Blue-green deployment vs canary release: Choosing a deployment strategy

Blue-green deployment

Blue-Green deployment is a strategy that maintains two identical production environments, called “Blue” and “Green.” At any time, only one of these environments is live and serving all production traffic. When a new version of software is ready, it is deployed to the inactive environment. After testing and validation, traffic is switched from the active to the previously inactive environment, making the new version live. This switch can be done quickly, often by simply changing a load balancer configuration.

This approach minimizes downtime and risk because the entire platform is deployed and tested before any users are directed to it. If any issues arise after the switch, traffic can be immediately routed back to the previous environment, providing a fast rollback mechanism. Blue-Green deployments are particularly useful for organizations that cannot tolerate downtime but need to regularly update their applications.

Canary release

Canary release is a deployment strategy where a new version of an application is gradually rolled out to a small subset of users before being deployed to the entire user base. Initially, a small percentage of traffic is directed to the new version while most users continue to use the stable version. This allows teams to monitor performance, gather user feedback, and detect any issues in a production environment with minimal impact.

As confidence in the new version increases, the percentage of traffic routed to it can be incrementally increased until all users are on the new version. Named after the historical practice of using canaries in coal mines to detect toxic gases, this approach helps detect problems early with minimal user impact. If problems are found, only a small subset of users is affected, and traffic can be quickly routed back to the stable version.

Comparison: Blue-green vs. canary releases

Risk Exposure:

• Blue-Green: All users are switched simultaneously, exposing the entire user base to potential issues at once.

• Canary: Only a subset of users is initially exposed to changes, limiting the impact of potential issues.

Rollout Speed:

• Blue-Green: Typically faster as the switch happens all at once after validation.

• Canary: Generally slower as it involves gradual, incremental rollout over time.

Infrastructure Requirements:

• Blue-Green: Requires maintaining two complete production environments simultaneously.

• Canary: Can be implemented with a single environment plus additional instances for the canary version.

Feedback Collection:

• Blue-Green: Limited real user feedback before full deployment, relying more on pre-deployment testing.

• Canary: Provides real user feedback from the subset of users on the new version before full rollout.

Rollback Complexity:

• Blue-Green: Simple rollback process by switching traffic back to the previous environment.

• Canary: Rollback involves redirecting the canary traffic back to the stable version.

Cost Considerations:

• Blue-Green: Higher cost due to maintaining two full production environments.

• Canary: Can be more cost-effective as it may not require a complete duplicate environment.

Feature flags with deployment strategies

Feature flags integrate seamlessly with Blue-Green deployments by allowing teams to deploy code in an inactive state to the Green environment, with features turned off by default. Once the Green environment becomes live, features can be gradually enabled without requiring additional deployments. This provides an additional safety layer, as problematic features can be disabled without rolling back the entire deployment. Teams can also use feature flags to perform A/B testing between the environments or to enable certain features for specific user segments even after the full traffic switch has occurred.

In Canary releases, feature flags offer powerful complementary capabilities by enabling fine-grained control over which features are exposed to canary users. Organizations can deploy a new version with multiple features disabled, then selectively enable them for the canary group to isolate and evaluate each change independently. This granular approach helps pinpoint the source of any issues that arise during the canary phase. Feature flags also allow teams to quickly disable problematic features for canary users without reverting the entire deployment, making the canary approach even more robust and flexible for testing new functionality in production.

Blue-green deployment and canary release are both deployment strategies aimed at minimizing risk when releasing software updates. Blue-green deployment involves maintaining two identical production environments, with only one active at a time. When a new version is ready, traffic is switched from the active environment (blue) to the inactive one (green) that contains the updated code. This approach offers a quick rollback mechanism—if issues arise, traffic can be immediately redirected back to the original environment. It also eliminates downtime since the switch happens instantaneously. However, blue-green deployments require duplicating infrastructure resources, which increases costs. Additionally, database schema changes can be challenging to manage, and the all-or-nothing nature of the switch means that all users experience the new version simultaneously, potentially exposing all users to undiscovered issues.

Canary releases take a more gradual approach by rolling out updates to a small subset of users before expanding to the entire user base. This controlled exposure allows teams to monitor the performance and stability of the new version with real users while limiting potential negative impact. Canary deployments are particularly effective at catching issues that might only appear under specific user conditions or at scale. They’re ideal when you need to validate changes in a production environment with minimal risk. However, canary releases are more complex to implement, requiring sophisticated traffic routing capabilities and robust monitoring systems. They also take longer to complete a full deployment compared to blue-green. Choose blue-green deployment when you need zero-downtime updates with simple rollback options and when your application can handle the all-at-once transition. Opt for canary releases when dealing with critical applications where you need to carefully measure impact before full deployment, or when you want to test new features with specific user segments.

Frequently asked questions

What is the best insurance for blue-green deployment?

The best insurance for blue-green deployment is its quick rollback capability. Since you maintain two identical production environments (Blue and Green) with only one active at a time, if any issues arise after switching traffic to the new environment, you can immediately route traffic back to the previous environment. This provides a fast and reliable rollback mechanism that minimizes the impact of problematic deployments, essentially serving as an insurance policy against deployment failures.

How does blue-green deployment compare to canary deployment?

Blue-green deployment switches all users simultaneously to a new environment after validation, while canary deployment gradually routes a small percentage of users to the new version before full rollout. Blue-green is typically faster but exposes all users to potential issues at once, while canary limits risk by exposing only a subset of users initially. Blue-green requires two complete production environments, making it more costly but offering simpler rollbacks. Canary deployment provides real user feedback before full deployment and can be more cost-effective but requires more sophisticated traffic routing and monitoring capabilities.

Can you provide an example of a blue-green deployment?

In a blue-green deployment, imagine a web application running in the Blue environment serving all current production traffic. When a new version is ready, it’s deployed to the inactive Green environment where it undergoes testing and validation without affecting users. Once verified, traffic is switched from Blue to Green by updating the load balancer configuration, making the new version live. The previously active Blue environment becomes inactive but remains available for immediate rollback if needed. The next deployment would then target the Blue environment, continuing the alternating pattern.

How is AWS used for blue-green deployment?

AWS provides several services that facilitate blue-green deployments. AWS Elastic Beanstalk supports blue-green deployments through its deployment policies. AWS CodeDeploy offers built-in blue-green deployment capabilities where it provisions new instances for the green environment and automatically routes traffic after successful deployment. Amazon Route 53 (DNS service) or Application Load Balancers can be configured to switch traffic between environments. For containerized applications, Amazon ECS and EKS allow you to run multiple versions of your application and easily shift traffic between them. These AWS services simplify the implementation of blue-green deployments while providing the necessary infrastructure redundancy.

What strategies are involved in blue-green deployment?

Key strategies in blue-green deployment include maintaining identical Blue and Green environments with only one active at a time, comprehensive testing in the inactive environment before any traffic switch, implementing database compatibility strategies to handle schema changes across both environments, using load balancers or DNS changes for traffic switching, monitoring the new environment after switchover to quickly identify issues, and having a well-defined rollback plan. Feature flags can be integrated to deploy code in an inactive state and gradually enable features after the environment goes live, providing an additional safety layer without requiring new deployments.