Blue Green Deployment vs. Canary: 5 Key Differences and How to Choose

What Is Blue Green Deployment? 

Blue-green deployment is a release management strategy that involves having two identical production environments—one known as “Blue,” and the other “Green.” These environments are designed to be exact replicas of each other, containing the same resources, infrastructure, and configurations. The primary goal of blue-green deployment is to minimize downtime and reduce the risk of introducing new software versions by allowing you to switch between these environments seamlessly.

When you deploy a new version of your application, you do so in the inactive environment (say, Green). This allows you to test the new version thoroughly, ensure that it’s stable, and make any necessary adjustments without affecting your users. Once you’re confident that the new version is reliable, you can switch users to the Green environment, making it the new active production environment. The previously active Blue environment now becomes the standby, ready to receive the next deployment.

This is part of a series of articles about software deployment

What Is Canary Deployment? 

Canary deployment is another release management strategy that allows you to roll out new software versions to a small, controlled group of users before deploying it to the entire user base. Named after the “canary in a coal mine” analogy, this method helps you identify and address any potential issues with the new release before it affects all users, thus minimizing the risk of a widespread problem or outage.

In canary deployment, you gradually roll out the new version of your application to a percentage of users, monitor their feedback and performance, and iterate on any issues that may arise. If the new version performs well and receives positive feedback, you can proceed with a full-scale release. On the other hand, if you encounter any problems, you can pause the rollout, address the issues, and then continue the process. This incremental approach helps ensure that any potential problems are detected and resolved early on, reducing the risk of a catastrophic failure.

How Do Blue Green Deployment and Canary Deployment Work? 

To better understand the differences between blue-green and canary deployments, let’s take a closer look at how each strategy works in practice.

Blue-Green Deployment

  • Preparation: Set up a staging environment—this will be the Green environment—with identical infrastructure, resources, and configurations as the production environment.
  • Deployment: Deploy the new version of your application to the inactive environment (e.g., Green).
  • Testing: Thoroughly test the new version in the inactive environment, making any necessary adjustments to ensure it’s stable and reliable.
  • Switch: Once you’re confident in the new version, switch users to the inactive environment (Green), making it the new active production environment.
  • Standby: The previously active environment (Blue) can now serve as standby, ready to receive the next deployment. Alternatively, to conserve costs, it can be torn down and redeployed when a new version is ready to test.

Learn more in our guide to blue green deployment

Canary Deployment

  • Preparation: Set up a traffic rerouting mechanism that enables directing part of the traffic, based on certain criteria, to a different version of the software..
  • Deployment: Deploy the new version and divert a small percentage of your user base in the production environment to that version.
  • Monitoring: Monitor user feedback and performance metrics for the new version, iterating on any issues that arise.
  • Rollout: If the new version performs well and receives positive feedback, gradually roll it out to the rest of your user base. If problems are encountered, pause the rollout, address the issues, and then continue the process.

Learn more in our guide to canary deployment

Blue Green Deployment vs. Canary Deployment: 5 Key Differences 

Now that we have a clear understanding of how Blue-Green and Canary Deployments work, let’s examine the key differences between these strategies and their implications for your projects.

1. Speed and Ease of Deployment

One of the main advantages of blue-green deployment is the speed and ease with which you can deploy new software versions. Since you have two identical environments, you can switch between them almost instantaneously, minimizing downtime and ensuring a seamless user experience. Another advantage is that in most applications, it is easy to support blue/green deployment. This is not the case for canaries, because to support canary deployment, the application must be designed to run two different versions at the same time.

Canary deployment, on the other hand, requires a more gradual and incremental approach. You must carefully monitor user feedback and performance metrics, making adjustments as needed, before rolling out the new version to your entire user base. This can be a more time-consuming process but allows for greater control and risk mitigation. In addition, canaries are more complex because they require a traffic rerouting mechanism that can gradually shift part of the traffic to the canary. In contrast, blue/green deployment only needs a simple network switch or load balancer.

