[openstack-dev] Scheduler proposal

Ed Leafe ed at leafe.com
Thu Oct 8 16:21:14 UTC 2015


On Oct 8, 2015, at 8:01 AM, Thierry Carrez <thierry at openstack.org> wrote:

>> Operational overhead has a cost - maintaining 3 different database
>> tools, backing them up, providing HA, etc. has operational cost.
>> 
>> This is not to say that this cannot be overseen, but it should be taken
>> into consideration.
>> 
>> And *if* they can be consolidated into an agreed solution across the
>> whole of OpenStack - that would be highly beneficial (IMHO).
> 
> Agreed, and that ties into the similar discussion we recently had about
> picking a common DLM. Ideally we'd only add *one* general dependency and
> use it for locks / leader election / syncing status around.

Oh, yes, sorry, I left that out of this particular post, as it had been discussed at length back in July. But yes, introducing a new dependency has a high cost, and needs to be justified before anyone would ever consider taking on that added cost. That was in my original email [0] back in July:

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At this point I'm sure that most of you are filled with thoughts on
how this won't work, or how much trouble it will be to switch, or how
much more of a pain it will be, or how you hate non-relational DBs, or
any of a zillion other negative thoughts. FWIW, I have them too. But
instead of ranting, I would ask that we acknowledge for now that:

a) it will be disruptive and painful to switch something like this at
this point in Nova's development
b) it would have to provide *significant* improvement to make such a
change worthwhile

So what I'm asking from all of you is to help define the second part:
what we would want improved, and how to measure those benefits. In
other words, what results would you have to see in order to make you
reconsider your initial "nah, this'll never work" reaction, and start
to think that this is will be a worthwhile change to make to Nova.
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Whether we make this type of change, or some other type of change, or keep things the way they are, having the data to justify that decision is always important.

-- Ed Leafe

[0] http://lists.openstack.org/pipermail/openstack-dev/2015-July/069593.html

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