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• Looking for open-source solutions for a knowledge sharing website

  - by Bundarr

  There is a need in my workplace to setup a knowledge sharing site, a place where users can discuss projects they are working share documentation ask questions I am looking for a open-source system that answers these needs, and that can be setup in a week, and requires only PHP and MySQL. I am a Wordpress fan and developer and could easily implement such a system in Wordpress, however this system needs to be very simple to use for the technically challenged. Without customization, Wordpress users would still need to login to the "back-end" to post. I like the Stackexchange (OSQA) format, but these do not allow for file uploading out of the box. I do not have experience with Buddy Press, would this be an alternative?

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• Apache Reverse Proxy not working inside a VirtualHost running a Mono Web Application

  - by Arwen

  I have a mono web application running with this virtual host below. It is running on Apache 2.2.20 / Ubuntu 11.10. I tried to add a reverse proxy inside this virtualhost so I can make asynchronous or AJAX type calls back to this same domain. My asynchronous requests would have problems in many browsers calling services that are on another domain (cross domain requests problem). I am wanting to do reverse proxy calls to this other service using http://www.whatever.com/monkey/. So, I added the directive and top directive to try to make this work. It is weird though...nothing I do seems to have any effect. I can put the exact same markup in my default website virtualhost file and it works great. What is the deal? Are some of these Mono directives causing problems? <VirtualHost *:80> ServerName www.whatever.com ServerAlias whatever.com *.whatever.com ServerAdmin [email protected] DocumentRoot /home/myuser/web/whatever ProxyRequests off <Proxy *> Order allow,deny Allow from all </Proxy> <Location /monkey/> ProxyPass http://www.google.com/ ProxyPassReverse http://www.google.com/ </Location> MonoServerPath www.whatever.com "/usr/bin/mod-mono-server2" MonoSetEnv www.whatever.com MONO_IOMAP=all MonoApplications www.whatever.com "/:/home/myuser/web/whatever" <Location "/"> Allow from all Order allow,deny MonoSetServerAlias www.whatever.com SetHandler mono SetOutputFilter DEFLATE SetEnvIfNoCase Request_URI "\.(?:gif|jpe?g|png)$" no-gzip dont-vary </Location> <IfModule mod_deflate.c> AddOutputFilterByType DEFLATE text/html text/plain text/xml text/javascript </IfModule> </VirtualHost>

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• How can I persuade our team to use mac as our development platform?

  - by Allen Bargi

  I'm joining a start up and there's a debate on which platform we should choose for our development; Mac, Linux or Windows? We're gonna use mainly open source tools and languages like, ruby, rails, PHP and mysql and photoshop (or something equivalent on Linux) for design. I suggested mac but they challenged me to be more persuasive. what's your idea? Help me with your persuasive arguments please.

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• Timeout Considerations for Solicit Response

