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  • Learning Asynchronous programming

    - by xenoterracide
    Asynchronous non-blocking event driven programming seems to be all the rage. I have a basic conceptual understanding of what this all means. However what I'm not sure is when and where my code can benefit from being asynchronous, or how to make blocking IO, non-blocking. I'm sure that I can simply use a library to do this, but I'm more interested in more in depth concepts, and the various ways to implement it myself. Are there any comprehensive/definitive books, or other resources on this subject (like GoF for Design Patterns, or K&R for C, tldp for things like bash)? (Note: I'm not sure if this is actually functionally an identical question to my question on Learning event driven programming)

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  • I/O Asynchronous Completion

    - by lockedscope
    In the following, it is said that an I/O handle must be associated with the thread pool but i could not find where in the given example an handle is associated with the thread. Which function or code helps to bind the file handle in that example? Using asynchronous I/O completion events, a thread from the thread pool processes data only when the data is received, and once the data has been processed, the thread returns to the thread pool. To make an asynchronous I/O call, an operating-system I/O handle must be associated with the thread pool and a callback method must be specified. When the I/O operation completes, a thread from the thread pool invokes the callback method. http://msdn.microsoft.com/en-us/library/aa720215(VS.71).aspx

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  • asynchronous pages

    - by lockedscope
    I have just read the multi-threading and custom threading in asp.net articles. http://www.williablog.net/williablog/post/2008/12/16/Custom-Threading-in-ASPNET.aspx http://www.williablog.net/williablog/post/2008/12/16/Multi-Threading-in-ASPNET.aspx I have couple of questions. What does he mean by returning a thread to the pool? Is that thread completely removed from memory or put in to a state that it does not scheduled to CPU(is it in sleep state or whatever)? If that thread is removed from memory how could it survive after async point? How this mechanism works? Are every objects(pages class, request,response etc.) are copied to somewhere else before they are disposed? (Or, is it just waiting in a sleep state and then its waked when async call ends?) He is saying that; "Having said that, making pages asynchronous is not really about improving performance, it is about improving scalability" then he is saying; "I'm sorry to say that it will do nothing for scalability or performance." So which one is true? or for which case(s) are they true?

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  • Transitioning to asynchronous programming model

    - by Simone
    our team is mantaining and developing a .NET web service written in C#. We have stress tested the web service's farm and we have evidence that the actual architecture doesn't scale well, as the number of request are constantly increasing. We analyzed Martin Fowler's conclusion in this article, and our team feels that migrating to an asynchronous programming model such as the one described could be the right direction to point to for our service too. My question is: do you think that this "switch" needs a complete rewrite of the application? Has been someone of you been able to adopt APM without rewriting everything and has some insight to share? Thank you in advance

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  • Asynchronous operations performance

    - by LicenseQ
    One of the features of asynchronous programming in .NET is saving threads during long running operation execution. The FileStream class can be setup to allow asynchronous operations, that allows running (e.g.) a copy operation without virtually using any threads. To my surprise, I found that running asynchronous stream copy performs not only slower, but also uses more processing power than synchronous stream copy equivalent. Is there any benchmark tests were done to compare a synchronous vs asynchronous operation execution (file, network, etc.)? Does it really make sense to perform an asynchronous operation instead of spanning separate thread and perform synchronous operation in server environment if the asynchronous operation is times slower than the synchronous one?

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  • Creating Asynchronous Methods in EJB 3.1

    - by cindo
    Normal 0 false false false EN-US X-NONE X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi;} OBE of the Month: Creating Asynchronous Methods in EJB 3.1 This OBE covers creating an EJB 3.1 application that demonstrates the use of the @Asynchronous annotation in an Enterprise Java Bean (EJB) class or specific method. In this tutorial, you will create a Java EE 6 Web Application and add the following components to it - a Stateless Session Bean with two asynchronous methods. You define a Servlet to call the asynchronous methods and to keep track of the invocation and completion times to demonstrate the asynchronous nature of the method calls. The index.jsp will contain a form with a submit button, Run allowing you to execute the application. The form will submit to the Servlet which invokes the asynchronous methods defined in the session bean and the response is re-directed to response.jsp. Information about the asynchronous handling procedure is displayed to users. From this information, users will notice that the invoker thread and the called asynchronous thread are working concurrently. Check out this new OBE on the Oracle Learning Library: Creating Asynchronous Methods in EJB 3.1. This OBE is part of the new EJB 3.1 New Features Series. Related OBE’s that might interest you: Creating a No-Interface View Session Bean and Packaging in a WAR File Creating and Accessing a Session Bean in a  Web Application

