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• Why MSMQ won't send a space character?

  - by cyclotis04

  I'm exploring MSMQ services, and I wrote a simple console client-server application that sends each of the client's keystrokes to the server. Whenever hit a control character (DEL, ESC, INS, etc) the server understandably throws an error. However, whenever I type a space character, the server receives the packet but doesn't throw an error and doesn't display the space. Server: namespace QIM { class Program { const string QUEUE = @".\Private$\qim"; static MessageQueue _mq; static readonly object _mqLock = new object(); static XmlSerializer xs; static void Main(string[] args) { lock (_mqLock) { if (!MessageQueue.Exists(QUEUE)) _mq = MessageQueue.Create(QUEUE); else _mq = new MessageQueue(QUEUE); } xs = new XmlSerializer(typeof(string)); _mq.BeginReceive(new TimeSpan(0, 1, 0), new object(), OnReceive); while (Console.ReadKey().Key != ConsoleKey.Escape) { } } static void OnReceive(IAsyncResult result) { Message msg; lock (_mqLock) { try { msg = _mq.EndReceive(result); Console.Write("."); Console.Write(xs.Deserialize(msg.BodyStream)); } catch (Exception ex) { Console.Write(ex); } } _mq.BeginReceive(new TimeSpan(0, 1, 0), new object(), OnReceive); } } } Client: namespace QIM_Client { class Program { const string QUEUE = @".\Private$\qim"; static MessageQueue _mq; static void Main(string[] args) { if (!MessageQueue.Exists(QUEUE)) _mq = MessageQueue.Create(QUEUE); else _mq = new MessageQueue(QUEUE); ConsoleKeyInfo key = new ConsoleKeyInfo(); while (key.Key != ConsoleKey.Escape) { key = Console.ReadKey(); _mq.Send(key.KeyChar.ToString()); } } } } Client Input: Testing, Testing... Server Output: .T.e.s.t.i.n.g.,..T.e.s.t.i.n.g...... You'll notice that the space character sends a message, but the character isn't displayed.

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• How to Perform Continues Iteration over Shared Dictionary in Multi-threaded Environment

  - by Mubashar Ahmad

  Dear Gurus. Note Pls do not tell me regarding alternative to custom session, Pls answer only relative to the Pattern Scenario I have Done Custom Session Management in my application(WCF Service) for this I have a Dictionary shared to all thread. When a specific function Gets called I add a New Session and Issue SessionId to the client so it can use that sessionId for rest of his calls until it calls another specific function, which terminates this session and removes the session from the Dictionary. Due to any reason Client may not call session terminator function so i have to implement time expiration logic so that i can remove all such sessions from the memory. For this I added a Timer Object which calls ClearExpiredSessions function after the specific period of time. which iterates on the dictionary. Problem: As this dictionary gets modified every time new client comes and leaves so i can't lock the whole dictionary while iterating over it. And if i do not lock the dictionary while iteration, if dictionary gets modified from other thread while iterating, Enumerator will throw exception on MoveNext(). So can anybody tell me what kind of Design i should follow in this case. Is there any standard pattern available.

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• AssemblyResolve event is not firing during compilation of a dynamic assembly for an aspx page.

  - by John

  This one is really pissing me off. Here goes: My goal is to load assemblies at run-time that contain embedded aspx,ascx etc. What I would also like is to not lock the assembly file on disk so I can update it at run-time without having to restart the application (I know this will leave the previous version(s) loaded). To that end I have written a virtual path provider that does the trick. I have subscribed to the CurrentDomain.AssemblyResolve event so as to redirect the framework to my assemblies. The problem is that the when the framework tries to compile the dynamic assembly for the aspx page I get the following: Compiler Error Message: CS0400: The type or namespace name 'Pages' could not be found in the global namespace (are you missing an assembly reference?) Source Error: public class app_resource_pages__version_1_0_0_0__culture_neutral__publickeytoken_null_default_aspx : global::Pages._Default, System.Web.SessionState.IRequiresSessionState, System.Web.IHttpHandle I noticed that if I load the assembly with Assembly.Load(AssemblyName) or Assembly.LoadFrom(filename) I dont get the above error. If I load it with Assembly.Load(byte[]) (so as to not lock it), the exception is thrown but my AssemblyResolve handler, when called is returning the assembly correctly (it is called once). So I am guessing that it is called once when the framework parses the asp markup but not when it tries to create the dynamic assembly for the aspx page.

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• mysql row locking via php

  - by deezee

  I am helping a friend with a web based form that is for their business. I am trying to get it ready to handle multiple users. I have set it up so that just before the record is displayed for editing I am locking the record with the following code. $query = "START TRANSACTION;"; mysql_query($query); $query = "SELECT field FROM table WHERE ID = \"$value\" FOR UPDATE;"; mysql_query($query); (okay that is greatly simplified but that is the essence of the mysql) It does not appear to be working. However, when I go directly to mysql from the command line, logging in with the same user and execute START TRANSACTION; SELECT field FROM table WHERE ID = "40" FOR UPDATE; I can effectively block the web form from accessing record "40" and get the timeout warning. I have tried using BEGIN instead of START TRANSACTION. I have tried doing SET AUTOCOMMIT=0 first and starting the transaction after locking but I cannot seem to lock the row from the PHP code. Since I can lock the row from the command line I do not think there is a problem with how the database is set up. I am really hoping that there is some simple something that I have missed in my reading. FYI, I am developing on XAMPP version 1.7.3 which has Apache 2.2.14, MySQL 5.1.41 and PHP 5.3.1. Thanks in advance. This is my first time posting but I have gleaned alot of knowledge from this site in the past.

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• Can I prevent a Linux user space pthread yielding in critical code?

  - by KermitG

  I am working on an user space app for an embedded Linux project using the 2.6.24.3 kernel. My app passes data between two file nodes by creating 2 pthreads that each sleep until a asynchronous IO operation completes at which point it wakes and runs a completion handler. The completion handlers need to keep track of how many transfers are pending and maintain a handful of linked lists that one thread will add to and the other will remove. // sleep here until events arrive or time out expires for(;;) { no_of_events = io_getevents(ctx, 1, num_events, events, &timeout); // Process each aio event that has completed or thrown an error for (i=0; i<no_of_events; i++) { // Get pointer to completion handler io_complete = (io_callback_t) events[i].data; // Get pointer to data object iocb = (struct iocb *) events[i].obj; // Call completion handler and pass it the data object io_complete(ctx, iocb, events[i].res, events[i].res2); } } My question is this... Is there a simple way I can prevent the currently active thread from yielding whilst it runs the completion handler rather than going down the mutex/spin lock route? Or failing that can Linux be configured to prevent yielding a pthread when a mutex/spin lock is held?

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• Is something along the lines of nested memoization needed here?

