Hi, I mentioned at the dnsop talk at IETF88 yesterday that I have some (hopefully) useful information regarding W.C.A. Wijngaards' prefetch work.
At OpenDNS, we implemented the same thing some months ago (without knowing about this work) with the following differences: - Our HAMMER_TIME is set to 3 seconds - Our STOP is hardwired as HAMMER_TIME + 1 We saw similar non-results in our graphs - at ~50 billion queries per day, prefetch didn't change anything.... However, there were two other issues addressed: - Under normal circumstances, when a record expires, all clients querying that record suffer (unnecessary) latency while the record is being re-queried upstream. Fixing this was a convenient benefit. - Because our resolvers run multiple threads sharing the same cache, previously, a popular record expiration would tend to result in an upstream query from *each* thread. This was the issue we wanted to address. You could argue that our implementation should be clever enough to piggy-back the upstream queries from different threads (one query, multiple clients on multiple threads waiting for the response), but having the threads interact/contend against eachother for more than just cache lookups/updates is undesirable at higher loads. -- Brian Somers bsom...@opendns.com
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