The TeraGrid operates two high-availability central MDS4 services that
downstream MDS4 services register to using info1-up and
info2-up.dyn.teragrid.org.  If either of these servers had a catastrophic
failure we could bring up the central MDS4 services on an alternate host and
update the info1-up or info2-up dynamic DNS entries with global internet
propagation in 15 minutes.

Unfortunately, it appears that our downstream MDS4 services resolve the
info1-up and info2-up hostnames used to register upstream into an IP addresses
at startup and never again.  In support of high-availability services it would
be helpful if MDS4 services, or their container, periodically expired DNS name
to IP address mappings.