feat: 初始化零工后端代码

gig-poc/apps/api/app/services/ai_guard.py

@@ -0,0 +1,87 @@
+from __future__ import annotations
+
+import time
+from dataclasses import dataclass
+from threading import Lock
+
+from app.core.config import Settings
+
+
+@dataclass
+class EndpointState:
+    current_minute: int = 0
+    minute_count: int = 0
+    consecutive_failures: int = 0
+    circuit_open_until: float = 0.0
+
+
+class AIGuard:
+    _lock = Lock()
+    _endpoint_states: dict[str, EndpointState] = {}
+    _metrics = {
+        "requests_total": 0,
+        "success_total": 0,
+        "fail_total": 0,
+        "fallback_total": 0,
+        "rate_limited_total": 0,
+        "circuit_open_total": 0,
+        "endpoint_failover_total": 0,
+    }
+
+    def __init__(self, settings: Settings):
+        self.settings = settings
+
+    def allow_request(self, endpoint: str) -> tuple[bool, str]:
+        now = time.time()
+        now_minute = int(now // 60)
+        with self._lock:
+            state = self._endpoint_states.setdefault(endpoint, EndpointState())
+            if state.circuit_open_until > now:
+                self._metrics["circuit_open_total"] += 1
+                return False, "circuit_open"
+            if state.current_minute != now_minute:
+                state.current_minute = now_minute
+                state.minute_count = 0
+            if state.minute_count >= self.settings.ai_rate_limit_per_minute:
+                self._metrics["rate_limited_total"] += 1
+                return False, "rate_limited"
+            state.minute_count += 1
+            self._metrics["requests_total"] += 1
+        return True, "ok"
+
+    def record_success(self, endpoint: str) -> None:
+        with self._lock:
+            state = self._endpoint_states.setdefault(endpoint, EndpointState())
+            state.consecutive_failures = 0
+            state.circuit_open_until = 0.0
+            self._metrics["success_total"] += 1
+
+    def record_failure(self, endpoint: str) -> None:
+        with self._lock:
+            state = self._endpoint_states.setdefault(endpoint, EndpointState())
+            state.consecutive_failures += 1
+            self._metrics["fail_total"] += 1
+            if state.consecutive_failures >= self.settings.ai_circuit_breaker_fail_threshold:
+                state.circuit_open_until = time.time() + self.settings.ai_circuit_breaker_cooldown_seconds
+                state.consecutive_failures = 0
+
+    def record_fallback(self) -> None:
+        with self._lock:
+            self._metrics["fallback_total"] += 1
+
+    def record_failover(self) -> None:
+        with self._lock:
+            self._metrics["endpoint_failover_total"] += 1
+
+    def snapshot(self) -> dict:
+        with self._lock:
+            requests_total = self._metrics["requests_total"]
+            fallback_total = self._metrics["fallback_total"]
+            success_total = self._metrics["success_total"]
+            fail_total = self._metrics["fail_total"]
+            return {
+                **self._metrics,
+                "fallback_hit_rate": round(fallback_total / requests_total, 4) if requests_total else 0.0,
+                "success_rate": round(success_total / requests_total, 4) if requests_total else 0.0,
+                "failure_rate": round(fail_total / requests_total, 4) if requests_total else 0.0,
+            }