I have a C# application where I spawn multiple threads. I'm on .NET framework 4.7.1. Inside these threads, work is performed and this work may execute user-defined scripted functions. I am using ClearScript as the scripting engine and for purposes of this question I am using the VBScriptEngine. Here is an sample application demonstrating my problem:
static VBScriptEngine vbsengine = new VBScriptEngine();
static void Main(string[] args)
{
for (int i=0;i<4000;i++)
{
Thread t = new Thread(Program.ThreadedFunc);
t.Start(i);
}
Console.ReadKey();
}
static void ThreadedFunc(object i)
{
Console.WriteLine(i + ": " + vbsengine.Evaluate("1+1"));
}
On the Evaluate() function I get the following error:
System.InvalidOperationException: 'The calling thread cannot access this object because a different thread owns it.'
I understand ClearScript has implemented thread affinity and a spawned thread cannot access the globally defined engine. So what is my alternative? Create a new instance of ClearScript for each new thread? This seems incredibly wasteful and would create a lot of overhead - my application will need to process thousands of threads. I went ahead and tried this approach anyways - and while it does work (for a while) - end up getting an error. Here's a revised version of my sample app:
static void Main(string[] args)
{
for (int i=0;i<4000;i++)
{
Thread t = new Thread(Program.ThreadedFunc);
t.Start(i);
}
Console.ReadKey();
}
static void ThreadedFunc(object i)
{
using (VBScriptEngine vbsengine = new VBScriptEngine())
{
Console.WriteLine(i + ": " + vbsengine.Evaluate("1+1"));
}
}
On the new VBScriptEngine() call, I now start getting: System.ComponentModel.Win32Exception: 'Not enough storage is available to process this command'.
I'm not really sure what's causing that message as the application isn't taking up a lot of RAM.
I realize this sample application is starting all the threads at once but my full application ensures only 4 threads are running and I still end up getting this message after a while. I don't know why, but I can't get rid of this message either - even after restarting the app and Visual Studio. A little clarity on what's causing this message would be useful.
So my question is - if I only need, say 4 threads, running at once - is there a way I can just create 4 instances of the VBScriptEngine and reuse it for each new thread call? Or even just 1 instance of the VBScriptEngine on the main thread and each new thread just shares it?
With some help from the ClearScript team, I was able to get able to get my sample app to work using only 1 dedicated engine instance per thread. The trick was creating all the necessary engines first with its own thread, then within my loop using Dispatcher.Invoke() to call my threaded function. Here is an updated sample app using this approach:
static void Main(string[] args)
{
var vbengines = new VBScriptEngine[Environment.ProcessorCount];
var checkPoint = new ManualResetEventSlim();
for (var index = 0; index < vbengines.Length; ++index)
{
var thread = new Thread(indexArg =>
{
using (var engine = new VBScriptEngine())
{
vbengines[(int)indexArg] = engine;
checkPoint.Set();
Dispatcher.Run();
}
});
thread.Start(index);
checkPoint.Wait();
checkPoint.Reset();
}
Parallel.ForEach(Enumerable.Range(0, 4000), item => {
var engine = vbengines[item % vbengines.Length];
engine.Dispatcher.Invoke(() => {
ThreadedFunc(new myobj() { vbengine = engine, index = item });
});
});
Array.ForEach(vbengines, engine => engine.Dispatcher.InvokeShutdown());
Console.ReadKey();
}
static void ThreadedFunc(object obj)
{
Console.WriteLine(((myobj)obj).index.ToString() + ": " + ((myobj)obj).vbengine.Evaluate("1+1").ToString());
}
class myobj
{
public VBScriptEngine vbengine { get; set; }
public int index { get; set; }
}
Related
I've built a program that
takes in a list of record data from a file
parses and cleans up each record in a parsing object
outputs it to an output file
So far this has worked on a single thread, but considering the fact that records can exceed 1 million in some cases, we want to implement this in a multi threading context. Multi threading is new to me in .Net, and I've given it a shot but its not working. Below I will provide more details and code:
