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• are simultaneous reads of a variable thread-safe?

  - by Dasuraga

  Assuming that the variable isn't in any risk of being modified during the reads, are there any inherent problems in a variable being read by 2 or more threads at the same time?

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• Is is necessary to create a Mutex for a read-only thread and a write-only thread?

  - by httpinterpret

  There are 2 threads,one only reads the signal,the other only sets the signal. Is it necessary to create a mutex for signal and the reason?

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• Why thread started by ScheduledExecutorService.schedule() never quits?

  - by moonese

  If I create a scheduled task by calling ScheduledExecutorService.schedule(), it never quits after execution, is it a JDK bug, or I just miss something? note: doSomething() is empty method below. public static void doSomething() { } public static void main(String[] args) { ScheduledFuture scheduleFuture = Executors.newSingleThreadScheduledExecutor().schedule(new Callable() { public Void call() { try { doSomething(); } catch (Exception e) { e.printStackTrace(); } return null; } }, 1, TimeUnit.SECONDS); }

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• How to schedule heavy work for later display for Listviews?

  - by Pentium10

  I have a listview with 200 items. I use a custom view for each row. There is a code that takes some time to calculate, and because of this the list hangs out on scrolling and loads in slow (2-3sec). I have subclassed SimpleCursorAdapter, and using Filterable and SectionIndexer. I have in mind to show initially the name of the record, and put in a thread the calculation, and will show up later when it's done. How do I push back some work, and later update the listview to include the calculated data? This should show up on fly without user interaction.

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• glitchy stuttery iphone game loop

  - by Adam

  This is a problem I've been trying to solve for a few days now, and I've looked at the various solutions on stackoverflow and nothing has really seemed to work for me. I'm making an iPhone game with OpenGLES graphics and accelerometer input, at this point it's very simple, but the rendering is already pretty bad... it stutters and seems to jump back or forward in time. It doesn't happen a lot, but it happens enough to be a problem. I mean, who wants to play a game where a bullet gets magically transported into the player, and then it's game over? No one. I've tried using NSTimer for the game loop, I've tried using a separate thread (with a frame rate and continuously) I've tried using different frame rates, from 30FPS to 60FPS (It seems to have a max frame rate around 45FPS, but no problems at 30FPS) I've tried using timeIntervalSince1970 and CFGetAbsoluteTime to measure loop time, with no noticeable diffence Anyone have any ideas on what is the best way to get this looking better? One of the posts I've read suggested running the simulation at a fixed frame rate and then just render as fast as possible, does that seem like a good idea?

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• PHP database simulation

  - by Emdiesse

  I have a PHP script that works by calling items from a database based upon the time they were placed in there and it deletes them if they are older than 5 minutes. Basically, I want to now simulate what would happen if this database was being updated regularly. So I was considering sticking in some code that loads an XML file then goes through and parses that into the database based upon the time data located within a node of the xml data... but the problem there is I want it to continually loop through an enter this data so it'll never actually run the other processes So I was thinking of having another PHP script do that that could do this independantly of the php script that is going to display this data... In theory: I am looking to have a button that I can press and it will then run some php code to load up an XML file from a directory on my web server and then iterate though the data sending the data, to a database, based upon the time within a node in the PHP script and when the script was first called So back to my page that displayed the data... if I continually hit refresh it will contain different results each time because data is being added by the other process and this php script removes the older data when it is refreshed Any information on this? Is there a way I can silently, and safely, run a php script without it being loaded into a browser... like a thread!?

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• How to use boost::bind with non-copyable params, for example boost::promise ?

  - by zhengxi

  Some C++ objects have no copy constructor, but have move constructor. For example, boost::promise. How can I bind those objects using their move constructors ? #include <boost/thread.hpp> void fullfil_1(boost::promise<int>& prom, int x) { prom.set_value(x); } boost::function<void()> get_functor() { // boost::promise is not copyable, but movable boost::promise<int> pi; // compilation error boost::function<void()> f_set_one = boost::bind(&fullfil_1, pi, 1); // compilation error as well boost::function<void()> f_set_one = boost::bind(&fullfil_1, std::move(pi), 1); // PS. I know, it is possible to bind a pointer to the object instead of // the object itself. But it is weird solution, in this case I will have // to take cake about lifetime of the object instead of delegating that to // boost::bind (by moving object into boost::function object) // // weird: pi will be destroyed on leaving the scope boost::function<void()> f_set_one = boost::bind(&fullfil_1, boost::ref(pi), 1); return f_set_one; }

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• notify listener inside or outside inner synchronization

  - by Jary Zeels

  Hello all, I am struggling with a decision. I am writing a thread-safe library/API. Listeners can be registered, so the client is notified when something interesting happens. Which of the two implementations is most common? class MyModule { protected Listener listener; protected void somethingHappens() { synchronized(this) { ... do useful stuff ... listener.notify(); } } } or class MyModule { protected Listener listener; protected void somethingHappens() { Listener l = null; synchronized(this) { ... do useful stuff ... l = listener; } l.notify(); } } In the first implementation, the listener is notified inside the synchronization. In the second implementation, this is done outside the synchronization. I feel that the second one is advised, as it makes less room for potential deadlocks. But I am having trouble to convince myself. A downside of the second imlementation is that the client might receive 'incorrect' notifications, which happens if it accessed the module prior to the l.notify() statement. thanks a lot

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• problem with implementing a simple work queue

  - by John Deerikio

  Hi all, I am having troubles with implementing a simple work queue. Doing some analysis, I am facing a subtle problem. The work queue is backed by a regular linked list. The code looks like this (simplified): 0. while (true) 1. while (enabled == true) 2. acquire lock on the list and get the next action to be executed (blocking operation) (store it in a local variable) 3. execute the action (outside the lock on the list on previous line) 4. get lock on this work queue 5. wait until this work queue has been notified (triggered when setEnabled(true) has been callled) The setEnabled(e) operation looks like this (simplified): enabled = e if (enabled == true) acquire lock on this work queue and do notify() Although this works, there is a condition in which a deadlock occurs. It happens in the following rare situation: while an action is being executed, setEnabled(false) is called just before step (4) is entered, setEnabled(true) is called now step (5) keeps waiting forever, because this work queue has already been notified How do I solve this? I have been looking at this for some time, but I cannot come up with a solution. Please note I am fairly new to thread synchronization. Thanks a lot.

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• Timer in java ,time difference problem

  - by javatechi

  I want to create a timer for my app. The sample code is shown below. When the method datetwo() is called the same time in milliseconds is shown as there in the main method. Please help me out with this import java.util.Date; import java.util.Timer; public class TimerChe { Timer timer; static Date date = new Date(); static Date date2 = new Date(); public static void timerMethod(){ new Thread() { public void run() { try { while (true) { sleep(10000); datetwo(); } } catch (InterruptedException ex) { } } }.start(); } public static void datetwo() { System.out.println ("OK, It's time to do something!") ; System.out.println("The Time is " + date2.getTime() + " milliseconds since 1970/01/01"); } public static void main(String args[]) throws Exception { System.out.println("The Time is " + date.getTime() + " milliseconds since 1970/01/01" ); System.out.println ("Schedule something to do in the mean time.") ; timerMethod(); } }

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• java Sockets and Threads Problem

  - by vs4vijay

  I am doin a Some Socket Programing Stuff in Java.. Here i have created a button(Create Server)..and when i click it ,it starts server...but i want to change the button name to (Stop Server) after Starting the server... so i did this.. but when i press start server it starts and the button name remains the same... and when a client gets connected to it ,then it change the name to stop server... tell me whats the wrong with this code?? Here is My a SomePart Of Code... public void actionPerformed(ActionEvent ex) { if(ex.getActionCommand() == "CreateServer") { bt1.setText("Stop Server"); bt2.setEnabled(false); b5.setText("Server Started On Port " + tf2.getText()); System.out.println("Server started 1"); create(Integer.parseInt(tf2.getText())); //my func. to create server System.out.println("Server started 2"); } } and my create() fucn. contains some sockets and thread...so tell me what the problem...

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• Why is UITableView not reloading (even on the main thread)?

