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Re: Ubuntu Xenial stemcell and rootfs plans

Mike Dalessio
 

Hi Mike,

I totally agree with you on all points, but there are second-order effects
that are worth discussing and understanding, as they've influenced my own
thinking around the timing of this work.

Given the current state of automation in the Buildpacks Team's CI
pipelines, we could add a Xenial-based rootfs ("cflinuxfs3"?) to CF pretty
quickly (and in fact have considered doing exactly this), and could build
precompiled Xenial binaries to add to each buildpack pretty easily.

Unfortunately, this would result in doubling (or nearly so) the size of
almost all of the buildpacks, since the majority of a buildpack's payload
are the precompiled binaries for the rootfs. For example, we'd need to
compile several Ruby binaries for Xenial and vendor them in the buildpack
alongside the existing Trusty-based binaries.

Larger buildpacks result in longer staging times, longer deploy times for
CF, and are just generally a burden to ship around, particularly for
operators and users that don't actually want or need two stacks.

A second solution is to ship a separate buildpack for each stack (so,
ruby_buildpack_cflinuxfs2 versus ruby_buildpack_cflinuxfs3), and have
`bin/detect` only select itself if it's running on the appropriate stack.

But this would simply be forcing all buildpacks to plug a leaky
abstraction, and so I'd like to endeavor to make buildpacks simpler to
maintain.

A third solution, and the one which I think we should pursue, is to ship
separate buildpacks for each stack, but make Cloud Controller aware of the
buildpack's "stackiness", and only invoke buildpacks that are appropriate
for that stack.

So, for example, the CC would know that the go_buildpack works on both
Trusty- and Xenial-based rootfses (as those binaries are statically
linked), and would also know that ruby_buildpack_cflinuxfs2 isn't valid for
applications running on cflinuxfs3.

This work, however, will require some changes to CC's behavior, and that's
the critical path work that hasn't been scoped or prioritized yet.

Hope this helps everyone understand some of the concerns, and hopefully
explains why we haven't just shipped a Xenial-based stack.

-m

On Tue, May 10, 2016 at 1:34 PM, Mike Youngstrom <youngm(a)gmail.com> wrote:

I may not have anything that qualifies as compelling. But, here are some
of the reasons I've got:

* If skipping Xenial that give at the most 1 year to transition from
trusty to a 2018.04 based rootfs. Lets say it takes 6 months to get the
new rootFS into our customers hands and for everyone to be comfortable
enough with it to make it the default. I don't think 6 months is enough
time for my users to naturally transition all of their applications via
pushes and restages to the new rootfs. The more time we have with the new
rootfs as the default the less I will need to bother my customers to test
before I force them to change.

* Xenial uses OpenSSL 1.0.2. Improving security by not statically
compiling OpenSSL into Node would be nice.

* With the lucid rootfs after a while it became difficult to find
pre-built libraries for Lucid. This put increased burden on me to identify
and provide lucid compatible builds for some common tools. One example of
this is wkhtmltopdf a commonly used tool in my organization.

I think the biggest thing for me is that the move from Lucid to Trusty was
a nightmare for me and my customers. Though better planning and adding a
couple of more months to the process would help, giving my users a couple
of years to migrate would be better. :)

Mike

On Mon, May 9, 2016 at 2:05 PM, Danny Rosen <drosen(a)pivotal.io> wrote:

Hey Mike,

Thanks for reaching out. We've discussed supporting Xenial recently but
have had trouble identifying compelling reasons to do so. Our current
version of the rootfs is supported until April 2019 [1] and while we do not
plan on waiting until March 2019 :) we want to understand compelling
reasons to go forward with the work sooner than later.


On Mon, May 9, 2016 at 12:47 PM, Mike Youngstrom <youngm(a)gmail.com>
wrote:

Ubuntu Xenial Xerus was released a few weeks ago. Any plans to
incorporate Xenial into the platform? Stemcells and/or new root fs?

The recent lucid to trusty rootfs fire drill was frustrating to my
customers. I'm hoping that this year we can get a Xenial rootfs out
loooong before trusty support ends so I don't have to put another tight
deadline on my customers to test and move.

Thoughts?

Thanks,
Mike

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