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• NoHostAvailableException With Cassandra & DataStax Java Driver If Large ResultSet

  - by hughj

  The setup: 2-node Cassandra 1.2.6 cluster replicas=2 very large CQL3 table with no secondary index Rowkey is a UUID.randomUUID().toString() read consistency set to ONE Using DataStax java driver 1.0 The request: Attempting to do a table scan by "SELECT some-col from schema.table LIMIT nnn;" The fail: Once I go beyond a certain nnn LIMIT, I start to get NoHostAvailableExceptions from the driver. It reads like this: com.datastax.driver.core.exceptions.NoHostAvailableException: All host(s) tried for query failed (tried: /10.181.13.239 ([/10.181.13.239] Unexpected exception triggered)) at com.datastax.driver.core.exceptions.NoHostAvailableException.copy(NoHostAvailableException.java:64) at com.datastax.driver.core.ResultSetFuture.extractCauseFromExecutionException(ResultSetFuture.java:214) at com.datastax.driver.core.ResultSetFuture.getUninterruptibly(ResultSetFuture.java:169) at com.jpmc.es.rtm.storage.impl.EventExtract.main(EventExtract.java:36) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:601) at com.intellij.rt.execution.application.AppMain.main(AppMain.java:120) Caused by: com.datastax.driver.core.exceptions.NoHostAvailableException: All host(s) tried for query failed (tried: /10.181.13.239 ([/10.181.13.239] Unexpected exception triggered)) at com.datastax.driver.core.RequestHandler.sendRequest(RequestHandler.java:98) at com.datastax.driver.core.RequestHandler$1.run(RequestHandler.java:165) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603) Given: This is probably not the most enlightened thing to do to a large table with millions of rows, but this is how I learn what not to do, so I would really appreciate someone who could volunteer how this kind of error can be debugged. For example, when this happens, there are no indications that the nodes in the cluster ever had an issue with the request (there is nothing in the logs on either node that indicate any timeout or failure). Also, I enabled the trace on the driver, which gives you some nice autotrace (ala Oracle) info as long as the query succeeds. But in this case, the driver blows a NoHostAvailableException and no ExecutionInfo is available, so tracing has not provided any benefit in this case. I also find it interesting that this does not seem to be recorded as a timeout (my JMX consoles tell me no timeouts have occurred). So, I am left not understanding WHERE the failure is actually occurring. I am left with the idea that it is the driver that is having a problem, but I don't know how to debug it (and I would really like to). I have read several posts from folks that state that query'g for resultSets 10000 rows is probably not a good idea, and I am willing to accept this, but I would like to understand what is causing the exception and where the exception is happening. FWIW, I also tried bumping the timeout properties in the cassandra.yaml, but this made no difference whatsoever. I welcome any suggestions, anecdotes, insults, or monetary contributions for my registration in the house of moron-developers. Regards!!

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• Creating thousands of records in Rails

  - by willCosgrove

  Let me set the stage: My application deals with gift cards. When we create cards they have to have a unique string that the user can use to redeem it with. So when someone orders our gift cards, like a retailer, we need to make a lot of new card objects and store them in the DB. With that in mind, I'm trying to see how quickly I can have my application generate 100,000 Cards. Database expert, I am not, so I need someone to explain this little phenomena: When I create 1000 Cards, it takes 5 seconds. When I create 100,000 cards it should take 500 seconds right? Now I know what you're wanting to see, the card creation method I'm using, because the first assumption would be that it's getting slower because it's checking the uniqueness of a bunch of cards, more as it goes along. But I can show you my rake task desc "Creates cards for a retailer" task :order_cards, [:number_of_cards, :value, :retailer_name] => :environment do |t, args| t = Time.now puts "Searching for retailer" @retailer = Retailer.find_by_name(args[:retailer_name]) puts "Retailer found" puts "Generating codes" value = args[:value].to_i number_of_cards = args[:number_of_cards].to_i codes = [] top_off_codes(codes, number_of_cards) while codes != codes.uniq codes.uniq! top_off_codes(codes, number_of_cards) end stored_codes = Card.all.collect do |c| c.code end while codes != (codes - stored_codes) codes -= stored_codes top_off_codes(codes, number_of_cards) end puts "Codes are unique and generated" puts "Creating bundle" @bundle = @retailer.bundles.create!(:value => value) puts "Bundle created" puts "Creating cards" @bundle.transaction do codes.each do |code| @bundle.cards.create!(:code => code) end end puts "Cards generated in #{Time.now - t}s" end def top_off_codes(codes, intended_number) (intended_number - codes.size).times do codes << ReadableRandom.get(CODE_LENGTH) end end I'm using a gem called readable_random for the unique code. So if you read through all of that code, you'll see that it does all of it's uniqueness testing before it ever starts creating cards. It also writes status updates to the screen while it's running, and it always sits for a while at creating. Meanwhile it flies through the uniqueness tests. So my question to the stackoverflow community is: Why is my database slowing down as I add more cards? Why is this not a linear function in regards to time per card? I'm sure the answer is simple and I'm just a moron who knows nothing about data storage. And if anyone has any suggestions, how would you optimize this method, and how fast do you think you could get it to create 100,000 cards? (When I plotted out my times on a graph and did a quick curve fit to get my line formula, I calculated how long it would take to create 100,000 cards with my current code and it says 5.5 hours. That maybe completely wrong, I'm not sure. But if it stays on the line I curve fitted, it would be right around there.)

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• Exporting a report from Crystal 8.5 causes the report to first refresh, then export, with unexpected

  - by LittleBobbyTables

  We have a VB6 application that can generate reports using the Crystal Reports 8.5 runtime. To generate one of the more complicated reports we have, the VB app does the following: Deletes records from a SQL table (we'll call it Foo) based on the session ID of the user Performs a select statement, and populates the Foo table with the contents of the select statement. Massages the data in Foo. Executes the report (we'll call it Bar). The Bar report uses the Foo table as part of some outer joins to get some descriptions. After the report is opened and populated, the code then deletes the records in Foo. If you ever look in Foo there will be no data since it is always purged at the end, but the Crystal Report will still have the data, since Foo wasn't cleared out until after the report ran. Most sites can export this report afterwards, to either PDF or Excel, with no issue. One site, however, has two servers in production where if you attempt to export the Bar report (doesn't matter what format it is exported to), the report will visibly refresh and then export the report in the requested format. This refresh, however, causes the exported data to be invalid because the report is still doing the outer joins to the Foo table, which is now empty. I'm at a total loss why the report refreshes before printing on these two servers. One server has Crystal Reports 8.5 installed on it as well as the Crystal Reports 8.5 runtime (so they can modify reports). The other server only has the Crystal Reports 8.5 runtime (so you can generate reports from the VB application, but can't modify them on that server). Both of the servers belong to a French site. Another support staff here said the issue sounded vaguely familiar to an issue a few years ago, and suggested re-registering DLLs. I have tried unregistering and re-registering the following DLLs out of frustration: Crystl32.ocx crxlat32.dll cpeau32.dll exportmodeller.dll crtslv.dll atl.dll Unregistering and re-registering the above DLLs does not fix the issue. If we take the problem report, and run it on any of our development or QA servers, we have no issues; the report does NOT refresh before exporting, and the data looks consistent. It seems like a server or regional setting may be causing this, but what could possibly cause the report to refresh before exporting on only two of our servers? The most obvious solution is to simply alter the code so the Foo table isn't purged after the report is run, only when the report is run, but this is a production issue, the customer wants a fix now, and there's quite a few hoops to jump through to make the change.

