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  • JPA optimistic lock - setting @Version to entity class cause query to include VERSION as column

    - by masato-san
    I'm using JPA Toplink Essential, Netbean6.8, GlassFish v3 In my Entity class I added @Version annotation to enable optimistic locking at transaction commit however after I added the annotation, my query started including VERSION as column thus throwing SQL exception. None of this is mentioned in any tutorial I've seen so far. What could be wrong? Snippet public class MasatosanTest2 implements Serializable { private static final long serialVersionUID = 1L; @Id @Basic(optional = false) @Column(name = "id") private Integer id; @Column(name = "username") private String username; @Column(name = "note") private String note; //here adding Version @Version int version; query used: SELECT m FROM MasatosanTest2 m Internal Exception: com.microsoft.sqlserver.jdbc.SQLServerException Call: SELECT id, username, note, VERSION FROM MasatosanTest2

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  • Is AsParallel() good practice in a web environment?

    - by Bjorn Bailleul
    I have no doubt that for client applications, AsParallel() will bring some out-of-the-box performance gains. But what if I would use it in a web environment. Let's say I have a widget framework that loops over all widgets to get their data and render output. This would parallelize great no? I do have my doubts on using AsParallel() in this scenario. What if I have a large number of visitors for my site, isn't IIS going to use multiple threads to handle all requests? Aren't there going to be locking issues presented after a while, or threads dying because all processors are in use? It's just a thought, what do you think about this?

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  • How do you handle files that can't support concurrent edits in Mercurial?

    - by Scott Whitlock
    I'm using Mercurial with TortoiseHg. Each developer has their own repositories, and there's one central repository on the server for synchronizing our changes. (This will sound lame, but we're using it to manage the source for a legacy VB6 project. Nothing we can do about that...) As has been pointed out elsewhere, there is a big problem in VB6 with merging the .frx (form resources) files. So code changes seem to merge fine, but if two developers both make changes at the same time in the form design view, we can't merge. I'm ok with disallowing concurrent edits, but of course the whole point of Mercurial is that it's distributed so there is no option to force a file to be locked before editing. I don't believe there's a Mercurial solution for this, so I'm wondering: other developers who are using Mercurial for version control, do you have some 3rd party tool that assists with locking files for editing in the cases where it's necessary? Did we make a mistake using Mercurial instead of something like SVN?

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  • How do you implement Software Transactional Memory?

    - by Joseph Garvin
    In terms of actual low level atomic instructions and memory fences (I assume they're used), how do you implement STM? The part that's mysterious to me is that given some arbitrary chunk of code, you need a way to go back afterward and determine if the values used in each step were valid. How do you do that, and how do you do it efficiently? This would also seem to suggest that just like any other 'locking' solution you want to keep your critical sections as small as possible (to decrease the probability of a conflict), am I right? Also, can STM simply detect "another thread entered this area while the computation was executing, therefore the computation is invalid" or can it actually detect whether clobbered values were used (and thus by luck sometimes two threads may execute the same critical section simultaneously without need for rollback)?

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  • Async Socket Listener on separate thread - VB.net

    - by TheHockeyGeek
    I am trying to use the code from Microsoft for an Async Socket connection. It appears the listener runs in the main thread locking the GUI. I am new at both socket connections and multi-threading all at the same time. Having a hard time getting my mind wrapped around this all at once. The code used is at http://msdn.microsoft.com/en-us/library/fx6588te.aspx Using this example, how can I move the listener to its own thread? Public Shared Sub Main() ' Data buffer for incoming data. Dim bytes() As Byte = New [Byte](1023) {} ' Establish the local endpoint for the socket. Dim ipHostInfo As IPHostEntry = Dns.GetHostEntry(Dns.GetHostName()) Dim ipAddress As IPAddress = ipHostInfo.AddressList(1) Dim localEndPoint As New IPEndPoint(ipAddress, 11000) ' Create a TCP/IP socket. Dim listener As New Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp) ' Bind the socket to the local endpoint and listen for incoming connections. listener.Bind(localEndPoint) listener.Listen(100)

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  • NServiceBus is blocking when hosted in ASP.NET web application

    - by Dale Niemeyer
    Hello, I created a simple web application where a search form is filled out, submit button clicked, and a message is sent with the search parameters via nServiceBus. I also have a handler in the same project that picks up the message (from the same queue). For some reason, the web server process blocks until after the message is picked up, is there any reason for this? I set a breakpoint in the message handler and it breaks before the request finishes... locking the browser until I allow the code to continue. I would expect control to return to the browser regardless of when the handler gets fired... Thanks, D.Niemeyer

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  • Multithreading and booleans

    - by Ikaso
    Hi Everyone, I have a class that contains a boolean field like this one: public class MyClass { private boolean boolVal; public boolean BoolVal { get { return boolVal; } set { boolVal = value; } } } The field can be read and written from many threads using the property. My question is if I should fence the getter and setter with a lock statement? Or should I simply use the volatile keyword and save the locking? Or should I totally ignore multithreading since getting and setting boolean values atomic? regards,

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  • Can i lock a record from a join sql statment using ROWLOCK,UPDLOCK ?

