On Mon, 22 May 2023 18:54:06 GMT, Sergey Bylokhov <s...@openjdk.org> wrote:
>> 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 refr... > > 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 src/java.base/share/classes/java/net/InetAddress.java line 225: > 223: * <p> > 224: * A value of 0 (zero) or if the property is not set means do not use > stale > 225: * names, the negative value is ignored. Suggestion: * names. Negative values are ignored. src/java.base/share/classes/java/net/doc-files/net-properties.html line 276: > 274: preferable to use a stale name rather than result of unsuccessful name > lookup. > 275: A value of 0 (zero) or if the property is not set means do not use stale > 276: names, the negative value is ignored. I'd suggest to rephrase: Suggestion: A value of 0 (zero) or if the property is not set means do not use stale names. Negative values are ignored. src/java.base/share/classes/java/net/doc-files/net-properties.html line 277: > 275: A value of 0 (zero) or if the property is not set means do not use stale > 276: names, the negative value is ignored. > 277: The default value is implementation-specific.</P> Maybe we should say that the default value is 0 since this is what is documented in `java.security` src/java.base/share/conf/security/java.security line 366: > 364: # zero: do not use stale names > 365: # > 366: # default value is never (NEVER). Suggestion: # any positive value: the number of seconds to use the stale names # zero: do not use stale names # negative values are ignored # # default value is 0 (NEVER). ------------- PR Review Comment: https://git.openjdk.org/jdk/pull/13285#discussion_r1209308636 PR Review Comment: https://git.openjdk.org/jdk/pull/13285#discussion_r1209303760 PR Review Comment: https://git.openjdk.org/jdk/pull/13285#discussion_r1209307516 PR Review Comment: https://git.openjdk.org/jdk/pull/13285#discussion_r1209306126
