Two nodes with IP address yet only one CNAME

I tried to recreate the problem in a test but everything seems fine: http://paste.ubuntu.com/1268870/.

I think we need to investigate how the config-writing tasks were dispatched/executed: this will add some useful debugging: http://paste.ubuntu.com/1268873/

The problem seems to be related to the -200 address' lease being expired. The cause of this expired lease is still undetermined.

It is perfectly valid for a lease to expire (while a host is down).

Also I don't think it had expired when I saw the problem, it only expired after I let rvb ssh into my test box.

I have some more data. Poking into the leases file shows for one host:

host 10.0.0.200 {
  dynamic;
  hardware ethernet e4:11:5b:13:8f:74;
  fixed-address 10.0.0.200;
}

lease 10.0.0.200 {
  starts 2 2012/10/09 05:19:48;
  ends 2 2012/10/09 09:25:10; # ← this time has passed
  tstp 2 2012/10/09 09:25:10;
  cltt 2 2012/10/09 05:19:48;
  binding state free;
  hardware ethernet e4:11:5b:13:8f:74;
}

IOW, the lease has expired but the DHCPD doesn't care, it happily re-assigns the same IP to that MAC even though the expired lease is kept around. I restarted the DHCPD and this expired lease stays in the leases file.

I think this is because we successfully poked in a host map. I need to re-read what effect this is having in the server.

I am reasonably convinced that the presence of the host map makes the DHCP server hold the expired lease in the config forever. This is going to confuse the lease parsing code quite badly. The fix is to make it look for host maps and consider whether they exist when deciding that a lease is really expired.

A "host" block in the leases file looks, for our purposes, just like a "lease" block without an expiry date. Which is effectively what it is to us. That could be very easy to arrange in the parser (though ordering won't be quite as simple as it was) but next we'll want to know what a deleted host entry looks like.

Found it: for a deleted host entry, the last-written "host" block with that address will have the "deleted" statement inside:

host 10.0.0.200 {
    deleted;
}