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Definition of Canary deployment

What is canary deployment?

Canary deployment involves gradually rolling out a new version of an application to a small subset of users. This allows you to observe its performance in real-time, monitor user feedback, and identify any issues before affecting your entire user base.

Why a tiny yellow bird symbolizes a test release of a new feature? The story takes us back to the dusty coal mines of the 1920s. Canaries, sensitive to even the slightest trace of toxic gas, were brought down with miners. If the air turned foul, the canary would perish first, a silent alarm that triggered immediate evacuation. Similarly, your canary users act as the early warning system in the digital minefield of software updates. You first release your new feature to this small group, and they become your intrepid explorers, navigating uncharted territory. 

What is the purpose of a canary release?

The primary purpose of a canary release is to minimize the risk of deploying a problematic update. By testing on a small group first, you can:

  • Identify major bugs and performance issues early, preventing widespread disruption.
  • Gather valuable user feedback on the new features and interface, allowing for fine-tuning before a full rollout.
  • Improve release confidence by validating the stability and compatibility of the new version.

What is the difference between blue-green vs canary vs rollout deployment?

Blue-green, canary, and rollout deployments are all techniques used to update software applications with minimal downtime and risk. But they differ in their approach:

Blue-Green: This strategy involves maintaining two identical environments, one running the current version ("blue") and the other running the new version ("green"). Traffic is then switched from blue to green at a specific time, resulting in a near-instantaneous transition. While fast and effective, blue-green deployments can be resource-intensive as you need to maintain two full environments.

Canary: This approach gradually introduces the new version to a small percentage of users, increasing traffic over time. This allows for a more controlled rollout and minimizes the risk of disruption, but it can be slower than blue-green deployments.

Rollout deployment: It involves releasing new versions in stages, but they typically follow a fixed schedule or percentage-based approach. This differs from canaries based on real-time feedback and performance metrics. Additionally, rollouts often lack the flexibility and fine-grained control offered by canaries, making them less suitable for high-risk or complex deployments.

In which scenario is it best to use canary deployment?

Canary deployments are ideal for scenarios:

  • Updating mobile apps with critical bug fixes for a large user base. Or maybe releasing new functionalities in enterprise software with minimal disruption to ongoing workflows.
  • Testing risky updates. Gradual rollout minimizes disruption and allows for quick fixes.
  • Continuous improvement. Roll out updates in steps, learn and refine before full release.
  • A/B testing variations. To find the best version without affecting all users.
  • Rollback complexity. Controlled rollouts simplify reverting to the previous version.

Not ideal for:

  • Low traffic and insufficient data from a small user subset.
  • Critical applications. Even temporary downtime for some is unacceptable.
  • Complex systems, since isolating updates in canaries can be challenging.

Key Takeaways

  • Canary deployment is the gradual rollout of new app versions to a small group ("canaries") to test performance and gather feedback before full release.
  • Why a canary? Like miners' canaries, these early users warn of potential issues before affecting everyone.
  • Compared to Blue-Green: Canary → Gradual rollouts are good for controlled tests but slower; Blue-Green → Fast switch, resource-intensive, less feedback.
  • Compared to Rollout: Canary → Adapts to real-time data, more control, riskier; Rollout → Fixed schedule, less flexible, suitable for low-risk updates.
  • Use it when: - Updating mobile apps with critical bug fixes for a large user base - Testing risky updates or have A/B testings - There is a rollback complexity - Continuous improvement

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