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• Eclipse Galileo + Glassfish v3: JPADeployer NullPointerException on deploy

  - by bshacklett

  I've created a very simple "Enterprise Application" project with about 7 entity beans and one stateless session bean. I've also configured an instance of Glassfish v3 to run as my application server. Unfortunately, when I attempt to publish the EAR to Glassfish, I'm getting the following response: SEVERE: Exception while invoking class org.glassfish.persistence.jpa.JPADeployer prepare method java.lang.NullPointerException at org.glassfish.persistence.jpa.JPADeployer.prepare(JPADeployer.java:104) at com.sun.enterprise.v3.server.ApplicationLifecycle.prepareModule(ApplicationLifecycle.java:644) at org.glassfish.javaee.full.deployment.EarDeployer.prepareBundle(EarDeployer.java:269) at org.glassfish.javaee.full.deployment.EarDeployer.access$200(EarDeployer.java:79) at org.glassfish.javaee.full.deployment.EarDeployer$1.doBundle(EarDeployer.java:131) at org.glassfish.javaee.full.deployment.EarDeployer$1.doBundle(EarDeployer.java:129) at org.glassfish.javaee.full.deployment.EarDeployer.doOnBundles(EarDeployer.java:197) at org.glassfish.javaee.full.deployment.EarDeployer.doOnAllTypedBundles(EarDeployer.java:206) at org.glassfish.javaee.full.deployment.EarDeployer.doOnAllBundles(EarDeployer.java:232) at org.glassfish.javaee.full.deployment.EarDeployer.prepare(EarDeployer.java:129) at com.sun.enterprise.v3.server.ApplicationLifecycle.prepareModule(ApplicationLifecycle.java:644) at com.sun.enterprise.v3.server.ApplicationLifecycle.deploy(ApplicationLifecycle.java:296) at com.sun.enterprise.v3.server.ApplicationLifecycle.deploy(ApplicationLifecycle.java:183) at org.glassfish.deployment.admin.DeployCommand.execute(DeployCommand.java:272) at com.sun.enterprise.v3.admin.CommandRunnerImpl$1.execute(CommandRunnerImpl.java:305) at com.sun.enterprise.v3.admin.CommandRunnerImpl.doCommand(CommandRunnerImpl.java:320) at com.sun.enterprise.v3.admin.CommandRunnerImpl.doCommand(CommandRunnerImpl.java:1176) at com.sun.enterprise.v3.admin.CommandRunnerImpl.access$900(CommandRunnerImpl.java:83) at com.sun.enterprise.v3.admin.CommandRunnerImpl$ExecutionContext.execute(CommandRunnerImpl.java:1235) at com.sun.enterprise.v3.admin.CommandRunnerImpl$ExecutionContext.execute(CommandRunnerImpl.java:1224) at com.sun.enterprise.v3.admin.AdminAdapter.doCommand(AdminAdapter.java:365) at com.sun.enterprise.v3.admin.AdminAdapter.service(AdminAdapter.java:204) at com.sun.grizzly.tcp.http11.GrizzlyAdapter.service(GrizzlyAdapter.java:166) at com.sun.enterprise.v3.server.HK2Dispatcher.dispath(HK2Dispatcher.java:100) at com.sun.enterprise.v3.services.impl.ContainerMapper.service(ContainerMapper.java:245) at com.sun.grizzly.http.ProcessorTask.invokeAdapter(ProcessorTask.java:791) at com.sun.grizzly.http.ProcessorTask.doProcess(ProcessorTask.java:693) at com.sun.grizzly.http.ProcessorTask.process(ProcessorTask.java:954) at com.sun.grizzly.http.DefaultProtocolFilter.execute(DefaultProtocolFilter.java:170) at com.sun.grizzly.DefaultProtocolChain.executeProtocolFilter(DefaultProtocolChain.java:135) at com.sun.grizzly.DefaultProtocolChain.execute(DefaultProtocolChain.java:102) at com.sun.grizzly.DefaultProtocolChain.execute(DefaultProtocolChain.java:88) at com.sun.grizzly.http.HttpProtocolChain.execute(HttpProtocolChain.java:76) at com.sun.grizzly.ProtocolChainContextTask.doCall(ProtocolChainContextTask.java:53) at com.sun.grizzly.SelectionKeyContextTask.call(SelectionKeyContextTask.java:57) at com.sun.grizzly.ContextTask.run(ContextTask.java:69) at com.sun.grizzly.util.AbstractThreadPool$Worker.doWork(AbstractThreadPool.java:330) at com.sun.grizzly.util.AbstractThreadPool$Worker.run(AbstractThreadPool.java:309) at java.lang.Thread.run(Thread.java:637)

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• BackgroundWorker Not working in VSTO