  - by Michael Stephenson

  Background One of the clients I work with had been experiencing some issues for a while surrounding web service timeouts.  It's been a little challenging to work through the problems due to limitations in the diagnostic information available from one of the applications, but I learned some interesting things while troubleshooting the problem which don't seem to have been discussed much in the community so I thought I'd share my findings. In the scenario we have BizTalk trying to make calls to a .net web service which was exposed as a WSE 2 endpoint.  In the process BizTalk will try to make a large number of concurrent web service calls to the application, and the backend application has more than enough infrastructure and capability to handle the load. We have configured the <ConnectionManagement> section of the BizTalk configuration file to support up to 100 concurrent connections from each of our 2 BizTalk send servers to the web servers of the application. The problem we were facing was that the BizTalk side was reporting a significant number of timeouts when calling the web service.   One of the biggest issues was the challenge of being able to correlate a message from BizTalk to the IIS log in the .net application and the custom logs in the application especially when there was a fairly large number of servers hosting the web services.  However the key moment came when we were able to identify a specific call which had taken 40 seconds to execute on the server (yes a long time I know but that's a different story!).  Anyway we were able to identify that this had timed out on the BizTalk side.  Based on the normal 2 minute timeout we knew something unexpected was going on. From here I decided to do some experimentation and I wanted to start outside of BizTalk because my hunch was this was not a BizTalk behaviour but something which was being highlighted by BizTalk because of our large load.     Server-side - Sample Web Service To begin with I created a sample web service.  Nothing special just a vanilla asmx web service hosted in IIS6 on Windows 2003 Standard Edition.  The web service is just a hello world style web service as shown in the below picture.  The only key feature is that the server side web method has a 30 second sleep in it and will trace out some information before and after the thread is set to sleep.      In the configuration for this web service there again is nothing special it's pretty much the most plain simple web service you could build. Client-Side To begin looking at what was happening with our example I created a number of different ways to consume the web service. SoapHttpClientProtocol Example I created a small application which would use a normal proxy generated to call the web service.  It would iterate around a loop and make calls using the begin/end methods so I can do this asynchronously.  I would do a loop of 20 calls with the ConnectionManager configuration section supporting only 5 concurrent connections to the server.     <connectionManagement> <remove address="*"/> <add address = "*" maxconnection = "12" /> <add address = "http://<ServerName>" maxconnection = "5" />                         </connectionManagement> </system.net>     The below picture shows an example of the service calling code, key points are: I have configured the timeout of 40 seconds for the proxy I am using the asynchronous methods on the proxy to call the web service         The Test I would run the client and execute 21 calls to the web service.   The Results  Below is the client side trace showing what's happening on the client. In the below diagram is the web service side trace showing what's happening on the server Some observations on the results are: All of the calls were successful from the clients perspective You could see the next call starting on the server as soon as the previous one had completed Calls took significantly longer than 40 seconds from the start of our call to the return. In fact call 20 took 2 minutes and 30 seconds from the perspective of my code to execute even though I had set the timeout to 40 seconds     WSE 2 Sample In the second example I used the exact same code to call the web service again with a single exception that I modified the web service proxy to derive from WebServiceClient protocol which is part of WSE 2 (using SP3).  The below picture shows the basic code and the key points are: I have configured the timeout of 40 seconds for the proxy I am using the asynchronous methods on the proxy to call the web service        The Test This test would execute 21 calls from the client to the web service.   The Results  The below trace is from the client side: The below trace is from the server side:   Some observations on the trace results for this scenario are: With call 4 if you look at the server side trace it did not start executing on the server for a number of seconds after the other 4 initial calls which were accepted by the server. I re-ran the test and this happened a couple of times and not on most others so at this point I'm just putting this down to something unexpected happening on the development machine and we will leave this observation out of scope of this article. You can see that the client side trace statement executed almost immediately in all cases All calls after the initial few calls would timeout On the client side the calls that did timeout; timed out in a longer duration than the 40 seconds we set as the timeout You can see that as calls were completing on the server the next calls were starting to come through The calls that timed out on the client did actually connect to the server and their server side execution completed successfully     Elaboration on the findings Based on the above observations I have drawn the below sequence diagram to illustrate conceptually what is happening.  Everything except the final web service object is on the client side of the call. In the diagram below I've put two notes on the Web Service Proxy to show the two different places where the different base classes seem to start their timeout counters. From the earlier samples we can work out that the timeout counter for the WSE web service proxy starts before the one for the SoapHttpClientProtocol proxy and the WSE one includes the time to get a connection from the pool; whereas the Soap proxy timeout just covers the method execution. One interesting observation is if we rerun the above sample and increase the number of calls from 21 to 100,000 then for the WSE sample we will see a similar pattern where everything after the first few calls will timeout on the client as soon as it makes a connection to the server whereas the soap proxy will happily plug away and process all of the calls without a single timeout. I have actually set the sample running overnight and this did happen. At this point you are probably thinking the same thoughts I was at the time about the differences in behaviour and which is right and why are they different? I'm not sure there is a definitive answer to this in the documentation, or at least not that I could find! I think you just have to consider that they are different and they could have different effects depending on your messaging solution. In lots of situations this is just not an issue as your concurrent requests doesn't get to the situation where you end up throttling the web service calls on the client side, however this is definitely more common with an integration broker such as BizTalk where you often have high throughput requirements.  Some of the considerations you should make Based on this behaviour you should be aware of the following: In a .net application if you are making lots of concurrent web service calls from an application in an asynchronous manner your user may thing they are experiencing poor performance but you think your web service is working well. The problem could be that the client will have a default of 2 connections to remote servers so you should bear this in mind When you are developing a BizTalk solution or a .net solution with the WSE 2 stack you may experience timeouts under load and throttling the number of connections using the max connections element in the configuration file will not help you For an application using WSE2 or SoapHttpClientProtocol an expired timeout will not throw an error until after a connection to the server has been made so you should consider this in your transaction and durability patterns     Our Work Around In the short term for our specific scenario we know that we can handle this by just increasing our timeout value.  There is only a specific small window when we get lots of concurrent traffic that causes this scenario so we should be able to increase the timeout to take into consideration the additional client side wait, and on the odd occasion where we do get a timeout the BizTalk send port retry will handle this. What was causing our original problem was that for that short window we were getting a lot of retries which significantly increased the load on our send servers and highlighted the issue.  Longer Term Solution As a longer term solution this really gives us more ammunition to argue a migration to WCF. The application we are calling has some factors which limit the protocols we can use but with WCF we would have more control on the various timeout options because in WCF you can configure specific parts of the timeout. Summary I've had this blog post on my to do list for ages but hopefully it will be useful to some people to just understand this behaviour and to possibly help you with some performance issues you may have. I do not believe there is too much in the way of documentation particularly around WSE2 and ASMX in this area so again another bit of ammunition for migrating to WCF. I'll try to do a follow up post with the sample for WCF to show how this changes things.

