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This blog will help you get started on deploying your REST API in Kubernetes. First, we'll set up a local Kubernetes cluster, then create a simple API to deploy.

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There are already a lot of free resources available explaining basic Kubernetes concepts, so go check those out first if you haven't already. This blog is intended for beginners but assumes you already have a basic understanding of Kubernetes and Docker concepts.

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1. Set Up Local Kubernetes

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There's a couple options for running Kubernetes locally, with the most popular ones including minikube, k3s, kind, microk8s. In this guide, any of these will work, but we will be using k3s because of the lightweight installation.

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Install k3d, which is a utility for running k3s. k3s will be running in Docker, so make sure you have that installed as well. We used k3d v4.0 in this blog.

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curl -s https://raw.githubusercontent.com/rancher/k3d/main/install.sh | bash
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Set up a cluster named test:

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k3d cluster create test -p "80:80@loadbalancer"
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Optionally, check that your kubeconfig got updated and the current context is correct:

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kubectl config view\nkubectl config current-context
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Optionally, confirm that k3s is running in Docker. There should be two containers up, one for k3s and the other for load balancing:

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docker ps
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Make sure that all the pods are running. If they are stuck in pending status, it may be that there is not enough disk space on your machine. You can get more information by using the describe command:

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kubectl get pods -A\nkubectl describe pods -A
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There's a lot of kubectl commands you can try, so I recommend checking out the list of resources and being aware of their short names:

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kubectl api-resources
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2. Create a Simple API

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We will create a simple API using Express.js.

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Set up the project:

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mkdir my-backend-api && cd my-backend-api\ntouch server.js\nnpm init\nnpm i express --save
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// server.js\nconst express = require("express");\nconst app = express();\n\napp.get("/user/:id", (req, res) => {\n  const id = req.params.id;\n  res.json({\n    id,\n    name: `John Doe #${id}`\n  });\n});\n\napp.listen(80, () => {\n  console.log("Server running on port 80");\n});
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Optionally, you can try running it if you have Node.js installed and test the endpoint /user/{id} with curl:

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node server.js\n\n// request:\ncurl http://localhost:80/user/123\n\n// response: {"id":"123","name":"John Doe #123"}
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Next, add a Dockerfile and .dockerignore:

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// Dockerfile\nFROM node:12\n\nWORKDIR /usr/src/app\nCOPY package*.json ./\nRUN npm i\nCOPY . .\n\nEXPOSE 80\nCMD ["node", "server.js"]
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// .dockerignore\nnode_modules
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Then, build the image and push it to the Docker Hub registry:

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docker build -t <YOUR_DOCKER_ID>/my-backend-api .\ndocker push <YOUR_DOCKER_ID>/my-backend-api
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3. Deploy

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Now, we deploy the image to our local Kubernetes cluster. We use the default namespace.

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Create a deployment:

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kubectl create deploy my-backend-api --image=andyy5/my-backend-api
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kubectl create -f deployment.yaml
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// deployment.yaml\napiVersion: apps/v1\nkind: Deployment\nmetadata:\n  name: my-backend-api\n  labels:\n    app: my-backend-api\nspec:\n  replicas: 1\n  selector:\n    matchLabels:\n      app: my-backend-api\n  template:\n    metadata:\n      labels:\n        app: my-backend-api\n    spec:\n      containers:\n      - name: my-backend-api\n        image: andyy5/my-backend-api
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Create a service:

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kubectl expose deploy my-backend-api --type=ClusterIP --port=80
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kubectl create -f service.yaml
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// service.yaml\napiVersion: v1\nkind: Service\nmetadata:\n  name: my-backend-api\n  labels:\n    app: my-backend-api\nspec:\n  type: ClusterIP\n  ports:\n  - port: 80\n    protocol: TCP\n    targetPort: 80\n  selector:\n    app: my-backend-api
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Check that everything was created and the pod is running:

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kubectl get deploy -A\nkubectl get svc -A\nkubectl get pods -A
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Once the pod is running, the API is accessible within the cluster only. One quick way to verify the deployment from our localhost is by doing port forwarding:

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kubectl port-forward my-backend-api-84bb9d79fc-m9ddn 3000:80
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curl http://localhost:3000/user/123
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To correctly manage external access to the services in a cluster, we need to use ingress. Close the port-forwarding and let's expose our API by creating an ingress resource.

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Create an Ingress resource with the following YAML file:

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kubectl create -f ingress.yaml\nkubectl get ing -A
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// ingress.yaml\napiVersion: networking.k8s.io/v1\nkind: Ingress\nmetadata:\n  name: my-backend-api\n  annotations:\n    ingress.kubernetes.io/ssl-redirect: "false"\nspec:\n  rules:\n  - http:\n      paths:\n      - path: /user/\n        pathType: Prefix\n        backend:\n          service:\n            name: my-backend-api\n            port:\n              number: 80
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curl http://localhost:80/user/123
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If you want to learn more on how to deploy using a managed Kubernetes service in the cloud, such as Google Kubernetes Engine, then check out the excellent guides on the official Kubernetes docs.

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