处理来自看门狗的 OSError答案

【问题标题】：Handling OSError from Watchdog处理来自看门狗的 OSError
【发布时间】：2019-01-28 07:27:14
【问题描述】：

我一直在使用 tkinter 组合看门狗模块来处理一些上传请求。大多数情况下它工作正常，但有时我们的网络驱动器会变得不稳定并在一段时间内断开连接。但是我无法找到捕获此错误的正确位置。

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：

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.

谁能建议如何正确处理这个异常？

【问题讨论】：

啊，所以它是事件发射器，而不是事件调度程序，错误出现的地方。在您的情况下，我会尝试在WindowsApiEmitter 的子类的_read_events 中捕获异常，并将其用作emitter_class 在WindowsApiObserver 的子类中

标签： python python-3.x python-watchdog

【解决方案1】：

这就是我解决这个问题的方法：

    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，看门狗需要重新设置目录句柄，我们可以使用self.on_thread_start()。

然后使用MyEmitter 和BaseObserver，我们现在可以处理丢失和重新获得与共享驱动器的连接。

【讨论】：