Open Stack

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Hi all,

I'm currently pushing Neutron to oslo.messaging, and while at it, a
question popped up.

So in oslo-rpc, we have the following notification drivers available:
neutron.openstack.common.notifier.log_notifier
neutron.openstack.common.notifier.no_op_notifier
neutron.openstack.common.notifier.rpc_notifier2
neutron.openstack.common.notifier.rpc_notifier
neutron.openstack.common.notifier.test_notifier

And in oslo.messaging, we have:
oslo.messaging.notify._impl_log:LogDriver
oslo.messaging.notify._impl_noop:NoOpDriver
oslo.messaging.notify._impl_messaging:MessagingV2Driver
oslo.messaging.notify._impl_messaging:MessagingDriver
oslo.messaging.notify._impl_test:TestDriver

My understanding is that they map to each other as in [1].

So atm Neutron uses rpc_notifier from oslo-rpc, so I'm going to
replace it with MessagingDriver. So far so good.

But then I've checked docstrings for MessagingDriver and
MessagingV2Driver [2], and the following looks suspicious to me. For
MessagingDriver, it's said:

"This driver should only be used in cases where there are existing
consumers deployed which do not support the 2.0 message format."

This sounds like MessagingDriver is somehow obsolete, and we want to
use MessagingV2Driver unless forced to. But I don't get what those
consumers are. Are these other projects that interact with us via
messaging bus?

Another weird thing is that it seems that no other project is actually
using MessagingV2Driver (at least those that I've checked). Is it even
running in wild?

Can oslo devs elaborate on that topic?

Thanks,
/Ihar

[1]: https://review.openstack.org/#/c/100013/3/setup.cfg
[2]:
https://github.com/openstack/oslo.messaging/blob/master/oslo/messaging/notify/_impl_messaging.py
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