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  • async_write/async_read problems while trying to implement question-answer logic

    - by Max
    Good day. I'm trying to implement a question - answer logic using boost::asio. On the Client I have: void Send_Message() { .... boost::asio::async_write(server_socket, boost::asio::buffer(&Message, sizeof(Message)), boost::bind(&Client::Handle_Write_Message, this, boost::asio::placeholders::error)); .... } void Handle_Write_Message(const boost::system::error_code& error) { .... std::cout << "Message was sent.\n"; .... boost::asio::async_read(server_socket_,boost::asio::buffer(&Message, sizeof(Message)), boost::bind(&Client::Handle_Read_Message, this, boost::asio::placeholders::error)); .... } void Handle_Read_Message(const boost::system::error_code& error) { .... std::cout << "I have a new message.\n"; .... } And on the Server i have the "same - logic" code: void Read_Message() { .... boost::asio::async_read(client_socket, boost::asio::buffer(&Message, sizeof(Message)), boost::bind(&Server::Handle_Read_Message, this, boost::asio::placeholders::error)); .... } void Handle_Read_Message(const boost::system::error_code& error) { .... std::cout << "I have a new message.\n"; .... boost::asio::async_write(client_socket_,boost::asio::buffer(&Message, sizeof(Message)), boost::bind(&Server::Handle_Write_Message, this, boost::asio::placeholders::error)); .... } void Handle_Write_Message(const boost::system::error_code& error) { .... std::cout << "Message was sent back.\n"; .... } Message it's just a structure. And the output on the Client is: Message was sent. Output on the Server is: I have a new message. And that's all. After this both programs are still working but nothing happens. I tried to implement code like: if (!error) { .... } else { // close sockets and etc. } But there are no errors in reading or writing. Both programs are just running normally, but doesn't interact with each other. This code is quite obvious but i can't understand why it's not working. Thanks in advance for any advice.

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  • Real world examples of Rx

    - by theburningmonk
    I've been playing around with the Reactive Extension for a little while now, but mostly limited to handling/composing user driven events within a WPF frontend. It's such a powerful, new way of doing async programming, and I'm curious as to what other people are doing with it, and where do you think it might be able to improve the way we're currently doing things?

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  • Handling multiple async HTTP requests in Silverlight serially

    - by Jeb
    Due to the async nature of http access via WebClient or HttpWebRequest in Silverlight 4, when I want to do multiple http get/posts serially, I find myself writing code that looks like this: doFirstGet(someParams, () => { doSecondGet(someParams, () => { doThirdGet(... } }); Or something similar. I'll end up nesting subsequent calls within callbacks usually implemented using lambdas of some sort. Even if I break things out into Actions or separate methods, it still ends up being hard to read. Does anyone have a clean solution to executing multiple http requests in SL 4 serially? I don't need things to be synchronous, I just want serial execution.

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  • Async task ASP.net HttpContext.Current.Items is empty - How do handle this?

    - by GuruC
    We are running a very large web application in asp.net MVC .NET 4.0. Recently we had an audit done and the performance team says that there were a lot of null reference exceptions. So I started investigating it from the dumps and event viewer. My understanding was as follows: We are using Asyn Tasks in our controllers. We rely on HttpContext.Current.Items hashtable to store a lot of Application level values. Task<Articles>.Factory.StartNew(() => { System.Web.HttpContext.Current = ControllerContext.HttpContext.ApplicationInstance.Context; var service = new ArticlesService(page); return service.GetArticles(); }).ContinueWith(t => SetResult(t, "articles")); So we are copying the context object onto the new thread that is spawned from Task factory. This context.Items is used again in the thread wherever necessary. Say for ex: public class SomeClass { internal static int StreamID { get { if (HttpContext.Current != null) { return (int)HttpContext.Current.Items["StreamID"]; } else { return DEFAULT_STREAM_ID; } } } This runs fine as long as number of parallel requests are optimal. My questions are as follows: 1. When the load is more and there are too many parallel requests, I notice that HttpContext.Current.Items is empty. I am not able to figure out a reason for this and this causes all the null reference exceptions. 2. How do we make sure it is not null ? Any workaround if present ? NOTE: I read through in StackOverflow and people have questions like HttpContext.Current is null - but in my case it is not null and its empty. I was reading one more article where the author says that sometimes request object is terminated and it may cause problems since dispose is already called on objects. I am doing a copy of Context object - its just a shallow copy and not a deep copy.

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  • Controller actions appear to be synchronous though on different requests?

