通过pyinotify实现文件的监控，包括监控文件是否传输完成

叁歲伎倆 2022-09-10 08:29 159阅读 0赞

首先安装`pyinofity`，`pip install pyinotify`

# 创建Event Processor #

与linux下面的`inotify`事件机制类似，我们通过继承`ProcessEvent`来实现对`inotify`事件的重写，这里将事件名封装成`process_事件名`，例如`IN_CREATE`会经过`Event Processor`变成`process_IN_CREATE`。下面是所有的事件：

<table> 
 <thead> 
  <tr> 
   <th>Inotify Events</th> 
   <th>Description</th> 
  </tr> 
 </thead> 
 <tbody> 
  <tr> 
   <td>IN_CREATE</td> 
   <td>File/directory created in watched directory</td> 
  </tr> 
  <tr> 
   <td>IN_OPEN</td> 
   <td>File/directory opened in watched directory</td> 
  </tr> 
  <tr> 
   <td>IN_ACCESS</td> 
   <td>File accessed</td> 
  </tr> 
  <tr> 
   <td>IN_ATTRIB</td> 
   <td>Attributes of file/directory changed (e.g. permissions, timestamp, etc.)</td> 
  </tr> 
  <tr> 
   <td>IN_CLOSE_NOWRITE</td> 
   <td>Non-writable file/directory closed</td> 
  </tr> 
  <tr> 
   <td>IN_DELETE</td> 
   <td>File/directory deleted from watched directory</td> 
  </tr> 
  <tr> 
   <td>IN_DELETE_SELF</td> 
   <td>File/directory being watched deleted</td> 
  </tr> 
  <tr> 
   <td>IN_IGNORED</td> 
   <td>File/directory no longer watched, deleted, or unmounted filesystem</td> 
  </tr> 
  <tr> 
   <td>IN_MODIFY</td> 
   <td>File/directory modified</td> 
  </tr> 
  <tr> 
   <td>IN_MOVE_SELF</td> 
   <td>File/directory moved. Must monitor destination to know destination path</td> 
  </tr> 
  <tr> 
   <td>IN_MOVED_FROM</td> 
   <td>File/directory moved from one watched directory to another</td> 
  </tr> 
  <tr> 
   <td>IN_MOVED_TO</td> 
   <td>Similar to IN_MOVED_FROM except for outgoing file/directory</td> 
  </tr> 
  <tr> 
   <td>IN_Q_OVERFLOW</td> 
   <td>Event queue overflowed</td> 
  </tr> 
  <tr> 
   <td>IN_UNMOUNT</td> 
   <td>Filesystem of watched file/directory unmounted from system</td> 
  </tr> 
 </tbody> 
</table>

下面将通过一个简短的例子来展示：

import os
    import pyinotify
    
    
    class EventProcessor(pyinotify.ProcessEvent):
        _methods = ["IN_CREATE",
                    "IN_OPEN",
                    "IN_ACCESS",
                    "IN_ATTRIB",
                    "IN_CLOSE_NOWRITE",
                    "IN_CLOSE_WRITE",
                    "IN_DELETE",
                    "IN_DELETE_SELF",
                    "IN_IGNORED",
                    "IN_MODIFY",
                    "IN_MOVE_SELF",
                    "IN_MOVED_FROM",
                    "IN_MOVED_TO",
                    "IN_Q_OVERFLOW",
                    "IN_UNMOUNT",
                    "default"]
    
    
    def process_generator(cls, method):
        def _method_name(self, event):
            print("Method name: process_{}()\n"
                  "Path name: {}\n"
                  "Event Name: {}\n".format(method, event.pathname, event.maskname))
    
        _method_name.__name__ = "process_{}".format(method)
        setattr(cls, _method_name.__name__, _method_name)
    
    
    for method in EventProcessor._methods:
        process_generator(EventProcessor, method)
    
    watch_manager = pyinotify.WatchManager()
    event_notifier = pyinotify.Notifier(watch_manager, EventProcessor())
    
    watch_this = os.path.abspath("/home/vincent/software")
    watch_manager.add_watch(watch_this, pyinotify.ALL_EVENTS)
    event_notifier.loop()

这里我们可以看到，监控了一个文件夹`/home/vincent/software`，当往这个文件夹中复制一份文件时，将会打印出所有对应的事件。

Method name: process_IN_CREATE()
    Path name: /home/vincent/software/Anaconda3-2021.05-Linux-x86_64.sh
    Event Name: IN_CREATE
    
    Method name: process_IN_OPEN()
    Path name: /home/vincent/software/Anaconda3-2021.05-Linux-x86_64.sh
    Event Name: IN_OPEN
    
    Method name: process_IN_MODIFY()
    Path name: /home/vincent/software/Anaconda3-2021.05-Linux-x86_64.sh
    Event Name: IN_MODIFY
    
    Method name: process_IN_MODIFY()
    Path name: /home/vincent/software/Anaconda3-2021.05-Linux-x86_64.sh
    Event Name: IN_MODIFY
    
    Method name: process_IN_MODIFY()
    Path name: /home/vincent/software/Anaconda3-2021.05-Linux-x86_64.sh
    Event Name: IN_MODIFY
    
    Method name: process_IN_CLOSE_WRITE()
    Path name: /home/vincent/software/Anaconda3-2021.05-Linux-x86_64.sh
    Event Name: IN_CLOSE_WRITE

可以看出来，他会记录下文件操作的每一步，包括文件创建`IN_CREATE`，文件打开`IN_OPEN`，文件修改`IN_MODIFY`，文件关闭`IN_CLOSE_WRITE`

# Non-Blocking Loop非阻塞方式 #

上面的`loop()`的方式会阻塞进程，在`loop`后面的代码将不会被执行，这里有三种解决办法：

## Notifier with a timeout 使用超时 ##

在构造`notifier`时，timeout参数告诉Notifier以特定的时间间隔获取通知。

event_notifier = pyinotify.Notifier(watch_manager, EventProcessor(), timeout=10)

当使用超时时，应用程序将不会自动获得文件系统更改通知。需要在不同的时间显式调用`event_notifier.process_events()`和`event_notifier.read_events()`。也可以调用`event_notifier.check_events()`来检查是否有事件等待处理。

## ThreadedNotifier不同线程 ##

可以将程序放到另一个线程中，通过`ThreadedNotifier`而不是`Notifier`调用，然后通过`event_notifier.start()`启动

event_notifier = pyinotify.ThreadedNotifier(watch_manager, EventProcessor())
    
    watch_this = os.path.abspath("notification_dir")
    watch_manager.add_watch(watch_this, pyinotify.ALL_EVENTS)
    event_notifier.start()

## AsyncNotifier异步 ##

可以通过异步实现：

event_notifier = pyinotify.AsyncNotifier(watch_manager, EventProcessor())

然后通过调用`asyncore`中的`loop()`函数实现：

import asyncore
    asyncore.loop()

inotify的局限性也适用于pyinotify。例如，不监视递归目录;必须运行另一个inotify实例来跟踪子目录。尽管Python提供了一个方便的inotify接口，但与C实现的inotify相比，会导致性能下降。