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• Activity Indicator not displaying based on whether the UIWebView is loading or not...

  - by Jack W-H

  Hi folks Sorry if this is an easy one. Basically, here is my code: MainViewController.h: // // MainViewController.h // Site // // Created by Jack Webb-Heller on 19/03/2010. // Copyright __MyCompanyName__ 2010. All rights reserved. // #import "FlipsideViewController.h" @interface MainViewController : UIViewController <UIWebViewDelegate, FlipsideViewControllerDelegate> { IBOutlet UIWebView *webView; IBOutlet UIActivityIndicatorView *spinner; } - (IBAction)showInfo; @property(nonatomic,retain) UIWebView *webView; @property(nonatomic,retain) UIActivityIndicatorView *spinner; @end MainViewController.m: // // MainViewController.m // Site // // Created by Jack Webb-Heller on 19/03/2010. // Copyright __MyCompanyName__ 2010. All rights reserved. // #import "MainViewController.h" #import "MainView.h" @implementation MainViewController @synthesize webView; @synthesize spinner; - (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil { if (self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil]) { // Custom initialization } return self; } // Implement viewDidLoad to do additional setup after loading the view, typically from a nib. - (void)viewDidLoad { NSURL *siteURL; NSString *siteURLString; siteURLString=[[NSString alloc] initWithString:@"http://www.site.com"]; siteURL=[[NSURL alloc] initWithString:siteURLString]; [webView loadRequest:[NSURLRequest requestWithURL:siteURL]]; [siteURL release]; [siteURLString release]; [super viewDidLoad]; } - (void)flipsideViewControllerDidFinish:(FlipsideViewController *)controller { [self dismissModalViewControllerAnimated:YES]; } - (void)webViewDidFinishLoad:(UIWebView *)webView { [spinner stopAnimating]; spinner.hidden=FALSE; NSLog(@"viewDidFinishLoad went through nicely"); } - (void)webViewDidStartLoad:(UIWebView *)webView { [spinner startAnimating]; spinner.hidden=FALSE; NSLog(@"viewDidStartLoad seems to be working"); } - (IBAction)showInfo { FlipsideViewController *controller = [[FlipsideViewController alloc] initWithNibName:@"FlipsideView" bundle:nil]; controller.delegate = self; controller.modalTransitionStyle = UIModalTransitionStyleFlipHorizontal; [self presentModalViewController:controller animated:YES]; [controller release]; } - (void)didReceiveMemoryWarning { // Releases the view if it doesn't have a superview. [super didReceiveMemoryWarning]; // Release any cached data, images, etc that aren't in use. } - (void)viewDidUnload { // Release any retained subviews of the main view. // e.g. self.myOutlet = nil; } - (void)dealloc { [spinner release]; [webView release]; [super dealloc]; } @end Unfortunately nothing is ever written to my log, and for some reason the Activity Indicator never seems to appear. What's going wrong here? Thanks folks Jack

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• How can I use Web Services Core to send a complex type as a parameter to a SOAP API method

  - by Matthew Brindley

  I don't do much Cocoa programming, so I'm probably missing something obvious, so please excuse the basic question. I have a SOAP method that expects a complex type as a paramater. Here's some WSDL: <s:element name="SaveTestResult"> <s:complexType> <s:sequence> <s:element minOccurs="0" maxOccurs="1" name="result" type="tns:TestItemResponse" /> </s:sequence> </s:complexType> </s:element> Here's the definition of the complex type "TestItemResponse": <s:complexType name="TestItemResponse"> <s:sequence> <s:element minOccurs="1" maxOccurs="1" name="TestItemRequestId" type="s:int" /> <s:element minOccurs="1" maxOccurs="1" name="ExternalId" type="s:int" /> <s:element minOccurs="0" maxOccurs="1" name="ApiId" type="s:string" /> <s:element minOccurs="0" maxOccurs="1" name="InboxGuid" type="s:string" /> <s:element minOccurs="0" maxOccurs="1" name="SpamResult" type="tns:SpamResult" /> <s:element minOccurs="0" maxOccurs="1" name="ResultImageSet" type="tns:ResultImageSet" /> <s:element minOccurs="1" maxOccurs="1" name="ExclusiveUseMailAccountId" type="s:int" /> <s:element minOccurs="1" maxOccurs="1" name="State" type="tns:TestItemResponseState" /> <s:element minOccurs="0" maxOccurs="1" name="ErrorShortDescription" type="s:string" /> <s:element minOccurs="0" maxOccurs="1" name="ErrorFullDescription" type="s:string" /> </s:sequence> </s:complexType> I've been using Web Services Core to call a SOAP API method that requires a simple string param, that works great. That same method returns a complex type which WSC converted into nested NSDictionaries, so no problems there. So I assumed I'd be able to convert my local TestItemResponse class into an NSDictionary and then use that as the complex type param. It almost worked, but unfortunately WSC set the object's type as "Dictionary", instead of "TestItemResponse", and the server complained. <TestItemResponse xsi:type=\"SOAP-ENC:Dictionary\"> <ErrorFullDescription xsi:type=\"xsd:string\">foo</ErrorFullDescription> ... I can't seem to find anything that allows you to override the type WSC assigns to the element in the SOAP XML. I've been using code adapted from here, I'm happy to list it, it's just quite long and this is already the longest SO question I've ever posted.

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• List all possible combinations of k integers between 1...n (n choose k)

  - by Asaf R

  Hi, Out of no particular reason I decided to look for an algorithm that produces all possible choices of k integers between 1...n, where the order amongst the k integer doesn't matter (the n choose k thingy). From the exact same reason, which is no reason at all, I also implemented it in C#. My question is: Do you see any mistake in my algorithm or code? And, more importantly, can you suggest a better algorithm? Please pay more attention to the algorithm than the code itself. It's not the prettiest code I've ever written, although do tell if you see an error. EDIT: Alogirthm explained - We hold k indices. This creates k nested for loops, where loop i's index is indices[i]. It simulates k for loops where indices[i+1] belongs to a loop nested within the loop of indices[i]. indices[i] runs from indices[i - 1] + 1 to n - k + i + 1. CODE: public class AllPossibleCombination { int n, k; int[] indices; List<int[]> combinations = null; public AllPossibleCombination(int n_, int k_) { if (n_ <= 0) { throw new ArgumentException("n_ must be in N+"); } if (k_ <= 0) { throw new ArgumentException("k_ must be in N+"); } if (k_ > n_) { throw new ArgumentException("k_ can be at most n_"); } n = n_; k = k_; indices = new int[k]; indices[0] = 1; } /// <summary> /// Returns all possible k combination of 0..n-1 /// </summary> /// <returns></returns> public List<int[]> GetCombinations() { if (combinations == null) { combinations = new List<int[]>(); Iterate(0); } return combinations; } private void Iterate(int ii) { // // Initialize // if (ii > 0) { indices[ii] = indices[ii - 1] + 1; } for (; indices[ii] <= (n - k + ii + 1); indices[ii]++) { if (ii < k - 1) { Iterate(ii + 1); } else { int[] combination = new int[k]; indices.CopyTo(combination, 0); combinations.Add(combination); } } } } I apologize for the long question, it might be fit for a blog post, but I do want the community's opinion here. Thanks, Asaf