  - by radesix

  I have two programs that basically do the same thing. They read an XML feed and parse the elements. The design of both programs is to use an asynchronous NSURLConnection to get the data then to spawn a new thread to handle the parsing. As batches of 5 items are parsed it calls back to the main thread to reload the UITableView. My issue is it works fine in one program, but not the other. I know that the parsing is actually occuring on the background thread and I know that [tableView reloadData] is executing on the main thread; however, it doesn't reload the table until all parsing is complete. I'm stumped. As far as I can tell... both programs are structured exactly the same way. Here is some code from the app that isn't working correctly. - (void)startConnectionWithURL:(NSString *)feedURL feedList:(NSMutableArray *)list { self.feedList = list; // Use NSURLConnection to asynchronously download the data. This means the main thread will not be blocked - the // application will remain responsive to the user. // // IMPORTANT! The main thread of the application should never be blocked! Also, avoid synchronous network access on any thread. // NSURLRequest *feedURLRequest = [NSURLRequest requestWithURL:[NSURL URLWithString:feedURL]]; self.bloggerFeedConnection = [[[NSURLConnection alloc] initWithRequest:feedURLRequest delegate:self] autorelease]; // Test the validity of the connection object. The most likely reason for the connection object to be nil is a malformed // URL, which is a programmatic error easily detected during development. If the URL is more dynamic, then you should // implement a more flexible validation technique, and be able to both recover from errors and communicate problems // to the user in an unobtrusive manner. NSAssert(self.bloggerFeedConnection != nil, @"Failure to create URL connection."); // Start the status bar network activity indicator. We'll turn it off when the connection finishes or experiences an error. [UIApplication sharedApplication].networkActivityIndicatorVisible = YES; } - (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response { self.bloggerData = [NSMutableData data]; } - (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data { [bloggerData appendData:data]; } - (void)connectionDidFinishLoading:(NSURLConnection *)connection { self.bloggerFeedConnection = nil; [UIApplication sharedApplication].networkActivityIndicatorVisible = NO; // Spawn a thread to fetch the link data so that the UI is not blocked while the application parses the XML data. // // IMPORTANT! - Don't access UIKit objects on secondary threads. // [NSThread detachNewThreadSelector:@selector(parseFeedData:) toTarget:self withObject:bloggerData]; // farkData will be retained by the thread until parseFarkData: has finished executing, so we no longer need // a reference to it in the main thread. self.bloggerData = nil; } If you read this from the top down you can see when the NSURLConnection is finished I detach a new thread and call parseFeedData. - (void)parseFeedData:(NSData *)data { // You must create a autorelease pool for all secondary threads. NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init]; self.currentParseBatch = [NSMutableArray array]; self.currentParsedCharacterData = [NSMutableString string]; self.feedList = [NSMutableArray array]; // // It's also possible to have NSXMLParser download the data, by passing it a URL, but this is not desirable // because it gives less control over the network, particularly in responding to connection errors. // NSXMLParser *parser = [[NSXMLParser alloc] initWithData:data]; [parser setDelegate:self]; [parser parse]; // depending on the total number of links parsed, the last batch might not have been a "full" batch, and thus // not been part of the regular batch transfer. So, we check the count of the array and, if necessary, send it to the main thread. if ([self.currentParseBatch count] > 0) { [self performSelectorOnMainThread:@selector(addLinksToList:) withObject:self.currentParseBatch waitUntilDone:NO]; } self.currentParseBatch = nil; self.currentParsedCharacterData = nil; [parser release]; [pool release]; } In the did end element delegate I check to see that 5 items have been parsed before calling the main thread to perform the update. - (void)parser:(NSXMLParser *)parser didEndElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qName { if ([elementName isEqualToString:kItemElementName]) { [self.currentParseBatch addObject:self.currentItem]; parsedItemsCounter++; if (parsedItemsCounter % kSizeOfItemBatch == 0) { [self performSelectorOnMainThread:@selector(addLinksToList:) withObject:self.currentParseBatch waitUntilDone:NO]; self.currentParseBatch = [NSMutableArray array]; } } // Stop accumulating parsed character data. We won't start again until specific elements begin. accumulatingParsedCharacterData = NO; } - (void)addLinksToList:(NSMutableArray *)links { [self.feedList addObjectsFromArray:links]; // The table needs to be reloaded to reflect the new content of the list. if (self.viewDelegate != nil && [self.viewDelegate respondsToSelector:@selector(parser:didParseBatch:)]) { [self.viewDelegate parser:self didParseBatch:links]; } } Finally, the UIViewController delegate: - (void)parser:(XMLFeedParser *)parser didParseBatch:(NSMutableArray *)parsedBatch { NSLog(@"parser:didParseBatch:"); [self.selectedBlogger.feedList addObjectsFromArray:parsedBatch]; [self.tableView reloadData]; } If I write to the log when my view controller delegate fires to reload the table and when cellForRowAtIndexPath fires as it's rebuilding the table then the log looks something like this: parser:didParseBatch: parser:didParseBatch: tableView:cellForRowAtIndexPath tableView:cellForRowAtIndexPath tableView:cellForRowAtIndexPath tableView:cellForRowAtIndexPath tableView:cellForRowAtIndexPath parser:didParseBatch: parser:didParseBatch: parser:didParseBatch: tableView:cellForRowAtIndexPath tableView:cellForRowAtIndexPath tableView:cellForRowAtIndexPath tableView:cellForRowAtIndexPath tableView:cellForRowAtIndexPath parser:didParseBatch: tableView:cellForRowAtIndexPath tableView:cellForRowAtIndexPath tableView:cellForRowAtIndexPath tableView:cellForRowAtIndexPath tableView:cellForRowAtIndexPath parser:didParseBatch: parser:didParseBatch: parser:didParseBatch: parser:didParseBatch: tableView:cellForRowAtIndexPath tableView:cellForRowAtIndexPath tableView:cellForRowAtIndexPath tableView:cellForRowAtIndexPath tableView:cellForRowAtIndexPath Clearly, the tableView is not reloading when I tell it to every time. The log from the app that works correctly looks like this: parser:didParseBatch: tableView:cellForRowAtIndexPath tableView:cellForRowAtIndexPath tableView:cellForRowAtIndexPath tableView:cellForRowAtIndexPath tableView:cellForRowAtIndexPath parser:didParseBatch: tableView:cellForRowAtIndexPath tableView:cellForRowAtIndexPath tableView:cellForRowAtIndexPath tableView:cellForRowAtIndexPath tableView:cellForRowAtIndexPath parser:didParseBatch: tableView:cellForRowAtIndexPath tableView:cellForRowAtIndexPath tableView:cellForRowAtIndexPath tableView:cellForRowAtIndexPath tableView:cellForRowAtIndexPath parser:didParseBatch: tableView:cellForRowAtIndexPath tableView:cellForRowAtIndexPath tableView:cellForRowAtIndexPath tableView:cellForRowAtIndexPath tableView:cellForRowAtIndexPath parser:didParseBatch: tableView:cellForRowAtIndexPath tableView:cellForRowAtIndexPath tableView:cellForRowAtIndexPath tableView:cellForRowAtIndexPath tableView:cellForRowAtIndexPath

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• ArrayAdapter need to be clear even i am creating a new one

  - by Roi

  Hello I'm having problems understanding how the ArrayAdapter works. My code is working but I dont know how.(http://amy-mac.com/images/2013/code_meme.jpg) I have my activity, inside it i have 2 private classes.: public class MainActivity extends Activity { ... private void SomePrivateMethod(){ autoCompleteTextView.setAdapter(new ArrayAdapter<String>(this, android.R.layout.simple_spinner_dropdown_item, new ArrayList<String>(Arrays.asList("")))); autoCompleteTextView.addTextChangedListener(new MyTextWatcher()); } ... private class MyTextWatcher implements TextWatcher { ... } private class SearchAddressTask extends AsyncTask<String, Void, String[]> { ... } } Now inside my textwatcher class i call the search address task: @Override public void afterTextChanged(Editable s) { new SearchAddressTask().execute(s.toString()); } So far so good. In my SearchAddressTask I do some stuff on doInBackground() that returns the right array. On the onPostExecute() method i try to just modify the AutoCompleteTextView adapter to add the values from the array obtained in doInBackground() but the adapter cannot be modified: NOT WORKING CODE: protected void onPostExecute(String[] addressArray) { ArrayAdapter<String> adapter = (ArrayAdapter<String>) autoCompleteDestination.getAdapter(); adapter.clear(); adapter.addAll(new ArrayList<String>(Arrays.asList(addressArray))); adapter.notifyDataSetChanged(); Log.d("SearchAddressTask", "adapter isEmpty : " + adapter.isEmpty()); // Returns true!!??! } I dont get why this is not working. Even if i run it on UI Thread... I kept investigating, if i recreate the arrayAdapter, is working in the UI (Showing the suggestions), but i still need to clear the old adapter: WORKING CODE: protected void onPostExecute(String[] addressArray) { ArrayAdapter<String> adapter = (ArrayAdapter<String>) autoCompleteDestination.getAdapter(); adapter.clear(); autoCompleteDestination.setAdapter(new ArrayAdapter<String>(NewDestinationActivity.this,android.R.layout.simple_spinner_dropdown_item, new ArrayList<String>(Arrays.asList(addressArray)))); //adapter.notifyDataSetChanged(); // no needed Log.d("SearchAddressTask", "adapter isEmpty : " + adapter.isEmpty()); // keeps returning true!!??! } So my question is, what is really happening with this ArrayAdapter? why I cannot modify it in my onPostExecute()? Why is working in the UI if i am recreating the adapter? and why i need to clear the old adapter then? I dont know there are so many questions that I need some help in here!! Thanks!!

