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Summary of ChangesHello @slin1237, I'm Gemini Code Assist1! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed! This pull request focuses on enhancing the performance and reducing the CPU overhead of the Highlights
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This pull request significantly refactors the circuit breaker implementation to improve performance by replacing Arc<RwLock<...>> with lock-free atomic operations (AtomicU8, AtomicU32, AtomicU64) for state management and time tracking. This change affects how the circuit breaker's state, last failure time, and last state change time are stored and accessed, making hot paths more efficient through atomic loads, stores, and compare-and-swap operations. Additionally, the pull request introduces extensive optimizations for metric recording across the codebase. This includes new utility functions like bool_to_static_str, status_code_to_static_str, method_to_static_str, and status_code_to_cow to convert frequently used string labels (e.g., HTTP methods, status codes, boolean flags) into static string references or Cow types, thereby reducing heap allocations during metric collection. These metric-related changes are applied to HTTP request/response recording, router requests, upstream responses, and worker retry backoff metrics, ensuring that common label values avoid dynamic string allocations.
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The get_model! macro was ineffective as both branches performed clone(). Simplify to straightforward clones where needed, with a move on final use. This addresses code review feedback about confusing dead code. Optimize HTTP metrics with static strings Reduce allocations in hot paths by using static strings: - Add method_to_static_str() for HTTP methods (GET, POST, etc.) - Update record_http_request/record_http_duration to use &'static str - Optimize record_router_upstream_response with status_code_to_cow - Optimize record_worker_retry_backoff for common attempt values (1-5) - Update HttpMetricsMiddleware to use static method strings This eliminates string allocations on every HTTP request for method and status_class labels. Replace CircuitBreaker RwLock with lock-free atomics Convert CircuitBreaker to use atomic operations instead of RwLock for significantly reduced contention under high concurrency: - Replace Arc<RwLock<CircuitState>> with AtomicU8 - Replace Arc<RwLock<Instant>> with AtomicU64 (ms timestamps) - Use compare-and-swap for state transitions - Hot path (can_execute/state) is now fully lock-free Also update CPU_OVERHEAD_ANALYSIS.md with high-concurrency analysis documenting lock contention issues in metrics, TokenBucket, and WorkerRegistry. Estimated improvement: 20-30ms latency reduction under high concurrency. Reduce CPU overhead in metrics system Key optimizations: - Add bool_to_static_str() for zero-cost bool-to-string conversion - Add status_code_to_static_str() lookup table for common HTTP codes - Change record_router_request() streaming param from bool to &'static str - Optimize record_streaming_metrics() to minimize string clones - Update all router call sites to use static strings This eliminates allocations for the streaming label (was bool.to_string()) and reduces allocations in record_streaming_metrics from 5 clones to max 3. Common HTTP status codes (200, 400, 500, etc.) now use static strings. Add CPU overhead analysis for gateway 0.2.3 vs 0.2.4 Detailed analysis comparing metrics, middleware, and other changes between gateway versions. Key findings: - String allocations in metrics (HIGH impact): Every metric call with model_id allocates via .to_string() - High label cardinality (MEDIUM): 5-6 labels per router metric - New HTTP metrics layer (MEDIUM): Additional per-request processing - OTEL tracing (MEDIUM when enabled): Trace context propagation - WASM plugin support (LOW): Only when plugins loaded Includes recommendations for addressing overhead issues.
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