ASP MVC: Can I drop a client connection programatically?

Question

I have an ASP.NET Web API application running behind a load balancer. Some clients keep an HTTP busy connection alive for too much time, creating unnecessary affinity and causing high load on some server instances. In order to fix that, I wish to gracefully close a connection that is doing too much requests in a short period of time (thus forcing the client to reconnect and pick a different server instance) while at same time keeping low traffic connections alive indefinitely. Hence I cannot use a static configuration.

Is there some API that I can call to flag a request to "answer this then close the connection" ? Or can I simply add the Connection: close HTTP header that ASP.NET will see and close the connection for me?

Answer 1

It looks like the good solution for your situation will be the built-in IIS functionality called Dynamic IP restriction. "To provide this protection, the module temporarily blocks IP addresses of HTTP clients that make an unusually high number of concurrent requests or that make a large number of requests over small period of time."

It is supported by Azure Web Apps: https://azure.microsoft.com/en-us/blog/confirming-dynamic-ip-address-restrictions-in-windows-azure-web-sites/

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Answer 2

I am not 100% sure this would work in your situation, but in the past I have had to block people coming from specific IP addresses geographically and people coming from common proxies. I created an Authorized Attribute class following:

http://www.asp.net/web-api/overview/security/authentication-filters

In would dump the person out based on their IP address by returning a HttpStatusCode.BadRequest. On every request you would have to check a list of bad ips in the database and go from there. Maybe you can handle the rest client side, because they are going to get a ton of errors.