在与StreamReader的并发文件访问的情况下引发的异常 [英] Raised exception in the case of concurrent file access with StreamReader

问题描述

我发现了一个后谈论处理并发文件访问与StreamWriter的。

现在的问题是，答案不管理该文件被访问，但多进程的场景。

The problem is that the answers do not manage the scenario where the file is being accessed but multiple processes.

让我们告诉它不久：

• 我有多个应用程序


• 我需要一个集中的日志系统数据库


• 如果数据库失败了，我需要一个文件系统日志后备

有是一个已知的并发情况下，多个应用程序（进程）将尝试在该文件中写入。
这可以通过重新尝试一个短暂的延迟后的写入进行管理。
，而我不想OT重新尝试，如果它是一个安全错误或文件名语法错误

There is a known concurrency scenario, where multiple applications (processes) will try to write in that file. This can be managed by re-attempt the writing after a short delay. But I don't want ot reattempt if it's a security error or filename syntax error.

中的代码是在这里：

// true if an access error occured
bool accessError = false;
// number fo writing attemps
int attempts = 0;

do
{
    try
    {
        // open the file
        using (StreamWriter file = new StreamWriter(filename, true))
        {
            // write the line
            file.WriteLine(log);
            // success
            result = true;
        }
    }
        /////////////// access errors ///////////////
    catch (ArgumentException)
    {
        accessError = true;
    }
    catch (DirectoryNotFoundException)
    {
        accessError = true;
    }
    catch (PathTooLongException)
    {
        accessError = true;
    }
    catch (SecurityException)
    {
        accessError = true;
    }
        /////////////// concurrent writing errors ///////////////
    catch (Exception)
    {
        // WHAT EXCEPTION SHOULD I CATCH HERE ?
        // sleep before retrying
        Thread.Sleep(ConcurrentWriteDelay);
    }
    finally
    {
        attempts++;
    }
    // while the number of attemps has not been reached
} while ((attempts < ConcurrentWriteAttempts)
            // while we have no access error
            && !accessError
            // while the log is not written
            && !result);

我唯一的问题是，异常的类型将在提高案例并发，书写。我已经知道的东西可以分别进行。让我补充几个方面的考虑：

My only question is the type of exception that will be raised in the case of concurrency writting. I already know things can be done differently. Let me add a few considerations :

• 不，我不希望在场景中使用NLOG


• 是我处理与国际奥委会+互斥并发的过程中的并发


• 是的，我真的希望所有登录同一个文件

写入

• No, I don't want to use NLog in that scenario
• Yes I handle concurrency with IOC + Mutex for the in-process concurrency
• Yes I really want all log to be written in the same file

推荐答案

这将是一个 IOException异常文本：

该进程无法访问文件，因为它正被另一个进程使用{0}。

"The process cannot access the file '{0}' because it is being used by another process."

这是一个简单的方法：

 static bool LogError(string filename, string log)
    {
        const int MAX_RETRY = 10;
        const int DELAY_MS = 1000; // 1 second
        bool result = false;
        int retry = 0;
        bool keepRetry = true;
        while (keepRetry && !result && retry < MAX_RETRY )
        {
            try
            {
                using (StreamWriter file = new StreamWriter(filename, true))
                {
                    // write the line
                    file.WriteLine(log);
                    // success
                    result = true;
                }
            }
            catch (IOException ioException)
            {
                Thread.Sleep(DELAY_MS);
                retry++; 
            }
            catch (Exception e)
            {

                keepRetry = false;
            }

        }
        return result;
    }

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