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• How can I reduce the number of spammers registering with my phpBB site?

  - by Jayapal Chandran

  I have a site which runs phpBB, on this site I have enabled user authentication through email when registering enabled captcha However I still get spam users every 20 to 30 minutes. Is there anything I can do to prevent this with the ucp.php file? I have already loaded a large list of IP addresses yet there are spam users registering all the time. One thing I can do is I can check the bounce mail to find the username and can pipe bounced mails to a php script and immediately delete that user, but I have not got any bounce back from hotmail or some other email clients. So this way it will catch hold of a certain percent of spam users but there are still a huge amount of users spamming. What else can I do to prevent spammers abusing my phpBB site?

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• Node Serialization in NetBeans Platform 7.0

  - by Geertjan

  Node serialization makes sense when you're not interested in the data (since that should be serialized to a database), but in the state of the application. For example, when the application restarts, you want the last selected node to automatically be selected again. That's not the kind of information you'll want to store in a database, hence node serialization is not about data serialization but about application state serialization. I've written about this topic in October 2008, here and here, but want to show how to do this again, using NetBeans Platform 7.0. Somewhere I remember reading that this can't be done anymore and that's typically the best motivation for me, i.e., to prove that it can be done after all. Anyway, in a standard POJO/Node/BeanTreeView scenario, do the following: Remove the "@ConvertAsProperties" annotation at the top of the class, which you'll find there if you used the Window Component wizard. We're not going to use property-file based serialization, but plain old java.io.Serializable  instead. In the TopComponent, assuming it is named "UserExplorerTopComponent", typically at the end of the file, add the following: @Override public Object writeReplace() { //We want to work with one selected item only //and thanks to BeanTreeView.setSelectionMode, //only one node can be selected anyway: Handle handle = NodeOp.toHandles(em.getSelectedNodes())[0]; return new ResolvableHelper(handle); } public final static class ResolvableHelper implements Serializable { private static final long serialVersionUID = 1L; public Handle selectedHandle; private ResolvableHelper(Handle selectedHandle) { this.selectedHandle = selectedHandle; } public Object readResolve() { WindowManager.getDefault().invokeWhenUIReady(new Runnable() { @Override public void run() { try { //Get the TopComponent: UserExplorerTopComponent tc = (UserExplorerTopComponent) WindowManager.getDefault().findTopComponent("UserExplorerTopComponent"); //Get the display text to search for: String selectedDisplayName = selectedHandle.getNode().getDisplayName(); //Get the root, which is the parent of the node we want: Node root = tc.getExplorerManager().getRootContext(); //Find the node, by passing in the root with the display text: Node selectedNode = NodeOp.findPath(root, new String[]{selectedDisplayName}); //Set the explorer manager's selected node: tc.getExplorerManager().setSelectedNodes(new Node[]{selectedNode}); } catch (PropertyVetoException ex) { Exceptions.printStackTrace(ex); } catch (IOException ex) { Exceptions.printStackTrace(ex); } } }); return null; } } Assuming you have a node named "UserNode" for a type named "User" containing a property named "type", add the bits in bold below to your "UserNode": public class UserNode extends AbstractNode implements Serializable { static final long serialVersionUID = 1L; public UserNode(User key) { super(Children.LEAF); setName(key.getType()); } @Override public Handle getHandle() { return new CustomHandle(this, getName()); } public class CustomHandle implements Node.Handle { static final long serialVersionUID = 1L; private AbstractNode node = null; private final String searchString; public CustomHandle(AbstractNode node, String searchString) { this.node = node; this.searchString = searchString; } @Override public Node getNode() { node.setName(searchString); return node; } } } Run the application and select one of the user nodes. Close the application. Start it up again. The user node is not automatically selected, in fact, the window does not open, and you will see this in the output: Caused: java.io.InvalidClassException: org.serialization.sample.UserNode; no valid constructor Read this article and then you'll understand the need for this class: public class BaseNode extends AbstractNode { public BaseNode() { super(Children.LEAF); } public BaseNode(Children kids) { super(kids); } public BaseNode(Children kids, Lookup lkp) { super(kids, lkp); } } Now, instead of extending AbstractNode in your UserNode, extend BaseNode. Then the first non-serializable superclass of the UserNode has an explicitly declared no-args constructor, Do the same as the above for each node in the hierarchy that needs to be serialized. If you have multiple nodes needing serialization, you can share the "CustomHandle" inner class above between all the other nodes, while all the other nodes will also need to extend BaseNode (or provide their own non-serializable super class that explicitly declares a no-args constructor). Now, when I run the application, I select a node, then I close the application, restart it, and the previously selected node is automatically selected when the application has restarted.

