KAFKA-17676: Fix NPE when starting tasks after config topic compaction#21368
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KAFKA-17676: Fix NPE when starting tasks after config topic compaction#21368ayalamark-afk wants to merge 1 commit intoapache:trunkfrom
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…ecovery This commit adds three fixes for the NPE/task failure issues caused when task configs are lost due to connect-configs topic compaction: Fix 1: Leader periodic check for inconsistent connectors (processInconsistentConnectors) - Leader checks configState.inconsistentConnectors() on each tick - Automatically triggers reconfigureConnectorTasksWithRetry() for any connector with incomplete task configs - This proactively recovers connectors before tasks fail to start Fix 2: Auto-recovery in startTask() when task config is missing - Checks if taskConfig is null before attempting to start task - If connector is running, calls requestTaskReconfiguration() to regenerate configs - Throws ConnectException so task will be retried after configs are regenerated - This provides fallback recovery if periodic check misses the issue Fix 3: Proper cleanup in removeConnectorConfig() - When connector is deleted, also tombstone all task configs and commit record - Prevents orphaned task configs that could cause issues when connector is recreated - Original code only tombstoned connector config and target state These fixes ensure Kafka Connect can automatically recover from task config loss due to topic compaction without manual intervention.
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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.