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• Booking form works but does not give feedback

  - by Naim

  I have a form where people can book seats for a given event. It's actually a WordPress plugin. When someone sends his booking, email notifications are sent properly and the event booking status is updated accordingly. The issue is that the booking form does not give any feedback whatsoever. Once you hit "book now", the graphic keeps loading and no feedback is ever displayed like for instance "booking sent successfully" or "there are errors in your form", even though the booking is saved correctly with both sides notified by email. I guess it's a JavaScript issue,Firebug console is not showing any error... So here is the code source of the booking form : Also please experience the issue live Here username: tester password: testsa Thanks! $('#em-booking-form').submit( function(e){ e.preventDefault(); var em_booking_doing_ajax = false; $.ajax({ url: EM.bookingajaxurl, data:$('#em-booking-form').serializeArray(), dataType: 'jsonp', type:'post', beforeSend: function(formData, jqForm, options) { if(em_booking_doing_ajax){ alert(EM.bookingInProgress); return false; } em_booking_doing_ajax = true; $('.em-booking-message').remove(); $('#em-booking').append('<div id="em-loading"></div>'); }, success : function(response, statusText, xhr, $form) { $('#em-loading').remove(); $('.em-booking-message').remove(); $('.em-booking-message').remove(); //show error or success message if(response.result){ $('<div class="em-booking-message-success em-booking-message">'+response.message+'</div>').insertBefore('#em-booking-form'); $('#em-booking-form').hide(); $('.em-booking-login').hide(); $(document).trigger('em_booking_success', [response]); }else{ if( response.errors != null ){ if( $.isArray(response.errors) && response.errors.length > 0 ){ var error_msg; response.errors.each(function(i, el){ error_msg = error_msg + el; }); $('<div class="em-booking-message-error em-booking-message">'+error_msg.errors+'</div>').insertBefore('#em-booking-form'); }else{ $('<div class="em-booking-message-error em-booking-message">'+response.errors+'</div>').insertBefore('#em-booking-form'); } }else{ $('<div class="em-booking-message-error em-booking-message">'+response.message+'</div>').insertBefore('#em-booking-form'); } } $('html, body').animate({ scrollTop: $("#em-booking").first().offset().top - 50 }); //sends user back to top of form //run extra actions after showing the message here if( response.gateway != null ){ $(document).trigger('em_booking_gateway_add_'+response.gateway, [response]); } if( !response.result && typeof Recaptcha != 'undefined'){ Recaptcha.reload(); } }, complete : function(){ em_booking_doing_ajax = false; $('#em-loading').remove(); } }); return false; });

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• NSZombieEnabled breaking working code?

  - by Gordon Fontenot

  I have the following method in UIImageManipulation.m: +(UIImage *)scaleImage:(UIImage *)source toSize:(CGSize)size { UIImage *scaledImage = nil; if (source != nil) { UIGraphicsBeginImageContext(size); [source drawInRect:CGRectMake(0, 0, size.width, size.height)]; scaledImage = UIGraphicsGetImageFromCurrentImageContext(); UIGraphicsEndImageContext(); } return scaledImage; } I am calling it in a different view with: imageFromFile = [UIImageManipulator scaleImage:imageFromFile toSize:imageView.frame.size]; (imageView is a UIImageView allocated earlier) This is working great in my code. I resizes the image perfectly, and throws zero errors. I also don't have anything pop up under build - analyze. But the second I turn on NSZombieEnabled to debug a different EXC_BAD_ACCESS issue, the code breaks. Every single time. I can turn NSZombieEnabled off, code runs great. I turn it on, and boom. Broken. I comment out the call, and it works again. Every single time, it gives me an error in the console: -[UIImage release]: message sent to deallocated instance 0x3b1d600. This error doesn't appear if `NSZombieEnabled is turned off. Any ideas? --EDIT-- Ok, This is killing me. I have stuck breakpoints everywhere I can, and I still cannot get a hold of this thing. Here is the full code when I call the scaleImage method: -(void)setupImageButton { UIImage *imageFromFile; if (object.imageAttribute == nil) { imageFromFile = [UIImage imageNamed:@"no-image.png"]; } else { imageFromFile = object.imageAttribute; } UIImage *scaledImage = [UIImageManipulator scaleImage:imageFromFile toSize:imageButton.frame.size]; UIImage *roundedImage = [UIImageManipulator makeRoundCornerImage:scaledImage :10 :10 withBorder:YES]; [imageButton setBackgroundImage:roundedImage forState:UIControlStateNormal]; } The other UIImageManipulator method (makeRoundCornerImage) shouldn't be causing the error, but just in case I'm overlooking something, I threw the entire file up on github here. It's something about this method though. Has to be. If I comment it out, it works great. If I leave it in, Error. But it doesn't throw errors with NSZombieEnabled turned off ever.

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• Should Application_End fire on an automatic App Pool Recycle?

