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https://issues.apache.org/jira/browse/HDFS-15533?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Uma Maheswara Rao G resolved HDFS-15533.
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Fix Version/s: 3.4.0
Hadoop Flags: Reviewed
Resolution: Fixed
I have just committed this to trunk. Thanks [~ayushtkn] for reviews!
> Provide DFS API compatible class, but use ViewFileSystemOverloadScheme inside
> -----------------------------------------------------------------------------
>
> Key: HDFS-15533
> URL: https://issues.apache.org/jira/browse/HDFS-15533
> Project: Hadoop HDFS
> Issue Type: Sub-task
> Components: dfs, viewfs
> Affects Versions: 3.4.0
> Reporter: Uma Maheswara Rao G
> Assignee: Uma Maheswara Rao G
> Priority: Major
> Fix For: 3.4.0
>
>
> I have been working on a thought from last week is that, we wanted to provide
> DFS compatible APIs with mount functionality. So, that existing DFS
> applications can work with out class cast issues.
> When we tested with other components like Hive and HBase, I noticed some
> classcast issues.
> {code:java}
> HBase example:
> java.lang.ClassCastException:
> org.apache.hadoop.fs.viewfs.ViewFileSystemOverloadScheme cannot be cast to
> org.apache.hadoop.hdfs.DistributedFileSystemjava.lang.ClassCastException:
> org.apache.hadoop.fs.viewfs.ViewFileSystemOverloadScheme cannot be cast to
> org.apache.hadoop.hdfs.DistributedFileSystem at
> org.apache.hadoop.hbase.util.FSUtils.getDFSHedgedReadMetrics(FSUtils.java:1748)
> at
> org.apache.hadoop.hbase.regionserver.MetricsRegionServerWrapperImpl.<init>(MetricsRegionServerWrapperImpl.java:146)
> at
> org.apache.hadoop.hbase.regionserver.HRegionServer.handleReportForDutyResponse(HRegionServer.java:1594)
> at
> org.apache.hadoop.hbase.regionserver.HRegionServer.run(HRegionServer.java:1001)
> at java.lang.Thread.run(Thread.java:748){code}
> {code:java}
> Hive:
> |io.AcidUtils|: Failed to get files with ID; using regular API: Only
> supported for DFS; got class
> org.apache.hadoop.fs.viewfs.ViewFileSystemOverloadScheme{code}
> SO, here the implementation details are like follows:
> We extended DistributedFileSystem and created a class called "
> ViewDistributedFileSystem"
> This vfs=ViewFirstibutedFileSystem, try to initialize
> ViewFileSystemOverloadScheme. If success call will delegate to vfs. If fails
> to initialize due to no mount points, or other errors, it will just fallback
> to regular DFS init. If users does not configure any mount, system will
> behave exactly like today's DFS. If there are mount points, vfs functionality
> will come under DFS.
> I have a patch and will post it in some time.
>
>
>
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