Search Results

Search found 28159 results on 1127 pages for 'main thread'.

facebook twitter digg google delicious technorati stumbleupon myspace wordpress linkedin gmail igoogle windows live tumblr viadeo yahoo buzz yahoo mail yahoo bookmarks favorites email print

Page 67/1127 | < Previous Page | 63 64 65 66 67 68 69 70 71 72 73 74  | Next Page >

  • Why would you precede the main() function in C with a data type?

    - by Milktrader
    Many are familiar with the hello world program in C #include <stdio.h> main () { printf ("hello world"); return 0; } Why do some precede the main () function with int as in: int main() Also, I've seen the word 'void' entered inside the () as in: int main(void) It seems like extra typing for nothing, but maybe it's a best practice that pays dividends in other situations? Also, why precede main() with an int if you're returning a character string? If anything, one would expect: char main(void) I'm also foggy about why we return 0 at the end of the function.

    Read the article

  • Is it a header file or library? in a makefile

    - by gccinac
    I already know the differences between a header file and a library. However, when I'm writing my makefile, I have some difficulties on deciding if I should put something as a dependency of the file or just at the linking rule. For example: I have 2 simple files: main.c: #include <stdio.h> main(){ printf("this is the sine or 90"); sinus(90); } and func.c: #include <math.h> sinus(int num){ return sin(num); } and my makefile is: main: main.o func.o gcc main.o func.o -lm -o main func.o: func.c main.o: main.c Well, my question is why this makefile works and this one doesn't: main: main.o func.o gcc main.o func.o -lm -o main func.o: func.c math.h main.o: main.c

    Read the article

  • NetBeans/C++ - how to choose the "main file" other than when creating a project?

    - by Petike
    Hello, when I am creating a C++ project in NetBeans, there is a toggle button "Create main file" - I just enter a name for it and that's all. The problem is that I cannot put that file in a "different" folder than right in the main project folder. And I am "used" to put all the source files in a "src" folder (and its subfolders), but at the "project creation time" I "cannot" put the main file there. So I tried "not" to create the main file at project creation, but after that create manually the "src" file and then create a "cpp" file in that folder (this is "allowed" in NetBeans). But NetBeans could not find "which" is the main file. So how can I choose the main file other than when creating a project (if it is possible)?

    Read the article

  • 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.

    Read the article

  • 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; } }

    Read the article

  • Is this a valid pattern for raising events in C#?

    - by Will Vousden
    Update: For the benefit of anyone reading this, since .NET 4, the lock is unnecessary due to changes in synchronization of auto-generated events, so I just use this now: public static void Raise<T>(this EventHandler<T> handler, object sender, T e) where T : EventArgs { if (handler != null) { handlerCopy(sender, e); } } And to raise it: SomeEvent.Raise(this, new FooEventArgs()); Having been reading one of Jon Skeet's articles on multithreading, I've tried to encapsulate the approach he advocates to raising an event in an extension method like so (with a similar generic version): public static void Raise(this EventHandler handler, object @lock, object sender, EventArgs e) { EventHandler handlerCopy; lock (@lock) { handlerCopy = handler; } if (handlerCopy != null) { handlerCopy(sender, e); } } This can then be called like so: protected virtual void OnSomeEvent(EventArgs e) { this.someEvent.Raise(this.eventLock, this, e); } Are there any problems with doing this? Also, I'm a little confused about the necessity of the lock in the first place. As I understand it, the delegate is copied in the example in the article to avoid the possibility of it changing (and becoming null) between the null check and the delegate call. However, I was under the impression that access/assignment of this kind is atomic, so why is the lock necessary? Update: With regards to Mark Simpson's comment below, I threw together a test: static class Program { private static Action foo; private static Action bar; private static Action test; static void Main(string[] args) { foo = () => Console.WriteLine("Foo"); bar = () => Console.WriteLine("Bar"); test += foo; test += bar; test.Test(); Console.ReadKey(true); } public static void Test(this Action action) { action(); test -= foo; Console.WriteLine(); action(); } } This outputs: Foo Bar Foo Bar This illustrates that the delegate parameter to the method (action) does not mirror the argument that was passed into it (test), which is kind of expected, I guess. My question is will this affect the validity of the lock in the context of my Raise extension method? Update: Here is the code I'm now using. It's not quite as elegant as I'd have liked, but it seems to work: public static void Raise<T>(this object sender, ref EventHandler<T> handler, object eventLock, T e) where T : EventArgs { EventHandler<T> copy; lock (eventLock) { copy = handler; } if (copy != null) { copy(sender, e); } }

