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https://issues.apache.org/jira/browse/HADOOP-3818?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12617184#action_12617184
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Steve Loughran commented on HADOOP-3818:
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in SmartFrog we had fun with Sun JVM signal handling, which provides extra
compatibility problems with the clean-room OSS implementations and are pretty
hard to test.
Maybe the classname of the class to run as a filesystem hook could be
configurable, so someoneone could subclass and extend its shutdown code, rather
than run race condition pain in shutdown. Which, for anyone who has tried, is
essentially non-debuggable and therefore to be feared.
> Not possible to access a FileSystem from within a ShutdownHook
> --------------------------------------------------------------
>
> Key: HADOOP-3818
> URL: https://issues.apache.org/jira/browse/HADOOP-3818
> Project: Hadoop Core
> Issue Type: Bug
> Components: fs
> Affects Versions: 0.17.1
> Reporter: Rowan Nairn
> Priority: Minor
>
> FileSystem uses addShutdownHook to close all FileSystems at exit. This makes
> it impossible to access a FileSystem from within your own ShutdownHook
> threads, say for deleting incomplete output. Using a pre-existing FileSystem
> object is unsafe since it may be closed by the time the thread executes.
> Using FileSystem.get(...) results in an exception:
> Exception in thread "Thread-10" java.lang.IllegalStateException: Shutdown in
> progress
> at java.lang.Shutdown.add(Shutdown.java:81)
> at java.lang.Runtime.addShutdownHook(Runtime.java:190)
> at org.apache.hadoop.fs.FileSystem$Cache.get(FileSystem.java:1293)
> at org.apache.hadoop.fs.FileSystem.get(FileSystem.java:203)
> at org.apache.hadoop.fs.FileSystem.get(FileSystem.java:108)
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