    - by Oded
    I am under the impression that the below code should work asynchronously. However, when I am looking at firebug, I see the requests fired asynchronously, but the results coming back synchronously: Controller: [HandleError] public class HomeController : Controller { public ActionResult Status() { return Content(Session["status"].ToString()); } public ActionResult CreateSite() { Session["status"] += "Starting new site creation"; Thread.Sleep(20000); // Simulate long running task Session["status"] += "<br />New site creation complete"; return Content(string.Empty); } } Javascript/jQuery: $(document).ready(function () { $.ajax({ url: '/home/CreateSite', async: true, success: function () { mynamespace.done = true; } }); setTimeout(mynamespace.getStatus, 2000); }); var mynamespace = { counter: 0, done: false, getStatus: function () { $('#console').append('.'); if (mynamespace.counter == 4) { mynamespace.counter = 0; $.ajax({ url: '/home/Status', success: function (data) { $('#console').html(data); } }); } if (!mynamespace.done) { mynamespace.counter++; setTimeout(mynamespace.getStatus, 500); } } } Addtional information: IIS 7.0 Windows 2008 R2 Server Running in a VMWare virutual machine Can anyone explain this? Shouldn't the Status action be returning practically immediately instead of waiting for CreateSite to finish? Edit: How can I get the long running process to kick off and still get status updates?

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  • What happens to a transaction when App Pool recycles or the worker process is terminated forcefully?

    - by ARS
    The architecture of the application is straight forward. There is a web application which maintain account holder data. This data is processed and the status of account holders is updated based on number of business rules. This process is initiated using a button on the page and is a long running process (say 15 mins). A component is developed to do this data processing which internally calls stored procedures. Most of the business rules are kept in stored procedure. To handle timeouts the processing is done asynchornously(using Thread Pool or custom thread or Async Callback Delegates). The entire process run under a transaction. I would like to know your view on what happens to the transaction if the app pool is recycled or the worker process is terminated forcefully?

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  • Asynch operation in WinForm app

    - by TooFat
    I have a WinForms app. that when a button is clicked retrieves a bunch of data from database formats it and displays it to the end user. The operation can take 10 - 30 seconds. I would like to display a message to the user in a Dialog just saying "Be patient the operation is running" while the operation is running and then close when the data is ready to be presented to the end user. What is the best way to do this, start a new thread, use a Delegate or something else?

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  • What is the best way to read files in an EventMachine-based app?

    - by Theo
    In order not to block the reactor I would like to read files asynchronously, but I've found no obvious way of doing it using EventMachine. I've tried a few different approaches, but none of them feels right: Just read the file, it'll block the reactor, but what the hell, it's not that slow (unless it's a big file, and then it definitely is). Open the file for reading and read a chunk on each tick (but how much to read? too much and it'll block the reactor, too little and reading will get slower than necessary). EM.popen('cat some/file', FileReader) feels really weird, but works better than the alternatives above. In combination with the LineAndTextProtocol it reads lines pretty swiftly. EM.attach, but I haven't found any examples of how to use it, and the only thing I've found on the mailing list is that it's deprecated in favour of… EM.watch, which I've found no examples of how to use for reading files. How do you read files within a EventMachine reactor loop?

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  • How to tell iPhone NSURLConnection to abort

    - by Jahmic
    I have an app that makes moderate use of NSURLConnection. These async calls eventually finish and release properly (it looks like), but sometimes it takes some time for them to finish. So, there are times when I exit the app, (note, not just sending it the background), that some of these connections are still active. If I immediately restart the app, the app freezes on startup. (didFinishLaunchingWithOptions never seems to get called). While I'm not certain these connections are the issue, it would probably be good to terminate or cancel any remaining. Any suggestions on how to do this? Bonus points on how to debug the restart also. (I'm already saving NSLog statements to a downloadable file)

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  • Android: how to update UI dynamically?

    - by pandre
    I have an Android app and I need to change UI dynamically: ex: when user presses a button, I want to change the current activity's views and, as in some cases there are a lot of views involved, I need to display a ProgressDialog. I have been using an AsyncTask, but I think that it is not the best solution, because AsyncTask's doInBackground runs a different thread, so I can't update UI from there - I have to use runOnUiThread, which runs the code in the UI Thread, but freezes the progress dialog that is shown. I guess there should be more people with similar issues, as updating UI while displaying a ProgressDialog seems to be something done regularly by applications. So does anyone have a solution to this?

