Major Description
The two exceptions below were reported by Frank on the dev mailing list. After investigation, the root cause is multiple cache evictions happening in the same topology.
Given a topology like the one below. If a record arriving in `tableOne` causes a cache eviction, it will trigger the `leftJoin` that will do a `get` from `reducer-store`. If the key is not currently cached in `reducer-store`, but is in the backing store, it will be put into the cache, and it may also trigger an eviction. If it does trigger an eviction and the eldest entry is dirty it will flush the dirty keys. It is at this point that the exception in the comment happens (ClassCastException). This occurs because the ProcessorContext is still set to the context of the `leftJoin` and the next child in the topology is `mapValues`.
We need to set the correct `ProcessorNode`, on the context, in the `ForwardingCacheFlushListener` prior to calling `context.forward`. We also need to set remember to reset the `ProcessorNode` to the previous node once `context.forward` has completed.
final KTable<String, String> one = builder.table(Serdes.String(), Serdes.String(), tableOne, tableOne); final KTable<Long, String> two = builder.table(Serdes.Long(), Serdes.String(), tableTwo, tableTwo); final KTable<String, Long> reduce = two.groupBy(new KeyValueMapper<Long, String, KeyValue<String, Long>>() { @Override public KeyValue<String, Long> apply(final Long key, final String value) { return new KeyValue<>(value, key); } }, Serdes.String(), Serdes.Long()) .reduce(new Reducer<Long>() { @Override public Long apply(final Long value1, final Long value2) { return value1 + value2; } }, new Reducer<Long>() { @Override public Long apply(final Long value1, final Long value2) { return value1 - value2; } }, "reducer-store"); one.leftJoin(reduce, new ValueJoiner<String, Long, String>() { @Override public String apply(final String value1, final Long value2) { return value1 + ":" + value2; } }) .mapValues(new ValueMapper<String, String>() { @Override public String apply(final String value) { return value; } });
This exception is actually a symptom of the exception reported below in the comment. After the first exception is thrown, the StreamThread triggers a shutdown that then throws this exception.
[StreamThread-1] ERROR
org.apache.kafka.streams.processor.internals.StreamThread - stream-thread
[StreamThread-1] Failed to close state manager for StreamTask 0_0:
org.apache.kafka.streams.errors.ProcessorStateException: task [0_0] Failed
to close state store addr-organization
at
org.apache.kafka.streams.processor.internals.ProcessorStateManager.close(ProcessorStateManager.java:342)
at
org.apache.kafka.streams.processor.internals.AbstractTask.closeStateManager(AbstractTask.java:121)
at
org.apache.kafka.streams.processor.internals.StreamThread$2.apply(StreamThread.java:341)
at
org.apache.kafka.streams.processor.internals.StreamThread.performOnAllTasks(StreamThread.java:322)
at
org.apache.kafka.streams.processor.internals.StreamThread.closeAllStateManagers(StreamThread.java:338)
at
org.apache.kafka.streams.processor.internals.StreamThread.shutdownTasksAndState(StreamThread.java:299)
at
org.apache.kafka.streams.processor.internals.StreamThread.shutdown(StreamThread.java:262)
at
org.apache.kafka.streams.processor.internals.StreamThread.run(StreamThread.java:245)
Caused by: java.lang.IllegalStateException: Key found in dirty key set, but
entry is null
at
org.apache.kafka.streams.state.internals.NamedCache.flush(NamedCache.java:112)
at
org.apache.kafka.streams.state.internals.ThreadCache.flush(ThreadCache.java:100)
at
org.apache.kafka.streams.state.internals.CachingKeyValueStore.flush(CachingKeyValueStore.java:111)
at
org.apache.kafka.streams.state.internals.CachingKeyValueStore.close(CachingKeyValueStore.java:117)
at
org.apache.kafka.streams.processor.internals.ProcessorStateManager.close(ProcessorStateManager.java:340)
... 7 more
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