KAFKA-20268: Initialize group epochs to 1 for assignment offload#21700
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dajac merged 5 commits intoapache:trunkfrom Mar 11, 2026
Merged
KAFKA-20268: Initialize group epochs to 1 for assignment offload#21700dajac merged 5 commits intoapache:trunkfrom
dajac merged 5 commits intoapache:trunkfrom
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Once assignment offload is implemented, newly created groups may not have their first assignment at epoch 1 available yet. We cannot give the member an epoch of 0, since it is reserved for new members joining a group. The new member's epoch must be greater than 0 and less than the group epoch. To resolve this, we initialize groups at epoch 1 with target assignment epoch 1. Epoch 1 contains an empty assignment and the first computed assignment will have epoch 2. Members joining a new group will reconcile towards epoch 1 while waiting for epoch 2's assignment. Streams groups already start group epochs at 2. We update streams groups to use the same approach as consumer and share groups.
dajac
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Mar 10, 2026
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@squah-confluent Thanks for the PR. I left a few minor comments.
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| this.assignmentEpoch = 1; | ||
| this.assignmentTimestamp = 0L; |
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Should we use TargetAssignmentMetadata.INITIAL to init those two?
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That's a good idea, yes.
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| this.assignmentEpoch = 1; | ||
| this.assignmentTimestamp = 0L; |
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| this.targetAssignmentEpoch = 1; | ||
| this.targetAssignmentTimestamp = 0L; |
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| // The group epoch is bumped. | ||
| GroupCoordinatorRecordHelpers.newConsumerGroupEpochRecord(groupId, 1, 0), | ||
| // The target assignment is created. | ||
| GroupCoordinatorRecordHelpers.newConsumerGroupTargetAssignmentRecord(groupId, memberId1, Map.of()), | ||
| GroupCoordinatorRecordHelpers.newConsumerGroupTargetAssignmentMetadataRecord(groupId, 1, context.time.milliseconds()), |
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Let's replace those with a comment explaining why there are not here.
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Added a comment
…epoch and timestamp in group builders
…ItBeforeResolutionCompleted
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@squah-confluent Could you check the failed tests? They seem to be related. |
lucasbru
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This is a nice improvement, cleaner than the previous logic. Thanks, LGTM!
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CI on trunk is broken again. I opened a fix at #21707. |
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Once assignment offload is implemented, newly created groups may not
have their first assignment at epoch 1 available yet. We cannot give the
member an epoch of 0, since it is reserved for new members joining a
group. The new member's epoch must be greater than 0 and less than the
group epoch.
To resolve this, we initialize groups at epoch 1 with target assignment
epoch 1. Epoch 1 contains an empty assignment and the first computed
assignment will have epoch 2. Members joining a new group will reconcile
towards epoch 1 while waiting for epoch 2's assignment.
Streams groups already start group epochs at 2. We update streams groups
to use the same approach as consumer and share groups.
Reviewers: Lucas Brutschy lbrutschy@confluent.io, David Jacot
djacot@confluent.io