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• Implementation of instance testing in Java, C++, C#

  - by Jake

  For curiosity purposes as well as understanding what they entail in a program, I'm curious as to how instance testing (instanceof/is/using dynamic_cast in c++) works. I've tried to google it (particularly for java) but the only pages that come up are tutorials on how to use the operator. How do the implementations vary across those langauges? How do they treat classes with identical signatures? Also, it's been drilled into my head that using instance testing is a mark of bad design. Why exactly is this? When is that applicable, instanceof should still be used in methods like .equals() and such right? I was also thinking of this in the context of exception handling, again particularly in Java. When you have mutliple catch statements, how does that work? Is that instance testing or is it just resolved during compilation where each thrown exception would go to?

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• New Time Zone Patch DST V18 is available

  - by Mike Dietrich

  Sorry for not updating the blog more often at the moment - but more updates will come soon as I play around with Oracle Restart and single instance databases in ASM with Oracle 11.2. Just on the side there's a new time zone patch to DST V18 available since May 2012. You can download it via PATCH download from MOS with the patch number: 13417321 What do you think? Will Lufthansa operate a faster jet the other night? Will the jet stream be more powerful? Or a better type of fuel? Or is it just the travel portal which hasn't applied the correct time zone patches to catch DST change that night in the US whereas it happens two weeks later in Europe? Guess ... And please see the readme about how to apply the patch and our slides about why time zone patching may be important even in your environment RDBMS bug: Bug 13417321: DST 18 : HALF YEARLY DST PATCHES, MAY 2012 OJVM Bug 14112098 - dst changes for dstv18 (tzdata2012c) - need ojvm fix

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• Think before you animate

  - by David Paquette

  Animations are becoming more and more common in our applications.  With technologies like WPF, Silverlight and jQuery, animations are becoming easier for developers to use (and abuse).  When used properly, animation can augment the user experience.  When used improperly, animation can degrade the user experience.  Sometimes, the differences can be very subtle. I have recently made use of animations in a few projects and I very quickly realized how easy it is to abuse animation techniques.  Here are a few things I have learned along the way. 1) Don’t animate for the sake of animating We’ve all seen the PowerPoint slides with annoying slide transitions that animate 20 different ways.  It’s distracting and tacky.  The same holds true for your application.  While animations are fun and becoming easy to implement, resist the urge to use the technology just because you think the technology is amazing.   2) Animations should (and do) have meaning I recently built a simple Windows Phone 7 (WP7) application, Steeped (download it here).  The application has 2 pages.  The first page lists a number of tea types.  When the user taps on one of the tea types, the application navigates to the second page with information about that tea type and some options for the user to choose from.       One of the last things I did before submitting Steeped to the marketplace was add a page transition between the 2 pages.  I choose the Slide / Fade Out transition.  When the user selects a tea type, the main page slides to the left and fades out.  At the same time, the details page slides in from the right and fades in.  I tested it and thought it looked great so I submitted the app.  A few days later, I asked a friend to try the app.  He selected a tea type, and I was a little surprised by how he used the app.  When he wanted to navigate back to the main page, instead of pressing the back button on the phone, he tried to use a swiping gesture.  Of course, the swiping gesture did nothing because I had not implemented that feature.  After thinking about it for a while, I realized that the page transition I had chosen implied a particular behaviour.  As a user, if an action I perform causes an item (in this case the page) to move, then my expectation is that I should be able to move it back.  I have since added logic to handle the swipe gesture and I think the app flows much better now. When using animation, it pays to ask yourself:  What story does this animation tell my users?   3) Watch the replay Some animations might seem great initially but can get annoying over time.  When you use an animation in your application, make sure you try using it over and over again to make sure it doesn’t get annoying.  When I add an animation, I try watch it at least 25 times in a row.  After watching the animation repeatedly, I can make a more informed decision whether or not I should keep the animation.  Often, I end up shortening the length of the animations.   4) Don’t get in the users way An animation should never slow the user down.  When implemented properly, an animation can give a perceived bump in performance.  A good example of this is a the page transitions in most of the built in apps on WP7.  Obviously, these page animations don’t make the phone any faster, but they do provide a more responsive user experience.  Why?  Because most of the animations begin as soon as the user has performed some action.  The destination page might not be fully loaded yet, but the system responded immediately to user action, giving the impression that the system is more responsive.  If the user did not see anything happen until after the destination page was fully loaded, the application would feel clumsy and slow.  Also, it is important to make sure the animation does not degrade the performance (or perceived performance) of the application.   Jut a few things to consider when using animations.  As is the case with many technologies, we often learn how to misuse it before we learn how to use it effectively.