  - by Chris

  I have a background worker. Before I invoke the worker I disable a button and make a gif visible. I then invoke the runworkerasync method and it runs fine until comleteion. On the 'RunWorkerCompleted()' I get a cross thread error. Any idea why? private void buttonRun_Click(object sender, EventArgs e) { if (comboBoxFiscalYear.SelectedIndex != -1 && !string.IsNullOrEmpty(textBoxFolderLoc.Text)) { try { u = new UpdateDispositionReports( Convert.ToInt32(comboBoxFiscalYear.SelectedItem.ToString()) , textBoxFolderLoc.Text , Properties.Settings.Default.TemplatePath , Properties.Settings.Default.ConnStr); this.buttonRun.Enabled = false; this.pictureBox1.Visible = true; BackgroundWorker bw = new BackgroundWorker(); bw.DoWork += new DoWorkEventHandler(bw_DoWork); bw.RunWorkerCompleted += new RunWorkerCompletedEventHandler(bw_RunWorkerCompleted); bw.RunWorkerAsync(); //backgroundWorker1.RunWorkerAsync(); } catch (Exception ex) { MessageBox.Show("Unable to process.\nError:" + ex.Message, Properties.Settings.Default.AppName); } } } void bw_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e) { buttonRun.Enabled = true; pictureBox1.Visible = false; } void bw_DoWork(object sender, DoWorkEventArgs e) { u.Execute(); }

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• MS-Excel Negative times

  - by oxinabox.ucc.asn.au

  I'm writing a spreadsheet for a shop manager. What it does is keep track of the number of hours a worker has worked. So you enter times for Monday-Sunday, and then an adjustment - e.g. if they work 40/40/40/32 hours for the month, then you would have an adjustment of -2/-2/-2/+6 to bring the worker to the 38 hour week that he's being paid for. Some (most) weeks may be adjusted for overtime. The spreadsheet then totals the hours. This spreadsheet is supposed to just be a self-calculating version of a paper form. It needs to match the paper form as it has to be substituted for the old form which is given to some other member of the company (pay clerk, I don't know; I'm not rebuilding their whole system, just replacing a form) I'm having trouble entering a negative time in the adj field - the field has a [h]:mm formatting. and when i enter a negative time (e.g. -2:00) it displays an error, saying "incorrectly formatted equation", with the suggestion that if I was entering a string then I should prefix with a apostrophe. How do I overcome this?

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• COM Interop - Wait for Excel to Complete Operation

  - by roygbiv

  Hello, I am doing some COM Interop work with Excel and other Office Automation Software. A Co-Worker has mentioned to me that I need to wait for these Automation Servers to become ready after issuing a command to them. I, however, cannot see the purpose of this as don't all calls block until the automation server completes the given task? For example I would normally write: Dim o as AutomationObject = AutomationServer.CreateObject(x, y, z) o.Property ' could throw COM exception!!???? My co-worker says I need to sleep after that call because the the Automation Server could still be working on creating and initializing the object. Dim o as AutomationObject = AutomationServer.CreateObject(x, y, z) Threading.Sleep(5000) ' wait for AutomationServer to "become ready" o.Property ' could still throw COM exception!!???? The problem I have with this is that the AutomationServer calls should block until the AutomationServer finishes or completes what it was working on or at the very least it should be a loop checking if "o" is nothing, but that makes no sense because once the call returns its done! My question is, Is there any benefit to Sleeping after an AutomationServer call? Is there a method to "wait" until the AutomationServer finishes (if it does not in fact block)?

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• datanucleus enhancer & javaw: "the parameter is incorrect"

  - by Riley

  I'm on windows XP using eclipse and the datanucleus enhancer for a gwt + gae app. When I run the enhancer, I get an error: Error Thu Oct 21 16:33:57 CDT 2010 Cannot run program "C:\Program Files\Java\jdk1.6.0_18\bin\javaw.exe" (in directory "C:\ag\dev"): CreateProcess error=87, The parameter is incorrect java.io.IOException: Cannot run program "C:\Program Files\Java\jdk1.6.0_18\bin\javaw.exe" (in directory "C:\ag\dev"): CreateProcess error=87, The parameter is incorrect at java.lang.ProcessBuilder.start(Unknown Source) at com.google.gdt.eclipse.core.ProcessUtilities.launchProcessAndActivateOnError(ProcessUtilities.java:213) at com.google.appengine.eclipse.core.orm.enhancement.EnhancerJob.runInWorkspace(EnhancerJob.java:154) at org.eclipse.core.internal.resources.InternalWorkspaceJob.run(InternalWorkspaceJob.java:38) at org.eclipse.core.internal.jobs.Worker.run(Worker.java:55) Caused by: java.io.IOException: CreateProcess error=87, The parameter is incorrect at java.lang.ProcessImpl.create(Native Method) at java.lang.ProcessImpl.<init>(Unknown Source) at java.lang.ProcessImpl.start(Unknown Source) ... 5 more I've had this problem before, and it was due to a long classpath. I just spent an hour and a half shortening my classpath by moving libraries around and even moving my eclipse install, but with no luck. Any ideas about where I should start to look for an answer? The error message doesn't include any information about what directory it's in or anything. It's kind of infuriating! Is it possible to make the output of javaw more verbose? Is it possible to get around this class-path size bug?

