title: Kafka streams listening to multiple topics hangs
body: <p>I'm working with the kafka streams api and am running into issues where I subscribe to multiple topics and the consumer just hangs. It has a unique <code>application.id</code> and I can see in kafka that the consumer group has been created, but when I describe the group, I'll get: <code>consumer group X has no active members</code>. I've left it running for close to an hour.</p>
  
  <p>The interesting thing is that this works when the <code>topics</code> list only contains 1 topic. I'm not interested in other answers where we create multiple sources, ie: <code>source1 = builder.stream("topic1")</code> and <code>source2 = builder.stream("topic2")</code> as the interface for <code>StreamsBuilder.stream</code> supports an array of topics.</p>
  
  <p>I've been able to subscribe to multiple topics before, I just can't replicate how we've done this. (This code is running in a different environment and working as expected, so not sure if it's a timing issue or something else)</p>
  
  <pre><code>List&lt;String&gt; topics = Arrays.asList("topic1", "topic2");
  
  StreamsBuilder builder = new StreamsBuilder();
  KStream&lt;String, String&gt; source = builder.stream(topics);
  
  source
  .transformValues(...)
  .map(key, value) -&gt; ...)
  .to((key, value, record) -&gt; ...);
  
  new KafkaStreams(builder.build(), props).start();
  </code></pre>
  
  <p><strong>UPDATE 06/18/19</strong>
  After enabling logs, it was clear that we were trying to subscribe &amp; publish to topics that did not exist. While we had <code>auto.topic.create.enable=true</code> it didn't matter. So ultimately had a check on startup that would cause the script to exit if all the topics weren't created beforehand since we weren't creating topics dynamically.</p>