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• Deploying an EAR to JBOSS times out (org.rhq.core.pc.inventory.TimeoutException:)

  - by rangalo

  Hi, I am trying to deploy an ear file to JBOSS AS (defalut server). The application is the mavenised version of examples of SeamInAction book. When I copy the file to $JBOSS_HOME/server/default/deploy, I don't get any exception but the application doesn't respond, after some time trying to access the application from the browser gives following in the log... While deploying with admin-console (http://localhost:8080/admin-console) I get following error messgae: PS: After this Jboss gets into unusable state. I cannot even access admin-console. I just have to kill it. ErrorMessage in admin-console: Failed to create Resource Open18.ear - cause: org.rhq.core.pc.inventory.TimeoutException: Call to [org.rhq.plugins.jbossas5.ApplicationServerComponent.createResource()] with args [[CreateResourceReport: ResourceType=[ResourceType[id=0, category=Service, name=Enterprise Application (EAR), plugin=JBossAS5]], ResourceKey=[null]]] timed out. Invocation thread will be interrupted at org.rhq.core.pc.inventory.ResourceContainer$ResourceComponentInvocationHandler.invokeInNewThreadWithLock(ResourceContainer.java:437) at org.rhq.core.pc.inventory.ResourceContainer$ResourceComponentInvocationHandler.invoke(ResourceContainer.java:406) at $Proxy266.createResource(Unknown Source) at org.rhq.core.pc.inventory.CreateResourceRunner.call(CreateResourceRunner.java:113) at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:303) at java.util.concurrent.FutureTask.run(FutureTask.java:138) at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908) at java.lang.Thread.run(Thread.java:619) Error Logs: 4:08:58,555 INFO [TableMetadata] foreign keys: [fkaf42e01ba13c3380, fk_course_ref_facility] 14:08:58,555 INFO [TableMetadata] indexes: [course_pkey] 14:08:58,645 INFO [TableMetadata] table found: public.facility 14:08:58,645 INFO [TableMetadata] columns: [zip, phone, state, type, uri, city, country, id, price_range, address, county, description, nam e] 14:08:58,645 INFO [TableMetadata] foreign keys: [] 14:08:58,645 INFO [TableMetadata] indexes: [facility_pkey] 14:08:58,705 INFO [TableMetadata] table found: public.hole 14:08:58,705 INFO [TableMetadata] columns: [id, m_par, l_handicap, name, l_par, number, course_id, m_handicap] 14:08:58,705 INFO [TableMetadata] foreign keys: [fk_hole_ref_course, fk30f4c09c3f1200] 14:08:58,705 INFO [TableMetadata] indexes: [hole_pkey, uniq_hole_number] 14:08:58,764 INFO [TableMetadata] table found: public.tee 14:08:58,764 INFO [TableMetadata] columns: [hole_id, distance, tee_set_id] 14:08:58,764 INFO [TableMetadata] foreign keys: [fk1c014f8de7677, fk_tee_ref_hole, fk1c014c69de560, fk_tee_ref_tee_set] 14:08:58,764 INFO [TableMetadata] indexes: [tee_pkey] 14:08:58,826 INFO [TableMetadata] table found: public.tee_set 14:08:58,826 INFO [TableMetadata] columns: [id, color, m_slope_rating, l_slope_rating, name, course_id, m_course_rating, l_course_rating, p os] 14:08:58,826 INFO [TableMetadata] foreign keys: [fk_tee_set_ref_course, fkaa6881b79c3f1200] 14:08:58,826 INFO [TableMetadata] indexes: [tee_set_pkey, uniq_tee_set_pos, uniq_tee_set_color] 14:08:58,827 INFO [SchemaUpdate] schema update complete 14:08:58,829 INFO [NamingHelper] JNDI InitialContext properties:{java.naming.factory.initial=org.jnp.interfaces.NamingContextFactory, java. naming.factory.url.pkgs=org.jboss.naming:org.jnp.interfaces} 14:08:58,850 INFO [TomcatDeployment] deploy, ctxPath=/Open18 14:15:53,969 WARN [DiscoveryComponentProxyFactory] The discovery component for resource type [ResourceType[id=0, category=Service, name=Connector, plugin=JBossAS5]] has been blacklisted 14:15:53,970 WARN [InventoryManager] Failure during discovery for [Connector] Resources - failed after 300002 ms. org.rhq.core.pc.inventory.TimeoutException: Call to [org.rhq.plugins.jbossas5.ConnectorDiscoveryComponent.discoverResources()] with args [[org.rhq.core.pluginapi.inventory.ResourceDiscoveryContext@96db1]] timed out. Invocation thread will be interrupted at org.rhq.core.pc.util.DiscoveryComponentProxyFactory$ResourceDiscoveryComponentInvocationHandler.invokeInNewThread(DiscoveryComponentProxyFactory.java:208) at org.rhq.core.pc.util.DiscoveryComponentProxyFactory$ResourceDiscoveryComponentInvocationHandler.invoke(DiscoveryComponentProxyFactory.java:181) at $Proxy249.discoverResources(Unknown Source) at org.rhq.core.pc.inventory.InventoryManager.invokeDiscoveryComponent(InventoryManager.java:272) at org.rhq.core.pc.inventory.InventoryManager.executeComponentDiscovery(InventoryManager.java:1697) at org.rhq.core.pc.inventory.RuntimeDiscoveryExecutor.discoverForResource(RuntimeDiscoveryExecutor.java:218) at org.rhq.core.pc.inventory.RuntimeDiscoveryExecutor.discoverForResource(RuntimeDiscoveryExecutor.java:234) at org.rhq.core.pc.inventory.RuntimeDiscoveryExecutor.runtimeDiscover(RuntimeDiscoveryExecutor.java:134) at org.rhq.core.pc.inventory.RuntimeDiscoveryExecutor.call(RuntimeDiscoveryExecutor.java:94) at org.rhq.core.pc.inventory.RuntimeDiscoveryExecutor.call(RuntimeDiscoveryExecutor.java:51) at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:303) at java.util.concurrent.FutureTask.run(FutureTask.java:138) at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$301(ScheduledThreadPoolExecutor.java:98) at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:207) at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908) at java.lang.Thread.run(Thread.java:619) 14:15:53,981 WARN [NavigationContent] Unable to find node for deleted resource [Resource[id=-5, type=Connector, key=ajp://127.0.0.1:8009, name=ajp://127.0.0.1:8009, parent=JBoss Web]].

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• [C++] Producer/Consumer Implementation -- Feedback Wanted

  - by bobber205

  I'm preparing for an interview in a few weeks and I thougth I would give threads in boost a go, as well as do the simple producer/consumer problem I learned in school. Haven't done it quite awhile so I was curious what you guys think of this? What should I add to make it a better example etc. Thanks for the feedback! :) ////////////////////////////////////////////////////////////////////////// boost::mutex bufferMutex; deque<int> buffer; const int maxBufferSize = 5; ////////////////////////////////////////////////////////////////////////// bool AddToBuffer(int i) { if (buffer.size() < maxBufferSize) { buffer.push_back(i); return true; } else { return false; } } bool GetFromBuffer(int& toReturn) { if (buffer.size() == 0) { return false; } else { toReturn = buffer[buffer.size()-1]; buffer.pop_back(); return true; } } struct Producer { int ID; void operator()() { while (true) { boost::mutex::scoped_lock lock(bufferMutex); int num = dice(); bool result = AddToBuffer(num); lock.unlock(); //safe area done if (result) { cout << "Producer " << this->ID << " Added " << num << endl; } else { cout << "!!Buffer was Full!!" << endl; } //Added //Now wait boost::xtime xt; xtime_get( &xt, boost::TIME_UTC); xt.nsec += 1000000 + 100000 * (rand() % 1000); boost::thread::sleep(xt); } } }; struct Consumer { int ID; void operator()() { while (true) { int returnedInt = 0; boost::mutex::scoped_lock lock(bufferMutex); bool result = GetFromBuffer(returnedInt); lock.unlock(); //safe area done if (result) { cout << "\tConsumer " << this->ID << " Took Out " << returnedInt << endl; } else { cout << "!!Buffer was Empty!!" << endl; } //Added //Now wait boost::xtime xt; xtime_get( &xt, boost::TIME_UTC); xt.nsec += 1000000 + 100000 * (rand() % 1000); boost::thread::sleep(xt); } } }; void main() { Producer p, p2; Consumer c, c2; p.ID = 1; p2.ID = 2; c.ID = 1; c2.ID = 2; boost::thread thread1(boost::ref(p)); boost::thread thread2(boost::ref(c)); boost::thread thread3(boost::ref(p2)); boost::thread thread4(boost::ref(c2)); int x; cin >> x; }

