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• Comet, responseText and memory usage

  - by ithcy

  Is there a way to clear out the responseText of an XHR object without destroying the XHR object? I need to keep a persistent connection open to a web server to feed live data to a browser. The problem is, there is a relatively large amount of data coming through (several hundred K per second constantly), so memory usage is a big problem, because this connection must remain open for at least several minutes. responseText gets very big very quickly, even though the JSON I send back has been crunched as small as it can get. Due to the way the server-side app works, if I use AJAX-style short polling and just destroy the XHR object when I'm done with it, I miss significant amounts of important data even in the few milliseconds it takes to parse the response, create a new XHR and send it out. I do not have the option to use overlapping requests, as the web server only accepts one connection at a time. (Don't ask.) So Comet is exactly the model I need. What I would like to do is parse each JSON chunk as it comes back from the server, and then clear out responseText so that I can keep using the same connection. However, responseText is read-only. It cannot be directly emptied by any method I have found. Is there a part of the picture I am missing here? Does anyone know any tricks I can use to free up responseText when I'm done reading it? Or is there another place the server responses can go? I am not including code because this is really almost a code-agnostic question. The Javascript routines that spawn the XHRs and handle the returned data are very, very simple.

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• How does CDI injection work in MDBs and @Scheduled beans?

  - by Nils-Petter Nilsen

  I'm working on a large Java EE 6 application that is deployed on JBoss 6 Final. My current tasks involve using @Inject consistently instead of @EJB, but I'm running into some problems on some types of beans, specifically @MessageDriven beans and beans with @Scheduled methods. What happens is that if I'm unlucky with the timing (for @Schedule) or if there are messages in the MDBs' queues at startup, instantiation of the beans will fail because the injected resources (which are EJBs themselves) are not bound yet. Because I use @Inject, I'm guessing that the EJB container considers my beans to be ready, since the container itself does not care about @Inject; it probably simply assumes that since there are no @EJB injections, the beans are ready for use. The injected CDI proxies will then fail because the resources to inject aren't actually bound yet. Tiny example: @Stateless @LocalBean public class MySupportingBean { public void doSomething() { ... } } @Singleton public class MyScheduledBean { @Inject private MySupportingBean supportingBean; @Schedule(second = "*/1", hour = "*", minute = "*", persistent = false) public void onTimeout() { supportingBean.doSomething(); } } The above example will probably not fail often because there are only two beans, but the project I'm working on binds lots of EJBs, which will amplify the problem. But it might fail because there is no guarantee that MySupportingBean is bound first, and if onTimeout is invoked before MySupportingBean is bound, then instantiation of MyScheduledBean will fail. If I used @EJB instead, MyScheduledBean wouldn't be bound until the dependency to MySupportingBean was satisfied. Note that the example will not fail in onTimeout itself, but when CDI attempts to inject MySupportingBean. I've read a lot of posts on different forums where many people argue that @Inject is always better. Generally, I agree, but how do they handle @Schedule or @MessageDriven combined with @Inject? In my experience, it comes down to dumb luck whether the beans will work or not in those cases, and the beans will fail arbitrarily, depending on which order the EJBs are deployed in, and when @Schedule or onMessage are invoked.

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• ASP.NET Webforms site using HTTPCookie with 100 year timeout times out after 20 minutes

  - by Rob

  I have a site that is using Forms Auth. The client does not want the site session to expire at all for users. In the login page codebehind, the following code is used: // user passed validation FormsAuthentication.Initialize(); // grab the user's roles out of the database String strRole = AssignRoles(UserName.Text); // creates forms auth ticket with expiration date of 100 years from now and make it persistent FormsAuthenticationTicket fat = new FormsAuthenticationTicket(1, UserName.Text, DateTime.Now, DateTime.Now.AddYears(100), true, strRole, FormsAuthentication.FormsCookiePath); // create a cookie and throw the ticket in there, set expiration date to 100 years from now HttpCookie cookie = new HttpCookie(FormsAuthentication.FormsCookieName, FormsAuthentication.Encrypt(fat)) { Expires = DateTime.Now.AddYears(100) }; // add the cookie to the response queue Response.Cookies.Add(cookie); Response.Redirect(FormsAuthentication.GetRedirectUrl(UserName.Text, false)); The web.config file auth section looks like this: <authentication mode="Forms"> <forms name="APLOnlineCompliance" loginUrl="~/Login.aspx" defaultUrl="~/Course/CourseViewer.aspx" /> </authentication> When I log into the site I do see the cookie correctly being sent to the browser and passed back up: However, when I walk away for 20 minutes or so, come back and try to do anything on the site, the login window reappears. This solution was working for a while on our servers - now it's back. The problem doesn't occur on my local dev box running Cassini in VS2008. Any ideas on how to fix this?

