[jira] [Created] (SSHD-595) SSHD does not remove sessions if exceptions occur while closing

["Doug Kelly (JIRA)" <ji...@apache.org>]

Doug Kelly created SSHD-595:
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             Summary: SSHD does not remove sessions if exceptions occur while closing
                 Key: SSHD-595
                 URL: https://issues.apache.org/jira/browse/SSHD-595
             Project: MINA SSHD
          Issue Type: Bug
    Affects Versions: 0.14.0
         Environment: mina-ssh 0.14.0
mina-core 2.0.8
Multiple OSes / Java configurations:
* Mac OS X El Capitan on Java 8 (1.8.0_60)
* CentOS 6.4 on Java 8 (1.8.0_60)
* CentOS 6.5 on Java 8 (1.8.0_20-b26).
            Reporter: Doug Kelly


MINA SSHD isn't removing sessions when using the MINA/NIO backend if an exception as received as the session is closing (such as a connection reset is received with data still in the write buffer).  When this case happens, it seems that {{NioProcessor.getState}} returns the state as {{CLOSING}} (I'm assuming since the underlying channel is now closed), which means that the {{AbstractPollingIoProcessor.removeSessions()}} won't ever prune the session, since a {{CLOSING}} state is simply ignored.  The result is a resource leak over time, since these sessions are never pruned (it's a slow leak, since entering this condition is racy -- on my workstation, I can produce it through randomly interrupting connections anywhere from 1/6 to 1/10th of the time). (This may either be major or critical; reprioritize as necessary.)

I specifically see this error with Gerrit 2.10.4 and Gerrit 2.11.5 (using mina-sshd 0.14.0 / mina-core 2.0.8), and it looks like the code path is unchanged in mina-sshd 1.0.0 / mina-core 2.0.9.  I was unsure if this is specifically a bug in mina-core or, if it's something unique to mina-sshd.  My local development system runs Mac OS X El Capitan on Java 8 (1.8.0_60), but I've also seen this on Linux (CentOS 6.4, again Java 1.8.0_60 and CentOS 6.5 on Java 1.8.0_20-b26).

The fix may be as simple as attempting to remove the session if {{OPENED}} or {{CLOSING}}, but I'm unsure what side-effects this may have with other backends.  I'll be happy to test it locally, but I'm fairly ignorant when it comes to MINA's code.



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