IIS6 HTTP request prioritization

Question

Hi all,

I am submitting POST requests to an external server running IIS6. This is a time critical request where I want to ensure that my request is processed at a specific time (say 10:00:00 AM). No earlier. And I want to ensure that at that specific time, my request is assigned the highest priority over other requests. Would any of this help:

• Sending most of the message a few seconds early and sending the last byte or so a few milliseconds prior to 10:00:00. Not sure if this will help as I will be competing with other requests that come in around that time. Will IIS assign a higher priority to my request based on how long I am connected?
• Anything that I can add to the message header to tell the server to queue my request and process only at a specific time?

Any known hacks that I can leverage?

Answer 1

No - HTTP is not a real time protocol. It usually runs on top of TCP/IP which is not a real time protocol. While you can get near real-time behaviour out of such an architecture its far from simple - don't take my word for it - go read the source code for xntpd.

Having said that you give no details of the actual level of precision you require - but your post implies that it could be up to a second - which is a very long time for submitting a request to a webserver. On the other hand, scheduling such an event to fire client side with this level of accuracy is very difficult - I've not tried measuring the accuracy of the scheduler on MSWindowsNT but elsewhere I'd only expect it to be accurate to about 5 minutes. So you'd need to schedule the job to start 5 minutes early then sleep for 10 milliseconds at a time until the target time rolls around.

But then again, thinking about why you need to run any job with any sort of timing accuracy makes me think that you're trying to solve the problem the wrong way.

C.

Answer 2

It sounds like you need more of a scheduler system then trying to use http. HTTP is a stateless protocol, you send a request to IIS, you get a response.

What you might want to consider is taking that request, and then storing the information you require somewhere (database). Then using some sort of scheduler (cronjobs, scheduled tasks) you action that information at the desired time.

What you want, you probably can't achieve with IIS, it's not what it is designed to do.