  - by Laramie

  I have read this, this, this and this plus a dozen other posts/blogs. I have an ASP.Net app in shared hosting that is frequently recycling. We use NLog and have the following code in global.asax void Application_Start(object sender, EventArgs e) { NLog.Logger logger = NLog.LogManager.GetCurrentClassLogger(); logger.Debug("\r\n\r\nAPPLICATION STARTING\r\n\r\n"); } protected void Application_OnEnd(Object sender, EventArgs e) { NLog.Logger logger = NLog.LogManager.GetCurrentClassLogger(); logger.Debug("\r\n\r\nAPPLICATION_OnEnd\r\n\r\n"); } void Application_End(object sender, EventArgs e) { HttpRuntime runtime = (HttpRuntime)typeof(System.Web.HttpRuntime).InvokeMember("_theRuntime", BindingFlags.NonPublic | BindingFlags.Static | BindingFlags.GetField, null, null, null); if (runtime == null) return; string shutDownMessage = (string)runtime.GetType().InvokeMember("_shutDownMessage", BindingFlags.NonPublic | BindingFlags.Instance | BindingFlags.GetField, null, runtime, null); string shutDownStack = (string)runtime.GetType().InvokeMember("_shutDownStack", BindingFlags.NonPublic | BindingFlags.Instance | BindingFlags.GetField, null, runtime, null); ApplicationShutdownReason shutdownReason = System.Web.Hosting.HostingEnvironment.ShutdownReason; NLog.Logger logger = NLog.LogManager.GetCurrentClassLogger(); logger.Debug(String.Format("\r\n\r\nAPPLICATION END\r\n\r\n_shutDownReason = {2}\r\n\r\n _shutDownMessage = {0}\r\n\r\n_shutDownStack = {1}\r\n\r\n", shutDownMessage, shutDownStack, shutdownReason)); } void Application_Error(object sender, EventArgs e) { NLog.Logger logger = NLog.LogManager.GetCurrentClassLogger(); logger.Debug("\r\n\r\nApplication_Error\r\n\r\n"); } Our log file is littered with "APPLICATION STARTING" entries, but neither Application_OnEnd, Application_End, nor Application_Error are ever fired during these spontaneous restarts. I know they are working because there are entries for touching the web.config or /bin files. We also ran a memory overload test and can trigger an OutOfMemoryException which is caught in Application_Error. We are trying to determine whether the virtual memory limit is causing the recycling. We have added GC.GetTotalMemory(false) throughout the code, but this is for all of .Net, not just our App´s pool, correct? We've also tried var oPerfCounter = new PerformanceCounter(); oPerfCounter.CategoryName = "Process"; oPerfCounter.CounterName = "Virtual Bytes"; oPerfCounter.InstanceName = "iisExpress"; logger.Debug("Virtual Bytes: " + oPerfCounter.RawValue + " bytes"); but don't have permission in shared hosting. I've monitored the app on a dev server with the same requests that caused the recycles in production with ANTS Memory Profiler attached and can't seem to find a culprit. We have also run it with a debugger attached in dev to check for uncaught exceptions in spawned threads that might cause the app to abort. My questions are these: How can I effectively monitor memory usage in shared hosting to tell how much my application is consuming prior to an application recycle? Why are the Application_[End/OnEnd/Error] handlers in global.asax not being called? How else can I determine what is causing these recycles? Thanks.

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• Is it worth moving from stored procedures to linq ?

  - by Josef

  I'm looking at standardizing programming in an organisaiton. Half uses stored procedures and the other half Linq. From what i've read there is still some debate going on on this topic. My concern is that MS is trying to slip in it's own proprietry query language 'linq' to make SQL redundant. If a few years back microsoft had tried to win customers from oracle and sybase with their MSSQL database and stated that it didn't use SQL by their own proprietry query langues ie linq. I doubt many would have switched. I believe that is exactly what is happening now by introducting it into the applicaiton business layer. I have used MS for many years but there is one gripe that I have with them and that is that they change their direction a lot. By a lot I mean new releases of .net, silverlight etc are more than 30% different from previous version. So by the time you become productive a new release is on the way. As things stand now a web developer using .net would need to know either vb.net or c#, xml, xaml,javascript,html, sql and now linq. That doesn't make for good productivity in my books. My concern is that once we all start using linq MS will start changing it between releases. and it will become an ever changing landscape. I believe that 'linq to sql' has already been deprecated. At leas with SQL we are dealing with a more stable and standardized language. Are we looking at a programming revolution or a marketing campaign? As far as I know other languages like Cobol have stayed the same for years. A cobol program from 20 years ago could pick up todays code and start working on it. Could a Vb3 person work on a modern .net web app ? Would these large changes need to be made if the underlying original foundation had been sound ? I worry about following MS shaking roadmap with it's deadends and double backs. are there any architects out there who feel the same ? regards Josef

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• Java Hardware Acceleration

  - by Freezerburn

  I have been spending some time looking into the hardware acceleration features of Java, and I am still a bit confused as none of the sites that I found online directly and clearly answered some of the questions I have. So here are the questions I have for hardware acceleration in Java: 1) In Eclipse version 3.6.0, with the most recent Java update for Mac OS X (1.6u10 I think), is hardware acceleration enabled by default? I read somewhere that someCanvas.getGraphicsConfiguration().getBufferCapabilities().isPageFlipping() is supposed to give an indication of whether or not hardware acceleration is enabled, and my program reports back true when that is run on my main Canvas instance for drawing to. If my hardware acceleration is not enabled now, or by default, what would I have to do to enable it? 2) I have seen a couple articles here and there about the difference between a BufferedImage and VolatileImage, mainly saying that VolatileImage is the hardware accelerated image and is stored in VRAM for fast copy-from operations. However, I have also found some instances where BufferedImage is said to be hardware accelerated as well. Is BufferedImage hardware accelerated as well in my environment? What would be the advantage of using a VolatileImage if both types are hardware accelerated? My main assumption for the advantage of having a VolatileImage in the case of both having acceleration is that VolatileImage is able to detect when its VRAM has been dumped. But if BufferedImage also support acceleration now, would it not have the same kind of detection built into it as well, just hidden from the user, in case that the memory is dumped? 3) Is there any advantage to using someGraphicsConfiguration.getCompatibleImage/getCompatibleVolatileImage() as opposed to ImageIO.read() In a tutorial I have been reading for some general concepts about setting up the rendering window properly (tutorial) it uses the getCompatibleImage method, which I believe returns a BufferedImage, to get their "hardware accelerated" images for fast drawing, which ties into question 2 about if it is hardware accelerated. 4) This is less hardware acceleration, but it is something I have been curious about: do I need to order which graphics get drawn? I know that when using OpenGL via C/C++ it is best to make sure that the same graphic is drawn in all the locations it needs to be drawn at once to reduce the number of times the current texture needs to be switch. From what I have read, it seems as if Java will take care of this for me and make sure things are drawn in the most optimal fashion, but again, nothing has ever said anything like this clearly. 5) What AWT/Swing classes support hardware acceleration, and which ones should be used? I am currently using a class that extends JFrame to create a window, and adding a Canvas to it from which I create a BufferStrategy. Is this good practice, or is there some other type of way I should be implementing this? Thank you very much for your time, and I hope I provided clear questions and enough information for you to answer my several questions.

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• Explanation of converting exporting an XML document as a relational database using XSLT

  - by Yaaqov

  I would like to better understand the basic steps needed to a take an XML document like this Breakfast Menu... <?xml version="1.0" encoding="ISO-8859-1"?> <breakfast_menu> <food> <name>Belgian Waffles</name> <price>$5.95</price> <description>two of our famous Belgian Waffles with plenty of real maple syrup</description> <calories>650</calories> </food> <food> <name>Strawberry Belgian Waffles</name> <price>$7.95</price> <description>light Belgian waffles covered with strawberries and whipped cream</description> <calories>900</calories> </food> <food> <name>Berry-Berry Belgian Waffles</name> <price>$8.95</price> <description>light Belgian waffles covered with an assortment of fresh berries and whipped cream</description> <calories>900</calories> </food> <food> <name>French Toast</name> <price>$4.50</price> <description>thick slices made from our homemade sourdough bread</description> <calories>600</calories> </food> <food> <name>Homestyle Breakfast</name> <price>$6.95</price> <description>two eggs, bacon or sausage, toast, and our ever-popular hash browns</description> <calories>950</calories> </food> </breakfast_menu> And "export" it to say, an Access or MySQL database using XSLT, creating two joined tables: Table: breakfast_menu Field: menu_item_id Field: food_id Table: food Field: food_id Field: name Field: price Field: description Field: calories If there are online tutorials on this that you know of, I'd be interesting in learning more, as well. Thanks.

