处理来自Watchdog的OSError

Question

我一直在使用tkinter和watchdog模块来处理上传请求。大部分时间都能正常工作，但有时我们的网络驱动器会变得不稳定并断开连接一段时间。然而，我无法找到正确的位置来捕获此错误。

from watchdog.observers import Observer
from watchdog.events import FileSystemEventHandler
import tkinter as tk

root = tk.Tk()
path = [r"Network path 1",r"Network path 2"]

class MyGui:
    def __init__(self,master):
        self.master = master
        self.but = tk.Button(master,text="Click to start observer",command=self.start_observer)
        self.but.pack()

    def start_observer(self):
        for i in path:
            observer.schedule(event_handler, path=i, recursive=False)
        observer.start()
        self.but.config(state="disabled",text="observer started")
        print ("Observer started")

class MyHandler(FileSystemEventHandler):
    def on_created(self, event):
        current_file = event.src_path
        print (current_file)

event_handler = MyHandler()
observer = Observer()

gui = MyGui(root)
root.mainloop()

这是我让它运行几天后得到的结果：

Exception in thread Thread-4:
Traceback (most recent call last):
  File "C:\Users\AppData\Local\Programs\Python\Python37\lib\threading.py", line 917, in _bootstrap_inner
    self.run()
  File "C:\Users\AppData\Local\Programs\Python\Python37\lib\site-packages\watchdog\observers\api.py", line 146, in run
    self.queue_events(self.timeout)
  File "C:\Users\AppData\Local\Programs\Python\Python37\lib\site-packages\watchdog\observers\read_directory_changes.py", line 75, in queue_events
    winapi_events = read_events(self._handle, self.watch.is_recursive)
  File "C:\Users\AppData\Local\Programs\Python\Python37\lib\site-packages\watchdog\observers\winapi.py", line 346, in read_events
    buf, nbytes = read_directory_changes(handle, recursive)
  File "C:\Users\AppData\Local\Programs\Python\Python37\lib\site-packages\watchdog\observers\winapi.py", line 306, in read_directory_changes
    raise e
  File "C:\Users\AppData\Local\Programs\Python\Python37\lib\site-packages\watchdog\observers\winapi.py", line 302, in read_directory_changes
    ctypes.byref(nbytes), None, None)
  File "C:\Users\AppData\Local\Programs\Python\Python37\lib\site-packages\watchdog\observers\winapi.py", line 107, in _errcheck_bool
    raise ctypes.WinError()
OSError: [WinError 64] The specified network name is no longer available.

有人能建议如何正确处理这个异常吗？

- Henry Yik

---

啊，所以错误出现在事件发射器而不是事件分派器。在您的情况下，我建议在WindowsApiEmitter的子类的_read_events中捕获异常，并将其用作WindowsApiObserver的子类中的emitter_class。 - shmee

Answer 1

这是我解决此问题的方法：

    from watchdog import observers
    from watchdog.observers.api import DEFAULT_OBSERVER_TIMEOUT, BaseObserver


    class MyEmitter(observers.read_directory_changes.WindowsApiEmitter):
        def queue_events(self, timeout):
            try:
                super().queue_events(timeout)
            except OSError as e:
                print(e)
                connected = False
                while not connected:
                    try:
                        self.on_thread_start()  # need to re-set the directory handle.
                        connected = True
                        print('reconnected')
                    except OSError:
                        print('attempting to reconnect...')
                        time.sleep(10)


    observer = BaseObserver(emitter_class=MyEmitter, timeout=DEFAULT_OBSERVER_TIMEOUT)
    ...

子类化 WindowsApiEmitter 以捕获 queue_events 中的异常。为了在重新连接后继续，监视器需要重新设置目录句柄，我们可以使用 self.on_thread_start() 完成。

然后使用 MyEmitter 和 BaseObserver，我们现在可以处理共享驱动器失去和恢复连接的情况。

- Jon