Add variables to filename of rollingfileappender in Log4Net

Question

Is there a way to make the name of the fileAppender variable? I.e. when I call an action on my controller which takes an object, I would like to write this to a log file. The name of the file would look something like : yyyyMMdd_hhmssms_[controller]_[method].json

this is what I have in my config-file:

<appender name="JsonFileAppender" type="log4net.Appender.RollingFileAppender" >
  <file value="c:\temp\" />
  <datePattern value="yyyyMMdd_hh.mm.ss.ms_%thread{CommonApplicationData}'.json'" />
  <staticLogFileName value="false" />
  <appendToFile value="true" />
  <rollingStyle value="Composite" />
  <maxSizeRollBackups value="10" />
  <maximumFileSize value="5MB" />
  <layout type="log4net.Layout.PatternLayout">
    <param name="ConversionPattern" value="%message%newline" />
  </layout>
</appender>

This returns the following filename : 20160224_01.30.28.3028_P1rea24{Co30onApplicaPionDaPa}.json

http://stackoverflow.com/questions/1535736/how-can-i-change-the-file-location-programmatically — blogprogramisty.net, Feb 24 '16 at 12:22
@stuartd I know, that is wat the customer wants. It's just to log the json that was sent to the api. — Bart Schelkens, Feb 25 '16 at 07:04

score 6 · Answer 1 · answered Feb 24 '16 at 12:31

6

one way is to set an Environment Variable in your code like:

Environment.SetEnvironmentVariable("APPENDER_FILE", "Your File Path");

and then, configure this environment variable in log4net XML:

  <appender name="FileAppender" type="log4net.Appender.FileAppender">
    <file value="${APPENDER_FILE}"/>

answered Feb 24 '16 at 12:31

bkdev

432
4
9

But this means that I need to set that Environment Variable when I configure the logger. So where I write : log4net.Config.XmlConfigurator.Configure() ? – Bart Schelkens Feb 24 '16 at 13:00

score 2 · Accepted Answer · edited Jan 19 '23 at 13:03

You can access the appenders of your log4net configuration at run-time like so

var repository = (Hierarchy)LogManager.GetRepository();
var appenders = repository.GetAppenders().Where(x => x is FileAppender);

You can get specific appender then by name

var appender = appenders.FirstOrDefault(x => x.Name.Equals("MyAppeader"));

Once you have an appender you can modify it how you like. You want to set the filepath

appender.File = @"c:\folder\yyyyMMdd_hhmssms_[controller]_[method].json";

You should not have the do anything else as log4net should automatically start using the new configuration.

Placing this all into a little helper method, you'd get this

public static void SetAppenderPath(string appender, string path)
{
    var repository = (Hierarchy)LogManager.GetRepository();
    var appenders = repository.GetAppenders().Where(x => x is FileAppender);
    var appender = appenders.FirstOfDefault(x => x.Name.Equals(appender));
    
    if (appender == null)
    {
        throw new ConfigurationErrorsException("Appender not found (" + appender + ")");
    }

    appender.File = path;
}

...

LogHelper.SetAppenderPath("MyAppender", @"yyyyMMdd_hhmssms_[controller]_[method].json");

When amending appenders in code you should always call `appender.ActivateOptions()` afterwards: some changes may not require it but others do, so it's good practise to call it every time. — stuartd, Feb 24 '16 at 15:53

Add variables to filename of rollingfileappender in Log4Net

2 Answers2