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From "Ralph Goers (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (LOG4J2-149) SMTPManager buffer access not synchronized; can result in empty emails
Date Mon, 14 Jan 2013 17:42:12 GMT

    [ https://issues.apache.org/jira/browse/LOG4J2-149?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13552919#comment-13552919
] 

Ralph Goers commented on LOG4J2-149:
------------------------------------

It took me by surprise too when I first saw how the SMTPAppender worked, but I understand
what it is trying to do. There isn't any danger of the isFilter method being called twice
- that is only going to happen in the AppenderControl.  Note that this will NOT capture events
that have been filtered by a global Filter, Logger Filter or Appender-ref Filter as they will
never make it this far.  You would have to create a special global filter to capture the events
if you really want to capture everything.

As for the patch, I'm not sure what it is accomplishing.  The CyclicBuffer add and removeAll
methods are synchronized so wrapping those calls in a synchronized block doesn't do anything
useful.  Removing buffer as a parameter from two methods and then having writeBuffer just
reference the member variable also should accomplish nothing.  So I'm not ready to apply this
patch until I understand how it fixes the problem.

It would also be helpful to have a test that demonstrates the problem.

                
> SMTPManager buffer access not synchronized; can result in empty emails
> ----------------------------------------------------------------------
>
>                 Key: LOG4J2-149
>                 URL: https://issues.apache.org/jira/browse/LOG4J2-149
>             Project: Log4j 2
>          Issue Type: Bug
>          Components: Appenders
>    Affects Versions: 2.0-beta4
>         Environment: N/A
>            Reporter: Scott Severtson
>         Attachments: SMTPManager-buffer-synchronization.patch
>
>
> If multiple error events are logged against the same SMTPAppender/Manager at the same
time, one email will contain both error messages, while the second will be empty (no events).
> The original SMTPAppender patch included synchronization against the CyclicBuffer to
prevent such simultaneous access from multiple threads. This appears to have been lost in
the merge/refactor. Patch (to follow shortly) re-introduces synchronization against the CyclicBuffer
in the narrowest possible scope.

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