We have been using nginx as a reverse-proxy for a php farm, with "manual weight settings" for upstream hosts. The maybe 30 php backend servers are of wildly different power. We cannot change that.
We have reached the point where we cannot keep up with adjusting those weights manually any longer. Random spikes on individual upstream hosts will kill them before we can adjust weight. While other hosts are idle. (!)
What would be an alternative to manual weighted round-robin? Preferably an automatic solution based on the real upstream system load.