  - by Daniel

  System.Transactions notoriously escalates transactions involving multiple connections to the same database to the DTC. The module and helper class, ConnectionContext, below are meant to prevent this by ensuring multiple connection requests for the same database return the same connection object. This is, in some sense, memoization, although there are multiple things being memoized and the second is dependent on the first. Is there some way to hide the synchronization and/or mutable state (perhaps using memoization) in this module, or perhaps rewrite it in a more functional style? (It may be worth nothing that there's no locking when getting the connection by connection string because Transaction.Current is ThreadStatic.) type ConnectionContext(connection:IDbConnection, ownsConnection) = member x.Connection = connection member x.OwnsConnection = ownsConnection interface IDisposable with member x.Dispose() = if ownsConnection then connection.Dispose() module ConnectionManager = let private _connections = new Dictionary<string, Dictionary<string, IDbConnection>>() let private getTid (t:Transaction) = t.TransactionInformation.LocalIdentifier let private removeConnection tid = let cl = _connections.[tid] for (KeyValue(_, con)) in cl do con.Close() lock _connections (fun () -> _connections.Remove(tid) |> ignore) let getConnection connectionString (openConnection:(unit -> IDbConnection)) = match Transaction.Current with | null -> new ConnectionContext(openConnection(), true) | current -> let tid = getTid current // get connections for the current transaction let connections = match _connections.TryGetValue(tid) with | true, cl -> cl | false, _ -> let cl = Dictionary<_,_>() lock _connections (fun () -> _connections.Add(tid, cl)) cl // find connection for this connection string let connection = match connections.TryGetValue(connectionString) with | true, con -> con | false, _ -> let initial = (connections.Count = 0) let con = openConnection() connections.Add(connectionString, con) // if this is the first connection for this transaction, register connections for cleanup if initial then current.TransactionCompleted.Add (fun args -> let id = getTid args.Transaction removeConnection id) con new ConnectionContext(connection, false)

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• Returning pointers in a thread-safe way.

  - by Roddy

  Assume I have a thread-safe collection of Things (call it a ThingList), and I want to add the following function. Thing * ThingList::findByName(string name) { return &item[name]; // or something similar.. } But by doing this, I've delegated the responsibility for thread safety to the calling code, which would have to do something like this: try { list.lock(); // NEEDED FOR THREAD SAFETY Thing *foo = list.findByName("wibble"); foo->Bar = 123; list.unlock(); } catch (...) { list.unlock(); throw; } Obviously a RAII lock/unlock object would simplify/remove the try/catch/unlocks, but it's still easy for the caller to forget. There are a few alternatives I've looked at: Return Thing by value, instead of a pointer - fine unless you need to modify the Thing Add function ThingList::setItemBar(string name, int value) - fine, but these tend to proliferate Return a pointerlike object which locks the list on creation and unlocks it again on destruction. Not sure if this is good/bad practice... What's the right approach to dealing with this?

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• Is there a term for this concept, and does it exist in a static-typed language?

  - by Strilanc

  Recently I started noticing a repetition in some of my code. Of course, once you notice a repetition, it becomes grating. Which is why I'm asking this question. The idea is this: sometimes you write different versions of the same class: a raw version, a locked version, a read-only facade version, etc. These are common things to do to a class, but the translations are highly mechanical. Surround all the methods with lock acquires/releases, etc. In a dynamic language, you could write a function which did this to an instance of a class (eg. iterate over all the functions, replacing them with a version which acquires/releases a lock.). I think a good term for what I mean is 'reflected class'. You create a transformation which takes a class, and returns a modified-in-a-desired-way class. Synchronization is the easiest case, but there are others: make a class immutable [wrap methods so they clone, mutate the clone, and include it in the result], make a class readonly [assuming you can identify mutating methods], make a class appear to work with type A instead of type B, etc. The important part is that, in theory, these transformations make sense at compile-time. Even though an ActorModel<T> has methods which change depending on T, they depend on T in a specific way knowable at compile-time (ActorModel<T> methods would return a future of the original result type). I'm just wondering if this has been implemented in a language, and what it's called.

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• Ensuring that all callbacks were completed before sending a new request through a DuplexChannel usin

  - by Etan

  I am experiencing some issues when using a Callback in a WCF project. First, the server invokes some function Foo on the client which then forwards the request to a Windows Forms GUI: GUI CLASS delegate void DoForward(); public void ForwardToGui() { if (this.cmdSomeButton.InvokeRequired) { DoForward d = new DoForward(ForwardToGui); this.Invoke(d); } else { Process(); // sets result variable in callback class as soon as done } } } CALLBACK CLASS object _m = new object(); private int _result; public int result { get { return _result; } set { _result = value; lock(_m) { Monitor.PulseAll(_m); } } } [OperationContract] public int Foo() { result = 0; Program.Gui.ForwardToGui(); lock(_m) { Monitor.Wait(_m, 30000); } return result; } The problem now is that the user should be able to cancel the process, which doesn't work properly: SERVER INTERFACE [OperationContract] void Cleanup(); GUI CLASS private void Gui_FormClosed(object sender, EventArgs e) { Program.callbackclass.nextAction = -1; // so that the monitor pulses and Foo() returns Program.server.Cleanup(); } The problem with this is that Cleanup() hangs. However, when I close the form when Process() is not running, it works properly. The source seems to be that the Cleanup() is called before the monitor pulses etc and therefore a new request is sent to the server before the last request from the server has not yet been responded. How can I solve this problem? How can I ensure before calling Cleanup() that no Foo() is currently being executed?

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• Sql Compact and __sysobjects

  - by Scott Wisniewski

  I have some SQL Compact queries that create tables inside of transaction. This is mainly because I need to simulate temporary tables, which SQL Compact does not support. I do this by creating a real table, and then dropping it at the end of the transaction. This mostly works. Sometimes, however, when creating the tables Sql Compact will try to acquire PAGE level locks on the __sysobjects table. If there are several concurrent queries running that create "temp" tables, the attempt to acquire a page lock can result in a dead lock followed by a SqlLockTimeout exception. For normal tables I could fix this using a "with (rowlock)" hint. However, because I'm not writing the query to insert into __sysobjets (SQL server does that in response to "create table") I can't do this. Does anyone know of a way I could get around this? I've thought about pulling the table creation out of the transaction, but that opens up the possibility of phantom temporary tables that I'd then need to clean up regularly. Ideally I'd like to avoid that if possible.

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• What's the best way to store Logon User information for Web Application?

  - by Morgan Cheng

  I was once in a project of web application developed on ASP.NET. For each logon user, there is an object (let's call it UserSessionObject here) created and stored in RAM. For each HTTP request of given user, matching UserSessoinObject instance is used to visit user state information and connection to database. So, this UserSessionObject is pretty important. This design brings several problems found later: 1) Since this UserSessionObject is cached in ASP.NET memory space, we have to config load balancer to be sticky connection. That is, HTTP request in single session would always be sent to one web server behind. This limit scalability and maintainability. 2) This UserSessionObject is accessed in every HTTP request. To keep the consistency, there is a exclusive lock for the UserSessionObject. Only one HTTP request can be processed at any given time because it must to obtain the lock first. The performance and response time is affected. Now, I'm wondering whether there is better design to handle such logon user case. It seems Sharing-Nothing-Architecture helps. That means long user info is retrieved from database each time. I'm afraid that would hurt performance. Is there any design pattern for long user web app? Thanks.