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• Generate JFreeChart in servlet

  - by San4o

  I'm trying to generate graphs using JFreeChart. I added record in web.xml, installed jfreechart library. Compiled servlet. Below code of servlet has shown: import java.io.IOException; import java.io.OutputStream; import java.io.File; import javax.servlet.*; import javax.servlet.http.*; import java.awt.Color; import org.jfree.chart.ChartFactory; import org.jfree.chart.ChartUtilities; import org.jfree.chart.JFreeChart; import org.jfree.data.general.DefaultPieDataset; public class diagram extends HttpServlet { public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { doTestPieChart(request,response); } protected void doTestPieChart(HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException { OutputStream out = response.getOutputStream(); try { DefaultPieDataset dataset = new DefaultPieDataset(); dataset.setValue("Graphic Novels", 192); dataset.setValue("History", 125); dataset.setValue("Military Fiction", 236); dataset.setValue("Mystery", 547); dataset.setValue("Performing Arts", 210); dataset.setValue("Science, Non-Fiction", 70); dataset.setValue("Science Fiction", 989); JFreeChart chart = ChartFactory.createPieChart( "Books by Type", dataset, true, false, false ); chart.setBackgroundPaint(Color.white); response.setContentType("image/png"); ChartUtilities.writeChartAsPNG(out, chart, 400, 300); /* ServletContext sc = getServletContext(); String filename = sc.getRealPath("pie.png"); File file = new File(filename); ChartUtilities.saveChartAsPNG(file,chart,400,300); */ } catch (Exception e) { System.out.println(e.toString()); } finally { out.close(); } } } When i launch the servlet, mistake has shown : HTTP Status 500 - type Exception report message description The server encountered an internal error () that prevented it from fulfilling this request. exception javax.servlet.ServletException: Error instantiating servlet class diagram org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102) org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:298) org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:852) org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:588) org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:489) java.lang.Thread.run(Thread.java:619) root cause java.lang.NoClassDefFoundError: org/jfree/data/general/PieDataset java.lang.Class.getDeclaredConstructors0(Native Method) java.lang.Class.privateGetDeclaredConstructors(Class.java:2389) java.lang.Class.getConstructor0(Class.java:2699) java.lang.Class.newInstance0(Class.java:326) java.lang.Class.newInstance(Class.java:308) org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102) org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:298) org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:852) org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:588) org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:489) java.lang.Thread.run(Thread.java:619) root cause java.lang.ClassNotFoundException: org.jfree.data.general.PieDataset org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1484) org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1329) java.lang.ClassLoader.loadClassInternal(ClassLoader.java:316) java.lang.Class.getDeclaredConstructors0(Native Method) java.lang.Class.privateGetDeclaredConstructors(Class.java:2389) java.lang.Class.getConstructor0(Class.java:2699) java.lang.Class.newInstance0(Class.java:326) java.lang.Class.newInstance(Class.java:308) org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102) org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:298) org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:852) org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:588) org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:489) java.lang.Thread.run(Thread.java:619) note The full stack trace of the root cause is available in the Apache Tomcat/6.0.24 logs. Help me to solve a problem. and where is problem?

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• CPU Affinity Masks (Putting Threads on different CPUs)

  - by hahuang65

  I have 4 threads, and I am trying to set thread 1 to run on CPU 1, thread 2 on CPU 2, etc. However, when I run my code below, the affinity masks are returning the correct values, but when I do a sched_getcpu() on the threads, they all return that they are running on CPU 4. Anybody know what my problem here is? Thanks in advance! #define _GNU_SOURCE #include <stdio.h> #include <pthread.h> #include <stdlib.h> #include <sched.h> #include <errno.h> void *pthread_Message(char *message) { printf("%s is running on CPU %d\n", message, sched_getcpu()); } int main() { pthread_t thread1, thread2, thread3, thread4; pthread_t threadArray[4]; cpu_set_t cpu1, cpu2, cpu3, cpu4; char *thread1Msg = "Thread 1"; char *thread2Msg = "Thread 2"; char *thread3Msg = "Thread 3"; char *thread4Msg = "Thread 4"; int thread1Create, thread2Create, thread3Create, thread4Create, i, temp; CPU_ZERO(&cpu1); CPU_SET(1, &cpu1); temp = pthread_setaffinity_np(thread1, sizeof(cpu_set_t), &cpu1); printf("Set returned by pthread_getaffinity_np() contained:\n"); for (i = 0; i < CPU_SETSIZE; i++) if (CPU_ISSET(i, &cpu1)) printf("CPU1: CPU %d\n", i); CPU_ZERO(&cpu2); CPU_SET(2, &cpu2); temp = pthread_setaffinity_np(thread2, sizeof(cpu_set_t), &cpu2); for (i = 0; i < CPU_SETSIZE; i++) if (CPU_ISSET(i, &cpu2)) printf("CPU2: CPU %d\n", i); CPU_ZERO(&cpu3); CPU_SET(3, &cpu3); temp = pthread_setaffinity_np(thread3, sizeof(cpu_set_t), &cpu3); for (i = 0; i < CPU_SETSIZE; i++) if (CPU_ISSET(i, &cpu3)) printf("CPU3: CPU %d\n", i); CPU_ZERO(&cpu4); CPU_SET(4, &cpu4); temp = pthread_setaffinity_np(thread4, sizeof(cpu_set_t), &cpu4); for (i = 0; i < CPU_SETSIZE; i++) if (CPU_ISSET(i, &cpu4)) printf("CPU4: CPU %d\n", i); thread1Create = pthread_create(&thread1, NULL, (void *)pthread_Message, thread1Msg); thread2Create = pthread_create(&thread2, NULL, (void *)pthread_Message, thread2Msg); thread3Create = pthread_create(&thread3, NULL, (void *)pthread_Message, thread3Msg); thread4Create = pthread_create(&thread4, NULL, (void *)pthread_Message, thread4Msg); pthread_join(thread1, NULL); pthread_join(thread2, NULL); pthread_join(thread3, NULL); pthread_join(thread4, NULL); return 0; }

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• Why can't Java servlet sent out an object ?

