Develop Reference

Docker missing log4net ConsoleAppender logs

I've got a simple C# program with the following log4net configuration:
<log4net>
<appender name="stdout" type="log4net.Appender.ConsoleAppender">
<layout type="log4net.Layout.PatternLayout">
<conversionPattern value="%%-5level - %message%newline" />
</layout>
</appender>
<root>
<level value="DEBUG" />
<appender-ref ref="stdout" />
</root>
</log4net>
And the following code (abbreviated for clarity):
public static void Main(String[] args)
{
var log = LogManager.GetLogger("Logger");
log.Info("Hello From Logger");
Console.WriteLine("Hello From Console");
}
I'm compiling and running this using .NET 4.5 mono on an Ubuntu 16.04 system. When I run the program using the console the output is as expected:
$ mono Program.exe
INFO - Hello From Logger
Hello From Console
However, when I run this same program in a Docker container in detached mode (i.e, "docker run -d") and then check the logs, I only get the log from the Console.WriteLine:
$ docker logs <container_id>
Hello From Console
While trying to track this down, I tried running the program using the daemonize tool (more info here) and it illustrated the same behavior, leading me to believe it was an issue with log4net instead of docker.
I also wrote a custom appender for log4net that only does Console.Write (I believe that's the same functionality as ConsoleAppender, but I wanted to eliminate any other possible variables):
public class CustomAppender: AppenderSkeleton
{
protected override void Append(LoggingEvent loggingEvent)
{
Console.Write(RenderLoggingEvent(loggingEvent));
}
}
But no luck.
Can anyone with a deep knowledge of log4net point me to where I could be doing something wrong, or explain what log4net could be doing to stdout such that other programs that should be capturing that stream don't?
UPDATE: The plot thickens! I wrote a quick and dirty executable that uses the Process class to execute my example program. It then grabs the stdout from the example program and writes it with Console.WriteLine, like so:
Process proc = new Process();
proc.StartInfo.FileName = "/path/to/example.exe";
proc.StartInfo.UseShellExecute = false;
proc.StartInto.RedirectStandardOutput = true;
proc.Start();
Thread.Sleep(1000);
Console.WriteLine(proc.StandardOutput.ReadToEnd());
This works fine when I run it directly from the console, but has the same problem when I run it from docker / daemonize. So now I'm really confused.

It's not much of an answer, but in case someone else runs into this problem, I was able to get logging to work by using the NLog library here.

Why is the XML node's parent node being changed?

I have searched on here and Google for an answer to this but I cannot find a thing, apologies if this is something simple.
I have the below code:
private XmlNode loadXMLNode(string configPath, string loggingPath)
{
configFile.Load(configPath);
XmlNode logging = configFile.DocumentElement.SelectSingleNode(loggingPath);
return logging;
}
public string testXMLNodeValue(string configPath, string loggingPath)
{
XmlNode logging = loadXMLNode(configPath, loggingPath);
string value = logging.Attributes["value"].Value;
return value;
}
public void setXMLNodeValue(string configPath, string loggingPath, string newValue)
{
XmlNode logging = loadXMLNode(configPath, loggingPath);
logging.Attributes["value"].Value = newValue;
MessageBox.Show(logging.Attributes["value"].Value);
configFile.Save("C:\\inetpub\\CiresonPortal\\bin\\Cireson.CacheBuilder.Service.exe.config");
}
Which does correctly load the XML file and does modify the value in the targeted node. However it also changes the name of the parent node and I have no idea why.
(If you're wondering why the final path is hard coded it is because it was not saving the file at all when using the path from the configuration file, but that is a question for another thread.)
It should look like this:
<logger name="Logger">
<!-- LEVELS: ALL, DEBUG, INFO, WARN, ERROR, FATAL-->
<!-- Suggested for debugging: INFO -->
<!-- Suggested for production: WARN -->
<level value="ERROR" />
However once the above code runs it looks like this:
<root>
<level value="ERROR" />
Any help would be very much appreciated as I am still teaching myself c# (coming from a PowerShell background).
Thank you.