    Read the article

  • 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.

    Read the article

  • 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?

    Read the article

  • 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!

    Read the article

  • 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?

    Read the article

  • Box2D how to implement a camera?

    - by Romeo
    By now i have this Camera class. package GameObjects; import main.Main; import org.jbox2d.common.Vec2; public class Camera { public int x; public int y; public int sx; public int sy; public static final float PIXEL_TO_METER = 50f; private float yFlip = -1.0f; public Camera() { x = 0; y = 0; sx = x + Main.APPWIDTH; sy = y + Main.APPHEIGHT; } public Camera(int x, int y) { this.x = x; this.y = y; sx = x + Main.APPWIDTH; sy = y + Main.APPHEIGHT; } public void update() { sx = x + Main.APPWIDTH; sy = y + Main.APPHEIGHT; } public void moveCam(int mx, int my) { if(mx >= 0 && mx <= 80) { this.x -= 2; } else if(mx <= Main.APPWIDTH && mx >= Main.APPWIDTH - 80) { this.x += 2; } if(my >= 0 && my <= 80) { this.y += 2; } else if(my <= Main.APPHEIGHT && my >= Main.APPHEIGHT - 80) { this.y -= 2; } this.update(); } public float meterToPixel(float meter) { return meter * PIXEL_TO_METER; } public float pixelToMeter(float pixel) { return pixel / PIXEL_TO_METER; } public Vec2 screenToWorld(Vec2 screenV) { return new Vec2(screenV.x + this.x, yFlip * screenV.y + this.y); } public Vec2 worldToScreen(Vec2 worldV) { return new Vec2(worldV.x - this.x, yFlip * worldV.y - this.y); } } I need to know how to modify the screenToWorld and worldToScreen functions to include the PIXEL_TO_METER scaling.

    Read the article

  • 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?

    Read the article

  • Is there a quasi-standard set of attributes to annotate thread safety, immutability etc.?

    - by Eugene Beresovksy
    Except for a blog post here and there, describing the custom attributes someone created, but that do not seem to get any traction - like one describing how to enforce immutability, another one on Documenting Thread Safety, modeling the attributes after JCIP annotations - is there any standard emerging? Anything MS might be planning for the future? This is something that should be standard, if there's to be any chance of interoperability between libraries concurrency-wise. Both for documentation purposes, and also to feed static / dynamic test tools. If MS isn't doing anything in that direction, it could be done on CodePlex - but I couldn't find anything there, either. <opinion>Concurrency and thread safety are really hard in imperative and object-languages like C# and Java, we should try to tame it, until we hopefully switch to more appropriate languages.</opinion>

    Read the article

  • 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".

