Creating ReplicationController in Kubernetes Cluster using Terraform

What is Kubernetes replication for?

Before we go into how you would do replication, let’s talk about why. Typically you would want to replicate your containers (and thereby your applications) for several reasons, including:

  • Load balancing: Having multiple versions of a container enables you to easily send traffic to different instances to prevent overloading of a single instance or node. This is something that Kubernetes does out of the box, making it extremely convenient.
  • Scaling: When load does become too much for the number of existing instances, Kubernetes enables you to easily scale up your application, adding additional instances as needed.

Replication is appropriate for numerous use cases, including:

  • Microservices-based applications: In these cases, multiple small applications provide very specific functionality.
  • Cloud native applications: Because cloud-native applications are based on the theory that any component can fail at any time, replication is a perfect environment for implementing them, as multiple instances are baked into the architecture.
  • Mobile applications: Mobile applications can often be architected so that the mobile client interacts with an isolated version of the server application.

ReplicationController

A ReplicationController ensures that a specified number of pod replicas are running at any one time. In other words, a ReplicationController makes sure that a pod or a homogeneous set of pods is always up and available.

How a ReplicationController Works?

If there are too many pods, the ReplicationController terminates the extra pods. If there are too few, the ReplicationController starts more pods. Unlike manually created pods, the pods maintained by a ReplicationController are automatically replaced if they fail, are deleted, or are terminated. For example, your pods are re-created on a node after disruptive maintenance such as a kernel upgrade. For this reason, you should use a ReplicationController even if your application requires only a single pod. A ReplicationController is similar to a process supervisor, but instead of supervising individual processes on a single node, the ReplicationController supervises multiple pods across multiple nodes.

Terraform

Terraform is an open-source infrastructure as code software tool created by HashiCorp. It enables users to define and provision a datacenter infrastructure using a high-level configuration language known as HashiCorp Configuration Language, or optionally JSON.

Practical

In this practical, we are going to create a ReplicationController in Kubernetes cluster(minikube) using Terraform code.

Prerequisites

  1. Minikube.
  2. Kubectl(configured to minikube).
  3. Terraform.
  4. Visual Studio Code(with Terraform extension).

IN ● MLOps Engineer ● Linux Administrator ● DevOps and Cloud Architect ● Kubernetes Administrator ● AWS Community Builder ● Google Cloud Facilitator ● Author

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