title: What does consumer LAG mean in Consumer Group
body: <p>I'm observing that Kafka Consumer is inconsistently not able to receive the messages when Producer trying to send it. When i checked kafka consumer , there are LAG values seen :</p>
  
  <pre><code> docker run   --net=host   --rm &lt;docker image&gt; kafka-consumer-groups --zookeeper localhost:2181  --describe --group mgmt_testing
  
  GROUP                          TOPIC    PARTITION   CURRENT-OFFSET  LOG-END-OFFSET    LAG             OWNER
  mgmt_testing          mgmt_testing         0           44              44              0               mgmt_testing_aws-us-east-1-mr3-10-10-8-218-1561090200381-21858516-0
  mgmt_testing          mgmt_testing          1          35              35              0               mgmt_testing_aws-us-east-1-mr3-10-10-8-218-1561090200381-21858516-0
  mgmt_testing          mgmt_testing          2          39              39              0               mgmt_testing_aws-us-east-1-mr3-10-10-8-218-1561090200381-21858516-0
  mgmt_testing          mgmt_testing          3          37              37              0               mgmt_testing_aws-us-east-1-mr3-10-10-8-218-1561090200381-21858516-0
  mgmt_testing          mgmt_testing          4          25              38              13              mgmt_testing_aws-us-east-1-mr3-10-10-8-218-1561090200381-21858516-0
  mgmt_testing          mgmt_testing          5          458             666             208             mgmt_testing_aws-us-east-1-mr3-10-10-8-218-1561090200381-21858516-0
  mgmt_testing          mgmt_testing          6          808167          808181          14              mgmt_testing_aws-us-east-1-mr3-10-10-8-218-1561090200381-21858516-0
  mgmt_testing          mgmt_testing          7          434028          434041          13              mgmt_testing_aws-us-east-1-mr3-10-10-8-218-1561090200381-21858516-0
  </code></pre>
  
  <p>What does LAG mean here ? And will this be the reason that consumer is not able to receive the messages?</p>