Document what happens when target has multiple addresses

[zloo]

Document what happens when target has multiple addresses.

How often do we resolve? What if the IP changes? What if there's multiple addresses? Do we ping all of them, or just the first one?

[SuperQ]

Currently, we resolve once on startup, and only ping one.

[zloo]

ok, and do we want to keep that? we should at least honor the TTL and re-resolve when it expires.

regarding pinging multiple hosts, i think it makes sense to ping all resolved hosts, and we can distinguish between them via a label.

[SuperQ]

I was working on an upstream change to the ping library to adjust the way it resolves. Still waiting for feedback.