/* * Copyright (c) Contributors, http://opensimulator.org/ * See CONTRIBUTORS.TXT for a full list of copyright holders. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions are met: * * Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * * Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * * Neither the name of the OpenSimulator Project nor the * names of its contributors may be used to endorse or promote products * derived from this software without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE DEVELOPERS ``AS IS'' AND ANY * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE * DISCLAIMED. IN NO EVENT SHALL THE CONTRIBUTORS BE LIABLE FOR ANY * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. */ using System; using System.Collections.Generic; using System.Linq; using System.Threading; using log4net; namespace OpenSim.Framework { /// <summary> /// Manages launching threads and keeping watch over them for timeouts /// </summary> public static class Watchdog { /// <summary>Timer interval in milliseconds for the watchdog timer</summary> const double WATCHDOG_INTERVAL_MS = 2500.0d; /// <summary>Maximum timeout in milliseconds before a thread is considered dead</summary> const int WATCHDOG_TIMEOUT_MS = 5000; [System.Diagnostics.DebuggerDisplay("{Thread.Name}")] public class ThreadWatchdogInfo { public Thread Thread { get; private set; } /// <summary> /// Approximate tick when this thread was started. /// </summary> /// <remarks> /// Not terribly good since this quickly wraps around. /// </remarks> public int FirstTick { get; private set; } /// <summary> /// First time this heartbeat update was invoked /// </summary> public int LastTick { get; set; } /// <summary> /// Number of milliseconds before we notify that the thread is having a problem. /// </summary> public int Timeout { get; set; } /// <summary> /// Is this thread considered timed out? /// </summary> public bool IsTimedOut { get; set; } public ThreadWatchdogInfo(Thread thread, int timeout) { Thread = thread; Timeout = timeout; FirstTick = Environment.TickCount & Int32.MaxValue; LastTick = FirstTick; } } /// <summary> /// This event is called whenever a tracked thread is stopped or /// has not called UpdateThread() in time /// </summary> /// <param name="thread">The thread that has been identified as dead</param> /// <param name="lastTick">The last time this thread called UpdateThread()</param> public delegate void WatchdogTimeout(Thread thread, int lastTick); /// <summary>This event is called whenever a tracked thread is /// stopped or has not called UpdateThread() in time</summary> public static event WatchdogTimeout OnWatchdogTimeout; private static readonly ILog m_log = LogManager.GetLogger(System.Reflection.MethodBase.GetCurrentMethod().DeclaringType); private static Dictionary<int, ThreadWatchdogInfo> m_threads; private static System.Timers.Timer m_watchdogTimer; static Watchdog() { m_threads = new Dictionary<int, ThreadWatchdogInfo>(); m_watchdogTimer = new System.Timers.Timer(WATCHDOG_INTERVAL_MS); m_watchdogTimer.AutoReset = false; m_watchdogTimer.Elapsed += WatchdogTimerElapsed; m_watchdogTimer.Start(); } /// <summary> /// Start a new thread that is tracked by the watchdog timer. /// </summary> /// <param name="start">The method that will be executed in a new thread</param> /// <param name="name">A name to give to the new thread</param> /// <param name="priority">Priority to run the thread at</param> /// <param name="isBackground">True to run this thread as a background /// thread, otherwise false</param> /// <returns>The newly created Thread object</returns> public static Thread StartThread(ThreadStart start, string name, ThreadPriority priority, bool isBackground) { return StartThread(start, name, priority, isBackground, WATCHDOG_TIMEOUT_MS); } /// <summary> /// Start a new thread that is tracked by the watchdog timer /// </summary> /// <param name="start">The method that will be executed in a new thread</param> /// <param name="name">A name to give to the new thread</param> /// <param name="priority">Priority to run the thread at</param> /// <param name="isBackground">True to run this thread as a background /// thread, otherwise false</param> /// <param name="timeout"> /// Number of milliseconds to wait until we issue a warning about timeout. /// </para> /// <returns>The newly created Thread object</returns> public static Thread StartThread( ThreadStart start, string name, ThreadPriority priority, bool isBackground, int timeout) { Thread thread = new Thread(start); thread.Name = name; thread.Priority = priority; thread.IsBackground = isBackground; ThreadWatchdogInfo twi = new ThreadWatchdogInfo(thread, timeout); m_log.Debug("[WATCHDOG]: Started tracking thread \"" + twi.Thread.Name + "\" (ID " + twi.Thread.ManagedThreadId + ")"); lock (m_threads) m_threads.Add(twi.Thread.ManagedThreadId, twi); thread.Start(); return thread; } /// <summary> /// Marks the current thread as alive /// </summary> public static void UpdateThread() { UpdateThread(Thread.CurrentThread.ManagedThreadId); } /// <summary> /// Stops watchdog tracking on the current thread /// </summary> /// <returns> /// True if the thread was removed from the list of tracked /// threads, otherwise false /// </returns> public static bool RemoveThread() { return RemoveThread(Thread.CurrentThread.ManagedThreadId); } private static bool RemoveThread(int threadID) { lock (m_threads) return m_threads.Remove(threadID); } public static bool AbortThread(int threadID) { lock (m_threads) { if (m_threads.ContainsKey(threadID)) { ThreadWatchdogInfo twi = m_threads[threadID]; twi.Thread.Abort(); RemoveThread(threadID); return true; } else { return false; } } } private static void UpdateThread(int threadID) { ThreadWatchdogInfo threadInfo; // Although TryGetValue is not a thread safe operation, we use a try/catch here instead // of a lock for speed. Adding/removing threads is a very rare operation compared to // UpdateThread(), and a single UpdateThread() failure here and there won't break // anything try { if (m_threads.TryGetValue(threadID, out threadInfo)) { threadInfo.LastTick = Environment.TickCount & Int32.MaxValue; threadInfo.IsTimedOut = false; } else { m_log.WarnFormat("[WATCHDOG]: Asked to update thread {0} which is not being monitored", threadID); } } catch { } } /// <summary> /// Get currently watched threads for diagnostic purposes /// </summary> /// <returns></returns> public static ThreadWatchdogInfo[] GetThreads() { lock (m_threads) return m_threads.Values.ToArray(); } private static void WatchdogTimerElapsed(object sender, System.Timers.ElapsedEventArgs e) { WatchdogTimeout callback = OnWatchdogTimeout; if (callback != null) { ThreadWatchdogInfo timedOut = null; lock (m_threads) { int now = Environment.TickCount & Int32.MaxValue; foreach (ThreadWatchdogInfo threadInfo in m_threads.Values) { if (threadInfo.Thread.ThreadState == ThreadState.Stopped) { timedOut = threadInfo; RemoveThread(threadInfo.Thread.ManagedThreadId); break; } else if (!threadInfo.IsTimedOut && now - threadInfo.LastTick >= threadInfo.Timeout) { threadInfo.IsTimedOut = true; timedOut = threadInfo; break; } } } if (timedOut != null) callback(timedOut.Thread, timedOut.LastTick); } m_watchdogTimer.Start(); } } }