Canary release
Sending a new version to a small share of traffic first, watching error rates and latency, and widening the rollout only if it holds.
Named after the canaries miners carried to detect gas. Unlike blue-green, which switches everyone at once, a canary limits the blast radius of subtle problems that only show up under real traffic. It needs metrics good enough to compare the canary with the old version, ideally against an SLO, and an automatic rollback when they diverge.
Related terms
- Blue-green deployment: Two identical production environments: the new version goes to the idle one, then traffic switches over, and back if something breaks.
- Feature flags: Switches in code that turn a feature on or off for some or all users without a new deploy.
- SLO and SLI: An SLI is a measured indicator of service quality; an SLO is the internal target for it, stricter than any SLA you sign.
- Blast radius: How much of a system, and how many customers, a single failure, bad deploy or leaked key can affect.