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• Unit Testing an Event Firing From a Thread

  - by Dougc

  I'm having a problem unit testing a class which fires events when a thread starts and finishes. A cut down version of the offending source is as follows: public class ThreadRunner { private bool keepRunning; public event EventHandler Started; public event EventHandler Finished; public void StartThreadTest() { this.keepRunning = true; var thread = new Thread(new ThreadStart(this.LongRunningMethod)); thread.Start(); } public void FinishThreadTest() { this.keepRunning = false; } protected void OnStarted() { if (this.Started != null) this.Started(this, new EventArgs()); } protected void OnFinished() { if (this.Finished != null) this.Finished(this, new EventArgs()); } private void LongRunningMethod() { this.OnStarted(); while (this.keepRunning) Thread.Sleep(100); this.OnFinished(); } } I then have a test to check that the Finished event fires after the LongRunningMethod has finished as follows: [TestClass] public class ThreadRunnerTests { [TestMethod] public void CheckFinishedEventFiresTest() { var threadTest = new ThreadRunner(); bool finished = false; object locker = new object(); threadTest.Finished += delegate(object sender, EventArgs e) { lock (locker) { finished = true; Monitor.Pulse(locker); } }; threadTest.StartThreadTest(); threadTest.FinishThreadTest(); lock (locker) { Monitor.Wait(locker, 1000); Assert.IsTrue(finished); } } } So the idea here being that the test will block for a maximum of one second - or until the Finish event is fired - before checking whether the finished flag is set. Clearly I've done something wrong as sometimes the test will pass, sometimes it won't. Debugging seems very difficult as well as the breakpoints I'd expect to be hit (the OnFinished method, for example) don't always seem to be. I'm assuming this is just my misunderstanding of the way threading works, so hopefully someone can enlighten me.

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• Thread mutex behaviour

  - by Alberteddu

  Hi there, I'm learning C. I'm writing an application with multiple threads; I know that when a variable is shared between two or more threads, it is better to lock/unlock using a mutex to avoid deadlock and inconsistency of variables. This is very clear when I want to change or view one variable. int i = 0; /** Global */ static pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER; /** Thread 1. */ pthread_mutex_lock(&mutex); i++; pthread_mutex_unlock(&mutex); /** Thread 2. */ pthread_mutex_lock(&mutex); i++; pthread_mutex_unlock(&mutex); This is correct, I think. The variable i, at the end of the executions, contains the integer 2. Anyway, there are some situations in which I don't know exactly where to put the two function calls. For example, suppose you have a function obtain(), which returns a global variable. I need to call that function from within the two threads. I have also two other threads that call the function set(), defined with a few arguments; this function will set the same global variable. The two functions are necessary when you need to do something before getting/setting the var. /** (0) */ /** Thread 1, or 2, or 3... */ if(obtain() == something) { if(obtain() == somethingElse) { // Do this, sometimes obtain() and sometimes set(random number) (1) } else { // Do that, just obtain(). (2) } } else { // Do this and do that (3) // If # of thread * 3 > 10, then set(3*10) For example. (4) } /** (5) */ Where I have to lock, and where I have to unlock? The situation can be, I think, even more complex. I will appreciate an exhaustive answer. Thank you in advance. —Alberto

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• Is there a better way to throttle a high throughput job?

  - by ChaosPandion

  I created a simple class that shows what I am trying to do without any noise. Feel free to bash away at my code. That's why I posted it here. public class Throttled : IDisposable { private readonly Action work; private readonly Func<bool> stop; private readonly ManualResetEvent continueProcessing; private readonly Timer throttleTimer; private readonly int throttlePeriod; private readonly int throttleLimit; private int totalProcessed; public Throttled(Action work, Func<bool> stop, int throttlePeriod, int throttleLimit) { this.work = work; this.stop = stop; this.throttlePeriod = throttlePeriod; this.throttleLimit = throttleLimit; continueProcessing = new ManualResetEvent(true); throttleTimer = new Timer(ThrottleUpdate, null, throttlePeriod, throttlePeriod); } public void Dispose() { throttleTimer.Dispose(); ((IDisposable)continueProcessing).Dispose(); } public void Execute() { while (!stop()) { if (Interlocked.Increment(ref totalProcessed) > throttleLimit) { lock (continueProcessing) { continueProcessing.Reset(); } if (!continueProcessing.WaitOne(throttlePeriod)) { throw new TimeoutException(); } } work(); } } private void ThrottleUpdate(object state) { Interlocked.Exchange(ref totalProcessed, 0); lock (continueProcessing) { continueProcessing.Set(); } } }

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• optimistic and pessimistic locks

  - by billmce

  Working on my first php/Codeigniter project and I’ve scoured the ‘net for information on locking access to editing data and haven’t found very much information. I expect it to be a fairly regular occurrence for 2 users to attempt to edit the same form simultaneously. My experience (in the stateful world of BBx, filePro, and other RAD apps) is that the data being edited is locked using a pessimistic lock—one user has access to the edit form at the time. The second user basically has to wait for the first to finish. I understand this can be done using Ajax sending XMLHttpRequests to maintain a ‘lock’ database. The php world, lacking state, seems to prefer optimistic locking. If I understand it correctly it works like this: both users get to access the data and they each record a ‘before changes’ version of the data. Before saving their changes, the data is once again retrieved and compared the ‘before changes’ version. If the two versions are identical then the users changes are written. If they are different; the user is shown what has changed since he/she started editing and some mechanism is added to resolve the differences—or the user is shown a ‘Sorry, try again’ message. I’m interested in any experience people here have had with implementing both pessimistic and optimistic locking. If there are any libraries, tools, or ‘how-to’s available I’m appreciate a link. Thanks

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• How do I wait for all other threads to finish their tasks?

  - by Mike

  I have several threads consuming tasks from a queue using something similar to the code below. The problem is that there is one type of task which cannot run while any other tasks are being processed. Here is what I have: while (true) // Threaded code { while (true) { lock(locker) { if (close_thread) return; task = GetNextTask(); // Get the next task from the queue } if (task != null) break; wh.WaitOne(); // Wait until a task is added to the queue } task.Run(); } And this is kind of what I need: while (true) { while (true) { lock(locker) { if (close_thread) return; if (disable_new_tasks) { task = null; } else { task = GetNextTask(); } } if (task != null) break; wh.WaitOne(); } if(!task.IsThreadSafe()) { // I would set this to false inside task.Run() at // the end of the non-thread safe task disable_new_tasks = true; Wait_for_all_threads_to_finish_their_current_tasks(); } task.Run(); } The problem is I don't know how to achive this without creating a mess.

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• Any techniques to interrupt, kill, or otherwise unwind (releasing synchronization locks) a single de

  - by gojomo

  I have a long-running process where, due to a bug, a trivial/expendable thread is deadlocked with a thread which I would like to continue, so that it can perform some final reporting that would be hard to reproduce in another way. Of course, fixing the bug for future runs is the proper ultimate resolution. Of course, any such forced interrupt/kill/stop of any thread is inherently unsafe and likely to cause other unpredictable inconsistencies. (I'm familiar with all the standard warnings and the reasons for them.) But still, since the only alternative is to kill the JVM process and go through a more lengthy procedure which would result in a less-complete final report, messy/deprecated/dangerous/risky/one-time techniques are exactly what I'd like to try. The JVM is Sun's 1.6.0_16 64-bit on Ubuntu, and the expendable thread is waiting-to-lock an object monitor. Can an OS signal directed to an exact thread create an InterruptedException in the expendable thread? Could attaching with gdb, and directly tampering with JVM data or calling JVM procedures allow a forced-release of the object monitor held by the expendable thread? Would a Thread.interrupt() from another thread generate a InterruptedException from the waiting-to-lock frame? (With some effort, I can inject an arbitrary beanshell script into the running system.) Can the deprecated Thread.stop() be sent via JMX or any other remote-injection method? Any ideas appreciated, the more 'dangerous', the better! And, if your suggestion has worked in personal experience in a similar situation, the best!

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• How can one enforce calling a base class function after derived class constructor?

