smengcl opened a new pull request, #8959: URL: https://github.com/apache/hadoop/pull/8959
Generated-by: Claude Code (Opus 5.5) JIRA: https://issues.apache.org/jira/browse/MAPREDUCE-7552 ### Description of PR Map and reduce task JVMs get `-Djava.net.preferIPv4Stack=true` from the default of `mapreduce.admin.map.child.java.opts` and `mapreduce.admin.reduce.child.java.opts` (`MRJobConfig.DEFAULT_MAPRED_ADMIN_JAVA_OPTS`). Unlike daemons, they do not take this from `HADOOP_OPTS`, so on an IPv6 cluster the tasks keep IPv4 only sockets and fail to connect to IPv6 addresses (`java.nio.channels.UnsupportedAddressTypeException`). Both keys are missing from `mapred-default.xml`, so operators have no documented way to find this. The JIRA proposed removing the pin from the default. That would change task JVM networking on every existing IPv4 cluster, and daemons still default to `-Djava.net.preferIPv4Stack=true` in `hadoop-functions.sh`, so this PR keeps the default and documents the override instead: - Add both keys to `mapred-default.xml` with the current default value (unchanged), and explain that an IPv6 cluster has to remove `-Djava.net.preferIPv4Stack=true` from them. A job can also override it by adding `-Djava.net.preferIPv4Stack=false` to `mapreduce.map.java.opts` / `mapreduce.reduce.java.opts`, since user opts come after admin opts on the command line. ### How was this patch tested? - `TestMapReduceChildJVM` (checks the exact task command line, including the admin opts) and `TestMapreduceConfigFields` pass with the new `mapred-default.xml`, so the value matches the code default exactly. - Doc only, no behavior change. ### For code changes: - [x] Does the title of this PR start with the corresponding JIRA issue id (e.g. 'HADOOP-17799. Your PR title ...')? - [ ] Object storage: Have the integration tests been executed and the endpoint declared according to the connector-specific documentation? - [ ] If adding new dependencies to the code, are these dependencies licensed in a way that is compatible for inclusion under [ASF 2.0](http://www.apache.org/legal/resolved.html#category-a)? - [ ] If applicable, have you updated the `LICENSE`, `LICENSE-binary`, `NOTICE-binary` files? ### AI Tooling - [x] The PR includes the phrase "Contains content generated by Claude Code" where Claude Code is the name of the AI tool used. - [x] My use of AI contributions follows the ASF legal policy https://www.apache.org/legal/generative-tooling.html Contains content generated by Claude Code. 🤖 Generated with [Claude Code](https://claude.com/claude-code) -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected] --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