  - by Frank

  I use the following method to send out an object from a servlet : public void doGet(HttpServletRequest request,HttpServletResponse response) throws IOException { String Full_URL=request.getRequestURL().append("?"+request.getQueryString()).toString(); String Contact_Id=request.getParameter("Contact_Id"); String Time_Stamp=Get_Date_Format(6),query="select from "+Contact_Info_Entry.class.getName()+" where Contact_Id == '"+Contact_Id+"' order by Contact_Id desc"; PersistenceManager pm=null; try { pm=PMF.get().getPersistenceManager(); // note that this returns a list, there could be multiple, DataStore does not ensure uniqueness for non-primary key fields List<Contact_Info_Entry> results=(List<Contact_Info_Entry>)pm.newQuery(query).execute(); Write_Serialized_XML(response.getOutputStream(),results.get(0)); } catch (Exception e) { Send_Email(Email_From,Email_To,"Check_License_Servlet Error [ "+Time_Stamp+" ]",new Text(e.toString()+"\n"+Get_Stack_Trace(e)),null); } finally { pm.close(); } } /** Writes the object and CLOSES the stream. Uses the persistance delegate registered in this class. * @param os The stream to write to. * @param o The object to be serialized. */ public static void writeXMLObject(OutputStream os,Object o) { // Classloader reference must be set since netBeans uses another class loader to loead the bean wich will fail in some circumstances. ClassLoader oldClassLoader=Thread.currentThread().getContextClassLoader(); Thread.currentThread().setContextClassLoader(Check_License_Servlet.class.getClassLoader()); XMLEncoder encoder=new XMLEncoder(os); encoder.setExceptionListener(new ExceptionListener() { public void exceptionThrown(Exception e) { e.printStackTrace(); }}); encoder.writeObject(o); encoder.flush(); encoder.close(); Thread.currentThread().setContextClassLoader(oldClassLoader); } private static ByteArrayOutputStream writeOutputStream=new ByteArrayOutputStream(16384); /** Writes an object to XML. * @param out The boject out to write to. [ Will not be closed. ] * @param o The object to write. */ public static synchronized void writeAsXML(ObjectOutput out,Object o) throws IOException { writeOutputStream.reset(); writeXMLObject(writeOutputStream,o); byte[] Bt_1=writeOutputStream.toByteArray(); byte[] Bt_2=new Des_Encrypter().encrypt(Bt_1,Key); out.writeInt(Bt_2.length); out.write(Bt_2); out.flush(); out.close(); } public static synchronized void Write_Serialized_XML(OutputStream Output_Stream,Object o) throws IOException { writeAsXML(new ObjectOutputStream(Output_Stream),o); } At the receiving end the code look like this : File_Url="http://"+Site_Url+App_Dir+File_Name; try { Contact_Info_Entry Online_Contact_Entry=(Contact_Info_Entry)Read_Serialized_XML(new URL(File_Url)); } catch (Exception e) { e.printStackTrace(); } private static byte[] readBuf=new byte[16384]; public static synchronized Object readAsXML(ObjectInput in) throws IOException { // Classloader reference must be set since netBeans uses another class loader to load the bean which will fail under some circumstances. ClassLoader oldClassLoader=Thread.currentThread().getContextClassLoader(); Thread.currentThread().setContextClassLoader(Tool_Lib_Simple.class.getClassLoader()); int length=in.readInt(); readBuf=new byte[length]; in.readFully(readBuf,0,length); byte Bt[]=new Des_Encrypter().decrypt(readBuf,Key); XMLDecoder dec=new XMLDecoder(new ByteArrayInputStream(Bt,0,Bt.length)); Object o=dec.readObject(); Thread.currentThread().setContextClassLoader(oldClassLoader); in.close(); return o; } public static synchronized Object Read_Serialized_XML(URL File_Url) throws IOException { return readAsXML(new ObjectInputStream(File_Url.openStream())); } But I can't get the object from the Java app that's on the receiving end, why ? The error messages look like this : java.lang.ClassNotFoundException: PayPal_Monitor.Contact_Info_Entry Continuing ... java.lang.NullPointerException: target should not be null Continuing ... java.lang.NullPointerException: target should not be null Continuing ... java.lang.NullPointerException: target should not be null Continuing ...

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• Multi-threaded .NET application blocks during file I/O when protected by Themida

  - by Erik Jensen

  As the title says I have a .NET application that is the GUI which uses multiple threads to perform separate file I/O and notice that the threads occasionally block when the application is protected by Themida. One thread is devoted to reading from serial COM port and another thread is devoted to copying files. What I experience is occasionally when the file copy thread encounters a network delay, it will block the other thread that is reading from the serial port. In addition to slow network (which can be transient), I can cause the problem to happen more frequently by making a PathFileExists call to a bad path e.g. PathFileExists("\\\\BadPath\\file.txt"); The COM port reading function will block during the call to ReadFile. This only happens when the application is protected by Themida. I have tried under WinXP, Win7, and Server 2012. In a streamlined test project, if I replace the .NET application with a MFC unmanaged application and still utilize the same threads I see no issue even when protected with Themida. I have contacted Oreans support and here is their response: The way that a .NET application is protected is very different from a native application. To protect a .NET application, we need to hook most of the file access APIs in order to "cheat" the .NET Framework that the application is protected. I guess that those special hooks (on CreateFile, ReadFile...) are delaying a bit the execution in your application and the problem appears. We did a test making those hooks as light as possible (with minimum code on them) but the problem still appeared in your application. The rest of software protectors that we tried (like Enigma, Molebox...) also use a similar hooking approach as it's the only way to make the .NET packed file to work. If those hooks are not present, the .NET Framework will abort execution as it will see that the original file was tampered (due to all Microsoft checks on .NET files) Those hooks are not present in a native application, that's why it should be working fine on your native application. Oreans support tried other software protectors such as Enigma Protector, Engima VirtualBox, and Molebox and all exhibit the exact same problem. What I have found as a work around is to separate out the file copy logic (where the file exists call is being made) to be performed in a completely separate process. I have experimented with converting the thread functions from unmanaged C++ to VB.NET equivalents (PathFileExists - System.IO.File.Exists and CreateFile/ReadFile - System.IO.Ports.SerialPort.Open/Read) and still see the same serial port read blocked when the file check or copy call is delayed. I have also tried setting the ReadFile to work asynchronously but that had no effect. I believe I am dealing with some low-level windows layer that no matter the language it exhibits a block on a shared resource -- and only when the application is executing under a single .NET process protected by Themida which evidently installs some hooks to allow .NET execution. At this time converting the entire application away from .NET is not an option. Nor is separating out the file copy logic to a separate task. I am wondering if anyone else has more knowledge of how a file operation can block another thread reading from a system port. I have included here example applications that show the problem: https://db.tt/cNMYfEIg - VB.NET https://db.tt/Y2lnTqw7 - MFC They are Visual Studio 2010 solutions. When running the themida protected exe, you can see when the FileThread counter pauses (executing the File.Exists call) while the ReadThread counter also pauses. When running non-protected visual studio output exe, the ReadThread counter does not pause which is how we expect it to function. Thanks!

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• what's wrong with my producer-consumer queue design?

  - by toasteroven

  I'm starting with the C# code example here. I'm trying to adapt it for a couple reasons: 1) in my scenario, all tasks will be put in the queue up-front before consumers will start, and 2) I wanted to abstract the worker into a separate class instead of having raw Thread members within the WorkerQueue class. My queue doesn't seem to dispose of itself though, it just hangs, and when I break in Visual Studio it's stuck on the _th.Join() line for WorkerThread #1. Also, is there a better way to organize this? Something about exposing the WaitOne() and Join() methods seems wrong, but I couldn't think of an appropriate way to let the WorkerThread interact with the queue. Also, an aside - if I call q.Start(#) at the top of the using block, only some of the threads every kick in (e.g. threads 1, 2, and 8 process every task). Why is this? Is it a race condition of some sort, or am I doing something wrong? using System; using System.Collections.Generic; using System.Text; using System.Messaging; using System.Threading; using System.Linq; namespace QueueTest { class Program { static void Main(string[] args) { using (WorkQueue q = new WorkQueue()) { q.Finished += new Action(delegate { Console.WriteLine("All jobs finished"); }); Random r = new Random(); foreach (int i in Enumerable.Range(1, 10)) q.Enqueue(r.Next(100, 500)); Console.WriteLine("All jobs queued"); q.Start(8); } } } class WorkQueue : IDisposable { private Queue _jobs = new Queue(); private int _job_count; private EventWaitHandle _wh = new AutoResetEvent(false); private object _lock = new object(); private List _th; public event Action Finished; public WorkQueue() { } public void Start(int num_threads) { _job_count = _jobs.Count; _th = new List(num_threads); foreach (int i in Enumerable.Range(1, num_threads)) { _th.Add(new WorkerThread(i, this)); _th[_th.Count - 1].JobFinished += new Action(WorkQueue_JobFinished); } } void WorkQueue_JobFinished(int obj) { lock (_lock) { _job_count--; if (_job_count == 0 && Finished != null) Finished(); } } public void Enqueue(int job) { lock (_lock) _jobs.Enqueue(job); _wh.Set(); } public void Dispose() { Enqueue(Int32.MinValue); _th.ForEach(th = th.Join()); _wh.Close(); } public int GetNextJob() { lock (_lock) { if (_jobs.Count 0) return _jobs.Dequeue(); else return Int32.MinValue; } } public void WaitOne() { _wh.WaitOne(); } } class WorkerThread { private Thread _th; private WorkQueue _q; private int _i; public event Action JobFinished; public WorkerThread(int i, WorkQueue q) { _i = i; _q = q; _th = new Thread(DoWork); _th.Start(); } public void Join() { _th.Join(); } private void DoWork() { while (true) { int job = _q.GetNextJob(); if (job != Int32.MinValue) { Console.WriteLine("Thread {0} Got job {1}", _i, job); Thread.Sleep(job * 10); // in reality would to actual work here if (JobFinished != null) JobFinished(job); } else { Console.WriteLine("Thread {0} no job available", _i); _q.WaitOne(); } } } } }

