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From "Emmanuel Lecharny (JIRA)" <j...@apache.org>
Subject [jira] [Comment Edited] (DIRMINA-1021) MINA-CORE does not remove sessions if exceptions occur while closing
Date Sun, 06 Dec 2015 05:53:10 GMT

    [ https://issues.apache.org/jira/browse/DIRMINA-1021?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15043714#comment-15043714
] 

Emmanuel Lecharny edited comment on DIRMINA-1021 at 12/6/15 5:52 AM:
---------------------------------------------------------------------

yes, but...

what happens is that {{isClosing}} simply means the session is scheduled for closing, not
actually closed. The rationnal being that some data might be still waiting to be sent, and
because the server has decided to close the session does not necessarily implies those data
should be discarded.

In this very case, we have got an exception, mostly because the client is not there anymore,
thus there is no reason to wait for the pending data to be kept in memory and for the session
to remain in this state forever. This is why it's good to close the session immediately when
an exception is caught.


was (Author: elecharny):
yes, but...

what happens is that {{isClosing}} simply means the session is scheduled for closing, not
actually closed. The rationnal being that some data might be still waiting to be sent, and
because the server has decided to close the session does nit necessarily implies those data
to be discarded.

In this very case, we have got an exception, mostly because the client is not there anymore,
thus there is no reason to wait for the pending data to be kept in memory and for the session
to remain in this state forever. This is why it's good to close the session immediately when
an exception is caught.

> MINA-CORE does not remove sessions if exceptions occur while closing
> --------------------------------------------------------------------
>
>                 Key: DIRMINA-1021
>                 URL: https://issues.apache.org/jira/browse/DIRMINA-1021
>             Project: MINA
>          Issue Type: Bug
>    Affects Versions: 2.0.8
>         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
>         Attachments: attempt-removing-sessions-closing.patch
>
>
> 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.
> The attached patch (to mina-core) seems to resolve the issue by following the reproduction
case I have on the [Gerrit issue tracker|https://code.google.com/p/gerrit/issues/detail?id=3685].



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