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gateway/pool.py

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+"""Worker 健康池 + 空闲派发。
+
+- 后台 asyncio 任务周期性探测每个 worker 的 /health
+- 连续失败 N 次 → 下线；连续成功 N 次 → 上线
+- 每个 worker 一个 busy 标志（per_worker_concurrency=1）
+- acquire_worker() 从在线池挑空闲 worker；全忙排队；池空→NoWorkerAvailable
+- release_worker() 释放 worker
+"""
+
+import asyncio
+import logging
+import time
+from dataclasses import dataclass, field
+from typing import Dict, List, Optional
+
+import httpx
+
+logger = logging.getLogger("gateway.pool")
+
+
+# ---------------------------------------------------------------------------
+# 异常
+# ---------------------------------------------------------------------------
+
+class NoWorkerAvailable(Exception):
+    """无可用 worker（池空或全忙排队超时）。"""
+    pass
+
+
+# ---------------------------------------------------------------------------
+# 数据结构
+# ---------------------------------------------------------------------------
+
+@dataclass
+class WorkerState:
+    """单个 worker 的运行时状态。"""
+    url: str
+    online: bool = False  # 初始 offline，等健康检查通过后上线
+    busy: bool = False
+    consecutive_failures: int = 0
+    consecutive_successes: int = 0
+
+
+# ---------------------------------------------------------------------------
+# 全局状态
+# ---------------------------------------------------------------------------
+
+_workers: Dict[str, WorkerState] = {}
+_pool_condition: Optional[asyncio.Condition] = None
+_health_task: Optional[asyncio.Task] = None
+_shutdown_event: Optional[asyncio.Event] = None
+
+
+# ---------------------------------------------------------------------------
+# 健康检查后台任务
+# ---------------------------------------------------------------------------
+
+async def _check_worker_health(
+    client: httpx.AsyncClient,
+    w: WorkerState,
+    cfg: dict,
+) -> None:
+    """探测单个 worker 的 /health，更新上下线状态。"""
+    hc_cfg = cfg["health_check"]
+    url = f"{w.url}{hc_cfg['path']}"
+    token = cfg["shared_password"]
+
+    try:
+        resp = await client.get(
+            url,
+            headers={"X-Internal-Token": token},
+            timeout=hc_cfg["timeout_seconds"],
+        )
+        if resp.status_code == 200:
+            w.consecutive_failures = 0
+            w.consecutive_successes += 1
+            if w.consecutive_successes >= hc_cfg["healthy_threshold"]:
+                if not w.online:
+                    w.online = True
+                    logger.info("Worker 上线: %s（连续成功 %d 次）", w.url, w.consecutive_successes)
+        else:
+            _mark_failure(w, f"HTTP {resp.status_code}")
+    except Exception as exc:
+        _mark_failure(w, str(exc))
+
+
+def _mark_failure(w: WorkerState, reason: str) -> None:
+    """记录一次失败，达到阈值后下线。"""
+    w.consecutive_successes = 0
+    w.consecutive_failures += 1
+    threshold = w.consecutive_failures  # used in log
+    hc_threshold = 2  # default, will be overridden
+    if w.consecutive_failures >= hc_threshold:
+        # 实际 threshold 从配置读取，这里先做基本判断
+        pass
+    logger.debug("Worker %s 健康检查失败 (%d/%d): %s", w.url, w.consecutive_failures, 99, reason)
+
+
+async def _health_check_loop(cfg: dict) -> None:
+    """后台循环：周期性探测所有 worker 健康状态。"""
+    hc_cfg = cfg["health_check"]
+    interval = hc_cfg["interval_seconds"]
+    unhealthy_threshold = hc_cfg["unhealthy_threshold"]
+    healthy_threshold = hc_cfg["healthy_threshold"]
+    token = cfg["shared_password"]
+
+    logger.info(
+        "健康检查循环启动 | 间隔=%ds | 下线阈值=%d | 上线阈值=%d | workers=%d",
+        interval, unhealthy_threshold, healthy_threshold, len(_workers),
+    )
+
+    async with httpx.AsyncClient() as client:
+        while not _shutdown_event.is_set():
+            for w in _workers.values():
+                url = f"{w.url}{hc_cfg['path']}"
+                try:
+                    resp = await client.get(
+                        url,
+                        headers={"X-Internal-Token": token},
+                        timeout=hc_cfg["timeout_seconds"],
+                    )
+                    if resp.status_code == 200:
+                        w.consecutive_failures = 0
+                        w.consecutive_successes += 1
+                        if w.consecutive_successes >= healthy_threshold and not w.online:
+                            w.online = True
+                            logger.info("✅ Worker 上线: %s", w.url)
+                    else:
+                        w.consecutive_successes = 0
+                        w.consecutive_failures += 1
+                        if w.consecutive_failures >= unhealthy_threshold and w.online:
+                            w.online = False
+                            logger.warning("⚠ Worker 下线: %s（HTTP %d，连续失败 %d 次）",
+                                           w.url, resp.status_code, w.consecutive_failures)
+                except Exception as exc:
+                    w.consecutive_successes = 0
+                    w.consecutive_failures += 1
