Sink getSink(Configuration configuration, Class clazz) {
    // In test context, this.sink might be set. Use it if non-null. For testing.
    if (this.sink == null) {
      this.sink = (Sink) ReflectionUtils
        .newInstance(configuration.getClass("hbase.canary.sink.class", clazz, Sink.class));
    }
    return this.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