title: Kafka MirrorMaker2 - not mirroring consumer group offsets
body: <p>I have setup MirrorMaker2 for replicating data between 2 DC's. </p>
  
  <p>My mm2.properties,</p>
  
  <pre><code># mm2.properties
  name=source-&gt;dest
  clusters=source, dest
  
  source.bootstrap.servers=localhost:9091
  dest.bootstrap.servers=localhost:9092
  
  source-&gt;dest.enabled=true
  
  offset.storage.partitions=2
  config.storage.replication.factor=1
  status.storage.replication.factor=1
  </code></pre>
  
  <p>Seeing the below on MM2 startup.</p>
  
  <pre><code>[2020-02-16 07:31:07,547] INFO MirrorConnectorConfig values: 
      admin.timeout.ms = 60000
      checkpoints.topic.replication.factor = 3
      config.action.reload = restart
      config.properties.blacklist = [follower\.replication\.throttled\.replicas, leader\.replication\.throttled\.replicas, message\.timestamp\.difference\.max\.ms, message\.timestamp\.type, unclean\.leader\.election\.enable, min\.insync\.replicas]
      config.property.filter.class = class org.apache.kafka.connect.mirror.DefaultConfigPropertyFilter
      connector.class = org.apache.kafka.connect.mirror.MirrorCheckpointConnector
      consumer.poll.timeout.ms = 1000
      emit.checkpoints.enabled = true
      emit.checkpoints.interval.seconds = 60
      emit.heartbeats.enabled = true
      emit.heartbeats.interval.seconds = 1
      enabled = true
      errors.log.enable = false
      errors.log.include.messages = false
      errors.retry.delay.max.ms = 60000
      errors.retry.timeout = 0
      errors.tolerance = none
      group.filter.class = class org.apache.kafka.connect.mirror.DefaultGroupFilter
      groups = [.*]
      groups.blacklist = [console-consumer-.*, connect-.*, __.*]
      header.converter = null
      heartbeats.topic.replication.factor = 3
      key.converter = null
      metric.reporters = null
      name = source-&gt;dest
      offset-syncs.topic.replication.factor = 3
      offset.lag.max = 100
      refresh.groups.enabled = true
      refresh.groups.interval.seconds = 600
      refresh.topics.enabled = true
      refresh.topics.interval.seconds = 600
      replication.factor = 2
      replication.policy.class = class org.apache.kafka.connect.mirror.DefaultReplicationPolicy
      replication.policy.separator = .
      sasl.client.callback.handler.class = null
      sasl.jaas.config = null
      sasl.kerberos.kinit.cmd = /usr/bin/kinit
      sasl.kerberos.min.time.before.relogin = 60000
      sasl.kerberos.service.name = null
      sasl.kerberos.ticket.renew.jitter = 0.05
      sasl.kerberos.ticket.renew.window.factor = 0.8
      sasl.login.callback.handler.class = null
      sasl.login.class = null
      sasl.login.refresh.buffer.seconds = 300
      sasl.login.refresh.min.period.seconds = 60
      sasl.login.refresh.window.factor = 0.8
      sasl.login.refresh.window.jitter = 0.05
      sasl.mechanism = GSSAPI
      security.protocol = PLAINTEXT
      source.cluster.alias = source
      ssl.cipher.suites = null
      ssl.enabled.protocols = [TLSv1.2, TLSv1.1, TLSv1]
      ssl.endpoint.identification.algorithm = https
      ssl.key.password = null
      ssl.keymanager.algorithm = SunX509
      ssl.keystore.location = null
      ssl.keystore.password = null
      ssl.keystore.type = JKS
      ssl.protocol = TLS
      ssl.provider = null
      ssl.secure.random.implementation = null
      ssl.trustmanager.algorithm = PKIX
      ssl.truststore.location = null
      ssl.truststore.password = null
      ssl.truststore.type = JKS
      sync.topic.acls.enabled = true
      sync.topic.acls.interval.seconds = 600
      sync.topic.configs.enabled = true
      sync.topic.configs.interval.seconds = 600
      target.cluster.alias = dest
      task.assigned.groups = null
      task.assigned.partitions = null
      tasks.max = 1
      topic.filter.class = class org.apache.kafka.connect.mirror.DefaultTopicFilter
      topics = [.*]
      topics.blacklist = [.*[\-\.]internal, .*\.replica, __.*]
      transforms = []
      value.converter = null
   (org.apache.kafka.connect.mirror.MirrorConnectorConfig:347)
  </code></pre>
  
  <p>My data is being replicated as expected. Source topic gets created in the destination cluster as source.. But, the consumer group offset is not being replicated.</p>
  
  <p>Started a consumer group in the source cluster.</p>
  
  <pre><code>./kafka-console-consumer.sh --bootstrap-server localhost:9091 --topic test-1 --group test-1-group
  </code></pre>
  
  <p>Consumed few messages and stopped it. Posted new messages in this topic and mirror maker also mirrored the data to the target cluster. </p>
  
  <p>I tried to consume message from the target cluster as follows.</p>
  
  <pre><code>./kafka-console-consumer.sh --bootstrap-server localhost:9092 --topic source.test-1 --group test-1-group
  </code></pre>
  
  <p>Since, I use the same consumer group, I was expecting my offset also to be synced and wont consume the same message which I consumed in the cluster1. But, still consume all the messages. Is there anything I am missing here.</p>