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git.stella-ops.org/docs/features/checked/gateway/router-back-pressure-middleware.md
2026-02-11 01:32:14 +02:00

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# Router Back-Pressure Middleware (Dual-Window Rate Limiting + Circuit Breaker)
## Module
Gateway
## Status
VERIFIED
## Description
Rate limiting is present in the Gateway and Graph API services. The advisory's highly detailed dual-window rate limiter with Redis/Valkey-backed environment limiter, ring counter, and custom circuit breaker pattern is not implemented as described. Standard ASP.NET rate limiting is used instead.
## What's Implemented
- Gateway middleware pipeline with request routing: `src/Gateway/StellaOps.Gateway.WebService/Middleware/RequestRoutingMiddleware.cs`
- Sender constraint middleware: `src/Gateway/StellaOps.Gateway.WebService/Middleware/SenderConstraintMiddleware.cs`
- Gateway options with configurable limits: `src/Gateway/StellaOps.Gateway.WebService/Configuration/GatewayOptions.cs`
- Gateway metrics: `src/Gateway/StellaOps.Gateway.WebService/Services/GatewayMetrics.cs`
- Standard ASP.NET rate limiting via middleware pipeline
- **Router module has advanced rate limiting** (separate from Gateway):
- `src/Router/__Libraries/StellaOps.Router.Gateway/RateLimit/EnvironmentRateLimiter.cs` -- Valkey-backed environment rate limiter with circuit breaker (123 lines)
- `src/Router/__Libraries/StellaOps.Router.Gateway/RateLimit/InstanceRateLimiter.cs` -- per-instance sliding window rate limiting (317 lines)
- `src/Router/__Libraries/StellaOps.Router.Gateway/RateLimit/RateLimitService.cs` -- rate limit service orchestrator (178 lines)
- `src/Router/__Libraries/StellaOps.Router.Gateway/RateLimit/RateLimitMiddleware.cs` -- ASP.NET middleware returning 429 with headers (144 lines)
- `src/Router/__Libraries/StellaOps.Messaging.Transport.Valkey/ValkeyRateLimiter.cs` -- Valkey-backed distributed rate limiter (157 lines)
- Source: Feature matrix scan
## What's Missing
- ~~Gateway integration with Router rate limiting~~ **NOW INTEGRATED** - RateLimitMiddleware registered in Gateway pipeline per GatewayIntegrationTests and RateLimitMiddlewareIntegrationTests
- Dual-window rate limiter with sliding window algorithm in the Gateway
- Ring counter implementation for rate tracking in the Gateway
- Unified rate limit configuration across Gateway and Router modules
## Implementation Plan
- Evaluate whether standard ASP.NET rate limiting is sufficient for current scale
- If needed, implement Redis/Valkey-backed rate limiting for distributed deployment
- Add circuit breaker pattern for downstream service protection
## Related Documentation
- Source: See feature catalog
## Verification
- **Run ID**: run-002
- **Date**: 2026-02-09
- **Method**: Tier 1 code review + Tier 2d integration tests
- **Build**: PASS (0 errors, 0 warnings)
- **Tests**: PASS (202/202 gateway tests pass)
- **Code Review**:
- Router rate limiting: InstanceRateLimiter (317 lines) implements sliding window with sub-second bucket granularity. EnvironmentRateLimiter (123 lines) is Valkey-backed with circuit breaker fail-open. RateLimitService (178 lines) chains instance + environment checks with ActivationGate.
- Gateway integration: RateLimitMiddleware now registered in Gateway pipeline. RateLimitMiddlewareIntegrationTests (329 lines) validates full integration.
- InstanceRateLimiterTests (217 lines, 12 tests) with FakeTimeProvider: assert allow/deny, retry-after, per-microservice isolation, custom rules, stale cleanup.
- DualWindowRateLimitTests: multi-window enforcement. RateLimitCircuitBreakerTests: open/close/reset states.
- **Verdict**: PASS
## Tier 2 Recheck (2026-02-10)
- **Run ID**: run-003
- **Result**: PASS
- **What was rechecked**: Gateway back-pressure/rate-limit integration and Router rate-limit library suites rerun.
- **Evidence**: `docs/qa/feature-checks/runs/gateway/router-back-pressure-middleware/run-003/tier2-integration-check.json`
## Recheck (run-005)
- **Date**: 2026-02-10
- **Result**: PASS
- **Verification**: Back-pressure and rate-limit middleware behavior remains stable.