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• Finding latency issues (stalls) in embedded Linux systems

  - by camh

  I have an embedded Linux system running on an Atmel AT91SAM9260EK board on which I have two processes running at real-time priority. A manager process periodically "pings" a worker process using POSIX message queues to check the health of the worker process. Usually the round-trip ping takes about 1ms, but very occasionally it takes much longer - about 800ms. There are no other processes that run at a higher priority. It appears the stall may be related to logging (syslog). If I stop logging the problem seems to go away. However it makes no difference if the log file is on JFFS2 or NFS. No other processes are writing to the "disk" - just syslog. What tools are available to me to help me track down why these stalls are occurring? I am aware of latencytop and will be using that. Are there some other tools that may be more useful? Some details: Kernel version: 2.6.32.8 libc (syslog functions): uClibc 0.9.30.1 syslog: busybox 1.15.2

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• hudson.util.ProcessTreeTest test error

  - by senzacionale

  error: Tests run: 1, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.011 sec Running hudson.util.ProcessTreeTest Tests run: 1, Failures: 0, Errors: 1, Skipped: 0, Time elapsed: 0.181 sec <<< FAILURE! Running hudson.model.LoadStatisticsTest Tests run: 1, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 2.089 sec Running hudson.util.ArgumentListBuilderTest Tests run: 5, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.053 sec Running hudson.util.RobustReflectionConverterTest Tests run: 2, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.029 sec Running hudson.util.VersionNumberTest Tests run: 3, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.074 sec Running hudson.util.CyclicGraphDetectorTest Tests run: 3, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.038 sec Results : Tests in error: testRemoting(hudson.util.ProcessTreeTest) Tests run: 102, Failures: 0, Errors: 1, Skipped: 0 [INFO] ------------------------------------------------------------------------ [ERROR] BUILD FAILURE [INFO] ------------------------------------------------------------------------ [INFO] There are test failures. Please refer to D:\PROJEKTI\Maven\hudson\main\core\target\surefire-reports for the individual test results. [INFO] ------------------------------------------------------------------------ [INFO] For more information, run Maven with the -e switch [INFO] ------------------------------------------------------------------------ [INFO] Total time: 17 minutes 58 seconds [INFO] Finished at: Fri Jun 11 21:04:46 CEST 2010 [INFO] Final Memory: 85M/152M [INFO] ------------------------------------------------------------------------ error log: ------------------------------------------------------------------------------- Test set: hudson.util.ProcessTreeTest ------------------------------------------------------------------------------- Tests run: 1, Failures: 0, Errors: 1, Skipped: 0, Time elapsed: 0.181 sec <<< FAILURE! testRemoting(hudson.util.ProcessTreeTest) Time elapsed: 0.169 sec <<< ERROR! org.jvnet.winp.WinpException: Failed to read environment variable table error=299 at .\envvar-cmdline.cpp:114 at org.jvnet.winp.Native.getCmdLineAndEnvVars(Native Method) at org.jvnet.winp.WinProcess.parseCmdLineAndEnvVars(WinProcess.java:114) at org.jvnet.winp.WinProcess.getEnvironmentVariables(WinProcess.java:109) at hudson.util.ProcessTree$Windows$1.getEnvironmentVariables(ProcessTree.java:419) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) at java.lang.reflect.Method.invoke(Method.java:597) at hudson.remoting.RemoteInvocationHandler$RPCRequest.perform(RemoteInvocationHandler.java:274) at hudson.remoting.RemoteInvocationHandler$RPCRequest.call(RemoteInvocationHandler.java:255) at hudson.remoting.RemoteInvocationHandler$RPCRequest.call(RemoteInvocationHandler.java:215) at hudson.remoting.UserRequest.perform(UserRequest.java:114) at hudson.remoting.UserRequest.perform(UserRequest.java:48) at hudson.remoting.Request$2.run(Request.java:270) at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:441) at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:303) at java.util.concurrent.FutureTask.run(FutureTask.java:138) at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908) at java.lang.Thread.run(Thread.java:619) does anyone have any idea what can be wrong in test? Regards

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• Blocking on DBCP connection pool (open and close connnection). Is database connection pooling in OpenEJB pluggable?

  - by topchef

  We use OpenEJB on Tomcat (used to run on JBoss, Weblogic, etc.). While running load tests we experience significant performance problems with handling JMS messages (queues). Problem was localized to blocking on database connection pool getting or releasing connection to the pool. Blocking prevented concurrent MDB instances (threads) from running hence performance suffered 10-fold and worse. The same code used to run on application servers (with their respective connection pool implementations) with no blocking at all. Example of thread blocked: Name: JMS Resource Adapter-worker-23 State: BLOCKED on org.apache.commons.pool.impl.GenericObjectPool@1ea6b4a owned by: JMS Resource Adapter-worker-19 Total blocked: 18,426 Total waited: 0 Stack trace: org.apache.commons.pool.impl.GenericObjectPool.returnObject(GenericObjectPool.java:916) org.apache.commons.dbcp.PoolableConnection.close(PoolableConnection.java:91) - locked org.apache.commons.dbcp.PoolableConnection@1bcba8 org.apache.commons.dbcp.managed.ManagedConnection.close(ManagedConnection.java:147) com.xxxxx.persistence.DbHelper.closeConnection(DbHelper.java:290) .... Couple of questions. I am almost certain that some transactional attributes and properties contribute to this blocking, but MDBs are defined as non-transactional (we use both annotations and ejb-jar.xml). Some EJBs do use container-managed transactions though (and we can observe blocking there as well). Are there any DBCP configurations that may fix blocking? Is DBCP connection pool implementation replaceable in OpenEJB? How easy (difficult) to replace it with another library? Just in case this is how we define data source in OpenEJB (openejb.xml): <Resource id="MyDataSource" type="DataSource"> JdbcDriver oracle.jdbc.driver.OracleDriver JdbcUrl ${oracle.jdbc} UserName ${oracle.user} Password ${oracle.password} JtaManaged true InitialSize 5 MaxActive 30 ValidationQuery SELECT 1 FROM DUAL TestOnBorrow true </Resource>

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• Publish failed using Ant publisher (Eclipse/datanucleus).