    - by Andrea.Ko
    I have a store procedure to get the data i want: SELECT a.SONum, a.Seq1, a.SptNum, a.Qty1, a.SalUniPriP, a.PayNum, a.InvNum, a.BLNum, c.ETD, c.ShpNum, f.IssBan FROM OrdD a JOIN OrdH b ON a.SONum = b.SONum LEFT JOIN Invh c ON a.InvNum = c.InvNum LEFT JOIN cus d ON b.CusCod = d.CusCod LEFT JOIN BL e ON a.BLNum = e.BLNum LEFT JOIN PayMasH f ON f.PayNum = a.PayNum LEFT JOIN Shipment g ON g.ShpNum = c.ShpNum WHERE b.CusCod IN (SELECT CusCod FROM UsrInc WHERE UseID=@UserID and UseLev=@UserLvl) AND d.CusGrp = @CusGrp After i get those records into cursor, i used RowLock, UpdLock to lock all the related invoice number. SELECT InvNum FROM Invh WITH (ROWLOCK,UPDLOCK) WHERE InvNum = Can i issue locking on the table INVH at the point i select the table from a few table using join command? Any advice, please!

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  • What does Visual Studio 2008 do when I add an assembly reference?

    - by tk-421
    When I add a reference to an assembly (living in the GAC) to web.config in an ASP.NET project, what does Visual Studio do? [This is related to an earlier question pertaining to BusinessObjects: http://stackoverflow.com/questions/2379615/ ] When I add "CrystalDecisions.Enterprise" and "CrystalDecisions.Enterprise.Framework" to the assemblies element in web.config, VS thinks long and hard about it, locking me out for a couple of minutes while it scrutinizes the newcomers. What is it doing during this time? I Googled this but came up empty. I can make some educated guesses (IntelliSense integration, perhaps?) but would ideally like to find some documentation describing exactly what's going on. Ultimately I'm hoping to learn why these BO references are making VS take several minutes to open my projects (I struck out on the SAP forums).

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  • How to make mysql accept connections externally

    - by Tam
    I have a VPS and I want to make mysql DB accept connection externally (from my PC for instance). I have Debian Linux installed on the server. I checked some tutorials online and they said to comment out: bind-address = 127.0.0.1 But this didn't seem to help! is there anything specific for VPSs? or Am I missing something else? The command that runs mysql is: /usr/sbin/mysqld --basedir=/usr --datadir=/var/lib/mysql --user=mysql --pid-file=/var/run/mysqld/mysqld.pid --skip-external-locking --port=3306 --socket=/var/run/mysqld/mysqld.sock

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  • Why better isolation level means better performance in SQL Server

    - by Oleg Zhylin
    When measuring performance on my query I came up with a dependency between isolation level and elapsed time that was surprising to me READUNCOMMITTED - 409024 READCOMMITTED - 368021 REPEATABLEREAD - 358019 SERIALIZABLE - 348019 Left column is table hint, and the right column is elapsed time in microseconds (sys.dm_exec_query_stats.total_elapsed_time). Why better isolation level gives better performance? This is a development machine and no concurrency whatsoever happens. I would expect READUNCOMMITTED to be the fasted due to less locking overhead. Update: I did measure this with DBCC DROPCLEANBUFFERS DBCC FREEPROCCACHE issued and Profiler confirms there're no cache hits happening. Update2: The query in question is an OLAP one and we need to run it as fast as possible. Closing the production server from outside world to get the computation done is not out of question if this gives performance benefits.

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  • Popup Dialog Box Manager using PureMVC

    - by webwise
    I am developing a a game in Flash using the PureMVC framework. From time to time I need to show dialog pop-up window to get a user response back (e.g. "Cancel", "OK" and other kinds of asynchronous user feedback) while "locking" the background for interactivity. I need some management for my pop-ups: all pop-up notifications should be stacked up, so that if two (or more) pop-up messages are initiated at the same time I show them one by one. What's the best practice here? Should I employ a proxy to manage my pop-ups (sounds unreasonable). How do I get feedback back from my dialog? using notifications?

