.Net 下的程序調試相對C/C++要簡單很多,少了那些令人頭疼的指針越界的問題。不過當你的程序遇 到如下問題時,依然非常棘手:
1. 進程異常終止。解決方案見 .Net 下未捕獲異常的處理
2. 內存洩漏或者內存申請後程序始終沒有釋放。解決方案見 用 .NET Memory Profiler 跟蹤.net 應 用內存使用情況--基本應用篇 。如果通過自己編寫的程序監控,我將在以後的文章中闡述。
3. 線程因未知原因掛起,比如死鎖。
4. 程序死循環。
本文將闡述如果編寫程序對後兩者故障實時跟蹤並報告。
首先我們需要一個單獨的監控線程來監控需要監控的線程
我做了一個監控類 ThreadMonitor,在開始監控之前,我們將監控線程的優先級設置為最高。
public ThreadMonitor()
{
_MonitorThread = new Thread(new ThreadStart(MonitorTask));
_MonitorThread.Priority = ThreadPriority.Highest;
_MonitorThread.IsBackground = true;
}
接下來我們為這個線程提供幾個公共方法
Start 方法讓調用者啟動監控
Register 方法用於將需要監控的線程注冊到監控列表中
Heartbeat 方法後面說明
/**//// <summary>
/// Start monitor
/// </summary>
public void Start()
{
_MonitorThread.Start();
}
/**//// <summary>
/// Monitor register
/// </summary>
/// <param name="monitorPara">Monitor parameter</param>
public void Register(MonitorParameter monitorPara)
{
Debug.Assert(monitorPara != null);
Debug.Assert(monitorPara.Thread != null);
if (GetTCB(monitorPara.Thread) != null)
{
throw new System.ArgumentException("Register repeatedly!");
}
lock (_RegisterLock)
{
_TCBTable.Add(monitorPara.Thread.ManagedThreadId, new TCB (monitorPara));
}
}
public void Heartbeat(Thread t)
{
TCB tcb = GetTCB(t);
if (tcb == null)
{
throw new System.ArgumentException("This thread was not registered!");
}
tcb.LastHeartbeat = DateTime.Now;
tcb.HitTimes = 0;
tcb.Status &= ~ThreadStatus.Hang;
}
下面讓我來說說如何監控某個線程掛起。
監控線程提供了一個心跳調用 Heartbeat ,被監控的線程必須設置一個定時器定時向監控線程發送心 跳,如果監控線程在一定時間內無法收到這個心跳消息,則認為被監控線程非正常掛起了。這個時間又 MonitorParameter參數的HangTimeout指定。
光監控到線程掛起還不夠,我們必須要報告線程當前掛起的位置才有實際意義。那麼如何獲得線程當 前的調用位置呢?.Net framework 為我們提供了獲取線程當前堆棧調用回溯的方法。見下面代碼
private string GetThreadStackTrace(Thread t)
{
bool needFileInfo = NeedFileInfo;
t.Suspend();
StackTrace stack = new StackTrace(t, needFileInfo);
t.Resume();
return stack.ToString ();
}
這裡需要說明的是StackTrace(t, needFileInfo) 必須在線程t Suspend後 才能調用,否則會發生異 常。但Thread.Suspend 調用是比較危險的,因為調用者無法知道線程t掛起前的運行狀況,可能線程t目 前正在等待某個資源,這時強制掛起,非常容易造成程序死鎖。不過值得慶幸的是StackTrace(t, needFileInfo)的調用不會和其他線程尤其是調用線程產生資源沖突,但我們必須在這一句執行結束後迅 速調用 t.Resume 結束線程t的掛起狀態。
談完了對線程非正常掛起的監控,再談談對程序死循環的監控。
在決定采用我現在的這個方案之前,我曾經想通過 GetThreadTimes 這個API 函數得到被監控線程的 實際CPU運行時間,通過這個時間來計算其CPU占有率,但很遺憾,我的嘗試失敗了。通過非當前線程下調 用 GetThreadTimes 無法得到對應線程的CPU時間。(好像非托管線程可以,但.Net的托管線程我試了, 確實不行,但原因我還沒弄明白)另外GetThreadTimes 統計不夠准確 見 對老趙寫的簡單性能計數器的 修改續- 關於 GetThreadTimes
所以沒有辦法,我采用了一個不是很理想的方案
定時統計當前進程的TotalProcessorTime 來計算當前線程的CPU占有率,如果這個CPU占有率在一段時 間內大於 100 / (CPU 數)* 90% ,則認為當前進程出現了死循環。這個測試時間由 MonitorParameter參數的DeadCycleTimeout 屬性指定。
這就出現了一個問題,我們只知道程序死循環了,但不知道具體是那個線程死循環,那麼如何找到真 正死循環的線程呢?
