Open Stack

On Thu, 2014-07-17 at 15:54 +0100, Michael Kerrin wrote:
> On Thursday 26 June 2014 12:20:30 Clint Byrum wrote:
> 
> > Excerpts from Macdonald-Wallace, Matthew's message of 2014-06-26
> 04:13:31 -0700:
> 
> > > Hi all,
> 
> > > 
> 
> > > I've been working more and more with TripleO recently and whilst
> it does
> 
> > > seem to solve a number of problems well, I have found a couple of
> 
> > > idiosyncrasies that I feel would be easy to address.
> 
> > > 
> 
> > > My primary concern lies in the fact that os-refresh-config does
> not run on
> 
> > > every boot/reboot of a system. Surely a reboot *is* a
> configuration
> 
> > > change and therefore we should ensure that the box has come up in
> the
> 
> > > expected state with the correct config?
> 
> > > 
> 
> > > This is easily fixed through the addition of an "@reboot" entry in
> 
> > > /etc/crontab to run o-r-c or (less easily) by re-designing o-r-c
> to run
> 
> > > as a service.
> 
> > > 
> 
> > > My secondary concern is that through not running os-refresh-config
> on a
> 
> > > regular basis by default (i.e. every 15 minutes or something in
> the same
> 
> > > style as chef/cfengine/puppet), we leave ourselves exposed to
> someone
> 
> > > trying to make a "quick fix" to a production node and taking that
> node
> 
> > > offline the next time it reboots because the config was still left
> as
> 
> > > broken owing to a lack of updates to HEAT (I'm thinking a "quick
> change"
> 
> > > to allow root access via SSH during a major incident that is then
> left
> 
> > > unchanged for months because no-one updated HEAT).
> 
> > > 
> 
> > > There are a number of options to fix this including Modifying
> 
> > > os-collect-config to auto-run os-refresh-config on a regular basis
> or
> 
> > > setting os-refresh-config to be its own service running via
> upstart or
> 
> > > similar that triggers every 15 minutes
> 
> > > 
> 
> > > I'm sure there are other solutions to these problems, however I
> know from
> 
> > > experience that claiming this is solved through "education of
> users" or
> 
> > > (more severely!) via HR is not a sensible approach to take as by
> the time
> 
> > > you realise that your configuration has been changed for the last
> 24
> 
> > > hours it's often too late!
> 
> > So I see two problems highlighted above.
> 
> > 
> 
> > 1) We don't re-assert ephemeral state set by o-r-c scripts. You're
> right,
> 
> > and we've been talking about it for a while. The right thing to do
> is
> 
> > have os-collect-config re-run its command on boot. I don't think a
> cron
> 
> > job is the right way to go, we should just have a file in /var/run
> that
> 
> > is placed there only on a successful run of the command. If that
> file
> 
> > does not exist, then we run the command.
> 
> > 
> 
> > I've just opened this bug in response:
> 
> > 
> 
> > https://bugs.launchpad.net/os-collect-config/+bug/1334804
> 
> > 
> 
>  
> 
> I have been looking into bug #1334804 and I have a review up to
> resolve it. I want to highlight something.
> 
>  
> 
> Currently on a reboot we start all services via upstart (on debian
> anyways) and there have been quite a lot of issues around this -
> missing upstart scripts and timing issues. I don't know the issues on
> fedora.
> 
>  
> 
> So with a fix to #1334804, on a reboot upstart will start all the
> services first (with potentially out-of-date configuration), then
> o-c-c will start o-r-c and will now configure all services and restart
> them or start them if upstart isn't configured properly.
> 
>  
> 
> I would like to turn off all boot scripts for services we configure
> and leave all this to o-r-c. I think this will simplify things and put
> us in control of starting services. I believe that it will also narrow
> the gap between fedora and debian or debian and debian so what works
> on one should work on the other and make it easier for developers.

I'm not sold on this approach. At the very least I think we want to make
this optional because not all deployments may want to have o-r-c be the
central service starting agent. So I'm opposed to this being our (only!)
default...

The job of o-r-c in this regard is to assert state... which to me means
making sure that a service is configured correctly (config files, set to
start on boot, and initially started). Requiring o-r-c to be the service
starting agent (always) is beyond the scope of the o-r-c tool.

If people want to use it in that mode I think having an *option* to do
this is fine. I don't think it should be required though. Furthermore I
don't think we should get into the habit of writing our elements in such
a matter that things no longer start on boot without o-r-c in the mix.

I do think we can solve these problems. But taking a hardwired
prescriptive approach is not good here...

> 
>  
> 
> Having the ability to service nova-api stop|start|restart is very
> handy but this will be a manually thing and I intend to leave that
> there.
> 
>  
> 
> What do people think and how best do I push this forward. I feel that
> this leads into the the re-assert-system-state spec but mainly I think
> this is a bug and doesn't require a spec.
> 
>  
> 
> I will be at the tripleo mid-cycle meetup next and willing to discuss
> this with anyone interested in this and put together the necessary
> bits to make this happen.
> 
>  
> 
> Michael
> 
>  
> 
>  
> 
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