[jira] [Updated] (HDFS-9250) Add Precondition check to LocatedBlock#addCachedLoc

["Andrew Wang (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/HDFS-9250?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Andrew Wang updated HDFS-9250:
------------------------------
    Summary: Add Precondition check to LocatedBlock#addCachedLoc  (was: LocatedBlock#addCachedLoc may throw ArrayStoreException when cache is empty)

> Add Precondition check to LocatedBlock#addCachedLoc
> ---------------------------------------------------
>
>                 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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