<h3><strong>一，您选择用什么样的日志组件</strong></h3>    <p>日志组件，不得不提大名鼎鼎的Log4Net。比较常用的还有 Enterprise Library Logging，ServiceStack Logging。当然您还可以补充，我就只用过这几款。</p>    <p>上边提到的3款日志组件，都要在.config里加代码，特别是Log4Net，还要把SQL写在配置里。我就是仅仅只写个日志，还要配置这么多信息，让人略有不爽。</p>    <p>所以在很长一段时间里，我用下边这个方法写日志：</p>    <pre>  <code class="language-java">          private static void WriteText(string logPath, string logContent)          {              try              {                  if (!File.Exists(logPath))                  {                      File.CreateText(logPath).Close();                  }                  StreamWriter sw = File.AppendText(logPath);                  sw.Write(logContent);                  sw.Close();              }              catch (Exception ex)              {                                }              finally              {                }          }    View Code</code></pre>    <p>这个方法足够的简单，核心代码就只有那么5，6行，还包含容错机制。我就喜欢用这种简单的代码来处理简单的事。</p>    <h3><strong>二，多线程下引爆了问题</strong></h3>    <p>在多线程的情况下，比如100个线程同时需要写日志，上边提到的这个方法就力不从新了。</p>    <p>一个线程访问日志资源，另一个线程再去访问的时候，就会出现异常。</p>    <p>方法一：</p>    <pre>  <code class="language-java">    public static Object _processLock = new Object();        private void Button_Click_1(object sender, RoutedEventArgs e)      {          lock (_processLock)          {            }      }  </code></pre>    <p>方法二：</p>    <pre>  <code class="language-java">    public static Object _processLock = new Object();        private void Button_Click_1(object sender, RoutedEventArgs e)      {          Monitor.Enter(_processLock);          Monitor.Exit(_processLock);      }  </code></pre>    <p>这样，你不得不承认，我已经解决了多线程的问题。</p>    <p>但是有瓶颈，这些需要写日志的线程，必须要等前一个释放了锁资源，后一个线程才能访问的情况。</p>    <h3><strong>三，重新设计日志组件</strong></h3>    <p style="text-align:center"><img src="https://simg.open-open.com/show/453d105cc53dfaf5b9df4bd9c0485fcc.png"></p>    <p>先看图，再说一下我的思路：</p>    <p>1，不管有多少线程同时需要写日志，我都用一个临时队列来存放这些日志信息。</p>    <p>2，再启用一个Task任务把队列的日志 <strong>批量</strong> 存放到.log文件里。</p>    <p>3，附加一个小功能，每个日志存储的大小限制，当日志太大了，查看打开的时候比较慢。</p>    <h3><strong>四，具体的代码实现</strong></h3>    <p>1，在多线程的情况下，我们首先把日志压到Queue队列里</p>    <pre>  <code class="language-java">    static ConcurrentQueue<Tuple<string, string>> logQueue = new ConcurrentQueue<Tuple<string, string>>();  </code></pre>    <p>在这儿，我为什么选用 ConcurrentQueue  而不是  Queue  。因为ConcurrentQueue  表示线程安全的先进先出 (FIFO) 集合。</p>    <p>当然你一定要用Queue也是可以的，但是要自己去实现锁机制，何必自找麻烦呢？</p>    <p>2，把日志队列里的数据，批量持久化到.log文件里</p>    <p>这个问题，让我很头大。我最开始的方法是：</p>    <p><strong>持久化日志方法一：</strong></p>    <p>a，申明一个Task任务，当我Task任务没有实现化时，先实例化，然后再进行持久化日志写入。</p>    <p>b，当我的Task任务，已经实例化了，并且是处于 IsCompleted 状态，我重新实例化Task，再进行持久化日志的写入。</p>    <pre>  <code class="language-java">    static Task writeTask = default(Task);  </code></pre>    <pre>  <code class="language-java">      public static void WriteLog(String customDirectory, String preFile, String infoData)      {          string logPath = GetLogPath(customDirectory, preFile);          string logContent = String.Concat(DateTime.Now, " ", infoData);          logQueue.Enqueue(new Tuple<string, string>(logPath, logContent));            if (writeTask == null)          {              writeTask = new Task((object obj) =>              {                  //pause.WaitOne(1000, true);                  LogRepository();              }                  , null                  , TaskCreationOptions.LongRunning);              writeTask.Start();          }            if (writeTask.IsCompleted)          {                writeTask = new Task((object obj) =>              {                  //pause.WaitOne(1000, true);                  LogRepository();              }                  , null                  , TaskCreationOptions.LongRunning);              writeTask.Start();          }      }    View Code</code></pre>    <p>异常信息：</p>    <p>理论是那么的美好，但是现实是那么残酷，当我跑单元测试的时候，一段时间后总是抛出如下错误。如果是有那位朋友知道其原因，把这个问题解决就完美了。</p>    <p><img src="https://simg.open-open.com/show/2b8795a16096ad1f2d73cf4374085b4b.png"></p>    <p>但是我不能因为这一个异常，导致我这个组件写不下去吧！活人不能被一泡尿给憋死。</p>    <p><strong>持久化日志方法二：</strong></p>    <p>我采用了另外一种方法，在Task任务里我用信号量的方式来解决了些问题，完整代码如下：</p>    <p>static AutoResetEvent pause = new AutoResetEvent(false);</p>    <p>信号量法：</p>    <pre>  <code class="language-java">      public class IOExtention      {          static ConcurrentQueue<Tuple<string, string>> logQueue = new ConcurrentQueue<Tuple<string, string>>();            static Task writeTask = default(Task);            static IOExtention()          {              writeTask = new Task((object obj) =>              {                  while (true)                  {                      pause.WaitOne(1000, true);                      List<string[]> temp = new List<string[]>();                      foreach (var logItem in logQueue)                      {                          string logPath = logItem.Item1;                          string logMergeContent = String.Concat(logItem.Item2, Environment.NewLine, "-----------------------------------------------------------", Environment.NewLine);                          string[] logArr = temp.FirstOrDefault(d => d[0].Equals(logPath));                          if (logArr != null)                          {                              logArr[1] = string.Concat(logArr[1], logMergeContent);                          }                          else                          {                              logArr = new string[] { logPath, logMergeContent };                              temp.Add(logArr);                          }                          Tuple<string, string> val = default(Tuple<string, string>);                          logQueue.TryDequeue(out val);                      }                      foreach (string[] item in temp)                      {                          WriteText(item[0], item[1]);                      }                  }              }              , null              , TaskCreationOptions.LongRunning);              writeTask.Start();          }            public static void WriteLog(String preFile, String infoData)          {              WriteLog(string.Empty, preFile, infoData);          }            static AutoResetEvent pause = new AutoResetEvent(false);          public static void WriteLog(String customDirectory, String preFile, String infoData)          {              string logPath = GetLogPath(customDirectory, preFile);              string logContent = String.Concat(DateTime.Now, " ", infoData);              logQueue.Enqueue(new Tuple<string, string>(logPath, logContent));          }            private static string GetLogPath(String customDirectory, String preFile)          {              string newFilePath = string.Empty;              String logDir = string.IsNullOrEmpty(customDirectory) ? Path.Combine(Environment.CurrentDirectory, "logs") : customDirectory;              if (!Directory.Exists(logDir))              {                  Directory.CreateDirectory(logDir);              }              string extension = ".log";              string fileNameNotExt = String.Concat(preFile, DateTime.Now.ToString("yyyyMMdd"));              String fileName = String.Concat(fileNameNotExt, extension);              string fileNamePattern = string.Concat(fileNameNotExt, "(*)", extension);              List<string> filePaths = Directory.GetFiles(logDir, fileNamePattern, SearchOption.TopDirectoryOnly).ToList();                if (filePaths.Count > 0)              {                  int fileMaxLen = filePaths.Max(d => d.Length);                  string lastFilePath = filePaths.Where(d => d.Length == fileMaxLen).OrderByDescending(d => d).FirstOrDefault();                  if (new FileInfo(lastFilePath).Length > 1 * 1024 * 1024)                  {                      string no = new Regex(@"(?is)(?<=\()(.*)(?=\))").Match(Path.GetFileName(lastFilePath)).Value;                      int tempno = 0;                      bool parse = int.TryParse(no, out tempno);                      string formatno = String.Format("({0})", parse ? (tempno + 1) : tempno);                      string newFileName = String.Concat(fileNameNotExt, formatno, extension);                      newFilePath = Path.Combine(logDir, newFileName);                  }                  else                  {                      newFilePath = lastFilePath;                  }              }              else              {                  string newFileName = String.Concat(fileNameNotExt, String.Format("({0})", 0), extension);                  newFilePath = Path.Combine(logDir, newFileName);              }              return newFilePath;          }            private static void WriteText(string logPath, string logContent)          {              try              {                  if (!File.Exists(logPath))                  {                      File.CreateText(logPath).Close();                  }                  StreamWriter sw = File.AppendText(logPath);                  sw.Write(logContent);                  sw.Close();              }              catch (Exception ex)              {                                }              finally              {                }          }      }    View Code</code></pre>    <p><strong>持久化日志方法三：</strong></p>    <p>如果你感觉写一个日志类还用什么信号量这些技术，太复杂了，那也可以用最简单的方式，定时器来解决。</p>    <p>有同学一听定时器，就默默的笑了，但是这儿的坑也很深，首先了解一下这几个定时器的使用场合，再用不迟！