Canary release vs rolling deployment: Choosing a deployment strategy

Canary release

A canary release is a deployment strategy that gradually rolls out a new version of an application to a small subset of users or traffic before making it available to everyone. This approach gets its name from the historical practice of using canary birds in coal mines to detect dangerous gases. In software deployment, the “canary” version serves as an early warning system for potential issues.

The canary deployment typically starts by routing a small percentage (usually 5-10%) of traffic to the new version while the majority continues using the stable version. Teams monitor key metrics like error rates, response times, and user feedback during this phase. If the canary version performs well, traffic is gradually increased until the new version serves all users. If problems are detected, traffic can be quickly redirected back to the stable version with minimal user impact.

Rolling deployment

Rolling deployment is a strategy that gradually replaces instances of an application with new versions in a sequential manner, typically one server or container at a time. This approach ensures that the application remains available throughout the deployment process, as some instances continue serving traffic while others are being updated. It’s particularly well-suited for applications running across multiple servers or containers.

During a rolling deployment, the deployment system systematically takes servers out of the load balancer rotation, updates them with the new version, performs health checks, and then returns them to service before moving to the next instance. This process continues until all instances are running the new version. The main advantage is zero-downtime deployment, though the process can take longer than other strategies and may result in temporary inconsistencies as different versions run simultaneously.

Comparison

Rollback speed

• Canary: Instant rollback by redirecting traffic back to stable version

• Rolling: Slower rollback requiring reverse deployment process across all instances

Resource requirements

• Canary: Requires additional infrastructure to run both versions simultaneously

• Rolling: Uses existing infrastructure, updating instances in place

Risk level

• Canary: Lower risk with limited user exposure during testing phase

• Rolling: Higher risk as issues affect all users once problematic instances are deployed

Deployment duration

• Canary: Longer overall timeline due to gradual traffic increase phases

• Rolling: Moderate duration depending on number of instances and health check timing

Monitoring complexity

• Canary: Requires sophisticated traffic splitting and A/B testing capabilities

• Rolling: Simpler monitoring focused on individual instance health and overall system stability

Version consistency

• Canary: Intentionally runs mixed versions with controlled traffic distribution

• Rolling: Temporary version mixing during deployment window only

Feature flags with canary releases

Feature flags work exceptionally well with canary releases by providing an additional layer of control beyond traffic routing. Teams can deploy new code to the canary environment but keep new features disabled via feature flags, then selectively enable features for specific user segments or gradually increase the percentage of users who see new functionality. This approach allows for independent control of code deployment and feature activation, enabling more granular testing and risk management.

The combination of canary releases and feature flags also enables sophisticated testing scenarios, such as enabling new features only for internal users first, then beta users, and finally general users within the canary traffic. If issues arise, teams can quickly disable problematic features without needing to redeploy code or redirect traffic, providing multiple fallback options and faster incident response.

Feature flags with rolling deployments

Feature flags complement rolling deployments by allowing new code to be deployed across all instances while keeping new features safely disabled until the deployment is complete. This prevents users from experiencing inconsistent behavior during the deployment window when some servers might have new code while others are still running the old version. Teams can deploy with features toggled off, verify all instances are healthy and updated, then activate features uniformly across the entire system.

Additionally, feature flags provide a safety net during rolling deployments by allowing teams to quickly disable problematic features if issues are discovered after the deployment completes. Since rolling deployments take time to reverse, feature flags offer immediate remediation for feature-specific problems without requiring a full rollback of the deployment, significantly reducing the mean time to recovery for feature-related incidents.

Canary release offers excellent risk mitigation by exposing new features to only a small subset of users initially, allowing teams to monitor performance and gather feedback before full rollout. This strategy provides superior observability and the ability to quickly identify issues with minimal user impact. However, canary releases add complexity to infrastructure management, require sophisticated monitoring and traffic routing capabilities, and can slow down the overall deployment process due to the gradual rollout phases. The strategy also demands more resources as both old and new versions run simultaneously during the transition period.