2. Risk Management

Both blue-green and canary deployments are designed to minimize the risk of introducing new software versions, but they do so in different ways.

Blue-green deployment focuses on thorough testing and validation in the inactive environment before switching users to the new version. This ensures that any issues are detected and resolved before the new version becomes active, reducing the likelihood of a widespread problem or outage. Canary deployment, on the other hand, relies on a more iterative approach, gradually rolling out the new version to users and monitoring their feedback and performance metrics. This allows you to detect and address any potential problems early on, before they affect your entire user base.

3. Resource Requirements

Blue-green deployment requires more resources than canary deployment, as you must maintain two identical production environments. This can be expensive for smaller organizations or projects with limited budgets. However, with modern resource provisioning, it is possible to tear down the Green environment when the deployment ends and reinstate it only when a new version is ready to deploy.

Canary deployment is more resource-efficient, as you only need to set up a staging environment for testing and deploy new versions to a small percentage of your user base initially. This makes it more accessible for projects with constrained resources.

4. Rollback Capabilities

In the event of an issue with the new version, both blue-green and canary deployments provide rollback capabilities, but the process differs between the two strategies.

With blue-green Deployment, you can quickly revert to the previous version by switching users back to the inactive environment. This can be done almost instantaneously, minimizing downtime and ensuring a seamless user experience.

Canary deployment allows you to pause the rollout if problems are detected, address the issues, and then continue the process. If necessary, you can also roll back to the previous version by redirecting affected users back to the original release.

5. User Impact

The impact on users is another critical factor to consider when choosing between blue-green and canary deployments.

On the one hand, blue-green deployment reduces user impact by thoroughly testing the new version in the inactive environment before switching users to it. This ensures that they’re not exposed to any issues or disruptions during the deployment process. However, in case of problems with the new deployment, the entire user base will be exposed to them. Blue-green deployments are an all-or-nothing approach.

Canary deployment exposes a small percentage of users to the new version initially, which means that they may encounter issues or disruptions as you iterate on the release. However, this strategy allows you to identify and address problems early on, before they affect the entire user base.

Learn more in our detailed guide to rolling deployment

Choosing Between Blue-Green and Canary Deployments 

Choosing between blue-green and canary deployments ultimately depends on your specific needs, resources, and risk tolerance.

If you prioritize speed and ease of deployment, have sufficient resources to maintain two identical production environments, and are confident in your ability to thoroughly test and validate new releases, blue-green deployment may be the best choice for you.

On the other hand, if you have limited resources or prefer a more iterative and controlled approach to risk management, canary deployment may be a better fit.

Ultimately, both strategies have their strengths and weaknesses, and the best choice will depend on your unique requirements and circumstances. By understanding the key differences between blue-green and canary deployments, you can make an informed decision that best meets your needs and ensures the success of your software projects.

Advanced Progressive Delivery in Kubernetes with Argo Rollouts and Codefresh

Codefresh offers advanced progressive delivery methods, including blue green and canary deployment, by leveraging Argo Rollouts, a project specifically designed for gradual deployments to Kubernetes.

Through Argo Rollouts, Codefresh can perform advanced canary deployments that support:

  • Declarative configuration – all aspects of the blue/green deployment are defined in code and checked into a Git repository, supporting a GitOps process.
  • Pausing and resuming – pausing a deployment and resuming it after user-defined tests have succeeded.
  • Advanced traffic switching – leveraging methods that take advantage of service meshes available on the Kubernetes cluster.
  • Verifying new version – creating a preview service that can be used to verify the new release (i.e smoke testing before the traffic switch takes place).
  • Improved utilization – leveraging anti-affinity rules for better cluster utilization to avoid wasted resources in a canary deployment.
  • Easy management of the rollout – view status and manage the deployment via the new Applications Dashboard.

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