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  • Talking JavaOne with Rock Star Raghavan Srinivas

    - by Janice J. Heiss
    Raghavan Srinivas, affectionately known as “Rags,” is a two-time JavaOne Rock Star (from 2005 and 2011) who, as a Developer Advocate at Couchbase, gets his hands dirty with emerging technology directions and trends. His general focus is on distributed systems, with a specialization in cloud computing. He worked on Hadoop and HBase during its early stages, has spoken at conferences world-wide on a variety of technical topics, conducted and organized Hands-on Labs and taught graduate classes.He has 20 years of hands-on software development and over 10 years of architecture and technology evangelism experience and has worked for Digital Equipment Corporation, Sun Microsystems, Intuit and Accenture. He has evangelized and influenced the architecture of numerous technologies including the early releases of JavaFX, Java, Java EE, Java and XML, Java ME, AJAX and Web 2.0, and Java Security.Rags will be giving these sessions at JavaOne 2012: CON3570 -- Autosharding Enterprise to Social Gaming Applications with NoSQL and Couchbase CON3257 -- Script Bowl 2012: The Battle of the JVM-Based Languages (with Guillaume Laforge, Aaron Bedra, Dick Wall, and Dr Nic Williams) Rags emphasized the importance of the Cloud: “The Cloud and the Big Data are popular technologies not merely because they are trendy, but, largely due to the fact that it's possible to do massive data mining and use that information for business advantage,” he explained. I asked him what we should know about Hadoop. “Hadoop,” he remarked, “is mainly about using commodity hardware and achieving unprecedented scalability. At the heart of all this is the Java Virtual Machine which is running on each of these nodes. The vision of taking the processing to where the data resides is made possible by Java and Hadoop.” And the most exciting thing happening in the world of Java today? “I read recently that Java projects on github.com are just off the charts when compared to other projects. It's exciting to realize the robust growth of Java and the degree of collaboration amongst Java programmers.” He encourages Java developers to take advantage of Java 7 for Mac OS X which is now available for download. At the same time, he also encourages us to read the caveats. Originally published on blogs.oracle.com/javaone.

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  • Talking JavaOne with Rock Star Raghavan Srinivas

    - by Janice J. Heiss
    Raghavan Srinivas, affectionately known as “Rags,” is a two-time JavaOne Rock Star (from 2005 and 2011) who, as a Developer Advocate at Couchbase, gets his hands dirty with emerging technology directions and trends. His general focus is on distributed systems, with a specialization in cloud computing. He worked on Hadoop and HBase during its early stages, has spoken at conferences world-wide on a variety of technical topics, conducted and organized Hands-on Labs and taught graduate classes.He has 20 years of hands-on software development and over 10 years of architecture and technology evangelism experience and has worked for Digital Equipment Corporation, Sun Microsystems, Intuit and Accenture. He has evangelized and influenced the architecture of numerous technologies including the early releases of JavaFX, Java, Java EE, Java and XML, Java ME, AJAX and Web 2.0, and Java Security.Rags will be giving these sessions at JavaOne 2012: CON3570 -- Autosharding Enterprise to Social Gaming Applications with NoSQL and Couchbase CON3257 -- Script Bowl 2012: The Battle of the JVM-Based Languages (with Guillaume Laforge, Aaron Bedra, Dick Wall, and Dr Nic Williams) Rags emphasized the importance of the Cloud: “The Cloud and the Big Data are popular technologies not merely because they are trendy, but, largely due to the fact that it's possible to do massive data mining and use that information for business advantage,” he explained. I asked him what we should know about Hadoop. “Hadoop,” he remarked, “is mainly about using commodity hardware and achieving unprecedented scalability. At the heart of all this is the Java Virtual Machine which is running on each of these nodes. The vision of taking the processing to where the data resides is made possible by Java and Hadoop.” And the most exciting thing happening in the world of Java today? “I read recently that Java projects on github.com are just off the charts when compared to other projects. It's exciting to realize the robust growth of Java and the degree of collaboration amongst Java programmers.” He encourages Java developers to take advantage of Java 7 for Mac OS X which is now available for download. At the same time, he also encourages us to read the caveats.

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  • Setting up Linux VPN Client on Mint: Never sends "Set-Link-Info" packet

    - by cabanaboy
    I have tried to set up a VPN Connection on the Linux Mint disto, but could not get it working. When I use a Windows 7 VPN client it works fine. I brought up Wireshark on both Windows and Linux machine and noticed that on the Windows machine, the client never attempted to send the "Set-Link-Info" packet whereas the Windows (working) VPN client did. Why isn't the Linux Mint client sending the "Set-Link-Info" packet. I think if it did that, then my connection would work. What am I missing?

