Rolling Deployment in Kubernetes

Kubernetes, the open-source container orchestration platform, has revolutionized the way applications are deployed and managed. Among its powerful features, rolling deployment stands out as a key strategy for updating applications seamlessly without causing downtime. In this article, we'll delve into the concept of rolling deployment in Kubernetes, exploring its significance, benefits, and the step-by-step process to implement it effectively.

1. Understanding Rolling Deployment:

   • Definition and Purpose
   • Key Benefits

2. Preparing Your Kubernetes Cluster:

   • Ensuring Cluster Readiness
   • Verifying Kubernetes Versions

3. Deploying Your Application:

   • Containerizing Your Application
   • Creating Deployment YAML

4. Rolling Update Strategy:

   • Setting Update Policies
   • Defining Replication Controllers

5. Executing a Rolling Deployment:

   • Applying Deployment YAML
   • Monitoring Deployment Progress

Commands:

Let's start by understanding the basic commands used in Kubernetes for a rolling deployment.

# Check Kubernetes cluster nodes
kubectl get nodes

# Verify Kubernetes version
kubectl version

# Create a Kubernetes deployment YAML file
kubectl create deployment <deployment-name> --image=<image-name>

# Set update strategy for rolling deployment
kubectl set image deployment/<deployment-name> <container-name>=<new-image-name>

# Monitor deployment progress
kubectl rollout status deployment/<deployment-name>

Step-by-Step Instructions:

Step 1: Understanding Rolling Deployment

Definition and Purpose:

Rolling deployment is a strategy that allows updates to be applied gradually, node by node, ensuring continuous availability of the application. This minimizes downtime and provides a smooth transition between versions.

Key Benefits:

• Zero Downtime: Users experience uninterrupted service during the update.
• Rollback Capability: Easily revert to the previous version in case of issues.
• Resource Optimization: Efficient utilization of resources with controlled updates.

Step 2: Preparing Your Kubernetes Cluster

Ensuring Cluster Readiness:

Before initiating a rolling deployment, ensure that your Kubernetes cluster is healthy and all nodes are ready.

kubectl get nodes

Verifying Kubernetes Versions:

Check the compatibility of your application with the Kubernetes version running on your cluster.

kubectl version

Step 3: Deploying Your Application

Containerizing Your Application:

Ensure your application is containerized using Docker or any other containerization tool.

Creating Deployment YAML:

Create a deployment YAML file specifying the container image and desired replicas.

kubectl create deployment <deployment-name> --image=<image-name>

Step 4: Rolling Update Strategy

Setting Update Policies:

Define the rolling update strategy by configuring the deployment YAML file.

kubectl set image deployment/<deployment-name> <container-name>=<new-image-name>

Defining Replication Controllers:

Ensure the replication controllers are correctly set to manage the desired number of replicas.

Step 5: Executing a Rolling Deployment

Applying Deployment YAML:

Initiate the rolling deployment by applying the updated deployment YAML file.

kubectl apply -f <deployment-file.yaml>

Monitoring Deployment Progress:

Monitor the deployment progress to ensure a smooth transition.

kubectl rollout status deployment/<deployment-name>

More Examples:

Here are a few examples of rolling deployment scenarios:

• Blue-Green Deployment: Running two separate environments simultaneously, switching traffic instantly.
• Canary Deployment: Gradually rolling out the update to a small subset of users for testing before full deployment.