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• I have a stacktrace and limit of 250 characters for a bug report

  - by George Duckett

  I'm developing an xbox indie game and as a last-resort I have a try...catch encompassing everything. At this point if an exception is raised I can get the user to send me a message through the xbox however the limit is 250 characters. How can I get the most value out of my 250 characters? I don't want to do any encoding / compressing at least initially. Any solution to this problem could be compressed if needed as a second step anyway. I'm thinking of doing things like turning this: at EasyStorage.SaveDevice.VerifyIsReady() at EasyStorage.SaveDevice.Save(String containerName, String fileName) into this (drop the repeated namespace/class and method parameter names): at EasyStorage.SaveDevice.VerifyIsReady() at ..Save(String, String) Or maybe even just including the inner-most method, then only line numbers up the stack etc. TL;DR: Given an exception with a stacktrace how would you get the most useful debugging infromation out of 250 characters? (It will be a .net exception/stacktrace)

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• Meet up with JCP at Devoxx - 13 - 16 November

  - by Heather VanCura

  The JCP will be back at Devoxx this year:-).  If you are attending, you can catch either Patrick or Heather at one of these events... Tuesday - OpenJDK Lab, and then we will move over to the Hackergarten (TCK/unit testing); or Beer Bash at Oracle Booth-17:30–19:30. Wednesday - Beer Bash at Oracle Booth-18:00–20:00! Thursday - JCP session-12:00:  The JCP Program: More than 101 Ways to Influence the Future of the Java Platform ; Patrick Curran, Chair of the JCP & Heather VanCura, JCP Manager; or Beer Bash at Oracle Booth-18:00–20:00. Oracle booth twiki Oracle Session listing

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• Silverlight and Windows Phone 7 Sessions from MIX 10

  I had a great time at MIX 10 last week meeting so many people and being part of so  much of the activities. One of the side effects is that it was next to impossible to catch all of the great content while at MIX, so Ive been catching up by watching many of the videos online. Here is a list with all of the Windows Phone 7 and Silverlight sessions where you can grab the videos and/or slides.   Title WMV ...Did you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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• Timeout when trying to install ubuntu 12.04

  - by Oskars

  When i click on "try ubuntu" after booting it from a USB the screen goes black and a lot of text comes out. But after a while it says "timeout: killing /blablabalba" or something like and it just keep on saying that. What have I done wrong? <.< My computer is a Acer ASPIRE M5201 if that is of any importance. Edit: I noticed now that before it says "timeout" it says something about not supporting "DNS" or "Asn" or something like that. I'm not sure if it was exactly dns and asn but do this mean that I can't run ubuntu on this computer? Edit2: The exact strings are: "[sdg] Write cache: disabled, read cache: enabled, doesn't support DPO or FUA " "timeout: killing '/sbin/modprobe -bv pci:v00001002d00"(and more nubmers wich I didn't catch)

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• How Often do You Change E-mail Addresses? [Poll]

  - by Asian Angel

  Recently we ran across an article about a man who consistently changes his e-mail address every 20 months. Why? To throw off spam. With that in mind we became curious and decided to ask how often you change your e-mail addresses… Everyone has their own method for dealing with the bane known as spam whether it is heavy filtering, separate accounts to catch possible spam activity, abandoning swamped accounts, etc. Here is your opportunity to share how you deal with spam, protect your accounts, and to voice your thoughts regarding consistent timed changes to new accounts as mentioned in the article linked to below. How-To Geek Polls require Javascript. Please Click Here to View the Poll. How Frequently Do You Change Your Email Address? [Apartment Therapy] 6 Ways Windows 8 Is More Secure Than Windows 7 HTG Explains: Why It’s Good That Your Computer’s RAM Is Full 10 Awesome Improvements For Desktop Users in Windows 8

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• SharePoint 2010 Diagnostic Studio Remote Diag

