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We'll have a chance to discuss DB mutual exclusion at the API nodes at the Cider mid-cyle, which starts tomorrow.
The details, issues, and realistic schedule for that will be a key piece to this whole puzzle, since anything else is seen as a temporary solution.

-----Original Message-----
From: Gorka Eguileor [mailto:geguileo at redhat.com] 
Sent: Monday, August 03, 2015 11:38 AM
To: OpenStack Development Mailing List (not for usage questions)
Subject: Re: [openstack-dev] [Cinder] A possible solution for HA Active-Active

On Mon, Aug 03, 2015 at 07:01:45PM +1000, Morgan Fainberg wrote:
> Lets step back away from tooz. Tooz for the sake of this conversation is as much the same as saying zookeeper or consul or etcd, etc. We should be focused (as both Flavio and Thierry said) on if we need DLM and what it will solve.

What do you mean we should be focused on if we need a DLM and what it will solve?

I don't know what you mean, as those answers are quite clear:

- The DLM replaces our current local file locks and extends them among
  nodes, it does not provide any additional functionality.

- Do we need a DLM?  Need is a strong word, if you are asking if we can
  do it without a DLM, then the answer is yes, we can do it without it.
  And if you ask if it will take more time than using a DLM and has the
  potential to introduce more bugs, then the answer is yes as well.

- Will we keep using a DLM forever?  No, we will change the DLM locks
  with DB mutual exclusion at the API nodes later.

Gorka.

> 
> Once we have all of that defined, the use of an abstraction such as tooz (or just the direct bindings for some specific choice) can be made. 
> 
> I want to voice that we should be very picky about the solution (if we decide on a DLM) so that we are implementing to the strengths of the solution rather than try and make everything work seamlessly.  
> 
> --Morgan
> 
> Sent via mobile
> 
> >> On Aug 3, 2015, at 18:49, Julien Danjou <julien at danjou.info> wrote:
> >> 
> >> On Mon, Aug 03 2015, Thierry Carrez wrote:
> >> 
> >> The last thing we want is to rush a solution that would only solve 
> >> a particular project use case. Personally I'd like us to pick the 
> >> simplest solution that can solve most of the use cases. Each of the 
> >> solutions bring something to the table -- Zookeeper is mature, 
> >> Consul is featureful, etcd is lean and simple... Let's not dive 
> >> into the best solution but clearly define the problem space first.
> > 
> > Or just start using Tooz – like some of OpenStack are already doing 
> > for months – and let the operators pick the backend that they are 
> > the most comfortable with? :)
> > 
> > --
> > Julien Danjou
> > -- Free Software hacker
> > -- http://julien.danjou.info
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