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  • Anyone up to creating a tomcat based alternative for GAE?

    - by bach
    Hi, If we had the possibility to run GAE app without any code change on our servlet engine that would be great because: in case that google changes their billing policy we can just jump to our own server or in case their current policy doesn't fit our app needs we can do stuff which is not allowed in the GAE, compromising a 1 JVM, 1 DB We don't actually need a distributed system but more of a realtime system with synchronize, true locking mechanisms, other servers/software installed on the server machine, socket interface etc... Such a package should include at least: TomCat (or equivalent) DataNucleus Access Platform (Task Queue service) Any idea if it's easy to get such a thing or if it's already exist somewhere? Thanks

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  • How to play sounds in locked mode on iPhone

    - by Joe Mallik
    Everybody knows the standard procedure to keep your app alive, after the user pressed the lock button (silent sound). If I start a sound with AVAudioPlayer (before the iphone is locked), the sound plays till it's end (after locking). The app is still running. If I try to start another sound while the iPhone is locked, it will never get played. All the other things work as well but the sound doesn't. How can I play a sound while the iphone is locked?

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  • ADF vs. EJB/Spring: Where should I invest my time?

    - by Arthur Huxley
    I am a junior Java SE developer, planning to become a Java Standard Edition professional. Which technologies/frameworks will be the smartest thing for me to learn? I will invest a lot of time and energy on the technologies that I eventually choose and it will be the basis for my carreer. I need to choose carefully. I have one question in particular regarding Oracle ADF: How can it be better than Spring or EJB 3.x? No offense to the ADF developers - and please excuse my ignorance - but is there a reason for using ADF other than locking customers to Oracle products? If ADF is an inferior technology I fear I will be making a mistake choosing to specialize in ADF.

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  • Is it inmoral to put a captcha on a login form?

    - by azkotoki
    In a recent project I put a captcha test on a login form, in order to stop possible brute force attacks. The inmediate reaction of other coworkers was a request to remove it, saying that it was innapropiate for that purpose, and that it was quite exotic to see a captcha in that place. I've seen captcha images on signup, contact, password recovery forms, etc. So I personally don't see innapropiate to put a captcha also on a place like that. Well, it obviously burns down usability a little bit, but it's a matter of time and getting used to it. With the lack of a captcha test, one would have to put some sort of blacklist / account locking mechanism, which also has some drawbacks. Is it a good choice for you? Am I getting somewhat captcha-aholic and need some sort of group therapy? Thanks in advance.

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  • Thread Local Storage and local method variables

    - by miguel
    In c#, each thread has its own stack space. If this is the case, why is the following code not thread-safe? (It is stated that this code is thread-safe on this post: Locking in C# class Foo { private int count = 0; public void TrySomething() { count++; } } As count is an int (stack variable), surely this value would be isolated to an individual thread, on its own stack, and therefore thread-safe? I am probably missing something here, but I dont understand what is actually in Thread Local Storage if not stack-based variables for the thread?

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  • Are concurrency issues possible when using the WCF Service Behavoir attribute set to ConcurrencyMode

    - by Brandon Linton
    We have a WCF service that makes a good deal of transactional NHibernate calls. Occasionally we were seeing SQL timeouts, even though the calls were updating different rows and the tables were set to row level locking. After digging into the logs, it looks like different threads were entering the same point in the code (our transaction using block), and an update was hanging on commit. It didn't make sense, though, because we believed that the following service class attribute was forcing a unique execution thread per service call: [ServiceBehavior(ConcurrencyMode = ConcurrencyMode.Multiple, InstanceContextMode = InstanceContextMode.PerCall)] We recently changed the concurrency mode to ConcurrencyMode.Single and haven't yet run into any issues, but the bug was very difficult to reproduce (if anyone has any thoughts on flushing a bug like that out, let me know!). Anyway, that all brings me to my question: shouldn't an InstanceContextMode of PerCall enforce thread-safety within the service, even if the ConcurrencyMode is set to multiple? How would it be possible for two calls to be serviced by the same service instance? Thanks!

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  • How can I find file system concurrency issues ?

