c#多个任务在后台独立运行，互不阻塞

Question

我有一个C#Windows服务，它在里面运行一些任务。

其中一个任务是无限异步循环，其他任务由计时器触发，然后执行任务。

private readonly QueueProcessor _queueProcessor;
protected override void OnStart(string[] args)
{
// first task
_queueTask = _queueProcessor.Run(_cancellation.Token);

// second task
affiliate_timer = new System.Timers.Timer();
affiliate_timer.AutoReset = true;
affiliate_timer.Interval = _model.Interval_Affiliate * 60000;
affiliate_timer.Elapsed += new 
System.Timers.ElapsedEventHandler(affiliate_timer_Elapsed);
// third task
invoice_timer = new System.Timers.Timer();
invoice_timer.AutoReset = true;
invoice_timer.Interval = _model.Interval_Invoice * 60000;
invoice_timer.Elapsed += new 
System.Timers.ElapsedEventHandler(invoice_timer_Elapsed);
}

private void invoice_timer_Elapsed(object source, System.Timers.ElapsedEventArgs e)
{

if (!_isAffiliateBusy)
{
_isAffiliateBusy= true;

var task = Task.Run(() => StartAffiliateTask());
task.Wait();

_isAffiliateBusy= false;
}

}

private void invoice_timer_Elapsed(object source, System.Timers.ElapsedEventArgs e)
{

if (!_isInvoiceBusy)
{
_isInvoiceBusy = true;

var task = Task.Run(() => StartInvoiceTask());
task.Wait();

_isInvoiceBusy = false;
}

}

private void StartAffiliateTask()
{
_affiliateModule = new Modules.Affiliate();
_affiliateModule.RunSync();
}
private void StartInvoiceTask()
{
_invoiceModule = new Modules.Invoice();
_invoiceModule.RunSync();
}

这是我的QueueProcessor类，它实现await/async以执行无限循环作业：

public class QueueProcessor
{
private readonly IQueueBroker _serviceBroker;
public QueueProcessor()
{
}
public async Task Run(CancellationToken cancellationToken)
{
while (!cancellationToken.IsCancellationRequested)
{
var receiveMessageResponse = await _serviceBroker.ReceiveMessageAsync("test", cancellationToken);
if (!receiveMessageResponse.Messages.Any())
{
continue;
}
foreach (var message in receiveMessageResponse.Messages)
{

// some other tasks here...
await _serviceBroker.DeleteMessageAsync(message, cancellationToken);
}
}
}
}

我的Affiliate和Invoice模块类内部没有实现任何await/async代码，如下所示：

public class Affiliate
{
/// <summary>
/// Start the sync process
/// </summary>
public void RunSync()
{  
try
{
// some code here...
}
catch (Exception ex)
{

}

}
}

我的问题是：

当我的队列处理程序或无限循环正在运行时，由计时器触发的其他任务是否仍然可以独立运行？

当我使用：

var task = Task.Run(() => StartAffiliateTask());
task.Wait();

Wait方法是否会停止整个服务线程，直到该任务完成？或者这不会阻止我的StartInvoiceTask独立运行？

关于让我的3项任务相互独立运行的最佳方式，有什么建议吗？

Answer 1

总结多个潜在问题：

1. 竞争条件(访问/写入_isBusy(
2. 潜在的死锁(线程池大小较低(
3. 在出现错误或线程中止的情况下，标志的潜在不一致状态(_isBusy可以保持在"true"状态(

此外，我假设您的"任务"应该在单个实例中运行，因此如果它仍在运行，我们将发出计时器回调。您应该这样更改计时器事件处理程序(最好只是将其封装在某种类中(：

//the flag, do mention volatile modifier - it tells particular 
//systems to watch for variable changes by reference, 
//instead of just copying it into thread stack by value.
private volatile bool _isAffiliateBusy = false;
//sync object for flag to eliminate race condition
private object _affiliateSync = new object(); 
private void affiliate_timer_Elapsed(object source, System.Timers.ElapsedEventArgs e)
{
//very fast lookup at flag to filter threads which comes when task is still processing
if(_isAffiliateBusy)
return;
lock(_affiliateSync) //taking lock
{
//checking again for those threads which 'happen' to be faster than you think.
if(_isAffiliateBusy)
return;
//aquire lock for business 'task'
_isAffiliateBusy = true;
}
try
{
StartAffiliateTask();
}
finally
{
//resetting singleton business 'task' lock.
//do not forget to use finally block, to handle disposing
//even if something rise up in 'try' section - you will not be left with invalid state of flag.
_isAffiliateBusy = false; 
}
}