@Override
    public Void call() {
      if (this.sink.isStopped()) {
        return null;
      }
      switch (taskType) {
        case READ:
          return read();
        case WRITE:
          return write();
        default:
          return read();
      }
    }
Run a single Region Task and then exit. For each column family of the Region, get one row and
output latency or failure.
hbase-server/src/main/java/org/apache/hadoop/hbase/tool/CanaryTool.java