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https://issues.apache.org/jira/browse/HDFS-5454?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13848820#comment-13848820
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Junping Du commented on HDFS-5454:
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+1. Patch looks good to me. Thanks for this refactoring. Aript!
> DataNode UUID should be assigned prior to FsDataset initialization
> ------------------------------------------------------------------
>
> Key: HDFS-5454
> URL: https://issues.apache.org/jira/browse/HDFS-5454
> Project: Hadoop HDFS
> Issue Type: Sub-task
> Components: datanode
> Affects Versions: 3.0.0
> Reporter: Eric Sirianni
> Priority: Minor
> Attachments: HDFS-5454.01.patch, HDFS-5454.02.patch,
> HDFS-5454.03.patch
>
>
> The DataNode's UUID ({{DataStorage.getDatanodeUuid()}} field) is NULL at the
> point where the {{FsDataset}} object is created ({{DataNode.initStorage()}}.
> As the {{DataStorage}} object is an input to the {{FsDataset}} factory
> method, it is desirable for it to be fully populated with a UUID at this
> point. In particular, our {{FsDatasetSpi}} implementation relies upon the
> DataNode UUID as a key to access our underlying block storage device.
> This also appears to be a regression compared to Hadoop 1.x - our 1.x
> {{FSDatasetInterface}} plugin has a non-NULL UUID on startup. I haven't
> fully traced through the code, but I suspect this came from the
> {{BPOfferService}}/{{BPServiceActor}} refactoring to support federated
> namenodes.
> With HDFS-5448, the DataNode is now responsible for generating its own UUID.
> This greatly simplifies the fix. Move the UUID check/generation in from
> {{DataNode.createBPRegistration()}} to {{DataNode.initStorage()}}. This more
> naturally co-locates UUID generation immediately subsequent to the read of
> the UUID from the {{DataStorage}} properties file.
> {code}
> private void initStorage(final NamespaceInfo nsInfo) throws IOException {
> // ...
> final String bpid = nsInfo.getBlockPoolID();
> //read storage info, lock data dirs and transition fs state if necessary
> storage.recoverTransitionRead(this, bpid, nsInfo, dataDirs, startOpt);
>
> // SUGGESTED NEW PLACE TO CHECK DATANODE UUID
> checkDatanodeUuid();
> // ...
> }
> {code}
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