title: Kafka Stream Reducer is not reducing records
body: <p>Below is some sample code where we are trying to remove duplicates based on some record value (in this case id).  When I publish 2 records with the same ID I receive both print statements. I was expecting 1.  I am new to streams, so I am sure I am misunderstanding something.   </p>
  
  <pre><code> kstream.groupBy((key, value) -&gt; value.getId())
                      .reduce((aggValue, newValue) -&gt; aggValue)
                      .toStream()
                      .foreach((key,value) -&gt; {
                          System.out.println(value);
                      })
  </code></pre>