如何在长时间运行的服务器操作期间与用户交互(例如确认对话框)

我拼凑了一个例子，放在github上供您查看。MVC5长时间运行输入要求示例。

请注意，这不一定是最好的设计方法。这是我最初的方法，没有经过很多思考。可能有更灵活或更复杂的模式，或者更推荐的模式。

基本上，它只是在数据库中存储作业的状态(在示例中使用实体框架)，每当它发生变化时。与某些类型的长时间运行的"同步"方法相比，持久化到磁盘或数据库具有明显的优势。

• 在等待输入时不锁定资源
• 在崩溃或服务器超时的情况下防止数据丢失
• 它允许灵活性，如果你想在一个扩展的环境中运行或恢复，或者在一个完全不同的服务器上(例如，一个非前端VM)。
• 允许更好地管理当前运行的作业。

对于本例，我选择不使用Signalr，因为它不会增加重要的值。对于长时间运行的作业(比如5分钟以上)，亚秒级的响应不会增加用户体验。我建议每1-2秒从javascript轮询一次。更加简单。

请注意，有些代码相当粗糙;例如，在ResumableJobState表上复制Input字段。

流可能看起来像这样，

• 上传文件>返回文件名//在我的例子中不是impl
• call StartJob(filename)>返回(Json)Job
• Poll GetJobState(jobId)>返回(Json)Job
• 如果(Json)工作。RequiredInputType被填充，向用户显示一个适当的表单来提交输入
• 使用正确类型的输入从适当的表单调用PostInput
• 作业将恢复

下面是主JobController的转储。

public class JobController : Controller
{
    private Context _context;
    private JobinatorService _jobinatorService;
    public JobController()
    {
        _context = new Context();
        _jobinatorService = new JobinatorService(_context);
    }
    public ActionResult Index()
    {
        ViewBag.ActiveJobs = _context.LongRunningJobs.Where(t => t.State != "Completed").ToList();//TODO, filter by logged in User
        return View();
    }
    [HttpPost]
    public JsonResult StartJob(string filename)//or maybe you've already uploaded and have a fileId instead
    {
        var jobState = new ResumableJobState
        {
            CurrentIteration = 0,
            InputFile = filename,
            OutputFile = filename + "_output.csv"
        };
        var job = new LongRunningJob
        {
            State = "Running",
            ResumableJobState = jobState
        };
        _context.ResumableJobStates.Add(jobState);
        _context.LongRunningJobs.Add(job);
        var result = _context.SaveChanges();
        if (result == 0) throw new Exception("Error saving to database");
        _jobinatorService.StartOrResume(job);
        return Json(job);
    }
    [HttpGet]
    public JsonResult GetJobState(int jobId)
    {
        var job = _context.LongRunningJobs.Include("ResumableJobState.RequiredInputType").FirstOrDefault(t => t.Id == jobId);
        if (job == null)
            throw new HttpException(404, "No job found with that Id");
        return Json(job, JsonRequestBehavior.AllowGet);
    }
    [HttpPost]
    public JsonResult PostInput(int jobId, RequiredInputType userInput)
    {
        if (!ModelState.IsValid)
            throw new HttpException(500, "Bad input");
        var job = _context.LongRunningJobs.Include("ResumableJobState.RequiredInputType").FirstOrDefault(t => t.Id == jobId);
        job.ResumableJobState.BoolInput = userInput.BoolValue;
        job.ResumableJobState.IntInput = userInput.IntValue;
        job.ResumableJobState.FloatInput = userInput.FloatValue;
        job.ResumableJobState.StringInput = userInput.StringValue;
        _context.SaveChanges();
        if (job == null)
            throw new HttpException(404, "No job found with that Id");
        if (userInput.InputName == job.ResumableJobState.RequiredInputType.InputName)//Do some checks to see if they provided input matching the requirements
            _jobinatorService.StartOrResume(job);
        //TODO have the jobinator return the State after it's resumed, otherwise we need another Get to check the state. 
        return Json(job);
    }
    /// <summary>
    /// Stuff this in it's own service.  This way, you could use it in other places; for example starting scheduled jobs from a cron job
    /// </summary>
    public class JobinatorService//Ideally use Dependency Injection, or something good practicey to get an instance of this
    {
        private Context _context = new Context();
        private string _filePath = "";
        public JobinatorService(Context context)
        {
            _context = context;
            _filePath = AppDomain.CurrentDomain.GetData("DataDirectory").ToString() + "/";
        }
        public void StartOrResume(LongRunningJob job)
        {
            Task.Run(() =>
            {
                using (var inputFile = System.IO.File.OpenRead(_filePath + job.ResumableJobState.InputFile))
                using (var outputFile = System.IO.File.OpenWrite(_filePath + job.ResumableJobState.OutputFile))
                {
                    inputFile.Position = job.ResumableJobState.CurrentIteration;
                    for (int i = (int)inputFile.Position; i < inputFile.Length; i++)//casting long to int, what could possibly go wrong?
                    {
                        if (job.State == "Input Required" && job.ResumableJobState.RequiredInputType != null)
                        {//We needed input and received it
                            //You might want to do a switch..case on the various inputs, and branch into different functions
                            if (job.ResumableJobState.RequiredInputType.InputName == "6*7")
                                if (job.ResumableJobState.RequiredInputType.IntValue.Value == 42)
                                    break;//Pass Go, collect 42 dollars;
                        }
                        outputFile.WriteByte((byte)inputFile.ReadByte());//Don't try this at home!
                        job.ResumableJobState.CurrentIteration = i;//or row, or line, or however you delimit processing
                        job.ResumableJobState.InputFileBufferReadPosition = inputFile.Position;//or something
                        if (i % 7 == 0)
                            job.ResumableJobState.RequiredInputType = _context.RequiredInputTypes.First(t => t.InputName == "Row 7 Input");
                        if (i % 42 == 0)
                            job.ResumableJobState.RequiredInputType = _context.RequiredInputTypes.First(t => t.InputName == "6*7");
                        if (job.ResumableJobState.RequiredInputType != null)
                            job.State = "Input Required";
                        _context.SaveChanges();
                        if (job.State != "Running")
                            return;
                    }
                    job.State = "Completed";
                    _context.SaveChanges();
                }
            });
            return;
        }
    }
}