You can configure a list of servers listening for messages. According to the docs, logstash-forwarder will pick one at random until it appears to be dead or unresponsive.
"servers": [ "10.10.10.1:5043", "10.10.10.2:5043" ],
I wonder whether you can use Round Robin DNS to balance the load:
"servers": [ "domain-with-multiple-ip-addresses:5043" ],
I'd like to do that to avoid the need to reconfigure all the forwarders every time you deploy a new listening server or when a server changes its IP. Would logstash-forwarder be able to reconnect given that configuration?