resilience-circuit-breaker-designer

Purpose

Protect applications from cascading failures when downstream dependencies (third-party APIs, microservices, databases) become slow or unresponsive, using Circuit Breakers, Bulkheads, Timeouts, and Graceful Fallbacks.

When to Use

• Calling third-party APIs (Stripe, Twilio, OpenAI, shipment tracking) that occasionally degrade.
• Preventing thread/connection exhaustion when one downstream microservice stalls.
• Implementing graceful degradation (e.g. returning cached recommendations when AI engine is down).

What to Analyze

1. Circuit States: CLOSED (normal), OPEN (failing fast without calling downstream), HALF-OPEN (probing recovery).
2. Threshold Metrics: Failure percentage threshold (e.g. >50% errors over 20 requests) and slow call duration threshold.
3. Timeout Strategy: Strict, aggressive timeouts (e.g. 500ms) to prevent socket pooling exhaustion.
4. Bulkhead Isolation: Limiting concurrent outbound calls to a single service (e.g. max 20 concurrent threads for payment gateway).
5. Fallback Plan: Returning cached data, static default payloads, or queued background retries.

Output Format

• Resilience Blueprint Table: [Dependency | Timeout | Circuit Trigger | Bulkhead Cap | Fallback Action].
• Code Implementation: Production-ready wrapper using Opossum (Node.js), Resilience4j (Java), or go-resiliency (Go).
• Health Metrics & Alerting: Prometheus metrics emitted on circuit state changes.

Avoid

• Omitting strict timeouts (a hanging connection is worse than a fast failure).
• Setting reset timeout too low, causing thrashing between OPEN and HALF-OPEN states.