    Read the article

  • 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

    Read the article

  • Weirdness with cabal, HTF, and HUnit assertions

    - by rampion
    So I'm trying to use HTF to run some HUnit-style assertions % cat tests/TestDemo.hs {-# OPTIONS_GHC -Wall -F -pgmF htfpp #-} module Main where import Test.Framework import Test.HUnit.Base ((@?=)) import System.Environment (getArgs) -- just run some tests main :: IO () main = getArgs >>= flip runTestWithArgs Main.allHTFTests -- all these tests should fail test_fail_int1 :: Assertion test_fail_int1 = (0::Int) @?= (1::Int) test_fail_bool1 :: Assertion test_fail_bool1 = True @?= False test_fail_string1 :: Assertion test_fail_string1 = "0" @?= "1" test_fail_int2 :: Assertion test_fail_int2 = [0::Int] @?= [1::Int] test_fail_string2 :: Assertion test_fail_string2 = "true" @?= "false" test_fail_bool2 :: Assertion test_fail_bool2 = [True] @?= [False] And when I use ghc --make, it seems to work correctly. % ghc --make tests/TestDemo.hs [1 of 1] Compiling Main ( tests/TestDemo.hs, tests/TestDemo.o ) Linking tests/TestDemo ... % tests/TestDemoA ... * Tests: 6 * Passed: 0 * Failures: 6 * Errors: 0 Failures: * Main:fail_int1 (tests/TestDemo.hs:9) * Main:fail_bool1 (tests/TestDemo.hs:12) * Main:fail_string1 (tests/TestDemo.hs:15) * Main:fail_int2 (tests/TestDemo.hs:19) * Main:fail_string2 (tests/TestDemo.hs:22) * Main:fail_bool2 (tests/TestDemo.hs:25) But when I use cabal to build it, not all the tests that should fail, fail. % cat Demo.cabal ... executable test-demo build-depends: base >= 4, HUnit, HTF main-is: TestDemo.hs hs-source-dirs: tests % cabal configure Resolving dependencies... Configuring Demo-0.0.0... % cabal build Preprocessing executables for Demo-0.0.0... Building Demo-0.0.0... [1 of 1] Compiling Main ( tests/TestDemo.hs, dist/build/test-demo/test-demo-tmp/Main.o ) Linking dist/build/test-demo/test-demo ... % dist/build/test-demo/test-demo ... * Tests: 6 * Passed: 3 * Failures: 3 * Errors: 0 Failures: * Main:fail_int2 (tests/TestDemo.hs:23) * Main:fail_string2 (tests/TestDemo.hs:26) * Main:fail_bool2 (tests/TestDemo.hs:29) What's going wrong and how can I fix it?

    Read the article

  • Make Errors: Missing Includes in C++ Script?

    - by Abs
    Hello all, I just got help in how to compile this script a few mintues ago on SO but I have managed to get errors. I am only a beginner in C++ and have no idea what the below erros means or how to fix it. This is the script in question. I have read the comments from some users suggesting they changed the #include parts but it seems to be exactly what the script has, see this comment. [root@localhost wkthumb]# qmake-qt4 && make g++ -c -pipe -O2 -g -pipe -Wall -Wp,-D_FORTIFY_SOURCE=2 -fstack-protector --param=ssp-buffer-size=4 -m32 -march=i386 -mtune=generic -fasynchronous-unwind-tables -Wall -W -D_REENTRANT -DQT_NO_DEBUG -DQT_GUI_LIB -DQT_CORE_LIB -I/usr/lib/qt4/mkspecs/linux-g++ -I. -I/usr/include/QtCore -I/usr/include/QtGui -I/usr/include -I. -I. -I. -o main.o main.cpp main.cpp:5:20: error: QWebView: No such file or directory main.cpp:6:21: error: QWebFrame: No such file or directory main.cpp:8: error: expected constructor, destructor, or type conversion before ‘*’ token main.cpp:11: error: ‘QWebView’ has not been declared main.cpp: In function ‘void loadFinished(bool)’: main.cpp:18: error: ‘view’ was not declared in this scope main.cpp:18: error: ‘QWebSettings’ has not been declared main.cpp:19: error: ‘QWebSettings’ has not been declared main.cpp:20: error: ‘QWebSettings’ has not been declared main.cpp: In function ‘int main(int, char**)’: main.cpp:42: error: ‘view’ was not declared in this scope main.cpp:42: error: expected type-specifier before ‘QWebView’ main.cpp:42: error: expected `;' before ‘QWebView’ make: *** [main.o] Error 1 I have the web kit on my Fedora Core 10 machine: qt-4.5.3-9.fc10.i386 qt-devel-4.5.3-9.fc10.i386 Thanks all for any help

