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https://issues.apache.org/jira/browse/HDFS-9250?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14964218#comment-14964218
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Andrew Wang commented on HDFS-9250:
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LGTM, thanks Xiao. I'll update the summary and commit this.
> LocatedBlock#addCachedLoc may throw ArrayStoreException when cache is empty
> ---------------------------------------------------------------------------
>
> Key: HDFS-9250
> URL: https://issues.apache.org/jira/browse/HDFS-9250
> Project: Hadoop HDFS
> Issue Type: Bug
> Components: HDFS
> Reporter: Xiao Chen
> Assignee: Xiao Chen
> Attachments: HDFS-9250.001.patch, HDFS-9250.002.patch
>
>
> We may see the following exception:
> {noformat}
> java.lang.ArrayStoreException
> at java.util.ArrayList.toArray(ArrayList.java:389)
> at
> org.apache.hadoop.hdfs.protocol.LocatedBlock.addCachedLoc(LocatedBlock.java:205)
> at
> org.apache.hadoop.hdfs.server.namenode.CacheManager.setCachedLocations(CacheManager.java:907)
> at
> org.apache.hadoop.hdfs.server.namenode.FSNamesystem.getBlockLocationsUpdateTimes(FSNamesystem.java:1974)
> at
> org.apache.hadoop.hdfs.server.namenode.FSNamesystem.getBlockLocationsInt(FSNamesystem.java:1873)
> {noformat}
> The cause is that in LocatedBlock.java, when {{addCachedLoc}}:
> - Passed in parameter {{loc}}, which is type {{DatanodeDescriptor}}, is added
> to {{cachedList}}
> - {{cachedList}} was assigned to {{EMPTY_LOCS}}, which is type
> {{DatanodeInfoWithStorage}}.
> Both {{DatanodeDescriptor}} and {{DatanodeInfoWithStorage}} are subclasses of
> {{DatanodeInfo}} but do not inherit from each other, resulting in the
> ArrayStoreException.
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