Using 'Environment' values in log4net configuration

My application can be started both as a Windows Service and in console environment. For each case, I need some log4net appenders to be active (or not, respectively) as well as some which are active in both cases. (Service: RollingFileAppender, DebugAppender (if enabled), EventLogAppender | Console: ColoredConsoleAppender, DebugAppender (if enabled))
The only way to achieve something similar is using the PropertyFilter together with ThreadContext.Properties like so:
<filter type="log4net.Filter.PropertyFilter">
<key value="ApplicationMode" />
<stringToMatch value="Service" />
</filter>
if(!Environment.UserInteractive)
ThreadContext.Properties["ApplicationMode"] = "Service";
However, since the property is declared on the thread context, it only works on the current thread. If the thread changes, the configuration is being reset and I have to declare it again.
Does log4net support a way to declare a PropertyFilter in configuration to setup the desired environment automatically? Like this:
<filter type="log4net.Filter.PropertyFilter">
<key value="{Environment.UserInteractive}" />
<stringToMatch value="false" />
</filter>
Or... is there a better approach? Since I didn't found a solution yet.. is this an uncommon practice?

See the last part of my answer to this question:
Capture username with log4net
To summarize, you can implement an object that contains the logic that you have above and put that object in GlobalContext.Properties. When log4net retrieves the value (your object) from the Properties, it will call ToString to get the actual value. Put your logic inside ToString.
Maybe something like this:
public class ApplicationModeProvider
{
public override string ToString()
{
return Environment.UserInteractive ? "Console" : "Service";
}
}
Put it in your dictionary at startup:
GlobalContext.Properties["ApplicationMode"] = new ApplicationModeProvider();
In effect, this is sort of like adding
if(!Environment.UserInteractive)
ThreadContext.Properties["ApplicationMode"] = "Service";
before ever logging statement.
I'm not sure, but I think that then you can configure your filter as you describe in your post.

log4net not working

Hey I have this configuration in my web.config
<log4net>
<appender name="LogFileAppender" type="log4net.Appender.FileAppender">
<param name="File" value="mylog.log" />
<param name="AppendToFile" value="true" />
<layout type="log4net.Layout.PatternLayout">
<param name="Header" value="" />
<param name="Footer" value="" />
<param name="ConversionPattern" value="%d [%t] %-5p %m%n" />
</layout>
</appender>
<appender name="ConsoleAppender" type="log4net.Appender.ConsoleAppender" >
<layout type="log4net.Layout.PatternLayout">
<param name="Header" value="[Header]\r\n" />
<param name="Footer" value="[Footer]\r\n" />
<param name="ConversionPattern" value="%d [%t] %-5p %m%n" />
</layout>
</appender>
<root>
<level value="DEBUG" />
<appender-ref ref="LogFileAppender" />
<appender-ref ref="ConsoleAppender" />
</root>
</log4net>
but log4net is not working. My project compiles fine, and I get no errors debugging either. The lines where I tell to log.debug("somemessage") gets run fine, but I can't find the mylog.log file, so where is it?

One gotcha for this type of thing is to make sure to add the XmlConfigurator attribute to the assembly by placing the following line in your AssemblyInfo.cs:
[assembly: log4net.Config.XmlConfigurator]
Otherwise log4net never activates.

I guess that either log4net is not logging at all, or the file is not ending up where you expect it.
Firstly, have you actually called
XmlConfigurator.Configure()
anywhere in your code? If the xml snippet above is in the application configuration file, this call will do the trick. If the xml snippet is in it's own file, you'll need to use the .Configure(string) overload that takes the path to the file. Without this call (or apparently the assembly level attribute mentioned by Kirk Woll), then log4net won't be logging at all.
If you believe this is all done, and log4net should be logging, then maybe you should put a fully qualified path in for the log file while you debug further. That will let you be sure where the file should be.

