I'm running IIS 10 on a Windows Server 2016 EC2 instance that sits behind an AWS ELB.

I've loaded a custom (signed) SSL Certificate on the ELB. When I attempt to load sites without https, they're loading fine - but the same site using https produced a 503 - Service Temporarily Unavailable Error. No other indications.

Whatever measures I've tried so far hasn't fixed it for me. I've tried:

  1. Application Pool Restarts
  2. Application Pool identities - both IIS User and Domain Users (making sure the same user has RW access to the application folders)
  3. Custom Error messages

Here are my Request and Response headers: Request and Response headers

My ELB Configuration is as follows: ELB Configuration

Nothing appears to work or give me any indication on what is going wrong. Where can I find definitive logs that'll tell me what the issue is?

Thank you.

  • 2
    Capture and show the response headers from 503 response, please. Is this a Classic Load Balancer or Application Load Balancer? The next steps depend on which type of balancer, because the configurations are quite different. Showing the balancer config will be potentially helpful. – Michael - sqlbot May 20 '18 at 14:16
  • Hi Michael. Thanks for your response. It is an Application Load Balancer for http and https traffic. I've added the Request & Response headers as well as the ELB config screenshots above in my question. – miCRoSCoPiCeaRthLinG May 21 '18 at 2:53
  • 1
    Are you sending https requests to the same target group as http, and if not, why not? It sounds like you are not, and the https target group has no healthy targets, due to a misconfiguration there. The headers suggest the error is being generated by the ALB, due to the misconfiguration, not the application (which is unreachable). – Michael - sqlbot May 21 '18 at 3:14
  • Spot on Michael. Yes I was sending both connections to the same target - but I'm not sure how the target instance for the https traffic got removed. Must have been me - deleted it accidentally. ::GROAN:: Thank you VERY MUCH. I know now where to check. Perhaps you can copy your answer as an answer and I can accept it then? – miCRoSCoPiCeaRthLinG May 21 '18 at 3:41

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