Rolling deployment provides a simpler, more straightforward approach that gradually replaces instances without downtime while requiring fewer infrastructure resources than canary releases. It offers automatic rollback capabilities and works well with container orchestration platforms like Kubernetes. However, rolling deployments expose all users to potential issues simultaneously once the rollout begins, providing less granular control over risk exposure. Choose canary releases when deploying critical applications with high availability requirements, when you need detailed user feedback before full deployment, or when serving diverse user bases where gradual exposure is valuable. Opt for rolling deployments when you need faster, simpler deployments with good automated testing coverage, limited infrastructure complexity, or when working with internal applications where the blast radius of issues is more manageable.

What is a canary release deployment strategy template?

A canary release is a deployment strategy that gradually rolls out a new version of an application to a small subset of users or traffic before making it available to everyone. The strategy gets its name from the historical practice of using canary birds in coal mines to detect dangerous gases – similarly, the “canary” version serves as an early warning system for potential issues in software deployment. The deployment typically starts by routing a small percentage (usually 5-10%) of traffic to the new version while the majority continues using the stable version. Teams monitor key metrics like error rates, response times, and user feedback during this phase, gradually increasing traffic if the canary version performs well, or quickly redirecting back to the stable version if problems are detected.

How does blue-green deployment strategy work?

Blue-green deployment is a strategy that maintains two identical production environments – one called “blue” (currently live) and one called “green” (idle). When deploying a new version, the update is deployed to the idle environment while the live environment continues serving all traffic. Once the new version is fully deployed and tested in the idle environment, traffic is switched from the current live environment to the updated one, making it the new live environment. This approach provides instant rollback capabilities since the previous version remains intact in the now-idle environment, and ensures zero downtime during deployment since the switch between environments is nearly instantaneous.

What are the differences between canary deployment and blue-green deployment?

Canary deployment differs significantly from blue-green deployment in several key areas. In terms of traffic distribution, canary releases gradually split traffic between old and new versions, while blue-green switches 100% of traffic at once between environments. For rollback speed, both offer quick rollback capabilities, but canary deployments provide instant traffic redirection while blue-green offers instant environment switching. Resource requirements differ as canary deployments need infrastructure to run both versions simultaneously with traffic splitting capabilities, while blue-green requires two complete identical environments. Risk exposure varies significantly – canary deployments limit risk by exposing only a small percentage of users to new versions initially, while blue-green exposes all users simultaneously after the switch. Finally, deployment duration tends to be longer for canary releases due to gradual rollout phases, while blue-green deployments complete faster once the environment switch occurs.

How does rolling deployment compare to canary deployment?

Rolling deployment and canary deployment differ in their approach to risk management and infrastructure usage. Rolling deployment gradually replaces instances of an application with new versions sequentially, typically one server at a time, while canary deployment routes a percentage of traffic to new versions running alongside old versions. For rollback speed, canary deployments offer instant rollback by redirecting traffic, while rolling deployments require a slower reverse deployment process across all instances. Resource requirements favor rolling deployments as they use existing infrastructure and update instances in place, whereas canary deployments require additional infrastructure to run both versions simultaneously. Risk levels are lower with canary deployments due to limited user exposure during testing phases, while rolling deployments present higher risk as issues affect all users once problematic instances are deployed. Canary deployments require sophisticated traffic splitting and monitoring capabilities, while rolling deployments need simpler monitoring focused on individual instance health and overall system stability.

What are the best practices for a canary release deployment strategy?

Best practices for canary release deployment include starting with a small traffic percentage (5-10%) to minimize risk exposure and gradually increasing traffic based on performance metrics and user feedback. Implement comprehensive monitoring and alerting systems to track key metrics like error rates, response times, and user experience indicators during the canary phase. Establish clear success criteria and rollback triggers before deployment to ensure quick decision-making during the release process. Use feature flags in combination with canary releases to provide additional control layers – deploy new code to the canary environment with features disabled via flags, then selectively enable features for specific user segments. This combination allows for independent control of code deployment and feature activation, enabling more granular testing and faster incident response. Ensure sophisticated traffic routing capabilities are in place to properly distribute load between versions, and maintain the ability to quickly redirect traffic back to stable versions if issues arise. Finally, plan for longer deployment timelines due to the gradual nature of canary releases and ensure adequate infrastructure resources to support running multiple versions simultaneously.