[2.5] dhcpd.conf domain-name-servers has incorrect ip after removing hardcoded dns on subnet

[Andres Rodriguez]

I have a MAAS that has 4 maas machines all in the same subnet:

2 region/racks
2 racks controllers

maas00 - 10.90.90.1
node01 - 10.90.90.3
node02 - 10.90.90.4
node03 - 10.90.90.5

I have enabled DHCP in the subnet, and selected maas00 as the primary for DHCP. I've overridden the Subnet configuration with 10.90.90.3 as the DNS.

However, when I remove the override of 10.90.90.3 as the DNS for subnet 10.90.90.0/24, the configuration doesn't get automatically updated and the wrong DNS is in the config

[Andres Rodriguez (andreserl)]

This could be an issue that the trigger is not working, or that MAAS is not correctly updating the dhcpd config.

[Andres Rodriguez (andreserl)]

I had to manually restart rackd to update the config

[Blake Rouse (blake-rouse)]

Did a lot of testing of this to ensure that the behavior I am seeing is correct. Seems that this bug is actually related to the other bugs fixed with DHCPD. The trigger do exist for this change, setting and unsetting the domain-name-servers on the subnet does update the DHCP config.

I did see the original behavior where it didn't change, but after 30 seconds the timeout kicks in and it was updated. So the work to ensure this keeps work has fixed this problem. But more work could be done to ensure this is faster, instead of the 30 second timeout and retry.