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https://issues.apache.org/jira/browse/HDFS-4942?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Suresh Srinivas updated HDFS-4942:
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    Attachment: HDFSRetryCache.pdf

Here is the early version of the design document. Still pending is the analysis 
of all the Namenode RPC requests. I will post that soon.

Given that we plan on adding a unique identifier  to every RPC request, should 
we get this change done before 2.1.0-beta rc2 is built? This way 2.1.0-beta 
clients can utilize retry cache as well.
                
> Add retry cache support in Namenode
> -----------------------------------
>
>                 Key: HDFS-4942
>                 URL: https://issues.apache.org/jira/browse/HDFS-4942
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>          Components: ha, namenode
>            Reporter: Suresh Srinivas
>            Assignee: Suresh Srinivas
>         Attachments: HDFSRetryCache.pdf
>
>
> In current HA mechanism with FailoverProxyProvider and non HA setups with 
> RetryProxy retry a request from the RPC layer. If the retried request has 
> already been processed at the namenode, the subsequent attempts fail for 
> non-idempotent operations such as  create, append, delete, rename etc. This 
> will cause application failures during HA failover, network issues etc.
> This jira proposes adding retry cache at the namenode to handle these 
> failures. More details in the comments.

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