OpenStack Controller

The OpenStack Controller runs in a set of containers in a pod in Kubernetes. The OpenStack Controller is deployed as a Deployment with 1 replica only. The failover is provided by Kubernetes that automatically restarts the failed containers in a pod.

However, given the recommendation to use a separate Kubernetes cluster for each OpenStack deployment, the controller in envisioned mode for operation and deployment will only manage a single OpenStackDeployment resource, making the proper HA much less of an issue.

The OpenStack Controller is written in Python using Kopf, as a Python framework to build Kubernetes operators, and Pykube, as a Kubernetes API client.

Using Kubernetes API, the controller subscribes to changes to resources of kind: OpenStackDeployment, and then reacts to these changes by creating, updating, or deleting appropriate resources in Kubernetes.

The basic child resources managed by the controller are Helm releases. They are rendered from templates taking into account an appropriate values set from the main and features fields in the OpenStackDeployment resource.

Then, the common fields are merged to resulting data structures. Lastly, the services fields are merged providing the final and precise override for any value in any Helm release to be deployed or upgraded.

The constructed values are then used by the OpenStack Controller during a Helm release installation.

OpenStack Controller containers

Container

Description

osdpl

The core container that handles changes in the osdpl object.

helmbundle

The container that watches the helmbundle objects and reports their statuses to the osdpl object in status:children. See Status OsDpl elements for details.

health

The container that watches all Kubernetes native resources, such as Deployments, Daemonsets, Statefulsets, and reports their statuses to the osdpl object in status:health. See Status OsDpl elements for details.

secrets

The container that provides data exchange between different components such as Ceph.

node

The container that handles the node events.

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