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https://issues.apache.org/jira/browse/HBASE-18477?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16141628#comment-16141628
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Ashish Singhi edited comment on HBASE-18477 at 8/25/17 1:42 PM:
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The second version of doc looks fine to me, but still some things are not clear 
to me like,
1. All the clusters are live so the client can query any of the read-replica 
cluster also ? If yes then how the client decides which cluster to connect ? 
2. How can we identify whether the cluster is a primary cluster or a read only 
cluster ?
bq. All attempts to write will throw an exception.
3. How will be this handled ?


was (Author: ashish singhi):
The second version of doc looks fine to me, but still I find some things are 
not clear to me like,
All the clusters are live so the client can query any of the read-replica 
cluster also ? If yes then how the client decides which cluster to connect ? 
How can we identify whether the cluster is a primary cluster or a read only 
cluster ?
bq. All attempts to write will throw an exception.
How will be this handled ?

> Umbrella JIRA for HBase Read Replica clusters
> ---------------------------------------------
>
>                 Key: HBASE-18477
>                 URL: https://issues.apache.org/jira/browse/HBASE-18477
>             Project: HBase
>          Issue Type: New Feature
>            Reporter: Zach York
>            Assignee: Zach York
>         Attachments: HBase Read-Replica Clusters Scope doc.docx, HBase 
> Read-Replica Clusters Scope doc.pdf, HBase Read-Replica Clusters Scope 
> doc_v2.docx
>
>
> Recently, changes (such as HBASE-17437) have unblocked HBase to run with a 
> root directory external to the cluster (such as in Amazon S3). This means 
> that the data is stored outside of the cluster and can be accessible after 
> the cluster has been terminated. One use case that is often asked about is 
> pointing multiple clusters to one root directory (sharing the data) to have 
> read resiliency in the case of a cluster failure.
>  
> This JIRA is an umbrella JIRA to contain all the tasks necessary to create a 
> read-replica HBase cluster that is pointed at the same root directory.
>  
> This requires making the Read-Replica cluster Read-Only (no metadata 
> operation or data operations).
> Separating the hbase:meta table for each cluster (Otherwise HBase gets 
> confused with multiple clusters trying to update the meta table with their ip 
> addresses)
> Adding refresh functionality for the meta table to ensure new metadata is 
> picked up on the read replica cluster.
> Adding refresh functionality for HFiles for a given table to ensure new data 
> is picked up on the read replica cluster.
>  
> This can be used with any existing cluster that is backed by an external 
> filesystem.
>  
> Please note that this feature is still quite manual (with the potential for 
> automation later).
>  
> More information on this particular feature can be found here: 
> https://aws.amazon.com/blogs/big-data/setting-up-read-replica-clusters-with-hbase-on-amazon-s3/



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