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• Why boost::recursive_mutex is not working as expected?

  - by Kjir

  I have a custom class that uses boost mutexes and locks like this (only relevant parts): template<class T> class FFTBuf { public: FFTBuf(); [...] void lock(); void unlock(); private: T *_dst; int _siglen; int _processed_sums; int _expected_sums; int _assigned_sources; bool _written; boost::recursive_mutex _mut; boost::unique_lock<boost::recursive_mutex> _lock; }; template<class T> FFTBuf<T>::FFTBuf() : _dst(NULL), _siglen(0), _expected_sums(1), _processed_sums(0), _assigned_sources(0), _written(false), _lock(_mut, boost::defer_lock_t()) { } template<class T> void FFTBuf<T>::lock() { std::cerr << "Locking" << std::endl; _lock.lock(); std::cerr << "Locked" << std::endl; } template<class T> void FFTBuf<T>::unlock() { std::cerr << "Unlocking" << std::endl; _lock.unlock(); } If I try to lock more than once the object from the same thread, I get an exception (lock_error): #include "fft_buf.hpp" int main( void ) { FFTBuf<int> b( 256 ); b.lock(); b.lock(); b.unlock(); b.unlock(); return 0; } This is the output: sb@dex $ ./src/test Locking Locked Locking terminate called after throwing an instance of 'boost::lock_error' what(): boost::lock_error zsh: abort ./src/test Why is this happening? Am I understanding some concept incorrectly?

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• JBoss 7.1.1 + Spring 3.1 + JPA 2 (Hibernate 3.6.8) > Cannot parse beans.xml

