docs(review): minor updates to mm2 config #12273

PaulRMellor · 2025-12-22T17:51:50Z

Documentation

Minor updates to the MM2 config docs following review

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Please go through this checklist and make sure all applicable tasks have been done

Write tests
Make sure all tests pass
Update documentation
Check RBAC rights for Kubernetes / OpenShift roles
Try your changes from Pod inside your Kubernetes and OpenShift cluster, not just locally
Reference relevant issue(s) and close them after merging
Update CHANGELOG.md
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Signed-off-by: prmellor <[email protected]>

Copilot

Pull request overview

This PR refines the MirrorMaker 2 documentation to improve clarity, consistency, and technical precision following a review. The changes focus on better explaining configuration concepts, improving readability, and providing more accurate descriptions of MirrorMaker 2 behavior.

Clarifies configuration paths and terminology (e.g., "connector configuration" vs "MirrorMaker 2 configuration")
Expands explanations of Kafka Connect worker settings and internal topics
Improves wording and formatting for better readability across multiple configuration sections

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 7 comments.

Show a summary per file

File	Description
`con-mm2-recovery.adoc`	Updates disaster recovery documentation, removes trailing spaces and clarifies that `IdentityReplicationPolicy` is set in connector configuration
`con-config-mm2-multiple-instances.adoc`	Expands explanation of Kafka Connect worker settings and internal topics, clarifies when unique configurations are needed
`con-config-mirrormaker2-sync.adoc`	Simplifies wording about offset sync topic location and Java utility usage
`con-config-mirrormaker2-sync-acls.adoc`	Improves clarity of ACL synchronization behavior description
`con-config-mirrormaker2-producers-consumers.adoc`	Refines producer/consumer descriptions and adjusts table column widths; simplifies configuration paths
`con-config-mirrormaker2-connect-workers.adoc`	Enhances explanation of Kafka Connect worker behavior and adds inline comments to example configuration

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Copilot · 2025-12-22T17:54:23Z

documentation/modules/configuring/con-config-mirrormaker2-producers-consumers.adoc

-|Loads the `offset-syncs` topic.
-|mirrors.checkpointConnector.config: consumer.*
+|Consumes data from the `offset-syncs` topic.
+|`consumer.*`


The configuration path is incomplete. This should include the full path context showing it goes under "mirrors.checkpointConnector.config" section.

Copilot · 2025-12-22T17:54:23Z

documentation/modules/configuring/con-mm2-recovery.adoc

+. Deploy a new MirrorMaker 2 instance to replicate data from the active recovery cluster to the rebuilt cluster. 
 Treat the rebuilt cluster as the passive cluster during this replication process.
-To prevent automatic renaming of topics, configure MirrorMaker 2 to use the `IdentityReplicationPolicy` by setting the `replication.policy.class` property in the MirrorMaker 2 configuration.
+To prevent automatic renaming of topics, configure MirrorMaker 2 to use the `IdentityReplicationPolicy` by setting the `replication.policy.class` property in the connector configuration.


The change from "MirrorMaker 2 configuration" to "connector configuration" is more precise, but the sentence should clarify which connector. The IdentityReplicationPolicy is set on the MirrorSourceConnector specifically. Consider specifying "MirrorSourceConnector configuration" for clarity, as MirrorMaker 2 has multiple connector types (MirrorSourceConnector, MirrorCheckpointConnector, MirrorHeartbeatConnector).

Suggested change

To prevent automatic renaming of topics, configure MirrorMaker 2 to use the `IdentityReplicationPolicy` by setting the `replication.policy.class` property in the connector configuration.

To prevent automatic renaming of topics, configure MirrorMaker 2 to use the `IdentityReplicationPolicy` by setting the `replication.policy.class` property in the MirrorSourceConnector configuration.

Copilot · 2025-12-22T17:54:23Z

documentation/modules/configuring/con-config-mm2-multiple-instances.adoc


-Multiple instances attempting to use the same internal topics will cause unexpected errors, so you must change the values of these properties for each instance.
+* Multiple MirrorMaker 2 instances use the same source Kafka cluster but different target Kafka clusters
+* Deploying active-active replication where each MirrorMaker 2 instance uses a different target Kafka cluster


The second bullet point should include a comma before "where" for better readability. The sentence is a complex clause where the "where" introduces additional descriptive information. It should read: "Deploying active-active replication, where each MirrorMaker 2 instance uses a different target Kafka cluster".

Suggested change

* Deploying active-active replication where each MirrorMaker 2 instance uses a different target Kafka cluster

* Deploying active-active replication, where each MirrorMaker 2 instance uses a different target Kafka cluster

Copilot · 2025-12-22T17:54:24Z

documentation/modules/configuring/con-config-mirrormaker2-producers-consumers.adoc

-|mirrors.sourceConnector.config: producer.override.*
+|Sends replicated topic messages to the target Kafka cluster.
+Tune this producer when handling large volumes of data.
+|`producer.override.*`


The configuration path is incomplete. Based on line 18 which mentions "where you can add configuration" and the context that these are MirrorMaker 2 connector configurations, the path should include the full configuration location. The original text "mirrors.sourceConnector.config: producer.override." provided context showing where to place this configuration. The new format only shows "producer.override." without indicating this goes under "mirrors.sourceConnector.config" section.