  - by aronp

  Dear All, I am being driven mad the following (apparently hard) error from eclipse. Publish failed using Ant publisher Resource is out of sync with the file system: '/MyServlet/build/classes/com/inver/hotzones/database/BaseNetworkData.class'. I have seen comments on similar errors where refreshing eclipses view of the project helps but it is not helping me. Have tried cleaning the project, removing it from the webserver, deleting war files but cant seem to clear it. I have reset my TMPDIR variable so that it uses a directory on the same filesystem as that appeared to be another possible cause. The error occurs on classes which have been enhanced by datanuculeus. I have auto-enhance on the project. The other references to this problem indicate that it is due to Eclipses view of the project being out of step with the filesystem, and I am guessing that this has something to do with thedata nucleus enhancement. Any ideas? Thanks. I am using Eclipse 3.5.2 with latest datanucleus pluggins. Stack trace org.eclipse.core.runtime.CoreException: Resource is out of sync with the file system: '/MyServlet/build/classes/com/inver/hotzones/database/BaseNetworkData.class'. at org.eclipse.jst.server.generic.core.internal.publishers.AbstractModuleAssembler.copyModule(AbstractModuleAssembler.java:172) at org.eclipse.jst.server.generic.core.internal.publishers.WarModuleAssembler.assemble(WarModuleAssembler.java:31) at org.eclipse.jst.server.generic.core.internal.publishers.AntPublisher.assembleModule(AntPublisher.java:167) at org.eclipse.jst.server.generic.core.internal.publishers.AntPublisher.publish(AntPublisher.java:128) at org.eclipse.jst.server.generic.core.internal.GenericServerBehaviour.publishModule(GenericServerBehaviour.java:82) at org.eclipse.wst.server.core.model.ServerBehaviourDelegate.publishModule(ServerBehaviourDelegate.java:949) at org.eclipse.wst.server.core.model.ServerBehaviourDelegate.publishModules(ServerBehaviourDelegate.java:1039) at org.eclipse.wst.server.core.model.ServerBehaviourDelegate.publish(ServerBehaviourDelegate.java:872) at org.eclipse.wst.server.core.model.ServerBehaviourDelegate.publish(ServerBehaviourDelegate.java:708) at org.eclipse.wst.server.core.internal.Server.publishImpl(Server.java:2731) at org.eclipse.wst.server.core.internal.Server$PublishJob.run(Server.java:278) at org.eclipse.core.internal.jobs.Worker.run(Worker.java:55)

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• eclipseFP2 haskell unix haveing issues connectiong to Scion Server

  - by Chris

  I am having troubles with using FP2 for eclipse and getting it to connect with the server. Eclipse seems to auto-detect scion_server, but I a error in the log file !ENTRY net.sf.eclipsefp.haskell.scion.client 4 4 2010-04-15 10:40:06.580 !MESSAGE The connection with the Scion server could not be established. !STACK 0 The connection with the Scion server could not be established. at net.sf.eclipsefp.haskell.scion.internal.client.ScionServer.connectToServer(ScionServer.java:328) at net.sf.eclipsefp.haskell.scion.internal.client.ScionServer.startServer(ScionServer.java:73) at net.sf.eclipsefp.haskell.scion.client.ScionInstance.start(ScionInstance.java:94) at net.sf.eclipsefp.haskell.scion.client.ScionInstance.runCommandSync(ScionInstance.java:207) at net.sf.eclipsefp.haskell.scion.internal.commands.ScionCommand.run(ScionCommand.java:136) at org.eclipse.core.internal.jobs.Worker.run(Worker.java:55) Caused by: java.net.ConnectException: Connection refused at java.net.PlainSocketImpl.socketConnect(Native Method) at java.net.PlainSocketImpl.doConnect(Unknown Source) at java.net.PlainSocketImpl.connectToAddress(Unknown Source) at java.net.PlainSocketImpl.connect(Unknown Source) at java.net.SocksSocketImpl.connect(Unknown Source) at java.net.Socket.connect(Unknown Source) at java.net.Socket.connect(Unknown Source) at java.net.Socket.<init>(Unknown Source) at java.net.Socket.<init>(Unknown Source) at net.sf.eclipsefp.haskell.scion.internal.client.ScionServer.connectToServer(ScionServer.java:345) at net.sf.eclipsefp.haskell.scion.internal.client.ScionServer.connectToServer(ScionServer.java:324)

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• How to set permissions or alter a git commit process when using local repositories

