HTableMultiplexer provides a thread-safe non blocking PUT API across all the tables.
Each put will be sharded into different buffer queues based on its destination region server.
So each region server buffer queue will only have the puts which share the same destination.
And each queue will have a flush worker thread to flush the puts request to the region server.
If any queue is full, the HTableMultiplexer starts to drop the Put requests for that
Also all the puts will be retried as a configuration number before dropping.
And the HTableMultiplexer can report the number of buffered requests and the number of the
failed (dropped) requests in total or on per region server basis.
This class is thread safe.