c# – 在Windows服务中异步运行外部进程

我正在编写一个将csv文件从“queue”文件夹移动到“processing”文件夹的程序,然后以csv文件路径作为参数启动名为import.exe的第三方进程. Import.exe是一个长期运行的任务.我需要程序继续运行并检查队列中的新文件...

我正在编写一个将csv文件从“queue”文件夹移动到“processing”文件夹的程序,然后以csv文件路径作为参数启动名为import.exe的第三方进程. Import.exe是一个长期运行的任务.

我需要程序继续运行并检查队列中的新文件.出于这个原因,我选择了一个Windows服务应用程序,因为它将长期运行.

我的问题是我对选项感到不知所措,无法理解我是否应该用background threads或parallel programming解决这个问题,或者很可能是两者的结合.

到目前为止,我有这个代码只是同步运行.
您很快就会看到,我只是疯狂地解决流程而无需管理或检查完成情况.我已经注释掉了process.WaitForExit(),显然这是一个阻塞调用.

public int maxConcurrentProcesses = 10;
protected override void OnStart(string[] args)
    {
        // Set up a timer to trigger every minute.
        System.Timers.Timer timer = new System.Timers.Timer(60000);            
        timer.Elapsed += new System.Timers.ElapsedEventHandler(this.OnTimer);
        timer.Start();
    }

private void OnTimer(object sender, System.Timers.ElapsedEventArgs args)
    {            
        // How many instances of import.exe are running?
        Process[] importProcesses = Process.GetProcessesByName("import");
        int countRunning = importProcesses.Count();

        // If there are less than maxConcurrentProcesses, create as many as needed to reach maxConcurrentProcesses
        if (countRunning < maxConcurrentProcesses)
        {
            int processesToStart = maxConcurrentProcesses - countRunning;
            for (int i = 0; i < processesToStart; i++)
            {
                FireOffImport();
            }
        }
    }

private void FireOffImport()
    {
        // Get the first file returned from the Queue folder
        string filePathSource = GetNextCSVInQueue();

        if (filePathSource != "")
        {
            // …
            // commandArguments = create our arguments here
            // …        
            // Move the file to processing folder here
            // … 

            // Give a new process the import tool location and arguments
            ProcessStartInfo startInfo = new ProcessStartInfo(importLocation + "\\import.exe", commandArguments);
            try
            {
                Process process = Process.Start(startInfo);
                // process.WaitForExit(20000);
                // If the process has exited, there will be 4 csv files created in the same directory as the file.                  
            }
            catch (Exception ex)
            {
               // Deal with exception here
            }
       }
    }

我还尝试创建一个Task数组,并异步运行它们.但最后我仍然需要调用Task.WaitAll()才能读取结果.因此,即使提前结束,它也必须等待最长的运行任务.

我想我需要尝试循环创建可能使用任务的异步流程,但我不明白如何将其作为后台进程,这样我就可以让服务计时器检查进程数量是否需要创建更多.

解决方法:

您想到的代码的第一个改进是删除计时器并将其替换为System.IO.FileSystemWatcher和Created事件的事件处理程序.这样,您的代码无需管理之前队列中的哪些文件以及哪些新文件已到达.通常,减少代码=减少问题.

其次,单词“Task”认真地暗示要在1个System.IO.Tasks.Task实例中真正执行完整的导入任务,包括生成相应的导入流程实例并在完成后等待它退出.

如果您希望随时限制运行的导入进程数量,则可以使用调度程序替换调度程序,该调度程序允许与默认调度程序相比并行运行limits the amount of tasks.如果每个任务与1个导入程序实例关联,并且允许最多N个任务同时运行,则导入程序进程的最多N个实例.

下面的代码显示(以控制台应用程序的形式),上面描述的内容如何,??减去提供的链接中涵盖的自定义调度程序.

using System.Threading.Tasks;

namespace ConsoleApplication4
{
    class Program
    {
        static string importerProcessName = "import.exe";
        static string RootFolder = @"E:\temp\A\";
        static string queuePath = System.IO.Path.Combine(RootFolder, "Queue" );
        static string processingPath = System.IO.Path.Combine(RootFolder, "Processing");
        static string donePath = System.IO.Path.Combine(RootFolder, "Done");
        static void Main(string[] args)
        {
            GrantFolders(); // Make sure we have all our folders ready for action...
            var watcher = new System.IO.FileSystemWatcher(queuePath, "*.txt");
            watcher.Created += watcher_Created;
            watcher.EnableRaisingEvents = true;
            System.Console.ReadLine();
        }
        static Task ProcessFile( string fileName )
        {
            Task task = new Task(() =>
            {
                System.Console.WriteLine("Processing: " + fileName);
                System.IO.File.Move(System.IO.Path.Combine(queuePath, fileName), System.IO.Path.Combine(processingPath, fileName));
                string commandLine = "-import " + System.IO.Path.Combine(processingPath, fileName);
                using (var importer = new System.Diagnostics.Process())
                {
                    importer.StartInfo = new System.Diagnostics.ProcessStartInfo(importerProcessName, commandLine);
                    importer.Start();
                    importer.WaitForExit(20000);
                    System.IO.File.Move(System.IO.Path.Combine(processingPath, fileName), System.IO.Path.Combine(donePath, fileName));
                    System.Console.WriteLine("Done with: " + fileName);
                }
            });
            return task;
        }
        static void watcher_Created(object sender, System.IO.FileSystemEventArgs e)
        {
            System.Console.WriteLine("Found in queue: " + e.Name);
            var task = ProcessFile(e.Name);
            task.Start();
        }

        private static void GrantFolders()
        {
            string[] paths = new string[] { queuePath, processingPath, donePath };
            foreach( var path in paths)
            {
                if(!System.IO.Directory.Exists(path))
                {
                    System.IO.Directory.CreateDirectory(path);
                }
            }
        }
    }
}