c# 编写一个轻量级的异步写日志的实用工具类（LogAsyncWriter）

一说到写日志，大家可能推荐一堆的开源日志框架，如：Log4Net、NLog，这些日志框架确实也不错，比较强大也比较灵活，但也正因为又强大又灵活，导致我们使用他们时需要引用一些DLL，同时还要学习各种用法及配置文件，这对于有些小工具、小程序、小网站来说，有点“杀鸡焉俺用牛刀”的感觉，而且如果对这些日志框架不了解，可能输出来的日志性能或效果未毕是与自己所想的，鉴于这几个原因，我自己重复造轮子，编写了一个轻量级的异步写日志的实用工具类（LogAsyncWriter），这个类还是比较简单的，实现思路也很简单，就是把消息日志先入内存队列，然后由异步监听线程从队列中取出日志并批量输出到本地文件中，同时参照各大日志框架，对单个文件过大采取分割生成多个日志文件。

经测试发现性能非常不错，先看示例使用代码：（采取并发多线程同时写入1000000万条日志）

    Task.Factory.StartNew(() =>
    {
        DateTime startTime = DateTime.Now;
        int logCount = 1000000;
        Parallel.For(1, logCount, (i) =>
        {
            if (i % 2 == 0)
            {
                LogAsyncWriter.Default.Error("测试并发写错误日志-" + i.ToString(), "TestClass.TestLog", i.ToString());
            }
            else
            {
                LogAsyncWriter.Default.Info("测试并发写普通日志-" + i.ToString(), "TestClass.TestLog", i.ToString());
            }
        });
 
        this.Invoke(new MethodInvoker(() =>
        {
            MessageBox.Show(DateTime.Now.ToString() + "," + logCount + "条日志写完了！，耗时：" + (DateTime.Now - startTime).TotalMilliseconds + "ms");
        }));
    });
 
    MessageBox.Show(DateTime.Now.ToString() + ",同步方法已结束");
}

　执行效果如下图示：

因为采用异步，故方法先走到结尾，输出了同步的MsgBox，随后弹出的是100W日志输出到文件后的耗时MsgBox,从截图可以看出，不足1S(当然这里的1S不是真实的输出到本地方件，而是把所有的日志推到了Queue中而矣，但不影响不阻塞业务处理)，而本地日志文件的大小达到了263MB（设置最大值的MaxSizeBackup，使其不滚动备份），由此看性能是不错的；

因为是异步延迟输出到本地日志文件，故大家在代码中任意地方，比如：循环中都可以使用它，不用担心会影响你的正常的业务逻辑的执行效率；

如果采取滚动备份（设置MaxSizeBackup为一个合理值，默认为10MB），则生成的日志文件形式如下：（超过最大容量则生成同名文件+2位序号）,超过一个月则会自动清除

打开日志文件会看到所有的日志内容：

有些人可能要问，输出格式是固定的吗？能否自定义布局，告诉你是可以的，我考虑到每个人对日志输出的格式都有严格的要求，故可以通过设置：LineLayoutRenderFormat属性来设置每条日志输出的格式内容

好了，介绍了使用功能及效果、性能，下面贴出源代码：

using System;
using System.Collections.Concurrent;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Text;
using System.Threading;
using System.Threading.Tasks;
using System.Text.RegularExpressions;
 
namespace Zuowj.Common
{
    /// <summary>
    /// 日志异步生成器
    /// Author:Zuowenjun(http://www.zuowenjun.cn)
    /// Date:2018-6-14
    /// </summary>
    public class LogAsyncWriter
    {
        public const string InfoLevel = "INFO";
        public const string WarnLevel = "WARN";
        public const string ErrorLevel = "ERROR";
 
        private readonly ConcurrentQueue<string[]> logMsgQueue = new ConcurrentQueue<string[]>();
        private readonly CancellationTokenSource cts = null;
        private string lineLayoutRenderFormat = "[{0:yyyy-MM-dd HH:mm:ss}]\t{1}\t{2}\t{3}：{4}，Trace：{5}；Other1：{6}，Other2：{7}，Other3：{8}";
        private long maxSizeBackup = 10485760L;//默认10MB
        private string todayLogName = null;
 
        private static readonly LogAsyncWriter instance = new LogAsyncWriter();
 
 
        private LogAsyncWriter()
        {
            cts = new CancellationTokenSource();
            ListenSaveLogAsync(cts.Token);
        }
 
        private void ListenSaveLogAsync(CancellationToken cancellationToken)
        {
            Task.Factory.StartNew(() =>
            {
                DateTime lastSaveLogTime = DateTime.Now;
                while (!cancellationToken.IsCancellationRequested)//如果没有取消线程，则一直监听执行写LOG
                {
                    if (logMsgQueue.Count >= 10 || (logMsgQueue.Count > 0 && (DateTime.Now - lastSaveLogTime).TotalSeconds > 30))//如是待写日志消息累计>=10条或上一次距离现在写日志时间超过30s则需要批量提交日志
                    {
                        List<string[]> logMsgList = new List<string[]>();
                        string[] logMsgItems = null;
 
                        while (logMsgList.Count < 10 && logMsgQueue.TryDequeue(out logMsgItems))
                        {
                            logMsgList.Add(logMsgItems);
                        }
 
                        WriteLog(logMsgList);
 
