fix(sync): 依赖超时后限制就绪检查工作量

server sync/sync_server/readiness.py

@@ -0,0 +1,38 @@
+"""Bound readiness work even when a synchronous dependency ignores its timeout."""
+import asyncio
+import time
+
+
+class Readiness:
+    def __init__(self, probe, *, timeout=3, cache_seconds=5):
+        self.probe = probe
+        self.timeout = timeout
+        self.cache_seconds = cache_seconds
+        self.lock = asyncio.Lock()
+        self.running = None
+        self.until = 0.0
+        self.ok = False
+
+    @staticmethod
+    def consume(task):
+        # A request can time out or disconnect before the synchronous probe ends.
+        # Retrieve late exceptions without logging dependency messages/secrets.
+        if not task.cancelled():
+            task.exception()
+
+    async def check(self):
+        async with self.lock:
+            if time.monotonic() < self.until:
+                return self.ok
+            if self.running is None or self.running.done():
+                self.running = asyncio.create_task(asyncio.to_thread(self.probe))
+                self.running.add_done_callback(self.consume)
+            try:
+                # Cancelling a to_thread await does not stop its OS thread. Keep
+                # the task alive so subsequent requests reuse the same probe.
+                await asyncio.wait_for(asyncio.shield(self.running), self.timeout)
+                self.ok = True
+            except Exception:
+                self.ok = False
+            self.until = time.monotonic() + self.cache_seconds
+            return self.ok