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  • Eclipse on mac: how comes that everytime I install an Eclipse plug-in on my mac I always get this er

    - by Patrick
    I'm using Eclipse for several projects on Leopard OSX. I've installed several versions (Classic, PDT, etc). When I install a new plug-in using the Help Install New Software functionality and I restart it, I always get the same error and I cannot anymore use it: !ENTRY org.eclipse.equinox.launcher 4 0 2010-04-20 17:32:42.540 !MESSAGE Exception launching the Eclipse Platform: !STACK java.lang.ClassNotFoundException: org.eclipse.core.runtime.adaptor.EclipseStarter at java.net.URLClassLoader$1.run(URLClassLoader.java:200) at java.security.AccessController.doPrivileged(Native Method) at java.net.URLClassLoader.findClass(URLClassLoader.java:188) at java.lang.ClassLoader.loadClass(ClassLoader.java:317) at java.lang.ClassLoader.loadClass(ClassLoader.java:252) at org.eclipse.equinox.launcher.Main.invokeFramework(Main.java:556) at org.eclipse.equinox.launcher.Main.basicRun(Main.java:514) at org.eclipse.equinox.launcher.Main.run(Main.java:1311) What is causing the error? How can I get these plugins to work? Thanks

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  • Logging Apparently Not Working - Can't Set Configure Replication

    - by square_eyes
    I'm using a tutorial to set up a master (single) slave setup. When I run the command show master status; I get Empty set (0.00 sec). I have done a lot of research and believe that the log file I have set up isn't being used properly. The master is a Windows server, and I am administering it through workbench. The log file (log-bin.log) I have configured in the options exists, and is accessible by 'System'. But when I open it as a text file it doesn't have any data. So I'm assuming it's not getting used properly. How can I get the logging happening so I can finish setting up this replication? Edit: Purely for reference here is the tutorial. I followed all the steps and double checked everything up until show master status.

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  • Set certain WSUS updates to auto-install

    - by Nicolas
    We're running a WSUS server for the simple purpose of caching updates. Since we are a very small network of all "power users", we've got the domain group policy for WSUS updates on the clients set to prompt for download/install. i.e. We don't want updates to install without our knowledge. But there are a few cases where it would be nice to be able to set a certain update to auto-install. e.g. Windows Defender updates, Malicious Software Removal Tool, Outlook Junk Email Filter, etc. Basically all the silly little updates that you would always install anyway and don't require a restart. Is there a way to set the general policy to prompt for download/install, but auto-install certain regular updates? P.S. WSUS itself does have the facility to auto-approve certain updates. That part works. Facts & Figures: SBS 2003 domain Windows 7 Pro clients Windows XP Pro clients

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  • Suggestion for auditd set-up

    - by JVerstry
    Hi, I am trying to learn about securing a Linux box (I am using Ubuntu). Auditd is recommended for monitoring activities on the node. I have managed to install it, but I can't find much information about proper set-up to secure my node. How should I set-up auditd to make my node more secure? What should I monitor? Why? I am looking for set-up examples and recommendation from experienced administrators. Thanks!

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  • Java web app, with plugin framework and ability to connect to source for updates

    - by lessthancommon
    I've searched all around for some good sources, but either have been searching for the wrong keywords, or I'm just missing something. I'm looking to redevelop a web app I've been using for some time now. Many parts are out of date, and we're constantly throwing in little hacks to attempt to give it new life. So what I'd like to do is re-engineer it from the ground up, built on some sort of plug-in framework. Before I continue, I'm more or less an intermediate Java programmer. In some ways, I'm hoping to use this project as a big learning experience. I've read a lot about OSGi, and it seems that's the most complete framework. Ideally, I would like an end result web app which I can run one instance as my hosting environment, and other instances can connect to it to grab new and updated plug-ins. Eventually I'll want to lock down these plug-ins based on some undecided criteria of who can get them (basically some will simply be updates, others will provide new functionality and should be "purchased" through an external system). But that will probably be handled in a later phase. There should be an administration view for managing bundles in a hot environment (looking to avoid having to restart the server for an update). I know all these things are possible, I'm just trying to find some good resources for reference. All the OSGi tutorials I'm finding seem to be too simplistic. If anyone here can guide me in the right direction on any or all of the items I'm looking for, it would be much appreciated. Also, this is my first post, so I'll take any comments/criticisms about the content of my post. Thanks!