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• Why is my javascript function sometimes "not defined"?

  - by harpo

  Problem: I call my javascript function, and sometimes I get the error 'myFunction is not defined'. But it is defined. For example. I'll occasionally get 'copyArray is not defined' even in this example: function copyArray( pa ) { var la = []; for (var i=0; i < pa.length; i++) la.push( pa[i] ); return la; } Function.prototype.bind = function( po ) { var __method = this; var __args = []; // sometimes errors -- in practice I inline the function as a workaround __args = copyArray( arguments ); return function() { /* bind logic omitted for brevity */ } } As you can see, copyArray is defined right there, so this can't be about the order in which script files load. I've been getting this in situations that are harder to work around, where the calling function is located in another file that should be loaded after the called function. But this was the simplest case I could present, and appears to be the same problem. It doesn't happen 100% of the time, so I do suspect some kind of load-timing-related problem. But I have no idea what. @Hojou: That's part of the problem. The function in which I'm now getting this error is itself my addLoadEvent, which is basically a standard version of the common library function. @James: I understand that, and there is no syntax error in the function. When that is the case, the syntax error is reported as well. In this case, I am getting only the 'not defined' error. @David: The script in this case resides in an external file that is referenced using the normal <script src="file.js"></script> method in the page's head section. @Douglas: Interesting idea, but if this were the case, how could we ever call a user-defined function with confidence? In any event, I tried this and it didn't work. @sk: This technique has been tested across browsers and is basically copied from the prototype library.

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• How to avoid this PDO exception: Cannot execute queries while other unbuffered queries are active

  - by Vittorio Vittori

  Hi, I'd like to print a simple table in my page with 3 columns, building name, tags and architecture style. If I try to retrieve the list of building names and arch. styles there is no problem: SELECT buildings.name, arch_styles.style_name FROM buildings INNER JOIN buildings_arch_styles ON buildings.id = buildings_arch_styles.building_id INNER JOIN arch_styles ON arch_styles.id = buildings_arch_styles.arch_style_id LIMIT 0, 10 My problem starts on retreaving the first 5 tags for every building of the query I've just wrote. SELECT DISTINCT name FROM tags INNER JOIN buildings_tags ON buildings_tags.tag_id = tags.id AND buildings_tags.building_id = 123 LIMIT 0, 5 The query itself works perfectly, but not where I thought to use it: <?php // pdo connection allready active, i'm using mysql $pdo_conn->setAttribute(PDO::MYSQL_ATTR_USE_BUFFERED_QUERY, true); $sql = "SELECT buildings.name, buildings.id, arch_styles.style_name FROM buildings INNER JOIN buildings_arch_styles ON buildings.id = buildings_arch_styles.building_id INNER JOIN arch_styles ON arch_styles.id = buildings_arch_styles.arch_style_id LIMIT 0, 10"; $buildings_stmt = $pdo_conn->prepare ($sql); $buildings_stmt->execute (); $buildings = $buildings_stmt->fetchAll (PDO::FETCH_ASSOC); $sql = "SELECT DISTINCT name FROM tags INNER JOIN buildings_tags ON buildings_tags.tag_id = tags.id AND buildings_tags.building_id = :building_id LIMIT 0, 5"; $tags_stmt = $pdo_conn->prepare ($sql); $html = "<table>"; // i'll use it to print my table foreach ($buildings as $building) { $name = $building["name"]; $style = $building["style_name"]; $id = $building["id"]; $tags_stmt->bindParam (":building_id", $id, PDO::PARAM_INT); $tags_stmt->execute (); // the problem is HERE $tags = $tags_stmt->fetchAll (PDO::FETCH_ASSOC); $html .= "... $name ... $style"; foreach ($tags as $current_tag) { $tag = $current_tag["name"]; $html .= "... $tag ..."; // let's suppose this is an area of the table where I print the first 5 tags per building } } $html .= "...</table>"; print $html; I'm not experienced on queries, so i though something like this, but it throws the error: PHP Fatal error: Uncaught exception 'PDOException' with message 'SQLSTATE[HY000]: General error: 2014 Cannot execute queries while other unbuffered queries are active. Consider using PDOStatement::fetchAll(). Alternatively, if your code is only ever going to run against mysql, you may enable query buffering by setting the PDO::MYSQL_ATTR_USE_BUFFERED_QUERY attribute. What can I do to avoid this? Should I change all and search a different way to get this kind of queries?

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• NSTimer as a self-targeting ivar.

  - by Matt Wilding

  I have come across an awkward situation where I would like to have a class with an NSTimer instance variable that repeatedly calls a method of the class as long as the class is alive. For illustration purposes, it might look like this: // .h @interface MyClock : NSObject { NSTimer* _myTimer; } - (void)timerTick; @end - // .m @implementation MyClock - (id)init { self = [super init]; if (self) { _myTimer = [[NSTimer scheduledTimerWithTimeInterval:1.0f target:self selector:@selector(timerTick) userInfo:nil repeats:NO] retain]; } return self; } - (void)dealloc { [_myTimer invalidate]; [_myTImer release]; [super dealloc]; } - (void)timerTick { // Do something fantastic. } @end That's what I want. I don't want to to have to expose an interface on my class to start and stop the internal timer, I just want it to run while the class exists. Seems simple enough. But the problem is that NSTimer retains its target. That means that as long as that timer is active, it is keeping the class from being dealloc'd by normal memory management methods because the timer has retained it. Manually adjusting the retain count is out of the question. This behavior of NSTimer seems like it would make it difficult to ever have a repeating timer as an ivar, because I can't think of a time when an ivar should retain its owning class. This leaves me with the unpleasant duty of coming up with some method of providing an interface on MyClock that allows users of the class to control when the timer is started and stopped. Besides adding unneeded complexity, this is annoying because having one owner of an instance of the class invalidate the timer could step on the toes of another owner who is counting on it to keep running. I could implement my own pseudo-retain-count-system for keeping the timer running but, ...seriously? This is way to much work for such a simple concept. Any solution I can think of feels hacky. I ended up writing a wrapper for NSTimer that behaves exactly like a normal NSTimer, but doesn't retain its target. I don't like it, and I would appreciate any insight.

