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https://issues.apache.org/jira/browse/BEAM-8121?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17091876#comment-17091876
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Chamikara Madhusanka Jayalath commented on BEAM-8121:
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I think there are some users who read from Kafka topics with one partition (or
a very small number of partitions) and are unable to easily increase the number
of partitions of the topic.
For these users, the current solution seems to me simply to use a Reshuffle
after the read step to parallelize subsequent steps.
It might be better to allow parallelizing read step itself by distributing
messages from the same partition among multiple source splits.
> Messages are not distributed per machines when consuming from Kafka topic
> with 1 partition
> ------------------------------------------------------------------------------------------
>
> Key: BEAM-8121
> URL: https://issues.apache.org/jira/browse/BEAM-8121
> Project: Beam
> Issue Type: Bug
> Components: io-java-kafka
> Affects Versions: 2.14.0
> Reporter: TJ
> Assignee: Alexey Romanenko
> Priority: Major
> Fix For: Not applicable
>
> Attachments: datalake-dataflow-cleaned.zip
>
>
> Messages are consumed from Kafka using KafkaIO. Each kafka topic contains
> only 1 partition. (That means that messages can be consumed only by one
> Consumer per 1 consumer group)
> When backlog of topic grows and system scales from 1 to X machines, all the
> messages seems to be executed on the same machine on which they are read.
> Due to that message throughput doesn't increase comparing X machines to 1
> machine. If one machine was reading 2K messages per s, X machines will be
> reading the same amount.
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