- A Kubernetes Operator is a powerful pattern and tool used to automate the management of complex stateful applications on Kubernetes.
- Operators extend the Kubernetes API and leverage the native Kubernetes capabilities to manage application-specific tasks and lifecycle management.
- The goal of an Operator is to put operational knowledge into software.
- Operators typically provide controllers and Custom Resource Definitions (CRDs) that let you rapidly deploy new app instances without deep knowledge of their requirements or how they work.
An operator actively monitors the Kubernetes API for any alterations pertaining to a particular resource, like a custom resource definition (CRD). Upon detecting a change, the operator initiates actions to uphold the intended configuration of the resource. For instance, if a stateful set gains a new replica, the operator orchestrates the allocation of required resources and ensures seamless integration of the new replica into the set.
Operators employ a control loop mechanism to iteratively verify the status of the resources under their management, executing any required modifications as needed. This capability enables automatic handling of tasks such as scaling, failover, and other operations, eliminating the need for human intervention.
What might an operator look like in more detail? Here's an example:
- A Deployment that manages and monitors the pod.
The Operator Framework is an open-source toolkit designed to manage Kubernetes-native applications, referred to as Operators. Operators extend the capabilities of Kubernetes by automating the management of complex applications and resources. Using the Operator Framework, you can create, deploy, and manage custom resources, ensuring they maintain the desired state with minimal manual intervention.
The Operator Framework consists of three main components:
- Operator SDK: A set of tools and libraries for building operators. The SDK supports multiple languages and provides scaffolding, APIs, and utilities to simplify operator development.
- Operator Lifecycle Manager (OLM): A component that helps manage the lifecycle of operators and their associated resources. OLM handles tasks such as installation, updates, and dependency management, ensuring operators are consistently deployed and maintained.
- Operator Hub: A central repository for sharing and discovering operators. Operator Hub provides a catalog of pre-built operators that can be easily deployed in Kubernetes clusters.
- Go
- he most comprehensive and widely adopted language for writing Kubernetes operators.
- he most comprehensive and widely adopted language for writing Kubernetes operators.
- Ideal for developers who want detailed control and performance.
- Ansible
- nables writing operators using Ansible playbooks and roles.
- Suitable for those who prefer a declarative and configuration-driven approach.
- Great for users with existing Ansible automation knowledge, allowing them to leverage their skills to manage Kubernetes resources.
- Helm
- Allows the creation of operators using Helm charts.
- Useful for managing Kubernetes applications that are already packaged as Helm charts.
- Simplifies the transition to operator-based management by leveraging the existing Helm ecosystem.
- Prometheus
- ElasticSearch
- ISTIO
- ArgoCD
- MinIO
for more operators OperatorHub
Creation of an operator requires following softwares
- go version 1.21.0
- docker version 17.03+
- kubectl and access to kubernetes cluster
- operator sdk
Note*: I have choosen go as programming language to write an operator so I should have compatible go version installed.