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• CSS Background image arbitrarily not getting requested at all

  - by Pekka

  I`m in the process of building a template for Redmine (a project management system based on Ruby on Rails.) Ruby is running on a virtual server from a Bitnami.org installation package. The OS is Windows. The template essentially consists of a styles.css file. In that file, I have the following line: #header { padding: 0px; padding-top: 48px; background-color: #62DFFF; background-image: url(../images/bkg.jpg); background-position: center bottom; background-repeat: repeat-x; height:150px; } It's a header element with a background image. The problem: This background image arbitrarily appears and disappears when reloading the page. It is more often missing than it is not. Say you reload the page in your browser ten times in twenty seconds; the image will appear in two instances, and be missing in the 18 others. I would have put this down to server problems, but the weird thing is that when it's missing, the request for the image doesn't appear in Firebug's net tab at all. Even if it were cached, the request should be there, shouldn't it? Raw screenshots of the identical page on two reloads: I am 100% sure the CSS file does not change in between. I have examined both instances with Firebug and the CSS is identical. When I change the image's URL by editing the style declaration in firebug to bkg.jpg?xyz=123445 then the image will get loaded, which is making me think this must be a server problem. It happens in both Firefox and Chrome so it must be something basic I'm overlooking. What could be causing a browser not to load a resource at all? I have zero idea about Ruby nor Rails - getting Redmine running and customized is all I have ever had to do with this platform - so I don't really know where to start debugging. Apache's, Mongrel's and Redmine's error logs look fine, though. And then again, this looks like a browser issue. I'm stumped.

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• Update tile notifcation with XML returned by web service

  - by tempid

  I have a Metro app in C# & XAML. The tile is updated periodically and I've used WebAPI to serve the tile notification XML. So far so good. I was then told that I cannot use WebAPI as the server that I was planning to host it on does not have .NET 4.5. No plans to install it anytime soon either. I had to change the WebAPI to a plain old Web service (.NET 3.5) which does the same thing - return tile notification XML. I've enabled HTTP-GET (I know, security concern) and was able to invoke the webservice like this - http://server/TileNotifications.asmx/[email protected] But ever since I made the switch, the tiles are not being updated. I've checked Fiddler and made sure the app is hitting the webservice and the XML is being returned correctly. But the tiles are not updated. If I replace it with the WebAPI, the tiles are updated. Do I need to do anything special with the web services? like decorating the web method with a custom attribute? Here's my web service code - [WebMethod] public XmlDocument GetTileData(string user) { // snip var xml = new XmlDocument(); xml.LoadXml(string.Format(@"<tile> <visual> <binding template='TileWideSmallImageAndText02'> <image id='1' src='http://server/images/{0}_wide.png'/> <text id='1'>Custom Field : {1}/text> <text id='2'>Custom Field : {2}</text> <text id='3'>Custom Field : {3}</text> </binding> <binding template='TileSquarePeekImageAndText01'> <image id='1' src='http://server/images/{0}_square.png'/> <text id='1'>Custom Field</text> <text id='2'>{1}</text> </binding> </visual> </tile>", value1, value2, value3, value4)); return xml; }

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• How to integrate Purify into Hudson CI?

  - by Martin

  Hello everybody! I have a Hudson CI system set up and for the moment it is used for building a project and running some unit tests. My next step is to integrate the memory leak detector Purify into the build cycle. Now I want to start the unit tests also inside purify and for this I have created a new batch task which runs following command: purify.exe /SaveTextData MyExecutable.exe --test TestLibrary.dll --output xml As I read in the Purify documentation the /SaveTextData option is used in order to run purify not in GUI mode. If I run this command on my local workstation in the command line it works perfectly. But in case it is started by Hudson, nothing happens. Unfortunetly there are no logs of purify... Has someone ever tried to start purify either by Hudson or any other CI system? Thanks in advance. Best regards Martin EDIT: I forgot to tell you, that I have Hudson running as master and slave on different computers. On the master I have configured a task which should start the unit tests within purify on the slave. I am running the slave via JNLP. EDIT 18.03.2010: Ok, so finally I am a bit closer the source of the problem. I have discovered, that running my unit tests in purify locally the log file EngineCmdLine.log contains three commands. I am starting purify with following command: purify.exe /SaveTextData TestRunnerConsoleWD.exe --test TestDemoWD.dll Output of EngineCmdLine.log when starting purify manually: File: D:\workspace\hudson\workspace\Purify_TestFW_CommonsCoreTest_Cpp_msvs9\TestRunnerConsoleWD.exe File: C:\WINDOWS\system32\ws2_32.dll File: D:\workspace\hudson\workspace\Purify_TestFW_CommonsCoreTest_Cpp_msvs9\TestDemoWD.dll Output when starting via Hudson: File: D:\workspace\hudson\workspace\Purify_TestFW_CommonsCoreTest_Cpp_msvs9\TestRunnerConsoleWD.exe File: C:\WINDOWS\system32\ws2_32.dll File: D:\workspace\hudson\workspace\Purify_TestFW_CommonsCoreTest_Cpp_msvs9\TestDemoWD.dll File: D:\workspace\hudson\workspace\Purify_TestFW_CommonsCoreTest_Cpp_msvs9\TestDemoWD.dll The error output of purify: Instrumenting: BtcTestDemoWD.dll 313856 bytes Purify: While processing file D:\workspace\hudson\workspace\Purify_TestFW_CommonsCoreTest_Cpp_msvs9\TESTFWWD.DLL: Error: Cannot replace file c:\Programme\IBM\RationalPurifyPlus\PurifyPlus\cache\BTCTESTFWWD$Purify_D_workspace_hudson_workspace_Purify_TestFW_CommonsCoreTest_Cpp_msvs9.DLL. Is it in use? TESTFWWD.DLL 505344 bytes Unable to instrument D:\workspace\hudson\workspace\Purify_TestFW_CommonsCoreTest_Cpp_msvs9\TestDemoWD.dll (0x1) Question is, why is purify starting twice a command with the TestDemoWD.dll library?

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• Is it normal for a programmer with 2 years experience to take a long time to code simple programs?

  - by ajax81

  Hi all, I'm a relatively new programmer (18 months on the scene), and I'm finally getting to the point where I'm comfortable accepting projects and developing solutions under minimal supervision. Unfortunately, this also means that I've become acutely aware of my performance shortfalls, the most prevalent of which is the amount of time it takes me to develop, test, and submit algorithms for review. A great example of what I'm talking about occurred this week when I was tasked with developing a simple XML web service (asp.net 3.5) callable via client-side JavaScript, that accepts a single parameter and returns a dataset output to a modal window (please note this is the first time I've had to develop a web service and have had ZERO experience creating/consuming them...let alone calling them from JS client side). Keeping a long story short -- I worked on it for 4 days straight, all day each day, for a grand total of 36 hours, not including the time I spent dwelling on the problem in the shower, the morning commute, and laying awake in bed at night. I learned a great deal about web services and xml/json/javascript...but was called in for a management review to discuss the length of time it took me to develop the solution. In the meeting, I was praised for the quality of my work and was in fact told that my effort was commendable. However, they (senior leads and pm's) weren't impressed with the amount of time it took me to develop the solution and expressed that they would have liked to see the solution in roughly 1/3 of the time it took me. I guess what concerns me the most is that I've identified this pattern as common for myself. Between online videos, book research, and trial/error coding...if its something I haven't seen before, I can spend up to two weeks on a problem that seems to only take the pros in the videos moments to code up. And of course, knowing that management isn't happy with this pattern has shaken me up a bit. To sum up, I have some very specific questions I'd like to ask, and would greatly appreciate your objective professional feedback. Is my experience as a junior programmer common among new developers? Or is it possible that I'm just not cut out for the work? If you suspect that my experience is not common and that there may be an aptitude issue, do you have any suggestions/solutions that I could propose to management to help bring me up to speed? Do seasoned, professional programmers ever encounter knowledge barriers that considerably delay deliverables? When you started out in the industry, did you know how to "do it all"? If not, how long did it take you to be perceived as "proficient"? Was it a natural progression of trial and error, or was there a particular zen moment when you knew you had achieved super saiyen power level? Anyways, thanks for taking the time to read my question(s). I don't know if this is the right place to ask for professional career guidance, but I greatly appreciate your willingness to help me out. Cheers, Daniel

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• Am I Leaking ADO.NET Connections?

