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https://issues.apache.org/jira/browse/HDFS-10289?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Vinod Kumar Vavilapalli updated HDFS-10289:
-------------------------------------------
    Target Version/s:   (was: 2.8.0)

Not much going on here for a while, dropping from 2.8.0.

Not putting any target-version either anymore, let's target this depending on 
when there is patch activity.

> Balancer configures DNs directly
> --------------------------------
>
>                 Key: HDFS-10289
>                 URL: https://issues.apache.org/jira/browse/HDFS-10289
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>          Components: balancer & mover
>    Affects Versions: 2.6.0
>            Reporter: John Zhuge
>            Assignee: John Zhuge
>            Priority: Critical
>
> Balancer directly configures the 2 balance-related properties 
> (bandwidthPerSec and concurrentMoves) on the DNs involved.
> Details:
> * Before each balancing iteration, set the properties on all DNs involved in 
> the current iteration.
> * The DN property changes will not survive restart.
> * Balancer gets the property values from command line or its config file.
> * Need new DN APIs to query and set the 2 properties.
> * No need to edit the config file on each DN or run {{hdfs dfsadmin 
> -setBalancerBandwidth}} to configure every DN in the cluster.
> Pros:
> * Improve ease of use because all configurations are done at one place, the 
> balancer. We saw many customers often forgot to set concurrentMoves properly 
> since it is required on both DN and Balancer.
> * Support new DNs added between iterations
> * Handle DN restarts between iterations
> * May be able to dynamically adjust the thresholds in different iterations. 
> Don't know how useful though.
> Cons:
> * New DN property API
> * A malicious/misconfigured balancer may overwhelm DNs. {{hdfs dfsadmin 
> -setBalancerBandwidth}} has the same issue. Also Balancer can only be run by 
> admin.
> Questions:
> * Can we create {{BalancerConcurrentMovesCommand}} similar to 
> {{BalancerBandwidthCommand}}? Can Balancer use them directly without going 
> through NN?
> One proposal to implement HDFS-7466 calls for an API to query DN properties. 
> DN Conf Servlet returns all config properties. It does not return individual 
> property and it does not return the value set by {{hdfs dfsadmin 
> -setBalancerBandwidth}}.



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