  - by Tony

  I have a server that contains a central git repository and one of my co-worker's development environment. My co-worker's repository's origin is the central git repository and he pushes there when he has some code to share. Likewise, I develop locally and push to the central git repository when I have some code to share, so my repository's origin is also the central git repository. The issue is that I have the central git repository under a "git" user's home directory. So when I push I am actually SSH'ing into the the server as the "git" user. To be even more clear, my config has these lines: $ more .git/config [remote "origin"] fetch = +refs/heads/*:refs/remotes/origin/* url = [email protected]:fsg [branch "master"] remote = origin merge = refs/heads/master When I push, git handles this SSH + push seamlessly with I am guessing some sort of git shell. The issue is that when my coworker pushes, he is logged in as himself for a user and gets a bunch of crazy permission errors. Is there a typical way to solve this problem without opening up git's directories to a group? I think this will be problematic when I push and therefore overwrite the the repository and those permissions are reset. Thanks!

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• Message queue proxy in Python + Twisted

  - by gasper_k

  Hi, I want to implement a lightweight Message Queue proxy. It's job is to receive messages from a web application (PHP) and send them to the Message Queue server asynchronously. The reason for this proxy is that the MQ isn't always avaliable and is sometimes lagging, or even down, but I want to make sure the messages are delivered, and the web application returns immediately. So, PHP would send the message to the MQ proxy running on the same host. That proxy would save the messages to SQLite for persistence, in case of crashes. At the same time it would send the messages from SQLite to the MQ in batches when the connection is available, and delete them from SQLite. Now, the way I understand, there are these components in this service: message listener (listens to the messages from PHP and writes them to a Incoming Queue) DB flusher (reads messages from the Incoming Queue and saves them to a database; due to SQLite single-threadedness) MQ connection handler (keeps the connection to the MQ server online by reconnecting) message sender (collects messages from SQlite db and sends them to the MQ server, then removes them from db) I was thinking of using Twisted for #1 (TCPServer), but I'm having problem with integrating it with other points, which aren't event-driven. Intuition tells me that each of these points should be running in a separate thread, because all are IO-bound and independent of each other, but I could easily put them in a single thread. Even though, I couldn't find any good and clear (to me) examples on how to implement this worker thread aside of Twisted's main loop. The example I've started with is the chatserver.py, which uses service.Application and internet.TCPServer objects. If I start my own thread prior to creating TCPServer service, it runs a few times, but the it stops and never runs again. I'm not sure, why this is happening, but it's probably because I don't use threads with Twisted correctly. Any suggestions on how to implement a separate worker thread and keep Twisted? Do you have any alternative architectures in mind?

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• Workling processes multiplying uncontrolably

  - by adam

  Hello there. We have a rails app running on passenger and we background process some tasks using a combination of RabbitMQ and Workling. The workling's worker process is started using the script/workling_client command. There is always only one worker process started, and the script/workling_client has a :multiple => false options, thus allowing only one instance. But sometimes, under mysterious circumstances which I haven't been able to track down, more worklings spawn up. If I let the system run for some time, more and more worklings appear. I'm not sure if these rogue worklings cause any problems, but it is still unsettling not to know why is it happening. We are using Monit to monitor the workling process. So if it dies, it will spawn it up again. But this still does not explain how come there are suddenly more than one of them. So my question is: does anyone know what can be cause of this and how to make it stop? Is it possible that workling sometimes dies by itself, without deleting it's pid file? Could there be something wrong with the Daemons gem workling_client is build upon?

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• Passive and active sockets

  - by davsan

  Quoting from this socket tutorial: Sockets come in two primary flavors. An active socket is con­nect­ed to a remote active socket via an open data con­nec­tion... A passive socket is not con­nect­ed, but rather awaits an in­com­ing con­nec­tion, which will spawn a new active socket once a con­nec­tion is es­tab­lished ... Each port can have a single passive socket binded to it, await­ing in­com­ing con­nec­tions, and mul­ti­ple active sockets, each cor­re­spond­ing to an open con­nec­tion on the port. It's as if the factory worker is waiting for new mes­sages to arrive (he rep­re­sents the passive socket), and when one message arrives from a new sender, he ini­ti­ates a cor­re­spon­dence (a con­nec­tion) with them by del­e­gat­ing someone else (an active socket) to ac­tu­al­ly read the packet and respond back to the sender if nec­es­sary. This permits the factory worker to be free to receive new packets. ... Then the tutorial explains that, after a connection is established, the active socket continues receiving data until there are no remaining bytes, and then closes the connection. What I didn't understand is this: Suppose there's an incoming connection to the port, and the sender wants to send some little data every 20 minutes. If the active socket closes the connection when there are no remaining bytes, does the sender have to reconnect to the port every time it wants to send data? How do we persist a once established connection for a longer time? Can you tell me what I'm missing here? My second question is, who determines the limit of the concurrently working active sockets?