    - by krosenvold
    I have an application running on Linux, and I find myself wanting windows (!). The problem is that every 1000 times or so I run into concurrency problems that are consistent with concurrent reading/writing of files. I am fairly sure that this behavior would be prohibited by file locking under Windows, but I don't have any sufficiently fast windows box to check. There is simply too much file access (too much data) to expect strace to work reliably - the sheer volume of output is likely to change the problem too. It also happens on different files every time. Ideally I would like to change/reconfigure the linux file system to be more restrictive (as in fail-fast) wrt concurrent access. Are there any tools/settings I can use to achieve this ?

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  • MySQL - are FK's useful / viable in a web app?

    - by yoda
    Hi all, I've encountered this discussion related to FK's and web applications. Basically some people say that FK's in web applications doesn't represent a real improvement and can even make the application slower in some cases. What do you guys think, what's your experience? -- A quote from Heikki Tuuri, creator of InnoDB engine, founder and CEO of Innobase: InnoDB checks foreign keys as soon as a row is updated, no batching is performed or checks delayed till transaction commit Foreign keys are often serious performance overhead, but help maintain data consistency Foreign Keys increase amount of row level locking done and can make it spread to a lot of tables besides the ones directly updated

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  • Is it possible to exclude some files from checkin (TFS) ?

    - by Thomas Wanner
    We use configuration files within various projects under source control (TFS), where each developer has to make some adjustments in his local copy to configure his environment. The build process takes care about replacing the config files with the server configuration as a part of the deployment, so it doesn't actually matter what is in the repository. However, we would anyway like to keep some kind of a default non-breaking version of config files in the repository, so that e.g. people not involved in the particular project won't run into troubles because of local misconfiguration. We tried to resolve this by introducing the check-in policy that simply forbids to check-in the config files. This works fine, but just because we're lazy to always uncheck those checkboxes in the pending changes window, the question comes : is it possible to transparently disable the check-in of particular files without keeping them out of source control (e.g. locking their current version) ?

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  • Are there any nasty side affects if i lock the HttpContext.Current.Cache.Insert method

    - by Ekk
    Apart from blocking other threads reading from the cache what other problems should I be thinking about when locking the cache insert method for a public facing website. The actual data retrieval and insert into the cache should take no more than 1 second, which we can live with. More importantly i don't want multiple thread potentially all hitting the Insert method at the same time. The sample code looks something like: public static readonly object _syncRoot = new object(); if (HttpContext.Current.Cache["key"] == null) { lock (_syncRoot) { HttpContext.Current.Cache.Insert("key", "DATA", null, DateTime.Now.AddMinutes(5), Cache.NoSlidingExpiration, CacheItemPriority.Normal, null); } } Response.Write(HttpContext.Current.Cache["key"]);

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  • TSQL ID generation

    - by Markus
    Hi. I have a question regarding locking in TSQL. Suppose I have a the following table: A(int id, varchar name), where id is the primary key, but is NOT an identity column. I want to use the following pseudocode to insert a value into this table: lock (A) uniqueID = GenerateUniqueID() insert into A values (uniqueID, somename) unlock(A) How can this be accomplished in terms of TSQL? The computation of the next id should be done with the table A locked in order to avoid other sessions to do the same operation at the same time and get the same id.

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  • File Encrypt/Decrypt under load?

    - by chopps
    I found an interesting article about encrypting and decrypting files but since it uses a file.dat to store the key this will run into problems when theres alot of users on the site dealing with alot of files. http://www.codeproject.com/KB/security/VernamEncryption.aspx?display=Print Should a new file be created every time a file needs decrypting or would there be a better way to do this? UPDATE: Here is what im using to avoid the locking problems. using (Mutex FileLock = new Mutex(true, System.Guid.NewGuid().ToString())) { try { FileLock.WaitOne(); using (FileStream fs = new FileStream(keyFile, FileMode.Open)) { keyBytes = new byte[fs.Length]; fs.Read(keyBytes, 0, keyBytes.Length); } } catch (Exception ex) { EventLog.LogEvent(ex); } finally { FileLock.ReleaseMutex(); } } I tested it on 1000 TIFFs doing both encryption and decryption without any errors.

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  • Setting application affinity in gdb

    - by Marcus Ahlberg
    Is there a simple way of setting the affinity of the application I'm debugging without locking gdb to the same core? The reason why I'm asking is that the application is running with real time priority and it needs to run on a single core. At the moment I use this command line taskset -c 3 gdbserver :1234 ./app.out but the application stops responding and freezes the gdb server, making debugging impossible. I suspect that the real time priority of the application prevents gdb from executing. If I start the application and then start gdb without affinity setting, then I can attach and debug the application without gdb freezing. Is there a simple way to start gdb and the application with different affinities? Or preferably: Is there a gdb command to set affinity of the child process?

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