Rabit tracker configurations.
The timeout for all workers to connect to the tracker. Set timeout length to zero to disable timeout. Use a finite, non-zero timeout value to prevent tracker from hanging indefinitely (in milliseconds) (supported by "scala" implementation only.)
Choice between "python" or "scala". The former utilizes the Java wrapper of the Python Rabit tracker (in dmlc_core), whereas the latter is implemented in Scala without Python components, and with full support of timeouts. The Scala implementation is currently experimental, use at your own risk.