A (Very) Minimal Charm

[Cory Johns]

Marco,

What is the issue you mentioned with using snaps where you mentioned
needing an "unconfined classic snap"?

On Thu, Dec 1, 2016 at 1:13 PM, Marco Ceppi <marco.ceppi at canonical.com>
wrote:

> On Thu, Dec 1, 2016 at 12:56 PM Casey Marshall <
> casey.marshall at canonical.com> wrote:
>
> 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?
>
>
> This comes up a bit, and I'm really eager to figure this out. Allow me to
> explain the catch-22. It's name is pyyaml.
>
> So the wheelhouse, by default, is 3.8M in size, this is the stock
> wheelhouse we vendor in:
>
> 312K charmhelpers-0.10.0.tar.gz
> 21K  charms.reactive-0.4.5.tar.gz
> 349K Jinja2-2.8.tar.gz
> 14K  MarkupSafe-0.23.tar.gz
> 1.7M netaddr-0.7.18.tar.gz
> 1.1M pip-8.1.2.tar.gz
> 19K  pyaml-16.11.4.tar.gz
> 248K PyYAML-3.12.tar.gz
> 29K  six-1.10.0.tar.gz
> 13K  Tempita-0.5.2.tar.gz
>
> The problem child is PyYAML, which is a compiled cpyhton module, which
> requires build-essential. The latest version is 3.12, trusty is 3.10,
> xenial 3.11, and zesty (finally) 3.12 http://packages.ubuntu.
> com/search?keywords=python-yaml, CentOS 6 & 7 are 3.10
>
> So, the easy path here is to just make sure charms.reactive works with
> PyYAML 3.10 and do a `--no-install-recommends` but that's half the problem.
> There will inevitably be python modules that require build-essential to
> compile on install.
>
> We can't cache the compiled wheelhouse because of architectures (same way
> resources complicate this) so we must compile at deploy time.
>
> One path forward, after dropping PyYAML 3.12 (if feasible), would be to
> see if we can detect when a python module needs to be compiled and setting
> a flag in the rendered charm to install the build-essentials, etc.
>
> I'll file issues and spend some time seeing if we can actually detect when
> you need to compile a wheelhouse vs a straight python module that and
> lowering the requirement for PyYAML (using packaged version instead) will
> probably remove a lot of the reactive bootstrap time.
>
> Marco
>
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