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/*
* 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.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}")]
private class ThreadWatchdogInfo
{
public Thread Thread;
public int LastTick;
public ThreadWatchdogInfo(Thread thread)
{
Thread = thread;
LastTick = Environment.TickCount & Int32.MaxValue;
}
}
/// <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)
{
Thread thread = new Thread(start);
thread.Name = name;
thread.Priority = priority;
thread.IsBackground = isBackground;
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 void AddThread(ThreadWatchdogInfo threadInfo)
{
m_log.Debug("[WATCHDOG]: Started tracking thread \"" + threadInfo.Thread.Name + "\" (ID " + threadInfo.Thread.ManagedThreadId + ")");
lock (m_threads)
m_threads.Add(threadInfo.Thread.ManagedThreadId, threadInfo);
}
private static bool RemoveThread(int threadID)
{
lock (m_threads)
return m_threads.Remove(threadID);
}
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;
else
AddThread(new ThreadWatchdogInfo(Thread.CurrentThread));
}
catch { }
}
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 || now - threadInfo.LastTick >= WATCHDOG_TIMEOUT_MS)
{
timedOut = threadInfo;
m_threads.Remove(threadInfo.Thread.ManagedThreadId);
break;
}
}
}
if (timedOut != null)
callback(timedOut.Thread, timedOut.LastTick);
}
m_watchdogTimer.Start();
}
}
}
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