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https://issues.apache.org/jira/browse/KAFKA-12478?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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hudeqi updated KAFKA-12478:
---------------------------
    Description: 
  This problem is exposed in our product environment: a topic is used to 
produce monitoring data. *After expanding partitions, the consumer side of the 
business reported that the data is lost.*

  After preliminary investigation, the lost data is all concentrated in the 
newly expanded partitions. The reason is: when the server expands, the producer 
firstly perceives the expansion, and some data is written in the newly expanded 
partitions. But the consumer group perceives the expansion later, after the 
rebalance is completed, the newly expanded partitions will be consumed from the 
latest if it is set to consume from the latest. Within a period of time, the 
data of the newly expanded partitions is skipped and lost by the consumer.

  If it is not necessarily set to consume from the earliest for a huge data 
flow topic when starts up, this will make the group consume historical data 
from the broker crazily, which will affect the performance of brokers to a 
certain extent. Therefore, *it is necessary to consume these partitions from 
the earliest separately.*

  was:
  This problem is exposed in our product environment: a topic is used to 
produce monitoring data. *After expanding partitions, the consumer side of the 
business reported that the data is lost.*

  After preliminary investigation, the lost data is all concentrated in the 
newly expanded partitions. The reason is: when the server expands, the producer 
firstly perceives the expansion, and some data is written in the newly expanded 
partitions. But the consumer group perceives the expansion later, after the 
rebalance is completed, the newly expanded partitions will be consumed from the 
latest if it is set to consume from the latest. Within a period of time, the 
data of the newly expanded partitions is skipped and lost by the consumer.

  If it is not necessarily set to consume from the earliest for a huge data 
flow topic when starts up, this will make the group consume historical data 
from the broker crazily, which will affect the performance of brokers to a 
certain extent. Therefore, it is necessary to consume these partitions from the 
earliest separately.


> Consumer group may lose data for newly expanded partitions when add 
> partitions for topic if the group is set to consume from the latest
> ---------------------------------------------------------------------------------------------------------------------------------------
>
>                 Key: KAFKA-12478
>                 URL: https://issues.apache.org/jira/browse/KAFKA-12478
>             Project: Kafka
>          Issue Type: Improvement
>          Components: clients
>    Affects Versions: 2.7.0
>            Reporter: hudeqi
>            Priority: Blocker
>              Labels: patch
>   Original Estimate: 1,158h
>  Remaining Estimate: 1,158h
>
>   This problem is exposed in our product environment: a topic is used to 
> produce monitoring data. *After expanding partitions, the consumer side of 
> the business reported that the data is lost.*
>   After preliminary investigation, the lost data is all concentrated in the 
> newly expanded partitions. The reason is: when the server expands, the 
> producer firstly perceives the expansion, and some data is written in the 
> newly expanded partitions. But the consumer group perceives the expansion 
> later, after the rebalance is completed, the newly expanded partitions will 
> be consumed from the latest if it is set to consume from the latest. Within a 
> period of time, the data of the newly expanded partitions is skipped and lost 
> by the consumer.
>   If it is not necessarily set to consume from the earliest for a huge data 
> flow topic when starts up, this will make the group consume historical data 
> from the broker crazily, which will affect the performance of brokers to a 
> certain extent. Therefore, *it is necessary to consume these partitions from 
> the earliest separately.*



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