On 15/10/14 10:38, Clint Byrum wrote:
Excerpts from Thomas Spatzier's message of 2014-10-14 10:13:27 -0700:
Hi all,
I have been experimenting a lot with Heat software config to check out
what works today, and to think about potential next steps.
I've also worked on an internal project where we are leveraging software
config as of the Icehouse release.
I think what we can do now from a user's perspective in a HOT template is
really nice and resonates well also with customers I've talked to.
One of the points where we are constantly having issues, and also got some
push back from customers, are the requirements on the in-instance tools and
the process of building base images.
One observation is that building a base image with all the right stuff
inside sometimes is a brittle process; the other point is that a lot of
customers do not like a lot of requirements on their base images. They want
to maintain one set of corporate base images, with as little modification
on top as possible.
Regarding the process of building base images, the currently documented way
[1] of using diskimage-builder turns out to be a bit unstable sometimes.
Not because diskimage-builder is unstable, but probably because it pulls in
components from a couple of sources:
#1 we have a dependency on implementation of the Heat engine of course (So
this is not pulled in to the image building process, but the dependency is
there)
#2 we depend on features in python-heatclient (and other python-* clients)
#3 we pull in implementation from the heat-templates repo
#4 we depend on tripleo-image-elements
#5 we depend on os-collect-config, os-refresh-config and os-apply-config
#6 we depend on diskimage-builder itself
Heat itself and python-heatclient are reasonably well in synch because
there is a release process for both, so we can tell users with some
certainty that a feature will work with release X of OpenStack and Heat and
version x.z.y of python-heatclient. For the other 4 sources, success
sometimes depends on the time of day when you try to build an image
(depending on what changes are currently included in each repo). So
basically there does not seem to be a consolidated release process across
all that is currently needed for software config.
I don't really understand why a "consolidated release process across
all" would be desired or needed.
#3 is pretty odd. You're pulling in templates from the examples repo?
heat-templates is where our hook elements live:
[1]
https://github.com/openstack/heat-templates/blob/master/hot/software-config/elements/README.rst
For #4-#6, those are all on pypi and released on a regular basis. Build
yourself a bandersnatch mirror and you'll have locally controlled access
to them which should eliminate any reliability issues.
The ideal solution would be to have one self-contained package that is easy
to install on various distributions (an rpm, deb, MSI ...).
Secondly, it would be ideal to not have to bake additional things into the
image but doing bootstrapping during instance creation based on an existing
cloud-init enabled image. For that we would have to strip requirements down
to a bare minimum required for software config. One thing that comes to my
mind is the cirros software config example [2] that Steven Hardy created.
It is admittedly no up to what one could do with an image built according
to [1] but on the other hand is really slick, whereas [1] installs a whole
set of things into the image (some of which do not really seem to be needed
for software config).
The agent problem is one reason I've been drifting away from Heat
for software configuration, and toward Ansible. Mind you, I wrote
os-collect-config to have as few dependencies as possible as one attempt
around this problem. Still it isn't capable enough to do the job on its
own, so you end up needing os-apply-config and then os-refresh-config
to tie the two together.
For heat's requirements, os-refresh-config or os-apply-config is
overkill to go from occ to the config hooks, but they're tiny and useful
in their own right so I'm OK with requiring them.
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