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• Choosing between .NET Service Bus Queues vs Azure Queue Service

  - by ChrisV

  Just a quick question regarding an Azure application. If I have a number of Web and Worker roles that need to communicate, documentation says to use the Azure Queue Service. However, I've just read that the new .NET Service Bus now also offers queues. These look to be more powerful as they appear to offer a much more detailed API. Whilst the .NSB looks more interesting it has a couple of issues that make me wary of using it in distributed application. (for example, Queue Expiration... if I cannot guarantee that a queue will be renewed on time I may lose it all!). Has anyone had any experience using either of these two technologies and could give any advice on when to choose one over the other. I suspect that whilst the service bus looks more powerful, as my use case is really just enabling Web/Worker roles to communicate between each other, that the Azure Queue Service is what I'm after. But I'm just really looking for confirmation of that before progamming myself in to a corner :-) Thanks in advance. UPDATE Have read up about the two systems over the break. It defo looks like .NET service bus is more specifically designed for integrating systems rather than providing a general purpose reliable messaging system. Azure Queues are distributed and so reliable and scalable in a way that .NSB queues are not and so more suitable for code hosted within Azure itself. Thanks for the responses.

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• How does static code run with multiple threads?

  - by Krisc

  I was reading http://stackoverflow.com/questions/1511798/threading-from-within-a-class-with-static-and-non-static-methods and I am in a similar situation. I have a static method that pulls data from a resource and creates some runtime objects based on the data. static class Worker{ public static MyObject DoWork(string filename){ MyObject mo = new MyObject(); // ... does some work return mo; } } The method takes awhile (in this case it is reading 5-10mb files) and returns an object. I want to take this method and use it in a multiple thread situation so I can read multiple files at once. Design issues / guidelines aside, how would multiple threads access this code? Let's say I have something like this... class ThreadedWorker { public void Run() { Thread t = new Thread(OnRun); t.Start(); } void OnRun() { MyObject mo = Worker.DoWork("somefilename"); mo.WriteToConsole(); } } Does the static method run for each thread, allowing for parallel execution?

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• Using SQL dB column as a lock for concurrent operations in Entity Framework

  - by Sid

  We have a long running user operation that is handled by a pool of worker processes. Data input and output is from Azure SQL. The master Azure SQL table structure columns are approximated to [UserId, col1, col2, ... , col N, beingProcessed, lastTimeProcessed ] beingProcessed is boolean and lastTimeProcessed is DateTime. The logic in every worker role is: public void WorkerRoleMain() { while(true) { try { dbContext db = new dbContext(); // Read foreach (UserProfile user in db.UserProfile .Where(u => DateTime.UtcNow.Subtract(u.lastTimeProcessed) > TimeSpan.FromHours(24) & u.beingProcessed == false)) { user.beingProcessed = true; // Modify db.SaveChanges(); // Write // Do some long drawn processing here ... ... ... user.lastTimeProcessed = DateTime.UtcNow; user.beingProcessed = false; db.SaveChanges(); } } catch(Exception ex) { LogException(ex); Sleep(TimeSpan.FromMinutes(5)); } } // while () } With multiple workers processing as above (each with their own Entity Framework layer), in essence beingProcessed is being used a lock for MutEx purposes Question: How can I deal with concurrency issues on the beingProcessed "lock" itself based on the above load? I think read-modify-write operation on the beingProcessed needs to be atomic but I'm open to other strategies. Open to other code refinements too.

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• why am I stuck on "Initiating update" when deploying to google

  - by michelle

  I've have not had any trouble deploying through eclipse until now. I'm guessing it might have to do with all the stuff I've added today a folder of .pdf and .tex files (in war/web-inf directory) a bit of JDO stuff and a servlet that reads the files in the directory and indexes them into the JDO Is there any way to find out what exactly is the problem? I currently get stuck at "Initiating update" and the stack trace say "ConnectionReset" Any helkp of imput will be appreciated, I really need to deploy this today, thanks! here's the deploy trace: Unable to update: java.net.SocketException: Connection reset at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) at sun.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source) at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source) at java.lang.reflect.Constructor.newInstance(Unknown Source) at sun.net.www.protocol.http.HttpURLConnection$6.run(Unknown Source) at java.security.AccessController.doPrivileged(Native Method) at sun.net.www.protocol.http.HttpURLConnection.getChainedException(Unknown Source) at sun.net.www.protocol.http.HttpURLConnection.getInputStream(Unknown Source) at java.net.HttpURLConnection.getResponseCode(Unknown Source) at com.google.appengine.tools.admin.ServerConnection.getAuthCookie(ServerConnection.java:315) at com.google.appengine.tools.admin.ServerConnection.authenticate(ServerConnection.java:219) at com.google.appengine.tools.admin.ServerConnection.send(ServerConnection.java:145) at com.google.appengine.tools.admin.ServerConnection.post(ServerConnection.java:81) at com.google.appengine.tools.admin.AppVersionUpload.send(AppVersionUpload.java:427) at com.google.appengine.tools.admin.AppVersionUpload.beginTransaction(AppVersionUpload.java:241) at com.google.appengine.tools.admin.AppVersionUpload.doUpload(AppVersionUpload.java:98) at com.google.appengine.tools.admin.AppAdminImpl.update(AppAdminImpl.java:56) at com.google.appengine.eclipse.core.proxy.AppEngineBridgeImpl.deploy(AppEngineBridgeImpl.java:271) at com.google.appengine.eclipse.core.deploy.DeployProjectJob.runInWorkspace(DeployProjectJob.java:148) at org.eclipse.core.internal.resources.InternalWorkspaceJob.run(InternalWorkspaceJob.java:38) at org.eclipse.core.internal.jobs.Worker.run(Worker.java:55) Caused by: java.net.SocketException: Connection reset at java.net.SocketInputStream.read(Unknown Source) at java.io.BufferedInputStream.fill(Unknown Source) at java.io.BufferedInputStream.read1(Unknown Source) at java.io.BufferedInputStream.read(Unknown Source) at sun.net.www.http.HttpClient.parseHTTPHeader(Unknown Source) at sun.net.www.http.HttpClient.parseHTTP(Unknown Source) at sun.net.www.http.HttpClient.parseHTTP(Unknown Source) at sun.net.www.protocol.http.HttpURLConnection.getInputStream(Unknown Source) at sun.net.www.protocol.http.HttpURLConnection.getHeaderFieldKey(Unknown Source) at com.google.appengine.tools.util.ClientCookieManager.readCookies(ClientCookieManager.java:123) at com.google.appengine.tools.admin.ServerConnection.connect(ServerConnection.java:340) at com.google.appengine.tools.admin.ServerConnection.getAuthCookie(ServerConnection.java:314) ... 11 more

