What Is Blue Green Deployment And How To Implement It

In the fast-paced world of software development, releasing updates frequently and reliably is paramount. However, traditional deployment methods often involve downtime and carry the risk of introducing bugs into production. The blue green deployment strategy offers an elegant solution to these challenges, enabling teams to release new application versions with minimal disruption and a straightforward rollback path.

Imagine you’re about to update a critical microservice for a popular mobile game during peak hours. Instead of a nerve-wracking, late-night deployment, you could seamlessly switch users to the new version with zero downtime. This is the power of blue green deployments. This article will explore what blue green deployment is, its benefits, challenges, and how you can implement this effective blue green deployment strategy.

What is Blue Green Deployment?

Blue green deployment(often styled as blue/green deployment or blue-green deployment is an application release model that involves running two identical production environments, often referred to as “Blue” and “Green.” Only one of these environments is live and serving production traffic at any given time.

Here’s the core idea:

• Blue Environment: This is the current, stable version of your application that is handling all live user traffic.
• Green Environment: This is an identical, idle environment where the new version of your application is deployed and thoroughly tested.

Once the new version in the Green environment is deemed ready and has passed all tests, traffic is switched from the Blue environment to the Green environment. The Green environment then becomes the new live production environment. The previous Blue environment is kept on standby, ready to take traffic back if any issues arise with the new version (a quick rollback). After a period of confidence in the new version, the old Blue environment can be decommissioned or updated to become the staging area for the next release.

This blue green deployment model aims to achieve zero-downtime deployments and reduce the risk associated with releasing new software versions.

How Does the Blue Green Deployment Process Work?

The blue green deployment approach follows a distinct set of steps:

1. Prepare Identical Environments: The fundamental prerequisite is having two production environments (Blue and Green) that are as identical as possible in terms of infrastructure, configuration, and data (or access to shared data stores). A router, load balancer, or service mesh is crucial to direct traffic to either environment.
2. Deploy to the Idle Environment (Green): The current live environment is Blue. The new version of the application is deployed to the Green environment.
3. Test the Green Environment: The Green environment undergoes rigorous testing. This can include automated tests, smoke tests, and even limited user acceptance testing (UAT) if desired, all while it’s isolated from live production traffic.
4. Switch Traffic: Once the Green environment is validated and considered stable, the router or load balancer is configured to redirect all incoming production traffic from the Blue environment to the Green environment. This switch is typically quick and seamless for end-users.
5. Monitor the New Live Environment (Green): After the switch, the Green environment (now live) is closely monitored for any unexpected issues, errors, or performance degradation.
6. Rollback (If Necessary): If problems arise with the Green environment, traffic can be quickly switched back to the stable Blue environment. This provides a simple and rapid rollback mechanism.
7. Promote Green to Blue: If the Green environment performs well and no critical issues are detected after a monitoring period, it officially becomes the new Blue (current production) environment. The old Blue environment (now idle) can be:
   • Kept as a hot standby for a longer period.
   • Taken offline and decommissioned.
   • Updated to become the Green environment for the next deployment cycle.

This cyclical process allows for continuous delivery with reduced risk.

Benefits of Blue Green Deployment

The blue green deployment pattern offers several significant advantages:

• Zero or Near-Zero Downtime: Traffic is switched almost instantaneously, meaning users experience no interruption during the deployment.
• Simple and Fast Rollback: If issues are detected in the new version, reverting to the previous stable version is as simple as switching the router back to the old environment. This significantly reduces the Mean Time To Recovery (MTTR).
• Reduced Deployment Risk: Extensive testing can be performed on the new version in an identical production environment without impacting live users. This catches many issues before they go live.
• Testing in a Production-Like Environment: The Green environment is essentially a clone of production, allowing for highly accurate testing.
• Confidence in Releases: The safety net of an easy rollback encourages more frequent releases and experimentation.
• Simplified Release Process: While the initial setup can be complex, the actual deployment and rollback steps are straightforward.