  - by Mashrur

  Trying to deploy a JSF 2 app with Spring 3.1 + JPA 2 (Hibernte 3.6.8) into JBoss 7.1.1 AS. The app was working fine on tomcat 7. Now, I have already added and changed some configurations. Added jboss-deployment-structure.xml <jboss-deployment-structure xmlns="urn:jboss:deployment-structure:1.1"> <deployment> <exclusions> <module name="org.apache.log4j" /> <module name="javax.faces.api" slot="main"/> <module name="com.sun.jsf-impl" slot="main"/> <module name="org.hibernate"/> <module name="org.javassist" /> <module name="javaee.api" /> <module name="org.hibernate.validator" /> <module name="org.jboss.as.web" /> <module name="org.jboss.logging" /> <module name="javax.persistence.api" /> <module name="org.jboss.interceptor" /> </exclusions> </deployment> </jboss-deployment-structure> 2. Inside web.xml added these lines: <persistence-unit-ref> <persistence-unit-ref-name>persistence/persistenceUnit</persistence-unit-ref-name> <persistence-unit-name>persistenceUnit</persistence-unit-name> </persistence-unit-ref> 3. Inside applicationContext.xml, changed bean definition for entityManagerFactory by adding this property <property name="persistenceXmlLocation" value="classpath*:META-INF/persistence.xml"/> Now, do I still need to do something more than these which is obvious to you? Because, while I am trying to deploy it from eclipse indigo SR2, getting this 14:10:32,046 INFO [org.jboss.modules] JBoss Modules version 1.1.1.GA 14:10:33,054 INFO [org.jboss.msc] JBoss MSC version 1.0.2.GA 14:10:33,200 INFO [org.jboss.as] JBAS015899: JBoss AS 7.1.1.Final "Brontes" starting 14:10:36,375 INFO [org.xnio] XNIO Version 3.0.3.GA 14:10:36,384 INFO [org.jboss.as.server] JBAS015888: Creating http management service using socket-binding (management-http) 14:10:36,432 INFO [org.xnio.nio] XNIO NIO Implementation Version 3.0.3.GA 14:10:36,462 INFO [org.jboss.remoting] JBoss Remoting version 3.2.3.GA 14:10:36,587 INFO [org.jboss.as.logging] JBAS011502: Removing bootstrap log handlers 14:10:36,714 INFO [org.jboss.as.security] (ServerService Thread Pool -- 44) JBAS013101: Activating Security Subsystem 14:10:36,735 INFO [org.jboss.as.naming] (MSC service thread 1-2) JBAS011802: Starting Naming Service 14:10:37,043 INFO [org.jboss.as.mail.extension] (MSC service thread 1-6) JBAS015400: Bound mail session [java:jboss/mail/Default] 14:10:37,208 INFO [org.jboss.as.connector] (MSC service thread 1-7) JBAS010408: Starting JCA Subsystem (JBoss IronJacamar 1.0.9.Final) 14:10:37,295 INFO [org.jboss.as.security] (MSC service thread 1-7) JBAS013100: Current PicketBox version=4.0.7.Final 14:10:37,740 INFO [org.jboss.as.connector.subsystems.datasources] (ServerService Thread Pool -- 27) JBAS010403: Deploying JDBC-compliant driver class org.h2.Driver (version 1.3) 14:10:38,792 INFO [org.jboss.ws.common.management.AbstractServerConfig] (MSC service thread 1-3) JBoss Web Services - Stack CXF Server 4.0.2.GA 14:10:38,833 INFO [org.apache.coyote.http11.Http11Protocol] (MSC service thread 1-2) Starting Coyote HTTP/1.1 on http-localhost-127.0.0.1-8080 14:10:39,534 INFO [org.jboss.as.server.deployment.scanner] (MSC service thread 1-1) JBAS015012: Started FileSystemDeploymentService for directory F:\work\softwares\Application Servers\JBoss\jboss-as-7.1.1.Final\jboss-as-7.1.1.Final\standalone\deployments 14:10:39,618 INFO [org.jboss.as.remoting] (MSC service thread 1-3) JBAS017100: Listening on localhost/127.0.0.1:4447 14:10:39,623 INFO [org.jboss.as.remoting] (MSC service thread 1-2) JBAS017100: Listening on /127.0.0.1:9999 14:10:39,698 INFO [org.jboss.as.server.deployment.scanner] (DeploymentScanner-threads - 1) JBAS015014: Re-attempting failed deployment treasury.war 14:10:39,706 INFO [org.jboss.as.server.deployment.scanner] (DeploymentScanner-threads - 1) JBAS015003: Found com.misl.treasury.ui.war in deployment directory. To trigger deployment create a file called com.misl.treasury.ui.war.dodeploy 14:10:40,105 INFO [org.jboss.as.connector.subsystems.datasources] (MSC service thread 1-2) JBAS010400: Bound data source [java:jboss/datasources/ExampleDS] 14:10:40,399 INFO [org.jboss.as.server.deployment] (MSC service thread 1-1) JBAS015876: Starting deployment of "com.misl.treasury.ui.war" 14:10:40,405 INFO [org.jboss.as.server.deployment] (MSC service thread 1-7) JBAS015876: Starting deployment of "treasury.war" 14:10:55,283 WARN [org.jboss.as.server.deployment] (MSC service thread 1-7) JBAS015893: Encountered invalid class name 'com.sun.faces.vendor.Tomcat6InjectionProvider:org.apache.catalina.util.DefaultAnnotationProcessor' for service type 'com.sun.faces.spi.injectionprovider' 14:10:55,289 WARN [org.jboss.as.server.deployment] (MSC service thread 1-7) JBAS015893: Encountered invalid class name 'com.sun.faces.vendor.Jetty6InjectionProvider:org.mortbay.jetty.plus.annotation.InjectionCollection' for service type 'com.sun.faces.spi.injectionprovider' 14:10:55,428 INFO [org.jboss.as.jpa] (MSC service thread 1-7) JBAS011401: Read persistence.xml for persistenceUnit 14:10:55,843 WARN [org.jboss.as.server.deployment] (MSC service thread 1-4) JBAS015893: Encountered invalid class name 'com.sun.faces.vendor.Tomcat6InjectionProvider:org.apache.catalina.util.DefaultAnnotationProcessor' for service type 'com.sun.faces.spi.injectionprovider' 14:10:55,849 WARN [org.jboss.as.server.deployment] (MSC service thread 1-4) JBAS015893: Encountered invalid class name 'com.sun.faces.vendor.Jetty6InjectionProvider:org.mortbay.jetty.plus.annotation.InjectionCollection' for service type 'com.sun.faces.spi.injectionprovider' 14:10:56,010 ERROR [org.jboss.msc.service.fail] (MSC service thread 1-2) MSC00001: Failed to start service jboss.deployment.unit."com.misl.treasury.ui.war".POST_MODULE: org.jboss.msc.service.StartException in service jboss.deployment.unit."com.misl.treasury.ui.war".POST_MODULE: Failed to process phase POST_MODULE of deployment "com.misl.treasury.ui.war" at org.jboss.as.server.deployment.DeploymentUnitPhaseService.start(DeploymentUnitPhaseService.java:119) [jboss-as-server-7.1.1.Final.jar:7.1.1.Final] at org.jboss.msc.service.ServiceControllerImpl$StartTask.startService(ServiceControllerImpl.java:1811) [jboss-msc-1.0.2.GA.jar:1.0.2.GA] at org.jboss.msc.service.ServiceControllerImpl$StartTask.run(ServiceControllerImpl.java:1746) [jboss-msc-1.0.2.GA.jar:1.0.2.GA] at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886) [rt.jar:1.6.0_23] at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908) [rt.jar:1.6.0_23] at java.lang.Thread.run(Thread.java:662) [rt.jar:1.6.0_23] Caused by: java.lang.NoClassDefFoundError: javax/servlet/ServletOutputStream at java.lang.Class.getDeclaredConstructors0(Native Method) [rt.jar:1.6.0_23] at java.lang.Class.privateGetDeclaredConstructors(Class.java:2389) [rt.jar:1.6.0_23] at java.lang.Class.getConstructor0(Class.java:2699) [rt.jar:1.6.0_23] at java.lang.Class.getConstructor(Class.java:1657) [rt.jar:1.6.0_23] at org.jboss.as.web.deployment.jsf.JsfManagedBeanProcessor.deploy(JsfManagedBeanProcessor.java:108) at org.jboss.as.server.deployment.DeploymentUnitPhaseService.start(DeploymentUnitPhaseService.java:113) [jboss-as-server-7.1.1.Final.jar:7.1.1.Final] ... 