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https://issues.apache.org/jira/browse/HDFS-5366?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Colin Patrick McCabe updated HDFS-5366:
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    Description: 
There are a few things about our HDFS-4949 recaching strategy that could be 
improved.

* We should monitor the DN's maximum and current mlock'ed memory consumption 
levels, so that we don't ask the DN to do stuff it can't.

* We should not try to initiate caching on stale or decomissioning DataNodes 
(although we should not recache things stored on such nodes until they're 
declared dead).

* We might want to resend the {{DNA_CACHE}} or {{DNA_UNCACHE}} command a few 
times before giving up.  Currently, we only send it once.

  was:
There are a few things about our HDFS-4949 recaching strategy that could be 
improved.

* We should monitor the DN's maximum and current mlock'ed memory consumption 
levels, so that we don't ask the DN to do stuff it can't.

* We should not try to initiate caching on stale DataNodes (although we should 
not recache things stored on such nodes until they're declared dead).

* We might want to resend the {{DNA_CACHE}} or {{DNA_UNCACHE}} command a few 
times before giving up.  Currently, we only send it once.


> recaching improvements
> ----------------------
>
>                 Key: HDFS-5366
>                 URL: https://issues.apache.org/jira/browse/HDFS-5366
>             Project: Hadoop HDFS
>          Issue Type: Sub-task
>          Components: namenode
>    Affects Versions: HDFS-4949
>            Reporter: Colin Patrick McCabe
>            Assignee: Colin Patrick McCabe
>
> There are a few things about our HDFS-4949 recaching strategy that could be 
> improved.
> * We should monitor the DN's maximum and current mlock'ed memory consumption 
> levels, so that we don't ask the DN to do stuff it can't.
> * We should not try to initiate caching on stale or decomissioning DataNodes 
> (although we should not recache things stored on such nodes until they're 
> declared dead).
> * We might want to resend the {{DNA_CACHE}} or {{DNA_UNCACHE}} command a few 
> times before giving up.  Currently, we only send it once.



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