What are blue/green deployments?
Blue/green deployment is a strategy that improves application availability and minimizes downtime and risks during deployments. This approach uses two identical production environments called blue and green. The “blue” environment is the outgoing live environment, while the “green” environment serves as the next version in readiness. Once changes are fully tested in “green,” traffic is switched from “blue” to “green.” This swift traffic transition minimizes downtime, and issues can be quickly addressed by reverting back to “blue.”
A key advantage of blue/green deployment is its simplicity in switching back environments if problems arise. The process typically involves a load balancer directing traffic accordingly. However, it requires enough resources to run two complete environments simultaneously, which might not be feasible for all organizations.
What are canary deployments?
Canary deployment is a technique aimed at mitigating risks by gradually rolling out updates to a subset of users before full release. This strategy lets you incrementally deploy new features or updates, reducing the chance of widespread issues. Initially, only a small percentage of users, called “canaries,” are exposed to the changes. This helps you find potential bugs or performance issues within a limited scope, safeguarding the broader user base from immediate impacts if something goes wrong.
The advantage of canary deployment lies in its ability to gauge user responses and system performance in real-time within a controlled group. By observing smaller groups, you can collect valuable feedback and make necessary adjustments before full-scale deployment. However, this method requires significant monitoring and potentially complex routing configurations to manage traffic distribution accurately.
This is part of a series of articles about software deployment.
How blue/green and canary deployments work
The blue/green deployment workflow
The workflow for a blue/green deployment typically follows these steps:
- Prepare the green environment: Set up the “green” environment as a mirror of the existing “blue” environment. This includes replicating the infrastructure, configurations, and dependencies. The new version of the application is deployed to the green environment.
- Test the green environment: Perform thorough testing in the green environment, including functional tests, integration tests, and performance tests, to ensure the application meets requirements.
- Switch traffic: Once the green environment is verified, update the load balancer to direct user traffic from the blue environment to the green environment. This switchover is instantaneous, ensuring minimal downtime.
- Monitor the green environment: After the switch, closely monitor the green environment to detect any issues. Use metrics, logs, and feedback to assess application stability and performance.
- Decommission the blue environment: If no issues are detected in the green environment, the blue environment can be decommissioned or repurposed. If problems arise, the load balancer can quickly redirect traffic back to the blue environment.
Canary deployment workflow
The canary deployment process unfolds in gradual stages:
- Deploy the new version to a canary group: Start by deploying the updated application to a small subset of servers or users (the canary group). These users receive the new version, while the rest continue using the old version.
- Monitor and analyze: Collect and analyze metrics from the canary group, such as error rates, response times, and user feedback. Monitoring tools and logs play a crucial role in identifying potential issues early.
- Gradually expand rollout: If the canary group shows no critical issues, increase the number of users or servers receiving the new version. This step-by-step expansion minimizes risks while progressively introducing the new version.
- Rollback if necessary: If problems arise at any stage, you can pause rollout and decide whether to roll forward to a new version that fixes the issue, or roll back to the previous version. This step ensures that the impact of issues remains localized to the current canary group or stage.
- Full deployment: Once you’ve validated the new version across increasingly larger groups, complete the rollout to all users or servers. Continue monitoring during and after the full deployment to ensure stability.
Related content: Read our guide to Continuous Deployment.
Tony Kelly is a DevOps marketing leader who drives innovation and awareness of the latest trends in Continuous Delivery.
Key differences between blue/green and canary deployments
1. Rollout strategy
Blue/green deployment involves a complete switchover of user traffic from the old (blue) environment to the new (green) environment in a single action. The deployment process is binary: users are either on the old version or the new version, with no overlap.
Canary deployment takes a phased approach, gradually introducing the new version to a small subset of users or servers first. As confidence in the new version’s stability increases, its exposure is expanded incrementally until it reaches the entire user base.
2. Downtime
Blue/green deployment is specifically designed to achieve zero or near-zero downtime during the transition. Because the green environment is fully prepared and tested before traffic is switched, the transition is instantaneous, ensuring uninterrupted service for end users. If problems occur, the traffic can quickly revert to the blue environment with minimal disruption.
Canary deployment can also achieve minimal downtime, but the rollout is slower due to the incremental nature of the process. While new changes are introduced in stages, the system continues to run the old version for the majority of users until the final stages of deployment.
3. Risk mitigation
In blue/green deployment, risk mitigation is achieved by maintaining two identical environments, with the option to revert to the stable (blue) environment if issues arise. This instant rollback capability ensures that any critical problems with the green environment do not impact users for long. However, the scope of potential issues is broader since all users are exposed to the new version at the same time.
Canary deployment mitigates risk by limiting the new version’s exposure to a small group of users, often referred to as the “canaries.” If an issue arises, it affects only this small group, making it easier to isolate, diagnose, and resolve. The gradual rollout also allows for continuous monitoring and validation at each stage.