  - by Mike Elkins

  I'm looking for a clean C++ idiom for the following situation: class SomeLibraryClass { public: SomeLibraryClass() { /* start initialization */ } void addFoo() { /* we are a collection of foos */ } void funcToCallAfterAllAddFoos() { /* Making sure this is called is the issue */ } }; class SomeUserClass : public SomeLibraryClass { public: SomeUserClass() { addFoo(); addFoo(); addFoo(); // SomeUserClass has three foos. } }; class SomeUserDerrivedClass : public SomeUserClass { public: SomeUserDerrivedClass() { addFoo(); // This one has four foos. } }; So, what I really want is for SomeLibraryClass to enforce the calling of funcToCallAfterAllAddFoos at the end of the construction process. The user can't put it at the end of SomeUserClass::SomeUserClass(), that would mess up SomeUserDerrivedClass. If he puts it at the end of SomeUserDerrivedClass, then it never gets called for SomeUserClass. To further clarify what I need, imagine that /* start initialization */ acquires a lock, and funcToCallAfterAllAddFoos() releases a lock. The compiler knows when all the initializations for an object are done, but can I get at that information by some nice trick?

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• NULL pointer dereference in swiotlb_unmap_sg_attrs() on disk IO

  - by Inductiveload

  I'm getting an error I really don't understand when reading or writing files using a PCIe block device driver. I seem to be hitting an issue in swiotlb_unmap_sg_attrs(), which appears to be doing a NULL dereference of the sg pointer, but I don't know where this is coming from, as the only scatterlist I use myself is allocated as part of the device info structure and persists as long as the driver does. There is a stacktrace to go with the problem. It tends to vary a bit in exact details, but it always crashes in swiotlb_unmap_sq_attrs(). I think it's likely I have a locking issue, as I am not sure how to handle the locks around the IO functions. The lock is already held when the request function is called, I release it before the IO functions themselves are called, as they need an (MSI) IRQ to complete. The IRQ handler updates a "status" value, which the IO function is waiting for. When the IO function returns, I then take the lock back up and return to request queue handling. The crash happens in blk_fetch_request() during the following: if (!__blk_end_request(req, res, bytes)){ printk(KERN_ERR "%s next request\n", DRIVER_NAME); req = blk_fetch_request(q); } else { printk(KERN_ERR "%s same request\n", DRIVER_NAME); } where bytes is updated by the request handler to be the total length of IO (summed length of each scatter-gather segment).

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• While in a transaction, how can reads to an affected row be prevented until the transaction is done?

  - by Mahn

  I'm fairly sure this has a simple solution, but I haven't been able to find it so far. Provided an InnoDB MySQL database with the isolation level set to SERIALIZABLE, and given the following operation: BEGIN WORK; SELECT * FROM users WHERE userID=1; UPDATE users SET credits=100 WHERE userID=1; COMMIT; I would like to make sure that as soon as the select inside the transaction is issued, the row corresponding to userID=1 is locked for reads until the transaction is done. As it stands now, UPDATEs to this row will wait for the transaction to be finished if it is in process, but SELECTs simply will read the previous value. I understand this is the expected behaviour in this case, but I wonder if there is a way to lock the row in such a way that SELECTs will also wait until the transaction is finished to return the values? The reason I'm looking for that is that at some point, and with enough concurrent users, it could happen that while the previous transaction is in process someone else reads the "credits" to calculate something else. Ideally the code run by that someone else should wait for the transaction to finish to use the new value, because otherwise it could lead to irreversible desync issues. Note that I don't want to lock the entire table for reads, just the specific row. Also, I could add a boolean "locked" field to the tables and set it to 1 every time I'm starting a transaction but I don't really feel this is the most elegant solution here, unless there is absolutely no other way to handle this through mysql directly.

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• How do I make this Java code operate properly? [Multi-threaded, race condition]

  - by Fixee

  I got this code from a student, and it does not work properly because of a race condition involving x++ and x--. He added synchronized to the run() method trying to get rid of this bug, but obviously this only excludes threads from entering run() on the same object (which was never a problem in the first place) but doesn't prevent independent objects from updating the same static variable x at the same time. public class DataRace implements Runnable { static volatile int x; public synchronized void run() { for (int i = 0; i < 10000; i++) { x++; x--; } } public static void main(String[] args) throws Exception { Thread [] threads = new Thread[100]; for (int i = 0; i < threads.length; i++) threads[i] = new Thread(new DataRace()); for (int i = 0; i < threads.length; i++) threads[i].start(); for (int i = 0; i < threads.length; i++) threads[i].join(); System.out.println(x); // x not always 0! } } Since we cannot synchronize on x (because it is primitive), the best solution I can think of is to create a new static object like static String lock = ""; and enclose the x++ and x-- within a synchronized block, locking on lock. But this seems really awkward. Is there a better way?

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• Unexpected start of already-primary server processes when heartbeat on secondary is stopped.

