[TriLUG] Load balancing DNS servers

[Ron Kelley via TriLUG]

Have to agree on the non load-balanced DNS Server setup.  We are running a similar setup running dnsmasq on a primary and standby server.  To make sure the standby server gets correctly synced, you can use some of the following options:

inotify.  This tool (daemon) can watch a file or directory for changes and run a script when the event happens.  For example, use notify to watch the DHCP leases on dns-1 then rsync the directory to dns-2 (and restart dnsmasq on dns-2)

monit.  Similar to inotify, have the tool watch dhcp server files/directories then run an external rsync script once a change happens (ie: rsync the dnsmasq DHCP lease files)

“lsyncd”.  Again, similar to inotify.  Check out this thread:   https://unix.stackexchange.com/questions/307046/real-time-file-synchronization


-Ron



> On May 3, 2019, at 12:33 PM, John Franklin via TriLUG <trilug at trilug.org> wrote:
> 
> On May 3, 2019, at 10:45, Mauricio Tavares via TriLUG <trilug at trilug.org> wrote:
>> 
>> How would you load balance them so you only have to provide a single
>> IP to the clients? If I were to use a database term, this smells like
>> multimaster replication. If those servers also do DHCP, how would the
>> updates be shared with each node so everyone will be on the same page?
>> What about leases?
> 
> Generally, you don’t load balance DNS.  If you’re running a registry or a massive DNS service (think: 8.8.8.8), then you might build a custom solution with a front-end that fans out to multiple back-end servers or use anycast to stand up servers around the world all with the same IP and let the internet’s routing tables “load balance” for you.  (How much DNS are you doing?)
> 
> For more typical environments where you’re handing out IPs via DHCP (office, home, even single datacenter), you hand out the IPs of one or more DNS servers on the local network in the DHCP response and the clients will cycle through them.  Each of the DNS servers maintain their own cache for non-authoritative lookups and use the normal DNS XFER protocols to push out updates of authoritative zones.
> 
> What are you trying to do?
> 
> jf
> -- 
> John Franklin
> franklin at elfie.org
> -- 
> This message was sent to: Ron Kelley <rkelleyrtp at gmail.com>
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