkg-perl
2016-12-01 17:45:47 INFO install   libexpat1-dev libfakeroot
libfile-fcntllock-perl libgcc-5-dev libgomp1
2016-12-01 17:45:47 INFO install   libisl15 libitm1 liblsan0 libmpc3
libmpx0 libpython3-dev libpython3.5-dev
2016-12-01 17:45:47 INFO install   libquadmath0 libstdc++-5-dev libtsan0
libubsan0 linux-libc-dev make
2016-12-01 17:45:47 INFO install   manpages-dev python-pip-whl python3-dev
python3-pip python3-setuptools
2016-12-01 17:45:47 INFO install   python3-wheel python3.5-dev

None of my charms need build-essential or a g++ compiler, that's a lot of
unnecessary dependencies! Can we get rid of most of these? Would installing
the bare minimum with --no-install-recommends help?


> What's the real problem with the Ubuntu charm today?
> How does it not achieve it's goal of providing a relatively blank Ubuntu
> machine? What are people using the Ubuntu charm for?
>
> Other than demos, hacks/workarounds, and testing I'm not clear on the
> purpose of an Ubuntu charm in a model serves.
>
> Marco
>
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