  - by juanlarios

  I have had some time this week to try out some tools that I have been meaning to try out. This week I am trying out the SP 2010 Diagnostic Studio. I installed it successfully and tried it on my development evironment. I was able to build a report and a snapshot of the environment. I decided to turn my attention to my Employer's intranet environment. This would allow me to analyze it and measure it against benchmarks. I didn't want to install the Diagnostic studio on the Production Envorinment, lucky for me, the Diagnostic studio can be run remotely, well...kind of. Issue My development environment is a stand alone, full installation of SharePoint 2010 Server. It has Office 2010, SQL 2008 Enterprise, a DC...well you get the point, it's jammed packed! But more importantly it's a stand alone, self contained VM environment. Well Microsoft has instructions as to how to connect remotely with Diagnostic Studio here. The deciving part of this is that the SP2010DS prompts you for credentails. So I thought I was getting the right account to run the reports. I tried all the Power Shell commands in the link above but I still ended up getting the following errors: 06/28/2011 12:50:18    Connecting to remote server failed with the following error message : The WinRM client cannot process the request...If the SPN exists, but CredSSP cannot use Kerberos to validate the identity of the target computer and you still want to allow the delegation of the user credentials to the target computer, use gpedit.msc and look at the following policy: Computer Configuration -> Administrative Templates -> System -> Credentials Delegation -> Allow Fresh Credentials with NTLM-only Server Authentication.  Verify that it is enabled and configured with an SPN appropriate for the target computer. For example, for a target computer name "myserver.domain.com", the SPN can be one of the following: WSMAN/myserver.domain.com or WSMAN/*.domain.com. Try the request again after these changes. For more information, see the about_Remote_Troubleshooting Help topic. 06/28/2011 12:54:47    Access to the path '\\<targetserver>\C$\Users\<account logging in>\AppData\Local\Temp' is denied. You might also get an error message like this: The WinRM client cannot process the request. A computer policy does not allow the delegation of the user credentials to the target computer. Explanation After looking at the event logs on the target environment, I noticed that there were a several Security Exceptions. After looking at the specifics around who was denied access, I was able to see the account that was being denied access, it was the client machine administrator account. Well of course that was never going to work!!! After some quick Googling, the last error message above will lead you to edit the Local Group Policy on the client server. And although there are instructions from microsoft around doing this, it really will not work in this scenario. Notice the Description and how it only applices to authentication mentioned? Resolution I can tell you what I did, but I wish there was a better way but I simply don't know if it's duable any other way. Because my development environment had it's own DC, I didn't really want to mess with Kerberos authentication. I would also not be smart to connect that server to the domain, considering it has it's own DC. I ended up installing SharePoint 2010 Diagnostic Studio on another Windows 7 Dev environment I have, and connected the machien to the domain. I ran all the necesary remote credentials commands mentioned here. Those commands add the group policy for you! Once I did this I was able to authenticate properly and I was able to get the reports. Conclusion   You can run SharePoint 2010 Diagnostic Studio Remotely but it will require some specific scenarions. A couple of things I should mention is that as far as I understand, SP2010 DS, will install agents on your target environment to run tests and retrieve the data. I was a Farm Administrator, and also a Server Admin on SharePoint Server. I am not 100% sure if you need all those permissions but I that's just what I have to my internal intranet.   I deally I would like to have a machine that I can have SharePoint 2010 DIagnostic Studio installed and I can run that against client environments. It appears that I will not be able to do that, unless I enable Kerberos on my Windows 7 Machine now. If you have it installed in the same way I would like to have it, please let me know, I'll keep trying to get what I'm after. Hope this helps someone out there doing the same.

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• Is there a command-line utility app which can locate a specific block of lines in a text file?

  - by fred.bear

  The text "search and replace" utility programs I've seen, seem to only search on a line-by-line basis... Is there a command-line tool which can locate one block of lines (in a text file), and replace it with another block of lines.? For example: Does the test file file contain this exact group of lines: 'Twas brillig, and the slithy toves Did gyre and gimble in the wabe: All mimsy were the borogoves, And the mome raths outgrabe. 'Beware the Jabberwock, my son! The jaws that bite, the claws that catch! Beware the Jubjub bird, and shun The frumious Bandersnatch!' I want this, so that I can replace multiple lines of text in a file and know I'm not overwriting the wrong lines. I would never replace "The Jabberwocky" (Lewis Carroll), but it makes a novel example :)

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• Why does pasting sometimes not work in gnome-terminal?