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• Implementing java FixedTreadPool status listener

  - by InsertNickHere

  Hi there, it's about an application which is supposed to process (VAD, Loudness, Clipping) a lot of soundfiles (e.g. 100k). At this time, I create as many worker threads (callables) as I can put into memory, and then run all with a threadPool.invokeAll(), write results to file system, unload processed files and continue at step 1. Due to the fact it's an app with a GUI, i don't want to user to feel like the app "is not responding" while processing all soundfiles. (which it does at this time cause invokeAll is blocking). Im not sure what is a "good" way to fix this. It shall not be possible for the user to do other things while processing, but I'd like to show a progress bar like "10 of 100000 soundfiles are done". So how do I get there? Do I have to create a "watcher thread", so that every worker hold a callback on it? I'm quite new to multi threading, and don't get the idea of such a mechanisem.. If you need to know: I'm using SWT/JFace. Regards, InsertNickHere

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• How can I keep an event from being delivered to the GUI until my code finished running?

  - by Frerich Raabe

  I installed a global mouse hook function like this: mouseEventHook = ::SetWindowsHookEx( WH_MOUSE_LL, mouseEventHookFn, thisModule, 0 ); The hook function looks like this: RESULT CALLBACK mouseEventHookFn( int code, WPARAM wParam, LPARAM lParam ) { if ( code == HC_ACTION ) { PMSLLHOOKSTRUCT mi = (PMSLLHOOKSTRUCT)lParam; // .. do interesting stuff .. } return ::CallNextHookEx( mouseEventHook, code, wParam, lParam ); } Now, my problem is that I cannot control how long the 'do interesting stuff' part takes exactly. In particular, it might take longer than the LowLevelHooksTimeout defined in the Windows registry. This means that, at least on Windows XP, the system no longer delivers mouse events to my hook function. I'd like to avoid this, but at the same time I need the 'do interesting stuff' part to happen before the target GUI receives the event. I attempted to solve this by doing the 'interesting stuff' work in a separate thread so that the mouseEventHookFn above can post a message to the worker thread and then do a return 1; immediately (which ends the hook function but avoids that the event is handed to the GUI). The idea was that the worker thread, when finished, performs the CallNextHookEx call itself. However, this causes a crash inside of CallNextHookEx (in fact, the crash occurs inside an internal function called PhkNextValid. I assume it's not safe to call CallNextHookEx from outside a hook function, is this true? If so, does anybody else know how I can run code (which needs to interact with the GUI thread of an application) before the GUI receives the event and avoid that my hook function blocks too long?

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• How to properly use Object Contexts in Entity Framework using BackgroundWorker

  - by OffApps Cory

  Good day, I am developing using Entity Framework and WPF, and I am encountering some errors and I don't know why. When saving a record (using a BackgroundWorker), I set the entities change tracker to nothing (null), attach the record to a new disposable context, save it, detach, and dispose of the context. Saving a record fires and event in the MainViewModel of the program that the other ViewModels (including the one that is saving) need to refresh their entities to reflect changes. Private Sub _saveRecordWorker_DoWork(ByVal sender As Object, ByVal e As System.ComponentModel.DoWorkEventArgs) Handles _saveRecordWorker.DoWork Using MyContext As New RVShippingEntities Dim MyShipment = CType(ShipmentRecord, IEntityWithChangeTracker) MyShipment.SetChangeTracker(Nothing) MyContext.Attach(MyShipment) MyContext.Detach(ShipmentRecord) End Using End Sub The Refresh background worker is similar, but it has a Do While block to keep it from interfering with the save worker (which doesn't appear to be working; hence the post). When I save (and it subsequently refreshes) I get the following error: The calling thread cannot access this object because a different thread owns it. I thought that with the DoWhile block, it would wait (and when i step through it does) until the save thread finished, and all would be good. But it would seem that something (either the main thread or the save thread) is still doing something that is interfering. Is there a better way of doing this? Am I doing it is a goofy kludgey fashion? Any help would be appreciated. (Apparently Firefox recognized kludgey as a word. Interesting)

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• Connection Pool Strategy: Good, Bad or Ugly?

