This small software listens for udp packets on a given port and then forwards these to a set of hosts via udp. The set of hosts is discovered by resolving a dns name and the data is sent to all the addresses that are returned.

I needed something that could manage multiple uwsgi workers subscribing to a variable set of subscription servers to perform load balancing for some web applications. The case for disconnecting/dying workers is already handled by the subscription server, but there is no way of telling an already running worker to subscribe to another subscription server without having to restart it, reconfigure it or in any case touch it. With this hack the subscription server ip for the workers is always fixed to the host that is running usss, so that when a subscription server changes the worker has no knowledge of it and transparently registers to all available subscription server/frontends.

It's written in go so it should JustWork(tm) with go > 1.4. Just run

go build .

in the checked out dir to build. I decided against an installable package since this is a binary that is standalone and will be rarely updated.

A typical usage might be

usss -dnsname=somename.com -ttl=30 -outport=6262 -inport=2626 -bindaddr=10.0.0.1

so that all packets arriving on port 2626 of 10.0.0.1 will be forwarded to port 6262 on the hosts that are pointed by the somename.com record. Since the ttl is set to 30 seconds, the somename.com record will be re-resolved every 30 seconds and the list of addresses updated accordingly.

The goroutines that resolve the dns record and that send the data are mutually excluded via sync.Mutex so there is the guarantee that the set of ips that are used as destinations will be consistent between resolves.

Must have some bugs, pull requests and issues welcome!