  - by Matthew

  Ctrl + Shift + C and Ctrl + Shift + V are supposed to replace the normal Ctrl + C and Ctrl + V in gnome-terminal. Sometimes they work, but usually they have no effect. What are some potential reasons for this? I'm not sure what other information to give. Edit: It seems that manually selecting Paste from the Edit menu does not work either. Right click > Paste works, but Edit > Paste does not. Copying works, but pasting does not. Also, I have vi-mode enabled (set -o vi in my ~/.bashrc). Could this have something to do with it? Edit: Here is a video demonstrating the problem. I used Screenkey (in "raw" mode, to catch "shift") to show what keys I am pressing.

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• Active - like-minded Java mailing lists

  - by Lewis Robbins

  I need to find an active Java mailing list, I have looked onto the GNU Java mailing list, to my surprise there had been not too much activity this month, it also focused on any GNU related Java - I'd really help me progress my Java ability, if I had an active, likeminded Java mailing list. Questions' that are not suited to Stackoverflow, or provide little benefit to any user that see's the question: discussing a new API change; best practices; open source discussion; trivia type questions on Java ArrayList boxining-unboxing; Community atmosphere. I also read Jon Skeets blog post about his previous Java/C# mailing lists examples - I did not catch any names, though I did they would be of benefit to me, if I had access to any of them.

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• Webcast Replay: Extreme Performance for Consolidated Workloads with Oracle Exadata

  - by kimberly.billings

  If you missed our live webcast Extreme Performance for Consolidated Workloads with Oracle Exadata last week, the replay is now available. Watch the free on-demand webcast in which Tim Shetler, Vice President of Oracle Database Product Management, and Richard Exley, Consulting Member of Technical Staff, discuss how Oracle Exadata can help you can significantly improve application performance and reduce infrastructure costs by consolidating transaction processing, data warehousing, or mixed workloads on Oracle Exadata. Note: (1) Turn off pop-up blockers if the slides do not advance automatically. (2) Slides are available for download. var gaJsHost = (("https:" == document.location.protocol) ? "https://ssl." : "http://www."); document.write(unescape("%3Cscript src='" + gaJsHost + "google-analytics.com/ga.js' type='text/javascript'%3E%3C/script%3E")); try { var pageTracker = _gat._getTracker("UA-13185312-1"); pageTracker._trackPageview(); } catch(err) {}

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• Integrating a Progress Bar into a Wizard

  - by Geertjan

  Normally, when you create a wizard, as described here, and you have your own iterator, you'll have a class signature like this: public final class MyWizardWizardIterator implements WizardDescriptor.InstantiatingIterator<WizardDescriptor> { Let's now imagine that you've got some kind of long running process your wizard needs to perform. Maybe the wizard needs to connect to something, which could take some time. Start by adding a new dependency on the Progress API, which gives you the classes that access the NetBeans Platform's progress functionality. Now all we need to do is change the class signature very slightly: public final class MyWizardWizardIterator implements WizardDescriptor.ProgressInstantiatingIterator<WizardDescriptor> { Take a look at the part of the signature above that is highlighted. I.e., use WizardDescriptor.ProgressInstantiatingIterator instead of WizardDescriptor.InstantiatingIterator. Now you will need to implement a new instantiate method, one that receives a ProgressHandle. The other instantiate method, i.e., the one that already existed, should never be accessed anymore, and so you can add an assert to that effect: @Override public Set<?> instantiate() throws IOException {     throw new AssertionError("instantiate(ProgressHandle) " //NOI18N             + "should have been called"); //NOI18N } @Override public Set instantiate(ProgressHandle ph) throws IOException {     return Collections.emptySet(); } OK. Let's now add some code to make our progress bar work: @Override public Set instantiate(ProgressHandle ph) throws IOException {     ph.start();     ph.progress("Processing...");     try {         //Simulate some long process:         Thread.sleep(2500);     } catch (InterruptedException ex) {         Exceptions.printStackTrace(ex);     }     ph.finish();     return Collections.emptySet(); } And, maybe even more impressive, you can also do this: @Override public Set instantiate(ProgressHandle ph) throws IOException {     ph.start(1000);     ph.progress("Processing...");     try {         //Simulate some long process:         ph.progress("1/4 complete...", 250);         Thread.sleep(2500);         ph.progress("1/2 complete...", 500);         Thread.sleep(5000);         ph.progress("3/4 complete...", 750);         Thread.sleep(7500);         ph.progress("Complete...", 1000);         Thread.sleep(1000);     } catch (InterruptedException ex) {         Exceptions.printStackTrace(ex);     }     ph.finish();     return Collections.emptySet(); } The screenshots above show you what you should see when the Finish button is clicked in each case.

