title: SCDF on k8s: Producer exception when sending message to Kafka - ticktock + no messages on ticktock.time topic
body: <p>The timer application throws a per-second error when trying to send its message to <em>Kafka</em>:</p>
  
  <pre><code>2017-08-03 10:20:58,805 ERROR kafka-producer-network-thread | producer-2 o.s.k.s.LoggingProducerListener:76 - Exception thrown when sending a message with key='null' and payload='{-1, 2, 11, 99, 111, 110, 116, 101, 110, 116, 84, 121, 112, 101, 0, 0, 0, 12, 34, 116, 101, 120, 116...' to topic metrics: org.apache.kafka.common.errors.TimeoutException: Expiring 2 record(s) for metrics-0 due to 30009 ms has passed since batch creation plus linger time
  </code></pre>
  
  <p>It seems to me like these would be the records for the metrics topic, but at the same time there are no records in the ticktock.timer topic in <em>Kafka</em>.
  I'm guessing this partition key being null could be the problem. But I am not so sure why it should use some partitioning setup that is not the default one.</p>
  
  <p>Here's what I deployed:</p>
  
  <pre><code>dataflow:&gt; app register --type sink --name log --uri docker://springcloudstream/log-sink-kafka-10:1.2.0.RELEASE --metadata-uri maven://org.springframework.cloud.stream.app:log-sink-kafka-10:jar:metadata:1.2.0.RELEASE dataflow:&gt; app register --type source --name time --uri docker://springcloudstream/time-source-kafka-10:1.2.0.RELEASE --metadata-uri maven://org.springframework.cloud.stream.app:time-source-kafka-10:jar:metadata:1.2.0.RELEASE dataflow:&gt; stream create --name ticktock --definition "time | log" --deploy
  </code></pre>
  
  <p>And here's my setup:</p>
  
  <pre><code>spring-cloud-dataflow-server-kubernetes: 1.3.0.BUILD-SNAPSHOT
  Spring Cloud Data Flow Core: 1.3.0.BUILD-SNAPSHOT
  Spring Cloud Dataflow UI: 1.3.0.BUILD-SNAPSHOT
  </code></pre>
  
  <p>I'm using <em>Kafka 10</em> BTW.</p>
  
  <p>What could be the problem?</p>
  
  <p>Many thanks for your support!</p>