Github user srdo commented on the issue:
https://github.com/apache/storm/pull/1919
@XuMingmin You shouldn't assume that `KafkaConsumer.close` is called when
crashing. If the executor running the spout crashes (or throws an uncaught
Exception), `close` is not called as far as I know. If the spout is reassigned
to another worker, Storm will just `kill -9` the JVM running the spout. I'm not
sure `ISpout.close` is actually ever called in a non-local cluster. See
https://storm.apache.org/releases/0.9.7/javadocs/backtype/storm/spout/ISpout.html#close--
If you need real at-most-once, the spout would probably need to commit
offsets after every ack.
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