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• Apache module, is it possible to have asynchronous processing

  - by prashant2361

  Hi, I have a requirement where I need to send continous updates to my clients. Client is browser in this case. We have some data which updates every sec, so once client connects to our server, we maintain a persistent connection and keep pushing data to the client. I am looking for suggestions of this implementation at the server end. Basically what I need is this: 1. client connects to server. I maintain the socket and metadata about the socket. metadata contains what updates need to be send to this client 2. server process now waits for new client connections 3. One other process will have the list of all the sockets opened and will go through each of them and send the updates if required. Can we do something like this in apache module: 1. apache process gets the new connection. It maintains the state for the connection. It keeps the state in some global memory and returns back to root process to signify that it is done so that it can accept the new connection 2. the apache process though has returned the status to root process but it is also executing parallely where it going through its global store and sending updates to the client, if any. So can a apache process do these things: 1. Have more than one connection associated with it 2. Asynchronously waiting for new connection and at the same time processing the previous connections? Regards Prashant

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• Apache Tuscany 1.6 How do you set the JMS Binding Delivery Mode to NON_PERSISTENT?

  - by Robert Greiner

  I am using Tuscany 1.6 and am trying to set the Delivery Mode JMS Binding to NON_PERSISTENT. I've tried using uri="jms:MyService?deliveryMode=1" (which is what the spec (PDF) says to do) but, I ended up getting the following exception: Unknown token deliveryMode=1 I also tried <headers JMSDeliveryMode="NON_PERSISTENT"/>, although I did not get an exception the messages still got delivered as PERSISTENT. This is the format for the URI jms:<jms-dest>? connectionFactoryName=<Connection-Factory-Name> & destinationType={queue|topic} deliveryMode=<Delivery-Mode> & timeToLive=<Time-To-Live> & priority=<Priority> & <User-Property>=<User-Property-Value> & … This is the example I am using <composite xmlns="http://www.osoa.org/xmlns/sca/1.0" name="MyValueComposite"> <service name="MyValueService"> <interface.java interface="services.myvalue.MyValueService"/> <binding.jms uri="jms:MyValueServiceQueue?activationSpecName=MyValueServiceAS&... "/> </service> <reference name="StockQuoteService"> <interface.java interface="services.stockquote.StockQuoteService"/> <binding.jms uri="jms:StockQuoteServiceQueue?connectionFactoryName=StockQuoteServiceQCF&deliveryMode=1&... "/> </reference> </composite>

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• AJAX Autosave

  - by antony.trupe

  What's the best javascript library, or plugin or extension to a library, that has implemented autosaving functionality? The specific need is to be able to 'save' a data grid. Think gmail and Google Documents' autosave. I don't want to reinvent the wheel if its already been invented. I'm looking for an existing implementation of the magical autoSave() function. Auto-Saving:pushing to server code that saves to persistent storage, usually a DB. The server code framework is outside the scope of this question. Note that I'm not looking for an Ajax library, but a library/framework a level higher: interacts with the form itself. daemach introduced an implementation on top of jQuery @ http://ideamill.synaptrixgroup.com/?p=3. I'm not convinced it meets the lightweight and well engineered criteria though. Criteria stable, lightweight, well engineered saves onChange and/or onBlur saves no more frequently then a given number of milliseconds handles multiple updates happening at the same time doesn't save if no change has occurred since last save saves to different urls per input class Updates I've stabilized a solution. See my answer below for links.

