multithreading - C# lock issues when writing to log

Question

I have a class that programmatically creates a log using the Nlog framework. I have several processes running and creating their logs at the same time. I added a lock to the constructor of the class, as before the two threads were attempting to create a file at the same time which resulted in some annoying bugs (like only creating one log).

This seems to have solved that problem. However now i have the same issue with writing to the log, and using a lock has not helped. Here is the class.

public class CwiLogger
    {
        private Logger _log;
        private static Object createLogLock = new Object();
        private static Object writeLogLock = new Object();
        public CwiLogger(string logPath, string logName, string className)
        {
            lock (createLogLock)
            {
                var config = new LoggingConfiguration();
                var fileTarget = new FileTarget();
                config.AddTarget("file", fileTarget);
                fileTarget.FileName = Path.Combine(logPath, logName);
                fileTarget.Layout = "${longdate}|${level:uppercase=true}|${logger}|${message}";
                var rule = new LoggingRule("*", LogLevel.Debug, fileTarget);
                config.LoggingRules.Add(rule);

                LogManager.Configuration = config;

                this._log = LogManager.GetLogger(className);
            }
        }

        public void AddToLog(string logText, LogLevel level = null)
        {
            lock (writeLogLock)
            {
                level = level ?? LogLevel.Info;
                this._log.Log(level, logText + "
");
            }
        }
    }

In my client code i run two threads each running a process that looks like this:

var log = new CwiLogger(@"C:UsersjmaDocumentsProgrammingJunklogTest", "Log2.txt", "Log2");
for (int i = 0; i < 100; i++)
{
    log.AddToLog("Log2 " + i);
}

only i use log1 for one and log2 for the other.

in my output. One of the 2 logs always sucessfully counts to 99, while the other gets 4-5 in and then has no other output.

Answer 1

Maybe something like this:

public class CwiLogger
{
    private static LoggingConfiguration _logConfig = new LoggingConfiguration();
    private static Object createLogLock = new Object();
    private Logger _log;

    public CwiLogger(string logPath, string logName, string className)
    {
            lock (createLogLock)
            {
                var fileTarget = _logConfig.FindTargetByName(logName);
                if (fileTarget == null)
                {
                    var fileTarget = new FileTarget(logName);
                    fileTarget.FileName = Path.Combine(logPath, logName);
                    fileTarget.Layout = "${longdate}|${level:uppercase=true}|${logger}|${message}";
                    _logConfig.AddTarget(fileTarget);
                    var rule = new LoggingRule(className, LogLevel.Debug, fileTarget) { Final = true };
                    _logConfig.LoggingRules.Add(rule);
                    LogManager.Configuration = _logConfig;
                }
            }
        this._log = LogManager.GetLogger(className);
    }

    public void AddToLog(string logText, LogLevel level = null)
    {
        level = level ?? LogLevel.Info;
        this._log.Log(level, logText + "
");
    }
}

Or maybe steal some ideas from here: https://github.com/NLog/NLog/issues/1998