Thanks, those are some rather interesting (and one funny) ideas. On Thursday, July 3, 2014, Damian Menscher <dam...@google.com> wrote:
> Rather than address your question, I'm going to argue that the real > problem you should fix is the synchronized lookups. Some ideas for > smoothing it out a bit: > > - Have you considered just turning off NTP? ;) > - Can the servers delay their start time by a random offset (but fixed > for each server) from the top of the minute? > - Can the servers cache the result rather than looking it up so often? > Then you'll be fine as long a they don't get synchronized to the TTL. > > Damian > > > On Thu, Jul 3, 2014 at 2:06 PM, Mark Pettit <m...@pettit.org > <javascript:_e(%7B%7D,'cvml','m...@pettit.org');>> wrote: > >> Hi, folks. >> >> I have an issue with BIND cache timeouts, and I was hoping someone else >> might have some idea how to fix this. >> >> Here's the situation: we have a large number of servers that do a huge >> number of DNS lookups at the top of every minute. The TTL for the records >> they're looking up is 3600. >> >> What we've noticed is that on a host with a recently-restarted copy of >> BIND, we see huge spikes in DNS latency every 61 minutes. This makes >> logical sense, given the behavior of the DNS lookups. >> >> What is more interesting is that on hosts that have been running BIND for >> a very long time (on the order of months), the spikiness is not visible. >> >> Our speculation is that over time, due to the interaction between the >> 3600 TTL and the "once every minute" lookup behavior, cache misses become >> randomly distributed throughout the hour, and don't cause the spiky >> behavior that is observed initially. >> >> One of our ideas to resolve this is to randomize the TTLs in the zone >> files, causing them to expire out of cache at different times, thus forcing >> more-rapid distribution of cache misses across the hour. >> >> However, this would involve some massive edits to our zone files, and >> isn't really ideal. >> >> What *would* be ideal would be if we could tell BIND to randomly expire >> some small percentage of cached entries ahead of the actual TTL expiration. >> This would serve the same purpose as assigning "random" TTLs to the actual >> records in the zone files. >> >> Does BIND have a config option like this? Has anyone else ever >> encountered this issue, and if so, how did you address it? >> >> Thanks for any advice, and I hope everyone has a fantastic Fourth of July >> weekend. >> >> Mark Pettit >> >> >> _______________________________________________ >> dns-operations mailing list >> dns-operations@lists.dns-oarc.net >> <javascript:_e(%7B%7D,'cvml','dns-operations@lists.dns-oarc.net');> >> https://lists.dns-oarc.net/mailman/listinfo/dns-operations >> dns-jobs >> <https://lists.dns-oarc.net/mailman/listinfo/dns-operationsdns-jobs> >> mailing list >> https://lists.dns-oarc.net/mailman/listinfo/dns-jobs >> > >
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