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• Database call crashes Android Application

  - by Darren Murtagh

  i am using a Android database and its set up but when i call in within an onClickListener and the app crashes the code i am using is mButton.setOnClickListener( new View.OnClickListener() { public void onClick(View view) { s = WorkoutChoice.this.weight.getText().toString(); s2 = WorkoutChoice.this.height.getText().toString(); int w = Integer.parseInt(s); double h = Double.parseDouble(s2); double BMI = (w/h)/h; t.setText(""+BMI); long id = db.insertTitle("001", ""+days, ""+BMI); Cursor c = db.getAllTitles(); if (c.moveToFirst()) { do { DisplayTitle(c); } while (c.moveToNext()); } } }); and the log cat for when i run it is: 04-01 18:21:54.704: E/global(6333): Deprecated Thread methods are not supported. 04-01 18:21:54.704: E/global(6333): java.lang.UnsupportedOperationException 04-01 18:21:54.704: E/global(6333): at java.lang.VMThread.stop(VMThread.java:85) 04-01 18:21:54.704: E/global(6333): at java.lang.Thread.stop(Thread.java:1391) 04-01 18:21:54.704: E/global(6333): at java.lang.Thread.stop(Thread.java:1356) 04-01 18:21:54.704: E/global(6333): at com.b00348312.workout.Splashscreen$1.run(Splashscreen.java:42) 04-01 18:22:09.444: D/dalvikvm(6333): GC_FOR_MALLOC freed 4221 objects / 252640 bytes in 31ms 04-01 18:22:09.474: I/dalvikvm(6333): Total arena pages for JIT: 11 04-01 18:22:09.574: D/dalvikvm(6333): GC_FOR_MALLOC freed 1304 objects / 302920 bytes in 29ms 04-01 18:22:09.744: D/dalvikvm(6333): GC_FOR_MALLOC freed 2480 objects / 290848 bytes in 33ms 04-01 18:22:10.034: D/dalvikvm(6333): GC_FOR_MALLOC freed 6334 objects / 374152 bytes in 36ms 04-01 18:22:14.344: D/AndroidRuntime(6333): Shutting down VM 04-01 18:22:14.344: W/dalvikvm(6333): threadid=1: thread exiting with uncaught exception (group=0x400259f8) 04-01 18:22:14.364: E/AndroidRuntime(6333): FATAL EXCEPTION: main 04-01 18:22:14.364: E/AndroidRuntime(6333): java.lang.IllegalStateException: database not open 04-01 18:22:14.364: E/AndroidRuntime(6333): at android.database.sqlite.SQLiteDatabase.insertWithOnConflict(SQLiteDatabase.java:1567) 04-01 18:22:14.364: E/AndroidRuntime(6333): at android.database.sqlite.SQLiteDatabase.insert(SQLiteDatabase.java:1484) 04-01 18:22:14.364: E/AndroidRuntime(6333): at com.b00348312.workout.DataBaseHelper.insertTitle(DataBaseHelper.java:84) 04-01 18:22:14.364: E/AndroidRuntime(6333): at com.b00348312.workout.WorkoutChoice$3.onClick(WorkoutChoice.java:84) 04-01 18:22:14.364: E/AndroidRuntime(6333): at android.view.View.performClick(View.java:2408) 04-01 18:22:14.364: E/AndroidRuntime(6333): at android.view.View$PerformClick.run(View.java:8817) 04-01 18:22:14.364: E/AndroidRuntime(6333): at android.os.Handler.handleCallback(Handler.java:587) 04-01 18:22:14.364: E/AndroidRuntime(6333): at android.os.Handler.dispatchMessage(Handler.java:92) 04-01 18:22:14.364: E/AndroidRuntime(6333): at android.os.Looper.loop(Looper.java:144) 04-01 18:22:14.364: E/AndroidRuntime(6333): at android.app.ActivityThread.main(ActivityThread.java:4937) 04-01 18:22:14.364: E/AndroidRuntime(6333): at java.lang.reflect.Method.invokeNative(Native Method) 04-01 18:22:14.364: E/AndroidRuntime(6333): at java.lang.reflect.Method.invoke(Method.java:521) 04-01 18:22:14.364: E/AndroidRuntime(6333): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:858) 04-01 18:22:14.364: E/AndroidRuntime(6333): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616) 04-01 18:22:14.364: E/AndroidRuntime(6333): at dalvik.system.NativeStart.main(Native Method) i have notice errors when the application opens but i dont no what thet are from. when i take out the statements to do with the database there is no errors and everthign runs smoothly

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• C#: Parallel forms, multithreading and "applications in application"

  - by Harry

  First, what I need is - n WebBrowser-s, each in its own window doing its own job. The user should be able to see them all, or just one of them (or none), and to execute commands on each one. There is a main form, without a browser, this one contains control panel for my application. The key feautre is, each browser logs on to secured web page and it needs to stay logged in as long as possible. Well, I've done it, but I'm afraid something is wrong with my approach. The question is: Is code below valid, or rather a nasty hack which can cause problems: internal class SessionList : List<Session> { public SessionList(Server main) { MyRecords.ForEach(record => { var st = new System.Threading.Thread((data) => { var s = new Session(main, data as MyRecord); this.Add(s); Application.Run(s); Application.ExitThread(); }); st.SetApartmentState(System.Threading.ApartmentState.STA); st.Start(record); }); } // some other uninteresting methods here... } What's going on here? Session inherits from Form, so it creates a form, puts WebBrowser into it, and has methods to operate on websites. WebBrowser requires to be run in STA thread, so we provide one for each browser. The most interesting part of it is Application.Run(s). It makes the newly created forms alive and interactive. The next Application.ExitThread() is called after browser window is closed and its controls disposed. Main application stays alive to perform the rest of the cleanup job. When user select "Exit" or "Shutdown" option - first the browser threads are ended, so Application.ExitThread() is called. It all works, but everywhere I can read about "main GUI thread" - and here - I've created many GUI threads. I handle communication between main form and my new forms (sessions) with thread-safe methods using Invoke(). It all works, so is it right or is it wrong? Is everything right with using Application.Run() more than once in one application? :) An ugly hack or a normal practice? This code dies if I start a WebBrowser from the session form thread. It beats me why. It works however if I start WebBrowser (by changing its Url property) from any other thread. I'd like to know more what is really happening in such application. But most of all - I'd like to know if my idea of "applications in application" is OK. I'm not sure what exactly does Application.Run() do. Without it forms created in new threads were dead unresponsive. How is it possible I can call Application.Run() many times? It seems to do exactly what it should, but it seems a little undocumented feature to me. I'm almost sure, that the crashes are caused by WebBrowser component itself (since it's not completely "managed" and "native"). But maybe it's something else.

