How to stop requests to one Azure VM in load balanced set and avoid the 503 error?

Question

I get Service unavailable 503 error occasionally after stopping app pool in one Azure VM in a load balanced set. I stopped the app pool to perform maintenance on the VM.

Is there a better way to stop requests to one VM and avoid the 503 error?

Answer 1

You can define probes associated with your load balancer. Those probes will ping each instance at a defined interval (default is 5 seconds). After consecutive retry failures (default is 2 retry failures in a row) then the load balancer will no longer route traffic to that VM. So by default the user should not encounter any 503s after 10 seconds of the VM being unresponsive.