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  • Static lock in Python?

    - by roddik
    Hello. I've got the following code: import time import threading class BaseWrapper: #static class lock = threading.Lock() @staticmethod def synchronized_def(): BaseWrapper.lock.acquire() time.sleep(5) BaseWrapper.lock.release() def test(): print time.ctime() if __name__ is '__main__': for i in xrange(10): threading.Thread(target = test).start() I want to have a method synchronized using static lock. However the above code prints the same time ten times, so it isn't really locking. How can I fix it? TIA

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  • Determine modifier key state without an InputEvent object in Java

    - by heycam
    I need to determine the current state of the Shift key, but at the time I need the state I don't have an InputEvent object around. I need something like java.awt.Toolkit.getLockingKeyState(int) that works for Shift, not just the locking keys like VK_CAPS_LOCK. Is there a way I can do this without listening to input events and storing the for later when I need to check the state? Thanks!

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  • Django: How can I protect against concurrent modification of data base entries

    - by Ber
    If there a way to protect against concurrent modifications of the same data base entry by two or more users? It would be acceptable to show an error message to the user performing the second commit/save operation, but data should not be silently overwritten. I think locking the entry is not an option, as a user might use the "Back" button or simply close his browser, leaving the lock for ever.

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  • select for update with ruby oci8

    - by ash34
    how do I do a 'select for update' and then 'update' the row using ruby oci8. I have two fields counter1 and counter2 in a table which has only 1 record. I want to select the values from this table and then increment them by locking the row using select for update. thanks.

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  • Client server architecture question

    - by Shane Fulmer
    I am working on a client server system, and am running into issues where multiple clients are executing an action at the same time. We are able to solve this by locking on the critical section of code, which ensures that the first client will complete the action before the second client enters the code block. My question is this: our server is also clustered, so multiple instances of the server itself can exist, which recreates the same problem as before. How could we solve this problem? Thanks!

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  • compare windows server for patch/update/hotfix installs

    - by user12002221
    Are there any tools that can be used to connect to windows 2008 servers, and get a comparison of the installed patches/updates on the servers, showing what is installed on one and not on the other? This is to help isolate an issue we are seeing on a specific windows server, in a load balanced setup. There is a certain performance/locking issue, which is mitigated whenever one of the servers is disabled. Please share, if you have any suggestions. Thanks in advance!

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  • DOM Storage and locks

    - by user535759
    Since DOM storage and its equivalencies persist in between tabs and windows, I've thought about using it for message passing. The problem is that fetch and store are different operations, and therefore not atomic. I have models that rely on UUID generation, conflict resolutions, and beaconing to do the small subset of what I need to do, but my real question is this: Since the local storage is a shared memory resource, what are the locking mechanisms available for mutual access?

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  • application blocking

    - by pradeep
    I have a application which runs over browser ...php application... i need to lock this application to only few machines and laptops that we allow to access. IP locking cannot be done as laptops can be on wifi from outside... Any Idea on how to do this?

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  • Hibernate's version values in Grails app

    - by xain
    I'm looking at a database dump file, and I see many records in various tables with their version number set in values other than 0 (even 94 in one case). I understand it has to do with hibernate locking strategy, but my concern is that today is Sunday, and the site has almost no visitors so is: is this normal ? Or is there a known hibernate bug or even some programming malpractice producing this ?

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  • c# Unable to open file for reading

