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https://issues.apache.org/jira/browse/HDFS-15900?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17303572#comment-17303572
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Akira Ajisaka commented on HDFS-15900:
--------------------------------------
Thanks [~hdaikoku] for your report and analysis. [~hdaikoku] and I did more
analysis:
In
https://github.com/apache/hadoop/blob/rel/release-3.3.0/hadoop-hdfs-project/hadoop-hdfs-rbf/src/main/java/org/apache/hadoop/hdfs/server/federation/store/impl/MembershipStoreImpl.java#L219-L221,
we expect the federationSpaceInfo of both AVAILABLE and UNAVAILABLE NameNodes
are set in {{activeNamespaces}}, however, the hashCode method of
{{FederationNamespaceInfo}} is incorrect and {{activeNamespaces}} actually only
contains the first record in a nameservice and the latter records are ignored
in TreeSet. Therefore if the first record is of UNAVAILABLE NameNode, only
UNAVAILABLE NameNode will exist in {{activeNamespaces}} and the block pool id
becomes empty.
Possible fixes:
1. As he commented, we should ignore UNAVAILABLE NameNode registrations.
2. Add missing hashCode and equal methods. (Follow the well-known best practice)
Either of the two is sufficient to fix this issue. However, I think it's better
to do both.
> RBF: empty blockpool id on dfsrouter caused by UNAVAILABLE NameNode
> -------------------------------------------------------------------
>
> Key: HDFS-15900
> URL: https://issues.apache.org/jira/browse/HDFS-15900
> Project: Hadoop HDFS
> Issue Type: Bug
> Components: rbf
> Affects Versions: 3.3.0
> Reporter: Harunobu Daikoku
> Priority: Major
> Attachments: image.png
>
>
> We observed that when a NameNode becomes UNAVAILABLE, the corresponding
> blockpool id in MembershipStoreImpl#activeNamespaces on dfsrouter
> unintentionally sets to empty, its initial value.
> !image.png|height=250!
> As a result of this, concat operations through dfsrouter fail with the
> following error as it cannot resolve the block id in the recognized active
> namespaces.
> {noformat}
> Caused by:
> org.apache.hadoop.ipc.RemoteException(org.apache.hadoop.ipc.RemoteException):
> Cannot locate a nameservice for block pool BP-...
> {noformat}
> A possible fix is to ignore UNAVAILABLE NameNode registrations, and set
> proper namespace information obtained from available NameNode registrations
> when constructing the cache of active namespaces.
>
> [https://github.com/apache/hadoop/blob/rel/release-3.3.0/hadoop-hdfs-project/hadoop-hdfs-rbf/src/main/java/org/apache/hadoop/hdfs/server/federation/store/impl/MembershipStoreImpl.java#L207-L221]
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