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• ubuntu 14 painfully slow on dell r200

  - by sirmonkey

  I didn't notice it at first. The machines (there is 20 plus) are to be used a simple file servers. It wasn't until samba just wouldn't act right that I installed a desktop gui and started more diagnoseing the problem did I catch the slow preformance... I've tested 4 servers they all suck. And windows 7 runs fantastic on them. I have Google and searched. But nothing to explain this. The easy test is dmesg is so slow you can almost read it. I'm guessing it's an apic or cpu power management issue. What output would you all like????? It is a core2 machine with 4Gb of ram. On board data.

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• Checking for DBNull

  - by Jim Lahman

  Using a table adapter to a SQL Server database table that returns a NULL record.  We determine the fields are NULL by comparing against System.DBNull Looking the NULL records in SQL Management studio   Using a table adapter to retrieve a record   1: try 2: { 3: this.vTrackingTableAdapter.FillByTrkZone(this.dsL1Write.vTracking, iTrkZone); 4: } 5: catch (Exception ex) 6: { 7: sLogMessage = String 8: .Format("Error getting coil number from tracking table at {0} - {1}", 9: sTrkName, 10: ex.Message); 11: throw new CannotReadTrackingTableException(sLogMessage); 12: }   Looking at the record as it returned from the table adapter:   ItemArrayObject Column [0] ChargeCoilNumber [1] HeadWeldZone [2] TailWeldZone [3] ZoneLen [4] ZoneCoilLen [5] Confirmed [6] Validated [7] EntryWidth [8] EntryThickness   Since each item in the ItemArray is an object, we can test for null   1: if (dsL1Write.vTracking.Rows[0].ItemArray[0] == System.DBNull.Value) 2: { 3: throw new NoCoilAtPORException("NULL coil found at tracking zone " + sTrkName); 4: }   If no records were returned by the table adapter 1: if (dsL1Write.vTracking.Rows.Count == 0) 2: { 3: throw new NoCoilAtPORException("No coils found at tracking zone " + sTrkName); 4: }

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• Performance triage

  - by Dave

  Folks often ask me how to approach a suspected performance issue. My personal strategy is informed by the fact that I work on concurrency issues. (When you have a hammer everything looks like a nail, but I'll try to keep this general). A good starting point is to ask yourself if the observed performance matches your expectations. Expectations might be derived from known system performance limits, prototypes, and other software or environments that are comparable to your particular system-under-test. Some simple comparisons and microbenchmarks can be useful at this stage. It's also useful to write some very simple programs to validate some of the reported or expected system limits. Can that disk controller really tolerate and sustain 500 reads per second? To reduce the number of confounding factors it's better to try to answer that question with a very simple targeted program. And finally, nothing beats having familiarity with the technologies that underlying your particular layer. On the topic of confounding factors, as our technology stacks become deeper and less transparent, we often find our own technology working against us in some unexpected way to choke performance rather than simply running into some fundamental system limit. A good example is the warm-up time needed by just-in-time compilers in Java Virtual Machines. I won't delve too far into that particular hole except to say that it's rare to find good benchmarks and methodology for java code. Another example is power management on x86. Power management is great, but it can take a while for the CPUs to throttle up from low(er) frequencies to full throttle. And while I love "turbo" mode, it makes benchmarking applications with multiple threads a chore as you have to remember to turn it off and then back on otherwise short single-threaded runs may look abnormally fast compared to runs with higher thread counts. In general for performance characterization I disable turbo mode and fix the power governor at "performance" state. Another source of complexity is the scheduler, which I've discussed in prior blog entries. Lets say I have a running application and I want to better understand its behavior and performance. We'll presume it's warmed up, is under load, and is an execution mode representative of what we think the norm would be. It should be in steady-state, if a steady-state mode even exists. On Solaris the very first thing I'll do is take a set of "pstack" samples. Pstack briefly stops the process and walks each of the stacks, reporting symbolic information (if available) for each frame. For Java, pstack has been augmented to understand java frames, and even report inlining. A few pstack samples can provide powerful insight into what's actually going on inside the program. You'll be able to see calling patterns, which threads are blocked on what system calls or synchronization constructs, memory allocation, etc. If your code is CPU-bound then you'll get a good sense where the cycles are being spent. (I should caution that normal C/C++ inlining can diffuse an otherwise "hot" method into other methods. This is a rare instance where pstack sampling might not immediately point to the key problem). At this point you'll need to reconcile what you're seeing with pstack and your mental model of what you think the program should be doing. They're often rather different. And generally if there's a key performance issue, you'll spot it with a moderate number of samples. I'll also use OS-level observability tools to lock for the existence of bottlenecks where threads contend for locks; other situations where threads are blocked; and the distribution of threads over the system. On Solaris some good tools are mpstat and too a lesser degree, vmstat. Try running "mpstat -a 5" in one window while the application program runs concurrently. One key measure is the voluntary context switch rate "vctx" or "csw" which reflects threads descheduling themselves. It's also good to look at the user; system; and idle CPU percentages. This can give a broad but useful understanding if your threads are mostly parked or mostly running. For instance if your program makes heavy use of malloc/free, then it might be the case you're contending on the central malloc lock in the default allocator. In that case you'd see malloc calling lock in the stack traces, observe a high csw/vctx rate as threads block for the malloc lock, and your "usr" time would be less than expected. Solaris dtrace is a wonderful and invaluable performance tool as well, but in a sense you have to frame and articulate a meaningful and specific question to get a useful answer, so I tend not to use it for first-order screening of problems. It's also most effective for OS and software-level performance issues as opposed to HW-level issues. For that reason I recommend mpstat & pstack as my the 1st step in performance triage. If some other OS-level issue is evident then it's good to switch to dtrace to drill more deeply into the problem. Only after I've ruled out OS-level issues do I switch to using hardware performance counters to look for architectural impediments.