4. Resource requirements
Blue/green deployment requires the availability of two fully functional environments, which can significantly increase resource usage. Both the old and new environments need to run concurrently, at least temporarily, meaning infrastructure costs may double during the deployment process. This requirement may be challenging for organizations with limited resources or strict budget constraints.
Canary deployment is less demanding in terms of infrastructure, as it typically leverages the same environment and gradually shifts traffic to the new version. However, it requires sophisticated traffic management and monitoring systems to ensure a smooth rollout. While the resource costs are lower than for blue/green deployments, the complexity of configuration and traffic management is higher.
5. Feedback opportunities
Canary deployment provides a distinct advantage in terms of collecting feedback. By releasing the new version to a small subset of users first, you can gather real-world data on user behavior, system performance, and potential issues. This approach allows organizations to identify and fix problems early in the process.
Blue/green deployment, on the other hand, is less feedback-focused. While the green environment can undergo extensive testing before the switch, it does not provide the same opportunity for gradual feedback from live users.
6. Complexity
Blue/green deployment is relatively straightforward in concept, involving a simple switchover from one environment to another. However, ensuring that both environments are fully synchronized, including infrastructure, configurations, and dependencies, can be a complex task. Effective orchestration and planning are essential to minimize risks.
Canary deployment introduces more operational complexity. It requires dynamic traffic management to route a portion of users or servers to the new version, as well as continuous monitoring of metrics and logs at each stage of the rollout. Ensuring a seamless transition across multiple phases requires robust tools and expertise.
Blue/green versus canary deployments: Choosing the right deployment strategy
Selecting between blue/green and canary deployment strategies depends on several factors, including your organization’s technical capabilities, risk tolerance, resource availability, and deployment objectives. Below are considerations to guide your decision:
Deployment goals:
- Blue/green deployment: Ideal for scenarios requiring zero downtime and quick rollback capabilities. This strategy works well for critical updates where a full switchover is acceptable.
- Canary deployment: Best for iterative releases, where gradual feedback and validation are needed before exposing the entire user base to the new version.
Infrastructure and resources:
- Blue/green deployment: Requires maintaining two full environments, which can be resource-intensive. Ensure sufficient infrastructure is available to support concurrent environments.
- Canary deployment: Operates within the same environment but demands advanced traffic routing and monitoring tools. Organizations with limited infrastructure budgets may prefer this option.
Risk management:
- Blue/green deployment: Offers immediate rollback to a stable environment, but all users are exposed to the new version simultaneously, increasing potential risk.
- Canary deployment: Limits exposure to a small group of users initially, significantly reducing the blast radius of potential issues.
Complexity and expertise:
- Blue/green deployment: Simpler to implement conceptually but requires precise synchronization between environments.
- Canary deployment: Involves more complexity due to the need for incremental rollout, dynamic traffic management, and real-time monitoring. Teams must have expertise in these areas.
Time-to-deploy:
- Blue/green deployment: Enables a faster transition once the new version is tested and ready.
- Canary deployment: Takes longer due to its gradual rollout, making it better suited for non-urgent updates.
Feedback and iteration:
- Blue/green deployment: Provides limited real-world feedback until after the switch. This is better suited for well-tested, low-risk updates.
- Canary deployment: Allows for collecting and acting on live user feedback at each stage, making it ideal for validating complex features.
Compatibility with databases:
- Blue/green deployment: Requires careful handling of database changes, particularly when schema updates are involved, as these need to work across both environments.
- Canary deployment: May face challenges with backward compatibility between old and new versions during the phased rollout.
Use case scenarios:
- Blue/green deployment: Suitable for organizations with automated deployment pipelines, predictable traffic patterns, and high uptime requirements.
- Canary deployment: Fits well with teams focused on user-centric development, where feedback loops and performance monitoring drive product quality.
Progressive Deployment with Octopus
You can use Octopus to deploy anything, anywhere. Whether it’s Kubernetes, Linux, or Windows virtual machines, Amazon Web Services, Azure, or Google Cloud, if Octopus can speak to it via our Tentacle agent, SSH, command line, or a web service, Octopus can deploy to it.
Octopus supports many deployment patterns, including blue/green and canary deployments.
You can model blue/green deployments in Octopus using 2 environments: One for blue and one for green. Instead of having a fixed lifecycle that deploys to these environments in separate phases, you can place both blue and green environments in the same production phase. With this configuration, you can see which software version you installed on each environment and send new versions to either the blue or green environment during a deployment.
You can create canary deployments by modeling a canary environment with a subset of infrastructure or by deploying to a “canary” target tag and pausing further rollout with a manual intervention step until you’re satisfied with the fitness of the new software version.
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