Architure upgrade_ circuit breaking and rate limiting

Upgrade the software architecture to enhance availability and reduce risks for high-frequency API endpoints on the mini-program client:

• Implement circuit breaking and fallback strategies for APIs that invoke third-party services, ensuring graceful degradation when external dependencies fail or become unstable.
• Configure rate limiting and request throttling for high-concurrency activity interfaces—such as lucky draw and password redemption features—to prevent traffic from exceeding system capacity, thereby avoiding service overload and potential system collapse。

For circuit breaking and rate limiting strategies in software architecture, targeted testing is crucial to ensure these resilience mechanisms function correctly under stress and failure conditions. Below are the key tests that should be conducted:

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1. Circuit Breaking (熔断) Testing

Verify that the system can automatically isolate failing dependencies to prevent cascading failures.

• Trigger Condition Verification:
  • Simulate a downstream service (e.g., a third-party API) with high error rates (e.g., 50%+ HTTP 5xx errors) or high latency (e.g., response time > 2s).
  • Verify that the circuit breaker trips (opens) after the configured threshold (e.g., 5 failed requests within 10 seconds) is reached.
• Fallback Logic Validation:
  • Once the circuit is open, verify that:
    • Calls to the failing service are immediately blocked without actual network requests.
    • The predefined fallback response is returned (e.g., cached data, default values, user-friendly error messages).
    • Business logic continues to execute gracefully (e.g., showing "Service temporarily unavailable" instead of crashing).
• Recovery (Half-Open State) Testing:
  • After the configured timeout (e.g., 30 seconds), verify the circuit breaker enters the half-open state.
  • Allow a small number of test requests to pass through to the downstream service.
  • If these requests succeed, verify the circuit resets to closed; if they fail, it should return to open.
• State Transition Monitoring:
  • Verify that circuit breaker state changes (Closed → Open → Half-Open → Closed) are logged and exposed via metrics (e.g., Prometheus) for monitoring and alerting.

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2. Rate Limiting (限流) Testing

Ensure the system can protect itself from traffic overload by enforcing request quotas.

• Threshold Accuracy:
  • Configure a rate limit (e.g., 100 requests per minute per user/IP).
  • Send requests at a rate just below, at, and above the threshold.
  • Verify that requests are allowed below/at the limit and rejected above it.
• Rejection Behavior:
  • Verify that rejected requests return the correct HTTP status code (e.g., 429 Too Many Requests).
  • Check that the response includes standard rate-limiting headers (e.g., Retry-After, X-RateLimit-Limit, X-RateLimit-Remaining).
• Algorithm Validation:
  • Token Bucket / Leaky Bucket: Test burst traffic handling. Verify that a burst of requests within the bucket capacity is allowed, but sustained overflow is throttled.
  • Fixed Window / Sliding Window: Test for "thundering herd" issues at window boundaries and ensure smooth rate control.
• Scope and Granularity:
  • Test rate limiting at different levels: per IP, per user ID, per API endpoint, globally.
  • Verify that limits are enforced correctly across distributed instances (requires shared state, e.g., Redis).
• Performance Under Load:
  • Simulate high traffic (above limit) and verify that:
    • The rate limiting mechanism itself does not become a performance bottleneck.
    • System resources (CPU, memory) remain stable.
    • Non-limited APIs continue to function normally.

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3. Combined & Integration Testing

Test how circuit breaking and rate limiting interact with the overall system.

• Downstream Failure + Rate Limiting:
  • Simulate a slow or failing third-party service while simultaneously generating high client traffic.
  • Verify that the circuit breaker opens and rate limiting prevents the internal system from being overwhelmed by retries.
• Dependency on Rate-Limited Third Parties:
  • If a third-party API has its own rate limits, simulate hitting that limit.
  • Verify your system’s circuit breaker trips appropriately and uses fallbacks instead of continuously failing.
• Configuration Hot Reload:
  • Change rate limit or circuit breaker thresholds dynamically (without restart).
  • Verify the new rules take effect immediately.

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4. Observability & Alerting Validation

Ensure the system is observable when these mechanisms are active.

• Metrics Exposure:
  • Verify metrics such as circuit_breaker_open_count, rate_limit_rejected_requests_total, and request_duration are exposed (e.g., via Prometheus).
• Logging:
  • Verify that circuit breaker state changes and rate limit rejections are logged with sufficient context (e.g., user ID, endpoint, timestamp).
• Alerting:
  • Set up alerts for:
    • Circuit breaker entering OPEN state.
    • High rate of rate limit rejections.
    • Sustained high error rates that may trigger circuit breaking.

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Summary

Testing circuit breaking and rate limiting is essential for building a resilient system. Focus on correctness of logic, proper fallback behavior, performance under stress, and observability. Use tools like Chaos Engineering (e.g., Chaos Monkey), load testing tools (e.g., JMeter, k6), and monitoring platforms (e.g., Grafana, ELK) to validate these strategies effectively in staging or canary environments before production rollout.