    Read the article

  • Threads in WCF service

    - by dragonfly
    Hi, there is a piece of code: class WCFConsoleHostApp : IBank { private static int _instanceCounter; public WCFConsoleHostApp () { Interlocked.Increment(ref _instanceCounter); Console.WriteLine(string.Format("{0:T} Instance nr " + _instanceCounter + " created", DateTime.Now)); } private static int amount; static void Main(string[] args) { ServiceHost host = new ServiceHost(typeof(WCFConsoleHostApp)); host.Open(); Console.WriteLine("Host is running..."); Console.ReadLine(); } #region IBank Members BankOperationResult IBank.Put(int amount) { Console.WriteLine(string.Format("{0:00} {1}", Thread.CurrentThread.ManagedThreadId, Thread.CurrentThread.IsThreadPoolThread) + " Putting..."); WCFConsoleHostApp.amount += amount; Thread.Sleep(20000); Console.WriteLine(string.Format("{0:00} {1}", Thread.CurrentThread.ManagedThreadId, Thread.CurrentThread.IsThreadPoolThread) + " Putting done"); return new BankOperationResult { CurrentAmount = WCFConsoleHostApp.amount, Success = true }; } BankOperationResult IBank.Withdraw(int amount) { Console.WriteLine(string.Format("{0:00} {1}", Thread.CurrentThread.ManagedThreadId, Thread.CurrentThread.IsThreadPoolThread) + " Withdrawing..."); WCFConsoleHostApp.amount -= amount; Thread.Sleep(20000); Console.WriteLine(string.Format("{0:00} {1}", Thread.CurrentThread.ManagedThreadId, Thread.CurrentThread.IsThreadPoolThread) + " Withdrawing done"); return new BankOperationResult { CurrentAmount = WCFConsoleHostApp.amount, Success = true }; } #endregion } My test client application calls that service in 50 threads (service is PerCall). What I found very disturbing is when I added Thread.Sleep(20000) WCF creates one service instance per second using different thread from pool. When I remove Thread.Sleep(20000) 50 instances are instanciated straight away, and about 2-4 threads are used to do it - which in fact I consider normal. Could somebody explain why when Thread.Sleep causes those funny delays in creating instances?

