@Override
  protected String progressInfo() {
    StringBuilder sb = new StringBuilder();
    appendToStatus(sb, "wroteUpTo", wroteUpToKey.get());
    appendToStatus(sb, "wroteQSize", wroteKeyQueueSize.get());
    return sb.toString();
  }
The max key until which all keys have been inserted/updated (successfully or not).
@return the last key that we have inserted/updated all keys up to (inclusive)
hbase-diagnostics/src/main/java/org/apache/hadoop/hbase/util/MultiThreadedWriterBase.java