High Availability command line interface - future plans.

[Tim Penhey]

On 07/11/13 15:00, Andrew Wilkins wrote:
> On Thu, Nov 7, 2013 at 9:23 AM, Ian Booth <ian.booth at canonical.com
> <mailto:ian.booth at canonical.com>> wrote:
> 
>     So, I haven't been involved directly in a lot of the discussion, but
>     my 2c is:
> 
>     +1 to juju ensure-ha
> 
>     Users don't give a f*ck about how Juju achieves HA, they just want
>     to know their
>     data will survive a node outage. What Juju does under the covers to
>     make that
>     happen, what jobs are run on what nodes etc - that's for Juju to
>     care about.
> 
>  
> I'm not so sure about that. I expect there'll be users who wants to know
> *exactly* how it works, because otherwise they won't feel they can trust
> it with their services. That's not to say that ensure-ha can't be
> trusted - just that some users will want to know what it's doing under
> the covers. Speculative, but based on past experience with banks,
> insurance companies, etc.

I think if we gave no feedback at all, then yes, this would feel like
magic.  However, I'd expect us to at least say what we are doing on the
command line :-)

I think ensure-ha is sufficient for a first cut, and a way to get ha on
a running system.

For the record, we discussed the default behaviour for ensure-ha was to
make three nodes of manager services.  The user could override this by
specifying "-n 5" or "-n 7", or some other odd number.

> Another thing to consider is that one person's HA is not the next
> person's. I may want to disperse my state servers across multiple
> regions (were that supported); you might find this costs too much in
> inter-region traffic. What happens if I have a temporary outage in one
> region - where does ensure-ha automatically spin up a new one? What
> happens when the original comes back? Each of these things are things
> people may want to do differently, because they each have different
> trade-offs.

I agree that support over regions is an important idea, but this is way
outside the scope of this HA discussion.

AFAIK, our cross-region story is still all about cross-environment
relations, not spanning regions with one environment.

Tim