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• Python: Catching / blocking SIGINT during system call

  - by danben

  I've written a web crawler that I'd like to be able to stop via the keyboard. I don't want the program to die when I interrupt it; it needs to flush its data to disk first. I also don't want to catch KeyboardInterruptedException, because the persistent data could be in an inconsistent state. My current solution is to define a signal handler that catches SIGINT and sets a flag; each iteration of the main loop checks this flag before processing the next url. However, I've found that if the system happens to be executing socket.recv() when I send the interrupt, I get this: ^C Interrupted; stopping... // indicates my interrupt handler ran Traceback (most recent call last): File "crawler_test.py", line 154, in <module> main() ... File "/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/socket.py", line 397, in readline data = recv(1) socket.error: [Errno 4] Interrupted system call and the process exits completely. Why does this happen? Is there a way I can prevent the interrupt from affecting the system call?

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• What's a good Java-based Master-Slave communication mechanism?

  - by plecong

  I'm creating a Java application that requires master-slave communication between JVMs, possibly residing on the same physical machine. There will be a "master" server running inside a JEE application server (i.e. JBoss) that will have "slave" clients connect to it and dynamically register itself for communication (that is the master will not know the IP addresses/ports of the slaves so cannot be configured in advance). The master server acts as a controller that will dole work out to the slaves and the slaves will periodically respond with notifications, so there would be bi-directional communication. I was originally thinking of RPC-based systems where each side would be a server, but it could get complicated, so I'd prefer a mechanism where there's an open socket and they talk back and forth. I'm looking for a communication mechanism that would be low-latency where the messages would be mostly primitive types, so no serious serialization is necessary. Here's what I've looked at: RMI JMS: Built-in to Java, the "slave" clients would connect to the existing ConnectionFactory in the application server. JAX-WS/RS: Both master and slave would be servers exposing an RPC interface for bi-directional communication. JGroups/Hazelcast: Use shared distributed data structures to facilitate communication. Memcached/MongoDB: Use these as "queues" to facilitate communication, though the clients would have to poll so there would be some latency. Thrift: This does seem to keep a persistent connection, but not sure how to integrate/embed a Thrift server into JBoss WebSocket/Raw Socket: This would work, but require a lot more custom code than I'd like. Is there any technology I'm missing? Edit: Also looked at: JMX: Have the client connect to JBoss' JMX server and receive JMX notifications for bidirectional comms.

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• Catching / blocking SIGINT during system call

  - by danben

  I've written a web crawler that I'd like to be able to stop via the keyboard. I don't want the program to die when I interrupt it; it needs to flush its data to disk first. I also don't want to catch KeyboardInterruptedException, because the persistent data could be in an inconsistent state. My current solution is to define a signal handler that catches SIGINT and sets a flag; each iteration of the main loop checks this flag before processing the next url. However, I've found that if the system happens to be executing socket.recv() when I send the interrupt, I get this: ^C Interrupted; stopping... // indicates my interrupt handler ran Traceback (most recent call last): File "crawler_test.py", line 154, in <module> main() ... File "/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/socket.py", line 397, in readline data = recv(1) socket.error: [Errno 4] Interrupted system call and the process exits completely. Why does this happen? Is there a way I can prevent the interrupt from affecting the system call?

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• handle large Parcelable ArrayList in Android

  - by Gal Ben-Haim

  I'm developing an Android app that is a client to a JSON webservice API. I have classes of resource objects (some are nested) and I pass results from an IntentService that access the webserive using the Parcelable interface for all the resource classes. the webservice returns arrays or results that can be potentially large (because of the nesting, for example, a post object also contains comments array, each comment also contains a user object). currently I'm either inserting the results into a SQlite database or displaying them in a ListView. (my relevant methods are accepting ArrayList<resourceClass> as arguments). (some data need to be persistent stored and some should not). since I don't know what size of lists I can handle this way without reaching the memory limits, is this a good practice ? is it a better idea to save the parsed JSON to a local file immediately and pass the file path to the ResultReceiver, then either insert to database from that file or display the data ? is there a better way to handle this ? btw - I'm parsing the JSON as a stream with Gson's Reader so there shouldn't be memory issues at that stage.