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  • Two equal items in alternatives list

    - by Red Planet
    I want to have two JDKs. The first one was installed a long time ago to /usr/lib/jvm/java-7-oracle/. I installed the second version and executed following commands to add it to alternatives: red-planet@laptop:~$ sudo update-alternatives --install "/usr/bin/java" "java" "/opt/java_1.6.0_35/bin/java" 2 update-alternatives: using /opt/java_1.6.0_35/bin/java to provide /usr/bin/java (java) in auto mode. red-planet@laptop:~$ sudo update-alternatives --install "/usr/bin/javac" "javac" "/opt/java_1.6.0_35/bin/javac" 2 update-alternatives: using /opt/java_1.6.0_35/bin/javac to provide /usr/bin/javac (javac) in auto mode. red-planet@laptop:~$ sudo update-alternatives --install "/usr/bin/javaws" "javaws" "/opt/java_1.6.0_35/bin/javaws" 2 update-alternatives: using /opt/java_1.6.0_35/bin/javaws to provide /usr/bin/javaws (javaws) in auto mode. And configured: There are 2 choices for the alternative java (providing /usr/bin/java). Selection Path Priority Status ------------------------------------------------------------ * 0 /opt/java_1.6.0_35/bin/java 2 auto mode 1 /opt/java_1.6.0_35/bin/java 2 manual mode 2 /usr/lib/jvm/java-7-oracle/bin/java 1 manual mode Press enter to keep the current choice[*], or type selection number: Why do I have two equal items in the list?

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  • How to set up Dell OMSA tools on Debian 6 (Squeeze) (PE2950)

    - by javano
    I assume I have set up them up incorrectly or am missing a library or dependency. When I log into the OMSA web interface I can't see anything Also, omreport tells me nothing; root@box:~# omreport storage controller No controllers found I assume these two will use the same source of information so what ever is wrong will fix them both. I set up OMSA as per these instructions. Also I have compiled MegaCLI (as this is a PowerEdge 2950 with a Perc 6/i controller) and I have used that to update the RAID firmware, so that works, but the Dell tools aren't. What have I missed during set up? root@kvm1:~# cat /etc/issue Debian GNU/Linux 6.0 \n \l root@kvm1:~# uname -a Linux kvm1.mivoice.cust.vostron.net 3.4.9 #1 SMP Wed Aug 22 19:08:46 BST 2012 x86_64 GNU/Linux

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  • 'Object variable or With block variable not set' error when setting a range in VBA

    - by David Gard
    I have a function that creates a Pivot Table, but I am getting an error when I try to set a range that will be merged and have a title added to it. In the below code, pivot_title_range is a 'String' variable, and is optional when calling the funtion. title_range is a 'Range' variable. Both lines that set the range (whether or not the users declares pivot_title_range) cause the same error. If pivot_title_range = "" Then title_range = ActiveSheet.Range("B3:E4") Else title_range = ActiveSheet.Range(pivot_title_range) End If Here is the error that I am getting - Run-time error '91': Object variable or With block variable not set If required, here is a Pastebin of the full function - http://pastebin.com/L711jayc. The offending code starts on line 160. Is anybody able to tell me what I am doing wrong? Thanks.

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  • Page File - Why set one for each drive?

    - by Magic
    Hello, I have Windows Vista Business Edition running on my laptop (brand is HCL). I have 4 HDD which are as follows - C - 29.2 GB (of which only 3.68 GB is free) D - 39 GB (of which 37.8 GB is free) E - 39 GB (of which 37.3 GB is free) F - 41.6 (of which 41.4 GB is free) However, my page file settings are as below. Automatically manage paging file for all drives. Question - Why should I set one for each drive? Should I set my page file on the OS Root Drive. I happen to talk to a System Administrator in an IT company and he advised that we should never set the page file on the OS drive but on an alternate drive wherever possible. It would be really helpful, if you can guide me here or at least point me to the right resources so that I can read about paging and best practices of paging. Cheers,

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  • How to set up Google Apps (mail) MX Records on DNSMadeEasy (screen shot included)

    - by user41847
    I am attempting to complete google's mail MX setup. I would link, but new users can't have two links, and I think the following img is more important. This is what my input options are for DNS Made Easy, which manages my domain: http://img94.imageshack.us/img94/5662/dnsmadeeasy.gif I would like to confirm that I understand the fields correctly. It is my understanding that I am supposed to: Leave Name (Host) Blank Set Data to ASPMX.L.GOOGLE.COM. (and repeat for each of the server addresses provided by google) Set the MX level to what Google has in "Priority" column Set TTL as high as possible Did I get it right? The nightmare scenario is that I screw up, and bring everyone's mail down :P Thanks in advance for your time.

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  • How can I set Out-Of-Office in a shared mailbox

    - by balexandre
    I would want to set the out-of-office automatic response to all emails that arrive to our [email protected]. currently in the Outlook, I only have one mailbox (the user mailbox) but it has 2 shared mailboxes setup. I have tried to create a Rule that says: for all email received on account [email protected] forward to user [email protected] and make that user to set up the Out-of-office message, but it simply did not work, and I suspect that the rules only apply to the user account and not the shared account... How can I set Out-Of-Office in this shared mailbox ?

