Add experimental OutgoingQueueRefillEngine to handle queue refill processing on a controlled number of threads rather than the threadpool.

Disabled by default.  Currently can only be enabled with console "debug lludp oqre start" command, though this can be started and stopped whilst simulator is running.
When a connection requires packet queue refill processing (used to populate queues with entity updates, entity prop updates and image queue updates), this is done via Threadpool requests.
However, with a very high number of connections (e.g. 100 root + 300 child) a very large number of simultaneous requests may be causing performance issues.
This commit adds an experimental engine for processing these requests from a queue with a persistent thread instead.
Unlike inbound processing, there are no network requests in this processing that might hold the thread up for a long time.
Early implementation - currently only one thread which may (or may not) get overloaded with requests.  Added for testing purposes.

3 files changed, 288 insertions, 5 deletions

diff --git a/OpenSim/Region/ClientStack/Linden/UDP/LLUDPClient.cs b/OpenSim/Region/ClientStack/Linden/UDP/LLUDPClient.cs
index 2f363f4..c34bafa 100644
--- a/OpenSim/Region/ClientStack/Linden/UDP/LLUDPClient.cs
+++ b/OpenSim/Region/ClientStack/Linden/UDP/LLUDPClient.cs
@@ -650,8 +650,15 @@ namespace OpenSim.Region.ClientStack.LindenUDP
 
                 if (HasUpdates(m_categories))
                 {
-                    // Asynchronously run the callback
-                    Util.FireAndForget(FireQueueEmpty, categories);
+                    if (!m_udpServer.OqrEngine.IsRunning)
+                    {
+                        // Asynchronously run the callback
+                        Util.FireAndForget(FireQueueEmpty, categories);
+                    }
+                    else
+                    {
+                        m_udpServer.OqrEngine.QueueRequest(this, categories);
+                    }
                 }
                 else
                 {
@@ -670,7 +677,7 @@ namespace OpenSim.Region.ClientStack.LindenUDP
         /// <param name="o">Throttle categories to fire the callback for,
         /// stored as an object to match the WaitCallback delegate
         /// signature</param>
-        private void FireQueueEmpty(object o)
+        public void FireQueueEmpty(object o)
         {
 //            m_log.DebugFormat("[LLUDPCLIENT]: FireQueueEmpty for {0} in {1}", AgentID, m_udpServer.Scene.Name);
 
diff --git a/OpenSim/Region/ClientStack/Linden/UDP/LLUDPServer.cs b/OpenSim/Region/ClientStack/Linden/UDP/LLUDPServer.cs
index 465c86b..3c9bb1b 100644
--- a/OpenSim/Region/ClientStack/Linden/UDP/LLUDPServer.cs
+++ b/OpenSim/Region/ClientStack/Linden/UDP/LLUDPServer.cs
@@ -355,6 +355,13 @@ namespace OpenSim.Region.ClientStack.LindenUDP
         /// </summary>
         private IClientAPI m_currentIncomingClient;
 
+        /// <summary>
+        /// Experimental facility to run queue empty processing within a controlled number of threads rather than
+        /// requiring massive numbers of short-lived threads from the threadpool when there are a high number of 
+        /// connections.
+        /// </summary>
+        public OutgoingQueueRefillEngine OqrEngine { get; private set; }
+
         public LLUDPServer(
             IPAddress listenIP, ref uint port, int proxyPortOffsetParm, bool allow_alternate_port,
             IConfigSource configSource, AgentCircuitManager circuitManager)
@@ -432,6 +439,8 @@ namespace OpenSim.Region.ClientStack.LindenUDP
 
             if (usePools)
                 EnablePools();
+
+            OqrEngine = new OutgoingQueueRefillEngine(this);
         }
 
         public void Start()
@@ -469,7 +478,7 @@ namespace OpenSim.Region.ClientStack.LindenUDP
 
