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Kubernetes Operators are processes connecting to the master API and watching for events, typically on a limited number of resource types. When a relevant event occurs, the operator reacts and performs a specific action. This may be limited to interacting with the master API only, but will often involve performing some action on some other systems (this could be either in cluster or off cluster resources). Operators are implemented as a collection of controllers where each controller watches a specific resource type.

In this post I will show you how to use Roles published to Ansible Galaxy as an Operator to manage an application in Kubernetes. Reusing a Role in this way provides an example of how to create an Operator that simply installs an application with the flexibility to expand and customize the behavior organically as requirements dictate. I will leverage both the Ansible Operator and the k8s module to demonstrate how you can use Ansible to create Kubernetes native applications.

Kubernetes Operators have now become mainstream. An Operator is essentially a Kubernetes Custom Controller managing one or more Custom Resources. The term Operator has become popular as it succinctly captures end result of what Custom Controller+Custom Resource combination is typically defined for, e.g.—declaratively managing a stateful software on Kubernetes (e.g.: databases, off-the-shelf web applications, ML workloads, etc.). In technical terms, Custom Controller+Custom Resource combination is called ‘Custom Resource Definition’ (CRD).

Running production quality databases in Kubernetes can be quite a hassle. But KubeDB promises to solve all your problems. Let’s have a quick look at this framework. You can count on KubeDB to solve your problems when running production quality databases in Kubernetes. KubeDB is a framework for writing operators for any database that support certain requirements. Namely: Create a database declaratively using CRD. Take one-off backups or period backups to various cloud stores, eg,S3, GCS, etc.

Red Hat’s Diane Mueller andSebastien Pahldive deep on the Kubernetes Operators at KubeCon 2018. Source: redhat.com