We have built ourselves an API and are busy scaling it. At current we have 6 hosts and we use DNS Round Robin to spread the load.
However a lot of our traffic comes from single source. We plug into our client system so they use one source IP to contact us. We have carried out some testing on loader.io and I have seen uneven spread.
I know round robin might not be perfect but its better than what we were using before. HAProxy on another local box to manage it? I was thinking potentially having 2 load balancers with DNS FailOver to switch if one goes down.
UPDATE: Also we want to reduce network traffic. For example if HAProxy was asking which server was the least used this increases the response time. Could we forward the HTTP request straight to the host?