Cannot create configuration due to log4net loading failure

[JonasBRasmussen]

I'm trying to upgrade NH from 4.0.0 til 5.1.3. I have installed the proper Nuget packages and have not yet changed any existing code. This is the first (and right now, only) line of NHibernate-related code:

var config = new NHibernate.Cfg.Configuration();

After this, I plan to do different things to complete the configuration. However, the code fails at this line and I am unable to do any configuration.

I cloned the NH repo so I could debug the problem, and I cannot get past the line

properties = Environment.Properties;

in the Reset() method of the NHibernate.Cfg.Configuration class.

All projects in my solution target .NET 4.6.1. A thing to note is that my web projects are SharePoint (2016) projects, and the assemblies are therefore deployed to the GAC. I have confirmed that all the assemblies have been deployed correctly and that there are no versioning issues (only one version of each NHibernate-related assembly is deployed to the GAC). And just to be clear, everything worked without issue on the same setup with NH 4.0.0 (if I uninstall 5.1.3 and go back to 4.0.0, then everything works just fine again).

I have spent the last couple of days on this upgrade and I am getting no closer to a solution. I hope you can help me out.

The complete stack trace for the exception is:

System.TypeInitializationException: The type initializer for 'NHibernate.Cfg.Environment' threw an exception.
---> System.TypeInitializationException: The type initializer for 'NHibernate.NHibernateLogger' threw an exception.
---> NHibernate.InstantiationException: Unable to instantiate: NHibernate.Log4NetLoggerFactoryNHibernate.Log4NetLoggerFactory
---> System.Reflection.TargetInvocationException: Exception has been thrown by the target of an invocation.
---> System.TypeInitializationException: The type initializer for 'NHibernate.Log4NetLoggerFactory' threw an exception.
---> System.NullReferenceException: Object reference not set to an instance of an object.
   at NHibernate.Log4NetLoggerFactory.GetGetLoggerByNameMethodCall()
   at NHibernate.Log4NetLoggerFactory..cctor()
   --- End of inner exception stack trace ---
   at NHibernate.Log4NetLoggerFactory..ctor()
   --- End of inner exception stack trace ---
   at System.RuntimeTypeHandle.CreateInstance(RuntimeType type, Boolean publicOnly, Boolean noCheck, Boolean& canBeCached, RuntimeMethodHandleInternal& ctor, Boolean& bNeedSecurityCheck)
   at System.RuntimeType.CreateInstanceSlow(Boolean publicOnly, Boolean skipCheckThis, Boolean fillCache, StackCrawlMark& stackMark)
   at System.Activator.CreateInstance(Type type, Boolean nonPublic)
   at System.Activator.CreateInstance(Type type)
   at NHibernate.NHibernateLogger.GetLoggerFactory(String nhibernateLoggerClass)
   --- End of inner exception stack trace ---
   at NHibernate.NHibernateLogger.GetLoggerFactory(String nhibernateLoggerClass)
   at NHibernate.NHibernateLogger..cctor()
   --- End of inner exception stack trace ---
   at NHibernate.NHibernateLogger.For(Type type)
   at NHibernate.Cfg.Environment..cctor()
   --- End of inner exception stack trace ---
   at NHibernate.Cfg.Configuration.Reset()
   at MyCompany.MyProject.CreateNHibernateConfiguration()

[fredericDelaporte]

It seems the application finds a log4net assembly in the application directory and tries to instantiate the logger for it, but then fails as if the assembly was indeed not available (or maybe outdated, classes not having expected methods).

Either remove log4net or ensure it is up-to-date and available in GAC.

[JonasBRasmussen]

Thank you for the fast response!

I do have a log4net assembly in the GAC, version 2.0.8, which I use for my own logging purposes. Does NHibernate expect a different version?

[fredericDelaporte]

That is the version used in NHibernate tests.