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• Sending emails in web applications

  - by Denise

  Hi everyone, I'm looking for some opinions here, I'm building a web application which has the fairly standard functionality of: Register for an account by filling out a form and submitting it. Receive an email with a confirmation code link Click the link to confirm the new account and log in When you send emails from your web application, it's often (usually) the case that there will be some change to the persistence layer. For example: A new user registers for an account on your site - the new user is created in the database and an email is sent to them with a confirmation link A user assigns a bug or issue to someone else - the issue is updated and email notifications are sent. How you send these emails can be critical to the success of your application. How you send them depends on how important it is that the intended recipient receives the email. We'll look at the following four strategies in relation to the case where the mail server is down, using example 1. TRANSACTIONAL & SYNCHRONOUS The sending of the email fails and the user is shown an error message saying that their account could not be created. The application will appear to be slow and unresponsive as the application waits for the connection timeout. The account is not created in the database because the transaction is rolled back. TRANSACTIONAL & ASYNCHRONOUS The transactional definition here refers to sending the email to a JMS queue or saving it in a database table for another background process to pick up and send. The user account is created in the database, the email is sent to a JMS queue for processing later. The transaction is successful and committed. The user is shown a message saying that their account was created and to check their email for a confirmation link. It's possible in this case that the email is never sent due to some other error, however the user is told that the email has been sent to them. There may be some delay in getting the email sent to the user if application support has to be called in to diagnose the email problem. NON-TRANSACTIONAL & SYNCHRONOUS The user is created in the database, but the application gets a timeout error when it tries to send the email with the confirmation link. The user is shown an error message saying that there was an error. The application is slow and unresponsive as it waits for the connection timeout When the mail server comes back to life and the user tries to register again, they are told their account already exists but has not been confirmed and are given the option of having the email re-sent to them. NON-TRANSACTIONAL & ASYNCHRONOUS The only difference between this and transactional & asynchronous is that if there is an error sending the email to the JMS queue or saving it in the database, the user account is still created but the email is never sent until the user attempts to register again. What I'd like to know is what have other people done here? Can you recommend any other solutions other than the 4 I've mentioned above? What's a reasonable way of approaching this problem? I don't want to over-engineer a system that's dealing with the (hopefully) rare situation where my mail server goes down! The simplest thing to do is to code it synchronously, but are there any other pitfalls to this approach? I guess I'm wondering if there's a best practice, I couldn't find much out there by googling.

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• Windows Azure Recipe: Mobile Computing

