Kubernetes, often abbreviated as K8s, is an open-source platform designed to automate deploying, scaling, and operating application containers. It groups containers that make up an application into logical units for easy management and discovery. Kubernetes is widely used for orchestrating microservices due to its robust features and scalability.

A Kubernetes cluster consists of a set of worker machines, called nodes, that run containerized applications. Every cluster has at least one worker node.

A node is a worker machine in Kubernetes, which can be a virtual or a physical machine, depending on the cluster. Each node contains the necessary services to run pods and is managed by the master components.

A pod is the smallest and simplest Kubernetes object. It represents a single instance of a running process in your cluster. Pods contain one or more containers, such as Docker containers.

A Kubernetes service is an abstraction which defines a logical set of pods and a policy by which to access them. Services enable loose coupling between dependent pods.

A deployment provides declarative updates to applications. You describe a desired state in a deployment object, and the deployment controller changes the actual state to the desired state at a controlled rate.

Namespaces provide a mechanism for isolating groups of resources within a single cluster. They are intended for use in environments with many users spread across multiple teams or projects.

• Basic understanding of Docker and containerization.
• A working Docker installation.
• kubectl command-line tool installed.

Minikube is a tool that makes it easy to run Kubernetes locally. It runs a single-node Kubernetes cluster inside a VM on your laptop.

1. Install Minikube:

   curl -LO https://storage.googleapis.com/minikube/releases/latest/minikube-linux-amd64
   sudo install minikube-linux-amd64 /usr/local/bin/minikube
   

2. Start Minikube:

   minikube start
   

3. Verify Installation:

   kubectl get nodes
   

A deployment ensures that a specified number of pod replicas are running at any one time.

Apply the deployment:

Create a service to expose the deployment.

Apply the service:

Check the status of the pods and services.

1. Create a Docker Image: Create a simple Node.js application and Dockerize it.

   // app.js
   const express = require('express');
   const app = express();
   const port = 8080;
   
   app.get('/', (req, res) => {
     res.send('Hello, Kubernetes!');
   });
   
   app.listen(port, () => {
     console.log(`App running on port ${port}`);
   });
   

   # Dockerfile
   FROM node:14
   WORKDIR /app
   COPY . .
   RUN npm install
   EXPOSE 8080
   CMD ["node", "app.js"]
   

   Build and push the Docker image:

   docker build -t my-microservice-image:latest .
   docker tag my-microservice-image:latest <your-dockerhub-username>/my-microservice-image:latest
   docker push <your-dockerhub-username>/my-microservice-image:latest
   

2. Deploy on Kubernetes: Use the previously defined deployment.yaml and service.yaml files to deploy your microservice.

3. Access the Service: Use minikube service my-microservice to get the URL of the service and access it in your browser.

• Incorrect Image Name: Ensure the Docker image name in the deployment file matches the image you pushed to Docker Hub.
• Port Mismatch: Verify that the container port in the deployment file matches the port exposed by your application.
• Resource Limits: Set resource requests and limits in your deployment to avoid overloading nodes.

In this section, we covered the basics of Kubernetes and how to use it for orchestrating microservices. We learned about key concepts like clusters, nodes, pods, services, and deployments. We also walked through the process of setting up a Kubernetes cluster using Minikube and deploying a simple microservice. By understanding these concepts and practices, you are now equipped to manage and scale your microservices effectively using Kubernetes.