5 more Caused by: java.lang.ClassNotFoundException: javax.servlet.ServletOutputStream from [Module "deployment.com.misl.treasury.ui.war:main" from Service Module Loader] at org.jboss.modules.ModuleClassLoader.findClass(ModuleClassLoader.java:190) at org.jboss.modules.ConcurrentClassLoader.performLoadClassUnchecked(ConcurrentClassLoader.java:468) at org.jboss.modules.ConcurrentClassLoader.performLoadClassChecked(ConcurrentClassLoader.java:456) at org.jboss.modules.ConcurrentClassLoader.performLoadClassChecked(ConcurrentClassLoader.java:423) at org.jboss.modules.ConcurrentClassLoader.performLoadClass(ConcurrentClassLoader.java:398) at org.jboss.modules.ConcurrentClassLoader.loadClass(ConcurrentClassLoader.java:120) ... 11 more 14:10:56,628 ERROR [org.jboss.msc.service.fail] (MSC service thread 1-4) MSC00001: Failed to start service jboss.deployment.unit."treasury.war".PARSE: org.jboss.msc.service.StartException in service jboss.deployment.unit."treasury.war".PARSE: Failed to process phase PARSE of deployment "treasury.war" at org.jboss.as.server.deployment.DeploymentUnitPhaseService.start(DeploymentUnitPhaseService.java:119) [jboss-as-server-7.1.1.Final.jar:7.1.1.Final] at org.jboss.msc.service.ServiceControllerImpl$StartTask.startService(ServiceControllerImpl.java:1811) [jboss-msc-1.0.2.GA.jar:1.0.2.GA] at org.jboss.msc.service.ServiceControllerImpl$StartTask.run(ServiceControllerImpl.java:1746) [jboss-msc-1.0.2.GA.jar:1.0.2.GA] at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886) [rt.jar:1.6.0_23] at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908) [rt.jar:1.6.0_23] at java.lang.Thread.run(Thread.java:662) [rt.jar:1.6.0_23] Caused by: org.jboss.as.server.deployment.DeploymentUnitProcessingException: SAXException parsing vfs:/F:/work/softwares/Application Servers/JBoss/jboss-as-7.1.1.Final/jboss-as-7.1.1.Final/bin/content/treasury.war/WEB-INF/beans.xml at org.jboss.as.weld.deployment.BeansXmlParser.parse(BeansXmlParser.java:100) at org.jboss.as.weld.deployment.processors.BeansXmlProcessor.parseBeansXml(BeansXmlProcessor.java:133) at org.jboss.as.weld.deployment.processors.BeansXmlProcessor.deploy(BeansXmlProcessor.java:97) at org.jboss.as.server.deployment.DeploymentUnitPhaseService.start(DeploymentUnitPhaseService.java:113) [jboss-as-server-7.1.1.Final.jar:7.1.1.Final] ... 5 more Caused by: org.xml.sax.SAXParseException: Premature end of file. at org.apache.xerces.util.ErrorHandlerWrapper.createSAXParseException(ErrorHandlerWrapper.java:196) at org.apache.xerces.util.ErrorHandlerWrapper.fatalError(ErrorHandlerWrapper.java:175) at org.apache.xerces.impl.XMLErrorReporter.reportError(XMLErrorReporter.java:394) at org.apache.xerces.impl.XMLErrorReporter.reportError(XMLErrorReporter.java:322) at org.apache.xerces.impl.XMLErrorReporter.reportError(XMLErrorReporter.java:281) at org.apache.xerces.impl.XMLScanner.reportFatalError(XMLScanner.java:1459) at org.apache.xerces.impl.XMLDocumentScannerImpl$PrologDispatcher.dispatch(XMLDocumentScannerImpl.java:903) at org.apache.xerces.impl.XMLDocumentFragmentScannerImpl.scanDocument(XMLDocumentFragmentScannerImpl.java:324) at org.apache.xerces.parsers.XML11Configuration.parse(XML11Configuration.java:845) at org.apache.xerces.parsers.XML11Configuration.parse(XML11Configuration.java:768) at org.apache.xerces.parsers.XMLParser.parse(XMLParser.java:108) at org.apache.xerces.parsers.AbstractSAXParser.parse(AbstractSAXParser.java:1196) at org.apache.xerces.jaxp.SAXParserImpl$JAXPSAXParser.parse(SAXParserImpl.java:555) at org.apache.xerces.jaxp.SAXParserImpl.parse(SAXParserImpl.java:289) at org.jboss.as.weld.deployment.BeansXmlParser.parse(BeansXmlParser.java:94) ... 8 more 14:10:56,670 INFO [org.jboss.as] (MSC service thread 1-1) JBAS015951: Admin console listening on http://127.0.0.1:9990 14:10:56,672 ERROR [org.jboss.as] (MSC service thread 1-1) JBAS015875: JBoss AS 7.1.1.Final "Brontes" started (with errors) in 25527ms - Started 143 of 222 services (2 services failed or missing dependencies, 76 services are passive or on-demand) 14:10:56,671 INFO [org.jboss.as.server] (DeploymentScanner-threads - 2) JBAS015871: Deploy of deployment "treasury.war" was rolled back with no failure message 14:10:56,679 INFO [org.jboss.as.server] (DeploymentScanner-threads - 2) JBAS015870: Deploy of deployment "com.misl.treasury.ui.war" was rolled back with failure message {"JBAS014671: Failed services" => {"jboss.deployment.unit.\"com.misl.treasury.ui.war\".POST_MODULE" => "org.jboss.msc.service.StartException in service jboss.deployment.unit.\"com.misl.treasury.ui.war\".POST_MODULE: Failed to process phase POST_MODULE of deployment \"com.misl.treasury.ui.war\""}} 14:10:56,851 INFO [org.jboss.as.server.deployment] (MSC service thread 1-8) JBAS015877: Stopped deployment com.misl.treasury.ui.war in 172ms 14:10:57,068 INFO [org.jboss.as.server.deployment] (MSC service thread 1-7) JBAS015877: Stopped deployment treasury.war in 395ms 14:10:57,070 INFO [org.jboss.as.controller] (DeploymentScanner-threads - 2) JBAS014774: Service status report JBAS014777: Services which failed to start: service jboss.deployment.unit."treasury.war".PARSE: org.jboss.msc.service.StartException in service jboss.deployment.unit."treasury.war".PARSE: Failed to process phase PARSE of deployment "treasury.war" service jboss.deployment.unit."com.misl.treasury.ui.war".POST_MODULE: org.jboss.msc.service.StartException in service jboss.deployment.unit."com.misl.treasury.ui.war".POST_MODULE: Failed to process phase POST_MODULE of deployment "com.misl.treasury.ui.war" 14:10:57,079 ERROR [org.jboss.as.server.deployment.scanner] (DeploymentScanner-threads - 1) {"JBAS014653: Composite operation failed and was rolled back. Steps that failed:" => {"Operation step-2" => {"JBAS014671: Failed services" => {"jboss.deployment.unit.\"com.misl.treasury.ui.war\".POST_MODULE" => "org.jboss.msc.service.StartException in service jboss.deployment.unit.\"com.misl.treasury.ui.war\".POST_MODULE: Failed to process phase POST_MODULE of deployment \"com.misl.treasury.ui.war\""}}}} 14:10:57,087 ERROR [org.jboss.as.server.deployment.scanner] (DeploymentScanner-threads - 1) JBAS014654: Composite operation was rolled back And by the way, JBOSS_HOME\modules\javax\api\main folder only contains a module.xml, no jars. Tried to add jboss-servlet-api_3.0_spec-1.0.0.Final.jar file in that directory and updated module.xml too. But, it shows a very long trail of stacktraces :) I have even removed beans.xml. No change. I have never tried JBoss before. Any help would be highly appreciated.