    - by Maks
    I'm writing a program that uses FileSystemWatcher to monitor changes to a given directory, and when it recieves OnCreated or OnChanged event, it copies those created/changed files to a specified directorie(s). At first I had problems with the fact that OnChanged/OnCreated events can be sent twice (not acceptable in case it needed to process 500MB file) but I made a way around this and with what I'm REALLY STUCKED with is getting the following IOException: The process cannot access the file 'C:\Where are Photos\bookmarks (11).html' because it is being used by another process. Thus, preventing the program from copying all the files it should. So as I mentioned, when user uses this program he/she specifes monitored directory, when user copies/creates/changes file in that directory, program should get OnCreated/OnChanged event and then copy that file to few other directories. Above error happens in all casess, if user copies few files that needs to owerwrite other ones in folder being monitored or when copying bulk of several files or even sometimes when copying one file in a monitored directory. Whole program is quite big so I'm sending the most important parts. OnCreated: private void OnCreated(object source, FileSystemEventArgs e) { AddLogEntry(e.FullPath, "created", ""); // Update last access data if it's file so the same file doesn't // get processed twice because of sending another event. if (fileType(e.FullPath) == 2) { lastPath = e.FullPath; lastTime = DateTime.Now; } // serves no purpose now, it will be remove soon string fileName = GetFileName(e.FullPath); // copies file from source to few other directories Copy(e.FullPath, fileName); Console.WriteLine("OnCreated: " + e.FullPath); } OnChanged: private void OnChanged(object source, FileSystemEventArgs e) { // is it directory if (fileType(e.FullPath) == 1) return; // don't mind directory changes itself // Only if enough time has passed or if it's some other file // because two events can be generated int timeDiff = ((TimeSpan)(DateTime.Now - lastTime)).Seconds; if ((timeDiff < minSecsDiff) && (e.FullPath.Equals(lastPath))) { Console.WriteLine("-- skipped -- {0}, timediff: {1}", e.FullPath, timeDiff); return; } // Update last access data for above to work lastPath = e.FullPath; lastTime = DateTime.Now; // Only if size is changed, the rest will handle other handlers if (e.ChangeType == WatcherChangeTypes.Changed) { AddLogEntry(e.FullPath, "changed", ""); string fileName = GetFileName(e.FullPath); Copy(e.FullPath, fileName); Console.WriteLine("OnChanged: " + e.FullPath); } } fileType: private int fileType(string path) { if (Directory.Exists(path)) return 1; // directory else if (File.Exists(path)) return 2; // file else return 0; } Copy: private void Copy(string srcPath, string fileName) { foreach (string dstDirectoy in paths) { string eventType = "copied"; string error = "noerror"; string path = ""; string dirPortion = ""; // in case directory needs to be made if (srcPath.Length > fsw.Path.Length) { path = srcPath.Substring(fsw.Path.Length, srcPath.Length - fsw.Path.Length); int pos = path.LastIndexOf('\\'); if (pos != -1) dirPortion = path.Substring(0, pos); } if (fileType(srcPath) == 1) { try { Directory.CreateDirectory(dstDirectoy + path); //Directory.CreateDirectory(dstDirectoy + fileName); eventType = "created"; } catch (IOException e) { eventType = "error"; error = e.Message; } } else { try { if (!overwriteFile && File.Exists(dstDirectoy + path)) continue; // create new dir anyway even if it exists just to be sure Directory.CreateDirectory(dstDirectoy + dirPortion); // copy file from where event occured to all specified directories using (FileStream fsin = new FileStream(srcPath, FileMode.Open, FileAccess.Read, FileShare.Read)) { using (FileStream fsout = new FileStream(dstDirectoy + path, FileMode.Create, FileAccess.Write)) { byte[] buffer = new byte[32768]; int bytesRead = -1; while ((bytesRead = fsin.Read(buffer, 0, buffer.Length)) > 0) fsout.Write(buffer, 0, bytesRead); } } } catch (Exception e) { if ((e is IOException) && (overwriteFile == false)) { eventType = "skipped"; } else { eventType = "error"; error = e.Message; // attempt to find and kill the process locking the file. // failed, miserably System.Diagnostics.Process tool = new System.Diagnostics.Process(); tool.StartInfo.FileName = "handle.exe"; tool.StartInfo.Arguments = "\"" + srcPath + "\""; tool.StartInfo.UseShellExecute = false; tool.StartInfo.RedirectStandardOutput = true; tool.Start(); tool.WaitForExit(); string outputTool = tool.StandardOutput.ReadToEnd(); string matchPattern = @"(?<=\s+pid:\s+)\b(\d+)\b(?=\s+)"; foreach (Match match in Regex.Matches(outputTool, matchPattern)) { System.Diagnostics.Process.GetProcessById(int.Parse(match.Value)).Kill(); } Console.WriteLine("ERROR: {0}: [ {1} ]", e.Message, srcPath); } } } AddLogEntry(dstDirectoy + path, eventType, error); } } I checked everywhere in my program and whenever I use some file I use it in using block so even writing event to log (class for what I ommited since there is probably too much code already in post) wont lock the file, that is it shouldn't since all operations are using using statement block. I simply have no clue who's locking the file if not my program "copy" process from user through Windows or something else. Right now I have two possible "solutions" (I can't say they are clean solutions since they are hacks and as such not desireable). Since probably the problem is with fileType method (what else could lock the file?) I tried changing it to this, to simulate "blocking-until-ready-to-open" operation: fileType: private int fileType(string path) { FileStream fs = null; int ret = 0; bool run = true; if (Directory.Exists(path)) ret = 1; else { while (run) { try { fs = new FileStream(path, FileMode.Open); ret = 2; run = false; } catch (IOException) { } finally { if (fs != null) { fs.Close(); fs.Dispose(); } } } } return ret; } This is working as much as I could tell (test), but... it's hack, not to mention other deficients. The other "solution" I could try (I didn't test it yet) is using GC.Collect() somewhere at the end of fileType() method. Maybe even worse "solution" than previous one. Can someone pleas tell me, what on earth is locking the file, preventing it from opening and how can I fix that? What am I missing to see? Thanks in advance.