  - by vorik

  Hi, I've got an active-passive Heartbeat cluster with Apache, MySQL, ActiveMQ and DRBD. Today, I wanted to perform hardware-maintenance on the secondary node (node04), so I stopped the heartbeat service before shutting it down. Then, the primary node (node03) received a shutdown notice from the secondary node (node04). This logging comes from the primary node: node03 heartbeat[4458]: 2010/03/08_08:52:56 info: Received shutdown notice from 'node04.companydomain.nl'. heartbeat[4458]: 2010/03/08_08:52:56 info: Resources being acquired from node04.companydomain.nl. harc[27522]: 2010/03/08_08:52:56 info: Running /etc/ha.d/rc.d/status status heartbeat[27523]: 2010/03/08_08:52:56 info: Local Resource acquisition completed. mach_down[27567]: 2010/03/08_08:52:56 info: /usr/share/heartbeat/mach_down: nice_failback: foreign resources acquired mach_down[27567]: 2010/03/08_08:52:56 info: mach_down takeover complete for node node04.companydomain.nl. heartbeat[4458]: 2010/03/08_08:52:56 info: mach_down takeover complete. harc[27620]: 2010/03/08_08:52:56 info: Running /etc/ha.d/rc.d/ip-request-resp ip-request-resp ip-request-resp[27620]: 2010/03/08_08:52:56 received ip-request-resp drbddisk OK yes ResourceManager[27645]: 2010/03/08_08:52:56 info: Acquiring resource group: node03.companydomain.nl drbddisk Filesystem::/dev/drbd0::/data::ext3 mysql apache::/etc/httpd/conf/httpd.conf LVSSyncDaemonSwap::master monitor activemq tivoli-cluster MailTo::[email protected]::DRBDFailureDrisAcc MailTo::[email protected]::DRBDFailureDrisAcc 1.2.3.212 ResourceManager[27645]: 2010/03/08_08:52:56 info: Running /etc/ha.d/resource.d/drbddisk start Filesystem[27700]: 2010/03/08_08:52:57 INFO: Running OK ResourceManager[27645]: 2010/03/08_08:52:57 info: Running /etc/ha.d/resource.d/mysql start mysql[27783]: 2010/03/08_08:52:57 Starting MySQL[ OK ] apache[27853]: 2010/03/08_08:52:57 INFO: Running OK ResourceManager[27645]: 2010/03/08_08:52:57 info: Running /etc/ha.d/resource.d/monitor start monitor[28160]: 2010/03/08_08:52:58 ResourceManager[27645]: 2010/03/08_08:52:58 info: Running /etc/ha.d/resource.d/activemq start activemq[28210]: 2010/03/08_08:52:58 Starting ActiveMQ Broker... ActiveMQ Broker is already running. ResourceManager[27645]: 2010/03/08_08:52:58 ERROR: Return code 1 from /etc/ha.d/resource.d/activemq ResourceManager[27645]: 2010/03/08_08:52:58 CRIT: Giving up resources due to failure of activemq ResourceManager[27645]: 2010/03/08_08:52:58 info: Releasing resource group: node03.companydomain.nl drbddisk Filesystem::/dev/drbd0::/data::ext3 mysql apache::/etc/httpd/conf/httpd.conf LVSSyncDaemonSwap::master monitor activemq tivoli-cluster MailTo::[email protected]::DRBDFailureDrisAcc MailTo::[email protected]::DRBDFailureDrisAcc 1.2.3.212 ResourceManager[27645]: 2010/03/08_08:52:58 info: Running /etc/ha.d/resource.d/IPaddr 1.2.3.212 stop IPaddr[28329]: 2010/03/08_08:52:58 INFO: ifconfig eth0:0 down IPaddr[28312]: 2010/03/08_08:52:58 INFO: Success ResourceManager[27645]: 2010/03/08_08:52:58 info: Running /etc/ha.d/resource.d/MailTo [email protected] DRBDFailureDrisAcc stop MailTo[28378]: 2010/03/08_08:52:58 INFO: Success ResourceManager[27645]: 2010/03/08_08:52:58 info: Running /etc/ha.d/resource.d/MailTo [email protected] DRBDFailureDrisAcc stop MailTo[28433]: 2010/03/08_08:52:58 INFO: Success ResourceManager[27645]: 2010/03/08_08:52:58 info: Running /etc/ha.d/resource.d/tivoli-cluster stop ResourceManager[27645]: 2010/03/08_08:52:58 info: Running /etc/ha.d/resource.d/activemq stop activemq[28503]: 2010/03/08_08:53:01 Stopping ActiveMQ Broker... Stopped ActiveMQ Broker. ResourceManager[27645]: 2010/03/08_08:53:01 info: Running /etc/ha.d/resource.d/monitor stop monitor[28681]: 2010/03/08_08:53:01 ResourceManager[27645]: 2010/03/08_08:53:01 info: Running /etc/ha.d/resource.d/LVSSyncDaemonSwap master stop LVSSyncDaemonSwap[28714]: 2010/03/08_08:53:02 info: ipvs_syncmaster down LVSSyncDaemonSwap[28714]: 2010/03/08_08:53:02 info: ipvs_syncbackup up LVSSyncDaemonSwap[28714]: 2010/03/08_08:53:02 info: ipvs_syncmaster released ResourceManager[27645]: 2010/03/08_08:53:02 info: Running /etc/ha.d/resource.d/apache /etc/httpd/conf/httpd.conf stop apache[28782]: 2010/03/08_08:53:03 INFO: Killing apache PID 18390 apache[28782]: 2010/03/08_08:53:03 INFO: apache stopped. apache[28771]: 2010/03/08_08:53:03 INFO: Success ResourceManager[27645]: 2010/03/08_08:53:03 info: Running /etc/ha.d/resource.d/mysql stop mysql[28851]: 2010/03/08_08:53:24 Shutting down MySQL.....................[ OK ] ResourceManager[27645]: 2010/03/08_08:53:24 info: Running /etc/ha.d/resource.d/Filesystem /dev/drbd0 /data ext3 stop Filesystem[29010]: 2010/03/08_08:53:25 INFO: Running stop for /dev/drbd0 on /data Filesystem[29010]: 2010/03/08_08:53:25 INFO: Trying to unmount /data Filesystem[29010]: 2010/03/08_08:53:25 ERROR: Couldn't unmount /data; trying cleanup with SIGTERM Filesystem[29010]: 2010/03/08_08:53:25 INFO: Some processes on /data were signalled Filesystem[29010]: 2010/03/08_08:53:27 INFO: unmounted /data successfully Filesystem[28999]: 2010/03/08_08:53:27 INFO: Success ResourceManager[27645]: 2010/03/08_08:53:27 info: Running /etc/ha.d/resource.d/drbddisk stop heartbeat[4458]: 2010/03/08_08:53:29 WARN: node node04.companydomain.nl: is dead heartbeat[4458]: 2010/03/08_08:53:29 info: Dead node node04.companydomain.nl gave up resources. heartbeat[4458]: 2010/03/08_08:53:29 info: Link node04.companydomain.nl:eth0 dead. heartbeat[4458]: 2010/03/08_08:53:29 info: Link node04.companydomain.nl:eth1 dead. hb_standby[29193]: 2010/03/08_08:53:57 Going standby [foreign]. heartbeat[4458]: 2010/03/08_08:53:57 info: node03.companydomain.nl wants to go standby [foreign] Soo... What just happened here??? Heartbeat on node04 stopped and told node03, which was the active node at the time. Somehow, node03 decided to start the cluster processes that were already running. (For the processes that are not critical, I always return a 0 from the startupscript so it does not stops the entire cluster when a non-essential part fails.) When starting ActiveMQ, it returns status 1 because it is already running. This fails the node and shuts everything down. As heartbeat is not running on the secondary node, it cannot failover to there. When I tried to run ha_takeover to restart the resources, absolutely nothing happened. Only after I restarted heartbeat on the primary node the resources could be started (after a delay of 2 minutes). These are my questions: Why does heartbeat on the primary node try to start the cluster processes again? Why did ha_takeover not work? What can I do to prevent this from happening? Server configuration: DRBD: version: 8.3.7 (api:88/proto:86-91) GIT-hash: ea9e28dbff98e331a62bcbcc63a6135808fe2917 build by [email protected], 2010-01-20 09:14:48 0: cs:Connected ro:Secondary/Primary ds:UpToDate/UpToDate B r---- ns:0 nr:6459432 dw:6459432 dr:0 al:0 bm:301 lo:0 pe:0 ua:0 ap:0 ep:1 wo:d oos:0 uname -a Linux node04 2.6.18-164.11.1.el5 #1 SMP Wed Jan 6 13:26:04 EST 2010 x86_64 x86_64 x86_64 GNU/Linux haresources node03.companydomain.nl \ drbddisk \ Filesystem::/dev/drbd0::/data::ext3 \ mysql \ apache::/etc/httpd/conf/httpd.conf \ LVSSyncDaemonSwap::master \ monitor \ activemq \ tivoli-cluster \ MailTo::[email protected]::DRBDFailureDrisAcc \ MailTo::[email protected]::DRBDFailureDrisAcc \ 1.2.3.212 ha.cf debugfile /var/log/ha-debug logfile /var/log/ha-log keepalive 500ms deadtime 30 warntime 10 initdead 120 udpport 694 mcast eth0 225.0.0.3 694 1 0 mcast eth1 225.0.0.4 694 1 0 auto_failback off node node03.companydomain.nl node node04.companydomain.nl respawn hacluster /usr/lib64/heartbeat/dopd apiauth dopd gid=haclient uid=hacluster Thank you very much in advance, Ger Apeldoorn

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• tmux: Suddenly, cannot horizontally split

