尽管使用 Polly，但删除文件在使用时会引发异常

发布于 2025-01-10 04:33:27 字数 1209 浏览 3 评论 0原文

我正在尝试创建某种 C# 应用程序原型。我的目标是在文件可用时将其删除，这样就不会被另一个进程锁定。很多时候我需要读取/删除/移动仍在使用的文件，因为它们是由网络上的另一个应用程序写入的。网络延迟导致文件使用异常。

在我的演示中，我创建了另一个控制台应用程序，每 5 秒写入一次。一行到同一个文件，同时它保持文件打开，所以这将起作用。

因此，我想将删除/移动操作包装在 Polly 策略中，但是当我尝试时，仍然有 IOException: 文件正在被另一个进程使用。我以为这是 Polly 捕获的，但显然我错了......

这段代码有什么问题？
当我查看 InnerException 时，它是 null 吗？

static void Main(string[] args)
{     
    var MAX_RETRIES = 5;

    Console.WriteLine($"Attempting to delete the file {fileName}\r\nPress any key to continue....");
    Console.ReadKey();

    //Build the policy
    var retryPolicy = Policy
        .Handle<IOException>()
        .Or<Exception>()
        .Retry(MAX_RETRIES);

    //Execute the error prone code with the policy
    retryPolicy.Execute(() =>
    {
        Console.WriteLine($"Starting File-deleting on {fileName}");
        if (File.Exists(fileName))
            File.Delete(fileName);      // <== here's where the exception occurs !

        Console.WriteLine("File deleted");
    });

    Console.WriteLine("Press any key to quit");
    
    var s = Console.ReadLine();
    if (s == "quit");
    Environment.Exit(0);
}

原文

I'm trying to create some sort of prototype of a C# application. My goal is to delete a file when it becomes available, so not locked by another process. Lots of times I need to read/delete/move files which are still in use cause they are being written by another application on the network. Network-delay causes the file-in-use exception.

For my demo I created another console application which writes every 5 sec. a line to the same file and in the mean time it keeps the file open, so this will work.

So I want to wrap the delete/move action in a Polly policy, but when I'll try there is still the IOException: file in use by another process. I assumed this was captured by Polly, but apparently I'm wrong...

What's wrong in this code ?
When I take a look at the InnerException, it's null ?

static void Main(string[] args)
{     
    var MAX_RETRIES = 5;

    Console.WriteLine(quot;Attempting to delete the file {fileName}\r\nPress any key to continue....");
    Console.ReadKey();

    //Build the policy
    var retryPolicy = Policy
        .Handle<IOException>()
        .Or<Exception>()
        .Retry(MAX_RETRIES);

    //Execute the error prone code with the policy
    retryPolicy.Execute(() =>
    {
        Console.WriteLine(quot;Starting File-deleting on {fileName}");
        if (File.Exists(fileName))
            File.Delete(fileName);      // <== here's where the exception occurs !

        Console.WriteLine("File deleted");
    });

    Console.WriteLine("Press any key to quit");
    
    var s = Console.ReadLine();
    if (s == "quit");
    Environment.Exit(0);
}

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ゃ人海孤独症 2025-01-17 04:33:27

这有点超出了我的专业知识，因为我从未使用过 Polly，但可以尝试的一件事是在 if(file.Exists(filename)) 内部抛出一个 try catch。仅提出这一点，因为它看起来不像您在检查它是否存在后检查它是否正在使用。

Console.WriteLine($"Starting File-deleting on {fileName}");
if (File.Exists(fileName))
{
    try
    {
        File.Delete(fileName);
        Console.WriteLine("File deleted");
    } 
    catch
    { 
        Console.WriteLine("File in use..."); 
    }      
}

This is a little above my expertise as I have never used Polly, but one thing to try would be to throw a try catch inside of the if(file.Exists(filename)). Only bringing this up as it doesn't look like you are ever checking if it is in use after checking if it exists.

Console.WriteLine(quot;Starting File-deleting on {fileName}");
if (File.Exists(fileName))
{
    try
    {
        File.Delete(fileName);
        Console.WriteLine("File deleted");
    } 
    catch
    { 
        Console.WriteLine("File in use..."); 
    }      
}

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