Restarting a Kubernetes Pod

by Tola Ore-Aruwaji

Kubernetes, a powerful container orchestration platform that enables developers to automate, scale, and manage containerized applications. Pods are central to Kubernetes, the smallest and simplest units that run containers. Kubernetes Services enable communication between different components within and outside a cluster. By connecting Kubernetes Pods to Services, you can ensure stable network access and load balancing for your applications.

Service and Pod Connection:

Kubernetes Services work as an abstraction layer that routes incoming traffic to the appropriate Pods. The connection between a Kubernetes Pod and a Service is established through labels and selectors.

  • Labels: Labels are key-value pairs attached to Kubernetes objects, including Pods, that help organize and categorize resources. For instance, you can label a group of Pods that serve a particular function, like app=backend.
  • Selectors: A selector is used by a Kubernetes service to determine which Pods should receive traffic. In the Service definition, you specify a selector that matches the labels of the target Pods.

How Pods Connect to Services:

  • Label the Pods: First, ensure that the Pods you want to connect to a Service have appropriate labels. In the Pod definition, you can add labels under the metadata section.
  • Define the Service: Create a YAML file for your Service and specify the selector that matches the labels of the target Pods. The Service will route traffic to the Pods with matching labels.
  • Expose Ports: In the Service definition, specify the port on which the Service listens for incoming traffic and the target port on the backend Pods where the traffic is forwarded.

In this article, we'll explain how Kubernetes Pods connect to Services and the underlying mechanics that make it possible.

Create a Kubernetes Deployment

To create a Kubernetes deployment, write a YAML template file describing your deployment configuration and then use kubectl to create the pod based on the template. In this tutorial, we’ll use the Nginx image to create our Kubernetes deployment.

  • Create a yaml file, and add the Kubernetes deployment configuration.
apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx-deployment-workflow
spec:
  replicas: 1
  selector:
    matchLabels:
      app: nginx
  template:
    metadata:
      labels:
        app: nginx
    spec:
      containers:
      - name: nginx-container-workflow
        image: nginx:latest
        ports:
        - containerPort: 80

This YAML file defines a Pod with an Nginx container using the latest Nginx image from Docker Hub. The container listens on port 80.

  • Next, create the pod in your terminal using kubectl create -f <deployment_file_name.yaml>

  • Verify if your pods are running using kubectl get deployment

Creating a Kubernetes Service

A Kubernetes Service is a stable and abstract way to expose an application running on a set of Pods as a network service within a Kubernetes cluster or externally. Services provide networking capabilities such as load balancing, service discovery, and stable IP addresses or DNS names to access the application, regardless of where the Pods are running or if they are rescheduled.

  • Create a Kubernetes service in your yaml file and the following service configuration: 
apiVersion: v1
kind: Service
metadata:
  name: nginx-service
spec:
  selector:
    app: nginx
  ports:
    - protocol: TCP
      port: 80
      targetPort: 80
  type: LoadBalancer
  • Next, create your Kubernetes service using kubectl create -f <kubernetes_service_file.yaml>

  • Verify if your service is running using kubectl get service You’ll see your external IP address for your nginx-service

Copy the IP address and paste it into your browser. You’ll be able to access your Nginx resource.

Restarting a Kubernetes Pod

To restart a Kubernetes Nginx Pod, you can delete the existing Pod, and Kubernetes will automatically create a new one to replace it. Here's how to do it:

First, identify the name of the Nginx Pod you want to restart. You can list all the running Pods with: kubectl get pods

  • Delete your pod using the kubectl delete pod nginx-deployment-workflow-859cc56685-44n7n command.
  • Confirm if your Pod was automatically created using kubectl get pods you should see your pod with a unique name and a running status.

Conclusion

In conclusion, understanding the intricacies of Kubernetes Pods and Services and the strategies to manage and restart Pods is essential for successfully deploying and maintaining containerized applications in a Kubernetes cluster. This blog post has provided valuable insights and best practices to help you harness the full potential of these fundamental Kubernetes components, ensuring your applications are scalable, resilient, and highly available.