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  • Thread safety in C# arrays

    - by Betamoo
    Does having 2 different threads : one reading from a C# array (e.g from first location), and another one writing to the same C# array but to a different location(e.g to the last location) is thread safe or not? (And I mean here without locking reading nor writing)

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  • even small file upload stops activity on apache/rails

    - by Pavel K.
    on my rails(2.3.5) app(currently 50-70rpm, maximum response time around 0.7s), uploading even 700k file(using paperclip plugin) locks up the server for web requests for everyone for 2 minutes! (other apps on same server work normally) does anyone have a clue why that might be happening? i am using some mysql transactions which lock the database also if that might be an issue i read http://www.therailsway.com/2009/4/23/uploading-files but it couldn't be locking server for 2 minutes for a small file, could it?!

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  • Another Synergy issue: screen lock on Windows Server 2003

    - by pmr
    I have set up Synergy on Unix systems with no problems, however when I set up a Synergy server on a Windows Server 2003 box using I get an error message that the mouse cursor is locked when trying to move to the client system. I use a Microsoft Natural keyboard in case that matters (seems Scroll Lock might be involved). Does anyone have experience with using Synergy on Windows systems that have reported mouse screen locking in the log when unable to mouse over to a client system?

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  • VB.net SyncLock Object

    - by Budius
    I always seen on SyncLock examples people using Private Lock1 As New Object ' declaration SyncLock Lock1 ' usage but why? In my specific case I'm locking a Queue to avoid problems on mult-threading Enqueueing and Dequeueing my data. Can I lock the Queue object itself, like this? Private cmdQueue As New Queue(Of QueueItem) ' declaration SyncLock cmdQueue ' usage Any help appreciated. Thanks.

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  • Unlock device, display a text, then lock again