                        lastSaveLogTime = DateTime.Now;
                    }
                    else
                    {
                        SpinWait.SpinUntil(() => logMsgQueue.Count >= 10, 5000);//自旋等待直到日志队列有>=10的记录或超时5S后再进入下一轮的判断
                    }
                }
            }, cancellationToken);
        }
 
        private string GetLogFilePath()
        {
            string logFileDir = Path.Combine(AppDomain.CurrentDomain.BaseDirectory, "Logs");
            if (!Directory.Exists(logFileDir))
            {
                Directory.CreateDirectory(logFileDir);
            }
 
            string logDateStr = DateTime.Now.ToString("yyyyMMdd");
            string logName = logDateStr;
            if (!string.IsNullOrEmpty(todayLogName) && todayLogName.StartsWith(logName))
            {
                logName = todayLogName;
            }
            else
            {
                todayLogName = logName;
            }
 
            string logFilePath = Path.Combine(logFileDir, logName + ".log");
 
            if (File.Exists(logFilePath))
            {
                File.SetAttributes(logFilePath, FileAttributes.Normal);
                if (File.GetLastWriteTime(logFilePath).Month != DateTime.Today.Month) //30天滚动(删除旧的文件)，防止日志文件过多
                {
                    File.Delete(logFilePath);
                    string[] oldLogFiles = Directory.GetFiles(logFileDir, string.Format("{0}-##.log", logDateStr), SearchOption.TopDirectoryOnly);
                    foreach (string fileName in oldLogFiles)
                    {
                        File.SetAttributes(fileName, FileAttributes.Normal);
                        File.Delete(fileName);
                    }
                }
                else if (new FileInfo(logFilePath).Length > MaxSizeBackup)
                {
                    Regex rgx = new Regex(@"^\d{8}-(?<fnum>\d{2})$");
                    int fnum = 2;
                    if (rgx.IsMatch(logName))
                    {
                        fnum = int.Parse(rgx.Match(logName).Groups["fnum"].Value) + 1;
                    }
 
                    logName = string.Format("{0}-{1:D2}", logDateStr, fnum);
                    todayLogName = logName;
                    logFilePath = Path.Combine(logFileDir, logName + ".log");
                }
            }
 
            return logFilePath;
        }
 
        private void WriteLog(IEnumerable<string[]> logMsgs)
        {
            try
            {
                List<string> logMsgLines = new List<string>();
                foreach (var logMsgItems in logMsgs)
                {
                    var logMsgLineFields = (new object[] { DateTime.Now }).Concat(logMsgItems).ToArray();
                    string logMsgLineText = string.Format(LineLayoutRenderFormat, logMsgLineFields);
                    logMsgLines.Add(logMsgLineText);
                }
 
                string logFilePath = GetLogFilePath();
                File.AppendAllLines(logFilePath, logMsgLines);
            }
            catch
            { }
        }
 
 
 
        public static LogAsyncWriter Default
        {
            get
            {
                return instance;
            }
        }
 
        public string LineLayoutRenderFormat
        {
            get { return lineLayoutRenderFormat; }
            set
            {
                if (string.IsNullOrWhiteSpace(value))
                {
                    throw new ArgumentException("无效的LineLayoutRenderFormat属性值");
                }
 
                lineLayoutRenderFormat = value;
            }
        }
 
        public long MaxSizeBackup
        {
            get { return maxSizeBackup; }
            set
            {
                if (value <= 0)
                {
                    throw new ArgumentException("无效的MaxSizeBackup属性值");
                }
 
                maxSizeBackup = value;
            }
        }
 
        public void SaveLog(string logLevel, string msg, string source, string detailTrace = null, string other1 = null, string other2 = null, string other3 = null)
        {
            logMsgQueue.Enqueue(new[] { logLevel, Thread.CurrentThread.ManagedThreadId.ToString(), source, msg, detailTrace ?? string.Empty, other1 ?? string.Empty, other2 ?? string.Empty, other3 ?? string.Empty });
        }
 
        public void Info(string msg, string source, string detailTrace = null, string other1 = null, string other2 = null, string other3 = null)
        {
            SaveLog(InfoLevel, msg, source, detailTrace, other1, other2, other3);
        }
 
        public void Warn(string msg, string source, string detailTrace = null, string other1 = null, string other2 = null, string other3 = null)
        {
            SaveLog(WarnLevel, msg, source, detailTrace, other1, other2, other3);
        }
 
        public void Error(string msg, string source, string detailTrace = null, string other1 = null, string other2 = null, string other3 = null)
        {
            SaveLog(ErrorLevel, msg, source, detailTrace, other1, other2, other3);
        }
 
        public void Error(Exception ex, string source, string other1 = null, string other2 = null, string other3 = null)
        {
            SaveLog(ErrorLevel, ex.Message, source, ex.StackTrace, other1, other2, other3);
        }
 
        ~LogAsyncWriter()
        {
            cts.Cancel();
        }
 
    }
}

代码重点说明：

1.各种日志方法入参解释：

i. Msg:日志消息（一般是指简要消息）
ii. Source:日志产生源（一般是指该日志是由哪个位置产生的，可以定义为：类.方法名）
iii. detailTrace:日志详情（一般是指堆栈信息或日志更具体的信息）
iv. other1, other2, other3:备用日志字段，可根据实际情况记录相关信息，比如：入参、返参，执行耗时等；
v. log Level：日志消息级别一般有很多级别，但常用的只有3类，即：Info=普通日志消息，Warn=警告日志消息,Error=错误日志消息；

2.核心异步批量写日志的方法：（采用后台线程监听日志消息队列，当达到10条日志消息或写日志的时间间隔超过1分钟，则会批量提交1次日志，解决了普通的同步写日志方法造成写压力过大，且存在阻塞业务逻辑的情况）

3.采用单例模式，当第一次使用该类时，则会启动异步监听线程，当该类释放时（一般指应用进程关闭时，会发送通知线程取消监听，避免一切可能的线程驻留问题）

好了就介绍到这里，大家若想试用或想改造，可以直接复制上述代码，不足之处可以指出，谢谢！

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