Copilot · 2025-12-22T17:54:24Z

documentation/modules/configuring/con-config-mirrormaker2-producers-consumers.adoc

-|Writes to the `offset-syncs` topic, which maps the source and target offsets for replicated topic partitions. 
-|mirrors.sourceConnector.config: producer.*
+|Writes to the `offset-syncs` topic, which maps source and target offsets.
+|`producer.*`


The configuration path is incomplete. Similar to the producer.override.* configuration above, this should include the full path context showing it goes under "mirrors.sourceConnector.config" section.

Copilot · 2025-12-22T17:54:24Z

documentation/modules/configuring/con-config-mirrormaker2-producers-consumers.adoc

-|Retrieves topic messages from the source Kafka cluster.
-|mirrors.sourceConnector.config: consumer.* 
+|Consumes topic messages from the source Kafka cluster.
+|`consumer.*`


The configuration path is incomplete. This should include the full path context showing it goes under "mirrors.sourceConnector.config" section.

Copilot · 2025-12-22T17:54:24Z

documentation/modules/configuring/con-config-mirrormaker2-producers-consumers.adoc

-|Emits consumer offset checkpoints.
-|mirrors.checkpointConnector.config: producer.override.* 
+|Emits consumer group offset checkpoints.
+|`producer.override.*`


The configuration path is incomplete. This should include the full path context showing it goes under "mirrors.checkpointConnector.config" section.

codecov · 2025-12-22T18:41:33Z

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 74.80%. Comparing base (e15813d) to head (695f4b9).

Additional details and impacted files

@@             Coverage Diff              @@
##               main   #12273      +/-   ##
============================================
- Coverage     74.81%   74.80%   -0.01%     
  Complexity     6627     6627              
============================================
  Files           376      376              
  Lines         25345    25345              
  Branches       3402     3402              
============================================
- Hits          18962    18960       -2     
- Misses         4995     4996       +1     
- Partials       1388     1389       +1

see 4 files with indirect coverage changes

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scholzj

One nit. LGTM otherwise.

scholzj · 2025-12-23T09:04:10Z

documentation/modules/configuring/con-config-mm2-multiple-instances.adoc

 <4> Kafka topic that stores connector and task status updates.

-NOTE: Values for the three topics must be the same for all instances with the same `group.id`.
+NOTE: All workers that belong to the same Kafka Connect cluster must use the same values for these properties.


I'm not sure this is meaningful as there is now way user can configure it per-worker-node.

It is even more confusing with the two sentences below as users might assume that they can configure multiple MM2s to the same values which is not true.

I would remove this note.

mimaison · 2025-12-27T12:32:40Z

documentation/modules/configuring/con-config-mirrormaker2-sync-acls.adoc


 * ACL rules apply to both source and target topics
-* Users with source topic access automatically get equivalent target topic access
+* Users with access to source topics automatically receive equivalent access to replicated target topics


This is not quite true. MirrorSourceConnector mirror solely topic ACLs and does not mirror the ALLOW WRITE ACL.

mimaison · 2025-12-27T12:38:15Z

documentation/modules/configuring/con-config-mirrormaker2-sync.adoc

+You can change this behavior by setting the `offset-syncs.topic.location` connector configuration to `target`.
+
+Changing the location of the topic allows MirrorMaker 2 to operate when the connector has read-only access to the source cluster.
+In this case, the connector must have read and write access to the target cluster.


This file seems to be about MirrorCheckpointConnector. If so regardless of the location of the offset-sycns topics, this connector should already have read and write access to the checkpoints topic.

docs(review): minor updates to mm2 config

695f4b9

Signed-off-by: prmellor <[email protected]>

PaulRMellor added this to the 0.50.0 milestone Dec 22, 2025

PaulRMellor requested review from a team and mimaison December 22, 2025 17:51

PaulRMellor self-assigned this Dec 22, 2025

Copilot AI review requested due to automatic review settings December 22, 2025 17:51

PaulRMellor added the documentation label Dec 22, 2025

Copilot started reviewing on behalf of PaulRMellor December 22, 2025 17:52 View session

Copilot AI reviewed Dec 22, 2025

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scholzj reviewed Dec 23, 2025

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mimaison reviewed Dec 27, 2025

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	To prevent automatic renaming of topics, configure MirrorMaker 2 to use the `IdentityReplicationPolicy` by setting the `replication.policy.class` property in the connector configuration.
	To prevent automatic renaming of topics, configure MirrorMaker 2 to use the `IdentityReplicationPolicy` by setting the `replication.policy.class` property in the MirrorSourceConnector configuration.

	* Deploying active-active replication where each MirrorMaker 2 instance uses a different target Kafka cluster
	* Deploying active-active replication, where each MirrorMaker 2 instance uses a different target Kafka cluster

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PaulRMellor commented Dec 22, 2025 •

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