I'm setting up ELB, and I'm having trouble finding a suitable metric to use to adjust the size of the pool.
RequestCount doesn't work because some requests are much cheaper than others.
Latency doesn't work because some requests are for long-polling, so maximum latency is pretty much always 60 seconds.
What I'd really like is a statistic that measures the number of open connections. I believe that's what the LoadBalancer itself uses when routing requests, so it's really surprising that it doesn't appear to be exposed in CloudWatch for us to use. Am I just missing something? Other suggestions? Am I going to have to create my own metric?