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Posted to common-issues@hadoop.apache.org by GitBox <gi...@apache.org> on 2022/01/10 01:53:36 UTC
[GitHub] [hadoop] tomscut edited a comment on pull request #3839: HDFS-16402. HeartbeatManager may cause incorrect stats
tomscut edited a comment on pull request #3839:
URL: https://github.com/apache/hadoop/pull/3839#issuecomment-1008483869
> It's good catch here. Would you mind to add new test to cover this case? BTW, what is the root cause about NPE here? Thanks.
Thanks @Hexiaoqiao for your review and comments.
The main reason is that the `DatanodeDescriptor#storageMap` cannot find the storage that DN reports through `lifeline`. As a result, the `NPE` is thrown in line 460 of the code when the storage is operated. It is similar to the situation encountered in this issue [HDFS-14042](https://issues.apache.org/jira/browse/HDFS-14042).
Here is the scenario we encountered:
1 We add a disk to datanode and reconfig `dfs.datanode.data.dir`.
2 After a while, many values on NN's Web become negative.
3 We found the NPE from the NN log and discovered this issue [HDFS-14042](https://issues.apache.org/jira/browse/HDFS-14042).
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