NLog MemoryTarget maximum size - nlog

Question

Since I have a global exception handler that reports uncaught errors via e-mail, next step is to add some context to it by having some 10-20 last lines of log that are collected.
So I am using MemoryTarget like so:
MemoryTarget _logTarget;
_logTarget = new MemoryTarget();
_logTarget.Layout = "${longdate}|${level:uppercase=true}|${logger}|${message}${exception}";
LoggingRule loggingRule = new LoggingRule("*", LogLevel.Debug, _logTarget);
LogManager.Configuration.AddTarget("exceptionMemory", _logTarget);
LogManager.Configuration.LoggingRules.Add(loggingRule);
LogManager.Configuration.Reload();
Apps containing this should run forever, and if I leave logs in memory, unchecked, I'll have neatly designed memory leak.
How to address this? How to truncate MemoryTarget.Logs to have at most say 100 lines?

Answer 1

Your best bet is probably to write your own MemoryTarget... Something like this (untested) should work.
namespace NLog.Targets
{
using System.Collections.Generic;
[Target("LimitedMemory")]
public sealed class LimitedMemoryTarget : TargetWithLayout
{
private Queue<string> logs = new Queue<string>();
public LimitedMemoryTarget()
{
this.Logs = new List<string>();
}
public IEnumerable<string> Logs
{
get { return logs; }
private set { logs = value; }
}
[DefaultValue(100)]
public int Limit { get; set; }
protected override void Write(LogEventInfo logEvent)
{
string msg = this.Layout.Render(logEvent);
logs.Enqueue(msg);
if (logs.Count > Limit)
{
logs.Dequeue();
}
}
}
}
This example is based on the NLog MemoryTarget, the source code for which you can find here:
https://github.com/NLog/NLog
NLog docs are here:
http://nlog-project.org/documentation/v2.0.1/
I didn't see anything like you are asking about in either location.