Main Class (simplified):
public class MainClass
{
parseObject[] parseObjects;
Thread[] threads;
List<InputLineItem> inputList = new List<InputLineItem>();
FileUtils fileUtils = new FileUtils();
public GenParseUtilsThreaded(int threadCount)
{
this.threadCount = threadCount;
Init();
}
public void Init()
{
inputList = fileUtils.GetInputList();
parseObjects = new parseObject[threadCount - 1];
threads = new Thread[threadCount - 1];
InitParseObjects();
Parse();
}
private void InitParseObjects()
{
//using a ref of fileUtils to use as my lock expression
parseObjects[0] = new ParseObject(ref fileUtils);
parseObjects[0].InitValues();
for (int i = 1; i < threadCount - 1; i++)
{
parseObjects[i] = new parseObject(ref fileUtils);
parseObjects[i].InitValues();
}
}
private void InitThreads()
{
for (int i = 0; i < threadCount - 1; i++)
{
Thread t = new Thread(new ThreadStart(parseObjects[0].CleanupAndParseInput));
threads[i] = t;
}
}
public void Parse()
{
try
{
InitThreads();
int objectIndex = 0;
foreach (InputLineItem inputLineItem in inputList)
{
parseObjects[0].inputLineItem = inputLineItem;
threads[objectIndex].Start();
objectIndex++;
if (objectIndex == threadCount)
{
objectIndex = 0;
InitThreads(); //do i need to re-init the threads after I've already used them all once?
}
}
}
catch (Exception e)
{
Console.WriteLine("(286) The following error occured: " + e);
}
}
}
}
And my Parse object class (also simplified):
public class ParseObject
{
public ParserLibrary parser { get; set; }
public FileUtils fileUtils { get; set; }
public InputLineItem inputLineItem { get; set; }
public ParseObject( ref FileUtils fileUtils)
{
this.fileUtils = fileUtils;
}
public void InitValues()
{
//relevant config of parser library object occurs here
}
public void CleanupFields()
{
parser.Clean(inputLineItem.nameValue);
inputLineItem.nameValue = GetCleanupUpValueFromParser();
}
private string GetCleanupFieldValue()
{
//code to extract cleanup up value from parses
}
public void CleanupAndParseInput()
{
CleanupFields();
ParseInput();
}
public void ParseInput()
{
try
{
parser.Parse(InputLineItem.NameValue);
}
catch (Exception e)
{
}
try
{
lock (fileUtils)
{
WriteOutputToFile(inputLineItem);
}
}
catch (Exception e)
{
Console.WriteLine("(414) Failed to write to output: " + e);
}
}
public void WriteOutputToFile(InputLineItem inputLineItem)
{
//writes updated value to output file
}
}
The error I get is when trying to run the Parse function, I get this message:
An unhandled exception of type 'System.AccessViolationException' occurred in GenParse.NET.dll
Attempted to read or write protected memory. This is often an indication that other memory is corrupt.
That being said, I feel like there's a whole lot more that I'm doing wrong here aside from what is causing that error.
I also have further questions:
Do I create multiple parse objects and iteratively feed them to each thread as I'm attempting to do, or should I use one Parse object that gets shared or cloned across each thread?
If, outside the thread, I change a value in the object that I'm passing to the thread, will that change reflect in the object passed to the thread? i.e, is the object passed by value or reference?
Is there a more efficient way for each record to be assigned to a thread and its parse object than I am currently doing with the objectIndex iterator?
THANKS!
Do I create multiple parse objects and iteratively feed them to each thread as I'm attempting to do, or should I use one Parse object that gets shared or cloned across each thread?
You initialize each thread with new ThreadStart(parseObjects[0].CleanupAndParseInput) so all threads will share the same parse object. It is a fairly safe bet that the parse objects are not threadsafe. So each thread should have a separate object. Note that this might not be sufficient, if the parse library uses any global fields it might be non-threadsafe even when using separate objects.
If, outside the thread, I change a value in the object that I'm passing to the thread, will that change reflect in the object passed to the thread? i.e, is the object passed by value or reference?
