Github user arunmahadevan commented on a diff in the pull request:
https://github.com/apache/storm/pull/2147#discussion_r119444961
--- Diff:
external/storm-kafka-client/src/main/java/org/apache/storm/kafka/spout/KafkaSpout.java
---
@@ -170,10 +182,13 @@ private void initialize(Collection<TopicPartition>
partitions) {
final long fetchOffset = doSeek(tp, committedOffset);
setAcked(tp, fetchOffset);
}
- initialized = true;
+
+ task.start();
--- End diff --
https://kafka.apache.org/0102/javadoc/org/apache/kafka/clients/consumer/ConsumerRebalanceListener.html#onPartitionsRevoked(java.util.Collection)
It appears that offsets can be committed to either kafka or externally in
`onPartitionsRevoked`. So the spout can wait to receive the acks for in-flight
messages before committing the offsets to reduce duplicates.
>I think it would be a nicer solution to eliminate most rebalances by
switching to manual partition assignment
Yes, switching to manual assignment where each task gets a fixed subset of
partitions would eliminate the re-balance completely. If we can get that out
quickly well and good, but I think it may require a re-design of the current
logic, meanwhile this patch can put some band-aid on whatever already exists in
production.
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