log4net: error could not create appender [RollingLogFileAppender]

Question

So, I have a project in git repo, and 2 branches: master and fix-master. I've not changed code associated with log4net in fix-master. But every time, when I've started master - I don't have this problem, if I checkout to fix-master, I have this error after this line:

private static readonly ILog Log = LogManager.GetLogger(typeof(Program));

You shouldn't see errors thrown from log4net unless you've specifically set it to do so - as per [the faq](https://logging.apache.org/log4net/release/faq.html) _log4net will not throw unexpected exceptions at run-time potentially causing your application to crash. If for any reason, log4net throws an uncaught exception (except for ArgumentException and ArgumentNullException which may be thrown), please send an email to the log4net-user@logging.apache.org mailing list. Uncaught exceptions are handled as serious bugs requiring immediate attention."_ — stuartd, Sep 27 '19 at 00:00
I suggest you [enable log4net debugging](https://stackoverflow.com/questions/756125/how-to-track-down-log4net-problems) and see _why_ it cannot create the file. — stuartd, Sep 27 '19 at 00:01
What error you have? Can you share the log4net configuration? — Chetan, Sep 27 '19 at 01:16

score 2 · Accepted Answer · answered Sep 27 '19 at 01:21

Aside from the obvious candidates (illegal filepath, permissions error), the problem could even be mutex locking:

https://issues.apache.org/jira/browse/LOG4NET-506

RollingFileAppender locking log folder in some cases

Abstract:
In some configuration cases, the rolling file appender may issue a mutex lock on the folder name. If more than one processes try to do that with different executing identity, only one will be able to log to its specific logs file. The others will no more be able to do it.

SUGGESTION:

Add this line to your app.config/web.config, under appSettings, to enable internal debugging:

<add key="log4net.Internal.Debug" value="true"/>

This will give you output like this, to both the system console and to System.Diagnostics.Trace

log4net:ERROR Could not create Appender [RollingLogFileAppender] of type [log4net.Appender.RollingFileAppender]. Reported error follows.
System.UnauthorizedAccessException: Access to path 'D__Logs_' denied. (Translated from french)
   à System.IO.__Error.WinIOError(Int32 errorCode, String maybeFullPath)
   à System.Threading.Mutex.MutexTryCodeHelper.MutexTryCode(Object userData)
   à System.Runtime.CompilerServices.RuntimeHelpers.ExecuteCodeWithGuaranteedCleanup(TryCode code, CleanupCode backoutCode, Object userData)
   à  System.Threading.Mutex.CreateMutexWithGuaranteedCleanup(Boolean initiallyOwned, String name, Boolean& createdNew, SECURITY_ATTRIBUTES secAttrs)
   à  System.Threading.Mutex..ctor(Boolean initiallyOwned, String name, Boolean& createdNew, MutexSecurity mutexSecurity)
   à  System.Threading.Mutex..ctor(Boolean initiallyOwned, String name, Boolean& createdNew)
   à  log4net.Appender.RollingFileAppender.ActivateOptions()
   à  log4net.Repository.Hierarchy.XmlHierarchyConfigurator.ParseAppender(XmlElement appenderElement)
log4net:ERROR Appender named [RollingLogFileAppender] not found.

Please try this, and post back what you find!

log4net: error could not create appender [RollingLogFileAppender]

1 Answers1