Github user srdo commented on a diff in the pull request: https://github.com/apache/storm/pull/1696#discussion_r79992419 --- Diff: external/storm-kafka-client/src/main/java/org/apache/storm/kafka/spout/KafkaSpout.java --- @@ -145,6 +154,10 @@ private void initialize(Collection<TopicPartition> partitions) { } retryService.retainAll(partitions); + + //Emitted messages for partitions that are no longer assigned to this spout can't be acked, and they shouldn't be retried. Remove them from emitted. + Set<TopicPartition> partitionsSet = new HashSet(partitions); + emitted.removeIf((msgId) -> !partitionsSet.contains(msgId.getTopicPartition())); --- End diff -- The messages should be getting removed from retryService in line 156. It's my impression that onPartitionsAssigned will be getting called immediately after onPartitionsRevoked, before the current call to poll returns (see https://kafka.apache.org/090/javadoc/org/apache/kafka/clients/consumer/ConsumerRebalanceListener.html).
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