Challenges and Considerations for Blue Green Deployments

Despite its benefits, what are blue green deployments without their challenges? Here are some key considerations:

• Cost and Resource Overhead: Maintaining two identical production environments can double infrastructure costs, whether on-premises (hardware) or in the cloud (compute, storage).
• Database Schema Migrations: Managing database changes is a significant challenge. If the new application version requires schema changes that are not backward-compatible, the Blue and Green environments cannot simply share the same database. Strategies include:
  • Making schema changes backward and forward compatible.
  • Using database versioning and potentially separate database instances or read-replicas during the transition.
  • Making the database read-only during the switch, or using techniques to handle data synchronization.
• Managing Stateful Applications: For applications that maintain user session state, ensuring a seamless transition without losing session data requires careful planning (e.g., shared session stores, session draining).
• Long-Running Transactions: User transactions active during the switchover might be interrupted. Strategies to handle this include allowing transactions to complete on the old environment before routing new requests, or designing applications to be resilient to such interruptions.
• Complexity of Setup: Configuring the routing, load balancing, and environment duplication can be complex, especially for large, distributed systems.
• “Cold Starts” in the Green Environment: The newly activated Green environment might experience initial performance lag as caches warm up or connections are established. Warm-up routines or gradual traffic shifting can mitigate this.
• Shared Downstream Services: If both Blue and Green environments interact with shared third-party services or legacy systems, care must be taken to ensure these interactions don’t cause conflicts or data corruption.

Implementing Blue Green Deployment: Best Practices

To successfully implement a blue green deployment strategy, consider these best practices:

• Automate Everything: Automate the provisioning of environments, deployment process, testing, traffic switching, and rollback procedures as much as possible. This is crucial for consistency and speed, aligning well with DevOps blue green deployment principles.
• Comprehensive Testing in Green: Do not skimp on testing the Green environment. This includes functional tests, performance tests, and security scans.
• Monitor Both Environments: Implement robust monitoring and alerting for both Blue and Green environments. During the switch, closely monitor key metrics on the newly live environment.
• Database Versioning and Migration Strategy: Have a clear strategy for handling database schema changes. Decoupling schema changes from application code changes is often beneficial.
• Use Feature Flags: Feature flags can complement blue green deployments by allowing you to toggle new features on or off within the Green environment for testing, or even after it goes live, providing an additional layer of control.
• Infrastructure as Code (IaC): Use IaC tools (like Terraform or CloudFormation) to ensure that your Blue and Green environments are truly identical and can be provisioned consistently.
• Service Mesh / Load Balancer Configuration: Master your traffic routing tools. Modern service meshes (like Istio or Linkerd) and advanced load balancers offer fine-grained control over traffic shifting, which is essential for blue green deployments.

Blue Green Deployment in Kubernetes

Kubernetes, while offering rolling updates by default, doesn’t natively provide a “blue green” deployment strategy out-of-the-box in the same way. However, blue green deployments can be implemented in Kubernetes using various techniques:

• Manual Service Manipulation: You can manage two separate Deployments (Blue and Green) and manually update a Service to point its selector to the pods of the desired version.
• Tools like Argo Rollouts: Argo Rollouts is a Kubernetes controller that extends deployments to provide advanced strategies like blue green and canary. It automates the process of managing ReplicaSets for Blue and Green versions and updating the active service.

When using Argo Rollouts for a blue green deployment, the process typically involves:

1. Defining a Rollout custom resource specifying the blue green strategy.
2. The controller manages two ReplicaSets: one for the old (blue) version and one for the new (green) version.
3. An “active” Kubernetes Service points to the blue version initially. Optionally, a “preview” service can point to the green version for testing.
4. When an update is triggered (e.g., new image in the Rollout spec), the controller scales up the new ReplicaSet (green).
5. After the green version is ready and potentially after a manual approval or automated analysis, Argo Rollouts updates the active Service to point to the new (green) ReplicaSet.
6. The old (blue) ReplicaSet is then scaled down after a configurable delay.

This approach simplifies the implementation of blue green devops practices within Kubernetes environments.

Blue Green Deployment vs. Other Strategies

It’s useful to compare blue green deployments with other common strategies:

• Rolling Deployment: Gradually replaces instances of the old version with the new version. Slower rollout and rollback compared to blue green, but requires less infrastructure overhead.
• Canary Deployment: Releases the new version to a small subset of users first, then gradually increases exposure if no issues arise. Good for testing in production with real user traffic but more complex to manage traffic splitting and rollback.

The blue green strategy offers a balance of speed, safety, and simplicity for the switchover and rollback, provided the infrastructure overhead is acceptable.

Blue green testing often refers to the thorough validation performed on the green environment before it receives live traffic. This “test in production-like isolation” is a key strength of the blue green approach.

The blue green deployment methodology is a powerful technique for modern software delivery, particularly for applications requiring high availability and frequent updates. While it has its complexities, especially around data management and resource costs, the benefits of zero-downtime releases and simple, rapid rollbacks make it an attractive option for many organizations striving for agile and reliable deployments.

Thinking about optimizing your deployment pipelines? Understanding the performance of both your blue and green environments is crucial. Netdata can provide the real-time visibility you need during these critical transitions. Check out Netdata’s website to learn more.