我采用的方法是每秒鐘檢測一次線程當前狀態,如果當前狀態為運行狀態則表示命中一次,在確認出 現死循環後我們在來檢查在一個檢查周期內的命中次數,如果這個命中次數足夠高,則認為是該線程死循 環了。不過這樣還是有問題,主線程在等待windows 消息時 或者控制台程序線程在等待控制台輸入時, 該線程的狀態居然始終是 Runing ,其實是阻塞了,但我沒有找到一個很好的方法來得到線程當前處於阻 塞狀態。怎麼辦?我想了個笨辦法,就是在上面兩個條件都符合的情況下再看看在此期間有沒有心跳,如 果沒有心跳,說明死循環了。但如果有心跳也不一定就沒有死循環,遇到這種情況,就將可疑的都全部報 告了,靠人來判斷吧。
我寫了一個示例代碼,代碼中有一個Winform 主線程 和 一個計數器線程,計數器線程每秒記一次數 ,並更新界面。監控線程檢查到非正常掛起或者死循環,將在當前目錄下寫一個Report.log 輸出監控報 告。
點擊Hang後主線程休眠20秒,計數器線程由於要更新界面,也同樣會被掛起。
監控線程檢查到兩個線程掛起後報告如下:
2:38:40 PM
ThreadMonitorEvent
Thread Name:Main thread
Thread Status:Hang
Thread Stack: at System.Threading.Thread.SleepInternal(Int32 millisecondsTimeout)
at System.Threading.Thread.Sleep(Int32 millisecondsTimeout)
at DotNetDebug.Form1.buttonHang_Click(Object sender, EventArgs e)
at System.Windows.Forms.Control.OnClick(EventArgs e)
at System.Windows.Forms.Button.OnClick(EventArgs e)
at System.Windows.Forms.Button.OnMouseUp(MouseEventArgs mevent)
at System.Windows.Forms.Control.WmMouseUp(Message& m, MouseButtons button, Int32 clicks)
at System.Windows.Forms.Control.WndProc(Message& m)
at System.Windows.Forms.ButtonBase.WndProc(Message& m)
at System.Windows.Forms.Button.WndProc(Message& m)
at System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message& m)
at System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m)
at System.Windows.Forms.NativeWindow.DebuggableCallback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)
at System.Windows.Forms.UnsafeNativeMethods.DispatchMessageW(MSG& msg)
at System.Windows.Forms.Application.ComponentManager.System.Windows.Forms.UnsafeNativeMethods.I MsoComponentManager.FPushMessageLoop(Int32 dwComponentID, Int32 reason, Int32 pvLoopData)
at System.Windows.Forms.Application.ThreadContext.RunMessageLoopInner(Int32 reason, ApplicationContext context)
at System.Windows.Forms.Application.ThreadContext.RunMessageLoop(Int32 reason, ApplicationContext context)
at System.Windows.Forms.Application.Run(Form mainForm)
at DotNetDebug.Program.Main()
at System.AppDomain._nExecuteAssembly(Assembly assembly, String[] args)
at System.AppDomain.ExecuteAssembly(String assemblyFile, Evidence assemblySecurity, String[] args)
at Microsoft.VisualStudio.HostingProcess.HostProc.RunUsersAssembly()
at System.Threading.ThreadHelper.ThreadStart_Context(Object state)
at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
at System.Threading.ThreadHelper.ThreadStart()
2:38:40 PM
ThreadMonitorEvent
Thread Name:Counter thread
Thread Status:Hang
Thread Stack: at System.Threading.WaitHandle.WaitOneNative(SafeWaitHandle waitHandle, UInt32 millisecondsTimeout, Boolean hasThreadAffinity, Boolean exitContext)
at System.Threading.WaitHandle.WaitOne(Int64 timeout, Boolean exitContext)
at System.Threading.WaitHandle.WaitOne(Int32 millisecondsTimeout, Boolean exitContext)
at System.Windows.Forms.Control.WaitForWaitHandle(WaitHandle waitHandle)
at System.Windows.Forms.Control.MarshaledInvoke(Control caller, Delegate method, Object[] args, Boolean synchronous)
at System.Windows.Forms.Control.Invoke(Delegate method, Object[] args)
at System.Windows.Forms.Control.Invoke(Delegate method)
at DotNetDebug.Form1.Counter()