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• "FOR UPDATE" v/s "LOCK IN SHARE MODE" : Allow concurrent threads to read updated "state" value of locked row

  - by shadesco

  I have the following scenario: User X logs in to the application from location lc1: call it Ulc1 User X (has been hacked, or some friend of his knows his login credential, or he just logs in from a different browser on his machine,etc.. u got the point) logs in at the same time from location lc2: call it Ulc2 I am using a main servlet which : - gets a connection from database pooling - sets autocommit to false - executes a command that goes through app layers: if all successful, set autocommit to true in a "finally" statement, and closes connection. Else if an exception happens, rollback(). In my database (mysql/innoDb) i have a "history" table, with row columns: id(primary key) |username | date | topic | locked The column "locked" has by default value "false" and it serves as a flag that marks if a specific row is locked or not. Each row is specific to a user (as u can see from the username column) So back to the scenario: --Ulc1 sends the command to update his history from the db for date "D" and topic "T". --Ulc2 sends the same command to update history from the db for the same date "D" and same topic "T" at the exact same time. I want to implement an mysql/innoDB locking system that will enable whichever thread arriving to do the following check: Is column "locked" for this row true or not? if true, return a message to the user that " he is already updating the same data from another location" if not true (ie not locked) : flag it as locked and update then reset locked to false once finished. Which of these two mysql locking techniques, will actually allow the 2nd arriving thread from reading the "updated" value of the locked column to decide wt action to take?Should i use "FOR UPDATE" or "LOCK IN SHARE MODE"? This scenario explains what i want to accomplish: - Ulc1 thread arrives first: column "locked" is false, set it to true and continue updating process - Ulc2 thread arrives while Ulc1's transaction is still in process, and even though the row is locked through innoDb functionalities, it doesn't have to wait but in fact reads the "new" value of column locked which is "true", and so doesn't in fact have to wait till Ulc1 transaction commits to read the value of the "locked" column(anyway by that time the value of this column will already have been reset to false). I am not very experienced with the 2 types of locking mechanisms, what i understand so far is that LOCK IN SHARE MODE allow other transaction to read the locked row while FOR UPDATE doesn't even allow reading. But does this read gets on the updated value? or the 2nd arriving thread has to wait the first thread to commit to then read the value? Any recommendations about which locking mechanism to use for this scenario is appreciated. Also if there's a better way to "check" if the row has been locked (other than using a true/false column flag) please let me know about it. thank you SOLUTION (Jdbc pseudocode example based on @Darhazer's answer) Table : [ id(primary key) |username | date | topic | locked ] connection.setautocommit(false); //transaction-1 PreparedStatement ps1 = "Select locked from tableName for update where id="key" and locked=false); ps1.executeQuery(); //transaction 2 PreparedStatement ps2 = "Update tableName set locked=true where id="key"; ps2.executeUpdate(); connection.setautocommit(true);// here we allow other transactions threads to see the new value connection.setautocommit(false); //transaction 3 PreparedStatement ps3 = "Update tableName set aField="Sthg" where id="key" And date="D" and topic="T"; ps3.executeUpdate(); // reset locked to false PreparedStatement ps4 = "Update tableName set locked=false where id="key"; ps4.executeUpdate(); //commit connection.setautocommit(true);

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• Ubuntu 10.04 - unable to install Arduino

  - by Newbie

  Hello! At the moment, I try to install Arduino on my Ubuntu 10.04 (32 Bit) computer. I downloaded the latest release at http://arduino.cc/en/Main/Software, cd'ed to the directory and unziped the package. When I try to run ./arduino , I get following error: Exception in thread "main" java.lang.ExceptionInInitializerError at processing.app.Base.main(Base.java:112) Caused by: java.awt.HeadlessException at sun.awt.HeadlessToolkit.getMenuShortcutKeyMask(HeadlessToolkit.java:231) at processing.core.PApplet.<clinit>(Unknown Source) ... 1 more Here is my java -version output: java version "1.6.0_20" OpenJDK Runtime Environment (IcedTea6 1.9.5) (6b20-1.9.5-0ubuntu1~10.04.1) OpenJDK Server VM (build 19.0-b09, mixed mode) Any suggestions on this? I try to install arduino without the 'arduino' package. I tried to install it with apt-get (sudo apt-get install arduino). When I try to start arduino (using arduino command) will cause following error: Exception in thread "main" java.lang.ExceptionInInitializerError at processing.app.Preferences.load(Preferences.java:553) at processing.app.Preferences.load(Preferences.java:549) at processing.app.Preferences.init(Preferences.java:142) at processing.app.Base.main(Base.java:188) Caused by: java.awt.HeadlessException at sun.awt.HeadlessToolkit.getMenuShortcutKeyMask(HeadlessToolkit.java:231) at processing.core.PApplet.<clinit>(PApplet.java:224) ... 4 more Update: I saw that I installed several versions of jre (sun and open). So I uninstalled the open jre. Now, when calling arduino I get a new error: java.lang.UnsatisfiedLinkError: no rxtxSerial in java.library.path thrown while loading gnu.io.RXTXCommDriver Exception in thread "main" java.lang.UnsatisfiedLinkError: no rxtxSerial in java.library.path at java.lang.ClassLoader.loadLibrary(ClassLoader.java:1734) at java.lang.Runtime.loadLibrary0(Runtime.java:823) at java.lang.System.loadLibrary(System.java:1028) at gnu.io.CommPortIdentifier.<clinit>(CommPortIdentifier.java:123) at processing.app.Editor.populateSerialMenu(Editor.java:965) at processing.app.Editor.buildToolsMenu(Editor.java:717) at processing.app.Editor.buildMenuBar(Editor.java:502) at processing.app.Editor.<init>(Editor.java:194) at processing.app.Base.handleOpen(Base.java:698) at processing.app.Base.handleOpen(Base.java:663) at processing.app.Base.handleNew(Base.java:578) at processing.app.Base.<init>(Base.java:318) at processing.app.Base.main(Base.java:207)

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• Glenn Fiedler's fixed timestep with fake threads

  - by kaoD

  I've implemented Glenn Fiedler's Fix Your Timestep! quite a few times in single-threaded games. Now I'm facing a different situation: I'm trying to do this in JavaScript. I know JS is single-threaded, but I plan on using requestAnimationFrame for the rendering part. This leaves me with two independent fake threads: simulation and rendering (I suppose requestAnimationFrame isn't really threaded, is it? I don't think so, it would BREAK JS.) Timing in these threads is independent too: dt for simulation and render is not the same. If I'm not mistaken, simulation should be up to Fiedler's while loop end. After the while loop, accumulator < dt so I'm left with some unspent time (dt) in the simulation thread. The problem comes in the draw/interpolation phase: const double alpha = accumulator / dt; State state = currentState*alpha + previousState * ( 1.0 - alpha ); render( state ); In my render callback, I have the current timestamp to which I can subtract the last-simulated-in-physics-timestamp to have a dt for the current frame. Should I just forget about this dt and draw using the physics thread's dt? It seems weird, since, well, I want to interpolate for the unspent time between simulation and render too, right? Of course, I want simulation and rendering to be completely independent, but I can't get around the fact that in Glenn's implementation the renderer produces time and the simulation consumes it in discrete dt sized chunks. A similar question was asked in Semi Fixed-timestep ported to javascript but the question doesn't really get to the point, and answers there point to removing physics from the render thread (which is what I'm trying to do) or just keeping physics in the render callback too (which is what I'm trying to avoid.)