Objects (i.e. classes) are passed by reference. But any changes to an object are not guaranteed to be visible in other threads unless a memoryBarrier is issued. Most synchronization code (like lock) will issue memory barriers. Keep in mind that any non-atomic operation is unsafe if a field is written an read concurrently.
Is there a more efficient way for each record to be assigned to a thread and its parse object than I am currently doing with the objectIndex iterator?
Using manual threads in this way is very old-school. The modern, easier, and probably faster way is to use a parallel-for loop. This will try to be smart about how many threads it will use and try to adapt chunk sizes to keep the synchronization overhead low.
var items = new List<int>();
ParseObject LocalInit()
{
// Do initalization, This is run once for each thread used
return new ParseObject();
}
ParseObject ThreadMain(int value, ParallelLoopState state, ParseObject threadLocalObject)
{
// Do whatever you need to do
// This is run on multiple threads
return threadLocalObject;
}
void LocalFinally(ParseObject obj)
{
// Do Cleanup for each thread
}
Parallel.ForEach(items, LocalInit, ThreadMain, LocalFinally);
As a final note, I would advice against using multithreading unless you are familiar with the potential dangers and pitfalls it involves, at least for any project where the result is important. There are many ways to screw up and make a program that will work 99.9% of the time, and silently corrupt data the remaining 0.1% of the time.
I need to test if there's any memory leak in our application and monitor to see if memory usage increases too much while processing the requests.
I'm trying to develop some code to make multiple simultaneous calls to our api/webservice method. This api method is not asynchronous and takes some time to complete its operation.
I've made a lot of research about Tasks, Threads and Parallelism, but so far I had no luck. The problem is, even after trying all the below solutions, the result is always the same, it appears to be processing only two requests at the time.
Tried:
-> Creating tasks inside a simple for loop and starting them with and without setting them with TaskCreationOptions.LongRunning
-> Creating threads inside a simple for loop and starting them with and without high priority
-> Creating a list of actions on a simple for loop and starting them using
Parallel.Foreach(list, options, item => item.Invoke)
-> Running directly inside a Parallel.For loop (below)
-> Running TPL methods with and without Options and TaskScheduler
-> Tried with different values for MaxParallelism and maximum threads
-> Checked this post too, but it didn't help either. (Could I be missing something?)
-> Checked some other posts here in Stackoverflow, but with F# solutions that I don't know how to properly translate them to C#. (I never used F#...)
(Task Scheduler class taken from msdn)
Here's the basic structure that I have:
public class Test
{
Data _data;
String _url;
public Test(Data data, string url)
{
_data = data;
_url = url;
}
public ReturnData Execute()
{
ReturnData returnData;
using(var ws = new WebService())
{
ws.Url = _url;
ws.Timeout = 600000;
var wsReturn = ws.LongRunningMethod(data);
// Basically convert wsReturn to my method return, with some logic if/else etc
}
return returnData;
}
}
sealed class ThreadTaskScheduler : TaskScheduler, IDisposable
{
// The runtime decides how many tasks to create for the given set of iterations, loop options, and scheduler's max concurrency level.
// Tasks will be queued in this collection
private BlockingCollection<Task> _tasks = new BlockingCollection<Task>();
// Maintain an array of threads. (Feel free to bump up _n.)
private readonly int _n = 100;
private Thread[] _threads;
public TwoThreadTaskScheduler()
{
_threads = new Thread[_n];
// Create unstarted threads based on the same inline delegate
for (int i = 0; i < _n; i++)
{
_threads[i] = new Thread(() =>
{
// The following loop blocks until items become available in the blocking collection.
// Then one thread is unblocked to consume that item.
foreach (var task in _tasks.GetConsumingEnumerable())
{
TryExecuteTask(task);
}
});
// Start each thread
_threads[i].IsBackground = true;
_threads[i].Start();
}
}
// This method is invoked by the runtime to schedule a task
protected override void QueueTask(Task task)
{
_tasks.Add(task);
}
// The runtime will probe if a task can be executed in the current thread.