  - by A__A__0

  As root, using a reasonably default .profile and .shrc and an empty tmux.conf, I am unable to split the window horizontally. There are a number of cases to consider so I'll list them clearly. Using the keybinding + empty configuration: nothing happens Using the keybinding + my configuration: a bell is generated, nothing else; occasionally, the split will appear and disappear immediately (maybe it always does this, but I'm connecting over ssh so it may not make it through) Using tmux split-window -h with any config: tmux immediately exits I've posted here in order the server and client verbose logs generated by tmux -v during the third case: server started, pid 9523 socket path /tmp/tmux-0/default new client 7 got 100 from client 7 got 101 from client 7 got 102 from client 7 got 103 from client 7 got 104 from client 7 got 105 from client 7 got 105 from client 7 got 105 from client 7 got 105 from client 7 got 105 from client 7 got 105 from client 7 got 105 from client 7 got 105 from client 7 got 105 from client 7 got 105 from client 7 got 105 from client 7 got 105 from client 7 got 105 from client 7 got 105 from client 7 got 105 from client 7 got 105 from client 7 got 106 from client 7 got 200 from client 7 cmdq 0x801c6e080: new-session (client 7) new term: xterm xterm override: XT xterm override: Ms ]52;%p1%s;%p2%s xterm override: Cs ]12;%p1%s xterm override: Cr ]112 xterm override: Ss [%p1%d q xterm override: Se [2 q new key Oo: 0x1021 (KP/) new key Oj: 0x1022 (KP*) new key Om: 0x1023 (KP-) new key Ow: 0x1024 (KP7) new key Ox: 0x1025 (KP8) new key Oy: 0x1026 (KP9) new key Ok: 0x1027 (KP+) new key Ot: 0x1028 (KP4) new key Ou: 0x1029 (KP5) new key Ov: 0x102a (KP6) new key Oq: 0x102b (KP1) new key Or: 0x102c (KP2) new key Os: 0x102d (KP3) new key OM: 0x102e (KPEnter) new key Op: 0x102f (KP0) new key On: 0x1030 (KP.) new key OA: 0x101d (Up) new key OB: 0x101e (Down) new key OC: 0x1020 (Right) new key OD: 0x101f (Left) new key [A: 0x101d (Up) new key [B: 0x101e (Down) new key [C: 0x1020 (Right) new key [D: 0x101f (Left) new key OH: 0x1018 (Home) new key OF: 0x1019 (End) new key [H: 0x1018 (Home) new key [F: 0x1019 (End) new key Oa: 0x501d (C-Up) new key Ob: 0x501e (C-Down) new key Oc: 0x5020 (C-Right) new key Od: 0x501f (C-Left) new key [a: 0x901d (S-Up) new key [b: 0x901e (S-Down) new key [c: 0x9020 (S-Right) new key [d: 0x901f (S-Left) new key [11^: 0x5002 (C-F1) new key [12^: 0x5003 (C-F2) new key [13^: 0x5004 (C-F3) new key [14^: 0x5005 (C-F4) new key [15^: 0x5006 (C-F5) new key [17^: 0x5007 (C-F6) new key [18^: 0x5008 (C-F7) new key [19^: 0x5009 (C-F8) new key [20^: 0x500a (C-F9) new key [21^: 0x500b (C-F10) new key [23^: 0x500c (C-F11) new key [24^: 0x500d (C-F12) new key [25^: 0x500e (C-F13) new key [26^: 0x500f (C-F14) new key [28^: 0x5010 (C-F15) new key [29^: 0x5011 (C-F16) new key [31^: 0x5012 (C-F17) new key [32^: 0x5013 (C-F18) new key [33^: 0x5014 (C-F19) new key [34^: 0x5015 (C-F20) new key [2^: 0x5016 (C-IC) new key [3^: 0x5017 (C-DC) new key [7^: 0x5018 (C-Home) new key [8^: 0x5019 (C-End) new key [6^: 0x501a (C-NPage) new key [5^: 0x501b (C-PPage) new key [11$: 0x9002 (S-F1) new key [12$: 0x9003 (S-F2) new key [13$: 0x9004 (S-F3) new key [14$: 0x9005 (S-F4) new key [15$: 0x9006 (S-F5) new key [17$: 0x9007 (S-F6) new key [18$: 0x9008 (S-F7) new key [19$: 0x9009 (S-F8) new key [20$: 0x900a (S-F9) new key [21$: 0x900b (S-F10) new key [23$: 0x900c (S-F11) new key [24$: 0x900d (S-F12) new key [25$: 0x900e (S-F13) new key [26$: 0x900f (S-F14) new key [28$: 0x9010 (S-F15) new key [29$: 0x9011 (S-F16) new key [31$: 0x9012 (S-F17) new key [32$: 0x9013 (S-F18) new key [33$: 0x9014 (S-F19) new key [34$: 0x9015 (S-F20) new key [2$: 0x9016 (S-IC) new key [3$: 0x9017 (S-DC) new key [7$: 0x9018 (S-Home) new key [8$: 0x9019 (S-End) new key [6$: 0x901a (S-NPage) new key [5$: 0x901b (S-PPage) new key [11@: 0xd002 (C-S-F1) new key [12@: 0xd003 (C-S-F2) new key [13@: 0xd004 (C-S-F3) new key [14@: 0xd005 (C-S-F4) new key [15@: 0xd006 (C-S-F5) new key [17@: 0xd007 (C-S-F6) new key [18@: 0xd008 (C-S-F7) new key [19@: 0xd009 (C-S-F8) new key [20@: 0xd00a (C-S-F9) new key [21@: 0xd00b (C-S-F10) new key [23@: 0xd00c (C-S-F11) new key [24@: 0xd00d (C-S-F12) new key [25@: 0xd00e (C-S-F13) new key [26@: 0xd00f (C-S-F14) new key [28@: 0xd010 (C-S-F15) new key [29@: 0xd011 (C-S-F16) new key [31@: 0xd012 (C-S-F17) new key [32@: 0xd013 (C-S-F18) new key [33@: 0xd014 (C-S-F19) new key [34@: 0xd015 (C-S-F20) new key [2@: 0xd016 (C-S-IC) new key [3@: 0xd017 (C-S-DC) new key [7@: 0xd018 (C-S-Home) new key [8@: 0xd019 (C-S-End) new key [6@: 0xd01a (C-S-NPage) new key [5@: 0xd01b (C-S-PPage) new key [I: 0x1031 ((null)) new key [O: 0x1032 ((null)) new key OP: 0x1002 (F1) new key OQ: 0x1003 (F2) new key OR: 0x1004 (F3) new key OS: 0x1005 (F4) new key [15~: 0x1006 (F5) new key [17~: 0x1007 (F6) new key [18~: 0x1008 (F7) new key [19~: 0x1009 (F8) new key [20~: 0x100a (F9) new key [21~: 0x100b (F10) new key [23~: 0x100c (F11) new key [24~: 0x100d (F12) new key [2~: 0x1016 (IC) new key [3~: 0x1017 (DC) replacing key OH: 0x1018 (Home) replacing key OF: 0x1019 (End) new key [6~: 0x101a (NPage) new key [5~: 0x101b (PPage) new key [Z: 0x101c (BTab) replacing key OA: 0x101d (Up) replacing key OB: 0x101e (Down) replacing key OD: 0x101f (Left) replacing key OC: 0x1020 (Right) spawn: /bin/sh -- session 0 created writing 207 to client 7 got 208 from client 7 input_parse: '#' ground input_parse: ' ' ground keys are 7 ([?1;2c) received service class 1 complete key [?1;2c 0xfff keys are 1 (t) complete key t 0x74 input_parse: 't' ground keys are 1 (m) complete key m 0x6d input_parse: 'm' ground keys are 1 (u) complete key u 0x75 input_parse: 'u' ground keys are 1 (x) complete key x 0x78 input_parse: 'x' ground keys are 1 ( ) complete key 0x20 input_parse: ' ' ground keys are 1 (s) complete key s 0x73 input_parse: 's' ground keys are 1 (p) complete key p 0x70 input_parse: 'p' ground keys are 1 (l) complete key l 0x6c input_parse: 'l' ground keys are 1 (i) complete key i 0x69 input_parse: 'i' ground keys are 1 (t) complete key t 0x74 input_parse: 't' ground keys are 1 (-) complete key - 0x2d input_parse: '-' ground keys are 1 (d) complete key d 0x64 input_parse: 'd' ground keys are 1 () complete key 0x7f input_parse: '' ground input_c0_dispatch: ' input_parse: '' ground input_parse: '[' esc_enter input_parse: 'K' csi_enter input_csi_dispatch: 'K' "" "" keys are 1 (w) complete key w 0x77 input_parse: 'w' ground keys are 1 (i) complete key i 0x69 input_parse: 'i' ground keys are 1 (n) complete key n 0x6e input_parse: 'n' ground keys are 1 (d) complete key d 0x64 input_parse: 'd' ground keys are 1 (o) complete key o 0x6f input_parse: 'o' ground keys are 1 (w) complete key w 0x77 input_parse: 'w' ground keys are 1 ( ) complete key 0x20 input_parse: ' ' ground keys are 1 (-) complete key - 0x2d input_parse: '-' ground keys are 1 (h) complete key h 0x68 input_parse: 'h' ground keys are 1 ( ) complete key 0xd input_parse: ' ' ground input_c0_dispatch: ' input_parse: ' ' ground input_c0_dispatch: ' new client 13 got 100 from client 13 got 101 from client 13 got 102 from client 13 got 103 from client 13 got 104 from client 13 got 105 from client 13 got 105 from client 13 got 105 from client 13 got 105 from client 13 got 105 from client 13 got 105 from client 13 got 105 from client 13 got 105 from client 13 got 105 from client 13 got 105 from client 13 got 105 from client 13 got 105 from client 13 got 105 from client 13 got 105 from client 13 got 105 from client 13 got 105 from client 13 got 105 from client 13 got 105 from client 13 got 106 from client 13 got 200 from client 13 cmdq 0x801c6e160: split-window -h (client 13) spawn: /bin/sh -- writing 203 to client 13 input_parse: '#' ground input_parse: ' ' ground input_parse: '#' ground input_parse: ' ' ground lost client 13 session 0 destroyed writing 203 to client 7 got 205 from client 7 writing 204 to client 7 lost client 7 got 207 from server got 203 from server got 204 from server There are some other peculiarities: With a newly created user (from which I overwrote root's .profile and .shrc, tmux works perfectly. Occasionally (twice out of the 50 or so times I've tested it), the splitting will work fine once in a session. (This happened for example when I ran ktrace on tmux, which I can also post) To explain the 'suddenly' part of the title: when I started my newly updated mysql56-server, tmux immediately exited and lost the session. Recently I changed architectures, from FreeBSD 10.0 i386 to amd64, and I am still working through shared library incompatibilities. I suspect that this could be involved, but I can't imagine how an incompatibility of this sort could result in such a specific, isolated failure.

