Open Stack

On Tue, 14 Oct 2014 07:51:54 AM Steven Dake wrote:
> Angus,
> 
> On 10/13/2014 08:51 PM, Angus Lees wrote:
> > I've been reading a bunch of the existing Dockerfiles, and I have two
> > humble requests:
> > 
> > 
> > 1. It would be good if the "interesting" code came from python
> > sdist/bdists
> > rather than rpms.
> > 
> > This will make it possible to rebuild the containers using code from a
> > private branch or even unsubmitted code, without having to go through a
> > redhat/rpm release process first.
> > 
> > I care much less about where the python dependencies come from. Pulling
> > them from rpms rather than pip/pypi seems like a very good idea, given
> > the relative difficulty of caching pypi content and we also pull in the
> > required C, etc libraries for free.
> > 
> > 
> > With this in place, I think I could drop my own containers and switch to
> > reusing kolla's for building virtual testing environments.  This would
> > make me happy.
> 
> I've captured this requirement here:
> https://blueprints.launchpad.net/kolla/+spec/run-from-master
> 
> I also believe it would be interesting to run from master or a stable
> branch for CD.  Unfortunately I'm still working on the nova-compute
> docker code, but if someone comes along and picks up that blueprint, i
> expect it will get implemented :)  Maybe that could be you.

Yeah I've already got a bunch of working containers that pull from master[1], 
but I've been thinking I should change that to use an externally supplied 
bdist.  The downside is you quickly end up wanting a docker container to build 
your deployment docker container.  I gather this is quite a common thing to 
do, but I haven't found the time to script it up yet.

[1] https://github.com/anguslees/kube-openstack/tree/master/docker

I could indeed work on this, and I guess I was gauging the level of enthusiasm 
within kolla for such a change.  I don't want to take time away from the 
alternative I have that already does what I need only to push uphill to get it 
integrated :/

> > 2. I think we should separate out "run the server" from "do once-off
> > setup".
> > 
> > Currently the containers run a start.sh that typically sets up the
> > database, runs the servers, creates keystone users and sets up the
> > keystone catalog.  In something like k8s, the container will almost
> > certainly be run multiple times in parallel and restarted numerous times,
> > so all those other steps go against the service-oriented k8s ideal and
> > are at-best wasted.
> > 
> > I suggest making the container contain the deployed code and offer a few
> > thin scripts/commands for entrypoints.  The main
> > replicationController/pod _just_ starts the server, and then we have
> > separate pods (or perhaps even non-k8s container invocations) that do
> > initial database setup/migrate, and post- install keystone setup.
> 
> The server may not start before the configuration of the server is
> complete.  I guess I don't quite understand what you indicate here when
> you say we have separate pods that do initial database setup/migrate.
> Do you mean have dependencies in some way, or for eg:
> 
> glance-registry-setup-pod.yaml - the glance registry pod descriptor
> which sets up the db and keystone
> glance-registry-pod.yaml - the glance registry pod descriptor which
> starts the application and waits for db/keystone setup
> 
> and start these two pods as part of the same selector (glance-registry)?
> 
> That idea sounds pretty appealing although probably won't be ready to go
> for milestone #1.

So the way I do it now, I have a replicationController that starts/manages 
(eg) nova-api pods[2].  I separately have a nova-db-sync pod[3] that basically 
just runs "nova-manage db sync".

I then have a simple shell script[4] that starts them all at the same time.  
The nova-api pods crash and get restarted a few times until the database has 
been appropriately configured by the nova-db-sync pod, and then they're fine and 
start serving.

When nova-db-sync exits successfully, the pod just sits in state terminated 
thanks to restartPolicy: onFailure.  Sometime later I can delete the 
terminated nova-db-sync pod, but it's also harmless if I just leave it or even 
if it gets occasionally re-run as part of some sort of update.


[2] https://github.com/anguslees/kube-openstack/blob/master/kubernetes-in/nova-api-repcon.yaml
[3] https://github.com/anguslees/kube-openstack/blob/master/kubernetes-in/nova-db-sync-pod.yaml
[4] https://github.com/anguslees/kube-openstack/blob/master/kubecfg-create.sh


> > I'm open to whether we want to make these as lightweight/independent as
> > possible (every daemon in an individual container), or limit it to one per
> > project (eg: run nova-api, nova-conductor, nova-scheduler, etc all in one
> > container).   I think the differences are run-time scalability and
> > resource- attribution vs upfront coding effort and are not hugely
> > significant either way.
> > 
> > Post-install catalog setup we can combine into one cross-service setup
> > like
> > tripleO does[1].  Although k8s doesn't have explicit support for batch
> > tasks currently, I'm doing the pre-install setup in restartPolicy:
> > onFailure pods currently and it seems to work quite well[2].
> > 
> > (I'm saying "post install catalog setup", but really keystone catalog can
> > happen at any point pre/post aiui.)
> > 
> > [1]
> > https://github.com/openstack/tripleo-incubator/blob/master/scripts/setup-> > endpoints [2]
> > https://github.com/anguslees/kube-openstack/blob/master/kubernetes-in/nov
> > a-db-sync-pod.yaml
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-- 
 - Gus