// By returning false, we direct all tasks to be queued up.
protected override bool TryExecuteTaskInline(Task task, bool taskWasPreviouslyQueued)
{
return false;
}
public override int MaximumConcurrencyLevel { get { return _n; } }
protected override IEnumerable<Task> GetScheduledTasks()
{
return _tasks.ToArray();
}
// Dispose is not thread-safe with other members.
// It may only be used when no more tasks will be queued
// to the scheduler. This implementation will block
// until all previously queued tasks have completed.
public void Dispose()
{
if (_threads != null)
{
_tasks.CompleteAdding();
for (int i = 0; i < _n; i++)
{
_threads[i].Join();
_threads[i] = null;
}
_threads = null;
_tasks.Dispose();
_tasks = null;
}
}
}
And the test code itself:
private void button2_Click(object sender, EventArgs e)
{
var maximum = 100;
var options = new ParallelOptions
{
MaxDegreeOfParallelism = 100,
TaskScheduler = new ThreadTaskScheduler()
};
// To prevent UI blocking
Task.Factory.StartNew(() =>
{
Parallel.For(0, maximum, options, i =>
{
var data = new Data();
// Fill data
var test = new Test(data, _url); //_url is pre-defined
var ret = test.Execute();
// Check return and display on screen
var now = DateTime.Now.ToString("HH:mm:ss");
var newText = $"{Environment.NewLine}[{now}] - {ret.ReturnId}) {ret.ReturnDescription}";
AppendTextBox(newText, ref resultTextBox);
}
}
public void AppendTextBox(string value, ref TextBox textBox)
{
if (InvokeRequired)
{
this.Invoke(new ActionRef<string, TextBox>(AppendTextBox), value, textBox);
return;
}
textBox.Text += value;
}
And the result that I get is basically this:
[10:08:56] - (0) OK
[10:08:56] - (0) OK
[10:09:23] - (0) OK
[10:09:23] - (0) OK
[10:09:49] - (0) OK
[10:09:50] - (0) OK
[10:10:15] - (0) OK
[10:10:16] - (0) OK
etc
As far as I know there's no limitation on the server side. I'm relatively new to the Parallel/Multitasking world. Is there any other way to do this? Am I missing something?
(I simplified all the code for clearness and I believe that the provided code is enough to picture the mentioned scenarios. I also didn't post the application code, but it's a simple WinForms screen just to call and show results. If any code is somehow relevant, please let me know, I can edit and post it too.)
Thanks in advance!
EDIT1: I checked on the server logs that it's receiving the requests two by two, so it's indeed something related to sending them, not receiving.
Could it be a network problem/limitation related to how the framework manages the requests/connections? Or something with the network at all (unrelated to .net)?
EDIT2: Forgot to mention, it's a SOAP webservice.
EDIT3: One of the properties that I send (inside data) needs to change for each request.
EDIT4: I noticed that there's always an interval of ~25 secs between each pair of request, if it's relevant.
I would recommend not to reinvent the wheel and just use one of the existing solutions:
Most obvious choice: if your Visual Studio license allows you can use MS Load Testing Framework, most likely you won't even have to write a single line of code: How to: Create a Web Service Test
SoapUI is a free and open source web services testing tool, it has some limited load testing capabilities
If for some reasons SoapUI is not suitable (i.e. you need to run load tests in clustered mode from several hosts or you need more enhanced reporting) you can use Apache JMeter - free and open source multiprotocol load testing tool which supports web services load testing as well.
A good solution to create load tests without write a own project is use this service https://loader.io/targets
It is free for small tests, you can POST Parameters, Header,... and you have a nice reporting.
Isnt the "two requests at a time" the result of the default maxconnection=2 limit on connectionManagement?
<configuration>
<system.net>
<connectionManagement>
<add address = "http://www.contoso.com" maxconnection = "4" />
<add address = "*" maxconnection = "2" />
</connectionManagement>
</system.net>
</configuration>
My favorite load testing library is NBomber. It has an easy and powerful API, realistic user simulations, and provides you with nice HTML reports about latency and requests per second.
I used it to test my API and wrote an article about how I did it.
