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/2019/0... [3] https://github.com/4383/4383.github.io -- Hervé Beraud Senior Software Engineer Red Hat - Openstack Oslo irc: hberaud -----BEGIN PGP SIGNATURE----- wsFcBAABCAAQBQJb4AwCCRAHwXRBNkGNegAALSkQAHrotwCiL3VMwDR0vcja10Q+ Kf31yCutl5bAlS7tOKpPQ9XN4oC0ZSThyNNFVrg8ail0SczHXsC4rOrsPblgGRN+ RQLoCm2eO1AkB0ubCYLaq0XqSaO+Uk81QxAPkyPCEGT6SRxXr2lhADK0T86kBnMP F8RvGolu3EFjlqCVgeOZaR51PqwUlEhZXZuuNKrWZXg/oRiY4811GmnvzmUhgK5G 5+f8mUg74hfjDbR2VhjTeaLKp0PhskjOIKY3vqHXofLuaqFDD+WrAy/NgDGvN22g glGfj472T3xyHnUzM8ILgAGSghfzZF5Skj2qEeci9cB6K3Hm3osj+PbvfsXE/7Kw m/xtm+FjnaywZEv54uCmVIzQsRIm1qJscu20Qw6Q0UiPpDFqD7O6tWSRKdX11UTZ hwVQTMh9AKQDBEh2W9nnFi9kzSSNu4OQ1dRMcYHWfd9BEkccezxHwUM4Xyov5Fe0 qnbfzTB1tYkjU78loMWFaLa00ftSxP/DtQ//iYVyfVNfcCwfDszXLOqlkvGmY1/Y F1ON0ONekDZkGJsDoS6QdiUSn8RZ2mHArGEWMV00EV5DCIbCXRvywXV43ckx8Z+3 B8qUJhBqJ8RS2F+vTs3DTaXqcktgJ4UkhYC2c1gImcPRyGrK9VY0sCT+1iA+wp/O v6rDpkeNksZ9fFSyoY2o =ECSj -----END PGP SIGNATURE-----