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  • Some clarification needed about synchronous versus asynchronous asio operations

    - by Old newbie
    As far as I know, the main difference between synchronous and asynchronous operations. I.e. write() or read() vs async_write() and async_read() is that the former, don't return until the operation finish -or error-, and the last ones, returns inmediately. Due the fact that the asynchronous operations are controlled by an io_service.run() that does not finish until the controlled operations has finalized. It seems to me that in sequencial operations as those involved in TCP/IP connections with protocols such as POP3, in which the operaton is a sequence such as: C: <connect> S: Ok. C: User... S: Ok. C: Password S: Ok. C: Command S: answer C: Command S: answer ... C: bye S: <close> The difference between synchronous/asynchronous opperatons does not make much sense. Of course, in both operations there is allways the risk that the program flow stops indefinitely by some circunstance -there the use of timers-, but I would like know some more authorized opinions in this matter. I must admit that the question is rather ill-defined, but I like hear some advices about when use one or other, because I've problems in debugging with MS Visual Studio, asynchronous SSL operations in a POP3 client in wich I'm working now -about some of who surely I would write here soon-, and sometimes think that perhaps is a bad idea use asynchronous in this. Not to say that I'm an absolute newbie with this librarys, that additionally to the difficult with the idioma, and some obscure concepts in the STL, must suffer the brevity of the asio documentation.

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  • Create and Call an ASP.NET Asynchronous Web Service and call it from JavaScript

    - by nickyt
    Environment: ASP.NET web applicaition jQuery, ASP.NET AJAX Currently using ASP.NET Web Services The title says it all. One, how do i create an ASP.NET web service that is asynchronous? I've seen many articles, that show example with IAsyncResult and BeginMyWebServiceMethod and EndMyWebServiceMethod, some using ThreadPool etc. I would just like to know what is the simplest way to make an asynchronous web service method call (ideally without having to implement other classes, if possible). To me it should be as simple as adding an attribute to the method (but I think that is wishful thinking), e.g. public SomeWebService : WebService { [Asynchronous] public static bool SomeCheck() { // code } } I'm open to using WCF if that makes it easier (we converted to ASP.NET 3.5 around Christmas time). Once I have the asynchronous web service created, what is the best way to call it from client-side script? Via jQuery's $ajax or ASP.NET's auto generated class for a web service that is script method?

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  • Designing a fluid Javascript interface to abstract away the asynchronous nature of AJAX

    - by Anurag
    How would I design an API to hide the asynchronous nature of AJAX and HTTP requests, or basically delay it to provide a fluid interface. To show an example from Twitter's new Anywhere API: // get @ded's first 20 statuses, filter only the tweets that // mention photography, and render each into an HTML element T.User.find('ded').timeline().first(20).filter(filterer).each(function(status) { $('div#tweets').append('<p>' + status.text + '</p>'); }); function filterer(status) { return status.text.match(/photography/); } vs this (asynchronous nature of each call is clearly visible) T.User.find('ded', function(user) { user.timeline(function(statuses) { statuses.first(20).filter(filterer).each(function(status) { $('div#tweets').append('<p>' + status.text + '</p>'); }); }); }); It finds the user, gets their tweet timeline, filters only the first 20 tweets, applies a custom filter, and ultimately uses the callback function to process each tweet. I am guessing that a well designed API like this should work like a query builder (think ORMs) where each function call builds the query (HTTP URL in this case), until it hits a looping function such as each/map/etc., the HTTP call is made and the passed in function becomes the callback. An easy development route would be to make each AJAX call synchronous, but that's probably not the best solution. I am interested in figuring out a way to make it asynchronous, and still hide the asynchronous nature of AJAX.

