Blue/Green vs Canary Deployments

Introduction

Blue/green and canary deployments are core release strategies for minimizing risk in production. Both aim to reduce downtime and limit blast radius, but they have different operational trade-offs.

Blue/Green Deployment

Blue/green deployments maintain two identical environments. Traffic switches entirely from the old (blue) environment to the new (green) environment once validation completes.

Advantages

• Instant rollback by flipping traffic back.
• Minimal configuration complexity.
• Clean separation between versions.

Challenges

• Requires double capacity during deployment.
• Database changes must be backward compatible.

Canary Deployment

Canary deployments gradually shift traffic to a new version in stages.

Advantages

• Lower resource cost compared to blue/green.
• Allows metrics-based validation with real users.
• Suitable for large or highly regulated systems.

Challenges

• Requires advanced traffic routing and monitoring.
• Rollbacks may require more orchestration.

Choosing the Right Strategy

• Use blue/green when rapid rollback is critical and capacity is available.
• Use canary when you need progressive validation or have multiple traffic tiers.

Example: Versioned Endpoint in Spring Boot

A simple versioned endpoint can help confirm routing during a canary release.

@RestController
@RequestMapping("/api")
public class VersionController {
    @GetMapping("/version")
    public Map<String, String> version() {
        return Map.of(
            "service", "payments",
            "version", System.getenv().getOrDefault("APP_VERSION", "unknown")
        );
    }
}

Deployment Validation Checklist

• Confirm database migration compatibility.
• Validate metrics and logs before full traffic cutover.
• Ensure automated rollback on error thresholds.

Conclusion

Blue/green and canary deployments are both essential tools. The best choice depends on capacity constraints, regulatory requirements, and how much risk you can accept during releases.