Have you check no older version was also in the GAC?
NHibernate loading mechanism for log4net is System.Type.GetType("log4net.LogManager, log4net"), so it may load any log4net version.
This has not changed since 2010, but in 5.0.0 the code searches for LogManager.GetLogger(Assembly, string), while previously it was searching for the overload just taking a string. So maybe this method was not existing in older versions of log4net (but it looks unlikely to me).

Otherwise, NHibernate attempts to load log4net only if it finds it in the app domain base directory or search directory. This has not changed either, but maybe during your test a log4net assembly gets there while in your normal setup it is not there, avoiding having NHibernate attempting to load it.

Corresponding code is:

nhibernate-core/src/NHibernate/Logging.cs

Lines 120 to 129 in f8b1bc4

	// look for log4net.dll
	string baseDir = AppDomain.CurrentDomain.BaseDirectory;
	string relativeSearchPath = AppDomain.CurrentDomain.RelativeSearchPath;
	string binPath = relativeSearchPath == null ? baseDir : Path.Combine(baseDir, relativeSearchPath);
	string log4NetDllPath = binPath == null ? "log4net.dll" : Path.Combine(binPath, "log4net.dll");
	if (File.Exists(log4NetDllPath) || AppDomain.CurrentDomain.GetAssemblies().Any(a => a.GetName().Name == "log4net"))
	{
	nhibernateLoggerClass = typeof(Log4NetLoggerFactory).AssemblyQualifiedName;
	}

If you do not need NHbernate logs, you can also disable them instead: put an empty appSetting named nhibernate-logger in your application .config file.

[JonasBRasmussen]

Yeah, I dug through that code as well. When I attempted to debug I was unable to hit a breakpoint in the code extract from your post. I just can't make it past the call to Environment.Properties.

I only see one log4net folder in the GAC:

I checked both C:\Windows\Microsoft.NET\assembly and C:\Windows\assembly, and this was the only place I found anything with log4net.

Before upgrading, I did use NHibernate logging of SQL statements, and I'd prefer not to lose that. But if I could get async instead, I might be willing to accept it. But I'm not sure it would help me to put the app setting you mentioned in my .config file, since the crash happens on the Reset() call before anything is attempted to be read from a .config file.

[JonasBRasmussen]

I found the problem! Thanks to your work in #1837, which I replicated, built and deployed locally, I was able to get a more reasonable exception message. It was of course something stupid. :)

System.IO.FileNotFoundException: Could not load file or assembly 'Remotion.Linq, Version=2.1.0.0, Culture=neutral, PublicKeyToken=fee00910d6e5f53b' or one of its dependencies. The system cannot find the file specified

My NuGet references to Remotion.Linq and Remotion.Linq.EagerFetching had been updated to 2.2.0, while NHibernate expects 2.1.0. A simple binding redirect fixed the problem.

[fredericDelaporte]

You may have other issues after the binding redirect. Some possible breaking changes in Remotion 2.2.0 are breaking for NHibernate. See #696. If you must use ReLinq 2.2 instead of 2.1, you would have to wait for NHibernate 5.2.

[JonasBRasmussen]

Thanks for the info! What's the planned release date for 5.2?

[JonasBRasmussen]

Just to follow up: I downgraded the Remotion.Linq packages to 2.1 and removed the binding redirects and that seemed to do it. I then switched back to the official NHibernate 5.1.3 release and that gave me the same error as before. So for now I need to use the changes referenced in #1837 to even make it work. Really look forward to an updated official release (could just be 5.1.4).

[fredericDelaporte]

This means the ReLinq reference trouble was another, unrelated trouble.

For checking what is the actual trouble with the logger, may you try again but only with Logging.log4net.cs file changes? The changes in the other file are likely to cause the logger to be indeed disabled in your case.

(Alternatively, you can also fully take #1837 changes but moreover, in your application code, force the logger to use log4net with following instruction: NHibernateLogger.SetLoggersFactory(new Log4NetLoggerFactory());. It will likely fail in your application case to instantiate the factory, due to static constructor failure, but with my changes, with a better error message.)

