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https://issues.apache.org/jira/browse/HDFS-16890?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17694113#comment-17694113
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ASF GitHub Bot commented on HDFS-16890:
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omalley merged PR #5298:
URL: https://github.com/apache/hadoop/pull/5298




> RBF: Add period state refresh to keep router state near active namenode's
> -------------------------------------------------------------------------
>
>                 Key: HDFS-16890
>                 URL: https://issues.apache.org/jira/browse/HDFS-16890
>             Project: Hadoop HDFS
>          Issue Type: Task
>            Reporter: Simbarashe Dzinamarira
>            Assignee: Simbarashe Dzinamarira
>            Priority: Major
>              Labels: pull-request-available
>
> When using the ObserverReadProxyProvider, clients can set 
> *dfs.client.failover.observer.auto-msync-period...* to periodically get the 
> Active namenode's state. When using routers without the 
> ObserverReadProxyProvider, this periodic update is lost.
> In a busy cluster, the Router constantly gets updated with the active 
> namenode's state when
>  # There is a write operation.
>  # There is an operation (read/write) from a new clients.
> However, in the scenario when there are no new clients and no write 
> operations, the state kept in the router can lag behind the active's. The 
> router does update its state with responses from the Observer, but the 
> observer may be lagging behind too.
> We should have a periodic refresh in the router to serve a similar role as 
> *dfs.client.failover.observer.auto-msync-period*



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