Launching your Kubernetes Cluster with Deployment

What is Deployment in k8s?

A Kubernetes Deployment is an API resource that provides a declarative way to define the desired state of an application. It allows you to describe the application's components, the number of instances (replicas) to run, and how updates or rollbacks should be handled.

Deployment in Kubernetes (k8s) is a higher-level concept that helps manage pods and replicas. It ensures that a specified number of pod "replicas" are running at any given time.

A Deployment in Kubernetes:

• Specifies the desired state of the system (i.e., how many replicas should be running)
• Manages the pod creation, updates, and deletion
• Handles scaling (adding or removing replicas)
• Rolls back to a previous version in case of failure
• Supports updating pods and their replicas without any downtime (i.e., zero-downtime deployments)

Features of a Kubernetes Deployment

1. Declarative Configuration: You specify the desired state of your application, and Kubernetes takes care of achieving and maintaining that state.
2. Rolling Updates and Rollbacks: Deployments enable you to update your application without downtime by gradually replacing instances with new ones. If an update fails or you need to roll back to a previous version, Kubernetes can easily revert to the previous state.
3. Scaling: Deployments allow you to scale your application horizontally by adjusting the number of replicas, distributing the load across multiple instances.

Self-healing: If a pod (an instance of a running container) within a deployment fails, Kubernetes automatically replaces it to maintain the desired number of replicas.

apiVersion: apps/v1
kind: Deployment
metadata:
  name: example-deployment
spec:
  replicas: 3
  selector:
    matchLabels:
      app: example
  template:
    metadata:
      labels:
        app: example
    spec:
      containers:
      - name: example-container
        image: example-image:tag
        

• replicas: 3 specifies that there should be three instances (pods) of the application.
• selector is used to match pods with the labels specified in the template.
• The template section defines the pod template, including the container image to be used.