Open Stack

On Mon, 24 Aug 2020 at 17:53, Tony Liu <tonyliu0592 at hotmail.com> wrote:
>
> > -----Original Message-----
> > From: Mark Goddard <mark at stackhpc.com>
> > Sent: Monday, August 24, 2020 12:46 AM
> > To: Eric K. Miller <emiller at genesishosting.com>
> > Cc: openstack-discuss <openstack-discuss at lists.openstack.org>
> > Subject: Re: [Kolla Ansible] host maintenance
> >
> > On Sat, 22 Aug 2020 at 01:10, Eric K. Miller <emiller at genesishosting.com>
> > wrote:
> > >
> > > > Actually, in my case, the setup is originally deploy by Kolla
> > > > Ansible. Other than the initial deployment, I am looking for using
> > > > Kolla Ansible for maintenance operations.
> > > > What I am looking for, eg. replace a host, can surely be done by
> > > > manual steps or customized script. I'd like to know if they are
> > > > automated by Kolla Ansible.
> > >
> > > We do this often by simply using the "limit" flag in Kolla Ansible to
> > only include the controllers and new compute node (after adding the
> > compute node to the multinode.ini file).  Specify "reconfigure" for the
> > action, and not "install".
> >
> > We need some better docs around this, and I think they will be added
> > soon. Some things to watch out for:
> >
> > * if adding a new controller, ensure that if using --limit, all
> > controllers are included and do not use serial mode
>
> What I tried was to replace a controller, where I don't need to
> update other controllers, because there is no address update.
>
> If there is address update caused by controller change, then all
> controllers have to be included to get update.

While this may work at the moment, we have just merged a change that
prevents this. For keystone, we need access to all controllers, to
determine whether it is a new cluster or a new node in an existing
cluster.

>
> What's "serial mode"?

Ansible has a feature to run plays in batches of some % of the hosts.
In Kolla Ansible you can e.g. export ANSIBLE_SERIAL=0.1. It's an
advanced use case and needs some care.

>
> > * if removing a controller, reconfigure other controllers to update the
> > RabbitMQ & Galera cluster nodes etc.
>
> In this case, are those services who don't need any updates going
> to be restarted or untouched?
>
> Thanks!
> Tony
>