Kafka KStreams - how to add threads / using StreamsConfig.NUM_STREAM_THREADS_CONFIG
<p>I was messing about with this param and ran into some oddness. My app runs ok without it but when I added this line to the config:</p>
<pre><code> config.put(StreamsConfig.NUM_STREAM_THREADS_CONFIG, &quot;3&quot;);
</code></pre>
<p>CPU usage wouldn't climb above zero. App didn't appear to be doing <em>anything</em>. No errors.</p>
<p>Is there some advised method to increasing thread usage for a KStreams app? Or just 'trust the force' and let it all run together?</p>
<hr />
<h2>Edit:</h2>
<ol>
<li>I have two partitions</li>
<li>Have checked the consumer lag via <code>kafka-consumer-groups</code> - lots of records available</li>
<li>Even if there were only 1 partition - why would having multiple threads <em>do nothing</em>? 0% CPU.</li>
</ol>