    Read the article

  • Perl cgi @INC different in shell and in http request

    - by pistacchio
    Hi to all, I have the follwing, simplest per cgi script: use strict; use warnings; use CGI(); use CGI::Carp qw(fatalsToBrowser); use Template; print CGI::header(); foreach(@INC) { print "$_\n"; } When called (http://[..]/cgi-bin/p.cgi) I am given the following error: Can't locate Template.pm in @INC (@INC contains: /usr/lib/perl5/site_perl/5.8.8/i386-linux-thread-multi /usr/lib/perl5/site_perl/5.8.8 /usr/lib/perl5/site_perl /usr/lib/perl5/vendor_perl/5.8.8/i386-linux-thread-multi /usr/lib/perl5/vendor_perl/5.8.8 /usr/lib/perl5/vendor_perl /usr/lib/perl5/5.8.8/i386-linux-thread-multi /usr/lib/perl5/5.8.8 .) at /home/pistacchio/webapps/htdocs/cgi-bin/p.cgi line 8. BEGIN failed--compilation aborted at /home/pistacchio/webapps/htdocs/cgi-bin/p.cgi line 8. I made sure that Template is installed and indeed when running this program from shell it works (loads Template) and outputs: Content-Type: text/html; charset=ISO-8859-1 /home/pistacchio/lib/perl5 /home/pistacchio/lib/perl5/lib/i386-linux-thread-multi /home/pistacchio/lib/perl5/lib /home/pistacchio/lib/perl5/lib/i386-linux-thread-multi /usr/lib/perl5/site_perl/5.8.8/i386-linux-thread-multi /usr/lib/perl5/site_perl/5.8.8 /usr/lib/perl5/site_perl /usr/lib/perl5/vendor_perl/5.8.8/i386-linux-thread-multi /usr/lib/perl5/vendor_perl/5.8.8 /usr/lib/perl5/vendor_perl /usr/lib/perl5/5.8.8/i386-linux-thread-multi /usr/lib/perl5/5.8.8 Template is installed in /home/pistacchio/lib/perl5/lib/i386-linux-thread-multi [pistacchio@web118 i386-linux-thread-multi]$ pwd /home/pistacchio/lib/perl5/lib/i386-linux-thread-multi [pistacchio@web118 i386-linux-thread-multi]$ ls auto perllocal.pod Template Template.pm This directory is correctly listed in env and, as previously posted, in @INC. In @INC it is shown twice, so I even tried to pop it out before calling use Template, but without result. From env: [pistacchio@web118 i386-linux-thread-multi]$ env [..] PERL5LIB=/home/pistacchio/lib/perl5:/home/pistacchio/lib/perl5/lib:/home/pistacchio/lib/perl5/lib/i386-linux-thread-multi [..] Removing use Template gets rid of the problem. Can anybody help?

    Read the article

  • How do I set Perl's @INC for a CGI script?

    - by pistacchio
    I have the follwing, simplest Perl CGI script: use strict; use warnings; use CGI(); use CGI::Carp qw(fatalsToBrowser); use Template; print CGI::header(); foreach(@INC) { print "$_\n"; } When called (http://[..]/cgi-bin/p.cgi) I am given the following error: Can't locate Template.pm in @INC (@INC contains: /usr/lib/perl5/site_perl/5.8.8/i386-linux-thread-multi /usr/lib/perl5/site_perl/5.8.8 /usr/lib/perl5/site_perl /usr/lib/perl5/vendor_perl/5.8.8/i386-linux-thread-multi /usr/lib/perl5/vendor_perl/5.8.8 /usr/lib/perl5/vendor_perl /usr/lib/perl5/5.8.8/i386-linux-thread-multi /usr/lib/perl5/5.8.8 .) at /home/pistacchio/webapps/htdocs/cgi-bin/p.cgi line 8. BEGIN failed--compilation aborted at /home/pistacchio/webapps/htdocs/cgi-bin/p.cgi line 8. I made sure that Template is installed and indeed when running this program from shell it works (loads Template) and outputs: Content-Type: text/html; charset=ISO-8859-1 /home/pistacchio/lib/perl5 /home/pistacchio/lib/perl5/lib/i386-linux-thread-multi /home/pistacchio/lib/perl5/lib /home/pistacchio/lib/perl5/lib/i386-linux-thread-multi /usr/lib/perl5/site_perl/5.8.8/i386-linux-thread-multi /usr/lib/perl5/site_perl/5.8.8 /usr/lib/perl5/site_perl /usr/lib/perl5/vendor_perl/5.8.8/i386-linux-thread-multi /usr/lib/perl5/vendor_perl/5.8.8 /usr/lib/perl5/vendor_perl /usr/lib/perl5/5.8.8/i386-linux-thread-multi /usr/lib/perl5/5.8.8 Template is installed in /home/pistacchio/lib/perl5/lib/i386-linux-thread-multi [pistacchio@web118 i386-linux-thread-multi]$ pwd /home/pistacchio/lib/perl5/lib/i386-linux-thread-multi [pistacchio@web118 i386-linux-thread-multi]$ ls auto perllocal.pod Template Template.pm This directory is correctly listed in env and, as previously posted, in @INC. In @INC it is shown twice, so I even tried to pop it out before calling use Template, but without result. From env: [pistacchio@web118 i386-linux-thread-multi]$ env [..] PERL5LIB=/home/pistacchio/lib/perl5:/home/pistacchio/lib/perl5/lib:/home/pistacchio/lib/perl5/lib/i386-linux-thread-multi [..] Removing use Template gets rid of the problem.

