[jira] [Resolved] (HDFS-8992) Balancer throws NPE

["He Xiaoqiao (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/HDFS-8992?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

He Xiaoqiao resolved HDFS-8992.
-------------------------------
    Resolution: Duplicate

> Balancer throws NPE
> -------------------
>
>                 Key: HDFS-8992
>                 URL: https://issues.apache.org/jira/browse/HDFS-8992
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: balancer & mover
>    Affects Versions: 2.4.1
>            Reporter: He Xiaoqiao
>
> Balancer may throw NPE because the following {{if Statements}} at line 709 of Balancer.java
> {code:java|firstline=705}
>           synchronized (block) {
>             // update locations
>             for (String datanodeUuid : blk.getDatanodeUuids()) {
>               final BalancerDatanode d = datanodeMap.get(datanodeUuid);
>               if (datanode != null) { // not an unknown datanode
>                 block.addLocation(d);
>               }
>             }
>           }
> {code}
> Before moving block, Balancer divides into two step to get all DNs info & some blocks of DN from NN. Regarding one DN commission after {{getDatanodeReport}} then {{getBlockList}} and one block's target is above DN just right, It will throw NPE when dispatcher.



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