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• New Enhancements for InnoDB Memcached

  - by Calvin Sun

  In MySQL 5.6, we continued our development on InnoDB Memcached and completed a few widely desirable features that make InnoDB Memcached a competitive feature in more scenario. Notablely, they are 1) Support multiple table mapping 2) Added background thread to auto-commit long running transactions 3) Enhancement in binlog performance  Let’s go over each of these features one by one. And in the last section, we will go over a couple of internally performed performance tests. Support multiple table mapping In our earlier release, all InnoDB Memcached operations are mapped to a single InnoDB table. In the real life, user might want to use this InnoDB Memcached features on different tables. Thus being able to support access to different table at run time, and having different mapping for different connections becomes a very desirable feature. And in this GA release, we allow user just be able to do both. We will discuss the key concepts and key steps in using this feature. 1) "mapping name" in the "get" and "set" command In order to allow InnoDB Memcached map to a new table, the user (DBA) would still require to "pre-register" table(s) in InnoDB Memcached “containers” table (there is security consideration for this requirement). If you would like to know about “containers” table, please refer to my earlier blogs in blogs.innodb.com. Once registered, the InnoDB Memcached will then be able to look for such table when they are referred. Each of such registered table will have a unique "registration name" (or mapping_name) corresponding to the “name” field in the “containers” table.. To access these tables, user will include such "registration name" in their get or set commands, in the form of "get @@new_mapping_name.key", prefix "@@" is required for signaling a mapped table change. The key and the "mapping name" are separated by a configurable delimiter, by default, it is ".". So the syntax is: get [@@mapping_name.]key_name set [@@mapping_name.]key_name  or  get @@mapping_name set @@mapping_name Here is an example: Let's set up three tables in the "containers" table: The first is a map to InnoDB table "test/demo_test" table with mapping name "setup_1" INSERT INTO containers VALUES ("setup_1", "test", "demo_test", "c1", "c2", "c3", "c4", "c5", "PRIMARY");  Similarly, we set up table mappings for table "test/new_demo" with name "setup_2" and that to table "mydatabase/my_demo" with name "setup_3": INSERT INTO containers VALUES ("setup_2", "test", "new_demo", "c1", "c2", "c3", "c4", "c5", "secondary_index_x"); INSERT INTO containers VALUES ("setup_3", "my_database", "my_demo", "c1", "c2", "c3", "c4", "c5", "idx"); To switch to table "my_database/my_demo", and get the value corresponding to “key_a”, user will do: get @@setup_3.key_a (this will also output the value that corresponding to key "key_a" or simply get @@setup_3 Once this is done, this connection will switch to "my_database/my_demo" table until another table mapping switch is requested. so it can continue issue regular command like: get key_b  set key_c 0 0 7 These DMLs will all be directed to "my_database/my_demo" table. And this also implies that different connections can have different bindings (to different table). 2) Delimiter: For the delimiter "." that separates the "mapping name" and key value, we also added a configure option in the "config_options" system table with name of "table_map_delimiter": INSERT INTO config_options VALUES("table_map_delimiter", "."); So if user wants to change to a different delimiter, they can change it in the config_option table. 3) Default mapping: Once we have multiple table mapping, there should be always a "default" map setting. For this, we decided if there exists a mapping name of "default", then this will be chosen as default mapping. Otherwise, the first row of the containers table will chosen as default setting. Please note, user tables can be repeated in the "containers" table (for example, user wants to access different columns of the table in different settings), as long as they are using different mapping/configure names in the first column, which is enforced by a unique index. 4) bind command In addition, we also extend the protocol and added a bind command, its usage is fairly straightforward. To switch to "setup_3" mapping above, you simply issue: bind setup_3 This will switch this connection's InnoDB table to "my_database/my_demo" In summary, with this feature, you now can direct access to difference tables with difference session. And even a single connection, you can query into difference tables. Background thread to auto-commit long running transactions This is a feature related to the “batch” concept we discussed in earlier blogs. This “batch” feature allows us batch the read and write operations, and commit them only after certain calls. The “batch” size is controlled by the configure parameter “daemon_memcached_w_batch_size” and “daemon_memcached_r_batch_size”. This could significantly boost performance. However, it also comes with some disadvantages, for example, you will not be able to view “uncommitted” operations from SQL end unless you set transaction isolation level to read_uncommitted, and in addition, this will held certain row locks for extend period of time that might reduce the concurrency. To deal with this, we introduce a background thread that “auto-commits” the transaction if they are idle for certain amount of time (default is 5 seconds). The background thread will wake up every second and loop through every “connections” opened by Memcached, and check for idle transactions. And if such transaction is idle longer than certain limit and not being used, it will commit such transactions. This limit is configurable by change “innodb_api_bk_commit_interval”. Its default value is 5 seconds, and minimum is 1 second, and maximum is 1073741824 seconds. With the help of such background thread, you will not need to worry about long running uncommitted transactions when set daemon_memcached_w_batch_size and daemon_memcached_r_batch_size to a large number. This also reduces the number of locks that could be held due to long running transactions, and thus further increase the concurrency. Enhancement in binlog performance As you might all know, binlog operation is not done by InnoDB storage engine, rather it is handled in the MySQL layer. In order to support binlog operation through InnoDB Memcached, we would have to artificially create some MySQL constructs in order to access binlog handler APIs. In previous lab release, for simplicity consideration, we open and destroy these MySQL constructs (such as THD) for each operations. This required us to set the “batch” size always to 1 when binlog is on, no matter what “daemon_memcached_w_batch_size” and “daemon_memcached_r_batch_size” are configured to. This put a big restriction on our capability to scale, and also there are quite a bit overhead in creating destroying such constructs that bogs the performance down. With this release, we made necessary change that would keep MySQL constructs as long as they are valid for a particular connection. So there will not be repeated and redundant open and close (table) calls. And now even with binlog option is enabled (with innodb_api_enable_binlog,), we still can batch the transactions with daemon_memcached_w_batch_size and daemon_memcached_r_batch_size, thus scale the write/read performance. Although there are still overheads that makes InnoDB Memcached cannot perform as fast as when binlog is turned off. It is much better off comparing to previous release. And we are continuing optimize the solution is this area to improve the performance as much as possible. Performance Study: Amerandra of our System QA team have conducted some performance studies on queries through our InnoDB Memcached connection and plain SQL end. And it shows some interesting results. The test is conducted on a “Linux 2.6.32-300.7.1.el6uek.x86_64 ix86 (64)” machine with 16 GB Memory, Intel Xeon 2.0 GHz CPU X86_64 2 CPUs- 4 Core Each, 2 RAID DISKS (1027 GB,733.9GB). Results are described in following tables: Table 1: Performance comparison on Set operations Connections 5.6.7-RC-Memcached-plugin ( TPS / Qps) with memcached-threads=8*** 5.6.7-RC* X faster Set (QPS) Set** 8 30,000 5,600 5.36 32 59,000 13,000 4.54 128 68,000 8,000 8.50 512 63,000 6.800 9.23 * mysql-5.6.7-rc-linux2.6-x86_64 ** The “set” operation when implemented in InnoDB Memcached involves a couple of DMLs: it first query the table to see whether the “key” exists, if it does not, the new key/value pair will be inserted. If it does exist, the “value” field of matching row (by key) will be updated. So when used in above query, it is a precompiled store procedure, and query will just execute such procedures. *** added “–daemon_memcached_option=-t8” (default is 4 threads) So we can see with this “set” query, InnoDB Memcached can run 4.5 to 9 time faster than MySQL server. Table 2: Performance comparison on Get operations Connections 5.6.7-RC-Memcached-plugin ( TPS / Qps) with memcached-threads=8 5.6.7-RC* X faster Get (QPS) Get 8 42,000 27,000 1.56 32 101,000 55.000 1.83 128 117,000 52,000 2.25 512 109,000 52,000 2.10 With the “get” query (or the select query), memcached performs 1.5 to 2 times faster than normal SQL. Summary: In summary, we added several much-desired features to InnoDB Memcached in this release, allowing user to operate on different tables with this Memcached interface. We also now provide a background commit thread to commit long running idle transactions, thus allow user to configure large batch write/read without worrying about large number of rows held or not being able to see (uncommit) data. We also greatly enhanced the performance when Binlog is enabled. We will continue making efforts in both performance enhancement and functionality areas to make InnoDB Memcached a good demo case for our InnoDB APIs. Jimmy Yang, September 29, 2012

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• Change power button to 'Ask' in Xubuntu 13.10

  - by Gully.Moy

  I have recently installed Xubuntu 13.10 on my Vaio vpcea making me a Linux beginner. The problem is that laptop's power button is right on the edge of the bezel making it far too easy to press accidentally, in my opinion a design fault by Sony. At present, when I press the power button it shuts down strait away and as you can imagine, when I'm accidentally pressing it all the time it gets very annoying! So I planned to change it to ask what I would like to do when I press it or at least ask if I'm sure. So I went through the xfce GUI options "Settings Manager" - "Power Manager" to the field "When power button is pressed", but it was already set to "Ask". So I did some digging and found a thread telling me to navigate to /etc/xdg/xfce4/xfconf/xfce-perchannel-xml/xfce4-power-manager.xml where it said to find power-button-action and check that value="3". It already did. So I looked some more and found this thread which focuses on acpi scripts. I tried solution 1 & 2 using sudoedit to change the files accordingly (I have made executable bash shell scripts already so I think I followed them correctly), but still no difference. I also found this thread which instructed me to edit /etc/systemd/logind.conf so that HandlePowerKey=ignore. Still no luck. I even tried my own approach to completely disable /etc/acpi/powerbtn.sh by renaming it powerbtn.sh.bak hoping for at least no response from the power button... and I have done many reboots in between... but still it shuts down! I have also read that some people have the file /etc/acpi/events/power_button, but I do not. So does anyone have any other ideas? What else could be executing the shutdown sequence Is there something I'm missing? I haven't undone any of these actions so every one of the above files is currently edited on my computer, with the exception that "Solution 2" automatically undone "Solution 1" above. Thanks guys.