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  • Eclipse Java Code Formatter in NetBeans Plugin Manager

    - by Geertjan
    Great news for Eclipse refugees everywhere. Benno Markiewicz forked the Eclipse formatter plugin that I blogged about sometime ago (here and here)... and he fixed many bugs, while also adding new features. It's a handy plugin when you're (a) switching from Eclipse to NetBeans and want to continue using your old formatting rules and (b) working in a polyglot IDE team, i.e., now the formatting rules defined in Eclipse can be imported into NetBeans IDE and everyone will happily be able to conform to the same set of formatting standards. And now you can get it directly from Tools | Plugins in NetBeans IDE 7.4: News from Benno on the plugin, received from him today: The plugin is verified by the NetBeans community and available in the Plugin Manager in NetBeans IDE 7.4 (as shown above) and also at the NetBeans Plugin Portal here, where you can also read quite some info about the plugin:  http://plugins.netbeans.org/plugin/50877/eclipse-code-formatter-for-java The issue with empty undo buffer was solved with the help of junichi11: https://github.com/markiewb/eclipsecodeformatter_for_netbeans/issues/18 The issue with the lost breakpoints remains unsolved and there was no further feedback. That is the main reason why the save action isn't activated by default. See also the open known issues at https://github.com/markiewb/eclipsecodeformatter_for_netbeans/issues?state=open Features are as follows:  Global configuration and project specific configuration.  On save action, which is disabled by default. Show the used formatter as a notification, which is enabled by default.  Finally, Benno testifies to the usefulness, stability, and reliability of the plugin: I use the Eclipse formatter provided by this plugin every day at work. Before I commit, I format the sources. It works and that's it. I am pleased with it. Here's where the Eclipse formatter is defined globally in Tools | Options: And here is per-project configuration, i.e., use the Project Properties dialog of any project to override the global settings:  Interested to hear from anyone who tries the plugin and has any feedback of any kind! 

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  • JCP 2012 Award Nominations are now open!

    - by heathervc
    The 10th JCP Annual Awards Nominations are now open until 16 July 2012. Submit nominations to [email protected] or use form here. The Java Community Process (JCP) program celebrates success. Members of the community nominate worthy participants, Spec Leads, and Java Specification Requests (JSRs) in order to cheer on the hard work and creativity that produces ground-breaking results for the community and industry in the Java Standard Edition (SE), Java Enterprise Edition (EE), or Java Micro Edition (ME) platforms. The community gets together every year at the JavaOne conference to applaud in person the winners of three awards: JCP Member/Participant of the Year, Outstanding Spec Lead, and Most Significant JSR. This year’s unveiling will occur Tuesday evening, 2 October, at the Annual JCP Community Party held in San Francisco.  Nominate today...descriptions of the award categories for this year: JCP Member/Participant Of The Year - This award recognizes the corporate or individual member (either Member or Participant) who has made the most significant positive impact on the community in the past year. Leadership, investment in the community, and innovation are some of the qualities that EC Members look for in voting for this award. Outstanding Spec Lead - The role of Spec Lead is not an easy one, and the person who takes that responsibility must be, among other things, technically savvy, able to build consensus in spite of diverse corporate goals, and focused on efficiency and execution. This award recognizes the person who has brought together these qualities the best in the past year, in leading a JSR for the Java community (Java SE, Java EE or Java ME). Most Significant JSR - Specification development is key to the success of the JCP program and helps ensure we remain a fresh and vibrant community. This award recognizes the Spec Lead and Expert Group that have contributed (either in progress or final) the most significant JSR for the Java community (Java SE, Java EE or Java ME) in the past year.

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  • Project Jigsaw: On the next train

    - by Mark Reinhold
    I recently proposed to defer Project Jigsaw from Java 8 to Java 9. Feedback on the proposal was about evenly divided as to whether Java 8 should be delayed for Jigsaw, Jigsaw should be deferred to Java 9, or some other, usually less-realistic, option should be taken. The ultimate decision rested, of course, with the Java SE 8 (JSR 337) Expert Group. After due consideration, a strong majority of the EG agreed to my proposal. In light of this decision we can still make progress in Java 8 toward the convergence of the higher-end Java ME Platforms with Java SE. I previously suggested that we consider defining a small number of Profiles which would allow compact configurations of the SE Platform to be built and deployed. JEP 161 lays out a specific initial proposal for such Profiles. There is also much useful work to be done in Java 8 toward the fully-modular platform in Java 9. Alan Bateman has submitted JEP 162, which proposes some changes in Java 8 to smooth the eventual transition to modules, to provide new tools to help developers prepare for modularity, and to deprecate and then, in Java 9, actually remove certain API elements that are a significant impediment to modularization. Thanks to everyone who responded to the proposal with comments and questions. As I wrote initially, deferring Jigsaw to a Java 9 release in 2015 is by no means a pleasant decision. It does, however, still appear to be the best available option, and it is now the plan of record.