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  • Request header field x-user-session is not allowed by Access-Control-Allow-Headers

    - by Saurabh Bhandari
    I am trying to do a CORS call to a WCF service endpoint hosted on IIS7.5. I have configured custom headers in IIS. My configuration looks like below <customHeaders> <add name="Access-Control-Allow-Methods" value="GET,PUT,POST,DELETE,OPTIONS" /> <add name="Access-Control-Allow-Headers" value="x-user-session,origin, content-type, accept" /> <add name="Access-Control-Allow-Credentials" value="true" /> </customHeaders> When I do a POST request I get following error message "Request header field x-user-session is not allowed by Access-Control-Allow-Headers" If I remove my custom header from the call and run it, everything works fine. Also if I do a GET call with custom header then also API works correctly. $.ajax({ type:"POST", success: function(d) { console.log(d) }, timeout: 9000, url: "http://api.myserver.com/Services/v2/CreditCard.svc/update_cc_detail", data: JSON.stringify({"card_id": 1234,"expire_month":"11","expire_year":"2020","full_name":"Demo Account", "number":"4111111111111111","is_primary":true}), xhrFields: { withCredentials: true}, headers: { x-user-session': "B23680D0B8CB5AFED9F624271F1DFAE5052085755AEDDEFDA3834EF16115BCDDC6319BD79FDCCB1E199BB6CC4D0C6FBC9F30242A723BA9C0DFB8BCA3F31F4C7302B1A37EE0A20C42E8AFD45FAB85282FCB62C0B4EC62329BD8573FEBAEBC6E8269FFBF57C7D57E6EF880E396F266E7AD841797792619AD3F1C27A5AE" }, crossDomain: true, contentType: 'application/json' });

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  • Redirecting before POST upload has been completed

    - by vartec
    I have form with file upload. The files to be uploaded actually are pictures and videos, so they can be quite big. I have logic which based on headers and first 1KB can determine if the rest will be processed or immediately rejected. In the later case I'd like to redirect client to error page without having to wait for upload to finish. The case is, that just sending response before POST is complete doesn't seem to work. The redirect get's ignored and if I close connection, browser complains with "Connection reset by peer" error. So the question is: is it even possible to do that in pure HTTP (without JavaScript on client-side), and if so, how?

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  • Exciting new Evented I/O technologies

    - by Saif Bechan
    Lately I have been having my eye on evented I/O to tackle some of my web application problems. I have been looking at things as Python's Twisted, Ruby's Eventmachine, and Node.js. Are there any other alternatives to these three, maybe in other languages as PHP ?

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  • Adding cancel ability and exception handling to async code.

    - by Rob
    I have this sample code for async operations (copied from the interwebs) public class LongRunningTask { public LongRunningTask() { //do nowt } public int FetchInt() { Thread.Sleep(2000); return 5; } } public delegate TOutput SomeMethod<TOutput>(); public class GoodPerformance { public void BeginFetchInt() { LongRunningTask lr = new LongRunningTask(); SomeMethod<int> method = new SomeMethod<int>(lr.FetchInt); // method is state object used to transfer result //of long running operation method.BeginInvoke(EndFetchInt, method); } public void EndFetchInt(IAsyncResult result) { SomeMethod<int> method = result.AsyncState as SomeMethod<int>; Value = method.EndInvoke(result); } public int Value { get; set; } } Other async approaches I tried required the aysnc page attribute, they also seemed to cancel if other page elements where actioned on (a button clicked), this approach just seemed to work. I’d like to add a cancel ability and exception handling for the longRunningTask class, but don’t erm, really know how.

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  • How can I use multi-threading with a "for" or "foreach" loop?

    - by saafh
    I am trying to run the for loop in a separate thread so that the UI should be responsive and the progress bar is visible. The problem is that I don't know how to do that :). In this code, the process starts in a separate thread, but the next part of the code is executed at the same time. The messageBox is displayed and the results are never returned (e.g. the listbox's selected index property is never set). It doesn't work even if I use, "taskEx.delay()". TaskEx.Run(() => { for (int i = 0; i < sResults.Count(); i++) { if (sResults.ElementAt(i).DisplayIndexForSearchListBox.Trim().Contains(ayaStr)) { lstGoto.SelectedIndex = i; lstGoto_SelectionChanged(lstReadingSearchResults, null); IsIndexMatched = true; break; } } }); //TaskEx.delay(1000); if (IsIndexMatched == true) stkPanelGoto.Visibility = Visibility.Collapsed; else //the index didn't match { MessagePrompt.ShowMessage("The test'" + ayaStr + "' does not exist.", "Warning!"); } Could anyone please tell me how can I use multi-threading with a "for" or "foreach" loop?

