On 15/09/2022 15:28, Franky Van Liedekerke wrote: Hi Franky,
So the process restarts to serve freshly updated zones? Is there any
Yes, kind of. The master creates new child processes, which have the old zone data in them. These child processes apply the updates to their in-memory copy of the zones, and then take over serving zones from the previous processes.
reason to that logic? Because it is indeed a server that serves more than 7000 zones with the real masters indeed updating their zones regularly, and restarting a dns process because a zone was updated is a very costly step ...
Well, there are different ways to apply updates to existing zones, and the NSD developers chose this one (fork new child processes to apply the update). Other name servers like BIND and Knot DNS do things differently.
I agree with you that it's not the most efficient way to do things. For starters, NSD temporarily causes memory usage to double when applying zone updates. So you either have to provision a server with double the amount of RAM, or play tricks with swap and/or tune the kernel's memory variables (eg. overcommit) to ensure that fork() doesn't fail.
However, this is how NSD works, so if you're using it, then it's good to understand it, and tune your server accordingly.
If you feel that the reloads are too frequent, you can slow them down by adjusting "xfrd-reload-timeout" from the default of 1s to 10s or even higher. This causes the server processes to be restarted less frequently. The consequence is that more updates are batched together, and zone updates will not be visible immediately.
Regards, Anand _______________________________________________ nsd-users mailing list nsd-users@lists.nlnetlabs.nl https://lists.nlnetlabs.nl/mailman/listinfo/nsd-users
