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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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  • 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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  • 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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  • 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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  • 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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  • 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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  • prevent race condition without using locks C++

    - by Hristo
    How do I prevent a race condition with locking or using mutexes/semaphors in C++? I'm dealing with a nested for loop in which I will be setting a value in an array: for (int i = 0; i < m; ++i) for (int j = 0; j < n; ++j) for (int k = 0; k < o; ++k) array[k] += foo(...); More or less, I want to deal with this so that I can ensure different threads running at the same time don't write to array[k] at the same time. Any suggestions on how to approach this? Thanks, Hristo

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  • iPhone: One Object, One Thread

    - by GingerBreadMane
    On the iPhone, I would like to do some operations on an image in a separate thread. Rather than dealing with semiphores, locking, etc., I'd like to use the 'One Object, One Thread' method of safely writing this concurrent operation. I'm not sure what is the correct way to copy my object into a new thread so that the object is not accessed in the main thread. Do I use the 'copy' method? If so, do I do this before the thread or inside the thread? ... -(void)someMethod{ UIImage *myImage; [NSThread detachNewThreadSelector:@selector(getRotatedImage:) toTarget:self withObject:myImage]; } -(void)getRotatedImage:(UIImage *)image{ ... ... UIImage *copiedImage = [image copy]; ... ... }

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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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  • Best way to identify and dispose locked thread in java.

    - by Bala R
    I have to call a function 3rd party module on a new thread. From what I've seen, the call either completes quickly if everything went well or it just hangs for ever locking up the thread. What's a good way to start the thread and make the call and wait for a few secs and if the thread is still alive, then assuming it's locked up, kill (or stop or abandon) the thread without using any deprecated methods. I have something like this for now, but I'm not sure if this is the best way to do it and I want to avoid calling Thread.stop() as it's deprecated. Thanks. private void foo() throws Exception { Runnable runnable = new Runnable() { @Override public void run() { // stuff that could potentially lock up the thread. } }; Thread thread; thread = new Thread(runnable); thread.start(); thread.join(3500); if (thread.isAlive()) { thread.stop(); throw new Exception(); } }

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  • How do I implement .net plugins without using AppDomains?

    - by Abtin Forouzandeh
    Problem statement: Implement a plug-in system that allows the associated assemblies to be overwritten (avoid file locking). In .Net, specific assemblies may not be unloaded, only entire AppDomains may be unloaded. I'm posting this because when I was trying to solve the problem, every solution made reference to using multiple AppDomains. Multiple AppDomains are very hard to implement correctly, even when architected at the start of a project. Also, AppDomains didn't work for me because I needed to transfer Type across domains as a setting for Speech Server worfklow's InvokeWorkflow activity. Unfortunately, sending a type across domains causes the assembly to be injected into the local AppDomain. Also, this is relevant to IIS. IIS has a Shadow Copy setting that allows an executing assembly to be overwritten while its loaded into memory. The problem is that (at least under XP, didnt test on production 2003 servers) when you programmatically load an assembly, the shadow copy doesnt work (because you are loading the DLL, not IIS).

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  • ASP.Net Architecture Specific to Shared/Static functions

    - by Maxim Gershkovich
    Hello All, Could someone please advise in the context of a ASP.Net application is a shared/static function common to all users? If for example you have a function Public shared function GetStockByID(StockID as Guid) as Stock Is that function common to all current users of your application? Or is the shared function only specific to the current user and shared in the context of ONLY that current user? So more specifically my question is this, besides database concurrency issues such as table locking do I need to concern myself with threading issues in shared functions in an ASP.Net application? In my head; let’s say my application namespace is MyTestApplicationNamespace. Everytime a new user connects to my site a new instance of the MyTestApplicationNamespace is created and therefore all shared functions are common to that instance and user but NOT common across multiple users. Is this correct?

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  • MEMORY(HEAP) vs. InnoDB in a Read and Write Environment

    - by Johannes
    I want to program a real-time application using MySQL. It needs a small table (less than 10000 rows) that will be under heavy read (scan) and write (update and some insert/delete) load. I am really speaking of 10000 updates or selects per second. These statements will be executed on only a few (less than 10) open mysql connections. The table is small and does not contain any data that needs to be stored on disk. So I ask which is faster: InnoDB or MEMORY (HEAP)? My thoughts are: Both engines will probably serve SELECTs directly from memory, as even InnoDB will cache the whole table. What about the UPDATEs? (innodb_flush_log_at_trx_commit?) My main concern is the locking behavior: InnoDB row lock vs. MEMORY table lock. Will this present the bottleneck in the MEMORY implementation? Thanks for your thoughts!

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  • Data access strategy for a site like SO - sorted SQL queries and simultaneous updates that affect th

    - by Kaleb Brasee
    I'm working on a Grails web app that would be similar in access patterns to StackOverflow or MyLifeIsAverage - users can vote on entries, and their votes are used to sort a list of entries based on the number of votes. Votes can be placed while the sorted select queries are being performed. Since the selects would lock a large portion of the table, it seems that normal transaction locking would cause updates to take forever (given enough traffic). Has anyone worked on an app with a data access pattern such as this, and if so, did you find a way to allow these updates and selects to happen more or less concurrently? Does anyone know how sites like SO approach this? My thought was to make the sorted selects dirty reads, since it is acceptable if they're not completely up to date all of the time. This is my only idea for possibly improving performance of these selects and updates, but I thought someone might know a better way.

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