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• Bash Script help required

  - by Sunil J

  I am trying to get this bash script that i found on a forum to work. Copied it to text editor. Saved it as script.sh chmod 700 and tried to run it. rootdir="/usr/share/malware" day=`date +%Y%m%d` url=`echo "wget -qO - http://lists.clean-mx.com/pipermail/viruswatch/$day/thread.html |\ awk '/\[Virus/'|tail -n 1|sed 's:\": :g' |\ awk '{print \"http://lists.clean-mx.com/pipermail/viruswatch/$day/\"$3}'"|sh` filename=`wget -qO - http://lists.clean-mx.com/pipermail/viruswatch/$day/thread.html |\ awk '/\[Virus/'|tail -n 1|sed 's:": :g' |awk '{print $3}'` links -dump $url$filename | awk '/Up/'|grep "TR\|exe" | awk '{print $2,$8,$10,$11,$12"\n"}' > $rootdir/>$filename dirname=`wget -qO - http://lists.clean-mx.com/pipermail/viruswatch/$day/thread.html |\ awk '/\[Virus/'|tail -n 1|sed 's:": :g' |awk '{print $3}'|sed 's:.html::g'` rm -rf $rootdir/$dirname mkdir $rootdir/$dirname cd $rootdir grep "exe$" $filename |awk '{print "wget \""$5"\""}' | sh ls *.exe | xargs md5 >> checksums mv *.exe $dirname rm -r $rootdir/*exe* mv checksums $rootdir/$dirname mv $filename $rootdir/$dirname I get the following message.. script.sh: line 11: /usr/share/malware/: Is a directory script.sh: line 11: links: command not found

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• Does concurrency inherently introduce "randomness" into a game?

  - by Jeff

  When a game is implemented with concurrency (as most games are), does this necessarily, by its very nature, introduce an element of randomness into the game that is outside of the players' control? Note that when I use the word "random", I'm not meaning to launch into a philosophical debate about the deterministic nature of the system. I understand that concurrency is deterministic in the sense that the operating system decides which processes to allow time on the CPU and in what order (or the JVM controls which Thread's turn it is to execute, etc). But my understanding of this is that there is no way to control or predict whether one thread's next command will execute before or after another. The reason I'm asking is because this seems like a fundamental difficulty for game development where a game is supposedly designed around a player's skill. Consider a game like League of Legends. Assume that two players are battling it out. It's a very close contest between the two and it's coming down to the wire -- so much so that whoever gets their last attack off will be the one to kill the other and win the game for their team. If the players are implemented using concurrency and the situation really was like this, is it essentially out of the players' hands at this point? Is the outcome of this match all up to whatever system is arbitrarily deciding which player's thread/process will execute next? If not, what am I misunderstanding about concurrency? If so, is there any way around this problem so that a game of skill can always be a game of skill, especially in those most crucial moments?

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• Tuning B2B Server Engine Threads in SOA Suite 11g

  - by Shub Lahiri, A-Team

  Background B2B 11g has a number of parameters that can be tweaked to tune the engine for handling high volumes of messages. These parameters are also known as B2B server properties and managed via the EM console.  This note highlights one aspect of the tuning exercise and describes the different threads, that can be configured to tune the performance of a B2B server. Symptoms The most common indicator of a B2B engine in need of a tuning is reflected in the constant build-up of messages in an internal JMS queue within the B2B server. It is called B2B_EVENT_QUEUE and can be monitored via the Weblogic server console. Whenever such a behaviour is seen, it usually results in general degradation of performance. Remedy There could be many contributing factors behind a B2B server's degradation of performance. However, one of the first places to tune the server from the out-of-the-box, default configuration is to change the number of internal engine threads allocated within the B2B server. Usually the default configuration for the B2B server engine threads is not suitable for high-volume of messaging loads. So, it is necessary to increase the counts for 3 types of such threads, by specifying the appropriate B2B server properties via the EM console, namely, Inbound - b2b.inboundThreadCount Outbound - b2b.outboundThreadCount Default - b2b.defaultThreadCount The function of these threads are fairly self-explanatory. In other words, the inbound threads process the inbound messages that are coming into the B2B server from an external endpoint. Similarly, the outbound threads processes the messages that are sent out from the B2B server. The default threads are responsible for certain B2B server-specific special tasks. In case the inbound and outbound thread counts are not specified, the default thread count also dictates the total number of inbound and outbound threads. As found in any tuning exercise, the optimisation of these threads is usually reached via an iterative process. The best working combination of the thread counts are directly related to the system infrastructure, traffic load and several other environmental factors.

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• Pattern for Accessing MySQL connection

  - by Dipan Mehta

  We have an application which is C++ trying to access MySQL database. There are several (about 5 or so) threads in the application (with Boost library for threading) and in each thread has a few objects, each of which is trying to access Database for its' own purpose. It has a simple ORM kind of model but that really is not an important factor here. There are three potential access patterns i can think of: There could be single connection object per application or thread and is shared between all (or group). The object needs to be thread safe and there will be contentions but MySQL will not be fired with too many connections. Every object could initiate connection on its own. The database needs to take care of concurrency (which i think MySQL can) and the design could be much simpler. There could be two possibilities here. a. either object keeps a persistent connection for its life OR b. object initiate connection as and when needed. To simplify the contention as in case of 1 and not to create too many sockets as in case of 2, we can have group/set based connections. So there could be there could be more than one connection (say N), each of this connection could be shared connection across M objects. Naturally, each of the pattern has different resource cost and would work under different constraints and objectives. What criteria should i use to choose the pattern of this for my own application? What are some of the advantages and disadvantages of each of these pattern over the other? Are there any other pattern which is better? PS: I have been through these questions: mysql, one connection vs multiple and MySQL with mutiple threads and processes But they don't quite answer exactly what i am trying to ask.

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• Design pattern for an automated mechanical test bench

  - by JJS

  Background I have a test fixture with a number of communication/data acquisition devices on it that is used as an end of line test for a product. Because of all the various sensors used in the bench and the need to run the test procedure in near real-time, I'm having a hard time structuring the program to be more friendly to modify later on. For example, a National Instruments USB data acquisition device is used to control an analog output (load) and monitor an analog input (current), a digital scale with a serial data interface measures position, an air pressure gauge with a different serial data interface, and the product is interfaced through a proprietary DLL that handles its own serial communication. The hard part The "real-time" aspect of the program is my biggest tripping point. For example, I need to time how long the product needs to go from position 0 to position 10,000 to the tenth of a second. While it's traveling, I need to ramp up an output of the NI DAQ when it reaches position 6,000 and ramp it down when it reaches position 8,000. This sort of control looks easy from browsing NI's LabVIEW docs but I'm stuck with C# for now. All external communication is done by polling which makes for lots of annoying loops. I've slapped together a loose Producer Consumer model where the Producer thread loops through reading the sensors and sets the outputs. The Consumer thread executes functions containing timed loops that poll the Producer for current data and execute movement commands as required. The UI thread polls both threads for updating some gauges indicating current test progress. Unsure where to start Is there a more appropriate pattern for this type of application? Are there any good resources for writing control loops in software (non-LabVIEW) that interface with external sensors and whatnot?

