On Mon, Mar 16, 2020 at 08:31:17PM -0500, Sasha Litvak wrote: > I couldn't find a specific answer anywhere so hopefully someone has a > clue on this list > > We are using dnsmasq on our servers as a caching dns solution. > > Most of our domains are resolved by a wildcard record like this > > $TTL 3600 ; 1 hour > A 10.10.10.23 > $ORIGIN example.net. > * CNAME excontainers > excontainers CNAME exservice.service.consul > > dnsmasq handles resolution of .consul domain directly but the DNS > server itself also forwards .consul to consul servers. > > I added min-ttl 5s to decrease the number of queries to consul > > So when I do dig foo.example.net @127.0.0.1 I get > > foo.example.net. 3600 IN CNAME excontainers.example.net. > excontainers.example.net. 3600 IN CNAME exservice.service.consul. > exservice.service.consul. 5 IN A 10.0.48.13 > > Now we often need to migrate subdomains by pointing them to a > different consul cluster. So our script uses nsupdate and creates a > dynamic DNS record resulting in this reply > > foo.example.net. 60 IN CNAME exservice2.service.consul. > exservice2.service.consul. 5 IN A 10.0.48.35 > > So we have a record that is more explicit and it takes precedence over > wild card. On servers with little traffic, domain switch happens > within a few seconds, but on the main busy server with 100s of queries > a second, it takes an hour for dnsmasq to change its cache. We see > dnsmasq sending requests to the DNS server getting correct new records > but still sending the old cached records to a client. > > When we are going back from distinct to default wild card (removing > distinct record in DNS) cache change happens almost immediately (a > couple of seconds) regardless of how busy the server is. > > Sorry for the long description but I would like to find out a reason > why during switching from wild card to more explicit record dnsmasq > cache update takes such a long time.
$ host -t ns org org name server d0.org.afilias-nst.org. org name server b2.org.afilias-nst.org. org name server a0.org.afilias-nst.info. org name server a2.org.afilias-nst.info. org name server b0.org.afilias-nst.org. org name server c0.org.afilias-nst.info. $ host -t ns consul Host consul not found: 3(NXDOMAIN) $ _______________________________________________ Dnsmasq-discuss mailing list Dnsmasq-discuss@lists.thekelleys.org.uk http://lists.thekelleys.org.uk/mailman/listinfo/dnsmasq-discuss