I've got a case that might be useful to analyze and extract some conclusions.
I've got a class that implements ITaskWorker, and each Task can run simultaneously with other Task connected with a scheduling engine.
Suppose Task A runs a job for object A_1 with B1...BN attributes, while for each attribute a command line runs and gives results (which is blocked until an answer is recieved from the command line process).
This means that for Task B we can schedule the same A_1 with B1...BN attributes.
For the following piece of code and explanation, could you find something that might resolve in threads interrupting each other (deadlocks, race conditions, starvation)?
How can I ensure that there isn't a multi threaded issue here?
I think starvation cannot be an issue here, unless there are a lot of tasks of the same type that other types cannot get to be done (see below explanation about the code). I don't see a case for deadlock, but there might be a race condition on mainLocaker or connectionLockers data members (because of the same variable and collection that's are used across multiple methods).
There cannot be the same key in the dictionary (I've verified that: [b_i.A_Name + "_" + b_i.B_Name] creates a unique key)
I've got this code in C#. Please notice that mainLocker and connectorsLockers is being used in several methods like doTaskOfTypeX, so several 'types' of workers might lock it in different parts of code:
private static object mainLocker = new Object();
private static Dictionary<string, object> connectionLockers = new Dictionary<string,object>();
private doTaskOfTypeA()
{
// ... initialize A from task parameters
var attibutes = getListOfAttribuesByObject(A);
bool localLocalTaken = false;
foreach (B b_i in attibutes)
{
try{
lock (mainLocker)
{
if (!typeLockers.ContainsKey(b_i.A_Name + "_" + b_i.B_Name))
{
typeLockers.Add(b_i.A_Name + "_" + b_i.B_Name, new object());
}
}
localLocalTaken = false;
Monitor.Enter(connectionLockers[b_i.A_Name + "_" + b_i.B_Name, ref localLocalTaken);
if (localLocalTaken)
{
var calcObj = callCLIProcess(); // a CMD call is in here
if (calcObj != null)
{
// do things with calcObj
}
else
{
jobResult = new ScheduleTaskResult(ResultTypes.Failed);
}
}
}
catch
{
jobResult = new ScheduleTaskResult(ResultTypes.Failed);
throw;
}
finally
{
if (localLocalTaken)
{
Monitor.Exit(connectionLockers[b_i.A_Name + "_" + b_i.B_Name]);
}
}
}
}
Actually, there is no issue here.
The [// do things with calcObj] notation had a code from an external library that didn't work too well :-)
I have a user control that displays information from the database. This user control has to update these information constantly(let's say every 5 seconds). A few instances of this user control is generated programmatically during run time in a single page. In the code behind of this user control I added a code that sends a query to the database to get the needed information (which means every single instance of the user control is doing this). But this seems to slow down the processing of queries so I am making a static class that will do the querying and store the information in its variables and let the instances of my user control access those variables. Now I need this static class to do queries every 5 seconds to update its variables. I tried using a new thread to do this but the variables don't seem to be updated since I always get a NullReferenceException whenever I access them from a different class.
Here's my static class:
public static class SessionManager
{
public static volatile List<int> activeSessionsPCIDs;
public static volatile List<int> sessionsThatChangedStatus;
public static volatile List<SessionObject> allSessions;
public static void Initialize() {
Thread t = new Thread(SetProperties);
t.Start();
}
public static void SetProperties() {
SessionDataAccess sd = new SessionDataAccess();
while (true) {
allSessions = sd.GetAllSessions();
activeSessionsPCIDs = new List<int>();
sessionsThatChangedStatus = new List<int>();
foreach (SessionObject session in allSessions) {
if (session.status == 1) { //if session is active
activeSessionsPCIDs.Add(session.pcid);
}
if (session.status != session.prevStat) { //if current status doesn't match the previous status
sessionsThatChangedStatus.Add(session.pcid);
}
}
Thread.Sleep(5000);
}
}
And this is how I am trying to access the variables in my static class:
protected void Page_Load(object sender, EventArgs e)
{
SessionManager.Initialize();
loadSessions();
}
private void loadSessions()
{ // refresh the current_sessions table
List<int> pcIds = pcl.GetPCIds(); //get the ids of all computers
foreach (SessionObject s in SessionManager.allSessions)
{
SessionInfo sesInf = (SessionInfo)LoadControl("~/UserControls/SessionInfo.ascx");
sesInf.session = s;
pnlMonitoring.Controls.Add(sesInf);
}
}
Any help, please? Thanks
Multiple threads problem
You have one thread that gets created for each and every call to SessionManager.Initialize.
