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https://issues.apache.org/jira/browse/KAFKA-8328?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17168515#comment-17168515
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ChenLin commented on KAFKA-8328:
--------------------------------

Thanks for your attention, I will re submit the batch to the trunk 
version。[~roncenzhao] [~xilangyan]

> Kafka smooth expansion
> ----------------------
>
>                 Key: KAFKA-8328
>                 URL: https://issues.apache.org/jira/browse/KAFKA-8328
>             Project: Kafka
>          Issue Type: Improvement
>          Components: clients, core
>    Affects Versions: 0.10.2.0
>            Reporter: ChenLin
>            Priority: Major
>              Labels: Kafka, expansion
>             Fix For: 0.10.2.0
>
>         Attachments: DiskUtil.png, Kafka_smooth_expansion.patch, 
> producerP999.png
>
>
> When expanding the kafka cluster, the new follower will read the data from 
> the earliest offset. This can result in a large amount of historical data 
> being read from the disk, putting a lot of pressure on the disk and affecting 
> the performance of the kafka service, for example, the producer write latency 
> will increase. In general, kafka's original expansion mechanism has the 
> following problems:
>            1. The new follower will put a lot of pressure on the disk;
>            2. Causes the producer write latency to increase;
>            3. Causes the consumer read latency to increase;
>         In order to solve these problems, we have proposed a solution for 
> smooth expansion. The main idea of the scheme is that the newly added 
> follower reads data from the HW position, and when the newly added follower 
> reads the data to a certain time threshold or data size threshold, the 
> follower enters the ISR queue. . Since the new follower reads data from the 
> HW location, most of the data read is in the operating system's cache, so it 
> does not put pressure on the disk and does not affect the performance of the 
> kafka service, thus solving the above problems. 
>         In order to illustrate the problems of the original expansion scheme, 
> we have done some tests, and there are corresponding test charts in the 
> attachment.
> !producerP999.png!
> !DiskUtil.png!  
>  



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