ajax - How do you measure the progress of a web service call?

Question

I have an ASP.NET web service which does some heavy lifting, like say,some file operations, or generating Excel Sheets from a bunch of crystal reports. I don't want to be blocked by calling this web service, so i want to make the web service call asynchronous. Also, I want to call this web service from a web page, and want some mechanism which will allow me to keep polling the server so that i can i can show some indicator of progress on the screen, like say, the number of files that have been processed. Please note that i do not want a notification on completion of the web method call, rather, i want a live progress status. How do i go about it?

Answer 1

Write a separate method on the server that you can query by passing the ID of the job that has been scheduled and which returns an approximate value between 0-100 (or 0.0 and 1.0, or whatever) of how far along it is.

E.g. in REST-style, you could make a GET request to http://yourserver.com/app/jobstatus/4133/ which would return a simple '52' as text/plain. Then you just have to query that every (second? two seconds? ten seconds?) to see how far along it is.

How you actually accomplish the monitoring on the backend hugely depends on what your process is and how it works.