* New statistic names in StoreStatisticNames
(for joint use with s3a committers)
* Improvements to IOStatistics implementation classes
* RateLimiting wrapper to guava RateLimiter
* S3A committer Tasks moved over as TaskPool and
added support for RemoteIterator
* JsonSerialization.load() to fail fast if source does not exist
+ tests.
This commit is a prerequisite for the main MAPREDUCE-7341 Manifest Committer
patch.
Contributed by Steve Loughran
Change-Id: Ia92e2ab5083ac3d8d3d713a4d9cb3e9e0278f654