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  • Designing a fluent Javascript interface to abstract away the asynchronous nature of AJAX

    - by Anurag
    How would I design an API to hide the asynchronous nature of AJAX and HTTP requests, or basically delay it to provide a fluid interface. To show an example from Twitter's new Anywhere API: // get @ded's first 20 statuses, filter only the tweets that // mention photography, and render each into an HTML element T.User.find('ded').timeline().first(20).filter(filterer).each(function(status) { $('div#tweets').append('<p>' + status.text + '</p>'); }); function filterer(status) { return status.text.match(/photography/); } vs this (asynchronous nature of each call is clearly visible) T.User.find('ded', function(user) { user.timeline(function(statuses) { statuses.first(20).filter(filterer).each(function(status) { $('div#tweets').append('<p>' + status.text + '</p>'); }); }); }); It finds the user, gets their tweet timeline, filters only the first 20 tweets, applies a custom filter, and ultimately uses the callback function to process each tweet. I am guessing that a well designed API like this should work like a query builder (think ORMs) where each function call builds the query (HTTP URL in this case), until it hits a looping function such as each/map/etc., the HTTP call is made and the passed in function becomes the callback. An easy development route would be to make each AJAX call synchronous, but that's probably not the best solution. I am interested in figuring out a way to make it asynchronous, and still hide the asynchronous nature of AJAX.

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  • twisted deferred/callbacks and asynchronous execution

    - by NetSkay
    hey guys, quick question about twisted and python... im trying to figure out how can i make my code more asynchronous using twisted and ive come to sort of a dead end, if a function of mine returns a deferred object, then i add a list of callbacks, the first callback will be called after the deferred function provides some result through deferred_obj.callback, then, in the chain of callbacks, the first callback will do something with the data and call the second callback and etc. however chained callbacks will not be considered asynchronous because they're chained and the event loop will keep firing each one of them concurrently until there is no more, right? however, if i have a deferred object, and i attach as its callback the deferred_obj.callback as in d.addCallback(deferred_obj.callback) then this will be considered asynchronous, because the deferred_obj is waiting for the data, and then the method that will pass the data is waiting on data as well, however once i d.callback 'd' object processes the data then it call deferred_obj.callback however since this object is deferred, unlike the case of chained callbacks, it will execute asynchronously... correct? meaning chained callbacks are NOT asynchronous while chained deferreds are, correct? thank you PS: assuming all of my code is non-blocking

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  • C# getting the results from an asynchronous call

    - by Jim Beam
    I have an API that I'm working with and it has limited documentation. I have been told that some of the methods that it executes are called asynchronously. How can I get the result of these asynchronous calls. Note that I am not doing anything special to call them, the API handles the asynchronous part. But I can't seem to get a "reply" back from these calls - I'm assuming that's because they are in another thread.

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  • WinForms Control.BeginInvoke asynchronous callback

    - by Darran
    I have a number of Janus grid controls that need to be populated on an application startup. I'd like to load these grids on different threads to speed startup time and the time it takes to refresh these grids. Each grid is on a seperate tab. Ideally I'd like to use Control.BeginInvoke on each grid and on the grid load completing the tabs will become enabled. I know with Delegates you can do a Asynchronous callback when using BeginInvoke, so I could enable the tabs in the asynchronous callback, however when using Control.BeginInvoke this is not possible. Is there a way to do asynchronous callbacks using Control.BeginInvoke or possibly a better solution? So far I have: public delegate void BindDelegate(IMyGrid grid); private IAsyncResult InvokeBind(IMyGrid grid) { return ((Control)grid).BeginInvoke( new BindDelegate(DoBind), new object[] { grid } ); } private void DoBind(IMyGrid grid) { grid.Bind(); // Expensive operation } private void RefreshComplete() { IAsyncResult grid1Asynch = InvokeBind(grid1); IAsyncResult grid2Asynch = InvokeBind(grid2); IAsyncResult grid3Asynch = InvokeBind(grid2); IAsyncResult grid4Asynch = InvokeBind(grid3); IAsyncResult grid5Asynch = InvokeBind(grid4); IAsyncResult grid6Asynch = InvokeBind(grid5); } Now I could spin off a separate thread and keep checking to see if the IAsynchResults have completed and depending on which one completes I could re-enable the Tab control that the grid is contained in. Is there a better way of doing this?

