[jira] [Commented] (KAFKA-6686) Allow reading topic as KStream and GlobalKTable

["Antony Stubbs (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/KAFKA-6686?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16787856#comment-16787856 ] 

Antony Stubbs commented on KAFKA-6686:
--------------------------------------

Also relates to KAFKA-6646 because if you want both a GTK and a KS from the same topic, instead of KAFKA-6687, you could construct the GTK and then use GTK#toStream...

> Allow reading topic as KStream and GlobalKTable
> -----------------------------------------------
>
>                 Key: KAFKA-6686
>                 URL: https://issues.apache.org/jira/browse/KAFKA-6686
>             Project: Kafka
>          Issue Type: Improvement
>          Components: streams
>            Reporter: Matthias J. Sax
>            Priority: Major
>
> Users often want to read topic multiple times, eg, as a stream and a table. For KSteam/KTable this is possible by reading the data as a KTable, disable caching on the KTable, and get a stream via {{toStream()}}. This pattern does not work for KStream/GlobalKTable though.
> However, there is no need to raise an exception
> {quote}Exception in thread “main” org.apache.kafka.streams.errors.TopologyException: Invalid topology: Topic source has already been registered by another source.
> {quote}
> for this case, because the GlobalKTable is consumer by a different consumer (in contrast to KStream/KTable case for which KStream and KTable use a shared consumer). This fix should also allow to add a topic to a {{Topology}} twice; ie, one as regular and once as global-store topic.



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