How to log with a tree like structure

Question

I want to log with log4net (and I am doing this right now) to a file, but with log4net, there are just simple log outputs with a message each line.

Now I want to log to the same log file, but in a tree like structure. For example I've got the following method calls and each method logs its method name (there should be an indentation):

firstMethod().secondMethod().thirdMethod();

Should print this log for example:

2016-07-26 15:44:56,042    > firstMethod
2016-07-26 15:44:56,043         > secondMethod
2016-07-26 15:44:56,044              > thirdMethod
2016-07-26 15:44:56,045              < thirdMethod
2016-07-26 15:44:56,046         < secondMethod
2016-07-26 15:44:56,047    < firstMethod

The < and > signs are printed within the method at the start and at the end of the method.

Answer 1

It is not very efficient but you can look at using the call stack to get the hierarchy of methods and then pad/indent each log entry based on the depth of the call in the call stack.

 StackTrace stackTrace = new StackTrace();          
 StackFrame[] stackFrames = stackTrace.GetFrames();

Alternatives could include using PostSharp or (possibly) writing a custom appender for log4net . Another thought is to forget about indenting and use the full namespace and method name to track where your log entry is coming from. This way you will still get a tree like view.

var methodInfo = System.Reflection.MethodBase.GetCurrentMethod();
var fullName = methodInfo.DeclaringType.FullName + "." + methodInfo.Name;

All that said, it seems like a very a-typical requirement. Do you really need to do this?

Answer 2

How about adding another method for logging with parameter for enter/exit, and do the padding there :

int curLevel = 0;
public void MyLogInfo( bool enter, [System.Runtime.CompilerServices.CallerMemberName] string callingMethod = "", )
{
    string prefix;
    if (enter)
    {
      prefix = "> ";
      curLevel++;
    }
    else
    {
      prefix = "< ";
      curLevel--;
    }
    logger.info(prefix.PadLeft(curLevel+prefix.Length) + callingMethod);
}

You just call MyLogInfo(true) or MyLogInfo(false) - .NET will set the callingMethod name if you do not specify it yourself.

You would have to ensure that you do always call the method on entry/exit of each method you log - maybe check you don't decrement curLevel below zero.

Answer 3

You can use NDC to achieve similar behavior. But it is deprecated. Now, you can use Contexts and Contexts Stacks. Check out this documentation:https://logging.apache.org/log4net/release/manual/contexts.html

You can define multiple stacks (instead of indentation). One stack for a set of behaviors you want to debug. Let's say you want to log creating a Sales Order and its Items. In this example, this stack is defined in ThreadContext. However you can define it in a GlobalContext , LogicalThreadContext or LoggingEvent.

using(log4net.ThreadContext.Stacks["SalesOrderLogic"].Push("SalesOrder"))
{
    log.Info("Created the sales order");

    using(log4net.ThreadContext.Stacks["SalesOrderLogic"].Push("Items"))
    {
        log.Info("Created the sales order items");
    }
}

And then you should add it to your configuration:

<appender name="ConsoleAppender" type="log4net.Appender.ConsoleAppender">
  <layout type="log4net.Layout.PatternLayout">
    <conversionPattern value="%logger - %property{SalesOrderStatus} - [%level]- %message%newline" />
  </layout>
</appender>

DISCLAIMER: I did not test this code.

Note 1: The old NDC will appear in one thread. So if you pushed a message in one thread, it won't appear in another. And it has only one stack unlike the new Context Stack method.

Note 2: Don't forget to checkout Contexts. It is very useful.

Note 3: Also you might find it useful if you research Ninject and log4net working together