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• Are these advanced/unfair interview questions regarding Java concurrency?

  - by sparc_spread

  Here are some questions I've recently asked interviewees who say they know Java concurrency: Explain the hazard of "memory visibility" - the way the JVM can reorder certain operations on variables that are unprotected by a monitor and not declared volatile, such that one thread may not see the changes made by another thread. Usually I ask this one by showing code where this hazard is present (e.g. the NoVisibility example in Listing 3.1 from "Java Concurrency in Practice" by Goetz et al) and asking what is wrong. Explain how volatile affects not just the actual variable declared volatile, but also any changes to variables made by a thread before it changes the volatile variable. Why might you use volatile instead of synchronized? Implement a condition variable with wait() and notifyAll(). Explain why you should use notifyAll(). Explain why the condition variable should be tested with a while loop. My question is - are these appropriate or too advanced to ask someone who says they know Java concurrency? And while we're at it, do you think that someone working in Java concurrency should be expected to have an above-average knowledge of Java garbage collection?

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• TXPAUSE : polite waiting for hardware transactional memory

  - by Dave

  Classic locks are an appropriate tool to prevent potentially conflicting operations A and B, invoked by different threads, from running at the same time. In a sense the locks cause either A to run before B or vice-versa. Similarly, we can replace the locks with hardware transactional memory, or use transactional lock elision to leverage potential disjoint access parallelism between A and B. But often we want A to wait until B has run. In a Pthreads environment we'd usually use locks in conjunction with condition variables to implement our "wait until" constraint. MONITOR-MWAIT is another way to wait for a memory location to change, but it only allows us to track one cache line and it's only available on x86. There's no similar "wait until" construct for hardware transactions. At the instruction-set level a simple way to express "wait until" in transactions would be to add a new TXPAUSE instruction that could be used within an active hardware transaction. TXPAUSE would politely stall the invoking thread, possibly surrendering or yielding compute resources, while at the same time continuing to track the transaction's address-set. Once a transaction has executed TXPAUSE it can only abort. Ideally that'd happen when some other thread modifies a variable that's in the transaction's read-set or write-set. And since we're aborting all writes would be discarded. In a sense this gives us multi-location MWAIT but with much more flexibility. We could also augment the TXPAUSE with a cycle-count bound to cap the time spent stalled. I should note that we can already enter a tight spin loop in a transaction to wait for updates to address-set to cause an abort. Assuming that the implementation monitors the address-set via cache-coherence probes, by waiting in this fashion we actually communicate via the probes, and not via memory values. That is the updating thread signals the waiter via probes instead of by traditional memory values. But TXPAUSE gives us a polite way to spin.

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• Android 2D terrain scrolling

  - by Nikola Ninkovic

  I want to make infinite 2D terrain based on my algorithm.Then I want to move it along Y axis (to the left) This is how I did it : public class Terrain { Queue<Integer> _bottom; Paint _paint; Bitmap _texture; Point _screen; int _numberOfColumns = 100; int _columnWidth = 20; public Terrain(int screenWidth, int screenHeight, Bitmap texture) { _bottom = new LinkedList<Integer>(); _screen = new Point(screenWidth, screenHeight); _numberOfColumns = screenWidth / 6; _columnWidth = screenWidth / _numberOfColumns; for(int i=0;i<=_numberOfColumns;i++) { // Generate terrain point and put it into _bottom queue } _paint = new Paint(); _paint.setStyle(Paint.Style.FILL); _paint.setShader(new BitmapShader(texture, Shader.TileMode.REPEAT, Shader.TileMode.REPEAT)); } public void update() { _bottom.remove(); // Algorithm calculates next point _bottom.add(nextPoint); } public void draw(Canvas canvas) { Iterator<Integer> i = _bottom.iterator(); int counter = 0; Path path = new Path(); path.moveTo(0, _screen.y); while (i.hasNext()) { path.lineTo(counter, _screen.y-i.next()); counter += _columnWidth; } path.lineTo(_screen.x, _screen.y); path.lineTo(0, _screen.y); canvas.drawPath(path2, _paint); } } The problem is that the game is too 'fast', so I tried with pausing thread with Thread.sleep(50); in run() method of my game thread but then it looks too torn. Well, is there any way to slow down drawing of my terrain ?

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• Get Func-y v2.0

  - by PhubarBaz

  In my last post I talked about using funcs in C# to do async calls in WinForms to free up the main thread for the UI. In that post I demonstrated calling a method and then waiting until the value came back. Today I want to talk about calling a method and then continuing on and handling the results of the async call in a callback.The difference is that in the previous example although the UI would not lock up the user couldn't really do anything while the other thread was working because it was waiting for it to finish. This time I want to allow the user to continue to do other stuff while waiting for the thread to finish.Like before I have a service call I want to make that takes a long time to finish defined in a method called MyServiceCall. We need to define a callback method takes an IAsyncResult parameter.public ServiceCallResult MyServiceCall(int param1)...public int MyCallbackMethod(IAsyncResult ar)...We start the same way by defining a delegate to the service call method using a Func. We need to pass an AsyncCallback object into the BeginInvoke method. This will tell it to call our callback method when MyServiceCall finishes. The second parameter to BeginInvoke is the Func delegate. This will give us access to it in our callback.Func<int, ServiceCallResult> f = MyServiceCall;AsyncCallback callback =   new AsyncCallback(MyCallbackMethod);IAsyncResult async = f.BeginInvoke(23, callback, f); Now let's expand the callback method. The IAsyncResult parameter contains the Func delegate in its AsyncState property. We call EndInvoke on that Func to get the return value.public int MyCallbackMethod(IAsyncResult ar){    Func<int, ServiceCallResult> delegate =        (Func<int, ServiceCallResult>)ar.AsyncState;    ServiceCallResult result = delegate.EndInvoke(ar);}There you have it. Now you don't have to make the user wait for something that isn't critical to the loading of the page.

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• MVC pattern synchronisation

  - by Hariprasad

  I am facing a problem in synchronizing my model and view threads I have a view which is table. In it, user can select a few rows. I update the view as soon as the user clicks on any row since I don't want the UI to be slow. This updating is done by a logic which runs in the controller thread below. At the same time, the controller will update the model data too, which takes place in a different thread. i.e., controller puts the query in a queue, which is then executed by the model thread - which is a single-threaded interface. As soon as the query executes, controller will get a signal. Now, In order to keep the view and model synchronized, I will update the view again based on the return value of the query (the data returned by model) - even though I updated the view already for that user action. But, I am facing issues because, its taking a lot of time for the model to return the result, by that time user would have performed multiple clicks. So, as a result of updating the view again based on the information from model, the view sometimes goes back to the state in which the previous clicks were made (Suppose user clicks thrice on different rows. I update the view as soon as the click happens. Also, I update the view when I get data back from the model - which is supposed to be same as the already updated state of the view. Now, when the user clicks third time, I get data for the first click from model. As a result, view goes back to a state which is generated by the first click) Is there any way to handle such a synchronization issue?

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• Separate update and render

  - by NSAddict

  I'm programming a simple Snake in Java. I'm a complete newbie when it comes to Java and Game Developing, so please bear with me ;) Until now, I have been using a UI thread, as well as a update-thread. The update thread just set the position, set the GameObjects, and so on. I didn't think much of concurrency, but now I've come to a problem. I wanted to modify the ArrayList<GameObject>, but it throws a java.util.ConcurrentModificationException. With a little research I found out that this happens because the two threads are trying to access the variables at the same time. But I didn't really find a way to prevent this. I thought about copying the array and swapping them out when the rendering is finished, but I would have to deep-copy them, which isn't really the best solution in my opinion. It probably eats up more CPU resources than a single-threaded game. Are there any other ways to prevent this? Thanks a lot for your help!

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