KAFKA-17676: Fix NPE when starting tasks after config topic compaction #21368
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This commit includes two fixes for NPE issues caused by config topic compaction: Fix 1: Only update connectorTaskCounts when we actually apply task configs - Moves connectorTaskCounts.put() inside the else block - Prevents advertising task count without having configs for all tasks - Handles incomplete task set scenario due to compaction Fix 2: Handle compacted connector configs gracefully - Distinguish between deleted connector vs compacted config - Recover from previously applied config if available - Mark as inconsistent if recovery not possible Both fixes are needed to fully address NPE crashes when starting tasks after the connect-configs topic has been compacted.
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Summary
Fix for KAFKA-17676 - NullPointerException when starting tasks after the connect-configs topic has been compacted.
Problem
When the connect-configs topic gets compacted, two scenarios can cause NPE crashes:
Incomplete task configs due to compaction: Task config records get compacted leaving an incomplete set, but
connectorTaskCountsis still updated, causing NPE when trying to start tasks without configs.Missing connector config: Connector config records can be removed by compaction even though the connector is still active. The fix for KAFKA-16838 assumes that if a connector config is missing, the connector was deleted, and ignores task configs. This causes an NPE when trying to start tasks:
java.lang.NullPointerException: Cannot invoke "java.util.Map.size()" because "inputMap" is null
at org.apache.kafka.connect.runtime.TaskConfig.
at org.apache.kafka.connect.runtime.Worker.startTask
Solution
Two fixes in
processTasksCommitRecord:Fix 1: Only update
connectorTaskCountswhen we actually apply task configsconnectorTaskCounts.put()inside the else blockFix 2: Handle compacted connector configs gracefully
Both fixes are needed to fully address NPE crashes when starting tasks after config topic compaction.