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  • Aquamacs overrides my custom-set-faces options

    - by Roberto Aloi
    I've just installed Aquamacs on my Mac. I have a .emacs file in my home, which contains all my customizations. Among these, I have a: (custom-set-faces ... ) set of lines, which seems not to be applied automatically. If I select the lines from the .emacs and manually evaluate them, everything works fine. My guess is that these options are overridden in some other place. How can I debug this? Where should I set my custom faces? Thanks guys.

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  • Powershell Set-Acl fails

    - by Ulrich
    While working on a little backup script I try to change the ACL of a file using Set-Acl in Powershell 1 on Vista and always get the following error message: Set-Acl : The security identifier is not allowed to be the owner of this object. This error persists even if I go a minimal script: $acl = Get-Acl $sourcepath$file $acl |format-list Set-Acl -path $sourcepath$file -AclObject $acl Does anyone know the reason for this error? Obviously I'm not changing the ownership of the file... BTW: What I ultimately want to achieve is to reduce all access rights to ReadAndExecute. Is there maybe an easier way of doing this in Powershell? Thanks for your help! Ulrich

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  • Advanced Experiments with JavaScript, CSS, HTML, JavaFX, and Java

    - by Geertjan
    Once you're embedding JavaScript, CSS, and HTML into your Java desktop application, via the JavaFX browser, a whole range of new possibilities open up to you. For example, here's an impressive page on-line, notice that you can drag items and drop them in new places: http://nettuts.s3.amazonaws.com/127_iNETTUTS/demo/index.html The source code of the above is provided too, so you can drop the various files directly into your NetBeans module and use the JavaFX WebEngine to load the HTML page into the JavaFX browser. Once the JavaFX browser is in a NetBeans TopComponent, you'll have the start of an off-line news composer, something like this: WebView view = new WebView(); view.setMinSize(widthDouble, heightDouble); view.setPrefSize(widthDouble, heightDouble); webengine = view.getEngine(); URL url = getClass().getResource("index.html"); webengine.load(url.toExternalForm()); webengine.getLoadWorker().stateProperty().addListener( new ChangeListener() { @Override public void changed(ObservableValue ov, State oldState, State newState) { if (newState == State.SUCCEEDED) { Document document = (Document) webengine.executeScript("document"); NodeList list = document.getElementById("columns").getChildNodes(); for (int i = 0; i < list.getLength(); i++) { EventTarget et = (EventTarget) list.item(i); et.addEventListener("click", new EventListener() { @Override public void handleEvent(Event evt) { instanceContent.add(new Date()); } }, true); } } } }); The above is the code showing how, whenever a news item is clicked, the current date can be published into the Lookup. As you can see, I have a viewer component listening to the Lookup for dates.

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  • At the Java DEMOgrounds - ZeroTurnaround and its LiveRebel 2.5

    - by Janice J. Heiss
    At the ZeroTurnaround demo, I spoke with Krishnan Badrinarayanan, their Product Marketing Manager. ZeroTurnaround, the creator of JRebel and LiveRebel, describes itself on their site as a company “dedicated to changing the way the world develops, tests and runs Java applications."“We just launched LiveRebel 2.5 today,” stated Badrinarayanan, “which enables companies to embrace the concept and practice of continuous delivery, which means having a pipeline that takes products right from the developers to an end-user, faster, more frequently -- all the while ensuring that it’s a quality product that does not break in production. So customers don’t feel the discontinuity that something has changed under them and that they can’t deal with the change. And all this happens while there is zero down time.”He pointed out that Salesforce.com is not useable from 3 a.m. to 5 a.m. on Saturday because they are engaged in maintenance. “With LiveRebel 2.5, you can unify the whole delivery chain without having any downtime at all,” he said. “There are many products that tell customers to take their tools and change how they work as an organization so that you they have to conform to the way the tool prescribes them to work as an application team. We take a more pragmatic approach. A lot of companies might use Jenkins or Bamboo to do continuous integration. We extend that. We say, take our product, take LiveRebel okay, and integrate it with Jenkins – you can do that quickly, so that, in half a day, you will be up and running. And let LiveRebel automate your deployment processes and all the automated tasks that go with it. Right from tests to the staging environment to production -- all with zero downtime and with no impact on users currently using the system.” “So if you were to make the update right now and you had 100 users on your system, they would not even know this was happening. It would maintain their sessions and transfer them over to the new version, all in the background.”

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  • How to set the laptop screen brightness programatically?

    - by zls
    I'm currently migrating to openbox without gnome session. In unity i can use the vendor keys to set the screen brightness, but in openbox I'm on my own. /sys/class/backlight/acpi_video0/brightness works fine, the problem is that I need sudo to set the brightness and that wouldn't work with keyboard mappings. xbacklight -get/set doesn't do or output anything. I don't really want to use xrandr --brightness. Are there any other options or a way to fix the problems with xbacklight or acpi_video0 ?