</p>    <p>System.Windows.Threading.DispatcherTimer</p>    <p>System.Windows.Forms.Timer</p>    <p>System.Timers.Timer</p>    <p>System.Threading.Timer</p>    <p>定时器法：</p>    <pre>  <code class="language-java">      public class IOExtention      {          static ConcurrentQueue<Tuple<string, string>> logQueue = new ConcurrentQueue<Tuple<string, string>>();            static System.Timers.Timer logTimers = new System.Timers.Timer();            static IOExtention()          {              logTimers.Interval = 1000;              logTimers.Elapsed += logTimers_Elapsed;              logTimers.AutoReset = true;              logTimers.Enabled = true;          }            public static void WriteLog(String preFile, String infoData)          {              WriteLog(string.Empty, preFile, infoData);          }            public static void WriteLog(String customDirectory, String preFile, String infoData)          {              string logPath = GetLogPath(customDirectory, preFile);              string logContent = String.Concat(DateTime.Now, " ", infoData);              logQueue.Enqueue(new Tuple<string, string>(logPath, logContent));            }            private static string GetLogPath(String customDirectory, String preFile)          {              string newFilePath = string.Empty;              String logDir = string.IsNullOrEmpty(customDirectory) ? Path.Combine(Environment.CurrentDirectory, "logs") : customDirectory;              if (!Directory.Exists(logDir))              {                  Directory.CreateDirectory(logDir);              }              string extension = ".log";              string fileNameNotExt = String.Concat(preFile, DateTime.Now.ToString("yyyyMMdd"));              String fileName = String.Concat(fileNameNotExt, extension);              string fileNamePattern = string.Concat(fileNameNotExt, "(*)", extension);              List<string> filePaths = Directory.GetFiles(logDir, fileNamePattern, SearchOption.TopDirectoryOnly).ToList();                if (filePaths.Count > 0)              {                  int fileMaxLen = filePaths.Max(d => d.Length);                  string lastFilePath = filePaths.Where(d => d.Length == fileMaxLen).OrderByDescending(d => d).FirstOrDefault();                  if (new FileInfo(lastFilePath).Length > 1 * 1024 * 1024)                  {                      string no = new Regex(@"(?is)(?<=\()(.*)(?=\))").Match(Path.GetFileName(lastFilePath)).Value;                      int tempno = 0;                      bool parse = int.TryParse(no, out tempno);                      string formatno = String.Format("({0})", parse ? (tempno + 1) : tempno);                      string newFileName = String.Concat(fileNameNotExt, formatno, extension);                      newFilePath = Path.Combine(logDir, newFileName);                  }                  else                  {                      newFilePath = lastFilePath;                  }              }              else              {                  string newFileName = String.Concat(fileNameNotExt, String.Format("({0})", 0), extension);                  newFilePath = Path.Combine(logDir, newFileName);              }              return newFilePath;          }            static void logTimers_Elapsed(object sender, System.Timers.ElapsedEventArgs e)          {              System.Timers.Timer logTimers = (System.Timers.Timer)sender;              logTimers.Enabled = false;              List<string[]> temp = new List<string[]>();              foreach (var logItem in logQueue)              {                  string logPath = logItem.Item1;                  string logMergeContent = String.Concat(logItem.Item2, Environment.NewLine, "-----------------------------------------------------------", Environment.NewLine);                  string[] logArr = temp.FirstOrDefault(d => d[0].Equals(logPath));                  if (logArr != null)                  {                      logArr[1] = string.Concat(logArr[1], logMergeContent);                  }                  else                  {                      logArr = new string[] { logPath, logMergeContent };                      temp.Add(logArr);                  }                  Tuple<string, string> val = default(Tuple<string, string>);                  logQueue.TryDequeue(out val);              }              foreach (string[] item in temp)              {                  WriteText(item[0], item[1]);              }              logTimers.Enabled = true;          }            private static void WriteText(string logPath, string logContent)          {              try              {                  if (!File.Exists(logPath))                  {                      File.CreateText(logPath).Close();                  }                  StreamWriter sw = File.AppendText(logPath);                  sw.Write(logContent);                  sw.Close();              }              catch (Exception ex)              {                }              finally              {                }          }      }    View Code</code></pre>    <h3><strong>五，结语</strong></h3>    <p>重新设计的日志组件，思路还是非常清晰的。只是在持久化日志时遇上了问题了。</p>    <p>持久化日志方法一，其实是很完美的解决方法，但是在高并发的时候，总是抛出异常，找不出原因。</p>    <p>持久化日志方法二，是我目前采用的方法，能够有效的解决问题。</p>    <p>持久化日志方法三，采用定时器解决，也是可行的。只是代码看起来很别扭。</p>    <p> </p>    <p> </p>    <p>来自：http://www.cnblogs.com/xcj26/p/6037808.html</p>    <p> </p>