Indeed it is a considered a base service, but I'm unaware of why it was decided to not have any abstraction layer on top. That sort of defeats the adoption of tooz as a standard in the community. Plus with the rest of our code bases, we have a number of similar or identical patterns and it would be ideal to have a single library providing the overall interface for the purposes of consistency. Could you provide some more background on that decision?

I guess what I'd really like to see is an oslo.db interface into etcd3.

-Julia

On Mon, Dec 3, 2018 at 4:55 PM Fox, Kevin M <Kevin.Fox@pnnl.gov> wrote:
It is a full base service already:
https://governance.openstack.org/tc/reference/base-services.html

Projects have been free to use it for quite some time. I'm not sure if any actually are yet though.

It was decided not to put an abstraction layer on top as its pretty simple and commonly deployed.

Thanks,
Kevin
From: Julia Kreger [juliaashleykreger@gmail.com]
Sent: Monday, December 03, 2018 3:53 PM
To: Ben Nemec
Cc: Davanum Srinivas; geguileo@redhat.com; openstack-discuss@lists.openstack.org
Subject: Re: [all] Etcd as DLM

I would like to slightly interrupt this train of thought for an unscheduled vision of the future!

What if we could allow a component to store data in etcd3's key value store like how we presently use oslo_db/sqlalchemy?

While I personally hope to have etcd3 as a DLM for ironic one day, review bandwidth permitting, it occurs to me that etcd3 could be leveraged for more than just DLM. If we have a common vision to enable data storage, I suspect it might help provide overall guidance as to how we want to interact with the service moving forward.

-Julia

On Mon, Dec 3, 2018 at 2:52 PM Ben Nemec <openstack@nemebean.com> wrote:
Hi,

I wanted to revisit this topic because it has come up in some downstream
discussions around Cinder A/A HA and the last time we talked about it
upstream was a year and a half ago[1]. There have certainly been changes
since then so I think it's worth another look. For context, the
conclusion of that session was:

"Let's use etcd 3.x in the devstack CI, projects that are eventlet based
an use the etcd v3 http experimental API and those that don't can use
the etcd v3 gRPC API. Dims will submit a patch to tooz for the new
driver with v3 http experimental API. Projects should feel free to use
the DLM based on tooz+etcd3 from now on. Others projects can figure out
other use cases for etcd3."

The main question that has come up is whether this is still the best
practice or if we should revisit the preferred drivers for etcd. Gorka
has gotten the grpc-based driver working in a Cinder driver that needs
etcd[2], so there's a question as to whether we still need the HTTP
etcd-gateway or if everything should use grpc. I will admit I'm nervous
about trying to juggle eventlet and grpc, but if it works then my only
argument is general misgivings about doing anything clever that involves
eventlet. :-)

It looks like the HTTP API for etcd has moved out of experimental
status[3] at this point, so that's no longer an issue. There was some
vague concern from a downstream packaging perspective that the grpc
library might use a funky build system, whereas the etcd3-gateway
library only depends on existing OpenStack requirements.

On the other hand, I don't know how much of a hassle it is to deploy and
manage a grpc-gateway. I'm kind of hoping someone has already been down
this road and can advise about what they found.

Thanks.

-Ben

1: https://etherpad.openstack.org/p/BOS-etcd-base-service
2:
https://github.com/embercsi/ember-csi/blob/5bd4dffe9107bc906d14a45cd819d9a659c19047/ember_csi/ember_csi.py#L1106-L1111
3: https://github.com/grpc-ecosystem/grpc-gateway