Open Stack

> -----Original Message-----
> From: Mark Goddard <mark at stackhpc.com>
> Sent: Monday, August 24, 2020 11:21 AM
> To: Tony Liu <tonyliu0592 at hotmail.com>
> Cc: Eric K. Miller <emiller at genesishosting.com>; openstack-discuss
> <openstack-discuss at lists.openstack.org>
> Subject: Re: [Kolla Ansible] host maintenance
> 
> 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?

Could you comment on this? This is my biggest concern. I'd like
to ensure services who don't need update remain untouched.

Thanks!
Tony