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• can i know the Thread runnable class attributes in java?

  - by dori naji

  probability this question have been asked before but i cant find anything in my searching mechanism. I am trying to create a multiple threads, in an array list but i want to retrieve them from an arraylist and filter them by the attribute of w1 i used in my code. any ideas ? w1 = new FirstWorker(ProductsList, OrdersList, s); FirstWorkerThread = new Thread(w1); ThreadArrayList.add(FirstWorkerThread); //I know i cant do the code below but i want to do that how ? for(Thread x : ThreadArrayList){ x.ProductsList } this is FirstWorker class import java.lang.String; import java.util.HashMap; /* * To change this template, choose Tools | Templates and open the template in * the editor. */ /** * * @author Dimitris */ public class FirstWorker extends Thread implements Runnable { private OrderList orderlist; private ProductList productlist; private String Worker; boolean Stop; private int speed = 1000; public FirstWorker(ProductList productlist, OrderList orderlist, String Worker) { this.productlist = productlist; this.orderlist = orderlist; this.Worker = Worker; this.Stop = true; } public void run() { if (Stop == true) { try { Thread.sleep(100); } catch (InterruptedException e) { } while (orderlist.returnLengthofOrder() != 0) { if (Thread.interrupted()) { System.out.println("I am in the thread inturrupt"); // We've been interrupted: no more crunching. return; } if (orderlist.getDone() == true) { } else if (orderlist.getDone() == false) { orderlist.setDoneTrue(); orderlist.Purchased(Worker); orderlist.setDoneFalse(); try { Thread.sleep(this.speed); } catch (InterruptedException e) { return; } } } } } public void setWork() { Stop = false; } public void setSpeed(int speed) { this.speed = speed; } }

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• ASP.NET Asynchronous Pages and when to use them

  - by rajbk

  There have been several articles posted about using  asynchronous pages in ASP.NET but none of them go into detail as to when you should use them. I finally found a great post by Thomas Marquardt that explains the process in depth. He addresses a key misconception also: So, in your ASP.NET application, when should you perform work asynchronously instead of synchronously? Well, only 1 thread per CPU can execute at a time.  Did you catch that?  A lot of people seem to miss this point...only one thread executes at a time on a CPU. When you have more than this, you pay an expensive penalty--a context switch. However, if a thread is blocked waiting on work...then it makes sense to switch to another thread, one that can execute now.  It also makes sense to switch threads if you want work to be done in parallel as opposed to in series, but up until a certain point it actually makes much more sense to execute work in series, again, because of the expensive context switch. Pop quiz: If you have a thread that is doing a lot of computational work and using the CPU heavily, and this takes a while, should you switch to another thread? No! The current thread is efficiently using the CPU, so switching will only incur the cost of a context switch. Ok, well, what if you have a thread that makes an HTTP or SOAP request to another server and takes a long time, should you switch threads? Yes! You can perform the HTTP or SOAP request asynchronously, so that once the "send" has occurred, you can unwind the current thread and not use any threads until there is an I/O completion for the "receive". Between the "send" and the "receive", the remote server is busy, so locally you don't need to be blocking on a thread, but instead make use of the asynchronous APIs provided in .NET Framework so that you can unwind and be notified upon completion. Again, it only makes sense to switch threads if the benefit from doing so out weights the cost of the switch. Read more about it in these posts: Performing Asynchronous Work, or Tasks, in ASP.NET Applications http://blogs.msdn.com/tmarq/archive/2010/04/14/performing-asynchronous-work-or-tasks-in-asp-net-applications.aspx ASP.NET Thread Usage on IIS 7.0 and 6.0 http://blogs.msdn.com/tmarq/archive/2007/07/21/asp-net-thread-usage-on-iis-7-0-and-6-0.aspx   PS: I generally do not write posts that simply link to other posts but think it is warranted in this case.

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• Tomcat 7 taking ages to start up after upgrade

