title: Does Spark Streaming provide a guarantee on the order of the date when reducing
body: <p>I was wondering if when calling reduceByKey in apache spark streaming the order of the records in the stream were guarantied. Basically part of the computation I do has to get the last value. </p>
  
  <p>Here's an example:</p>
  
  <pre><code>JavaPairDStream&lt; String, Double &gt;  pairs; // ...
  pairs.reduceByKey( new Function2&lt;Double, Double, Double&gt;() { 
              @Override public Double call(Double first, Double second) throws Exception { 
                  return second;
              } 
          });
  </code></pre>