title: Kafka track consumer progress
body: <p>I have one Kafka topic and four consumer groups.   In each group there can be different numbers of nodes consuming.   Different groups can consume at different rates and some can fall behind, but I want to know if this happens and how far behind.  I want to track how far each group is in consuming the topic.  Can I get the offset in each consumer and write that to metrics.   Or will the offset not be a great indication as it may be different across partitions and I need to do something different.   By the way there will be quite a few partitions. </p>
  
  <p>There are other things I can do but would rather not change the payload to add a counter or timestamp if there is an easier way?</p>
  
  <p>Thanks.</p>