public Sink getActiveSink() {
    return sink;
  }
Return a CanaryTool.Sink object containing the detailed results of the canary run. The Sink may
not have been created if a Monitor thread is not yet running.
@return the active Sink if one exists, null otherwise.
hbase-server/src/main/java/org/apache/hadoop/hbase/tool/CanaryTool.java