aboutsummaryrefslogtreecommitdiffstatshomepage
path: root/OpenSim/Framework/Watchdog.cs
blob: 9baf3a07029f3d1a13b0c2a45314a904bfcb0af8 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
/*
 * 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;
            public int LastTick;

            public ThreadWatchdogInfo(Thread thread)
            {
                Thread = thread;
                LastTick = Environment.TickCount;
            }
        }

        /// <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;
                else
                    AddThread(new ThreadWatchdogInfo(Thread.CurrentThread));
            }
            catch { }
        }
        
        /// <summary>
        /// Get currently watched threads for diagnostic purposes
        /// </summary>
        /// <returns></returns>
        public static ThreadWatchdogInfo[] GetThreads()
        {
            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;

                    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();
        }
    }
}