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https://issues.apache.org/jira/browse/HADOOP-5933?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12714027#action_12714027
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Steve Loughran commented on HADOOP-5933:
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Some options
# if the log is at debug level, generate an exception in close() and save it
until the next checkOpen() call is reached -and use that exception as the
nested cause of the exception that is raised there.
# some complicated reference count mechanism with its own leakage problems
# add the ability to reopen things if they were in cache and got purged.
I've done the first one of these to track down problems, and while I now know
where I shouldn't be calling close(), there's a risk that my code will now leak
filesystem clients.
> Make it harder to accidentally close a shared DFSClient
> -------------------------------------------------------
>
> Key: HADOOP-5933
> URL: https://issues.apache.org/jira/browse/HADOOP-5933
> Project: Hadoop Core
> Issue Type: Improvement
> Components: fs
> Affects Versions: 0.21.0
> Reporter: Steve Loughran
> Priority: Minor
>
> Every so often I get stack traces telling me that DFSClient is closed,
> usually in {{org.apache.hadoop.hdfs.DFSClient.checkOpen() }} . The root cause
> of this is usually that one thread has closed a shared fsclient while another
> thread still has a reference to it. If the other thread then asks for a new
> client it will get one -and the cache repopulated- but if has one already,
> then I get to see a stack trace.
> It's effectively a race condition between clients in different threads.
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