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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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• Sparse (Pseudo) Infinite Grid Data Structure for Web Game

  - by Ming

  I'm considering trying to make a game that takes place on an essentially infinite grid. The grid is very sparse. Certain small regions of relatively high density. Relatively few isolated nonempty cells. The amount of the grid in use is too large to implement naively but probably smallish by "big data" standards (I'm not trying to map the Internet or anything like that) This needs to be easy to persist. Here are the operations I may want to perform (reasonably efficiently) on this grid: Ask for some small rectangular region of cells and all their contents (a player's current neighborhood) Set individual cells or blit small regions (the player is making a move) Ask for the rough shape or outline/silhouette of some larger rectangular regions (a world map or region preview) Find some regions with approximately a given density (player spawning location) Approximate shortest path through gaps of at most some small constant empty spaces per hop (it's OK to be a bad approximation often, but not OK to keep heading the wrong direction searching) Approximate convex hull for a region Here's the catch: I want to do this in a web app. That is, I would prefer to use existing data storage (perhaps in the form of a relational database) and relatively little external dependency (preferably avoiding the need for a persistent process). Guys, what advice can you give me on actually implementing this? How would you do this if the web-app restrictions weren't in place? How would you modify that if they were? Thanks a lot, everyone!

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• LinqToSQL not updating database

  - by codegarten

  Hi. I created a database and dbml in visual studio 2010 using its wizards. Everything was working fine until i checked the tables data (also in visual studio server explorer) and none of my updates were there. using (var context = new CenasDataContext()) { context.Log = Console.Out; context.Cenas.InsertOnSubmit(new Cena() { id = 1}); context.SubmitChanges(); } This is the code i am using to update my database. At this point my database has one table with one field (PK) named ID. *INSERT INTO [dbo].Cenas VALUES (@p0) -- @p0: Input Int (Size = -1; Prec = 0; Scale = 0) [1] -- Context: SqlProvider(Sql2008) Model: AttributedMetaModel Build: 4.0.30319.1* This is LOG from the execution (printed the context log into the console). The problem i'm having is that these updates are not persistent in the database. I mean that when i query my database (visual studio server explorer - new query) i see the table is empty, every time. I am using a SQL Server database file (.mdf).

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• Help with accessing a pre-existing window AFTER opener is refreshed!

  - by Wilhelm Murdoch

  Alright, I'm at my wit's end on this issue. First, backstory. I'm working on a video management system where we're allowing users, when adding new content, to upload and, optionally, transcode a media file. We're using Java applet for the browser-based FTP client. What I want to do is allow a user to initiate an upload and then send the FTP connection instance to a popup window. This window will act as a job queue for the FTP transfer process. This will allow users to move about the main interface without having to stay on the original page until an individual file transfer is complete. For the most part I have all of this working, but here's a problem. If the window is closed, all connections are dropped and the upload process for all queued files will be canceled. So, if Window One opens the Popup Window, adds stuff to the queue, refreshes the screen or moves to a different page, how will I access the Popup Window? The popup window and its contents must remain persistent while the user navigates through the original window. The original window must be able to access the popup to add a new job to the queue. The popup window itself is independent of the opening window, so communication only happens in one direction: Parent - Popup Not Parent <- Popup Window.open(null, 'WINDOW_NAME'); will not work in this case. I need to check if a window exists BEFORE using window.open. Help!?!?