  - by Clint Edmonson

  A while back, mashups were all the rage. The idea was to compose solutions that provided aggregation and integration across applications and services to make information more available, useful, and personal. Mashups ushered in the era of Web 2.0 in all it’s socially connected goodness. They taught us that to be successful, we needed to add web service APIs to our web applications. Web and client based mashups met with great success and have evolved even further with the introduction of the internet connected smartphone. Nothing is more available, useful, or personal than our smartphones. The current generation of cloud connected mobile computing mashups allow our mobilized workforces to receive, process, and react to information from disparate sources faster than ever before. Drivers Integration Reach Time to market Solution Here’s a sketch of a prototypical mobile computing solution using Windows Azure: Ingredients Web Role – with the phone running a dedicated client application, the web role is responsible for serving up backend web services that implement the solution’s core connected functionality. Database – used to store core operational and workflow data for the solution’s web services. Access Control – this service is used to authenticate and manage users identity, roles, and groups, possibly in conjunction with 3rd identity providers such as Windows LiveID, Google, Yahoo!, and Facebook. Worker Role – this role is used to handle the orchestration of long-running, complex, asynchronous operations. While much of the integration and interaction with other services can be handled directly by the mobile client application, it’s possible that the backend may need to integrate with 3rd party services as well. Offloading this work to a worker role better distributes computing resources and keeps the web roles focused on direct client interaction. Queues – these provide reliable, persistent messaging between applications and processes. They are an absolute necessity once asynchronous processing is involved. Queues facilitate the flow of distributed events and allow a solution to send push notifications back to mobile devices at appropriate times. Training & Resources These links point to online Windows Azure training labs and resources where you can learn more about the individual ingredients described above. (Note: The entire Windows Azure Training Kit can also be downloaded for offline use.) Windows Azure (16 labs) Windows Azure is an internet-scale cloud computing and services platform hosted in Microsoft data centers, which provides an operating system and a set of developer services which can be used individually or together. It gives developers the choice to build web applications; applications running on connected devices, PCs, or servers; or hybrid solutions offering the best of both worlds. New or enhanced applications can be built using existing skills with the Visual Studio development environment and the .NET Framework. With its standards-based and interoperable approach, the services platform supports multiple internet protocols, including HTTP, REST, SOAP, and plain XML SQL Azure (7 labs) Microsoft SQL Azure delivers on the Microsoft Data Platform vision of extending the SQL Server capabilities to the cloud as web-based services, enabling you to store structured, semi-structured, and unstructured data. Windows Azure Services (9 labs) As applications collaborate across organizational boundaries, ensuring secure transactions across disparate security domains is crucial but difficult to implement. Windows Azure Services provides hosted authentication and access control using powerful, secure, standards-based infrastructure. Windows Azure Toolkit for Windows Phone The Windows Azure Toolkit for Windows Phone is designed to make it easier for you to build mobile applications that leverage cloud services running in Windows Azure. The toolkit includes Visual Studio project templates for Windows Phone and Windows Azure, class libraries optimized for use on the phone, sample applications, and documentation Windows Azure Toolkit for iOS The Windows Azure Toolkit for iOS is a toolkit for developers to make it easy to access Windows Azure storage services from native iOS applications. The toolkit can be used for both iPhone and iPad applications, developed using Objective-C and XCode. Windows Azure Toolkit for Android The Windows Azure Toolkit for Android is a toolkit for developers to make it easy to work with Windows Azure from native Android applications. The toolkit can be used for native Android applications developed using Eclipse and the Android SDK. See my Windows Azure Resource Guide for more guidance on how to get started, including links web portals, training kits, samples, and blogs related to Windows Azure.

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• How set EnqueueCallBack to my generic callback

  - by CrazyJoe

  using System; using System.Windows; using System.Windows.Controls; using System.Windows.Documents; using System.Windows.Ink; using System.Windows.Input; using System.Windows.Media; using System.Windows.Media.Animation; using System.Windows.Shapes; using Microsistec.Domain; using Microsistec.Client; using Microsoft.VisualStudio.TestTools.UnitTesting; using System.Collections.Generic; using Microsistec.Tools; using System.Json; using Microsistec.SystemConfig; using System.Threading; using Microsoft.Silverlight.Testing; namespace Test { [TestClass] public class SampleTest : SilverlightTest { [TestMethod, Asynchronous] public void login() { List<PostData> data = new List<PostData>(); data.Add(new PostData("email", "xxx")); data.Add(new PostData("password", MD5.GetHashString("xxx"))); WebClient.sendData(Config.DataServerURL + "/user/login", data, LoginCallBack); EnqueueCallback(?????????); EnqueueTestComplete(); } [Asynchronous] public void LoginCallBack(object sender, System.Net.UploadStringCompletedEventArgs e) { string json = Microsistec.Client.WebClient.ProcessResult(e); var result = JsonArray.Parse(json); Assert.Equals("1", result["value"].ToString()); TestComplete(); } } Im tring to set ???????? value but my callback is generic, it is setup on my WebClient .SendData, how i implement my EnqueueCallback to a my already functio LoginCallBack???

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• Async.Parallel or Array.Parallel.Map ?

  - by gurteen2

  Hello- I'm trying to implement a pattern I read from Don Syme's blog (http://blogs.msdn.com/dsyme/archive/2010/01/09/async-and-parallel-design-patterns-in-f-parallelizing-cpu-and-i-o-computations.aspx) which suggests that there are opportunities for massive performance improvements from leveraging asynchronous I/O. I am currently trying to take a piece of code that "works" one way, using Array.Parallel.Map, and see if I can somehow achieve the same result using Async.Parallel, but I really don't understand Async.Parallel, and cannot get anything to work. I have a piece of code (simplified below to illustrate the point) that successfully retrieves an array of data for one cusip. (A price series, for example) let getStockData cusip = let D = DataProvider() let arr = D.GetPriceSeries(cusip) return arr let data = Array.Parallel.map (fun x -> getStockData x) stockCusips So this approach contructs an array of arrays, by making a connection over the internet to my data vendor for each stock (which could be as many as 3000) and returns me an array of arrays (1 per stock, with a price series for each one). I admittedly don't understand what goes on underneath Array.Parallel.map, but am wondering if this is a scenario where there are resources wasted under the hood, and it actually could be faster using asynchronous I/O? So to test this out, I have attempted to make this function using asyncs, and I think that the function below follows the pattern in Don Syme's article using the URLs, but it won't compile with "let!". let getStockDataAsync cusip = async { let D = DataProvider() let! arr = D.GetData(cusip) return arr } The error I get is: This expression was expected to have type Async<'a but here has type obj It compiles fine with "let" instead of "let!", but I had thought the whole point was that you need the exclamation point in order for the command to run without blocking a thread. So the first question really is, what's wrong with my syntax above, in getStockDataAsync, and then at a higher level, can anyone offer some additional insight about asychronous I/O and whether the scenario I have presented would benefit from it, making it potentially much, much faster than Array.Parallel.map? Thanks so much.