There is another small gotcha, see here: http://logging.apache.org/log4net/release/manual/configuration.html#dot-config
the [assembly: log4net.Config.XmlConfigurator] method doesn't work with app.config. If you configure log4net from app.config, you must use the log4net.Config.XmlConfigurator.Configure() method.

Here is my checklist for when log4net is proving to be recalcitrant:
ensure that log4net.config file is copied to the bin\ folder when building (set to 'Copy if newer' in compiler)
when dealing with installed code, ensure that the log4net.config came along for the ride (set to 'Content' in compiler)
ensure that the user that the process runs as has write rights to the folder where the logs are to be written
if in doubt, give promiscuous permissions to c:\temp\ and get everything to log to there ()
fire up Sysinternal/Dbgview.exe to see if that tells you anything

For an ASP.NET MVC project adding
log4net.Config.XmlConfigurator.Configure();
to the Global.asax.cs also helps:
public class MvcApplication : System.Web.HttpApplication
{
protected void Application_Start()
{
AreaRegistration.RegisterAllAreas();
WebApiConfig.Register(GlobalConfiguration.Configuration);
FilterConfig.RegisterGlobalFilters(GlobalFilters.Filters);
RouteConfig.RegisterRoutes(RouteTable.Routes);
BundleConfig.RegisterBundles(BundleTable.Bundles);
AuthConfig.RegisterAuth();
log4net.Config.XmlConfigurator.Configure();
}
}

These are the steps which eventually got my file logging working:
-Check AssemblyInfo.cs contains the following attribute.
[assembly: log4net.Config.XmlConfigurator]. This loads log4net.
Check the log directory has write permissions.
Check the logger has a format specified. This is done by checking each element in your configuration has a layout element specified. Eg:
<appender name="MainLogger"...
<layout type="log4net.Layout.SimpleLayout"/>
Finally, try turning on log4net internal logging to enable console logging and checking the console. To do this, add <add key="log4net.Internal.Debug" value="true"/> to your appSettings.

I've had experiences where logging systems fail silently without raising exceptions. I suppose this makes sense because if the logger is logging errors then how can it log an error that it's unable to perform logging?
So if the file isn't created on disk, start by looking into file system permissions to ensure the user your application is running under can write a new file to that disk location.
For testing purposes you might want to manually create the file on disk that should be written to and open up permissions for everybody to write to it. If the logger starts writing to it then you know it's permission based rather than configuration based.

On my side, I forgot to mark the config file to be copied while the app is being compiled.
Just right click the log4net.config file, select property and then choose Copy to Output Directory to be Copy XXXX

Unfortunately none of the above helped. Explicit configuration in the class to be logged additionaly to the previous settings suggestions did the trick for me.
string assemblyFolder = Path.GetDirectoryName(Assembly.GetExecutingAssembly().Location);
log4net.Config.XmlConfigurator.Configure(new FileInfo(assemblyFolder + "/log4net.config"));

So, in the Accepted Answer, the solution was to put
[assembly: log4net.Config.XmlConfigurator]
into the AssemblyInfo.cs File.
Also, there was a comment sugesting
[assembly: log4net.Config.XmlConfigurator(Watch = true)]
however, if it is still not working, consider configuring the name of your log4net config file (log4net.config in my case):
[assembly: log4net.Config.XmlConfigurator(ConfigFile = "log4net.config")]
after that, logging worked like a charm.

I tried all of the above but nothing worked. Adding this line in app.config's configSections section worked for me.
<section name="log4net" type="log4net.Config.Log4NetConfigurationSectionHandler,log4net, Version=1.2.15.0, Culture=neutral, PublicKeyToken=669e0ddf0bb1aa2a" />
Ensure that Version and PublicKeyToken is correct

<param name="File" value="mylog.log" />
is saying "write mylog.log to actual folder". This means that if your webapp is under IIS, then log will be written to C:\inetpub\wwwroot\appname\mylog.log.
If log file is not there, then maybe account under which is app running doesn't have write permission on folder. You can run Process Monitor from SysInternals to see if and where a file is written.
Also run VS in debug mode, to see if any exceptions are thrown (Debug->Exceptions->CLR Exceptions, check Thrown).

