[openstack-dev] [all] etcd3 as base service - update

Mike Bayer mbayer at redhat.com
Thu Jun 8 16:37:20 UTC 2017

On 06/08/2017 12:47 AM, Joshua Harlow wrote:
> So just out of curiosity, but do people really even know what etcd is 
> good for? I am thinking that there should be some guidance from folks in 
> the community as to where etcd should be used and where it shouldn't 
> (otherwise we just all end up in a mess).

So far I've seen a proposal of etcd3 as a replacement for memcached in 
keystone, and a new dogpile connector was added to oslo.cache to handle 
referring to etcd3 as a cache backend.  This is a really simplistic / 
minimal kind of use case for a key-store.

But, keeping in mind I don't know anything about etcd3 other than "it's 
another key-store", it's the only database used by Kubernetes as a 
whole, which suggests it's doing a better job than Redis in terms of 
"durable".   So I wouldn't be surprised if new / existing openstack 
applications express some gravitational pull towards using it as their 
own datastore as well.    I'll be trying to hang onto the etcd3 track as 
much as possible so that if/when that happens I still have a job :).

> Perhaps a good idea to actually give examples of how it should be used, 
> how it shouldn't be used, what it offers, what it doesn't... Or at least 
> provide links for people to read up on this.
> Thoughts?
> Davanum Srinivas wrote:
>> One clarification: Since https://pypi.python.org/pypi/etcd3gw just
>> uses the HTTP API (/v3alpha) it will work under both eventlet and
>> non-eventlet environments.
>> Thanks,
>> Dims
>> On Wed, Jun 7, 2017 at 6:47 AM, Davanum Srinivas<davanum at gmail.com>  
>> wrote:
>>> Team,
>>> Here's the update to the base services resolution from the TC:
>>> https://governance.openstack.org/tc/reference/base-services.html
>>> First request is to Distros, Packagers, Deployers, anyone who
>>> installs/configures OpenStack:
>>> Please make sure you have latest etcd 3.x available in your
>>> environment for Services to use, Fedora already does, we need help in
>>> making sure all distros and architectures are covered.
>>> Any project who want to use etcd v3 API via grpc, please use:
>>> https://pypi.python.org/pypi/etcd3 (works only for non-eventlet 
>>> services)
>>> Those that depend on eventlet, please use the etcd3 v3alpha HTTP API 
>>> using:
>>> https://pypi.python.org/pypi/etcd3gw
>>> If you use tooz, there are 2 driver choices for you:
>>> https://github.com/openstack/tooz/blob/master/setup.cfg#L29
>>> https://github.com/openstack/tooz/blob/master/setup.cfg#L30
>>> If you use oslo.cache, there is a driver for you:
>>> https://github.com/openstack/oslo.cache/blob/master/setup.cfg#L33
>>> Devstack installs etcd3 by default and points cinder to it:
>>> http://git.openstack.org/cgit/openstack-dev/devstack/tree/lib/etcd3
>>> http://git.openstack.org/cgit/openstack-dev/devstack/tree/lib/cinder#n356 
>>> Review in progress for keystone to use etcd3 for caching:
>>> https://review.openstack.org/#/c/469621/
>>> Doug is working on proposal(s) for oslo.config to store some
>>> configuration in etcd3:
>>> https://review.openstack.org/#/c/454897/
>>> So, feel free to turn on / test with etcd3 and report issues.
>>> Thanks,
>>> Dims
>>> -- 
>>> Davanum Srinivas :: https://twitter.com/dims
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