Support ZeroMQ messaging driver in cinder

[OpenStack Infra]

https://review.openstack.org/271848
Dear bug triager. This bug was created since a commit was marked with DOCIMPACT.
Your project "openstack/cinder" is set up so that we directly report the documentation bugs against it. If this needs changing, the docimpact-group option needs to be added for the project. You can ask the OpenStack infra team (#openstack-infra on freenode) for help if you need to.

commit 3320a8943827e82a1576d212b1ea076a9381ef63
Author: Vivek Dhayaal <email address hidden>
Date: Sun Jan 24 11:17:37 2016 +0530

    Support ZeroMQ messaging driver in cinder

    NOTE:This patch introduces support for ZeroMQ driver for cinder single
    backend case.
    Multi-backend will be addressed in the next patch as part of the
    blueprint.

    CHANGES:ZeroMQ driver requires hostname for message delivery as there is no
    broker inbetween.
    So, extract the hostname and feed to the messaging client for zeromq
    driver.

    For the record, ZeroMq is a very lightweight distributed messaging system
    specially designed for high throughput/low latency scenarios.
    Addition of support for ZeroMQ would help cinder scale out with high
    performance and be highly available as there is no centralised broker.

    DocImpact
    Document the configurations for ZeroMQ driver for Cinder

    Change-Id: Ic4b4301e5d7ca1692fc91155ba53f2dd12f99311
    Closes-Bug: #1440631
    partially Implements bp cinder-zeromq-support

[Sean McGinnis (sean-mcginnis)]

Vivek, please add information to this bug report so the docs folks know what needs to be added or updated in the documentation. It can then be switched over to the openstack-manuals project.

[Vivek Dhayaal (vivekdhayaal)]

As mentioned below :
https://review.openstack.org/#/c/277113/10/doc/source/devref/rpc.rst
ZeroMQ RPC messaging backend can be enabled by setting the below config option in cinder.conf
"rpc_backend=zmq"

Other optional ZeroMQ config options are available in the below link:
https://github.com/openstack/oslo.messaging/blob/master/oslo_messaging/_drivers/impl_zmq.py#L38-L100
(OR)
https://github.com/openstack/oslo.messaging/blob/76ab2c4f624204f181eff50c27c3aa192f14fc2a/oslo_messaging/_drivers/impl_zmq.py#L38-L100

Hi Sean, I think this is fine. Please review.

[Atsushi SAKAI (sakaia)]

It is related to config-reference.

if CONF.rpc_backend and CONF.rpc_backend == "zmq":
        # ZeroMQ RPC driver requires only the hostname.
        # So, return just that.
        return extract_host(host, 'host')
https://review.openstack.org/#/c/271848/11/cinder/volume/utils.py