kfake: bump group epoch on topic change to ensure assignment resend#1259
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kfake: bump group epoch on topic change to ensure assignment resend#1259
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When a topic is created/deleted/partitioned, notifyTopicChange eagerly recomputes target assignments but did not bump g.generation. If the heartbeat response carrying the new assignment arrived before the client discovered the topic ID via metadata, the client skipped the unknown topic. The server recorded lastReconciledSent as delivered and never resent the assignment on subsequent keepalive heartbeats, permanently missing the topic. Fix by bumping g.generation in notifyTopicChange (matching Kafka, which bumps the group epoch on target assignment changes) and resending the assignment while memberEpoch < generation. The member epoch only catches up when currentAssignment == targetAssignment, confirming the client processed the assignment. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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When a topic is created/deleted/partitioned, notifyTopicChange eagerly recomputes target assignments but did not bump g.generation. If the heartbeat response carrying the new assignment arrived before the client discovered the topic ID via metadata, the client skipped the unknown topic. The server recorded lastReconciledSent as delivered and never resent the assignment on subsequent keepalive heartbeats, permanently missing the topic.
Fix by bumping g.generation in notifyTopicChange (matching Kafka, which bumps the group epoch on target assignment changes) and resending the assignment while memberEpoch < generation. The member epoch only catches up when currentAssignment == targetAssignment, confirming the client processed the assignment.