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CONCEPT Cited by 1 source

Progressive scope expansion

Definition

Progressive scope expansion is the practice of starting a fault-injection experiment with a minimal fraction of affected resources (typically 1%) and incrementally increasing scope (e.g., 1% → 5% → 10% → 25%) only after validating that the system tolerates the previous level without breaching health thresholds.

Rationale

The pattern applies the same principle as canary deployments to chaos engineering: limit blast radius by proving safety at each increment before expanding. This makes resilience testing safe enough for production environments and lowers the barrier to adoption for teams without specialized chaos-engineering expertise.

Safety mechanisms

  • Stop conditions: automated alarms (e.g., CloudWatch) that halt experiments before SLA violation. Recommended margin: 10× below SLA (trigger at 0.1% error rate when SLA allows 1%).
  • Scope gating: each expansion step requires the previous step to complete without triggering stop conditions.
  • Time-bounded: experiments have maximum durations to prevent indefinite fault injection.

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