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From "Alexander Klimetschek (JIRA)" <j...@apache.org>
Subject [jira] Commented: (JCR-2378) Avoid exceptions thrown in finalize handler of RepositoryImpl constructor
Date Mon, 02 Nov 2009 15:58:59 GMT

    [ https://issues.apache.org/jira/browse/JCR-2378?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12772546#action_12772546

Alexander Klimetschek commented on JCR-2378:

>  I would prefer to see a solution to the root cause

Yes, but I think there is too much involved to capture all possible problems (easily). Therefore
I think this is just good defensive programming. I'll change the wording and add "unexpected"
rather than "likely to fail".

Also created a separate issue for the NPE: JCR-2380

> Avoid exceptions thrown in finalize handler of RepositoryImpl constructor
> -------------------------------------------------------------------------
>                 Key: JCR-2378
>                 URL: https://issues.apache.org/jira/browse/JCR-2378
>             Project: Jackrabbit Content Repository
>          Issue Type: Improvement
>          Components: jackrabbit-core
>    Affects Versions: 2.0-alpha11
>            Reporter: Alexander Klimetschek
>            Assignee: Alexander Klimetschek
>            Priority: Minor
>         Attachments: JCR-2378.patch
> If an exception happens during initialization of the repository, it might be overlayed
by an exception thrown in the finalize handler of the RepositoryImpl constructor (see line
382 ff in [1]). The latter exception wins and the original exception is lost (if you don't
have a log). This makes it hard to figure out the real problem.
> This problem is actually a bit self-enforcing: if something goes wrong during startup,
the code in the shutdown() method that is called is actually very prone to fail as it might
not expect such a broken-startup state. In my case the overlaying NPE happened in ObservationManagerImpl.getRegisteredEventListeners,
where this.dispatcher was unexpectedly null [2].
> I think both places should be fixed (NPE guard in ObservationManagerImpl constructor
for "dispatcher") and a try/catch block in the finalizer, just logging the exception:
>     } finally {
>         if (!succeeded) {
>             try {
>                 // repository startup failed, clean up...
>                 shutdown();
>             } catch (Throwable t) {
>                 // shutdown() likely to fail now, as startup was broken...
>                 log.error("In addition to startup fail, another problem occurred while
shutting down the repository again.", e);
>             }
>         }
>     }
> [1] http://svn.apache.org/viewvc/jackrabbit/trunk/jackrabbit-core/src/main/java/org/apache/jackrabbit/core/RepositoryImpl.java?view=markup
> [2] Overlaying exception's stacktrace:
> Caused by: java.lang.NullPointerException
> 	at org.apache.jackrabbit.core.observation.ObservationManagerImpl.getRegisteredEventListeners(ObservationManagerImpl.java:143)
> 	at org.apache.jackrabbit.core.SessionImpl.removeRegisteredEventListeners(SessionImpl.java:1190)
> 	at org.apache.jackrabbit.core.SessionImpl.logout(SessionImpl.java:1215)
> 	at org.apache.jackrabbit.core.RepositoryImpl$WorkspaceInfo.doDispose(RepositoryImpl.java:2153)
> 	at com.day.crx.core.CRXRepositoryImpl$CRXWorkspaceInfo.doDispose(CRXRepositoryImpl.java:1095)
> 	at org.apache.jackrabbit.core.RepositoryImpl$WorkspaceInfo.dispose(RepositoryImpl.java:2108)
> 	at org.apache.jackrabbit.core.RepositoryImpl.doShutdown(RepositoryImpl.java:1146)
> 	at com.day.crx.core.CRXRepositoryImpl.doShutdown(CRXRepositoryImpl.java:845)
> 	at org.apache.jackrabbit.core.RepositoryImpl.shutdown(RepositoryImpl.java:1098)
> 	at org.apache.jackrabbit.core.RepositoryImpl.<init>(RepositoryImpl.java:387)
> 	at com.day.crx.core.CRXRepositoryImpl.<init>(CRXRepositoryImpl.java:201)
> 	at com.day.crx.core.CRXRepositoryImpl.create(CRXRepositoryImpl.java:190)
> 	... 28 more

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