  - by HardCode

  Here is an example of my code in a DAL. All calls to the database's Stored Procedures are structured this way, and there is no in-line SQL. Friend Shared Function Save(ByVal s As MyClass) As Boolean Dim cn As SqlClient.SqlConnection = Dal.Connections.MyAppConnection Dim cmd As New SqlClient.SqlCommand Try cmd.Connection = cn cmd.CommandType = CommandType.StoredProcedure cmd.CommandText = "proc_save_my_class" cmd.Parameters.AddWithValue("@param1", s.Foo) cmd.Parameters.AddWithValue("@param2", s.Bar) Return True Finally Dal.Utility.CleanupAdoObjects(cmd, cn) End Try End Function Here is the Connection factory (if I am using the correct term): Friend Shared Function MyAppConnection() As SqlClient.SqlConnection Dim cn As New SqlClient.SqlConnection(ConfigurationManager.ConnectionStrings("MyConnectionString").ToString) cn.Open() If cn.State <> ConnectionState.Open Then ' CriticalException is a custom object inheriting from Exception. Throw New CriticalException("Could not connect to the database.") Else Return cn End If End Function Here is the Dal.Utility.CleaupAdoObjects() function: Friend Shared Sub CleanupAdoObjects(ByVal cmd As SqlCommand, ByVal cn As SqlConnection) If cmd IsNot Nothing Then cmd.Dispose() If cn IsNot Nothing AndAlso cn.State <> ConnectionState.Closed Then cn.Close() End Sub I am getting a lot of "Timeout expired. The timeout period elapsed prior to completion of the operation or the server is not responding." error messages reported by the users. The application's DAL opens a connection, reads or saves data, and closes it. No connections are ever left open - intentionally! There is nothing obvious on the Windows 2000 Server hosting the SQL Server 2000 that would indicate a problem. Nothing in the Event Logs and nothing in the SQL Server logs. The timeouts happen randomly - I cannot reproduce. It happens early in the day with only 1 to 5 users in the system. It also happens with around 50 users in the system. The most connections to SQL Server via Performance Monitor, for all databases, has been about 74. The timeouts happen in code that both saves to, and reads from, the database in different parts of the application. The stack trace does not point to one or two offending DAL functions. It's happened in many different places. Does my ADO.NET code appear to be able to leak connections? I've goolged around a bit, and I've read that if the connection pool fills up, this can happen. However, I'm not explicitly setting any connection pooling. I've even tried to increase the Connection Timeout in the connection string, but timeouts happen long before the 300 second (5 minute) value: <add name="MyConnectionString" connectionString="Data Source=MyServer;Initial Catalog=MyDatabase;Integrated Security=SSPI;Connection Timeout=300;"/> I'm at a total loss already as to what is causing these Timeout issues. Any ideas are appreciated.

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• How to fine tune a Membership Provider?

  - by Venemo

  After all the answers to my last question about fine-tuning turned out to be more useful than I expected, I thought that I would ask another similar Question about the MembershipProviders as well. Okay, so firstly, to clarify: I know what a Membership, Role, and Profile provider is, how to implement my own, and how to configure them, and most of the things about them. Implementing a role and profile provider is pretty straightforward, because they only require simple CRUD most of the time. (A single line of LINQ is enough for about half of the RoleProvider's methods.) However, the Membership provider is a differend beast. Many of you may realize that it violates the SR (Single Responsibility) principle, because it has to do EVERYTHING related to user management. While this leaves a lot of room for customizations, it has its downsides as well. There is no information on the Internet about what their EXACT expected behaviour is, such as when should they throw exceptions or simply return null, and stuff like that. I use this sample implementation for reference, but it also contains several contradictions. For example, it uses its own ValidateUser method for checking for credentials in the ChangePassword method. But the ValidateUser also updates the user's LastLoginDate to the current date. So, does the framework expect that I set it in my own provider as well, or is it simply a mistake in the sample? The other is: the ChangePassword method throws an exception every time when validating the new password, but CreateUser doesn't ever throw an exception, it simply returns false. And last, but not least: it counts the invalid password attempts of the user and locks them if it passes a threshold. While this is good, but it requires manual action to unlock the users. Is it a problem if my provider automatically unlocks the user after a certain amount of time? (EDIT) I almost forgot: the CreateUser method in the sample inserts the ID from the method parameter. I actually think this is bad practice, because I use inters with auto incement as IDs, so inserting them from some method parameter is not an option. Should I just ignore the parameter, or require that its value is null and throw an exception if it isn't? All in all, does ASP.NET have any assumptions about the behaviour of a MembershipProvider? Is there any documentation which describes when should I throw an exception or just return null? I also tried to find a set of generic unit tests which would provide some guidance about the expected behaviour, but no luck, I found plenty of articles about "Unit testing is good", and "How to unit test a MembershipProvider", but not one where there would be any actual tests. Thanks in advance for everyone!

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• XSL unique values per node

  - by Nathan

  ok i have this xml <roots> <root> <name>first</name> <item type='test'><something>A</something></item> <item type='test'><something>B</something></item> <item type='test'><something>C</something></item> <item type='test'><something>A</something></item> <item type='other'><something>A</something></item> <item type='test'><something>B</something></item> <item type='other'><something>D</something></item> </root> <root> <name>second</name> <item type='test'><something>E</something></item> <item type='test'><something>B</something></item> <item type='test'><something>F</something></item> <item type='test'><something>A</something></item> <item type='other'><something>A</something></item> <item type='test'><something>B</something></item> <item type='other'><something>D</something></item> </root> </roots> now i need to get the unique values of each root node so far i have <?xml version="1.0" encoding="ISO-8859-1"?> <xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform"> <xsl:output indent="yes" method="text"/> <xsl:key name="item-by-value" match="something" use="."/> <xsl:key name="rootkey" match="root" use="name"/> <xsl:template match="/"> <xsl:for-each select="key('rootkey','second')"> <xsl:for-each select="item/something"> <xsl:if test="generate-id() = generate-id(key('item-by-value', normalize-space(.)))"> <xsl:value-of select="."/> </xsl:if> </xsl:for-each> </xsl:for-each> </xsl:template> </xsl:stylesheet> if i use "First" as the key to get only the first root i get a good result ABCD how ever if i use "second" i only get EF but i need the result to be ABDFE

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• Is O_NONBLOCK being set a property of the file descriptor or underlying file?

