功能：完善加氢站导航详情与缓存刷新

station-navigation/server.py

@@ -31,6 +31,8 @@ STATION_CACHE_SECONDS = int(os.getenv("STATION_NAVIGATION_CACHE_SECONDS", "120")
 VEHICLE_MAP_INTERNAL_BASE_URL = os.getenv("VEHICLE_MAP_INTERNAL_BASE_URL", "http://127.0.0.1:20800").rstrip("/")
 _cache_lock = threading.Lock()
 _cache = {}
+_cache_load_locks = {}
+_cache_refreshing = set()
 
 
 def _static_asset_version():
@@ -80,16 +82,51 @@ def _post_open_platform(path, body):
     return payload.get("data") or []
 
 
+def _refresh_cached_value(key, loader):
+    try:
+        value = loader()
+    except Exception as exc:
+        print("{} cache background refresh deferred: {}".format(key, exc))
+    else:
+        with _cache_lock:
+            _cache[key] = (time.time(), value)
+    finally:
+        with _cache_lock:
+            _cache_refreshing.discard(key)
+
+
+def _start_cache_refresh(key, loader):
+    threading.Thread(target=_refresh_cached_value, args=(key, loader), daemon=True).start()
+
+
 def _cached(key, ttl_seconds, loader):
     now = time.time()
+    refresh_in_background = False
     with _cache_lock:
         cached = _cache.get(key)
         if cached and now - cached[0] < ttl_seconds:
             return cached[1]
-    value = loader()
-    with _cache_lock:
-        _cache[key] = (now, value)
-    return value
+        if cached:
+            if key not in _cache_refreshing:
+                _cache_refreshing.add(key)
+                refresh_in_background = True
+            stale_value = cached[1]
+        else:
+            stale_value = None
+        load_lock = _cache_load_locks.setdefault(key, threading.Lock())
+    if cached:
+        if refresh_in_background:
+            _start_cache_refresh(key, loader)
+        return stale_value
+    with load_lock:
+        with _cache_lock:
+            cached = _cache.get(key)
+        if cached:
+            return _cached(key, ttl_seconds, loader)
+        value = loader()
+        with _cache_lock:
+            _cache[key] = (time.time(), value)
+        return value
 
 
 def _load_station_directory():
@@ -137,7 +174,7 @@ class StationNavigationHandler(SimpleHTTPRequestHandler):
             return
         if path == "/api/stations":
             try:
-                self._write_json(200, _cached("station-directory", STATION_CACHE_SECONDS, _load_station_directory))
+                payload = _cached("station-directory", STATION_CACHE_SECONDS, _load_station_directory)
             except Exception as exc:
                 self.log_error("station directory refresh failed: %s", exc)
                 self._write_json(502, {
@@ -145,6 +182,8 @@ class StationNavigationHandler(SimpleHTTPRequestHandler):
                     "code": "UPSTREAM_UNAVAILABLE",
                     "message": "加氢站数据暂时不可用，请稍后重试",
                 })
+                return
+            self._write_json(200, payload)
             return
         if path == "/assets/logo_light.svg":
             self._serve_logo()
@@ -213,7 +252,10 @@ class StationNavigationHandler(SimpleHTTPRequestHandler):
         self.send_header("Cache-Control", "no-store")
         self.send_header("Content-Length", str(len(body)))
         self.end_headers()
-        self.wfile.write(body)
+        try:
+            self.wfile.write(body)
+        except (BrokenPipeError, ConnectionResetError):
+            self.log_message("client disconnected before JSON response completed")
 
 
 if __name__ == "__main__":