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Apache Hadoop 2.6.5 Release Notes

These release notes cover new developer and user-facing incompatibilities, important issues, features, and major improvements.

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• HADOOP-12805 | Major | Annotate CanUnbuffer with @InterfaceAudience.Public

Made CanBuffer interface public for use in client applications.

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• MAPREDUCE-6622 | Critical | Add capability to set JHS job cache to a task-based limit

Two recommendations for the mapreduce.jobhistory.loadedtasks.cache.size property:

1. For every 100k of cache size, set the heap size of the Job History Server to 1.2GB. For example, mapreduce.jobhistory.loadedtasks.cache.size=500000, heap size=6GB.
2. Make sure that the cache size is larger than the number of tasks required for the largest job run on the cluster. It might be a good idea to set the value slightly higher (say, 20%) in order to allow for job size growth.

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• YARN-4785 | Major | inconsistent value type of the "type" field for LeafQueueInfo in response of RM REST API - cluster/scheduler

Fix inconsistent value type ( String and Array ) of the "type" field for LeafQueueInfo in response of RM REST API