    - by Waza_Be
    For the need of my application, I need to display a message on the screen even if the lockscreen is enabled, then wait 3 seconds, than I have to lock again the phone as I don't want it to make unwanted phone calls in your pockets. First part is easy: if (PreferenceManager.getDefaultSharedPreferences( getBaseContext()).getBoolean("wake", false)) { KeyguardManager kgm = (KeyguardManager) getSystemService(Context.KEYGUARD_SERVICE); boolean isKeyguardUp = kgm.inKeyguardRestrictedInputMode(); WakeLocker.acquire(ProtoBenService.this); Intent myIntent = new Intent(ProtoBenService.this,LockActivity.class); myIntent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK); if (isKeyguardUp) { ProtoBenService.this.startActivity(myIntent); } else Toast.makeText(ProtoBenService.this.getBaseContext(), intention, Toast.LENGTH_LONG).show(); WakeLocker.release(); } With this class: public abstract class WakeLocker { private static PowerManager.WakeLock wakeLock; public static void acquire(Context ctx) { if (wakeLock != null) wakeLock.release(); PowerManager pm = (PowerManager) ctx.getSystemService(Context.POWER_SERVICE); wakeLock = pm.newWakeLock(PowerManager.FULL_WAKE_LOCK | PowerManager.ACQUIRE_CAUSES_WAKEUP | PowerManager.ON_AFTER_RELEASE, "CobeIm"); wakeLock.acquire(); } public static void release() { if (wakeLock != null) wakeLock.release(); wakeLock = null; } } And the Activity: public class LockActivity extends Activity { @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); Window window = getWindow(); window.addFlags(WindowManager.LayoutParams.FLAG_DISMISS_KEYGUARD); window.addFlags(WindowManager.LayoutParams.FLAG_TURN_SCREEN_ON); window.addFlags(WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON); TextView tv = new TextView(this); tv.setText("This is working!"); tv.setTextSize(45); setContentView(tv); Runnable mRunnable; Handler mHandler = new Handler(); mRunnable = new Runnable() { @Override public void run() { LockActivity.this.finish(); } }; mHandler.postDelayed(mRunnable, 3 * 1000); } } So, this is nice, the phone can display my text! The only problem comes when I want to lock again the phone, it seems that locking the phone is protected by the system... Programmatically turning off the screen and locking the phone how to lock the android programatically I think that my users won't understand the Device Admin and won't be able to activate it. Is there any workaround to lock the screen without the Device Admin stuff?

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  • Hiernate's version values in Grails app

    - by xain
    Hi, looking at a database dump file, and I see many records in various tables with their version number set in values other than 0 (even 94 in one case). I understand it has to do with hibernate locking strategy, but my concern is that today is Sunday, and the site has almost no visitors so is: is this normal ? Or is there a known hibernate bug or even some programming malpractice producing this ? Thanks in advance.

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  • SQL Server stored procedure in multi threaded environments

    - by Shamika
    Hi, I need to execute some Sql server stored procs in a thread safe manner. At the moment I'm using software locks (C# locks) to achieve this but wonder what kind of features provided by the Sql server itself to achieve thread safety. It seems to be there are some table and row locking features built in to Sql server. Also from a performance perspective what is best approach? Software locks? Or Sql Server built in locks? Thanks, Shamika

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  • Table in DB for generating primary keys?

    - by Sapphire
    Do you ever use a separate table for "generating" artificial primary keys for DB (and why)? What I mean is to have a table with two columns, table name and current ID - with which you could get new "ID" for some table by simply locking the row with that table name, getting the current value of the key, increment it by one, and unlock the row. Why would you prefer this over standard integer identity column? P.S. The "idea" is from Fowlers Patterns of Enterprise Application Architecture, btw...

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  • How do I read and write to a file using threads in java?

    - by WarmWaffles
    I'm writing an application where I need to read blocks in from a single file, each block is roughly 512 bytes. I am also needing to write blocks simultaneously. One of the ideas I had was BlockReader implements Runnable and BlockWriter implements Runnable and BlockManager manages both the reader and writer. The problem that I am seeing with most examples that I have found was locking problems and potential deadlock situations. Any ideas how to implement this?

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  • Please suggest good book/website to for Threads and Concurrency?

    - by learner
    I have gone through Head First Java and some other sites but I couldn't find complete stuff related to Threads and additional concurrency packages at one place. Please suggest a book/website which covers complete Threads with more details like Synchronize and locking of objects More detailed about volatile Visibility issues in Threads java.util.concurrent package java.util.concurrent.atomic package

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  • Thread-safe get (accessor method)

    - by sonofdelphi
    I'm currently using the following code for thread-safe access of a variable. int gnVariable; void getVariableValue(int *pnValue) { acquireLock(); //Acquires the protection mechanism *pnValue = gnVariable; releaseLock(); //Releasing the protection mechanism } I would like to change my API signature to a more user-friendly int getVariableValue(void); How should I rewrite the function - such that the users of the API don't have to bother about the locking/unlocking details?

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