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Posted to dev@mina.apache.org by "jpalacios (JIRA)" <ji...@apache.org> on 2018/10/26 02:30:00 UTC

[jira] [Closed] (SSHD-855) CachingPublicKeyAuthenticator not clearing up closed sessions

     [ https://issues.apache.org/jira/browse/SSHD-855?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

jpalacios closed SSHD-855.
--------------------------
    Resolution: Duplicate

> CachingPublicKeyAuthenticator not clearing up closed sessions
> -------------------------------------------------------------
>
>                 Key: SSHD-855
>                 URL: https://issues.apache.org/jira/browse/SSHD-855
>             Project: MINA SSHD
>          Issue Type: Bug
>    Affects Versions: 1.7.0
>            Reporter: jpalacios
>            Priority: Major
>
> I'm currently investigating an incident in a production environment which resulted in an {{OutOfMemoryError}}.
> According to the heap dump we are seeing massive object graphs made up of nested MINA's {{NioSocketSessions}}:
> {code:java}
> Thread -> ServerSessionImpl -> SshServer -> JohnsonAwarePublicKeyAuthenticator -> CachingPublicKeyAuthenticator -> ConcurrentHashMap -> ConcurrentHashMap$Node[] -> ConcurrentHashMap$Node -> ServerSessionImpl -> MinaSession -> NioSocketSession -> SelectionKeyImpl -> EpollSelectorImpl -> HashMap -> SelectionKeyImpl -> NioSocketSession -> ...
> {code}
> As you can see pass the first {{NioSocketSession}} the graph starts to repeat itself. These are not loops however. These are all different instances with a small shallow size but which add up to massive retained sizes. The {{CachingPublicKeyAuthenticator}} in particular has a retained size of ~6GB.
> Another interesting thing is that AFAICT out the 94K {{NioSocketSession}} instances in the heap, 93983 have a closed channel and the {{ServerSessionImpl}} that directly reference them is closed as well. 59 of these {{ServerSessionImpl}} instances are directly referenced from the {{cache}} map in {{CachingPublicKeyAuthenticator}}.
> I'm still gathering information to understand the load the system was in at the time of the incident, but I would appreciate your help in trying to understand how this nested graph could be put together, and if there's a scenario in which the {{CachingPublicKeyAuthenticator}} may fail to clear it's cached correctly.



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