title: Prevent Kafka broker from closing idle connection
body: <p>In my case, my producer uses librdkafka, <code>topic.metadata.refresh.interval.ms</code> is by default 5mins. 
  On broker side <code>connections.max.idle.ms</code> is 2 hours, we have pretty low qps, but We want 99.9% of request within rtt 20ms, but if the broker close the connection, the producer will re-establish the channel and send the message, which will get a high latency. It seems the metadata refresh won't work. </p>
  
  <p>How do I address this problem?</p>