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• Module not found

  - by TMP

  Hi There! I've been working on this one quite a bit and haven't gotten any closer to a solution. I juut dug up my old copy of the WindowsHookLib again - It's available with source at http://www.codeproject.com/KB/DLL/WindowsHookLib.aspx. This library allows Global Windows Mouse/Keyboard/Clipboard Hooks, which is very useful. I'm trying to use the Mouse Hook in here to Capture Mouse-Motion (I could use a Timer that always polls Cursor.Position, but I plan on using more features of WindowsHookLib later). Code as follows: MouseHook mh = new MouseHook(); mh.InstallHook(); mh.MouseMove += new EventHandler<WindowsHookLib.MouseEventArgs>(mh_MouseMove); But on the call to InstallHook(), I get an Exception: "The specified Module could not be found". Strange. Searching, I found that someone thought this occurs because a DLL is not in a place included in the Windows PATH variable, and because placing it in system32 didn't help I went the whole hog and translated the thing to C# for inclusion directly in my project (I was curious how it works). However the error was obstinately persistent, so I dug a bit on this, and found the Code in the Library that is responsible: In InstallHook(), we have IntPtr hinstDLL = Marshal.GetHINSTANCE(Assembly.GetExecutingAssembly().GetModules()[0]); this._hMouseHook = UnsafeNativeMethods.SetWindowsHookEx(14, this._mouseProc, hinstDLL, 0); if (this._hMouseHook == IntPtr.Zero) { throw new MouseHookException(new Win32Exception(Marshal.GetLastWin32Error()).Message); } And this (after modification and recompile) tells me that what I'm really getting is a Windows error "ERROR_MOD_NOT_FOUND"! Now, Here I'm stumped. Didn't I just compile the Hook Library directly into my project? (UnsafeMethods.SetWindowsHookEx is just a DllImported Method from user32) Any Answers, or Prods in the right direction, or any hints, pointers or similar are very much appreciated!

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• Can I use a keyPath in a predicate?

  - by dontWatchMyProfile

  For some reason, this didn't work (although the keypath does exist): NSPredicate *predicate = [NSPredicate predicateWithFormat:@"department.departmentName == %@", departmentName]; [fetchRequest setPredicate:predicate]; NSError *fetchError = nil; NSUInteger count = [moc countForFetchRequest:fetchRequest error:&fetchError]; // execution simply stops at this line, with no error or console log Execution just stops at the last line above when asking for the count. I don't get an console log. Also I don't get any kind of exception. The execution just stops. There are no objects in the persistent store yet. So maybe it crashes because of it tries to follow a keypath in a nonexisting object? Does that make sense? The line where GDB stops is this: 0x002a31cb <+0459> test %eax,%eax Previously to that, I see a lot of NSSQLAdapter... calls in the stack trace. There's definitely something wrong. Well, but when I set the Entity to the destination of the key path and then just do something like NSPredicate *predicate = [NSPredicate predicateWithFormat:@"departmentName == %@", departmentName]; then there is no problem and count simply is 0.

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• Sending buffered images between Java client and Twisted Python socket server

  - by PattimusPrime

  I have a server-side function that draws an image with the Python Imaging Library. The Java client requests an image, which is returned via socket and converted to a BufferedImage. I prefix the data with the size of the image to be sent, followed by a CR. I then read this number of bytes from the socket input stream and attempt to use ImageIO to convert to a BufferedImage. In abbreviated code for the client: public String writeAndReadSocket(String request) { // Write text to the socket BufferedWriter bufferedWriter = new BufferedWriter(new OutputStreamWriter(socket.getOutputStream())); bufferedWriter.write(request); bufferedWriter.flush(); // Read text from the socket BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(socket.getInputStream())); // Read the prefixed size int size = Integer.parseInt(bufferedReader.readLine()); // Get that many bytes from the stream char[] buf = new char[size]; bufferedReader.read(buf, 0, size); return new String(buf); } public BufferedImage stringToBufferedImage(String imageBytes) { return ImageIO.read(new ByteArrayInputStream(s.getBytes())); } and the server: # Twisted server code here # The analog of the following method is called with the proper client # request and the result is written to the socket. def worker_thread(): img = draw_function() buf = StringIO.StringIO() img.save(buf, format="PNG") img_string = buf.getvalue() return "%i\r%s" % (sys.getsizeof(img_string), img_string) This works for sending and receiving Strings, but image conversion (usually) fails. I'm trying to understand why the images are not being read properly. My best guess is that the client is not reading the proper number of bytes, but I honestly don't know why that would be the case. Side notes: I realize that the char[]-to-String-to-bytes-to-BufferedImage Java logic is roundabout, but reading the bytestream directly produces the same errors. I have a version of this working where the client socket isn't persistent, ie. the request is processed and the connection is dropped. That version works fine, as I don't need to care about the image size, but I want to learn why the proposed approach doesn't work.