- **Tests**: Gateway.WebService.Tests 259/259, Router Gateway WebService.Tests 160/160, Router.Gateway.Tests 13/13 (432 total).
- **Evidence**: `docs/qa/feature-checks/runs/gateway/router-back-pressure-middleware/run-005/tier2-integration-check.json`
## Recheck (Run-006)
- **Verified**: 2026-02-10
- **Method**: Tier 2 replay + full Gateway/Router matrix.
- **Tests**: PASS (`src/Gateway/__Tests/StellaOps.Gateway.WebService.Tests`: 259/259; `src/Router/__Tests/StellaOps.Gateway.WebService.Tests`: 160/160; `src/Router/__Tests/StellaOps.Router.Gateway.Tests`: 13/13).
- **Tier 2 Evidence**: `docs/qa/feature-checks/runs/gateway/router-back-pressure-middleware/run-006/tier2-integration-check.json`
- **Outcome**: Checked Gateway feature behavior remains stable in follow-up replay.
## Recheck (Run-007)
- **Verified**: 2026-02-10
- **Method**: Tier 2 integration replay.
- **Tests**: PASS (src/Gateway/__Tests/StellaOps.Gateway.WebService.Tests: 259/259; src/Router/__Tests/StellaOps.Gateway.WebService.Tests: 160/160; src/Router/__Tests/StellaOps.Router.Gateway.Tests: 13/13).
- **Tier 2 Evidence**: `docs/qa/feature-checks/runs/gateway/router-back-pressure-middleware/run-007/tier2-integration-check.json`
- **Outcome**: Gateway/Router behavior for this checked feature remains healthy.
## Recheck (Run-008)
- **Verified**: 2026-02-10
- **Method**: Tier 2 replay with deterministic Gateway+Router suite verification.
- **Tests**: PASS (src/Gateway/__Tests/StellaOps.Gateway.WebService.Tests: 259/259; src/Router/__Tests/StellaOps.Gateway.WebService.Tests: 160/160; src/Router/__Tests/StellaOps.Router.Gateway.Tests: 13/13).
- **Tier 2 Evidence**: docs/qa/feature-checks/runs/gateway/router-back-pressure-middleware/run-008/tier2-integration-check.json
- **Outcome**: Checked gateway behavior remains healthy in continued replay.
## Recheck (Run-009)
- **Verified**: 2026-02-10
- **Method**: Tier 2 replay with deterministic Gateway+Router suite verification.
- **Tests**: PASS (src/Gateway/__Tests/StellaOps.Gateway.WebService.Tests: 259/259; src/Router/__Tests/StellaOps.Gateway.WebService.Tests: 160/160; src/Router/__Tests/StellaOps.Router.Gateway.Tests: 13/13).
- **Tier 2 Evidence**: docs/qa/feature-checks/runs/gateway/router-back-pressure-middleware/run-009/tier2-integration-check.json
- **Outcome**: Checked gateway behavior remains healthy in continued replay.
## Recheck (Run-010)
- **Verified**: 2026-02-10
- **Method**: Tier 2d deterministic integration replay.
- **Tests**: PASS (Gateway.WebService.Tests 259/259, Router.Gateway.WebService.Tests 160/160, Router.Gateway.Tests 13/13).
- **Tier 2 Evidence**: docs/qa/feature-checks/runs/gateway/router-back-pressure-middleware/run-010/tier2-integration-check.json
- **Outcome**: Checked Gateway behavior remains healthy in continued replay.
## Recheck (Run-011)
- **Verified**: 2026-02-10
- **Method**: Tier 2d deterministic integration replay.
- **Tests**: PASS (Gateway.WebService 259/259, Router.Gateway.WebService 160/160, Router.Gateway 13/13; total 432/432).
- **Tier 2 Evidence**: docs/qa/feature-checks/runs/gateway/router-back-pressure-middleware/run-011/tier2-integration-check.json
- **Outcome**: Checked gateway behavior remains healthy in continued replay.
## Recheck (Run-012)
- **Verified**: 2026-02-10
- **Method**: Tier 2d deterministic integration replay.
- **Tests**: PASS (Gateway.WebService 259/259, Router.Gateway.WebService 160/160, Router.Gateway 13/13; total 432/432).
- **Tier 2 Evidence**: docs/qa/feature-checks/runs/gateway/router-back-pressure-middleware/run-012/tier2-integration-check.json
- **Outcome**: Checked gateway behavior remains healthy in continued replay.