[jira] [Created] (HDFS-16377) Should CheckNotNull before access FsDatasetSpi

["tomscut (Jira)" <ji...@apache.org>]

tomscut created HDFS-16377:
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             Summary: Should CheckNotNull before access FsDatasetSpi
                 Key: HDFS-16377
                 URL: https://issues.apache.org/jira/browse/HDFS-16377
             Project: Hadoop HDFS
          Issue Type: Bug
            Reporter: tomscut
            Assignee: tomscut
         Attachments: image-2021-12-10-19-19-22-957.png, image-2021-12-10-19-20-58-022.png

When starting the DN, we found NPE in the staring DN's log, as follows:

!image-2021-12-10-19-19-22-957.png|width=909,height=126!

The logs of the upstream DN are as follows:

!image-2021-12-10-19-20-58-022.png|width=905,height=239!

This is mainly because *FsDatasetSpi* has not been initialized at the time of access. 

I noticed that checkNotNull is already done in these two method({*}DataNode#getBlockLocalPathInfo{*} and {*}DataNode#getVolumeInfo{*}). So we should add it to other places(interfaces that clients and other DN can access directly) so that we can add a message when throwing exceptions.

Therefore, the client and the upstream DN know that FsDatasetSpi has not been initialized, rather than blindly unaware of the specific cause of the NPE.



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