  - by Daniel Trebbien

  From what I have been reading on The Open Group website on fcntl, open, read, and write, I get the impression that whether O_NONBLOCK is set on a file descriptor, and hence whether non-blocking I/O is used with the descriptor, should be a property of that file descriptor rather than the underlying file. Being a property of the file descriptor means, for example, that if I duplicate a file descriptor or open another descriptor to the same file, then I can use blocking I/O with one and non-blocking I/O with the other. Experimenting with a FIFO, however, it appears that it is not possible to have a blocking I/O descriptor and non-blocking I/O descriptor to the FIFO simultaneously (so whether O_NONBLOCK is set is a property of the underlying file [the FIFO]): #include <errno.h> #include <fcntl.h> #include <stdio.h> #include <stdlib.h> #include <unistd.h> int main(int argc, char **argv) { int fds[2]; if (pipe(fds) == -1) { fprintf(stderr, "`pipe` failed.\n"); return EXIT_FAILURE; } int fd0_dup = dup(fds[0]); if (fd0_dup <= STDERR_FILENO) { fprintf(stderr, "Failed to duplicate the read end\n"); return EXIT_FAILURE; } if (fds[0] == fd0_dup) { fprintf(stderr, "`fds[0]` should not equal `fd0_dup`.\n"); return EXIT_FAILURE; } if ((fcntl(fds[0], F_GETFL) & O_NONBLOCK)) { fprintf(stderr, "`fds[0]` should not have `O_NONBLOCK` set.\n"); return EXIT_FAILURE; } if (fcntl(fd0_dup, F_SETFL, fcntl(fd0_dup, F_GETFL) | O_NONBLOCK) == -1) { fprintf(stderr, "Failed to set `O_NONBLOCK` on `fd0_dup`\n"); return EXIT_FAILURE; } if ((fcntl(fds[0], F_GETFL) & O_NONBLOCK)) { fprintf(stderr, "`fds[0]` should still have `O_NONBLOCK` unset.\n"); return EXIT_FAILURE; // RETURNS HERE } char buf[1]; if (read(fd0_dup, buf, 1) != -1) { fprintf(stderr, "Expected `read` on `fd0_dup` to fail immediately\n"); return EXIT_FAILURE; } else if (errno != EAGAIN) { fprintf(stderr, "Expected `errno` to be `EAGAIN`\n"); return EXIT_FAILURE; } return EXIT_SUCCESS; } This leaves me thinking: is it ever possible to have a non-blocking I/O descriptor and blocking I/O descriptor to the same file and if so, does it depend on the type of file (regular file, FIFO, block special file, character special file, socket, etc.)?

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• How can I inject Javascript (including Prototype.js) in other sites without cluttering the global na

  - by Daniel Magliola

  I'm currently on a project that is a big site that uses the Prototype library, and there is already a humongous amount of Javascript code. We're now working on a piece of code that will get "injected" into other people's sites (picture people adding a <script> tag in their sites) which will then run our code and add a bunch of DOM elements and functionality to their site. This will have new pieces of code, and will also reuse a lot of the code that we use on our main site. The problem I have is that it's of course not cool to just add a <script> that will include Prototype in people's pages. If we do that in a page that's already using ANY framework, we're guaranteed to screw everything up. jQuery gives us the option to "rename" the $ object, so it could handle this situation decently, except obviously for the fact that we're not using jQuery, so we'd have to migrate everything. Right now i'm contemplating a number of ugly choices, and I'm not sure what's best... Rewrite everything to use jQuery, with a renamed $ object everywhere. Creating a "new" Prototype library with only the subset we'd be using in "injected" code, and renaming $ to something else. Then again I'd have to adapt the parts of my code that would be shared somehow. Not using a library at all in injected code, to keep it as clean as possible, and rewriting the shared code to use no library at all. This would obviously degenerate into us creating our own frankenstein of a library, which is probably the worst case scenario ever. I'm wondering what you guys think I could do, and also whether there's some magic option that would solve all my problems... For example, do you think I could use something like Caja / Cajita to sandbox my own code and isolate it from the rest of the site, and have Prototype inside of there? Or am I completely missing the point with that? I also read once about a technique for bookmarklets, were you add your code like this: (function() { /* your code */ })(); And then your code is all inside your anonymous function and you haven't touched the global namespace at all. Do you think I could make one file containing: (function() { /* Full Code of the Prototype file here */ /* All my code that will run in the "other" site */ InitializeStuff_CreateDOMElements_AttachEventHandlers(); })(); Would that work? Would it accomplish the objective of not cluttering the global namespace, and not killing the functionality on a site that uses jQuery, for example? Or is Prototype too complex somehow to isolate it like that? (NOTE: I think I know that that would create closures everywhere and that's slower, but I don't care too much about performance, my code is not doing anything that complex)

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• One entityManger finds entity , the other does not.

  - by Pitelk

  Hi all, I have a very strange behavior in my program. I have 2 classes (class LogIn and CreateGame) where i have injected an EntityManager in each using the annotation @PersistenceContext(unitName="myUnitPU") EntityManager entitymanger; In some point i remove an object called "user" from the database using entitymanger.remove(user) from a method in LogIn class. The business logic is that a user can host and join games ( in the same time) so removing the user all the entries in database about the games the user has created are removed and all the entries showing in which games the user has joined are removed also. After that, i call another function which checks if the user exists using a method in the LogIn class entitymanager.find(user) which surprisingly enough, finds the user. After that I call a method in CreateGame class which tries to find the user by using again entitymanger.find(user) the entitymanger in that class fails to find the user (which is the expected result as the user is removed and it's not in the database) So the question is : Why the entitymanager in one class finds the user (which is wrong) where the other doesn't find it? Does anyone has ever the same problem? PS : This "bug" occurs when the user has hosted a game which is joined by another user (lets call him Buser) and the Buser has made a game which is joined by the current user. GAME | HOST | CLIENTS game1 | user | userB game2 | userB | user where in this case by removing the user, the game1 is deleted and the user is removed from game2 so the result is GAME | HOST | CLIENTS game2 | userB | PS2 : The Beans are EJB3.0. The methods are called from a delegate class. The beans in the delegate class are instantiated using the InitialContext.lookup() method. Note that for logging in ,creating , joining games the appropriate delegate class calls the correspondent EJB which does the transactions. In the case of logOut, the delegate calls an EJB to logout the user but becuase other stuff must be done (as said above) this EJB calls other EJB (again using lookup() ) which has methods like removegame(), removeUserFromGame() etc. After those methods are executed the user is then logged out. Maybe it has something to do with the fact the the first entity manager is called by a delegate but the second from inside an EJb and thats why the one entitymanger can see the non-existent user while the other cannot? Also all the methods have TRANSACTIONTYPE.REQUIRED Thank you in advance

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