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• Using ThreadPool.QueueUserWorkItem in ASP.NET in a high traffic scenario

  - by Michael Hart

  I've always been under the impression that using the ThreadPool for (let's say non-critical) short-lived background tasks was considered best practice, even in ASP.NET, but then I came across this article that seems to suggest otherwise - the argument being that you should leave the ThreadPool to deal with ASP.NET related requests. So here's how I've been doing small asynchronous tasks so far: ThreadPool.QueueUserWorkItem(s => PostLog(logEvent)) And the article is suggesting instead to create a thread explicitly, similar to: new Thread(() => PostLog(logEvent)){ IsBackground = true }.Start() The first method has the advantage of being managed and bounded, but there's the potential (if the article is correct) that the background tasks are then vying for threads with ASP.NET request-handlers. The second method frees up the ThreadPool, but at the cost of being unbounded and thus potentially using up too many resources. So my question is, is the advice in the article correct? If your site was getting so much traffic that your ThreadPool was getting full, then is it better to go out-of-band, or would a full ThreadPool imply that you're getting to the limit of your resources anyway, in which case you shouldn't be trying to start your own threads? Clarification: I'm just asking in the scope of small non-critical asynchronous tasks (eg, remote logging), not expensive work items that would require a separate process (in these cases I agree you'll need a more robust solution).

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• javascript - Detect if Google Analytics is loaded yet?

  - by Geuis

  I'm working on a project here that will store some info in Google Analytics custom variables. The script I'm building out needs to detect if GA has loaded yet before I can push data to it. The project is being designed to work across any kind of site that uses GA. The problem is reliably detecting if GA has finished loading or not and is available. A couple of variabilities here: 1) There's multiple methods of loading GA. Older scripts from the Urchin days up to the latest asynchronous scripts. Some of these are inline, some are asynchronous. Also, some sites do custom methods of loading GA, like at my job. We use YUI getScript to load it. 2) Variable-variable names. In some scripts, the variable name assigned to GA is "pageTracker". In others, its "_gaq". Then there's the infinity of custom variable names that sites could be using for their implementation of GA. So does anyone have any thoughts on what might be a reliable way to check if Google Analytics is being used on the page, and if it's been loaded?

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• In what order does DOJO handles ajax requests?

  - by mm2887

  Hi, Using a form in a dialog box I am using Dojo in jsp to save the form in my database. After that request is completed using dojo.xhrPost() I am sending in another request to update a dropdown box that should include the added form object that was just saved, but for some reason the request to update the dropdown is executed before saving the form in the database even though the form save is called first. Using Firebug I can see that the getLocations() request is completed before the sendForm() request. This is the code: Add Team sendForm("ajaxResult1", "addTeamForm"); dijit.byId("addTeamDialog").hide(); getLocations("locationsTeam"); </script> function sendForm(target, form){ var targetNode = dojo.byId(target); var xhrArgs = { form: form, url: "ajax", handleAs: "text", load: function(data) { targetNode.innerHTML = data; }, error: function(error) { targetNode.innerHTML = "An unexpected error occurred: " + error; } } //Call the asynchronous xhrGet var deferred = dojo.xhrPost(xhrArgs); } function getLocations(id) { var targetNode = dojo.byId(id); var xhrArgs = { url: "ajax", handleAs: "text", content: { location: "yes" }, load: function(data) { targetNode.innerHTML = data; }, error: function(error) { targetNode.innerHTML = "An unexpected error occurred: " + error; } } //Call the asynchronous xhrGet var deferred = dojo.xhrGet(xhrArgs); } Why is this happening? Is there way to make the first request complete first before the second executes? To reduce the possibilities of why this is happening I tried setting the cache property in xhrGet to false but the result is still the same. Please help!