That happens more than once in the lifetime of the process.
IIS recycles your app at some point, after a period of time should you have absolutely no requests.
Until that happens, all your created threads continue to run.
After the first PageLoad you will have one thread which updates stuff every 5 seconds.
If you refresh the page again you'll have two threads, possibly with different offsets in time but each of which, doing the same thing at 5 second intervals.
You should atomically check to see if your background thread is started already. You need at least an extra bool static field and a object static field which you should use like a Monitor (using the lock keyword).
You should also stop relying on volatile and simply using lock to make sure that other threads "observe" updated values for your static List<..> fields.
It may be the case that the other threads don't observe a change field and thusly, for them, the field is still null - therefore you get the NullReferenceException.
About volatile
Using volatile is bad, at least in .NET. There is a 90% chance that you think you know what it is doing and it's not true and there's a 99% chance that you feel relief because you used volatile and you aren't checking for other multitasking hazards the way you should.
RX to the rescue
I strongly suggest you take a look at this wonderful thing called Reactive Extensions.
Believe me, a couple of days' research combined with the fact that you're in a perfect position to use RX will pay of, not just now but in the future as well.
You get to keep your static class, but instead of materialised values that get stored within that class you create pipes that carry information. The information flows when you want it to flow. You get to have subscribers to those pipes. The number of subscribers does not affect the overall performance of your app.
Your app will be more scalable, and more robust.
Good luck!
There are few solution for this approach:
One of them is:
It's better in Global.asax in Application_start or Session_Start (depends on your case) create Thread to call your method:
Use below code :
var t = Task.Factory.StartNew(() => {
while(true)
{
SessionManager.SetProperties();
Task.Delay(5);
}
});
Second solution is using Job Scheduler for ASP.NET (that's my ideal solution).
for more info you can check this link How to run Background Tasks in ASP.NET
and third solution is rewrite your static class as follow:
public static class SessionManager
{
public static volatile List<int> activeSessionsPCIDs;
public static volatile List<int> sessionsThatChangedStatus;
public static volatile List<SessionObject> allSessions;
static SessionManager()
{
Initialize();
}
public static void Initialize() {
var t = Task.Factory.StartNew(() => {
while(true)
{
SetProperties();
Task.Delay(5);
}
});
}
public static void SetProperties() {
SessionDataAccess sd = new SessionDataAccess();
while (true) {
allSessions = sd.GetAllSessions();
activeSessionsPCIDs = new List<int>();
sessionsThatChangedStatus = new List<int>();
foreach (SessionObject session in allSessions) {
if (session.status == 1) { //if session is active
activeSessionsPCIDs.Add(session.pcid);
}
if (session.status != session.prevStat) { //if current status doesn't match the previous status
sessionsThatChangedStatus.Add(session.pcid);
}
}
Thread.Sleep(5000);
}
}
This is a solution that is a change in approach, but I kept the solution in Web Forms, to make it more directly applicable to your use case.
SignalR is a technology that enables real-time, two way communication between server and clients (browsers), which can replace your static session data class. Below, I have implemented a simple example to demonstrate the concept.
As a sample, create a new ASP.NET Web Forms application and add the SignalR package from nuget.