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  • Performance implications of Synchronous Sockets vs Asynchronous Sockets

    - by Akash Kava
    We are trying to build an SMTP Server to receive mail notifications from various clients over internet. As each of the communication will be longer and it needs to log everything, doing this Asynchronous way is little challenging as well as by using Socket's Asynchronous methods we are not sure of how flow of control and error handling happens. Previously we wrote lot of server/client apps but we always used Synchronous sockets, reason being they are longer sessions and each session also has lot of local data to manage and parsing messages etc. Does anyone have any experience over real performance differences between these two methods? Async calls use ThreadPool which we have experienced many times to just die for no reason. And we fail to restart threadpool etc. In one way Request-Response protocol of HTTP, Async Sockets makes sense, but SMTP/IMAP etc protocols are longer and they have interleaved messages plus state machine of server. So Async methods are really complicated to program. However if anyone can share the performance of Sockets, it will be helpful.

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  • Asynchronous sockets in C#

    - by IVlad
    I'm confused about the correct way of using asynchronous socket methods in C#. I will refer to these two articles to explain things and ask my questions: MSDN article on asynchronous client sockets and devarticles.com article on socket programming. My question is about the BeginReceive() method. The MSDN article uses these two functions to handle receiving data: private static void Receive(Socket client) { try { // Create the state object. StateObject state = new StateObject(); state.workSocket = client; // Begin receiving the data from the remote device. client.BeginReceive( state.buffer, 0, StateObject.BufferSize, 0, new AsyncCallback(ReceiveCallback), state); } catch (Exception e) { Console.WriteLine(e.ToString()); } } private static void ReceiveCallback( IAsyncResult ar ) { try { // Retrieve the state object and the client socket // from the asynchronous state object. StateObject state = (StateObject) ar.AsyncState; Socket client = state.workSocket; // Read data from the remote device. int bytesRead = client.EndReceive(ar); if (bytesRead > 0) { // There might be more data, so store the data received so far. state.sb.Append(Encoding.ASCII.GetString(state.buffer,0,bytesRead)); // Get the rest of the data. client.BeginReceive(state.buffer,0,StateObject.BufferSize,0, new AsyncCallback(ReceiveCallback), state); } else { // All the data has arrived; put it in response. if (state.sb.Length > 1) { response = state.sb.ToString(); } // Signal that all bytes have been received. receiveDone.Set(); } } catch (Exception e) { Console.WriteLine(e.ToString()); } } While the devarticles.com tutorial passes null for the last parameter of the BeginReceive method, and goes on to explain that the last parameter is useful when we're dealing with multiple sockets. Now my questions are: What is the point of passing a state to the BeginReceive method if we're only working with a single socket? Is it to avoid using a class field? It seems like there's little point in doing it, but maybe I'm missing something. How can the state parameter help when dealing with multiple sockets? If I'm calling client.BeginReceive(...), won't all the data be read from the client socket? The devarticles.com tutorial makes it sound like in this call: m_asynResult = m_socClient.BeginReceive (theSocPkt.dataBuffer,0,theSocPkt.dataBuffer.Length, SocketFlags.None,pfnCallBack,theSocPkt); Data will be read from the theSocPkt.thisSocket socket, instead of from the m_socClient socket. In their example the two are one and the same, but what happens if that is not the case? I just don't really see where that last argument is useful or at least how it helps with multiple sockets. If I have multiple sockets, I still need to call BeginReceive on each of them, right?

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  • How to write Asynchronous LINQ query?

    - by Morgan Cheng
    After I read a bunch of LINQ related stuff, I suddenly realized that no articles introduce how to write asynchronous LINQ query. Suppose we use LINQ to SQL, below statement is clear. However, if the SQL database responds slowly, then the thread using this block of code would be hindered. var result = from item in Products where item.Price > 3 select item.Name; foreach (var name in result) { Console.WriteLine(name); } Seems that current LINQ query spec doesn't provide support to this. Is there any way to do asynchronous programming LINQ? It works like there is a callback notification when results are ready to use without any blocking delay on I/O.

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  • What sense does asynchronous IO make if the thread is blocked anyway (see example)

    - by codymanix
    Hello, I found an example for async ftp upload on msdn which does the following (snippet): // Asynchronously get the stream for the file contents. request.BeginGetRequestStream( new AsyncCallback (EndGetStreamCallback), state ); // Block the current thread until all operations are complete. waitObject.WaitOne(); The thing what I do not understand here is, which sense does asynchronous IO make if the thread is blocked anyway with an explicit waithandle. I always thought the advantage of asynchronous IO was that the user/programm does not have to wait.