In my case I forget to set the log4Net.config file properties as "Content" so the file was not included in the deploy.
So pay attention on it:
Compile action : Content

Check your Reporting level is set to "Debug" or "ALL".
This caught me and I spent ages trying to debug my log4net setup.
I had it set to Error and as it wasn't erroring it didn't log anything.

Aside from all the other answers, my problem that was I needed a call to GetLogger() in my start-up class (WinForms example):
static class Program
{
public static readonly ILog MainLog = LogManager.GetLogger("Main");
/// <summary>
/// The main entry point for the application.
/// </summary>
[STAThread]
static void Main()
{
Application.EnableVisualStyles();
Application.SetCompatibleTextRenderingDefault(false);
Application.Run(new Form1());
}
}
All my 'meaningful' logging statements were in a DLL that is apparently loaded too late for log4net.

We also had problems with log4net not working and in our case the problem was that the config file had Windows line breaks instead of Unix line breaks.

Also after some hours, I figured out why it wasn't working for me...
i had:
public static class Program
{
private static CommunicationManager _bcScanner = new CommunicationManager();
private static ILog _log = LogManager.GetLogger(typeof(Program));
private static SocketServer socketListener;
but it should be:
public static class Program
{
private static ILog _log = LogManager.GetLogger(typeof(Program));
private static CommunicationManager _bcScanner = new CommunicationManager();
private static SocketServer socketListener;
So make sure the ILog is on the first line....

dynamic log4net appender name?

Let's say i have 3 smtp appenders in same log4net file whose names are:
<appender name = "emailDevelopment".. />
<appender name = "emailBeta".. />
<appender name = "emailProduction".. />
Let's say i have 3 different servers(Dev, Beta, Production). Depending upon the server, i want to fire the log. In case of Development server, it would fire log from "emailDevelopment". I have a system variable in each server named "ApplicationEnvironment" whose value is Development, Beta, Production based on the server names. Now is there anyway i can setup root in log4net so that it fires email depending upon the server name.
<root>
<priority value="ALL" />
<appender-ref ref="email<environment name from whose appender should be used>" />
</root>

This doesn't directly answer your question, but another approach is to simply have multiple log4net configuration files and call XmlConfigurator.Configure() on the right one. For example, you might have Logging.Development.Config, Logging.Beta.Config and so on.
Somewhere in code, you determine the "environment" and configure using the file you want.
I've even gone so far as to have multiple config files and pull different parts of them out into a single XML representing the "true" config, and then calling the Configure() method on that. For example, Logging.Appenders.Config which has all the appenders, and takes all of them and combines it with one of your environment-specific config files above; the environment-specific ones simply reference what they need, and the rest are effectively inactive/unreferenced for that environment.

Even after having written the only XSD file for log4net configuration I'm still not aware of an easy way to achieve this.
You might be able to do something like:
log4net.GlobalContext.Properties["host"] = new ClassThatToStringsHost();
class ClassThatToStringsHost
{ public override string ToString() { return "whatever"; } }
Now you can reference this value from the Log format with: "%property{host}"
To perform the filtering you will need to use a filter configuration in the adapter(s):
<appender name="file" type="log4net.Appender.RollingFileAppender">
<filter type="log4net.Filter.PropertyFilter">
<Key value="host" />
<StringToMatch value="whatever" />
</filter>
<!-- Anything not accepted by the above should be excluded -->
<filter type="log4net.Filter.DenyAllFilter" />
</appender>
There may even be a built-in property you could leverage and this should work. See also this post: http://geekswithblogs.net/rgupta/archive/2009/03/03/dynamic-log-filenames-with-log4net.aspx
For me, myself, and I... I would approach it another way all together. I would derive my own SMTP appender from the default and in the ActivateOptions() method I'd configure the values according to the environment. This would allow you to use one SMTP appender with consistent rules and yet provide three public properties for each of the email addresses you want to send from. It's not hard, give it a try!