Install-Package Microsoft.AspNet.SignalR
You will need to add a new Owin Startup class and add these 2 lines:
using Microsoft.AspNet.SignalR;
... and within the method
app.MapSignalR();
Add some UI elements to Default.aspx:
<div class="jumbotron">
<H3 class="MyName">Loading...</H3>
<p class="stats">
</p>
</div>
Add the following JavaScript to the Site.Master. This code references signalr, and implement client-side event handlers and initiates contact with the signalr hub from the browser. here's the code:
<script src="Scripts/jquery.signalR-2.2.0.min.js"></script>
<script src="signalr/hubs"></script>
<script >
var hub = $.connection.sessiondata;
hub.client.someOneJoined = function (name) {
var current = $(".stats").text();
current = current + '\nuser ' + name + ' joined.';
$(".stats").text(current);
};
hub.client.myNameIs = function (name) {
$(".MyName").text("Your user id: " + name);
};
$.connection.hub.start().done(function () { });
</script>
Finally, add a SignalR Hub to the solution and use this code for the SessionDataHub implementation:
[HubName("sessiondata")]
public class SessionDataHub : Hub
{
private ObservableCollection<string> sessions = new ObservableCollection<string>();
public SessionDataHub()
{
sessions.CollectionChanged += sessions_CollectionChanged;
}
private void sessions_CollectionChanged(object sender, NotifyCollectionChangedEventArgs e)
{
if (e.Action == NotifyCollectionChangedAction.Add)
{
Clients.All.someOneJoined(e.NewItems.Cast<string>().First());
}
}
public override Task OnConnected()
{
return Task.Factory.StartNew(() =>
{
var youAre = Context.ConnectionId;
Clients.Caller.myNameIs(youAre);
sessions.Add(youAre);
});
}
public override Task OnDisconnected(bool stopCalled)
{
// TODO: implement this as well.
return base.OnDisconnected(stopCalled);
}
}
For more information about SignalR, go to http://asp.net/signalr
Link to source code: https://lsscloud.blob.core.windows.net/downloads/WebApplication1.zip
I'm working with with a dictionary containing a ID as key and a queue as the value. I have one thread writing to the queues, and another thread reading from the queues, so I need to use the Concurrent-structures that were introduced in .NET 4.0. As a part of this i tried to write a test application just to fill the queues, but I came across an issue with the timers stopping after around 10 seconds. I really don't understand why as there is nothing to catch, no error message or anything to give me a hint about what might be wrong.
So can someone please explain to me why the timer stops after around 10 seconds? I've tried this on two different computers (both using Visual Studio 2012, but with .NET Framework 4.0).
class Program {
private readonly ConcurrentDictionary<int, ConcurrentQueue<TestObject>> _pipes =
new ConcurrentDictionary<int, ConcurrentQueue<TestObject>>();
static void Main() {
Program program = new Program();
program.Run();
Console.Read();
}
private void Run() {
_pipes[100] = new ConcurrentQueue<TestObject>();
_pipes[200] = new ConcurrentQueue<TestObject>();
_pipes[300] = new ConcurrentQueue<TestObject>();
Timer timer = new Timer(WriteStuff, null, 0, 100);
}
private void WriteStuff(object sender) {
for (int i = 0; i < 5; i++) {
foreach (KeyValuePair<int, ConcurrentQueue<TestObject>> pipe in _pipes) {
pipe.Value.Enqueue(
new TestObject { Name = DateTime.Now.ToString("o") + "-" + i });
}
i++;
}
Console.WriteLine(DateTime.Now + "added stuff");
}
}
internal class TestObject {
public string Name { get; set; }
public bool Sent { get; set; }
}
Most likely, the timer is going out of scope and being collected. Declare the timer at outer scope. That is:
private Timer timer;
private void Run()
{
...
timer = new Timer(WriteStuff, null, 0, 100);
}
Also, I think you'll find that BlockingCollection is easier to work with than ConcurrentQueue. BlockingCollection wraps a very nice API around concurrent collections, making it easier to do non-busy waits on the queue when removing things. In its default configuration, it uses a ConcurrentQueue as the backing store. All you have to do to use it is replace ConcurrentQueue in your code with BlockingCollection, and change from calling Enqueue to calling Add. As in:
for (int i = 0; i < 5; i++)
{
foreach (var pipe in _pipes)
{
pipe.Value.Add(
new TestObject { Name = DateTime.Now.ToString("o") + "-" + i });
}
}