We plan to fork the HdrHistogram library.

There are two main reasons behind this choice:

1. We would like to control semantic version and backward compatibility according to our definition. Right now, for instance, TDigest does not match our usage of semantic versioning when changing the library code and that makes upgrading quite challenging because exposes us to backward compatibility issues.
2. We would like to change those libraries to use some specific Elasticsearch libraries/tools/frameworks such as BigArrays. Right now when running some aggregations (percentiles, boxplot,...) we experience OOMs due to large memory usage. Using BigArrays, for instance, would allow us to deal with OOMs using Circuit Breakers.

The immediate goal is just to fork and then later enhance the forked library to make use of big arrays infrastructure.