为了避免多个Process对同一个log文件写入而引发文件锁定或者相互覆盖而出现log内容遗失问题，上一篇使用Buffer来解决，这一篇用MSMQ。

2年多前参加国内某航空公司系统转换项目的教育训练，当时架构师规划的log就用上了MSMQ。

每一台ap都将log写到自己的MSMQ，然后独立的Log Server 每隔一段时间来收，这样就可以将log集中管理，又免去临时通讯中断的问题。

1.首先要在Windows 启用MSMQ并建立MSMQ Private Queue，可以参考以下两篇:

[Powershell]启用Windows Server MSMQ功能(消息队列)

[Powershell]建立MSMQ(消息队列)设定

假设我们已经按照上面建立了名称为logqueue的private queue

2.log4net有一个msmq的sample code可以使用

打开前一篇的Visual Studio项目，新增一支class:  MsmqAppender.cs

#region Apache License
//
// Licensed to the Apache Software Foundation (ASF) under one or more 
// contributor license agreements. See the NOTICE file distributed with
// this work for additional information regarding copyright ownership. 
// The ASF licenses this file to you under the Apache License, Version 2.0
// (the "License"); you may not use this file except in compliance with 
// the License. You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//
#endregion

using System;
using System.Messaging;

using log4net.Core;

namespace Appender
{
	/// 

	/// Appender writes to a Microsoft Message Queue
	/// 
	/// 
  
  
   
   
	/// This appender sends log events via a specified MSMQ queue.
	/// The queue specified in the QueueName (e.g. .Private$log-test) must already exist on
	/// the source machine.
	/// The message label and body are rendered using separate layouts.
	/// 
  
  
	public class MsmqAppender : log4net.Appender.AppenderSkeleton
	{
		private MessageQueue m_queue;
		private string m_queueName;
		private log4net.Layout.PatternLayout m_labelLayout;

		public MsmqAppender()
		{
		}

		public string QueueName
		{
			get { return m_queueName; }
			set { m_queueName = value; }
		}

		public log4net.Layout.PatternLayout LabelLayout
		{
			get { return m_labelLayout; }
			set { m_labelLayout = value; }
		}

		override protected void Append(LoggingEvent loggingEvent) 
		{
			if (m_queue == null)
			{
				if (MessageQueue.Exists(m_queueName))
				{
					m_queue = new MessageQueue(m_queueName);
				}
				else
				{
					ErrorHandler.Error("Queue ["+m_queueName+"] not found");
				}
			}

			if (m_queue != null)
			{
				Message message = new Message();

				message.Label = RenderLabel(loggingEvent);

				using(System.IO.MemoryStream stream = new System.IO.MemoryStream())
				{
					System.IO.StreamWriter writer = new System.IO.StreamWriter(stream, new System.Text.UTF8Encoding(false, true));
					base.RenderLoggingEvent(writer, loggingEvent);
					writer.Flush();
					stream.Position = 0;
					message.BodyStream = stream;

					m_queue.Send(message);
				}
			}
		}

		private string RenderLabel(LoggingEvent loggingEvent)
		{
			if (m_labelLayout == null)
			{
				return null;
			}

			System.IO.StringWriter writer = new System.IO.StringWriter();
			m_labelLayout.Format(writer, loggingEvent);

			return writer.ToString();
		}
	}
}

3.接着设定log4net.config

4.测试程序: 执行1,000次写log

private static readonly ILog Logger = LogManager.GetLogger(typeof(testLog4net));
[TestMethod]
public void TestMethod1()
{
    XmlConfigurator.Configure(new FileInfo(string.Format(@"{0}{1}",
        Directory.GetParent(Directory.GetParent(Environment.CurrentDirectory).FullName),
        "log4net.config")));
    Stopwatch sw = new Stopwatch();
    sw.Start();
    for (int i = 0; i < 1000; i++)
    {
        Logger.Debug(string.Format("this is no{0} log", i + 1));
    }
    sw.Stop();
    Console.WriteLine("总耗时(ElapsedMilliseconds) = " + sw.ElapsedMilliseconds);
}

测试结果: 1,000笔log 1.721秒，速度可!

Private queueslogqueue果然也出现1,000笔log queues

小结:

• 从MQViewer可以发现，log4net写出的log是xml格式，再找时间再改写成json格式的log entry。
• 这一篇先笔记将log写到MSMQ，下一篇再笔记从MSMQ读出，然后写到Log File。

参考:

sample appender

log4net

msmq sample code

原文:大专栏  [.NET][Log4net]解决FileAppender+MinimalLock性能问题(二)(MSMQ)