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https://issues.apache.org/jira/browse/STORM-2896?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16320817#comment-16320817
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Stig Rohde Døssing commented on STORM-2896:
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I'm happy to work on implementing this, but it probably won't be for a while so
if anyone else is up for it please take the issue.
> Support automatic migration of offsets from storm-kafka to storm-kafka-client
> KafkaSpout
> ----------------------------------------------------------------------------------------
>
> Key: STORM-2896
> URL: https://issues.apache.org/jira/browse/STORM-2896
> Project: Apache Storm
> Issue Type: Improvement
> Components: storm-kafka-client
> Affects Versions: 2.0.0, 1.2.0
> Reporter: Stig Rohde Døssing
>
> I think we can ease migration for people looking to move from storm-kafka to
> storm-kafka-client. We should be able to support migrating offsets from the
> old spout by setting some extra configuration in KafkaSpoutConfig, and by
> adding a new FirstPollOffsetStrategy (e.g. something like
> FirstPollOffsetStrategy.UNCOMMITTED_MIGRATE_FROM_STORM_KAFKA).
> The old spout stores offsets in Storm's Zookeeper at one of two paths. The
> storm-kafka SpoutConfig has two parameters we'll also need, namely zkRoot and
> id. In addition we need to know if the storm-kafka subscription was a
> wildcard subscription or not.
> The zookeeper path for commit info is
> {code}
> zkRoot + "/" + id + "/" + topicName + "partition_" + partition
> {code}
> if the subscription was a wildcard. Otherwise it is
> {code}
> zkRoot + "/" + id + "/" + "partition_" + partition
> {code}
> We can get topicName and partition numbers from the KafkaConsumer.assignment.
> When we run initialize, we should be able to read the old offset structure
> from Zookeeper when the strategy is UNCOMMITTED_MIGRATE_FROM_STORM_KAFKA, and
> seek the consumer to those offsets. We can just crash if the offsets are not
> present.
> I'd be okay with this feature not being permanent, but I think this feature
> would make it a lot easier for people to move off the old spout.
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