Re: Job in background

[Dean Nizetic]

Here is what I would do if I were in tour place.

The job would be done in two parts...

Part 1.

    servlet gets the requast for calculations and

    opens new thread that does the work.

    You start the calculations and keep a reference to this object in

    some static member of some class

    (

       You can have a class with

         public static Vector CalcThreads;

       where you keep all the threads that do some calculations.

       (Of course you need to have some way to identify a Calc Job and to remove reference after some time)

    )

    when you start your Calculations you return response to user with a link that looks something like this

    http://www.address.com:port/servlet/ShowResults?CalcID

    

now goes the second part

Part 2.

    User clicks the link

    Servlet (ShowResults) finds your CalcThread using that  ID (CalcID)

    if the calculations are finished it sends back the results

    and if not you can send a message to try later and the same link again

At 06:50 1999.03.12 -0800, you wrote:

>I have a servlet that starts a long series of calculations.

>The calculations can take up to 30 minutes.

>

>This leads to 2 problems:

>1. The timeout of the server is less than 30 minutes,

>so we get a 'document contains no data'.

>2. We don't want to raise the timeout, because a user

>won't usually wait that long.

>

>We thought of the following solution:

>1. The user calls a servlet.

>2. This servlets starts a process in background that calculates

>a result and writes it to a file on the server.

>3. The user gets an immediate response with the URL of this file,

>so he can visit this URL once the calculations are finished.

>

>What is the best way to do this? A servlet calling another servlet?

>Starting a thread (but won't this thread be killed once the servlet

>has sent his response)?

>

>Is there a means to let the user know when the calculations are done

>to prevent 404 errors or having to look at an incomplete result?

>

>Thanks in advance,

>Bruno

>

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       Dean  Nizetic




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