Blue/Green Deployments

By Heba Eid
August 29, 2023

Blue/green deployment is a software deployment strategy used in the context of continuous delivery or continuous deployment.

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Deploying software updates to live environments has always been akin to walking on a tightrope. Traditional deployment methods often came wrapped with a set of challenges. Extended system downtimes, unanticipated bugs slipping into production, and the often tricky rollbacks when things didn’t pan out are some of the common pain points. For businesses, this translated to potential revenue losses, unhappy customers, and a stressed-out development team.

Enter the world of Blue/Green deployments, a technique that significantly reduces downtimes and simplifies deployments. In this blog post, we will zero in on this deployment approach to provide you with a comprehensive understanding of Blue/Green deployments.

What is a Blue/Green Deployment?

A Blue/Green deployment is a software release strategy where you gradually deploy a new feature or application using two separate production environments:

  • Blue Environment: This is the currently active version of the application, serving all user traffic. It represents stability and the known state of your service.
  • Green Environment: A perfect twin of the Blue, but with a pivotal difference—it holds the upcoming version of the application, primed for deployment after thorough testing.

Blue/Green DeploymentsBlue/Green Deployments

Having two mirror-image environments is a game-changer. It means that, at any given point, there's an environment readily available to absorb user traffic without interruption. Whether you're tweaking a minor feature or rolling out a major overhaul, you can do so in the Green environment without disturbing your active users. Once you're confident in the stability and efficiency of the updates in the Green environment, the switch can be made.

This seamless switching between Blue and Green ensures that users enjoy an uninterrupted experience, blissfully unaware of the profound changes that might be taking place behind the curtains. This duality and the ability to smoothly transition between versions have cemented Blue/Green deployment's position as a cornerstone of modern Kubernetes deployment strategies.

Benefits of Blue/Green Deployment

Embracing a Blue/Green deployment strategy, especially within the Kubernetes ecosystem, unlocks many advantages catering to developers and end users. Some of these benefits include:

  • Reduced Downtime: Downtime is drastically reduced by using two production environments and thoroughly testing the new release. Users experience almost uninterrupted service, bolstering trust and satisfaction.
  • Simplified Rollout and Automation: Seamless traffic switching between Blue and Green environments, especially with Kubernetes’ automation tools, makes deployments more predictable and less manual. This streamlined process saves time and ensures consistent deployment patterns.
  • Risk Mitigation: By testing changes in the Green environment first, potential errors are flagged and fixed before the live version is affected. This greatly minimizes disruptions and enhances application stability.
  • Faster Feedback Loops: With a clear distinction between live and new versions, developers can rapidly gather user feedback on the latest changes.
  • Continuous Improvements: A shorter feedback loop facilitates faster iterations and refines the development process, leading to a reliable product resonates with user needs.

How it works?

Navigating the Blue/Green deployment landscape can be likened to a well-choreographed dance, with each step meticulously planned to ensure a seamless transition between software versions. Here's how the process unfolds:

  1. Setting up the Blue environment: Establish the Blue environment, which is the current live version of your application. It's this environment that users interact with, and it serves as the baseline for the upcoming changes.
  2. Deploying to the Green environment: Parallel to Blue, the Green environment is set up. It's here that the new version of your application—be it bug fixes, feature additions, or other updates—is deployed, away from the prying eyes of users.
  3. Testing and verifying the Green environment: Before any switch is made, the Green environment undergoes rigorous testing. This ensures that the new changes work as intended and meet the required performance and security standards.
  4. Switching Traffic from Blue to Green: Once confident in the Green environment's stability, the pivotal moment arrives. Traffic is gradually rerouted from the Blue environment to the Green. This can be achieved using load balancers or other networking tools, ensuring that users now interact with the latest version of the application.
  5. Monitoring and Handling Potential Issues: Post-switch, continuous monitoring is imperative. This helps quickly identify and address any unforeseen issues that might arise, ensuring the user experience remains top-notch.
  6. Rolling Back (if necessary): One of the significant benefits of Blue/Green deployment is the safety net it provides. If, for any reason, the new version in the Green environment has any issues, there's always the option to roll back. By simply redirecting traffic back to the tried-and-tested Blue environment, service continuity is maintained while developers address the concern.

This structured approach ensures that updates, no matter how significant, are rolled out with minimal disruptions, providing both developers and users with a dependable and efficient deployment experience

Blue/Green Deployment with Flagger

What is Flagger?

Flagger, part of the GitOps toolset, is an open-source progressive delivery tool optimized for Kubernetes. It uses traffic-splitting policies to harness service meshes to control traffic flow between application versions. Flagger complements Flux CD and the GitOps family of projects and is compatible with numerous databases and alerting tools.

Flagger offers multiple deployment techniques, including Canary releases, A/B testing, and Blue/Green mirroring. It leverages service meshes like App Mesh, Istio, Linkerd, Kuma, and Open Service Mesh or ingress controllers such as Contour, Gloo, NGINX, Skipper, Traefik, and APISIX to direct traffic.

Using Flux CD & Flagger for Blue/Green Deployment

Blue/Green Deployment for gradual traffic switching

When executing a blue-green deployment approach, Flagger conducts checks on the canary pods to confirm their stability. If the results are positive, traffic smoothly transitions from the current version (blue) to the new one (green). Should any issues surpass the predefined failure limit, Flagger halts the traffic redirection. After successfully directing traffic to the canary (green), the original (blue) version gets updated to mirror the canary's specifications.

Blue/green mirroring for traffic shadowing

Traffic mirroring is an initial step in both Canary (progressive traffic shifting) and Blue/Green deployment tactics. It duplicates every incoming request, directing one to the primary and another to the canary service. While users receive responses solely from the primary, the canary's feedback gets ignored. The deployment's health is gauged by gathering metrics from both these requests, ensuring progression only when the canary's metrics are healthy.

De-Risk Deployments with Flagger & Weave GitOps

Flagger is part of Weave GitOps Enterprise- the fully automated platform powered by Flux CD, the CNCF project. Flux CD automates application deployment (CD) and oversees progressive delivery via automatic reconciliation with Flagger.

With Weave GitOps Enterprise, you can safely introduce new code to customers with progressive deployments, isolate and fix potential issues, and minimize deployment risks. Contact us for a demo today.

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