From your description though I imagine it might have the same drawbacks that exist with the multiple HAProxy + iptables swap solution. With a solution where we run multiple HAProxies and move traffic between them I worry about port exhaustion, long running connections, and the maintenance costs of the infrastructure. It could just be the case that we're talking about different problems. At Yelp we have hundreds of services that are added, changed, moved, and removed from physical machines causing our internal HAProxies (which listen on hundreds of ports and many have long running connections) to reload pretty constantly.
As all engineering decisions, I could very easily be wrong and be overestimating the complexity involved with the multiple HAProxy instance solution. At the end of the day I made a call based on the data available, and I decided the solution I talked about in the blog post was lowest risk.
From your description though I imagine it might have the same drawbacks that exist with the multiple HAProxy + iptables swap solution. With a solution where we run multiple HAProxies and move traffic between them I worry about port exhaustion, long running connections, and the maintenance costs of the infrastructure. It could just be the case that we're talking about different problems. At Yelp we have hundreds of services that are added, changed, moved, and removed from physical machines causing our internal HAProxies (which listen on hundreds of ports and many have long running connections) to reload pretty constantly.
As all engineering decisions, I could very easily be wrong and be overestimating the complexity involved with the multiple HAProxy instance solution. At the end of the day I made a call based on the data available, and I decided the solution I talked about in the blog post was lowest risk.