checking if a thread is alive

Question

for a task, potentially taking too long to complete, I'd like a mechanism

to start the task
return back to user interface (its a web page)
periodically/randomly check if the task is complete
cancel the executing task when user wishes so
get notified when the task completes / fails

what are the possible solutions?

Threads? Start a thread, save its ManagedThreadId, (can you get a thread by its id)
write a windows service, send the request to service via shared objects/files/db? keep interacting with the service the same way (objects/files/db,etc) Services?

What version of .NET are you using? Sounds like the Task Parallel Library in .NET 4 would be ideal for this... — Jon Skeet
– Jon Skeet, Commented Oct 21, 2011 at 6:37
@Hasan - ah, hadn't seen that bit. Not in the web server itself, but quite possibly in a service backing the UI. Tasks could definitely still be relevant. — Jon Skeet
– Jon Skeet, Commented Oct 21, 2011 at 6:43
@HasanKhan: Well, if you start it as "long running" the scheduler should take that into account. Fundamentally if you're starting multiple threads, tasks, whatever then they will be contending for time. — Jon Skeet
– Jon Skeet, Commented Oct 21, 2011 at 7:34
@JonSkeet you're right. Just checked that LongRunningTask actually creates a new thread instead of using thread in a thread pool. — Muhammad Hasan Khan
– Muhammad Hasan Khan, Commented Oct 21, 2011 at 7:41

Muhammad Hasan Khan · Accepted Answer · 2011-10-21 06:38:06Z

Host a WCF Service in a Windows Service that will perform the background tasks by adding/reading from a queue which can be maintained either using MSMQ or in a database.

When you add an item for processing; you should get a task id. You should be able to then log the completion/failed/cancel status of the task in db against the task id.

You can have following methods in your WCF contract

int ProcessItem(ItemDetails details); // returns task id bool CancelTask(int taskID); // returns true if successfully cancelled; false otherwise TaskStatus GetTaskStatus(int taskID); // returns Cancelled, Waiting, Failed or Completed

that looks like a good general solution, that can be paired up with a Request/Response Message system, sharing a RequestId.

Boas Enkler · Accepted Answer · 2011-10-21 06:40:23Z

You can do that in single process Have a look at the Task Paralell Library and / or TPL DataFlow

http://msdn.microsoft.com/en-us/library/dd460717.aspx http://go.microsoft.com/fwlink/?LinkId=205053

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