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• JQuery Deferred - Adding to the Deferred contract

  - by MgSam

  I'm trying to add another asynchronous call to the contract of an existing Deferred before its state is set to success. Rather than try and explain this in English, see the following pseudo-code: $.when( $.ajax({ url: someUrl, data: data, async: true, success: function (data, textStatus, jqXhr) { console.log('Call 1 done.') jqXhr.pipe( $.ajax({ url: someUrl, data: data, async: true, success: function (data, textStatus, jqXhr) { console.log('Call 2 done.'); }, }) ); }, }), $.ajax({ url: someUrl, data: data, async: true, success: function (data, textStatus, jqXhr) { console.log('Call 3 done.'); }, }) ).then(function(){ console.log('All done!'); }); Basically, Call 2 is dependent on the results of Call 1. I want Call 1 and Call 3 to be executed in parallel. Once all 3 calls are complete, I want the All Done code to execute. My understanding is that Deferred.pipe() is supposed to chain another asynchronous call to the given deferred, but in practice, I always get Call 2 completing after All Done. Does anyone know how to get jQuery's Deferred to do what I want? Hopefully the solution doesn't involve ripping the code apart into chunks any further. Thanks for any help.

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• Manage multiple UDP calls

  - by rayman

  Hi all, I would like to have an advice for this issue: I am using Jbos 5.1.0, EJB3.0 I have system, which sending requests via UDP'S to remote modems, and suppose to wait for an answer from the target modem. the remote modems support only UDP calls, therefor I o design asynchronous mechanism. (also coz I want to request X modems parallel) this is what I try to do: all calls are retrieved from Data Base, then each call will be added as a message to JMS QUE. let's say i will set X MDB'S on that que, so I can work asynchronous. now each MDB will send UDP request to the IP-address(remote modem) which will be parsed from the que message. so basicly each MDB, which takes a message is sending a udp request to the remote modem and [b]waiting [/b]for an answer from that modem. [u]now here is the BUG:[/u] could happen a scenario where MDB will get an answer, but not from the right modem( which it requested in first place). that bad scenario cause two wrong things: a. the sender which sent the message will wait forever since the message never returned to him(it got accepted by another MDB). b. the MDB which received the message is not the right one, and probablly if it was on a "listener" mode, then it supposed to wait for an answer from diffrent sender.(else it wouldnt get any messages) so ofcourse I can handle everything with a RETRY mechanisem. so both mdb's(the one who got message from the wrong sender, and the one who never got the answer) will try again, to do thire operation with a hope that next time it will success. This is the mechanism, mybe you could tell me if there is any design pattren, or any other effective solution for this problem? Thanks, ray.

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• Timer Service in ejb 3.1 - schedule calling timeout problem

  - by Greg

  Hi Guys, I have created simple example with @Singleton, @Schedule and @Timeout annotations to try if they would solve my problem. The scenario is this: EJB calls 'check' function every 5 secconds, and if certain conditions are met it will create single action timer that would invoke some long running process in asynchronous fashion. (it's sort of queue implementation type of thing). It then continues to check, but as long as long running process is there it won't start another one. Below is the code I came up with, but this solution does not work, because it looks like asynchronous call I'm making is in fact blocking my @Schedule method. @Singleton @Startup public class GenerationQueue { private Logger logger = Logger.getLogger(GenerationQueue.class.getName()); private List<String> queue = new ArrayList<String>(); private boolean available = true; @Resource TimerService timerService; @Schedule(persistent=true, minute="*", second="*/5", hour="*") public void checkQueueState() { logger.log(Level.INFO,"Queue state check: "+available+" size: "+queue.size()+", "+new Date()); if (available) { timerService.createSingleActionTimer(new Date(), new TimerConfig(null, false)); } } @Timeout private void generateReport(Timer timer) { logger.info("!!--timeout invoked here "+new Date()); available = false; try { Thread.sleep(1000*60*2); // something that lasts for a bit } catch (Exception e) {} available = true; logger.info("New report generation complete"); } What am I missing here or should I try different aproach? Any ideas most welcome :) Testing with Glassfish 3.0.1 latest build - forgot to mention

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• Real time embeddable http server library required