             Watchdog.StartThread(
                 OutgoingPacketHandler,
-                string.Format("Outgoing Packets ({0})", Scene.RegionInfo.RegionName),
+                string.Format("Outgoing Packets ({0})", Scene.Name),
                 ThreadPriority.Normal,
                 false,
                 true,
@@ -479,7 +488,7 @@ namespace OpenSim.Region.ClientStack.LindenUDP
 
         public void Stop()
         {
-            m_log.Info("[LLUDPSERVER]: Shutting down the LLUDP server for " + Scene.RegionInfo.RegionName);
+            m_log.Info("[LLUDPSERVER]: Shutting down the LLUDP server for " + Scene.Name);
             base.StopOutbound();
             base.StopInbound();
         }
diff --git a/OpenSim/Region/ClientStack/Linden/UDP/OutgoingQueueRefillEngine.cs b/OpenSim/Region/ClientStack/Linden/UDP/OutgoingQueueRefillEngine.cs
new file mode 100644
index 0000000..8777402
--- /dev/null
+++ b/OpenSim/Region/ClientStack/Linden/UDP/OutgoingQueueRefillEngine.cs
@@ -0,0 +1,267 @@
+/*
+ * 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.Concurrent;
+using System.Reflection;
+using System.Threading;
+using log4net;
+using OpenSim.Framework;
+using OpenSim.Framework.Monitoring;
+using OpenSim.Region.Framework.Scenes;
+
+namespace OpenSim.Region.ClientStack.LindenUDP
+{
+    public struct RefillRequest
+    {
+        public LLUDPClient Client;
+        public ThrottleOutPacketTypeFlags Categories;
+
+        public RefillRequest(LLUDPClient client, ThrottleOutPacketTypeFlags categories)
+        {
+            Client = client;
+            Categories = categories;
+        }
+    }
+
+    public class OutgoingQueueRefillEngine
+    {
+        private static readonly ILog m_log = LogManager.GetLogger(MethodBase.GetCurrentMethod().DeclaringType);
+
+        public bool IsRunning { get; private set; } 
+
+        /// <summary>
+        /// The timeout in milliseconds to wait for at least one event to be written when the recorder is stopping.
+        /// </summary>
+        public int RequestProcessTimeoutOnStop { get; set; }
+
+        /// <summary>
+        /// Controls whether we need to warn in the log about exceeding the max queue size.
+        /// </summary>
+        /// <remarks>
+        /// This is flipped to false once queue max has been exceeded and back to true when it falls below max, in 
+        /// order to avoid spamming the log with lots of warnings.
+        /// </remarks>
+        private bool m_warnOverMaxQueue = true;
+
+        private BlockingCollection<RefillRequest> m_requestQueue;
+
+        private CancellationTokenSource m_cancelSource = new CancellationTokenSource();
+
+        private LLUDPServer m_udpServer;
+
+        /// <summary>
+        /// Used to signal that we are ready to complete stop.
+        /// </summary>
+        private ManualResetEvent m_finishedProcessingAfterStop = new ManualResetEvent(false);
+
+        public OutgoingQueueRefillEngine(LLUDPServer server)
+        {
+            RequestProcessTimeoutOnStop = 5000;
+            m_udpServer = server;
+
+            MainConsole.Instance.Commands.AddCommand(
+                "Debug",
+                false,
+                "debug lludp oqre",
+                "debug lludp oqre <start|stop|status>",
+                "Start, stop or get status of OutgoingQueueRefillEngine.",
+                "Experimental.",
+                HandleOqreCommand);
+        }
+
+        public void Start()
+        {
+            lock (this)
+            {
+                if (IsRunning)
+                    return;
+
+                IsRunning = true;
+
+                m_finishedProcessingAfterStop.Reset();
+
+                m_requestQueue = new BlockingCollection<RefillRequest>(new ConcurrentQueue<RefillRequest>(), 5000);
+
+                Watchdog.StartThread(
+                    ProcessRequests,
+                    String.Format("OutgoingQueueRefillEngineThread ({0})", m_udpServer.Scene.Name),
+                    ThreadPriority.Normal,
+                    false,
+                    true,
+                    null,
+                    int.MaxValue);
+            }
+        }
+
+        public void Stop()
+        {   
+            lock (this)
+            {
+                try
+                {
+                    if (!IsRunning)
+                        return;
+
+                    IsRunning = false;
+
+                    int requestsLeft = m_requestQueue.Count;
+
+                    if (requestsLeft <= 0)
+                    {
+                        m_cancelSource.Cancel();
+                    }
+                    else 
+                    {
+                        m_log.InfoFormat("[OUTGOING QUEUE REFILL ENGINE]: Waiting to write {0} events after stop.", requestsLeft);
+