[JonasBRasmussen]

Indeed, it does not work if I rollback the changes made to Logging.cs. The stack trace this time is a little more telling, since we now get System.IO.FileNotFoundException: Could not load file or assembly 'log4net' or one of its dependencies. The system cannot find the file specified. The full stack trace:

System.TypeInitializationException: The type initializer for 'NHibernate.Cfg.Environment' threw an exception.
---> System.TypeInitializationException: The type initializer for 'NHibernate.NHibernateLogger' threw an exception.
---> NHibernate.InstantiationException: Unable to instantiate: NHibernate.Log4NetLoggerFactoryNHibernate.Log4NetLoggerFactory
---> System.Reflection.TargetInvocationException: Exception has been thrown by the target of an invocation.
---> System.TypeInitializationException: The type initializer for 'NHibernate.Log4NetLoggerFactory' threw an exception.
---> System.IO.FileNotFoundException: Could not load file or assembly 'log4net' or one of its dependencies. The system cannot find the file specified.
   at System.RuntimeTypeHandle.GetTypeByName(String name, Boolean throwOnError, Boolean ignoreCase, Boolean reflectionOnly, StackCrawlMarkHandle stackMark, IntPtr pPrivHostBinder, Boolean loadTypeFromPartialName, ObjectHandleOnStack type)
   at System.RuntimeTypeHandle.GetTypeByName(String name, Boolean throwOnError, Boolean ignoreCase, Boolean reflectionOnly, StackCrawlMark& stackMark, IntPtr pPrivHostBinder, Boolean loadTypeFromPartialName)
   at System.Type.GetType(String typeName, Boolean throwOnError)
   at NHibernate.Log4NetLoggerFactory..cctor()
   --- End of inner exception stack trace ---
   at NHibernate.Log4NetLoggerFactory..ctor()
   --- End of inner exception stack trace ---
   at System.RuntimeTypeHandle.CreateInstance(RuntimeType type, Boolean publicOnly, Boolean noCheck, Boolean& canBeCached, RuntimeMethodHandleInternal& ctor, Boolean& bNeedSecurityCheck)
   at System.RuntimeType.CreateInstanceSlow(Boolean publicOnly, Boolean skipCheckThis, Boolean fillCache, StackCrawlMark& stackMark)
   at System.Activator.CreateInstance(Type type, Boolean nonPublic)
   at System.Activator.CreateInstance(Type type)
   at NHibernate.NHibernateLogger.GetLoggerFactory(String nhibernateLoggerClass)
   --- End of inner exception stack trace ---
   at NHibernate.NHibernateLogger.GetLoggerFactory(String nhibernateLoggerClass)
   at NHibernate.NHibernateLogger..cctor()
   --- End of inner exception stack trace ---
   at NHibernate.NHibernateLogger.For(Type type)
   at NHibernate.Cfg.Environment..cctor()
   --- End of inner exception stack trace ---
   at NHibernate.Cfg.Configuration.Reset()
   at MyCompany.MyProject.CreateNHibernateConfiguration()

[fredericDelaporte]

I cannot tell more from that. Now you would have to do classical dependency loading failure debugging. (Like using fusion log.)

You can still work around the issue either by using my full changes (which surely cause the logger to be disabled in your case) or by disabling the logger yourself as explained in a previous comment.

But I'm not sure it would help me to put the app setting you mentioned in my .config file, since the crash happens on the Reset() call before anything is attempted to be read from a .config file.

This setting has a special independent handling. It is a .Net appSetting, not a NHibernate setting.

[JonasBRasmussen]

I'll keep looking into it. When I do AppDomain.CurrentDomain.GetAssemblies().Any(a => a.GetName().Name == "log4net") from application code it finds the log4net assembly just fine, so I don't know why it wouldn't work for NH.

I also tried your other suggestion, but I cannot do NHibernateLogger.SetLoggersFactory(new Log4NetLoggerFactory()) since Log4NetLoggerFactory is not assignable to INHibernateLoggerFactory.