Walker Carlson created KAFKA-12503:
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Summary: Resizing the thread cache in a non thread safe way can
cause records to be redirected throughout the topology
Key: KAFKA-12503
URL: https://issues.apache.org/jira/browse/KAFKA-12503
Project: Kafka
Issue Type: Bug
Components: streams
Affects Versions: 2.8.0
Reporter: Walker Carlson
Fix For: 2.8.0
When a thread is added, removed or replaced the cache is resized. When the
thread cache was resized it was being done so from the thread initiating these
calls. This can cause the record to be redirected to the wrong processor via
the call to `evict` in the cache. The evict flushes records downstream to the
next processor after the cache. But if this is on the wrong thread the wrong
processor receives them.
This can cause 3 problems.
1) When the owner finishes processing the record it set the current node to
null in the processor context a this then causes the other processor to throw
an exception `StreamsException: Current node is unknown.`.
2) Depending on the type it can cause a class cast exception as the record is a
different type. Mostly this happened when the value types were different inside
of the map node from the toStream method
3) A silent issue is it could cause data to be processed by the wrong node and
cause data corruption. We have not been able to confirm this last one but it is
the most dangerous in many ways.
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