This PR has:
- been self-reviewed.
- concurrent read
- concurrent write
- concurrent read and write
- added documentation for new or modified features or behaviors.
- added Javadocs for most classes and all non-trivial methods.
- added or updated version, license, or notice information
- added comments explaining the "why" and the intent of the code wherever would not be obvious for an unfamiliar reader.
- added unit tests or modified existing tests to cover new code paths, ensuring the threshold for code coverage.
- added integration tests.
- been tested in a test IoTDB cluster.