  - by Howard May

  Having looked at several available http server libraries I have not yet found what I am looking for and am sure I can't be the first to have this set of requirements. I need a library which presents an API which is 'pipelined'. Pipelining is used to describe an HTTP feature where multiple HTTP requests can be sent across a TCP link at a time without waiting for a response. I want a similar feature on the library API where my application can receive all of those request without having to send a response (I will respond but want the ability to process multiple requests at a time to reduce the impact of internal latency). So the web server library will need to support the following flow 1) HTTP Client transmits http request 1 2) HTTP Client transmits http request 2 ... 3) Web Server Library receives request 1 and passes it to My Web Server App 4) My Web Server App receives request 1 and dispatches it to My System 5) Web Server receives request 2 and passes it to My Web Server App 6) My Web Server App receives request 2 and dispatches it to My System 7) My Web Server App receives response to request 1 from My System and passes it to Web Server 8) Web Server transmits HTTP response 1 to HTTP Client 9) My Web Server App receives response to request 2 from My System and passes it to Web Server 10) Web Server transmits HTTP response 2 to HTTP Client Hopefully this illustrates my requirement. There are two key points to recognise. Responses to the Web Server Library are asynchronous and there may be several HTTP requests passed to My Web Server App with responses outstanding. Additional requirements are Embeddable into an existing 'C' application Small footprint; I don't need all the functionality available in Apache etc. Efficient; will need to support thousands of requests a second Allows asynchronous responses to requests; their is a small latency to responses and given the required request throughput a synchronous architecture is not going to work for me. Support persistent TCP connections Support use with Server-Push Comet connections Open Source / GPL support for HTTPS Portable across linux, windows; preferably more. I will be very grateful for any recommendation Best Regards

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• asyncore callbacks launching threads... ok to do?

  - by sbartell

  I'm unfamiliar with asyncore, and have very limited knowledge of asynchronous programming except for a few intro to twisted tutorials. I am most familiar with threads and use them in all my apps. One particular app uses a couchdb database as its interface. This involves longpolling the db looking for changes and updates. The module I use for couchdb is couchdbkit. It uses an asyncore loop to watch for these changes and send them to a callback. So, I figure from this callback is where I launch my worker threads. It seems a bit crude to mix asynchronous and threaded programming. I really like couchdbkit, but would rather not introduce issues into my program. So, my question is, is it safe to fire threads from an async callback? Here's some code... {{{ def dispatch(change): global jobs, db_url # jobs is my queue db = Database(db_url) work_order = db.get(change['id']) # change is an id to the document that changed. # i need to get the actual document (workorder) worker = Worker(work_order, db) # fire the thread jobs.append[worker] worker.start() return main() . . . consumer.wait(cb=dispatch, since=update_seq, timeout=10000) #wait constains the asyncloop. }}}

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• Best way to catch a WCF exception in Silverlight?

  - by wahrhaft

  I have a Silverlight 2 application that is consuming a WCF service. As such, it uses asynchronous callbacks for all the calls to the methods of the service. If the service is not running, or it crashes, or the network goes down, etc before or during one of these calls, an exception is generated as you would expect. The problem is, I don't know how to catch this exception. Because it is an asynchronous call, I can't wrap my begin call with a try/catch block and have it pick up an exception that happens after the program has moved on from that point. Because the service proxy is automatically generated, I can't put a try/catch block on each and every generated function that calls EndInvoke (where the exception actually shows up). These generated functions are also surrounded by External Code in the call stack, so there's nowhere else in the stack to put a try/catch either. I can't put the try/catch in my callback functions, because the exception occurs before they would get called. There is an Application_UnhandledException function in my App.xaml.cs, which captures all unhandled exceptions. I could use this, but it seems like a messy way to do it. I'd rather reserve this function for the truly unexpected errors (aka bugs) and not end up with code in this function for every circumstance I'd like to deal with in a specific way. Am I missing an obvious solution? Or am I stuck using Application_UnhandledException? [Edit] As mentioned below, the Error property is exactly what I was looking for. What is throwing me for a loop is that the fact that the exception is thrown and appears to be uncaught, yet execution is able to continue. It triggers the Application_UnhandledException event and causes VS2008 to break execution, but continuing in the debugger allows execution to continue. It's not really a problem, it just seems odd.

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• Synchronous Android activities

  - by rayman

  Ive made mis-leading topic in my last question, so i open this new question to clear what I realy want. sorry for the inconvenience. I wanna run two system(Android) activities one after another in specific order from my main activity. now as we know, startActivity is an asynchronous operation, so i cant keep on a specific order. so i thought maybe I should try to do it with dialogBox in the middle but also running a dialogBox is an asynchronous. now as i said the activities which i try to run are Android activities, so i cant even start them with startActivityForResult (or mybe i can, but i dont get any result back to my main(calling) activity) Any tricks how could i manage with this issue? Some code: first activity: Intent intent = new Intent(); intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK); intent.setAction(Settings.ACTION_APPLICATION_SETTINGS); startActivity(intent); second activity: Intent intent = new Intent(Intent.ACTION_VIEW); intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK); intent.setDataAndType(Uri.fromFile(tmpPackageFile .getAbsoluteFile()), "application/vnd.android.package-archive"); startActivity(intent); as you can see, i dont have any access to those activites, i can just run thire intents from my main activity.

