[HDFS-11208] Deadlock in WebHDFS on shutdown

• Type: Bug
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Affects Version/s: 2.8.0, 2.7.3, 2.6.5, 3.0.0-alpha1
• Component/s: webhdfs
• Assignee: Erik Krogen
• Reporter: Erik Krogen
• Created: 05/Dec/16 22:54
• Updated: 30/Dec/16 21:35

Description

Currently on the client side if the DelegationTokenRenewer attempts to renew a WebHdfs delegation token while the client system is shutting down (i.e. FileSystem.Cache.ClientFinalizer is running) a deadlock may occur. This happens because ClientFinalizer calls FileSystem.Cache.closeAll() which first takes a lock on the FileSystem.Cache object and then locks each file system in the cache as it iterates over them. DelegationTokenRenewer takes a lock on a filesystem object while it is renewing that filesystem's token, but within TokenAspect.TokenManager.renew() (used for renewal of WebHdfs tokens) FileSystem.get is called, which in turn takes a lock on the FileSystem cache object, potentially causing deadlock if ClientFinalizer is currently running.

See below for example deadlock output:

Found one Java-level deadlock:
=============================
"Thread-8572":
waiting to lock monitor 0x00007eff401f9878 (object 0x000000051ec3f930, a
dali.hdfs.web.WebHdfsFileSystem),
which is held by "FileSystem-DelegationTokenRenewer"
"FileSystem-DelegationTokenRenewer":
waiting to lock monitor 0x00007f005c08f5c8 (object 0x000000050389c8b8, a
dali.fs.FileSystem$Cache),
which is held by "Thread-8572"

Java stack information for the threads listed above:
===================================================
"Thread-8572":
at dali.hdfs.web.WebHdfsFileSystem.close(WebHdfsFileSystem.java:864)

   - waiting to lock <0x000000051ec3f930> (a
   dali.hdfs.web.WebHdfsFileSystem)
   at dali.fs.FilterFileSystem.close(FilterFileSystem.java:449)
   at dali.fs.FileSystem$Cache.closeAll(FileSystem.java:2407)
   - locked <0x000000050389c8b8> (a dali.fs.FileSystem$Cache)
   at dali.fs.FileSystem$Cache$ClientFinalizer.run(FileSystem.java:2424)
   - locked <0x000000050389c8d0> (a
   dali.fs.FileSystem$Cache$ClientFinalizer)
   at dali.util.ShutdownHookManager$1.run(ShutdownHookManager.java:54)
   "FileSystem-DelegationTokenRenewer":
   at dali.fs.FileSystem$Cache.getInternal(FileSystem.java:2343)
   - waiting to lock <0x000000050389c8b8> (a dali.fs.FileSystem$Cache)
   at dali.fs.FileSystem$Cache.get(FileSystem.java:2332)
   at dali.fs.FileSystem.get(FileSystem.java:369)
   at
   dali.hdfs.web.TokenAspect$TokenManager.getInstance(TokenAspect.java:92)
   at dali.hdfs.web.TokenAspect$TokenManager.renew(TokenAspect.java:72)
   at dali.security.token.Token.renew(Token.java:373)
   at

   dali.fs.DelegationTokenRenewer$RenewAction.renew(DelegationTokenRenewer.java:127)
   - locked <0x000000051ec3f930> (a dali.hdfs.web.WebHdfsFileSystem)
   at

   dali.fs.DelegationTokenRenewer$RenewAction.access$300(DelegationTokenRenewer.java:57)
   at dali.fs.DelegationTokenRenewer.run(DelegationTokenRenewer.java:258)

Found 1 deadlock.