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  • GlassFish/Java EE Community Open Forum Tomorrow!

    - by reza_rahman
    Still have lingering questions on the goals and future of GlassFish? Want to know a little more about the upcoming GlassFish 4.0.1 release? Something on your mind about Java EE 8/GlassFish 5? You have a golden opportunity to pose your questions and speak your mind tomorrow! The good folks over at C2B2 have gone through a lot of time and effort to organize a very useful online event for the London GlassFish User Group - they are having me answer all your questions online, in real time, "face-to-face". Steve Millidge of C2B2 will be moderating the questions and joining the conversation. Did I mention the event was online, free and open to anyone? The event is tomorrow (May 30th), so make sure to register as soon as possible through the C2B2 website (the registration page has more details on the event). It will be held at 4:30 PM BST / 11:30 AM EST / 8:30 AM PST - you must register to participate. Hope to talk to you tomorrow?

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  • What is the fastest cyclic synchronization in Java (ExecutorService vs. CyclicBarrier vs. X)?

    - by Alex Dunlop
    Which Java synchronization construct is likely to provide the best performance for a concurrent, iterative processing scenario with a fixed number of threads like the one outlined below? After experimenting on my own for a while (using ExecutorService and CyclicBarrier) and being somewhat surprised by the results, I would be grateful for some expert advice and maybe some new ideas. Existing questions here do not seem to focus primarily on performance, hence this new one. Thanks in advance! The core of the app is a simple iterative data processing algorithm, parallelized to the spread the computational load across 8 cores on a Mac Pro, running OS X 10.6 and Java 1.6.0_07. The data to be processed is split into 8 blocks and each block is fed to a Runnable to be executed by one of a fixed number of threads. Parallelizing the algorithm was fairly straightforward, and it functionally works as desired, but its performance is not yet what I think it could be. The app seems to spend a lot of time in system calls synchronizing, so after some profiling I wonder whether I selected the most appropriate synchronization mechanism(s). A key requirement of the algorithm is that it needs to proceed in stages, so the threads need to sync up at the end of each stage. The main thread prepares the work (very low overhead), passes it to the threads, lets them work on it, then proceeds when all threads are done, rearranges the work (again very low overhead) and repeats the cycle. The machine is dedicated to this task, Garbage Collection is minimized by using per-thread pools of pre-allocated items, and the number of threads can be fixed (no incoming requests or the like, just one thread per CPU core). V1 - ExecutorService My first implementation used an ExecutorService with 8 worker threads. The program creates 8 tasks holding the work and then lets them work on it, roughly like this: // create one thread per CPU executorService = Executors.newFixedThreadPool( 8 ); ... // now process data in cycles while( ...) { // package data into 8 work items ... // create one Callable task per work item ... // submit the Callables to the worker threads executorService.invokeAll( taskList ); } This works well functionally (it does what it should), and for very large work items indeed all 8 CPUs become highly loaded, as much as the processing algorithm would be expected to allow (some work items will finish faster than others, then idle). However, as the work items become smaller (and this is not really under the program's control), the user CPU load shrinks dramatically: blocksize | system | user | cycles/sec 256k 1.8% 85% 1.30 64k 2.5% 77% 5.6 16k 4% 64% 22.5 4096 8% 56% 86 1024 13% 38% 227 256 17% 19% 420 64 19% 17% 948 16 19% 13% 1626 Legend: - block size = size of the work item (= computational steps) - system = system load, as shown in OS X Activity Monitor (red bar) - user = user load, as shown in OS X Activity Monitor (green bar) - cycles/sec = iterations through the main while loop, more is better The primary area of concern here is the high percentage of time spent in the system, which appears to be driven by thread synchronization calls. As expected, for smaller work items, ExecutorService.invokeAll() will require relatively more effort to sync up the threads versus the amount of work being performed in each thread. But since ExecutorService is more generic than it would need to be for this use case (it can queue tasks for threads if there are more tasks than cores), I though maybe there would be a leaner synchronization construct. V2 - CyclicBarrier The next implementation used a CyclicBarrier to sync up the threads before receiving work and after completing