host: real-backup

host.py

@@ -326,7 +326,8 @@ def _state_lock(path, exclusive=True):
 def _read_state_file(path):
     if os.path.exists(path):
         try:
-            return json.load(open(path))
+            with open(path) as f:
+                return json.load(f)
         except Exception:
             pass
     return {"tasks": {}, "automations": []}
@@ -356,7 +357,22 @@ def save_state(path, state):
             if k not in ("tasks", "automations"):
                 merged[k] = v
         tmp = f"{path}.tmp.{os.getpid()}"
-        json.dump(merged, open(tmp, "w"), indent=2, ensure_ascii=False)
+        with open(tmp, "w") as f:
+            json.dump(merged, f, indent=2, ensure_ascii=False)
+        if os.path.exists(path):
+            import shutil
+            backup = path + ".bak"
+            backup_1 = backup + ".1"
+            backup_2 = backup + ".2"
+            backup_tmp = f"{backup}.tmp.{os.getpid()}.{threading.get_ident()}"
+            shutil.copy2(path, backup_tmp)
+            if os.path.exists(backup_2):
+                os.remove(backup_2)
+            if os.path.exists(backup_1):
+                os.replace(backup_1, backup_2)
+            if os.path.exists(backup):
+                os.replace(backup, backup_1)
+            os.replace(backup_tmp, backup)
         os.replace(tmp, path)
         # 让调用方内存里的 state 也跟上合并结果，避免下次保存
         # 又把别的进程的任务挤掉（调用方继续用这份 state 时）。