    Read the article

  • How to parallelize this groovy code?

    - by lucas
    I'm trying to write a reusable component in Groovy to easily shoot off emails from some of our Java applications. I would like to pass it a List, where Email is just a POJO(POGO?) with some email info. I'd like it to be multithreaded, at least running all the email logic in a second thread, or make one thread per email. I am really foggy on multithreading in Java so that probably doesn't help! I've attempted a few different ways, but here is what I have right now: void sendEmails(List<Email> emails) { def threads = [] def sendEm = emails.each{ email -> def th = new Thread({ Random rand = new Random() def wait = (long)(rand.nextDouble() * 1000) println "in closure" this.sleep wait sendEmail(email) }) println "putting thread in list" threads << th } threads.each { it.run() } threads.each { it.join() } } I was hoping the sleep would randomly slow some threads down so the console output wouldn't be sequential. Instead, I see this: putting thread in list putting thread in list putting thread in list putting thread in list putting thread in list putting thread in list putting thread in list putting thread in list putting thread in list putting thread in list in closure sending email1 in closure sending email2 in closure sending email3 in closure sending email4 in closure sending email5 in closure sending email6 in closure sending email7 in closure sending email8 in closure sending email9 in closure sending email10 sendEmail basically does what you'd expect, including the println statement, and the client that calls this follows, void doSomething() { Mailman emailer = MailmanFactory.getExchangeEmailer() def to = ["one","two"] def from = "noreply" def li = [] def email (1..10).each { email = new Email(to,null,from,"email"+it,"hello") li << email } emailer.sendEmails li }

    Read the article

  • MySQL: Limit rows linked to each joined row

    - by SolidSnakeGTI
    Hello, Specifications: MySQL 4.1+ I've certain situation that requires certain result set from MySQL query, let's see the current query first & then ask my question: SELECT thread.dateline AS tdateline, post.dateline AS pdateline, MIN(post.dateline) FROM thread AS thread LEFT JOIN post AS post ON(thread.threadid = post.threadid) LEFT JOIN forum AS forum ON(thread.forumid = forum.forumid) WHERE post.postid != thread.firstpostid AND thread.open = 1 AND thread.visible = 1 AND thread.replycount >= 1 AND post.visible = 1 AND (forum.options & 1) AND (forum.options & 2) AND (forum.options & 4) AND forum.forumid IN(1,2,3) GROUP BY post.threadid ORDER BY tdateline DESC, pdateline ASC As you can see, mainly I need to select dateline of threads from 'thread' table, in addition to dateline of the second post of each thread, that's all under the conditions you see in the WHERE CLAUSE. Since each thread has many posts, and I need only one result per thread, I've used GROUP BY CLAUSE for that purpose. This query will return only one post's dateline with it's related unique thread. My questions are: How to limit returned threads per each forum!? Suppose I need only 5 threads -as a maximum- to be returned for each forum declared in the WHERE CLAUSE 'forum.forumid IN(1,2,3)', how can this be achieved. Is there any recommendations for optimizing this query (of course after solving the first point)? Notes: I prefer not to use sub-queries, but if it's the only solution available I'll accept it. Double queries not recommended. I'm sure there's a smart solution for this situation. Appreciated advice in advance :)

    Read the article

facebook twitter digg google delicious technorati stumbleupon myspace wordpress linkedin gmail igoogle windows live tumblr viadeo yahoo buzz yahoo mail yahoo bookmarks favorites email print

< Previous Page | 63 64 65 66 67 68 69 70 71 72 73 74  | Next Page >