at System.Threading.ThreadHelper.ThreadStart_Context(Object state)
at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
at System.Threading.ThreadHelper.ThreadStart()
點擊DeadCycle 按鈕後,讓計數器線程死循環,但主線程不死循環。
監控線程檢查到計數器線程死循環後報告如下:
2:37:51 PM
ThreadMonitorEvent
Thread Name:Counter thread
Thread Status:Hang
Thread Stack: at DotNetDebug.Form1.DoDeadCycle()
at DotNetDebug.Form1.Counter()
at System.Threading.ThreadHelper.ThreadStart_Context(Object state)
at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
at System.Threading.ThreadHelper.ThreadStart()
2:37:52 PM
ThreadMonitorEvent
Thread Name:Counter thread
Thread Status:Hang, DeadCycle
Thread Stack: at DotNetDebug.Form1.DoDeadCycle()
at DotNetDebug.Form1.Counter()
at System.Threading.ThreadHelper.ThreadStart_Context(Object state)
at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
at System.Threading.ThreadHelper.ThreadStart()
下面是示例代碼在
以下是測試代碼。完整源碼的下載位置: 完整源碼
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;
using System.Threading;
using Sys.Diagnostics;
namespace DotNetDebug
{
public partial class Form1 : Form
{
Thread _CounterThread;
ThreadMonitor _ThreadMonitor = new ThreadMonitor();
bool _DeadCycle = false;
delegate void CounterDelegate ();
private void DoDeadCycle()
{
while (_DeadCycle)
{
}
}
private void Counter()
{
int count = 0;
while (true)
{
DoDeadCycle();
labelCounter.Invoke(new CounterDelegate(delegate() { labelCounter.Text = (count++).ToString(); }));
_ThreadMonitor.Heartbeat(Thread.CurrentThread);
Thread.Sleep(1000);
}
}
public Form1()
{
InitializeComponent();
}
void OnThreadMonitorEvent(object sender, ThreadMonitor.ThreadMonitorEvent args)
{
StringBuilder sb = new StringBuilder();
sb.AppendLine(DateTime.Now.ToLongTimeString());
sb.AppendLine("ThreadMonitorEvent");
sb.AppendLine("Thread Name:" + args.Name);
sb.AppendLine("Thread Status:" + args.Status.ToString());
sb.AppendLine("Thread Stack:" + args.StackTrace);
using (System.IO.FileStream fs =
new System.IO.FileStream("report.log", System.IO.FileMode.Append,
System.IO.FileAccess.Write))
{
using (System.IO.StreamWriter sw = new System.IO.StreamWriter(fs))
{
sw.WriteLine(sb.ToString());
}
}
}
private void Form1_Load(object sender, EventArgs e)
{
_ThreadMonitor.ThradMonitorEventHandler +=
new EventHandler<ThreadMonitor.ThreadMonitorEvent> (OnThreadMonitorEvent);
_CounterThread = new Thread(new ThreadStart(Counter));
_CounterThread.IsBackground = true;
_ThreadMonitor.Register(new ThreadMonitor.MonitorParameter(
Thread.CurrentThread, "Main thread", 10000, 5000,
ThreadMonitor.MonitorFlag.MonitorHang |
ThreadMonitor.MonitorFlag.MonitorDeadCycle));
_ThreadMonitor.Register(new ThreadMonitor.MonitorParameter(
_CounterThread, "Counter thread",
ThreadMonitor.MonitorFlag.MonitorHang |
ThreadMonitor.MonitorFlag.MonitorDeadCycle));
_CounterThread.Start();
timerHeartbeat.Interval = 1000;
timerHeartbeat.Enabled = true;
_ThreadMonitor.Start();
}
private void timerHeartBeat_Tick(object sender, EventArgs e)
{
_ThreadMonitor.Heartbeat(Thread.CurrentThread);
}
private void ButtonDeadCycle_Click(object sender, EventArgs e)
{
_DeadCycle = true;
}
private void buttonHang_Click(object sender, EventArgs e)
{
Thread.Sleep(20000);
}
}
}