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• Add keyboard languages to XP, Vista, and Windows 7

  - by Matthew Guay

  Do you regularly need to type in multiple languages in Windows?  Here we’ll show you the easy way to add and change input languages to your keyboard in XP, Vista, and Windows 7. Windows Vista and 7 come preinstalled with support for viewing a wide variety of languages, so adding an input language is fairly simply.  Adding an input language is slightly more difficult in XP, and requires installing additional files if you need an Asian or Complex script language.  First we show how to add an input language in Windows Vista and 7; it’s basically the same in both versions.  Then, we show how to add a language to XP, and also how to add Complex Script support.  Please note that this is only for adding an input language, which will allow you to type in the language you select.  This does not change your user interface language. Change keyboard language in Windows 7 and Vista It is fairly simple to add or change a keyboard language in Windows 7 or Vista.  In Windows 7, enter “keyboard language” in the Start menu search box, and select “Change keyboards or other input methods”. In Windows Vista, open Control Panel and enter “input language” in the search box and select “Change keyboards or other input methods”.  This also works in Windows 7. Now, click Change Keyboards to add another keyboard language or change your default one. Our default input language is US English, and our default keyboard is the US keyboard layout.  Click Add to insert another input language while still leaving your default input language installed. Here we selected the standard Thai keyboard language (Thai Kedmanee), but you can select any language you want.  Windows offers almost any language you can imagine, so just look for the language you want, select it, and click Ok. Alternately, if you want, you can click Preview to see your layout choice before accepting it.  This is only the default characters, not ones that will be activated with Shift or other keys (many Asian languages use many more characters than English, and require the use of Shift and other keys to access them all).  Once your finished previewing, click close and then press Ok on the previous dialog. Now you will see both of your keyboard languages in the Installed services box.  You can click Add to go back and get more, or move your selected language up or down (to change its priority), or simply click Apply to add the new language. Also, you can now change the default input language from the top menu.  This is the language that your keyboard will start with when you boot your computer.  So, if you mainly use English but also use another language, usually it is best to leave English as your default input language. Once you’ve pressed Apply or Ok, you will see a new icon beside your system tray with the initials of your default input language. If you click it, you can switch between input languages.  Alternately you can switch input languages by pressing Alt+Shift on your keyboard. Some complex languages, such as Chinese, may have extra buttons to change input modes to accommodate their large alphabet. If you would like to change the keyboard shortcut for changing languages, go back to the Input Languages dialog, and select the “Advanced Key Settings” tab.  Here you can change settings for Caps Lock and change or add key sequences to change between languages. Also, the On-Screen keyboard will display the correct keyboard language (here the keyboard is displaying Thai), which can be a helpful reference if your physical keyboard doesn’t have your preferred input language printed on it.  To open this, simply enter “On-Screen keyboard” in the start menu search, or click All Programs>Accessories>On-Screen keyboard. Change keyboard language in Windows XP The process for changing the keyboard language in Windows XP is slightly different.  Open Control Panel, and select “Date, Time, Language, and Regional Options”.   Select “Add other languages”. Now, click Details to add another language.  XP does not include support for Asian and complex languages by default, so if you need to add one of those languages we have details for that below. Click Add to add an input language. Select your desired language from the list, and choose your desired keyboard layout if your language offers multiple layouts.  Here we selected Canadian French with the default layout. Now you will see both of your keyboard languages in the Installed services box.  You can click Add to go back and add more, or move your selected language up or down (to change its priority), or simply click Apply to add the new language. Once you’ve pressed Apply or Ok, you will see a new icon beside your system tray with the initials of your default input language. If you click it, you can switch between input languages.  Alternately you can switch input languages by pressing Alt+Shift on your keyboard. If you would like to change the keyboard shortcut for changing languages, go back to the Input Languages dialog, and click the “Key Settings” button on the bottom of the dialog.  Here you can change settings for Caps Lock and change or add key sequences to change between languages. Add support to XP for Asian and Complex script languages Windows XP does not include support for Asian and Complex script languages by default, but you can easily add them to your computer.  This is useful if you wish to type in one of these languages, or simply want to read text written in these languages, since XP will not display these languages correctly if they are not installed.  If you wish to install Chinese, Japanese, and/or Korean, check the “Install files for East Asian languages” box.  Or, if you need to install a complex script language (including Arabic, Armenian, Georgian, Hebrew, the Indic languages, Thai, and Vietnamese), check the “Install files for complex script and right-to-left languages” box.   Choosing either of these options will open a prompt reminding you that this option will take up more disk space.  Support for complex languages will require around 10Mb of hard drive space, but East Asian language support may require 230 Mb or more free disk space.  Click Ok, and click apply to install your language files. You may have to insert your XP CD into your CD drive to install these files.  Insert the disk, and then click Ok. Windows will automatically copy the files, including fonts for these languages… …and then will ask you to reboot your computer to finalize the settings.  Click Yes, and then reopen the “Add other languages” dialog when your computer is rebooted, and add a language as before.     Now you can add Complex and/or Asian languages to XP, just as above.  Here is the XP taskbar language selector with Thai installed. Conclusion Unfortunately we haven’t found a way to add Asian and complex languages in XP without having an XP disc. If you know of a way, let us know in the comments. (No downloading the XP disc from torrent site answers please) Adding an input language is very important for bilingual individuals, and can also be useful if you simply need to occasionally view Asian or Complex languages in XP.  And by following the correct instructions for your version of Windows, it should be very easy to add, change, and remove input languages. Similar Articles Productive Geek Tips Show Keyboard Shortcut Access Keys in Windows VistaKeyboard Ninja: 21 Keyboard Shortcut ArticlesAnother Desktop Cube for Windows XP/VistaThe "Up" Keyboard Shortcut for Windows 7 or Vista ExplorerWhat is ctfmon.exe And Why Is It Running? 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• Week in Geek: FBI Back Door in OpenBSD Edition