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• Why two subprocesses created by Java behave differently?

  - by Lily

  I use Java Runtime.getRuntime().exec(command) to create a subprocess and print its pid as follows: public static void main(String[] args) { Process p2; try { p2 = Runtime.getRuntime().exec(cmd); Field f2 = p2.getClass().getDeclaredField("pid"); f2.setAccessible(true); System.out.println( f2.get( p2 ) ); } catch (Exception ie) { System.out.println("Yikes, you are not supposed to be here"); } } I tried both C++ executable and Java executable (.jar file). Both executables will continuously print out "Hello World" to stdout. When cmd is the C++ executable, the pid is printed out to console but the subprocess gets killed as soon as main() returns. However, when I call the .jar executable in cmd, the subprocess does not get killed, which is the desired behavior. I don't understand why same Java code, with different executables can behave so differently. How should I modify my code so that I could have persistent subprocesses in Java. Newbie in this field. Any suggestion is welcomed. Lily

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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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• jboss cache as hibernate 2nd level - cluster node doesn't persist replicated data

  - by Sergey Grashchenko

  I'm trying to build an architecture basically described in user guide http://www.jboss.org/file-access/default/members/jbosscache/freezone/docs/3.2.1.GA/userguide_en/html/cache_loaders.html#d0e3090 (Replicated caches with each cache having its own store.) but having jboss cache configured as hibernate second level cache. I've read manual for several days and played with the settings but could not achieve the result - the data in memory (jboss cache) gets replicated across the hosts, but it's not persisted in the datasource/database of the target (not original) cluster host. I had a hope that a node might become persistent at eviction, so I've got a cache listener and attached it to @NoveEvicted event. I found that though I could adjust eviction policy to fully control it, no any persistence takes place. Then I had a though that I could try to modify CacheLoader to set "passivate" to true, but I found that in my case (hibernate 2nd level cache) I don't have a way to access a loader. I wonder if replicated data persistence is possible at all by configuration tuning ? If not, will it work for me to create some manual peristence in CacheListener (I could check whether the eviction event is local, and if not - persist it to hibernate datasource somehow) ? I've used mvcc-entity configuration with the modification of cacheMode - set to REPL_ASYNC. I've also played with the eviction policy configuration. Last thing to mention is that I've tested entty persistence and replication in project that has been generated with Seam. I guess it's not important though.

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• Is it possible to have asynchronous processing

  - by prashant2361

  Hi, I have a requirement where I need to send continuous updates to my clients. Client is browser in this case. We have some data which updates every sec, so once client connects to our server, we maintain a persistent connection and keep pushing data to the client. I am looking for suggestions of this implementation at the server end. Basically what I need is this: 1. client connects to server. I maintain the socket and metadata about the socket. metadata contains what updates need to be send to this client 2. server process now waits for new client connections 3. One other process will have the list of all the sockets opened and will go through each of them and send the updates if required. Can we do something like this in Apache module: 1. Apache process gets the new connection. It maintains the state for the connection. It keeps the state in some global memory and returns back to root process to signify that it is done so that it can accept the new connection 2. the Apache process though has returned the status to root process but it is also executing in parallel where it going through its global store and sending updates to the client, if any. So can a Apache process do these things: 1. Have more than one connection associated with it 2. Asynchronously waiting for new connection and at the same time processing the previous connections? Regards Prashant

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• Intermittent Issue Writing to Google Appengine Datastore

