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https://issues.apache.org/jira/browse/LOG4NET-175?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Roy Chastain reassigned LOG4NET-175:
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Assignee: Roy Chastain
> RollingFileAppender generates unexpected filename and/or causes IIS to hang
> ---------------------------------------------------------------------------
>
> Key: LOG4NET-175
> URL: https://issues.apache.org/jira/browse/LOG4NET-175
> Project: Log4net
> Issue Type: Bug
> Components: Appenders
> Affects Versions: 1.2.9
> Environment: win32
> Reporter: Devan Iyer
> Assignee: Roy Chastain
> Fix For: 1.2 Maintenance Release
>
> Original Estimate: 2h
> Remaining Estimate: 2h
>
> We are using rolling file appender in an IIS managed C# application. Our
> log4Net deployment is configured with the following options specified in
> basic.xml: <appendToFile value="false" /> <countDirection value="0" />
> <maximumFileSize value="512KB" /> <maxSizeRollBackups value="100" />
> <rollingStyle value="Once" /> <staticLogFileName value="false" />. The file
> pattern for our log file name is "abc_%date{yyyyMMdd_HHmmss}_%processid_.log".
> We have observed in our production environment that occasionally filenames
> would be created with patterns like
> "abc_%date{yyyyMMdd_HHmmss}_%processid_.log.1",
> "abc_%date{yyyyMMdd_HHmmss}_%processid_.log.1.2",
> "abc_%date{yyyyMMdd_HHmmss}_%processid_.log.1.2.3", etc. We have observed
> filenames with the dot+sequential numbers pattern after the .log to be
> anything from ".1" to ".220". This is one of two unexpected behaviours
> observed.
>
> The second unexpected behaviour seems to a special case of the first that
> occasionally causes IIS to hang (100% CPU consumption). An analysis of
> several crash dumps taken at the time of the hang indicated that
> RollingFileAppender had in memory a filename of the same pattern as above but
> with the number of characters [base filename pattern]+[recurring extension
> pattern] exceeding 255 characters. It is very likely that an attempt to
> create a file by such name on NTFS would throw exceptions at various levels -
> managed and native - and hence the file itself is never created.
>
> To the best of our knowledge, there were no events to trigger the filename to
> be rolled. As indicated in the configuration options, we are using
> RollingStyle of "Once". (The log file content is minimal at the time the
> symptoms occur - total file size is about 2K - and the times of occurrence
> are totally non related).
>
> We have been unable to capture the workflow leading up to the symptoms above
> due to the high number of users and document types in our production
> environment. The permissions on the logging folder are static. However, we
> have found a simple workflow in our lab environment, using permissions, that
> produce similar symptoms. This workflow is:
>
> - Right click on the logging folder and select "Properties"
> - Under the "Security" tab ensure that IIS_WPG group doesn't have write
> access to the logging folder.
> - Restart IIS
> - Launch our application and view a document. Check the logging folder to
> make sure that a logfile is not created.
> - View a few more documents
> - Change the permission on the logging folder and ensure IIS_WPG group has
> write access to the folder. DO NOT restart IIS after changing the permission.
> - Launch our application and view another document.
> - At this point a logfile with a filename pattern described will be found in
> the logging folder.
>
> As mentioned, it is unlikely that permissions are the trigger in our event
> but it is likely that the same code is creating these unexpected patterns
> irrespective of the trigger.
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