Notifying the user after a long Ajax task when they might be on a different page

Question

I have an Ajax request to a web service that typically takes 30-60 seconds to complete. In some cases it could take as long as a few minutes. During this time the user can continue working on other tasks, which means they will probably be on a different page when the task finishes.

Is there a way to tell that the original request has been completed? The only thing that comes to mind is to:

• wrap the web service with a web service of my own
• use my web service to set a flag somewhere
• check for that flag in subsequent page requests

Any better ways to do it? I am using jQuery and ASP.Net, if it matters.

Answer 1

I would say you'd have to poll once in a while to see if request has ended and show some notifications, like this site does with badges for example.

Answer 2

You could add another method to your web service that allows you to check the status of a previous request. Then you can use ajax to poll the web service every 30 seconds or so. You can store the request id or whatever in Session so your ajax call knows what request ID to poll no matter what page you're on.

Answer 3

You could use frames on your site, and perform all your long AJAX requests in an invisible frame. Frames add a certain level of pain to development, but might be the answer to your problems.

The only other way I could think of doing it is to actually load the other pages via an AJAX request, such that there are no real page reloads - this would mean that the AJAX requests aren't interrupted, but may cause issues with breaking browser functionality (back/forward, bookmarking, etc).

Answer 4

At first make your request return immediately with something like "Started processing...". Then use a different request to poll for the result. It is not good neither for the server nor the client's browser to have long open HTTP sessions. Moreover the user should be informed and educated that he is starting a request that could take some time to complete.

To display the result you could have a"notification area" in all of your web pages. Alternatively you could have a dedicated page for this and instruct the user to navigate there. As others have suggested you could use polling to get the result.

Answer 5

Since web development is stateless (you can't set a trigger/event on a server to update the client), the viable strategy is to setup up a status function that you can intermittently call using a javascript timer to check whether your code has finished executing. When it finishes, you can update your view.