Blue-green deployment is a widely used software release management strategy. It involves two identical hardware environments—one active and serving users while the other remains on standby. This approach facilitates smooth management of software updates and mitigates the risk of system downtime.
New code is initially released to staging environments, where it undergoes rigorous testing. Once the team approves the updated code, the router configuration is adjusted to switch the application traffic to the now-production environment. If any issues emerge, they revert to the previous production environment to continue using the original software version.
Some noteworthy benefits of blue-green deployments include:
Kubernetes is growing in popularity as an environment for development, testing, and production deployments. Although it simplifies application deployment, Kubernetes doesn't offer native blue-green deployment functionality out of the box. Instead, it provides a Deployment object that enables rolling updates, which can, to some extent, replace an application's pods with its latest version without any downtime.
Rolling deployments come with certain limitations. They can make rollbacks challenging and may require Kubernetes health checks to gauge the status of pods within a deployment. Additionally, rolling deployments can take longer compared to a pure blue-green pattern, where the switchover to a new version happens instantly.
To effectively implement blue-green deployments with Kubernetes, consider the following tools:
Argo Rollouts is an open-source set of Kubernetes controllers and Custom Resource Definitions (CRDs) that adds advanced deployment features such as blue-green and canary deployments, experiments, and other progressive delivery capabilities. It optionally integrates with Kubernetes ingress controllers and service meshes to manage traffic during updates. It can even query and interpret metrics from other systems to validate key performance indicators (KPIs) and automatically promote or roll back releases.
Flagger is a progressive delivery tool that automates the release process of applications running on Kubernetes. It decreases the risk of introducing new software versions into production by progressively diverting traffic to the updated version while assessing metrics and performing conformance tests. Flagger supports multiple deployment strategies, such as canary releases, A/B testing, and blue-green deployments, and integrates with various Kubernetes ingress controllers, service meshes, and monitoring systems.
GitLab CI/CD is a feature-packed DevOps platform that streamlines large software development projects. In addition to its code repository and issue tracking capabilities, GitLab offers CI/CD automation that supports both manually triggered deployments and scheduled deployments to Kubernetes production systems, including progressive deployment strategies like blue-green deployment.
CircleCI is a CI/CD platform that helps engineering teams build, test, and deploy software while keeping track of code changes in real-time via its dashboard UI. CircleCI supports deployment to Kubernetes clusters and integrates with other services for deployment strategies like feature flags, blue-green, and canary deployments.
This article has introduced the blue-green deployment pattern, its various benefits, and options for implementing this technique within a Kubernetes environment. By considering tools like Argo Rollouts, Flagger, GitLab CI/CD, or CircleCI, you can achieve smoother software releases, minimize downtime, and improve the overall experience for both developers and end-users in your Kubernetes environment. As you explore these tools, consider the unique requirements of your software development pipeline to identify the solution that best aligns with your team's needs.
