The compute service components

The compute service is composed of multiple components that take care of incoming compute requests and then launch and manage instances, as depicted in the following diagram showing the Nova architecture:

Figure 4.1 – The Nova component architecture

Let’s explore each compute component in the following section.

API

The nova-api component deals with different (HTTP-based) requests via the queuing message service. Keep in mind that the API is the first interface that accepts compute requests before forwarding them to the next Nova component and establishing a complete workflow.

Scheduler

The next station in the Nova workflow abstraction layer is the nova-scheduler component. It is a major piece of the workflow that decides in which compute node each incoming instance creation request will run.

The scheduler component uses a variety of filters and preferences that can be customized to match different...