+                        while (requestsLeft > 0)
+                        {
+                            if (!m_finishedProcessingAfterStop.WaitOne(RequestProcessTimeoutOnStop))
+                            {
+                                // After timeout no events have been written
+                                if (requestsLeft == m_requestQueue.Count)
+                                {
+                                    m_log.WarnFormat(
+                                        "[OUTGOING QUEUE REFILL ENGINE]: No requests processed after {0} ms wait.  Discarding remaining {1} requests", 
+                                        RequestProcessTimeoutOnStop, requestsLeft);
+
+                                    break;
+                                }
+                            }
+
+                            requestsLeft = m_requestQueue.Count;
+                        }
+                    }
+                }
+                finally
+                {
+                    m_cancelSource.Dispose();
+                    m_requestQueue = null;
+                }
+            }
+        }
+
+        public bool QueueRequest(LLUDPClient client, ThrottleOutPacketTypeFlags categories)
+        {
+            if (m_requestQueue.Count < m_requestQueue.BoundedCapacity)
+            {
+//                m_log.DebugFormat(
+//                    "[OUTGOING QUEUE REFILL ENGINE]: Adding request for categories {0} for {1} in {2}", 
+//                    categories, client.AgentID, m_udpServer.Scene.Name);
+
+                m_requestQueue.Add(new RefillRequest(client, categories));
+
+                if (!m_warnOverMaxQueue)
+                    m_warnOverMaxQueue = true;
+
+                return true;
+            }
+            else
+            {
+                if (m_warnOverMaxQueue)
+                {
+                    m_log.WarnFormat(
+                        "[OUTGOING QUEUE REFILL ENGINE]: Request queue at maximum capacity, not recording request from {0} in {1}", 
+                        client.AgentID, m_udpServer.Scene.Name);
+
+                    m_warnOverMaxQueue = false;
+                }
+
+                return false;
+            }
+        }
+
+        private void ProcessRequests()
+        {
+            try
+            {
+                while (IsRunning || m_requestQueue.Count > 0)
+                {
+                    RefillRequest req = m_requestQueue.Take(m_cancelSource.Token);
+
+    //                QueueEmpty callback = req.Client.OnQueueEmpty;                      
+    //
+    //                if (callback != null)
+    //                {               
+    //                    try 
+    //                    { 
+    //                        callback(req.Categories); 
+    //                    }
+    //                    catch (Exception e) 
+    //                    { 
+    //                        m_log.Error("[OUTGOING QUEUE REFILL ENGINE]: ProcessRequests(" + req.Categories + ") threw an exception: " + e.Message, e); 
+    //                    }
+    //                }
+
+                    req.Client.FireQueueEmpty(req.Categories);
+                }
+            }
+            catch (OperationCanceledException)
+            {
+            }
+
+            m_finishedProcessingAfterStop.Set();
+        }
+
+        private void HandleOqreCommand(string module, string[] args)
+        {
+            if (SceneManager.Instance.CurrentScene != null && SceneManager.Instance.CurrentScene != m_udpServer.Scene)
+                return;
+
+            if (args.Length != 4)
+            {
+                MainConsole.Instance.Output("Usage: debug lludp oqre <stop|start|status>");
+                return;
+            }
+
+            string subCommand = args[3];
+
+            if (subCommand == "stop")
+            {
+                Stop();
+                MainConsole.Instance.OutputFormat("Stopped OQRE for {0}", m_udpServer.Scene.Name);
+            }
+            else if (subCommand == "start")
+            {
+                Start();
+                MainConsole.Instance.OutputFormat("Started OQRE for {0}", m_udpServer.Scene.Name);
+            }
+            else if (subCommand == "status")
+            {
+                MainConsole.Instance.OutputFormat("OQRE in {0}", m_udpServer.Scene.Name);
+                MainConsole.Instance.OutputFormat("Running: {0}", IsRunning);
+                MainConsole.Instance.OutputFormat(
+                    "Requests waiting: {0}", IsRunning ? m_requestQueue.Count.ToString() : "n/a");
+            }
+            else 
+            {
+                MainConsole.Instance.OutputFormat("Unrecognized OQRE subcommand {0}", subCommand);
+            }
+        }
+    }
+}
\ No newline at end of file