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  • Multiple instances of the same Async task (Windows Phone)

    - by Bart Teunissen
    After googeling for ages, and reading some stuff about async task in books. I made a my first program with an async task in it. Only to find out, that i can only start one task. I want to run the task more then once. This is where i found out that that doesn't seem to work. to be a little bit clearer, here are some parts of my code: InitFunction(var); This is the Task itself public async Task InitFunction(string var) { _VarHandle = await _AdsClient.GetSymhandleByNameAsync(var); _Data = await _AdsClient.ReadAsync<T>(_VarHandle); _AdsClient.AddNotificationAsync<T>(_VarHandle, AdsTransmissionMode.OnChange, 1000, this); } This works like a charm when i execute the task only once.. But is there a possibility to run it multiple times. Something like this? InitFunction(var1); InitFunction(var2); InitFunction(var3); Because if i do this now (multiple tasks at once), the task it wants to start is still running, and it throws an exeption. if someone could help me with this, that would be awesome! ~ Bart

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  • iphone dev - loading table content asynchronously

    - by Brian
    My app has a navigation controller which push and pop a series of views. One of the tableViews loads .xml file from URL and it takes 4-5 seconds. If I click the back button on the navigation bar, it will only respond after the content of the table finish loading. Is there an easy way to load the content asynchronously so that the app will still respond to my gesture on the navigation bar? p.s. I search this on the Internet and people are talking about multithreading. I don't know a lot about threads so please be more specific. Thanks in advanced =)

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  • Android app crashes on Async Task

    - by Telmo Vaz
    why is my APP crashing when I invoke the AsyncTask? public class Login extends Activity { String mail; EditText mailIn; Button btSubmit; @Override protected void onCreate(Bundle tokenArg) { super.onCreate(tokenArg); setContentView(R.layout.login); mailIn = (EditText)findViewById(R.id.usermail); btSubmit = (Button)findViewById(R.id.submit); btSubmit.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View thisView) { new LoginProc().execute(); } }); } public class LoginProc extends AsyncTask<String, Void, Void> { @Override protected void onPreExecute() { mailIn = (EditText)findViewById(R.id.usermail); mail = mailIn.getText().toString(); super.onPreExecute(); } @Override protected Void doInBackground(String... params) { Toast.makeText(getApplicationContext(), mail, Toast.LENGTH_SHORT).show(); return null; } } } I'm trying to make the String name get it's value on the preExecute method, but it happens that the app crashes on that point. Even if I take the preExecute and do that on the doInBrackground, it still crashes. What's wrong?

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  • AngularJS directives with async content

    - by SirDavik
    I'm generating a dynamic number of Google Charts tables after receiving the content through an ajax request and I wanted to apply an accordion effect on them. I wanted to know if I could do that with directives (since if I just code render the angular tags they won't get interpreted). I don't need a code example, just a short answer to see if I should learn directives or if I should do it in a different way (I was thinking routeParams). Thanks!

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  • More Poll() ?'s

    - by ultifinitus
    Back again! I've been doing some async socket programming with select() on windows,and it's been working quite well. However it's only scalable up to 1024 clients.Poll() is the way to get around that limitation, and I know it works on both linux and unix. But it doesn't work with a windows system correct? I read about WsaPoll(), does it have the exact same functionality? What libraries would I have to link to in order to use it? Can I increase the socket number safely in windows with FD_SETSIZE? My end program will be on a linux server. However I am testing on a windows system right now. Should I just swap my test machine over to a linux box? (probably going to anyway) Otherwise what would you recommend to use with windows? (sorry for all of the questions, I am doing research on my own, I promise =D)

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  • overriding callbacks avoiding attribute pollution

    - by pygabriel
    I've a class that has some callbacks and its own interface, something like: class Service: def __init__(self): connect("service_resolved", self.service_resolved) def service_resolved(self, a,b c): ''' This function is called when it's triggered service resolved signal and has a lot of parameters''' the connect function is for example the gtkwidget.connect, but I want that this connection is something more general, so I've decided to use a "twisted like" approach: class MyService(Service): def my_on_service_resolved(self, little_param): ''' it's a decorated version of srvice_resolved ''' def service_resolved(self,a,b,c): super(MyService,self).service_resolved(a,b,c) little_param = "something that's obtained from a,b,c" self.my_on_service_resolved(little_param) So I can use MyService by overriding my_on_service_resolved. The problem is the "attributes" pollution. In the real implementation, Service has some attributes that can accidentally be overriden in MyService and those who subclass MyService. How can I avoid attribute pollution? What I've thought is a "wrapper" like approach but I don't know if it's a good solution: class WrapperService(): def __init__(self): self._service = service_resolved # how to override self._service.service_resolved callback? def my_on_service_resolved(self,param): ''' '''

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