[jira] [Commented] (KAFKA-50) kafka intra-cluster replication support

["Sharad Agarwal (Commented) (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/KAFKA-50?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13129584#comment-13129584 ] 

Sharad Agarwal commented on KAFKA-50:
-------------------------------------

Sorry for coming late to this.

I read the design document and it looked like it is quite a complex feature to implement and maintain going forward. The sheer amount of complexity in managing the replicas and partition just bothers me. I am wondering why can't we use HDFS which is hardened over a number of years. Obviously I may be missing some subtle things. Would be great if folks shed light on this.
                
> kafka intra-cluster replication support
> ---------------------------------------
>
>                 Key: KAFKA-50
>                 URL: https://issues.apache.org/jira/browse/KAFKA-50
>             Project: Kafka
>          Issue Type: New Feature
>            Reporter: Jun Rao
>            Assignee: Jun Rao
>             Fix For: 0.8
>
>         Attachments: kafka_replication_highlevel_design.pdf, kafka_replication_lowlevel_design.pdf
>
>
> Currently, Kafka doesn't have replication. Each log segment is stored in a single broker. This limits both the availability and the durability of Kafka. If a broker goes down, all log segments stored on that broker become unavailable to consumers. If a broker dies permanently (e.g., disk failure), all unconsumed data on that node is lost forever. Our goal is to replicate every log segment to multiple broker nodes to improve both the availability and the durability. 
> We'd like to support the following in Kafka replication: 
> 1. Configurable synchronous and asynchronous replication 
> 2. Small unavailable window (e.g., less than 5 seconds) during broker failures 
> 3. Auto recovery when a failed broker rejoins 
> 4. Balanced load when a broker fails (i.e., the load on the failed broker is evenly spread among multiple surviving brokers)

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