it, roughly as follows: main() { // create the barrier barrier = new CyclicBarrier( 8 + 1 ); // create Runable for thread, tell it about the barrier Runnable task = new WorkerThreadRunnable( barrier ); // start the threads for( int i = 0; i < 8; i++ ) { // create one thread per core new Thread( task ).start(); } while( ... ) { // tell threads about the work ... // N threads + this will call await(), then system proceeds barrier.await(); // ... now worker threads work on the work... // wait for worker threads to finish barrier.await(); } } class WorkerThreadRunnable implements Runnable { CyclicBarrier barrier; WorkerThreadRunnable( CyclicBarrier barrier ) { this.barrier = barrier; } public void run() { while( true ) { // wait for work barrier.await(); // do the work ... // wait for everyone else to finish barrier.await(); } } } Again, this works well functionally (it does what it should), and for very large work items indeed all 8 CPUs become highly loaded, as before. However, as the work items become smaller, the load still shrinks dramatically: blocksize | system | user | cycles/sec 256k 1.9% 85% 1.30 64k 2.7% 78% 6.1 16k 5.5% 52% 25 4096 9% 29% 64 1024 11% 15% 117 256 12% 8% 169 64 12% 6.5% 285 16 12% 6% 377 For large work items, synchronization is negligible and the performance is identical to V1. But unexpectedly, the results of the (highly specialized) CyclicBarrier seem MUCH WORSE than those for the (generic) ExecutorService: throughput (cycles/sec) is only about 1/4th of V1. A preliminary conclusion would be that even though this seems to be the advertised ideal use case for CyclicBarrier, it performs much worse than the generic ExecutorService. V3 - Wait/Notify + CyclicBarrier It seemed worth a try to replace the first cyclic barrier await() with a simple wait/notify mechanism: main() { // create the barrier // create Runable for thread, tell it about the barrier // start the threads while( ... ) { // tell threads about the work // for each: workerThreadRunnable.setWorkItem( ... ); // ... now worker threads work on the work... // wait for worker threads to finish barrier.await(); } } class WorkerThreadRunnable implements Runnable { CyclicBarrier barrier; @NotNull volatile private Callable<Integer> workItem; WorkerThreadRunnable( CyclicBarrier barrier ) { this.barrier = barrier; this.workItem = NO_WORK; } final protected void setWorkItem( @NotNull final Callable<Integer> callable ) { synchronized( this ) { workItem = callable; notify(); } } public void run() { while( true ) { // wait for work while( true ) { synchronized( this ) { if( workItem != NO_WORK ) break; try { wait(); } catch( InterruptedException e ) { e.printStackTrace(); } } } // do the work ... // wait for everyone else to finish barrier.await(); } } } Again, this works well functionally (it does what it should). blocksize | system | user | cycles/sec 256k 1.9% 85% 1.30 64k 2.4% 80% 6.3 16k 4.6% 60% 30.1 4096 8.6% 41% 98.5 1024 12% 23% 202 256 14% 11.6% 299 64 14% 10.0% 518 16 14.8% 8.7% 679 The throughput for small work items is still much worse than that of the ExecutorService, but about 2x that of the CyclicBarrier. Eliminating one CyclicBarrier eliminates half of the gap. V4 - Busy wait instead of wait/notify Since this app is the primary one running on the system and the cores idle anyway if they're not busy with a work item, why not try a busy wait for work items in each thread, even if that spins the CPU needlessly. The worker thread code changes as follows: class WorkerThreadRunnable implements Runnable { // as before final protected void setWorkItem( @NotNull final Callable<Integer> callable ) { workItem = callable; } public void run() { while( true ) { // busy-wait for work while( true ) { if( workItem != NO_WORK ) break; } // do the work ... // wait for everyone else to finish barrier.await(); } } } Also works well functionally (it does what it should). blocksize | system | user | cycles/sec 256k 1.9% 85% 1.30 64k 2.2% 81% 6.3 16k 4.2% 62% 33 4096 7.5% 40% 107 1024 10.4% 23% 210 256 12.0% 12.0% 310 64 11.9% 10.2% 550 16 12.2% 8.6% 741 For small work items, this increases throughput by a further 10% over the CyclicBarrier + wait/notify variant, which is not insignificant. But it is still much lower-throughput than V1 with the ExecutorService. V5 - ? So what is the best synchronization mechanism for such a (presumably not uncommon) problem? I am weary of writing my own sync mechanism to completely replace ExecutorService (assuming that it is too generic and there has to be something that can still be taken out to make it more efficient). It is not my area of expertise and I'm concerned that I'd spend a lot of time debugging it (since I'm not even sure my wait/notify and busy wait variants are correct) for uncertain gain. Any advice would be greatly appreciated.

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  • NPE when drawing TabWidget in android (only on HTC Magic?)

