I am having some trouble with what should be a very basic configuration on an Ubuntu 16.04 server to use haproxy to load balance incoming metrics across two carbon-relay processes. Haproxy is only creating a TCP connection to the first server in the list of servers in the "listen" section. Also, when I tcpdump and watch for both carbon-relay ports, only the one connected receives any metrics from haproxy, but if I enable the "check" parameter in the server entries, the health checks do show up in the tcpdump output.
If I comment out the first server, or reverse their order, it does connect to the other server, and other testing doesn't indicate any problems with the carbon-relay processes, so I'm stumped as to why it will only connect to one server.
I have tried roundrobin, static-rr, and leastconn for the balance option, as well.
Here's a gist with the relevant sections of haproxy.cfg and carbon-relay.conf, plus the netstat output to show the listening ports and tcp connection to the one server.