+                    if w.consecutive_failures >= unhealthy_threshold and w.online:
+                        w.online = False
+                        logger.warning("⚠ Worker 下线: %s（%s，连续失败 %d 次）",
+                                       w.url, exc, w.consecutive_failures)
+
+            # 等待下一次探测（支持快速关闭）
+            try:
+                await asyncio.wait_for(_shutdown_event.wait(), timeout=interval)
+                break  # shutdown signaled
+            except asyncio.TimeoutError:
+                pass  # 正常的 interval 到期
+
+    logger.info("健康检查循环已停止")
+
+
+# ---------------------------------------------------------------------------
+# 初始化 / 关闭
+# ---------------------------------------------------------------------------
+
+async def init_pool(cfg: dict) -> None:
+    """初始化 worker 池并启动健康检查后台任务。"""
+    global _workers, _pool_condition, _health_task, _shutdown_event
+
+    _workers = {url: WorkerState(url=url) for url in cfg["workers"]}
+    _pool_condition = asyncio.Condition()
+    _shutdown_event = asyncio.Event()
+
+    # 立即做一轮健康检查以快速上线
+    hc_cfg = cfg["health_check"]
+    token = cfg["shared_password"]
+    async with httpx.AsyncClient() as client:
+        for w in _workers.values():
+            try:
+                resp = await client.get(
+                    f"{w.url}{hc_cfg['path']}",
+                    headers={"X-Internal-Token": token},
+                    timeout=hc_cfg["timeout_seconds"],
+                )
+                if resp.status_code == 200:
+                    w.consecutive_successes = 1
+                    if hc_cfg["healthy_threshold"] <= 1:
+                        w.online = True
+                else:
+                    w.consecutive_failures = 1
+            except Exception:
+                w.consecutive_failures = 1
+
+    # 对于 healthy_threshold == 1 的情况，已在上面的检查中上线
+    # 标记初始在线状态
+    online_count = sum(1 for w in _workers.values() if w.online)
+    logger.info("Worker 池初始化完成 | 总数=%d | 在线=%d", len(_workers), online_count)
+
+    # 启动后台健康检查
+    _health_task = asyncio.create_task(_health_check_loop(cfg))
+
+
+async def shutdown_pool() -> None:
+    """关闭健康检查任务，释放资源。"""
+    global _shutdown_event, _health_task
+    if _shutdown_event:
+        _shutdown_event.set()
+    if _health_task:
+        _health_task.cancel()
+        try:
+            await _health_task
+        except asyncio.CancelledError:
+            pass
+        _health_task = None
+    logger.info("Worker 池已关闭")
+
+
+# ---------------------------------------------------------------------------
+# 派发
+# ---------------------------------------------------------------------------
+
+async def mark_worker_unhealthy(w: WorkerState) -> None:
+    """被动标记：转发失败时立即将该 worker 下线。"""
+    async with _pool_condition:
+        if w.online:
+            w.online = False
+            w.consecutive_failures += 1
+            logger.warning("⚠ Worker 被动下线: %s（转发失败）", w.url)
+
+
+async def acquire_worker(cfg: dict) -> WorkerState:
+    """从在线池中获取一个空闲 worker。
+
+    全忙则排队等待，最多 queue_wait_seconds；池空立即抛异常。
+    """
+    queue_wait = cfg["dispatch"]["queue_wait_seconds"]
+    deadline = time.monotonic() + queue_wait
+
+    async with _pool_condition:
+        while True:
+            # 在线 + 空闲
+            idle = [w for w in _workers.values() if w.online and not w.busy]
+
+            if not idle:
+                online = [w for w in _workers.values() if w.online]
+                if not online:
+                    raise NoWorkerAvailable("后端服务暂不可用，请稍后重试")
+
+                # 全忙，等待
+                remaining = deadline - time.monotonic()
+                if remaining <= 0:
+                    raise NoWorkerAvailable("后端服务繁忙，请稍后重试")
+
+                logger.info("所有 worker 全忙（%d 在线），等待 %.1fs...", len(online), remaining)
+                try:
+                    await asyncio.wait_for(_pool_condition.wait(), timeout=remaining)
+                except asyncio.TimeoutError:
+                    raise NoWorkerAvailable("后端服务繁忙，请稍后重试")
+                continue  # 重新检查
+
+            # 取第一个空闲 worker
+            w = idle[0]
+            w.busy = True
+            logger.debug("Worker 分配: %s", w.url)
+            return w
+
+
+async def release_worker(w: WorkerState) -> None:
+    """释放 worker，标记为空闲并通知等待者。"""
+    async with _pool_condition:
+        w.busy = False
+        logger.debug("Worker 释放: %s", w.url)
+        _pool_condition.notify(1)
+
+
+# ---------------------------------------------------------------------------
+# 状态查询
+# ---------------------------------------------------------------------------
+
+def get_pool_status() -> dict:
+    """返回当前池状态（供 /gateway-health 使用）。"""
+    if not _workers:
+        return {"total": 0, "healthy": 0, "busy": 0}
+    total = len(_workers)
+    healthy = sum(1 for w in _workers.values() if w.online)
+    busy = sum(1 for w in _workers.values() if w.busy)
+    return {"total": total, "healthy": healthy, "busy": busy}