  - by Lawrence

  I recently updated my server installation from Tomcat 6 to Tomcat 7, in order to take advantage of better connection pooling. My project uses Hibernate, for object persistance, a Mysql 5.5.20 database, and memcached for caching. When I was using Tomcat 6, Tomcat would start in about 8 seconds. After moving to Tomcat 7, it now takes between 75 - 80 seconds to start (this is on a Macbook pro 15", core i7 2Ghz, 8Gb of RAM). The only thing that has really changed between during the move from Tomcat 6 to 7 has been my context.xml file, which controls the connection pooling information: <Context antiJARLocking="true" reloadable="true" path=""> <Resource name="jdbc/test-db" auth="Container" type="javax.sql.DataSource" factory="org.apache.tomcat.jdbc.pool.DataSourceFactory" testOnBorrow="true" testOnReturn="false" testWhileIdle="true" validationQuery="SELECT 1" validationQueryTimeout="20000" validationInterval="30000" timeBetweenEvictionRunsMillis="60000" logValidationErrors="true" autoReconnect="true" username="webuser" password="xxxxxxx" driverClassName="com.mysql.jdbc.Driver" url="jdbc:mysql://databasename.us-east-1.rds.amazonaws.com:3306/test-db" maxActive="15" minIdle="2" maxIdle="10" maxWait="10000" maxAge="7200000"/> </Context> Now, as you can see, the database is running on Amazon RDS (where our live servers are), and thus is about 200ms round trip time away from my machine. I have already checked that I have security permissions to that database from my machine, (and anyway, it connects after 75 secs, so it cant be that). My initial thought was that Tomcat 7 and hibernate are doing something weird (like pre-instantiating a bunch of connections or something), and the latency to the database is amplifying the effects. While trying to diagnose the problem, I used jstack to get a stack trace of the Tomcat 7 server while its doing its startup thing. Here is the stack trace... Full thread dump Java HotSpot(TM) 64-Bit Server VM (20.12-b01-434 mixed mode): "Attach Listener" daemon prio=9 tid=7fa4c0038800 nid=0x10c39a000 waiting on condition [00000000] java.lang.Thread.State: RUNNABLE "Abandoned connection cleanup thread" daemon prio=5 tid=7fa4bb810000 nid=0x10f3ba000 in Object.wait() [10f3b9000] java.lang.Thread.State: WAITING (on object monitor) at java.lang.Object.wait(Native Method) - waiting on <7f40a0070> (a java.lang.ref.ReferenceQueue$Lock) at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:118) - locked <7f40a0070> (a java.lang.ref.ReferenceQueue$Lock) at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:134) at com.mysql.jdbc.NonRegisteringDriver$1.run(NonRegisteringDriver.java:93) "PoolCleaner[545768040:1352724902327]" daemon prio=5 tid=7fa4be852800 nid=0x10e772000 in Object.wait() [10e771000] java.lang.Thread.State: TIMED_WAITING (on object monitor) at java.lang.Object.wait(Native Method) - waiting on <7f40c7c90> (a java.util.TaskQueue) at java.util.TimerThread.mainLoop(Timer.java:509) - locked <7f40c7c90> (a java.util.TaskQueue) at java.util.TimerThread.run(Timer.java:462) "localhost-startStop-1" daemon prio=5 tid=7fa4bd034800 nid=0x10d66b000 runnable [10d668000] java.lang.Thread.State: RUNNABLE at java.net.SocketInputStream.socketRead0(Native Method) at java.net.SocketInputStream.read(SocketInputStream.java:129) at com.mysql.jdbc.util.ReadAheadInputStream.fill(ReadAheadInputStream.java:114) at com.mysql.jdbc.util.ReadAheadInputStream.readFromUnderlyingStreamIfNecessary(ReadAheadInputStream.java:161) at com.mysql.jdbc.util.ReadAheadInputStream.read(ReadAheadInputStream.java:189) - locked <7f3673be0> (a com.mysql.jdbc.util.ReadAheadInputStream) at com.mysql.jdbc.MysqlIO.readFully(MysqlIO.java:3014) at com.mysql.jdbc.MysqlIO.reuseAndReadPacket(MysqlIO.java:3467) at com.mysql.jdbc.MysqlIO.reuseAndReadPacket(MysqlIO.java:3456) at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3997) at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:2468) at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:2629) at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2713) - locked <7f366a1c0> (a com.mysql.jdbc.JDBC4Connection) at com.mysql.jdbc.ConnectionImpl.configureClientCharacterSet(ConnectionImpl.java:1930) at com.mysql.jdbc.ConnectionImpl.initializePropsFromServer(ConnectionImpl.java:3571) at com.mysql.jdbc.ConnectionImpl.connectOneTryOnly(ConnectionImpl.java:2445) at com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2215) - locked <7f366a1c0> (a com.mysql.jdbc.JDBC4Connection) at com.mysql.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:813) at com.mysql.jdbc.JDBC4Connection.<init>(JDBC4Connection.java:47) at sun.reflect.GeneratedConstructorAccessor10.newInstance(Unknown Source) at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27) at java.lang.reflect.Constructor.newInstance(Constructor.java:513) at com.mysql.jdbc.Util.handleNewInstance(Util.java:411) at com.mysql.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:399) at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:334) at org.apache.tomcat.jdbc.pool.PooledConnection.connectUsingDriver(PooledConnection.java:278) at org.apache.tomcat.jdbc.pool.PooledConnection.connect(PooledConnection.java:182) at org.apache.tomcat.jdbc.pool.ConnectionPool.createConnection(ConnectionPool.java:699) at org.apache.tomcat.jdbc.pool.ConnectionPool.borrowConnection(ConnectionPool.java:631) at org.apache.tomcat.jdbc.pool.ConnectionPool.init(ConnectionPool.java:485) at org.apache.tomcat.jdbc.pool.ConnectionPool.<init>(ConnectionPool.java:143) at org.apache.tomcat.jdbc.pool.DataSourceProxy.pCreatePool(DataSourceProxy.java:116) - locked <7f34f0dc8> (a org.apache.tomcat.jdbc.pool.DataSource) at org.apache.tomcat.jdbc.pool.DataSourceProxy.createPool(DataSourceProxy.java:103) at org.apache.tomcat.jdbc.pool.DataSourceFactory.createDataSource(DataSourceFactory.java:539) at org.apache.tomcat.jdbc.pool.DataSourceFactory.getObjectInstance(DataSourceFactory.java:237) at org.apache.naming.factory.ResourceFactory.getObjectInstance(ResourceFactory.java:143) at javax.naming.spi.NamingManager.getObjectInstance(NamingManager.java:304) at org.apache.naming.NamingContext.lookup(NamingContext.java:843) at org.apache.naming.NamingContext.lookup(NamingContext.java:154) at org.apache.naming.NamingContext.lookup(NamingContext.java:831) at org.apache.naming.NamingContext.lookup(NamingContext.java:168) at org.apache.catalina.core.NamingContextListener.addResource(NamingContextListener.java:1061) at org.apache.catalina.core.NamingContextListener.createNamingContext(NamingContextListener.java:671) at org.apache.catalina.core.NamingContextListener.lifecycleEvent(NamingContextListener.java:270) at org.apache.catalina.util.LifecycleSupport.fireLifecycleEvent(LifecycleSupport.java:119) at org.apache.catalina.util.LifecycleBase.fireLifecycleEvent(LifecycleBase.java:90) at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5173) - locked <7f46b07f0> (a org.apache.catalina.core.StandardContext) at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150) - locked <7f46b07f0> (a org.apache.catalina.core.StandardContext) at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1559) at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1549) at java.util.concurrent.FutureTask$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:680) "Catalina-startStop-1" daemon prio=5 tid=7fa4b7a5e800 nid=0x10d568000 waiting on condition [10d567000] java.lang.Thread.State: WAITING (parking) at sun.misc.Unsafe.park(Native Method) - parking to wait for <7f480e970> (a java.util.concurrent.FutureTask$Sync) at java.util.concurrent.locks.LockSupport.park(LockSupport.java:156) at java.util.concurrent.locks.AbstractQueuedSynchronizer.parkAndCheckInterrupt(AbstractQueuedSynchronizer.java:811) at java.util.concurrent.locks.AbstractQueuedSynchronizer.doAcquireSharedInterruptibly(AbstractQueuedSynchronizer.java:969) at java.util.concurrent.locks.AbstractQueuedSynchronizer.acquireSharedInterruptibly(AbstractQueuedSynchronizer.java:1281) at java.util.concurrent.FutureTask$Sync.innerGet(FutureTask.java:218) at java.util.concurrent.FutureTask.get(FutureTask.java:83) at org.apache.catalina.core.ContainerBase.startInternal(ContainerBase.java:1123) - locked <7f453c630> (a org.apache.catalina.core.StandardHost) at org.apache.catalina.core.StandardHost.startInternal(StandardHost.java:800) - locked <7f453c630> (a org.apache.catalina.core.StandardHost) at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150) - locked <7f453c630> (a org.apache.catalina.core.StandardHost) at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1559) at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1549) 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$Worker.run(ThreadPoolExecutor.java:908) at java.lang.Thread.run(Thread.java:680) "GC Daemon" daemon prio=2 tid=7fa4b9912800 nid=0x10d465000 in Object.wait() [10d464000] java.lang.Thread.State: TIMED_WAITING (on object monitor) at java.lang.Object.wait(Native Method) - waiting on <7f4506d28> (a sun.misc.GC$LatencyLock) at sun.misc.GC$Daemon.run(GC.java:100) - locked <7f4506d28> (a sun.misc.GC$LatencyLock) "Low Memory Detector" daemon prio=5 tid=7fa4b480b800 nid=0x10c8ae000 runnable [00000000] java.lang.Thread.State: RUNNABLE "C2 CompilerThread1" daemon prio=9 tid=7fa4b480b000 nid=0x10c7ab000 waiting on condition [00000000] java.lang.Thread.State: RUNNABLE "C2 CompilerThread0" daemon prio=9 tid=7fa4b480a000 nid=0x10c6a8000 waiting on condition [00000000] java.lang.Thread.State: RUNNABLE "Signal Dispatcher" daemon prio=9 tid=7fa4b4809800 nid=0x10c5a5000 runnable [00000000] java.lang.Thread.State: RUNNABLE "Surrogate Locker Thread (Concurrent GC)" daemon prio=5 tid=7fa4b4808800 nid=0x10c4a2000 waiting on condition [00000000] java.lang.Thread.State: RUNNABLE "Finalizer" daemon prio=8 tid=7fa4b793f000 nid=0x10c297000 in Object.wait() [10c296000] java.lang.Thread.State: WAITING (on object monitor) at java.lang.Object.wait(Native Method) - waiting on <7f451c8f0> (a java.lang.ref.ReferenceQueue$Lock) at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:118) - locked <7f451c8f0> (a java.lang.ref.ReferenceQueue$Lock) at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:134) at java.lang.ref.Finalizer$FinalizerThread.run(Finalizer.java:159) "Reference Handler" daemon prio=10 tid=7fa4b793e000 nid=0x10c194000 in Object.wait() [10c193000] java.lang.Thread.State: WAITING (on object monitor) at java.lang.Object.wait(Native Method) - waiting on <7f452e168> (a java.lang.ref.Reference$Lock) at java.lang.Object.wait(Object.java:485) at java.lang.ref.Reference$ReferenceHandler.run(Reference.java:116) - locked <7f452e168> (a java.lang.ref.Reference$Lock) "main" prio=5 tid=7fa4b7800800 nid=0x104329000 waiting on condition [104327000] java.lang.Thread.State: WAITING (parking) at sun.misc.Unsafe.park(Native Method) - parking to wait for <7f480e9a0> (a java.util.concurrent.FutureTask$Sync) at java.util.concurrent.locks.LockSupport.park(LockSupport.java:156) at java.util.concurrent.locks.AbstractQueuedSynchronizer.parkAndCheckInterrupt(AbstractQueuedSynchronizer.java:811) at java.util.concurrent.locks.AbstractQueuedSynchronizer.doAcquireSharedInterruptibly(AbstractQueuedSynchronizer.java:969) at java.util.concurrent.locks.AbstractQueuedSynchronizer.acquireSharedInterruptibly(AbstractQueuedSynchronizer.java:1281) at java.util.concurrent.FutureTask$Sync.innerGet(FutureTask.java:218) at java.util.concurrent.FutureTask.get(FutureTask.java:83) at org.apache.catalina.core.ContainerBase.startInternal(ContainerBase.java:1123) - locked <7f451fd90> (a org.apache.catalina.core.StandardEngine) at org.apache.catalina.core.StandardEngine.startInternal(StandardEngine.java:302) - locked <7f451fd90> (a org.apache.catalina.core.StandardEngine) at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150) - locked <7f451fd90> (a org.apache.catalina.core.StandardEngine) at org.apache.catalina.core.StandardService.startInternal(StandardService.java:443) - locked <7f451fd90> (a org.apache.catalina.core.StandardEngine) at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150) - locked <7f453e810> (a org.apache.catalina.core.StandardService) at org.apache.catalina.core.StandardServer.startInternal(StandardServer.java:732) - locked <7f4506d58> (a [Lorg.apache.catalina.Service;) at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150) - locked <7f44f7ba0> (a org.apache.catalina.core.StandardServer) at org.apache.catalina.startup.Catalina.start(Catalina.java:684) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) at java.lang.reflect.Method.invoke(Method.java:597) at org.apache.catalina.startup.Bootstrap.start(Bootstrap.java:322) at org.apache.catalina.startup.Bootstrap.main(Bootstrap.java:451) "VM Thread" prio=9 tid=7fa4b7939800 nid=0x10c091000 runnable "Gang worker#0 (Parallel GC Threads)" prio=9 tid=7fa4b7802000 nid=0x10772b000 runnable "Gang worker#1 (Parallel GC Threads)" prio=9 tid=7fa4b7802800 nid=0x10782e000 runnable "Gang worker#2 (Parallel GC Threads)" prio=9 tid=7fa4b7803000 nid=0x107931000 runnable "Gang worker#3 (Parallel GC Threads)" prio=9 tid=7fa4b7804000 nid=0x107a34000 runnable "Gang worker#4 (Parallel GC Threads)" prio=9 tid=7fa4b7804800 nid=0x107b37000 runnable "Gang worker#5 (Parallel GC Threads)" prio=9 tid=7fa4b7805000 nid=0x107c3a000 runnable "Gang worker#6 (Parallel GC Threads)" prio=9 tid=7fa4b7805800 nid=0x107d3d000 runnable "Gang worker#7 (Parallel GC Threads)" prio=9 tid=7fa4b7806800 nid=0x107e40000 runnable "Concurrent Mark-Sweep GC Thread" prio=9 tid=7fa4b78e3800 nid=0x10bd0b000 runnable "Gang worker#0 (Parallel CMS Threads)" prio=9 tid=7fa4b78e2800 nid=0x10b305000 runnable "Gang worker#1 (Parallel CMS Threads)" prio=9 tid=7fa4b78e3000 nid=0x10b408000 runnable "VM Periodic Task Thread" prio=10 tid=7fa4b4815800 nid=0x10c9b1000 waiting on condition "Exception Catcher Thread" prio=10 tid=7fa4b7801800 nid=0x104554000 runnable JNI global references: 919 The only thing I can figure out from this is that it looks like the mysql jdbc drivers might have something to do with the long start up (the various stack traces I took during the start up process all pretty much look the same as this). Could anyone shed some light on what might be causing this? Have I done something dense in my context.xml? Is hibernate perhaps to blame?

