Open Stack

Hello,

During my working period related to the issue with the oslo.messaging
rabbitmq heartbeat [1],
I'd to studied how service consume oslo.messaging drivers to understand of
things works together and also the execution model behind the scene.

So during this period I wrote a walkthrough [2] to observe how nova-api use
and consume the oslo.messaging rabbitmq driver.

As I sayed, my walkthrough is focused on the studying of the nova-api, it
start from how service are runned (the puppet steps), through how nova-api
is runned by using mod_wsgi, to going to at least to how to nova-api
instanciate the oslo.messaging rabbitmq driver.

I also explain different solutions to fix the heartbeat rabbitmq driver
issue and more globaly why potentially we facing this problem with apache,
and the role of the MPM prefork module inside the issue.

I think that some parts of this article and especially my walkthrough  can
be useful for other persons and openstackers, so I want share it with you.

I surely wrote some erroned things in my article, so please do not hesitate
to fix it if you see one and to send me a pull request [3]. Else if see
other interesting things to add to it do not hesitate too.

Enjoy your reading and I hope you will find some useful info by reading my
article.

Thank you for your attention.

[1] https://bugs.launchpad.net/nova/+bug/1825584
[2]
https://herve.beraud.io/openstack/nova/oslo.messaging/rabbitmq/driver/2019/07/15/how-nova-consume-oslo-messaging.html
[3] https://github.com/4383/4383.github.io

-- 
Hervé Beraud
Senior Software Engineer
Red Hat - Openstack Oslo
irc: hberaud
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