Canary release vs progressive delivery: Choosing a deployment strategy

May 18, 2024

Article by Michael Ferranti

Canary release deployment strategy

Canary releasing is a deployment strategy where a new version of an application is rolled out to a small subset of users or servers before being made available to the entire infrastructure. This approach allows teams to test the new version in a production environment with real users while limiting potential negative impacts. By monitoring the performance and behavior of the canary version, teams can detect issues early and decide whether to proceed with a full rollout or roll back to the previous version.

The key advantage of canary releases is risk mitigation. By exposing only a small percentage of traffic to the new version initially, organizations can gain confidence in the release while protecting the majority of users from potential bugs or performance issues. This approach is particularly valuable for high-traffic systems where downtime or errors could have significant business impact. Canary releases require robust monitoring and the ability to quickly route traffic between different versions of the application.

Progressive delivery deployment strategy

Progressive delivery extends the concept of canary releases by providing a more structured framework for gradually exposing new functionality to users. It encompasses various techniques such as canary releases, feature flags, A/B testing, and blue-green deployments, all aimed at reducing deployment risk. Progressive delivery emphasizes the continuous and incremental nature of modern software delivery, where features are incrementally rolled out to users based on data and feedback.

What sets progressive delivery apart is its focus on user-centric metrics and the ability to make data-driven decisions about each phase of the rollout. Teams define success criteria for each stage of the deployment and only proceed when those criteria are met. This approach allows for more granular control over how and when users experience new features, enabling organizations to align technical releases with business goals and user needs.

Comparing canary releases and progressive delivery

Scope

Canary Release: Focuses specifically on the mechanism of limited deployment to a subset of users or infrastructure.

Progressive Delivery: Encompasses a broader set of practices including canary releases, feature flags, and A/B testing.

Control granularity

Canary Release: Typically controls exposure at the deployment or server level.

Progressive Delivery: Offers finer-grained control down to the feature or user segment level.

Decision criteria

Canary Release: Usually based on technical metrics like error rates and performance.

Progressive Delivery: Incorporates both technical metrics and business KPIs to guide rollout decisions.

Tooling requirements

Canary Release: Requires traffic routing capabilities and monitoring systems.

Progressive Delivery: Requires more sophisticated tooling including feature flag management and experimentation platforms.

Release reversibility

Canary Release: Rollbacks typically involve reverting to the previous deployment.

Progressive Delivery: Can selectively enable or disable features without full deployment rollbacks.

User segmentation

Canary Release: Often uses random selection or simple infrastructure-based segmentation.

Progressive Delivery: Enables targeted releases to specific user segments based on various attributes.

Feature flags with canary releases

In a canary release strategy, feature flags serve as a safety mechanism to control the exposure of new functionality within the limited canary deployment. Teams can deploy code to the canary servers with features turned off by default, then selectively enable them for specific users or scenarios once the basic deployment proves stable. This creates a two-layered approach to risk mitigation: first by limiting the server deployment scope, and then by controlling feature activation within that deployment.

Feature flags also enhance the flexibility of canary testing by allowing teams to test multiple features independently within the same canary deployment. For example, a team might enable feature A for all users in the canary group while enabling feature B for only 50% of those users. This approach provides more nuanced testing capabilities and allows teams to gather more specific feedback on individual components rather than evaluating the entire release as a monolithic unit.

Feature flags with progressive delivery

Feature flags are a cornerstone technology of progressive delivery, providing the fine-grained control needed to orchestrate sophisticated rollout strategies. In progressive delivery, feature flags control not just whether a feature is on or off, but also who sees it, under what conditions, and for how long. This enables teams to create sophisticated rollout plans where features can be progressively enabled for increasingly larger or more diverse user segments based on real-time feedback and performance data.

The integration of feature flags with progressive delivery also facilitates experimentation and data-driven decision making. Teams can use feature flags to run A/B tests or multivariate experiments to compare different implementations or experiences, collecting data on user behavior and business metrics. These insights then inform decisions about how to proceed with the rollout, allowing teams to optimize features before full release or even abandon features that don’t deliver the expected value—all without the risk and overhead of full deployment rollbacks.

Canary releases and progressive delivery are both strategies designed to mitigate risks when deploying software changes. Canary releases involve initially deploying changes to a small subset of users or servers before gradually expanding the rollout. This approach allows teams to monitor the performance and stability of new features in a controlled environment, catching potential issues before they affect the entire user base. The primary advantages include early detection of bugs, reduced blast radius for failures, and the ability to gather real user feedback. However, canary releases typically lack sophisticated targeting mechanisms, making it difficult to direct changes to specific user segments, and they often require manual intervention to progress through deployment stages.

Progressive delivery builds upon canary releases by adding more advanced capabilities, such as feature flags, sophisticated traffic management, and automated rollback mechanisms. This approach provides finer-grained control over who receives what features and when, enabling targeted releases to specific user demographics or regions. Progressive delivery excels when you need complex deployment patterns with precise user targeting, automated decision-making based on metrics, or when working with microservices architectures that benefit from granular control. Choose canary releases when your infrastructure is simpler, you have a monolithic application, or when your team is just beginning to implement safer deployment practices. Progressive delivery is better suited for organizations with mature DevOps practices, complex applications that require careful feature rollouts, or when you need to maintain multiple variations of features simultaneously for different user segments.

Frequently asked questions

What is a canary release deployment strategy?

What are the advantages of canary releases?

What is progressive delivery?

Progressive delivery extends the concept of canary releases by providing a more structured framework for gradually exposing new functionality to users. It encompasses various techniques such as canary releases, feature flags, A/B testing, and blue-green deployments, all aimed at reducing deployment risk. It emphasizes continuous and incremental software delivery, where features are rolled out to users based on data and feedback.

How do canary releases and progressive delivery differ?

Canary releases focus specifically on limited deployment to a subset of users or infrastructure, while progressive delivery encompasses a broader set of practices. Canary releases typically control exposure at the deployment level and use technical metrics for decision-making, while progressive delivery offers finer-grained control down to the feature level and incorporates both technical metrics and business KPIs to guide rollout decisions.

How are feature flags used with canary releases?

In a canary release strategy, feature flags serve as a safety mechanism to control the exposure of new functionality within the limited canary deployment. Teams can deploy code to the canary servers with features turned off by default, then selectively enable them for specific users or scenarios once the basic deployment proves stable. This creates a two-layered approach to risk mitigation and allows teams to test multiple features independently within the same canary deployment.

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