    - by David Hedlund
    I've received report from the user of an app I've written that he gets FC whenever starting a certain activity. I have not been able to reproduce the issue on the emulator or on my HTC Hero (running 1.5), but this user running HTC Magic (with 1.6) is facing this error every time. What bothers me is that no single step in the stacktrace actually includes any code in my app (com.filmtipset) 01-07 00:10:26.773 I/ActivityManager( 141): Starting activity: Intent { cmp=com.filmtipset/.ViewMovie (has extras) } 01-07 00:10:27.023 D/AndroidRuntime( 2402): Shutting down VM 01-07 00:10:27.023 W/dalvikvm( 2402): threadid=3: thread exiting with uncaught exception (group=0x4001e170) 01-07 00:10:27.023 E/AndroidRuntime( 2402): Uncaught handler: thread main exiting due to uncaught exception 01-07 00:10:27.083 E/AndroidRuntime( 2402): java.lang.NullPointerException 01-07 00:10:27.083 E/AndroidRuntime( 2402): at android.widget.TabWidget.dispatchDraw(TabWidget.java:173) 01-07 00:10:27.083 E/AndroidRuntime( 2402): at android.view.ViewGroup.drawChild(ViewGroup.java:1529) 01-07 00:10:27.083 E/AndroidRuntime( 2402): at android.view.ViewGroup.dispatchDraw(ViewGroup.java:1258) 01-07 00:10:27.083 E/AndroidRuntime( 2402): at android.view.ViewGroup.drawChild(ViewGroup.java:1529) 01-07 00:10:27.083 E/AndroidRuntime( 2402): at android.view.ViewGroup.dispatchDraw(ViewGroup.java:1258) 01-07 00:10:27.083 E/AndroidRuntime( 2402): at android.view.ViewGroup.drawChild(ViewGroup.java:1529) 01-07 00:10:27.083 E/AndroidRuntime( 2402): at android.view.ViewGroup.dispatchDraw(ViewGroup.java:1258) 01-07 00:10:27.083 E/AndroidRuntime( 2402): at android.view.View.draw(View.java:6552) 01-07 00:10:27.083 E/AndroidRuntime( 2402): at android.widget.FrameLayout.draw(FrameLayout.java:352) 01-07 00:10:27.083 E/AndroidRuntime( 2402): at android.view.ViewGroup.drawChild(ViewGroup.java:1531) 01-07 00:10:27.083 E/AndroidRuntime( 2402): at android.view.ViewGroup.dispatchDraw(ViewGroup.java:1258) 01-07 00:10:27.083 E/AndroidRuntime( 2402): at android.view.View.draw(View.java:6552) 01-07 00:10:27.083 E/AndroidRuntime( 2402): at android.widget.FrameLayout.draw(FrameLayout.java:352) 01-07 00:10:27.083 E/AndroidRuntime( 2402): at com.android.internal.policy.impl.PhoneWindow$DecorView.draw(PhoneWindow.java:1883) 01-07 00:10:27.083 E/AndroidRuntime( 2402): at android.view.ViewRoot.draw(ViewRoot.java:1332) 01-07 00:10:27.083 E/AndroidRuntime( 2402): at android.view.ViewRoot.performTraversals(ViewRoot.java:1097) 01-07 00:10:27.083 E/AndroidRuntime( 2402): at android.view.ViewRoot.handleMessage(ViewRoot.java:1613) 01-07 00:10:27.083 E/AndroidRuntime( 2402): at android.os.Handler.dispatchMessage(Handler.java:99) 01-07 00:10:27.083 E/AndroidRuntime( 2402): at android.os.Looper.loop(Looper.java:123) 01-07 00:10:27.083 E/AndroidRuntime( 2402): at android.app.ActivityThread.main(ActivityThread.java:4320) 01-07 00:10:27.083 E/AndroidRuntime( 2402): at java.lang.reflect.Method.invokeNative(Native Method) 01-07 00:10:27.083 E/AndroidRuntime( 2402): at java.lang.reflect.Method.invoke(Method.java:521) 01-07 00:10:27.083 E/AndroidRuntime( 2402): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:791) 01-07 00:10:27.083 E/AndroidRuntime( 2402): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:549) 01-07 00:10:27.083 E/AndroidRuntime( 2402): at dalvik.system.NativeStart.main(Native Method) Full dump here if I've missed anything of interest I'm guessing, then, that there might be something wrong with my layout. It's quite verbose, so I'm posting it here, rather than pasting the whole thing on SO. There is a tabwidget, where one tab is connected to the scrollview, svFilmInfo, and one to the linear layout llComments. The tab host is populated as such: Drawable commentSelector = getResources().getDrawable(R.drawable.tabcomment); Drawable infoSelector = getResources().getDrawable(R.drawable.tabinfo); mTabHost = getTabHost(); mTabHost.getTabWidget().setBackgroundColor(Color.BLACK); mTabHost.addTab(mTabHost.newTabSpec("tabInfo").setIndicator("Filminfo", infoSelector).setContent(R.id.svFilmInfo)); mTabHost.addTab(mTabHost.newTabSpec("tabInfo").setIndicator("Kommentarer", commentSelector).setContent(R.id.llComments)); Since I cannot reproduce the error myself, and since I cannot find any mention in the stack trace of what might be causing the error, I don't quite know where to start troubleshooting this. I'd appreciate any pointers.

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