Scenario Composer

Overview

Design reproducible scenarios that test one clear system behavior at a time. Package each scenario with deterministic timing, explicit hypotheses, and measurable success criteria.

Workflow

1. Define experiment intent

• Write one hypothesis in observable terms.
• Choose the primary target metric (p99 latency, error rate, recovery time, or cost).

2. Freeze deterministic controls

• Set seed, simulationDuration, and warmupDuration.
• Avoid changing more than one major variable per scenario version.

3. Compose traffic profile

• Select one workload pattern and justify it (constant, poisson, spike, diurnal, bursty, sawtooth, replay).
• Define request mix and base load.
• For scale tests, define the step-up schedule and stop condition.

4. Compose failure and resilience conditions

• Inject the minimum fault set needed to test the hypothesis.
• Specify timing mode (deterministic, probabilistic, conditional) and fault duration.
• Include resilience controls relevant to the scenario (retry, breaker, bulkhead, rate limit).

5. Define checks and expected outcomes

• Add invariants and SLO checks that can fail the run.
• Record expected qualitative behavior (for example, queue growth at gateway before API timeout cascade).

6. Deliver scenario package

• Provide scenario name and intent, topology deltas (or full config), workload config, fault list, invariants, and pass/fail rubric.

Scenario quality rules

• Keep each scenario focused on one dominant failure pattern.
• Separate baseline and stressed variants.
• Reuse seeds when comparing design alternatives.
• Prefer deterministic schedules for regression suites.

References

• Read references/scenario-patterns.md for templates, built-in mappings, and anti-pattern guardrails.
• Use these repo sources:
• canonical-catalogue/DSDS Canonical Catalogue - scenarios to ship.csv
• canonical-catalogue/DSDS Canonical Catalogue - Failure modes & propagation semantics.csv
• canonical-catalogue/DSDS Canonical Catalogue - Patterns for scenario generation.csv
• planning/IMPLEMENTATION_PLAN.md (Phase 7)