Dynamic updates to multiple masters

[Fred Morris]

You have more than one hypothetical problem there.

On Wed, 2 Aug 2023, Shailendra Gautam wrote:
> I have four authoritative dns servers, all running in master mode for my
> zone for high availability,

Can you give me the justification for why this was chosen and why it works 
in 100 words or less? I expect at least 50 words each for why it was 
chosen, and why it works. Am I bad with math?

Isn't the DNS Way to secondary zones from a master to achieve this?

> I'm
> trying to implement dynamic updates but I am wondering if there is any way
> to avoid sending an update to each of them

Good luck with that!

> Would like to know if anyone has faced this
> problem before.

Don't do that if it hurts... but I'm a plumber not a doctor.

You have multiple engineering problems here. You have eschewed the "DNS 
Solution" for zone management (zone transfers). Now you want to adopt the 
DNS Solution for updates (dynamic updates).

I have engineered a solution which switched masters in the case of 
failover and it wasn't too bad, although it required restarting BIND to 
reload the config file so that nodes would know that one of them was the 
new master. There were dynamic updates, although ironically my 
recollection is that the change in config somehow addressed that (it's 
been a few years).

As for the Dynamic Updates Generally problem, have you looked at 
idempotence as a paradigm? With this idea, updates are applied to converge 
with the "ideal image" that the updater holds; hopefully your updaters 
agree on that image, otherwise you have another problem related to 
conflict resolution (or in the parlance: distributed locking).

It's a wonderful world isn't it?

Anyway, the "way out" for us, even though the scenario was in someways 
different, was idempotence: the updaters would continue to attempt to 
update whatever the master was until it conformed to their ideal image, 
and their ideal image could change in consideration of what the zone held.

--

Fred Morris, internet plumber