DHCP failover - disk full, can not commit to lease file

[Ted Lemon]

On May 28, 2013, at 9:27 AM, Steven Carr <sjcarr at gmail.com> wrote:
> How does the DHCP server know what the cause of the error is and why
> would it care? all it knows is that it had an problem writing to the
> lease file which could be caused by any number of issues not just a
> full disk. DHCP failover isn't mean't to guard against your server
> running into problems, it's there to failover in the event of
> communications failure between the network and one of the DHCP
> servers.

Failover is there to allow one server to continue operating when the other fails, whether that's from a full disk or a network outage.   In cases where the server can detect that it has failed, for whatever reason, it's entirely appropriate for it to indicate to its peer that it is no longer able to serve leases, and there's a provision for that in the failover protocol.

It doesn't matter whether the server failed to write the lease because the disk was full or because of a hardware or permission error: what matters is that the server definitely can't make progress until something changes.   Gracefully handling this state in a failover peering environment is clearly in scope for failover.   Sure, the server could punt, and indeed when I wrote the code that you are seeing the problem with, I never got around to adding this feature.   But that was because I had other code I needed to write, not because I thought it was a bad idea.