[openstack-dev] [oslo][devstack][all] ZooKeeper vs etcd for Tooz/DLM

Davanum Srinivas davanum at gmail.com
Wed Mar 15 11:48:48 UTC 2017

+1000 Sean.


On Wed, Mar 15, 2017 at 7:44 AM, Sean Dague <sean at dague.net> wrote:
> On 03/14/2017 11:00 PM, Monty Taylor wrote:
> <snip>
>> a) awesome. when the rest of this dips momentarily into words that might
>> sound negative, please hear it all wrapped in an "awesome" and know that
>> my personal desire is to see the thing you're working on be successful
>> without undue burden...
>> b) In Tokyo, we had the big discussion about DLMs (where at least my
>> intent going in to the room was to get us to pick one and only one).
>> There were three camps in the room who were all vocal:
>> 1) YES! Let's just pick one, I don't care which one
>> 2) I hate Java I don't want to run Zookeeper, so we can't pick that
>> 3) I hate go/don't trust coreos I don't want to run etcd so we can't
>> pick that
>> Because of 2 and 3 the group represented by 1 lost and we ended up with:
>> "crap, we have to use an abstraction library"
>> I'd argue that unless something has changed significantly, having Nova
>> grow a direct depend on etcd when the DLM discussion brought us to "the
>> operators in the room have expressed a need for a pluggable choice
>> between at least zk and etcd" should be pretty much a non-starter.
>> Now, being that I was personally in group 1, I'd be THRILLED if we
>> could, as a community, decide to pick one and skip having an abstraction
>> library. I still don't care which one - and you know I love gRPC/protobuf.
>> But I do think that given the anti-etcd sentiment that was expressed was
>> equally as vehement as the anti-zk sentiment, that we need to circle
>> back and make a legit call on this topic.
>> If we can pick one, I think having special-purpose libraries like
>> os-lively for specific purposes would be neat.
>> If we still can't pick one, then I think adding the liveness check you
>> implemented for os-lively as a new feature in tooz and also implementing
>> the same thing in the zk driver would be necessary. (of course, that'll
>> probably depend on getting etcd3 support added to tooz and making sure
>> there is a good functional test for etcd3.
> We should also make it clear that:
> 1) Tokyo was nearly 1.5 years ago.
> 2) Many stake holders in openstack with people in that room may no
> longer be part of our community
> 3) Alignment with Kubernetes has become something important at many
> levels inside of OpenStack (which puts some real weight on the etcd front)
> 4) The containers ecosystem, which etcd came out of, has matured
> dramatically
> I do think this is enough change to when that decision was made to
> revisit. As was said elsewhere in this thread, you have to run etcd for
> kubernetes, so picking that (in an opinionated way) for OpenStack seems
> like a good both technical and social call.
>         -Sean
> --
> Sean Dague
> http://dague.net
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Davanum Srinivas :: https://twitter.com/dims

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