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• Open Source webapp that shows PC / Projector status in 30+ Lecture rooms

  - by Seanchán

  I am looking for a simple web application that only has a simple graphical representation of the current status of 30+ lecture rooms. I.e. Green = good, Red=bad i.e. PC or Projector not working. With a little message and a ETA as well. I am not looking for monitoring software, merely a way for a tech to flag a room as "technically challenged" until 1PM or until "Friday 10AM". With a message for those lecturers who are interested: "Waiting on replacement bulb" or "Power supply gone" I know this is a simple thing to code up yourself, but I am looking for something that has been around for a few years that has some cool extra little functionality that you wouldn't think of yourself. I just can't find anything like that out there. And just to be clear: not monitoring software, more like lecturer feedback web app.

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• mysql master-slave setup with synchronous replication

  - by imaginative

  I have a very trivial mysql master-slave setup going on between two servers. The problem is, replication is asynchronous, and this can cause issues (even on a low latency link), if the master server was to crash after a COMMIT before the replication thread from the slave was able to fetch the last bin log. Is there anyway to force mysql to do synchronous commits so that data consistency is guaranteed in a mysql-slave relationship?

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• Fast (non-blocking) way to transfer many files to another server

  - by Nyxynyx

  I am currently attempting to transfer over 1 million files from one server to another. Using wget, it seems to be extremely slow, probably because it starts a new transfer after the previous one has been completed. Question: Is there a faster non-blocking (asynchronous) way to do the transfer? I do not have enough space on the first server to compress the files into tar.gz and transferring them over. Thanks!

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• Weird TPS peaks on SQL 2005 replicated database.

  - by SuperCoolMoss

  When monitoring the Transactions/Sec using perfmon on one of my SQL2005 replicated databases - I'm seeing the TPS increase to 1000 and then immediately drop back down again - this happens every 5 seconds. I'm not sure what's causing this - is this something to do with replication? We also have asynchronous statistics set on this particular database. I've tried profiling when the users are not connected - but nothing is writing to the database. ADDED PICTURE AND BOUNTY

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• Why does starting a process in the background prevent me from recalling previous commands in the command prompt?

  - by leeand00

  I'm running asynchronous command prompt commands in cmd on Windows 7 64-bit and for some reason it effects my ability to recall previous commands just after I run them; for example: I might run something like: start /B rmdir /Q /S .\some_massive_directory And next I try to press the up arrow to recall the text of the previous command..but nothing happens...is this because whatever data structure is holding my commands is locked by the process I sent to the background, or is it because I am using a network mapped drive to run my command on?

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• Technical details for Server 2012 de-duplication feature

  - by syneticon-dj

  Now that Windows Server 2012 comes with de-duplication features for NTFS volumes I am having a hard time finding technical details about it. I can deduce from the TechNet documentation that the de-duplication action itself is an asynchronous process - not unlike how the SIS Groveler used to work - but there is virtually no detail about the implementation (algorithms used, resources needed, even the info on performance considerations is nothing but a bunch rule-of-thumb-style recommendations). Insights and pointers are greatly appreciated, a comparison to Solaris' ZFS de-duplication efficiency for a set of scenarios would be wonderful.

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• Microsoft guarantees the performance of SQL Server

  - by simonsabin

  I have recently been informed that Microsoft will be guaranteeing the performance of SQL Server. Yes thats right Microsoft will guarantee that you will get better performance out of SQL Server that any other competitor system. However on the flip side there are also saying that end users also have to guarantee the performance of SQL Server if they want to use the next release of SQL Server targeted for 2011 or 2012. It appears that a recent recruit Mark Smith from Newcastle, England will be heading a new team that will be making sure you are running SQL Server on adequate hardware and making sure you are developing your applications according to best practices. The Performance Enforcement Team (SQLPET) will be a global group headed by mark that will oversee two other groups the existing Customer Advisory Team (SQLCAT) and another new team the Design and Operation Group (SQLDOG). Mark informed me that the team was originally thought out during Yukon and was going to be an independent body that went round to customers making sure they didn’t suffer performance problems. However it was felt that they needed to wait a few releases until SQL Server was really there. The original Yukon Independent Performance Enhancement Team (YIPET) has now become the SQL Performance Enforcement Team (SQLPET). When challenged about the change from enhancement to enforcement Mark was unwilling to comment. An anonymous source suggested that "..Microsoft is sick of the bad press SQL Server gets for performance when the performance problems are normally down to people developing applications badly and using inadequate hardware..." Its true that it is very easy to install and run SQL, unlike other RDMS systems and the flip side is that its also easy to get into performance problems due to under specified hardware and bad design. Its not yet confirmed if this enforcement will apply to all SKUs or just the high end ones. I would personally welcome some level of architectural and hardware advice service that clients would be able to turn to, in order to justify getting the appropriate hardware at the start of a project and not 1 year in when its often too late.

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