Hey Mark, I don't think BIND has such a feature, but you'd be better off asking on the BIND users list.
Maybe you could benefit from some kind of script that does "pre-lookups" in advance of the job that runs at the top of each minute. i.e., spend seconds 1-59 doing the lookups slowly so that at second "0" most of the names should be fresh in the cache. DW On Jul 3, 2014, at 2:06 PM, Mark Pettit <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 > https://lists.dns-oarc.net/mailman/listinfo/dns-operations > dns-jobs mailing list > https://lists.dns-oarc.net/mailman/listinfo/dns-jobs
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