1 files changed, 183 insertions, 0 deletions

diff --git a/OpenSim/Framework/Watchdog.cs b/OpenSim/Framework/Watchdog.cs
new file mode 100644
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+++ b/OpenSim/Framework/Watchdog.cs
@@ -0,0 +1,183 @@
+/*
+ * 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();
+        }
+    }
+}