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• Inside the Concurrent Collections: ConcurrentDictionary

  - by Simon Cooper

  Using locks to implement a thread-safe collection is rather like using a sledgehammer - unsubtle, easy to understand, and tends to make any other tool redundant. Unlike the previous two collections I looked at, ConcurrentStack and ConcurrentQueue, ConcurrentDictionary uses locks quite heavily. However, it is careful to wield locks only where necessary to ensure that concurrency is maximised. This will, by necessity, be a higher-level look than my other posts in this series, as there is quite a lot of code and logic in ConcurrentDictionary. Therefore, I do recommend that you have ConcurrentDictionary open in a decompiler to have a look at all the details that I skip over. The problem with locks There's several things to bear in mind when using locks, as encapsulated by the lock keyword in C# and the System.Threading.Monitor class in .NET (if you're unsure as to what lock does in C#, I briefly covered it in my first post in the series): Locks block threads The most obvious problem is that threads waiting on a lock can't do any work at all. No preparatory work, no 'optimistic' work like in ConcurrentQueue and ConcurrentStack, nothing. It sits there, waiting to be unblocked. This is bad if you're trying to maximise concurrency. Locks are slow Whereas most of the methods on the Interlocked class can be compiled down to a single CPU instruction, ensuring atomicity at the hardware level, taking out a lock requires some heavy lifting by the CLR and the operating system. There's quite a bit of work required to take out a lock, block other threads, and wake them up again. If locks are used heavily, this impacts performance. Deadlocks When using locks there's always the possibility of a deadlock - two threads, each holding a lock, each trying to aquire the other's lock. Fortunately, this can be avoided with careful programming and structured lock-taking, as we'll see. So, it's important to minimise where locks are used to maximise the concurrency and performance of the collection. Implementation As you might expect, ConcurrentDictionary is similar in basic implementation to the non-concurrent Dictionary, which I studied in a previous post. I'll be using some concepts introduced there, so I recommend you have a quick read of it. So, if you were implementing a thread-safe dictionary, what would you do? The naive implementation is to simply have a single lock around all methods accessing the dictionary. This would work, but doesn't allow much concurrency. Fortunately, the bucketing used by Dictionary allows a simple but effective improvement to this - one lock per bucket. This allows different threads modifying different buckets to do so in parallel. Any thread making changes to the contents of a bucket takes the lock for that bucket, ensuring those changes are thread-safe. The method that maps each bucket to a lock is the GetBucketAndLockNo method: private void GetBucketAndLockNo( int hashcode, out int bucketNo, out int lockNo, int bucketCount) { // the bucket number is the hashcode (without the initial sign bit) // modulo the number of buckets bucketNo = (hashcode & 0x7fffffff) % bucketCount; // and the lock number is the bucket number modulo the number of locks lockNo = bucketNo % m_locks.Length; } However, this does require some changes to how the buckets are implemented. The 'implicit' linked list within a single backing array used by the non-concurrent Dictionary adds a dependency between separate buckets, as every bucket uses the same backing array. Instead, ConcurrentDictionary uses a strict linked list on each bucket: This ensures that each bucket is entirely separate from all other buckets; adding or removing an item from a bucket is independent to any changes to other buckets. Modifying the dictionary All the operations on the dictionary follow the same basic pattern: void AlterBucket(TKey key, ...) { int bucketNo, lockNo; 1: GetBucketAndLockNo( key.GetHashCode(), out bucketNo, out lockNo, m_buckets.Length); 2: lock (m_locks[lockNo]) { 3: Node headNode = m_buckets[bucketNo]; 4: Mutate the node linked list as appropriate } } For example, when adding another entry to the dictionary, you would iterate through the linked list to check whether the key exists already, and add the new entry as the head node. When removing items, you would find the entry to remove (if it exists), and remove the node from the linked list. Adding, updating, and removing items all follow this pattern. Performance issues There is a problem we have to address at this point. If the number of buckets in the dictionary is fixed in the constructor, then the performance will degrade from O(1) to O(n) when a large number of items are added to the dictionary. As more and more items get added to the linked lists in each bucket, the lookup operations will spend most of their time traversing a linear linked list. To fix this, the buckets array has to be resized once the number of items in each bucket has gone over a certain limit. (In ConcurrentDictionary this limit is when the size of the largest bucket is greater than the number of buckets for each lock. This check is done at the end of the TryAddInternal method.) Resizing the bucket array and re-hashing everything affects every bucket in the collection. Therefore, this operation needs to take out every lock in the collection. Taking out mutiple locks at once inevitably summons the spectre of the deadlock; two threads each hold a lock, and each trying to acquire the other lock. How can we eliminate this? Simple - ensure that threads never try to 'swap' locks in this fashion. When taking out multiple locks, always take them out in the same order, and always take out all the locks you need before starting to release them. In ConcurrentDictionary, this is controlled by the AcquireLocks, AcquireAllLocks and ReleaseLocks methods. Locks are always taken out and released in the order they are in the m_locks array, and locks are all released right at the end of the method in a finally block. At this point, it's worth pointing out that the locks array is never re-assigned, even when the buckets array is increased in size. The number of locks is fixed in the constructor by the concurrencyLevel parameter. This simplifies programming the locks; you don't have to check if the locks array has changed or been re-assigned before taking out a lock object. And you can be sure that when a thread takes out a lock, another thread isn't going to re-assign the lock array. This would create a new series of lock objects, thus allowing another thread to ignore the existing locks (and any threads controlling them), breaking thread-safety. Consequences of growing the array Just because we're using locks doesn't mean that race conditions aren't a problem. We can see this by looking at the GrowTable method. The operation of this method can be boiled down to: private void GrowTable(Node[] buckets) { try { 1: Acquire first lock in the locks array // this causes any other thread trying to take out // all the locks to block because the first lock in the array // is always the one taken out first // check if another thread has already resized the buckets array // while we were waiting to acquire the first lock 2: if (buckets != m_buckets) return; 3: Calculate the new size of the backing array 4: Node[] array = new array[size]; 5: Acquire all the remaining locks 6: Re-hash the contents of the existing buckets into array 7: m_buckets = array; } finally { 8: Release all locks } } As you can see, there's already a check for a race condition at step 2, for the case when the GrowTable method is called twice in quick succession on two separate threads. One will successfully resize the buckets array (blocking the second in the meantime), when the second thread is unblocked it'll see that the array has already been resized & exit without doing anything. There is another case we need to consider; looking back at the AlterBucket method above, consider the following situation: Thread 1 calls AlterBucket; step 1 is executed to get the bucket and lock numbers. Thread 2 calls GrowTable and executes steps 1-5; thread 1 is blocked when it tries to take out the lock in step 2. Thread 2 re-hashes everything, re-assigns the buckets array, and releases all the locks (steps 6-8). Thread 1 is unblocked and continues executing, but the calculated bucket and lock numbers are no longer valid. Between calculating the correct bucket and lock number and taking out the lock, another thread has changed where everything is. Not exactly thread-safe. Well, a similar problem was solved in ConcurrentStack and ConcurrentQueue by storing a local copy of the state, doing the necessary calculations, then checking if that state is still valid. We can use a similar idea here: void AlterBucket(TKey key, ...) { while (true) { Node[] buckets = m_buckets; int bucketNo, lockNo; GetBucketAndLockNo( key.GetHashCode(), out bucketNo, out lockNo, buckets.Length); lock (m_locks[lockNo]) { // if the state has changed, go back to the start if (buckets != m_buckets) continue; Node headNode = m_buckets[bucketNo]; Mutate the node linked list as appropriate } break; } } TryGetValue and GetEnumerator And so, finally, we get onto TryGetValue and GetEnumerator. I've left these to the end because, well, they don't actually use any locks. How can this be? Whenever you change a bucket, you need to take out the corresponding lock, yes? Indeed you do. However, it is important to note that TryGetValue and GetEnumerator don't actually change anything. Just as immutable objects are, by definition, thread-safe, read-only operations don't need to take out a lock because they don't change anything. All lockless methods can happily iterate through the buckets and linked lists without worrying about locking anything. However, this does put restrictions on how the other methods operate. Because there could be another thread in the middle of reading the dictionary at any time (even if a lock is taken out), the dictionary has to be in a valid state at all times. Every change to state has to be made visible to other threads in a single atomic operation (all relevant variables are marked volatile to help with this). This restriction ensures that whatever the reading threads are doing, they never read the dictionary in an invalid state (eg items that should be in the collection temporarily removed from the linked list, or reading a node that has had it's key & value removed before the node itself has been removed from the linked list). Fortunately, all the operations needed to change the dictionary can be done in that way. Bucket resizes are made visible when the new array is assigned back to the m_buckets variable. Any additions or modifications to a node are done by creating a new node, then splicing it into the existing list using a single variable assignment. Node removals are simply done by re-assigning the node's m_next pointer. Because the dictionary can be changed by another thread during execution of the lockless methods, the GetEnumerator method is liable to return dirty reads - changes made to the dictionary after GetEnumerator was called, but before the enumeration got to that point in the dictionary. It's worth listing at this point which methods are lockless, and which take out all the locks in the dictionary to ensure they get a consistent view of the dictionary: Lockless: TryGetValue GetEnumerator The indexer getter ContainsKey Takes out every lock (lockfull?): Count IsEmpty Keys Values CopyTo ToArray Concurrent principles That covers the overall implementation of ConcurrentDictionary. I haven't even begun to scratch the surface of this sophisticated collection. That I leave to you. However, we've looked at enough to be able to extract some useful principles for concurrent programming: Partitioning When using locks, the work is partitioned into independant chunks, each with its own lock. Each partition can then be modified concurrently to other partitions. Ordered lock-taking When a method does need to control the entire collection, locks are taken and released in a fixed order to prevent deadlocks. Lockless reads Read operations that don't care about dirty reads don't take out any lock; the rest of the collection is implemented so that any reading thread always has a consistent view of the collection. That leads us to the final collection in this little series - ConcurrentBag. Lacking a non-concurrent analogy, it is quite different to any other collection in the class libraries. Prepare your thinking hats!

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• How to change I/O priority of a process or thread in Win7?

  - by romkyns

  Process Explorer is able to show the effective IO priority of a given thread, but not change it. Seeing as IO priority support is a comparatively new feature, most programs don't set their own IO priorities. It appears that by default the IO priority is derived from the thread priority (rather than process priority), which Process Explorer can't modify either. Are there any other tools out there that can help me change the IO priority of a given thread / all threads of a given process?

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• Why should most logic be in the monitor objects and not in the thread objects when writing concurrent software in Java?

  - by refuser

  When I took the Realtime and Concurrent programming course our lecturer told us that when writing concurrent programs in Java and using monitors, most of the logic should be in the monitor and as little as possible in the threads that access it. I never really understood why and I really would like to. Let me clarify. In this particular case we had several classes. Lift extends Thread Person extends Thread LiftView Monitor, all methods synchronized. This is nothing we came up with, our task was to implement a lift simulation with persons waiting on different floors, and theses were the class skeletons that were given. Then our lecturer said to implement most of the logic in the monitor (he was talking about class Monitor as THE monitor) and as little as possible in the threads. Why would he make a statement like that?

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• MS-Outlook add-on to move a new message to the same folder as the rest of the thread

  - by Guss

  I'm forced to use MS-Outlook in my job, while I very much like the feature that shows all the messages of a discussion thread (that are stored in different folders) in the inbox when a new message is received for that thread, if the previous messages are in a different data file (which I'm forced to have as the MS-Exchange server quota is very very small) then the message list only shows the name of the data file and not the name of the folder where the messages are stored. As a result, because I file my message by context (i.e. all the emails for project A go into a "Project A" folder, etc), and its important for me to have all the messages in a single thread in the same folder, it is sometimes hard to figure out into which folder should I file the new message. It would be great help if there was some add-on or VBA script that I could add to my setup that will offer a shortcut key or a button to "file this message to the same folder as the previous messages in the conversation thread".

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• how to serialize function depending on what instance of object calls it, if same instance call in a thread then do serialize else not

  - by LondonDreams

  I have a function which fetches and updates some record from db and I am trying to make sure each if the function is called by same instance of object(same Or different thread) then function should behave synchronized else its a call from different object instance function need not to be synchronized. I have tried it use a lock per client. That is, instead of synchronizing the method directly using explicit locking through lock objects using Map. function is like :- getAndUpdateMyHitCount(myObjId){ //go to db and get unique record by myObjId //fetch value , increment , save update } And this function may get call is same thread by different Or same object instance But as fetching and matching from Map is slow , Is there other optimized way to do this ? Found similar at this Question but dont feel that is optimized

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• which thread a BeginInvoke's callback of a asynchronous delegate is in?

  - by northTiger

  Which thread a BeginInvoke's callback of a asynchronous delegate is supposed to be in? UI thread or a Thread Pool thread. for example private void button1_Click(object sender, EventArgs e) { Func func1 = LoadingDada; func1.BeginInvoke(IsDone, func1); } string IsDone(...) { .... }

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• What is the difference when a class extend from Handler and Thread? (In Android framework)

  - by XC

  What is the difference when a class extend from Handler and Thread? As described in developer.android.com ... Each Handler instance is associated with a single thread and that thread's message queue. ... Does the thread has no message queue ? Any benefit for a class extend from Handler?

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