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Posted to hdfs-issues@hadoop.apache.org by "xuzq (Jira)" <ji...@apache.org> on 2020/01/13 15:35:00 UTC

[jira] [Comment Edited] (HDFS-15115) Namenode crash caused by NPE in BlockPlacementPolicyDefault when dynamically change logger to debug

    [ https://issues.apache.org/jira/browse/HDFS-15115?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17014415#comment-17014415 ] 

xuzq edited comment on HDFS-15115 at 1/13/20 3:34 PM:
------------------------------------------------------

Thanks [~weichiu], -HDFS-11827- not solve the problem thoroughly.

The following code will also throw NPE, and the bug still exist.

 
{code:java}
if (LOG.isDebugEnabled()) {
  // it will be used, because i set the LOG level from INFO to DEBUG by LogLevel.
  builder.append("\nNode ").append(NodeBase.getPath(chosenNode))
      .append(" [");
}
{code}
 


was (Author: xuzq_zander):
Thanks [~weichiu], [HDFS-11827|https://issues.apache.org/jira/browse/HDFS-11827] not solve the problem thoroughly.

The following code will also throw NPE, and the bug still exist.

 
{code:java}
if (LOG.isDebugEnabled()) {
  // it will be used, because i set the LOG level from INFO to DEBUG by LogLevel.
  builder.append("\nNode ").append(NodeBase.getPath(chosenNode))
      .append(" [");
}
{code}
 

> Namenode crash caused by NPE in BlockPlacementPolicyDefault when dynamically change logger to debug
> ---------------------------------------------------------------------------------------------------
>
>                 Key: HDFS-15115
>                 URL: https://issues.apache.org/jira/browse/HDFS-15115
>             Project: Hadoop HDFS
>          Issue Type: Bug
>            Reporter: wangzhixiang
>            Priority: Major
>         Attachments: HDFS-15115.001.patch
>
>
> To get debug info, we dynamically change the logger of BlockPlacementPolicyDefault to debug when namenode is running. However, the Namenode crashs. From the log, we find some NPE in BlockPlacementPolicyDefault.chooseRandom. Because *StringBuilder builder* will be used 4 times in BlockPlacementPolicyDefault.chooseRandom method. While the *builder* only initializes in the first time of this method. If we change the logger of BlockPlacementPolicyDefault to debug after the part, the *builder* in remaining part is *NULL* and cause *NPE*



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