  - by user242153

  Hi, I have a functioning app and recently have had intermittent problems writing to the datastore. I did not make any relevant code changes, however in the last few days my attempts to write to the datastore sometimes work and sometimes don't. I am trying to save an object that is in a many to one relationship with an existing persisted parent. So, the logic works like this: 1) Parent pulled from the datastore 2) Child created / instantiated using constructor 3) Parent.addSingleChild(child); // the "addSingleChild" method just adds the object argument to the collection of children 4) child.setParent(Parent); // sets the Parent object to the parent field I am using transactions as explained in the documentation ending with "finally {if (tx.isActive()) {tx.rollback(); } }" When the servlet is called, the parent is called from the datastore and the child object is created and added to the many to one mapping to the pre-existing parent. The child should automatically be persisted, since the parent is already persistent, and the child is added to the collection of children that map to the parent. And it worked this way in the past. However, to be sure, i did add a pm.makePersistent(child). Doesn't seem to help, still have the intermittent problem. Any suggestions would be appreciated, and if you need to see the actual code I can post. Thanks

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• Can I commit changes to actual database while debugging C# in Visual Studio?

  - by nathant23

  I am creating a C# application using Visual Studio that uses an SQLExpress database. When I hit f5 to debug the application and make changes to the database I believe what is happening is there is a copy of the database in the bin/debug folder that changes are being made to. However, when I stop the debugging and then hit f5 the next time a new copy of the database is being put in the bin/debug folder so that all the changes made the last time are gone. My question is: Is there a way that when I am debugging the application I can have it make changes to the actual database and those changes are actually saved or will it only make changes to the copy in the bin/debug folder (if that is what is actually happening)? I've seen similar questions, but I couldn't find an answer that said if it's possible to make those changes persistent in the actual .mdf file. The reason I ask is because as I build this application I am continuously adding pieces and testing to make sure they all work together. When I put in test data I am using actual data that I would like to stay in the database. This would just help me not have to reenter the data later. Thanks in advance for any help or information that could help me better understand the process.

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• Giving writing permissions for IIS user at Windows 2003 Server

  - by Steve

  I am running a website over Windows 2003 Server and IIS6 and I am having problems to write or delete files in some temporary folder obtaining this kind of warmings: Warning: unlink(C:\Inetpub\wwwroot\cakephp\app\tmp\cache\persistent\myapp_cake_core_cake_): Permission denied in C:\Inetpub\wwwroot\cakephp\lib\Cake\Cache\Engine\FileEngine.php on line 254 I went to the tmp directory and at the properties I gave the IIS User the following permissions: Read & Execute List folder Contents Read And it still showing the same warnings. When I am on the properties window, if I click on Advanced the IIS username appears twice. One with Allow type and read & execute permissions and the other with Deny type and Special permissions. My question is: Should I give this user not only the Read & Execute permissions but also this ones?: Create Attributes Create Files/ Write Data Create Folders/ Append Data Delete Subfolders and Files Delete They are available to select if I Click on the edit button over the username. Wouldn't I be opening a security hole if I do this? Otherwise, how can I do to read and delete the files my website uses? Thanks.

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• Object equality in context of hibernate / webapp

  - by bert

  How do you handle object equality for java objects managed by hibernate? In the 'hibernate in action' book they say that one should favor business keys over surrogate keys. Most of the time, i do not have a business key. Think of addresses mapped to a person. The addresses are keeped in a Set and displayed in a Wicket RefreshingView (with a ReuseIfEquals strategy). I could either use the surrogate id or use all fields in the equals() and hashCode() functions. The problem is that those fields change during the lifetime ob the object. Either because the user entered some data or the id changes due to JPA merge() being called inside the OSIV (Open Session in View) filter. My understanding of the equals() and hashCode() contract is that those should not change during the lifetime of an object. What i have tried so far: equals() based on hashCode() which uses the database id (or super.hashCode() if id is null). Problem: new addresses start with an null id but get an id when attached to a person and this person gets merged() (re-attached) in the osiv-filter. lazy compute the hashcode when hashCode() is first called and make that hashcode @Transitional. Does not work, as merge() returns a new object and the hashcode does not get copied over. What i would need is an ID that gets assigned during object creation I think. What would be my options here? I don't want to introduce some additional persistent property. Is there a way to explicitly tell JPA to assign an ID to an object? Regards

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