Log4net
  1. Log4net
  2. LOG4NET-175

RollingFileAppender generates unexpected filename and/or causes IIS to hang

    Details

    • Type: Bug Bug
    • Status: Open
    • Priority: Major Major
    • Resolution: Unresolved
    • Affects Version/s: 1.2.9
    • Fix Version/s: 1.2 Maintenance Release
    • Component/s: Appenders
    • Labels:
      None
    • Environment:
      win32

      Description

      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.

        Issue Links

          Activity

          Hide
          Devan Iyer added a comment - - edited

          I solved this one:

          This behaviour is due to RollingFileAppender and it's base class FileAppender not resetting certain private member variables when an OpenFile call fails.

          RollingFileAppender.OpenFile (filename, bAppend) always does a GetNextOutputFileName(fileName) before calling the base class OpenFile. This appends the string value of m_curSizeRollBackups to filename.

          FileAppender.OpenFile (filename, bAppend) stores in private member variables the value of the arguments filename and bAppend and then attempts to create a LockingStream. This fails with a LockStateException which is not handled. The correct approach would be to roll back the values of m_fileName, m_appendToFile , m_curSizeRollBackups and m_scheduledFilename when the OpenFile call fails. I accomplished this in my subclass as follows:

          protected override void <MyClass>OpenFile(string fileName, bool append)
          {
          bool oldAppend = this.AppendToFile;
          string oldFileName = this.File;

          try

          { base.OpenFile (fileName, append); }

          catch (log4net.Core.LogException ex)

          { LogLog.Debug ("MyClass.OpenFile, base.OpenFile (fileName, append) threw an exception, " + ex.Message); base.File = oldFileName; // easily set by protected property access base.AppendToFile = oldAppend; // easily set by protected property access base.ExistingInit (); // no access to m_curSizeRollBackups and m_scheduledFilename but this will do it. }

          }

          Ideally this fix should be in the core RollingFileAppender, FileAppender implementations with appropriate additional configuration status checks.

          Show
          Devan Iyer added a comment - - edited I solved this one: This behaviour is due to RollingFileAppender and it's base class FileAppender not resetting certain private member variables when an OpenFile call fails. RollingFileAppender.OpenFile (filename, bAppend) always does a GetNextOutputFileName(fileName) before calling the base class OpenFile. This appends the string value of m_curSizeRollBackups to filename. FileAppender.OpenFile (filename, bAppend) stores in private member variables the value of the arguments filename and bAppend and then attempts to create a LockingStream. This fails with a LockStateException which is not handled. The correct approach would be to roll back the values of m_fileName, m_appendToFile , m_curSizeRollBackups and m_scheduledFilename when the OpenFile call fails. I accomplished this in my subclass as follows: protected override void <MyClass>OpenFile(string fileName, bool append) { bool oldAppend = this.AppendToFile; string oldFileName = this.File; try { base.OpenFile (fileName, append); } catch (log4net.Core.LogException ex) { LogLog.Debug ("MyClass.OpenFile, base.OpenFile (fileName, append) threw an exception, " + ex.Message); base.File = oldFileName; // easily set by protected property access base.AppendToFile = oldAppend; // easily set by protected property access base.ExistingInit (); // no access to m_curSizeRollBackups and m_scheduledFilename but this will do it. } } Ideally this fix should be in the core RollingFileAppender, FileAppender implementations with appropriate additional configuration status checks.
          Hide
          Eike-Peter Falk added a comment -

          Probably both issues have the same reason.

          Show
          Eike-Peter Falk added a comment - Probably both issues have the same reason.

            People

            • Assignee:
              Unassigned
              Reporter:
              Devan Iyer
            • Votes:
              2 Vote for this issue
              Watchers:
              1 Start watching this issue

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