  - by Drew

  I'm in charge of developing and maintaining a group of Web Applications that are centered around similar data. The architecture I decided on at the time was that each application would have their own database and web-root application. Each application maintains a connection pool to its own database and a central database for shared data (logins, etc.) A co-worker has been positing that this strategy will not scale because having so many different connection pools will not be scalable and that we should refactor the database so that all of the different applications use a single central database and that any modifications that may be unique to a system will need to be reflected from that one database and then use a single pool powered by Tomcat. He has posited that there is a lot of "meta data" that goes back and forth across the network to maintain a connection pool. My understanding is that with proper tuning to use only as many connections as necessary across the different pools (low volume apps getting less connections, high volume apps getting more, etc.) that the number of pools doesn't matter compared to the number of connections or more formally that the difference in overhead required to maintain 3 pools of 10 connections is negligible compared to 1 pool of 30 connections. The reasoning behind initially breaking the systems into a one-app-one-database design was that there are likely going to be differences between the apps and that each system could make modifications on the schema as needed. Similarly, it eliminated the possibility of system data bleeding through to other apps. Unfortunately there is not strong leadership in the company to make a hard decision. Although my co-worker is backing up his worries only with vagueness, I want to make sure I understand the ramifications of multiple small databases/connections versus one large database/connection pool.

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• Thread synchronization and aborting.

  - by kubal5003

  Hello, I've got a little problem with ending the work of one of my threads. First things first so here's the app "layout": Thread 1 - worker thread (C++/CLI) - runs and terminates as expected for(...) { try { if(TabuStop) return; System::Threading::Monitor::Enter("Lock1"); //some work, unmanaged code } finally { if(stop) { System::Threading::Monitor::Pulse("Lock1"); } else { System::Threading::Monitor::Pulse("Lock1"); System::Threading::Monitor::Wait("Lock1"); } } } Thread 2 - display results thread (C#) while (WorkerThread.IsAlive) { lock ("Lock1") { if (TabuEngine.TabuStop) { Monitor.Pulse("Lock1"); } else { Dispatcher.BeginInvoke(RefreshAction); Monitor.Pulse("Lock1"); Monitor.Wait("Lock1", 5000); } } // Thread.Sleep(5000); } I'm trying to shut the whole thing down from app main thread like this: TabuEngine.TabuStop = true; //terminates nicely the worker thread and if (DisplayThread.IsAlive) { DisplayThread.Abort(); } I also tried using DisplayThread.Interrupt, but it always blocks on Monitor.Wait("Lock1", 5000); and I can't get rid of it. What is wrong here? How am I supposed to perform the synchronization and let it do the work that it is supposed to do? //edit I'm not even sure now if the trick with using "Lock1" string is really working and locks are placed on the same object..

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• Best practices for (over)using Azure queues

  - by John

  Hi, I'm in the early phases of designing an Azure-based application. One of the things that attracts me to Azure is the scalability, given the variability of the demand I'm likely to expect. As such I'm trying to keep things loosely coupled so I can add instances when I need to. The recommendations I've seen for architecting an application for Azure include keeping web role logic to a minimum, and having processing done in worker roles, using queues to communicate and some sort of back-end store like SQL Azure or Azure Tables. This seems like a good idea to me as I can scale up either or both parts of the application without any issue. However I'm curious if there are any best practices (or if anyone has any experiences) for when it's best to just have the web role talk directly to the data store vs. sending data by the queue? I'm thinking of the case where I have a simple insert to do from the web role - while I could set this up as a message, send it on the queue, and have a worker role pick it up and do the insert, it seems like a lot of double-handling. However I also appreciate that it may be the case that this is better in the long run, in case the web role gets overwhelmed or more complex logic ends up being required for the insert. I realise this might be a case where the answer is "it depends entirely on the situation, check your perf metrics" - but if anyone has any thoughts I'd be very appreciative! Thanks John

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• Recommendations for IPC between parent and child processes in .NET?

  - by Jeremy

  My .NET program needs to run an algorithm that makes heavy use of 3rd party libraries (32-bit), most of which are unmanaged code. I want to drive the CPU as hard as I can, so the code runs several threads in parallel to divide up the work. I find that running all these threads simultaneously results in temporary memory spikes, causing the process' virtual memory size to approach the 2 GB limit. This memory is released back pretty quickly, but occasionally if enough threads enter the wrong sections of code at once, the process crosses the "red line" and either the unmanaged code or the .NET code encounters an out of memory error. I can throttle back the number of threads but then my CPU usage is not as high as I would like. I am thinking of creating worker processes rather than worker threads to help avoid the out of memory errors, since doing so would give each thread of execution its own 2 GB of virtual address space (my box has lots of RAM). I am wondering what are the best/easiest methods to communicate the input and output between the processes in .NET? The file system is an obvious choice. I am used to shared memory, named pipes, and such from my UNIX background. Is there a Windows or .NET specific mechanism I should use?

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