> I would like to get preliminary feedback about the provided patch. > > Discussion on net-dev@ > https://mail.openjdk.org/pipermail/net-dev/2023-March/020682.html > > One of the main issue I try to solve is how the cache handle the intermittent > DNS server outages due to overloading or network connection. > > At the moment this cache can be configured by the application using the > following two properties: > (1) "networkaddress.cache.ttl"(30 sec) - cache policy for successful > lookups > (2) "networkaddress.cache.negative.ttl"(10 sec) - cache policy for > negative lookups > > The default timeout for positive responses is good enough to "have recent > dns-records" and to "minimize the number of requests to the DNS server". > > But the cache for the negative responses is problematic. This is a problem I > would like to solve. Caching the negative response means that for **10** > seconds the application will not be able to connect to the server. > > Possible solutions: > 1. Decreasing timeout "for the negative responses": unfortunately more > requests to the server at the moment of "DNS-outage" cause even more issues, > since this is not the right moment to load the network/server more. > 2. Increasing timeout "for the positive responses": this will decrease the > chance to get an error, but the cache will start to use stale data longer. > 3. This proposal: it would be good to ignore the negative response and > continue to use the result of the last "successful lookup" until some > additional timeout. > > The idea is to split the notion of the TTL and the timeout used for the > cache. When TTL for the record will expire we should request the new data > from the server. If this request goes fine we will update the record, if it > fails we will continue to use the cached date until the next sync. > > For example, if the new property "networkaddress.cache.extended.ttl" is set > to 10 minutes, then we will cache a positive response for 10 minutes but will > try to sync it every 30 seconds. If the new property is not set then as > before we will cache positive for 30 seconds and then cache the negative > response for 10 seconds. > > > RFC 8767 Serving Stale Data to Improve DNS Resiliency: > https://www.rfc-editor.org/rfc/rfc8767 > > Comments about current and other possible implementations: > * The code intentionally moved to the separate ValidAddresses class, just to > make clear that the default configuration, when the new property is not set > is not changed much. > * The refresh timeout includes the time s...
Sergey Bylokhov has updated the pull request incrementally with one additional commit since the last revision: if the property is not set means do not use stale names ------------- Changes: - all: https://git.openjdk.org/jdk/pull/13285/files - new: https://git.openjdk.org/jdk/pull/13285/files/a856cd36..ce595f74 Webrevs: - full: https://webrevs.openjdk.org/?repo=jdk&pr=13285&range=10 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=13285&range=09-10 Stats: 4 lines in 2 files changed: 1 ins; 0 del; 3 mod Patch: https://git.openjdk.org/jdk/pull/13285.diff Fetch: git fetch https://git.openjdk.org/jdk.git pull/13285/head:pull/13285 PR: https://git.openjdk.org/jdk/pull/13285
