[jira] [Created] (KAFKA-19607) MirrorMaker2 Offset Replication Issue

["geric (Jira)" <ji...@apache.org>]

geric created KAFKA-19607:
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             Summary: MirrorMaker2 Offset Replication Issue
                 Key: KAFKA-19607
                 URL: https://issues.apache.org/jira/browse/KAFKA-19607
             Project: Kafka
          Issue Type: Bug
          Components: mirrormaker
    Affects Versions: 4.0.0
            Reporter: geric


I am using *Apache Kafka 4.0* with *MirrorMaker 2* to link the primary cluster ({*}clusterA{*}) to the secondary cluster ({*}clusterB{*}).
The secondary cluster will not have any producers or consumers until a disaster recovery event occurs, at which point all producers and consumers will switch to it.

*Setup:*
 * Dedicated standalone MirrorMaker 2 node
 * {{IdentityReplicationPolicy}} (no topic renaming)
 * No clients connected to secondary cluster under normal operation

*MirrorMaker 2 config:*
 {{# Cluster aliases
clusters = clusterA, clusterB

# Bootstrap servers
clusterA.bootstrap.servers = serverA-kafka-1:9092
clusterB.bootstrap.servers = serverB-kafka-1:9092

# Replication policy
replication.policy.class=org.apache.kafka.connect.mirror.IdentityReplicationPolicy

# Offset/Checkpoint sync
emit.checkpoints.enabled=true
emit.checkpoints.interval.seconds=5
sync.group.offsets.enabled=true
sync.group.offsets.interval.seconds=5
offset.lag.max=10
refresh.topics.interval.seconds=5}}
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h3. Test results:
 # *Produce 300 messages when MirrorMaker is running*
*Expected:* Topic offset synced within a minute
*Result:* ✅ Passed

 # *Consume 100 messages when MirrorMaker is running, then terminate the consumer*
*Expected:* Consumer offset synced
*Result:* ❌ Failed — offset is not synced to clusterB

 # *Restart MirrorMaker after test #2*
*Expected:* Consumer offset synced
*Result:* ✅ Passed

 # *Repeat test #2 — consume 100 messages when MirrorMaker is running, then terminate the consumer*
*Expected:* Consumer offset synced
*Result:* ❌ Failed — offset is not synced to clusterB

 # *Restart MirrorMaker after test #4*
*Expected:* Consumer offset synced
*Result:* ❌ Failed — offset is not synced to clusterB

 # *Consume messages but keep consumer running*
*Expected:* Offset synced
*Result:* ✅ Passed

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h3. Problem:

Consumer offsets appear to only sync in these cases:
 # When MirrorMaker is restarted and the consumer offset does *not* already exist in the secondary cluster (initial sync), or
 # When the consumer is still connected at the time of sync, *or* when the consumer has reached the end of the offset (i.e., consumed all available messages).

However, if the consumer exits immediately after consuming some messages (but {*}before reaching the end of the topic{*}), the committed offset is *never synced* to the target cluster.
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h3. Additional Context / Related Issues

This problem seems related to an open discussion in the Apache Kafka mailing list:

*MirrorCheckpointConnector does not replicate final batch of offsets*
[https://lists.apache.org/thread/dxn9jyotl00f7ov541299cd8tlcl1z00]



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