Event flow when a cloud instance is provisioned in Openstack

Many people think that cloud is alike virtualizastion or other way around. Both technologies have a lot of things in common and with a sophisticated virtualization manager or orchestration tool (example can be a VMware vCenter or vCloud) we get a look and feel that cloud promise but in essence cloud is not the same like virtualization.

In this post instead to polemize who is right or not I would like to rather take a look at the events that are happening when we provision a cloud server, either in cloud or VMware. The inside view is only for the Openstack although.

Problem

What is happening in the Openstack cluster when a cloud server is provisioned and booted.

Solution

Before a VM can be marked as booted and fully provisioned there are number or messages and requests exchanged between the core openstack components[4].

This slides show event after event what is happening: Openstack cloud request flow [2].
This diagram [3] below is an additional visualization of interaction between the components.

References

1. Python Code level analyse
   http://www.laurentluce.com/posts/openstack-nova-internals-of-instance-launching/
2. http://www.slideshare.net/mirantis/openstack-cloud-request-flow
3. Slides on Technical Architecture of Quantum (9/12) from the http://wiki.openstack.org/Quantum
4. http://www.openstack.org/software

High level Openstack software architecture

This is an overwhelming task of tracking code changes for Openstack projects as well as to maintain an up to date view of current software architecture model. As the number of core Openstack projects increase it drives as well as the overall complexity and communication patters between the them.

Below is a nice diagram that through visualization helps to represent the complexities and simplify the communications view between all components in Folscom Openstack release.

Sources

1. http://ken.pepple.info/openstack/2012/09/25/openstack-folsom-architecture/
2. http://ken.pepple.info/openstack/2012/02/21/revisit-openstack-architecture-diablo/