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  • Asynchronous email processing in Java web application

    - by Denise
    Hi everyone, I would like to implement asynchronous email sending in my web application when users register for a new account. This is so that if there is a problem or delay in sending the email message (e.g. the mail server is down or the network connection to the mail server is slow) the user won't be kept waiting for the sending to complete. My web app is built using Spring and Hibernate's implementation of JPA. What would be the best and most reliable way for me to implement asynchronous email processing in this web application? I am thinking about persisting the email information in a database table which is then regularly polled by a Quartz (http://www.opensymphony.com/quartz/) scheduled job for updates and when it finds new unsent emails, it attempts to send them. Is this a reasonable way of implementing what I want? Thanks.

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  • Converting Asynchronous Programming Model (Begin/End methods) into event-based asynchronous model?

    - by David
    Let's say I have code that uses the Asynchronous Programming Model, i.e. it provides the following methods as a group which can be used synchronously or asynchronously: public MethodResult Operation(<method params>); public IAsyncResult BeginOperation(<method params>, AsyncCallback callback, object state); public MethodResult EndOperation(IAsyncResult ar); What I want to do is wrap this code with an additional layer that will transform it into the event-driven asynchronous model, like so: public void OperationAsync(<method params>); public event OperationCompletedEventHandler OperationCompleted; public delegate void OperationCompletedEventHandler(object sender, OperationCompletedEventArgs e); Does anyone have any guidance (or links to such guidance) on how to accomplish this?

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  • Asynchronous Processing in JBoss 6 ("Comet")

    - by chris_l
    edit: Retagged as tomcat, since this is really a question about the Tomcat embedded inside JBoss 6, rather than JBoss itself I have an extremely simple servlet, which works on Glassfish v3. It uses Servlet 3.0 Asynchronous Processing. Here's a simplified version (which doesn't do much): @WebServlet(asyncSupported=true) public class SimpleServlet extends HttpServlet { @Override protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { final AsyncContext ac = request.startAsync(); ac.setTimeout(3000); } } On JBoss 6.0.0 (Milestone 2), I get the following Exception: java.lang.IllegalStateException: The servlet or filters that are being used by this request do not support async operation at org.apache.catalina.connector.Request.startAsync(Request.java:3096) at org.apache.catalina.connector.Request.startAsync(Request.java:3090) at org.apache.catalina.connector.RequestFacade.startAsync(RequestFacade.java:990) at playcomet.SimpleServlet.doGet(SimpleServlet.java:18) at javax.servlet.http.HttpServlet.service(HttpServlet.java:734) ... Do I have to do anything special to enable Asynchronous Processing in JBoss 6? Or do I need an additional deployment descriptor? ...

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  • Implementing an interface using an asynchronous WCF service?

    - by John K.
    Hello, I am trying to figure out if it is possible to implement a .NET interface, where the interface method has to return something and you are implementing that particular interface method with an asynchronous WCF service? Hopefully you should already see the issue I am encountering. Here is the interface: public interface IDataService { IDataServiceResponse SendDataRequest(); } IDataServiceResponse is supposed to represent a simple container that holds the result of my asynchronous WCF callback. Here is the code snippet where I am implementing the interface method, SendDataRequest() public IDataServiceResponse SendDataRequest() { InitializeDataServiceParameters(); // Call the web service asynchronously, here.... _client.BeginQueryJobs(_parameters, DataServiceQueryCallBack, _client); // How do I return _dataServiceResponse, if I am calling the WCF service // asynchronously?? return _dataServiceResponse; } And the callback method signature: void DataServiceQueryCallBack(IAsyncResult result) { // ... implementation code } Thanks in advance, John

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  • Django Asynchronous Processing

    - by freyrs
    Hello all, I have a bunch of Django requests which executes some mathematical computations ( written in C and executed via a Cython module ) which may take an indeterminate amount ( on the order of 1 second ) of time to execute. Also the requests don't need to access the database. Right now everything is synchronous ( using Gunicorn with sync worker types ) but I'd like to make this asynchronous and nonblocking. I am very new to asynchronous Django, and so my question is what is the best stack for doing this. Is this sort of process something a task queue is well suited for? Would anyone recommend Tornado + Celery + RabbitMQ, or perhaps something else? Thanks in advance!

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