  - by Asian Angel

  This week we learned how to migrate bookmarks from Delicious to Diigo, fix annoying arrows, play old-school DOS games, schedule smart computer shutdowns, use breaks in Microsoft Word to better format documents, check the condition of hard-disks using Linux disk utilities, & what the Linux fstab is and how it works. Photo by Jameson42. Random Geek Links Another week with extra news link goodness to help keep you up to date. Photo by justmakeit. Report of FBI back door roils OpenBSD community Allegations that the FBI surreptitiously placed a back door into the OpenBSD operating system have alarmed the computer security community, prompting calls for an audit of the source code and claims that the charges must be a hoax. Fortinet: Job outlook improving for cybercrooks In an ironic twist in the job market, more positions will open up for developers who can write customized malware packers, people who can break CAPTCHA codes, and distributors who can spread malicious code, according to Fortinet. Enisa: Malware for smartphones is a ’serious risk’ Businesses and consumers are at risk of data breaches through smartphone use, according to the European Network and Information Security Agency. The trick with the f: Google and Microsoft web sites distribute malware Last week, Google’s DoubleClick advertising platform and Microsoft’s rad.msn.com online ad network briefly distributed malware to other web sites in the form of advertising banners. New scam tactic: Fake disk defraggers It would appear that scammers are trying out new programs to see which might best confuse potential victims and evade detection by legitimate antivirus software. Microsoft closes IE and Stuxnet holes As previously announced, Microsoft has released 17 security updates to close 40 security holes. All four Windows holes so far disclosed in connection with Stuxnet have now been closed. Microsoft Offers H.264 Support to Firefox on Windows via Add-On The new HTML5 Extension for Windows Media Player Firefox Plug-in add-on from Microsoft offers users that are running Firefox on Windows 7 H.264 support for HTML5 video playback. Google proclaims Chrome business-ready Google has announced that Chrome is ready for corporate use. Microsoft Tells Exchange Customers to Think Twice Before Opting for Google Message Continuity This week, Microsoft is telling companies still running Exchange 2010’s precursors that they should carefully consider the implications of embracing Google Message Continuity. Who Google has in mind for its Chrome OS users Steven Vaughan-Nichols explains why he feels that Chrome OS will be ideal for either office-workers or people who need a computer, but do not know the first thing about how to use one safely. Oracle takes office suite to the cloud Oracle has introduced Cloud Office 1.0, a cloud-based version of its office suite, which is aimed at web and mobile users. Mozilla pays premiums for reports of vulnerabilities The Mozilla Foundation has followed Google’s example by expanding its rewards program for reports of vulnerabilities in its Web applications. Who bought those 882 Novell patents? Not just Microsoft The mysterious CPTN Holdings — the organization that bought the 882 Novell patents as part of the terms of the Attachmate acquisition of Novell – has been unmasked (Microsoft, Apple, EMC and Oracle). Appeals court: Feds need warrants for e-mail Police must obtain search warrants before perusing Internet users’ e-mail records, a federal appeals court ruled today in a landmark decision that struck down part of a 1986 law allowing warrantless access. Geek Video of the Week What happens when someone plays a wicked prank by shoveling crazy snow paths that lead to dead ends or turn back on themselves? Watch to find out! Photo by CollegeHumor. Janitor Snow Shoveling Prank Random TinyHacker Links The Oatmeal on Cat vs Internet What lengths will our poor neglected kitty hero have to go to in order to get some attention? Guide On Using JoliCloud With Windows JoliCloud is a nifty operating system that’s made for people who need a light-weight OS that’s mostly cloud based. Check this guide on using it with Windows. Use Cameyo to Easily Create Portable Programs Here’s a nifty tool to make portable apps out of programs in Windows. Check out the guide to do it. Better Family Tech Support A nice new site by Google to help members of family understand how computers work. Track Your Stolen Mobile Phone With F-Secure A useful anti-theft tool for your mobile phone. Super User Questions Another week with great answers to popular questions from Super User. What Chrome password manager fits my requirements? What’s the best way to be able to reimage windows computers? Could you suggest feature-rich disk-based personal backup program for linux (and I’ve seen a few)? What is IPv6 and why should I care? Is there any way to find out what programs are trying to connect to Internet on windows? How-To Geek Weekly Article Recap Here are our hottest articles full of geeky goodness from this past week at HTG. 20 OS X Keyboard Shortcuts You Might Not Know Microsoft Security Essentials 2.0 Kills Viruses Dead. Download It Now. Is Your Desktop Printer More Expensive Than Printing Services? Ask the Readers: Would You Be Willing to Give Windows Up and Use a Different O.S.? The Twelve Days of Geekmas One Year Ago on How-To Geek Enjoy reading through our latest batch of retro-geek goodness from one year ago. Macrium Reflect is a Free and Easy To Use Backup Utility How To Turn a Physical Computer Into A Virtual Machine with Disk2vhd How To Restore Windows 7 from a System Image How To Manage Hard Drive Space Used by Windows 7 Backup and Restore How To Manage Hibernate Mode in Windows 7 The Geek Note That is all we have for you this week, so see you back here again after the holidays! Got a great tip? Send it in to us at [email protected]. Photo by mitjamavsar. Latest Features How-To Geek ETC The Complete List of iPad Tips, Tricks, and Tutorials The 50 Best Registry Hacks that Make Windows Better The How-To Geek Holiday Gift Guide (Geeky Stuff We Like) LCD? LED? Plasma? The How-To Geek Guide to HDTV Technology The How-To Geek Guide to Learning Photoshop, Part 8: Filters Improve Digital Photography by Calibrating Your Monitor Deathwing the Destroyer – WoW Cataclysm Dragon Wallpaper Drag2Up Lets You Drag and Drop Files to the Web With Ease The Spam Police Parts 1 and 2 – Goodbye Spammers [Videos] Snow Angels Theme for Windows 7 Exploring the Jungle Ruins Wallpaper Protect Your Privacy When Browsing with Chrome and Iron Browser

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