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• A Patent for Workload Management Based on Service Level Objectives

  - by jsavit

  I'm very pleased to announce that after a tiny :-) wait of about 5 years, my patent application for a workload manager was finally approved. Background Many operating systems have a resource manager which lets you control machine resources. For example, Solaris provides controls for CPU with several options: shares for proportional CPU allocation. If you have twice as many shares as me, and we are competing for CPU, you'll get about twice as many CPU cycles), dedicated CPU allocation in which a number of CPUs are exclusively dedicated to an application's use. You can say that a zone or project "owns" 8 CPUs on a 32 CPU machine, for example. And, capped CPU in which you specify the upper bound, or cap, of how much CPU an application gets. For example, you can throttle an application to 0.125 of a CPU. (This isn't meant to be an exhaustive list of Solaris RM controls.) Workload management Useful as that is (and tragic that some other operating systems have little resource management and isolation, and frighten people into running only 1 app per OS instance - and wastefully size every server for the peak workload it might experience) that's not really workload management. With resource management one controls the resources, and hope that's enough to meet application service objectives. In fact, we hold resource distribution constant, see if that was good enough, and adjust resource distribution if that didn't meet service level objectives. Here's an example of what happens today: Let's try 30% dedicated CPU. Not enough? Let's try 80% Oh, that's too much, and we're achieving much better response time than the objective, but other workloads are starving. Let's back that off and try again. It's not the process I object to - it's that we to often do this manually. Worse, we sometimes identify and adjust the wrong resource and fiddle with that to no useful result. Back in my days as a customer managing large systems, one of my users would call me up to beg for a "CPU boost": Me: "it won't make any difference - there's plenty of spare CPU to be had, and your application is completely I/O bound." User: "Please do it anyway." Me: "oh, all right, but it won't do you any good." (I did, because he was a friend, but it didn't help.) Prior art There are some operating environments that take a stab about workload management (rather than resource management) but I find them lacking. I know of one that uses synthetic "service units" composed of the sum of CPU, I/O and memory allocations multiplied by weighting factors. A workload is set to make a target rate of service units consumed per second. But this seems to be missing a key point: what is the relationship between artificial 'service units' and actually meeting a throughput or response time objective? What if I get plenty of one of the components (so am getting enough service units), but not enough of the resource whose needed to remove the bottleneck? Actual workload management That's not really the answer either. What is needed is to specify a workload's service levels in terms of externally visible metrics that are meaningful to a business, such as response times or transactions per second, and have the workload manager figure out which resources are not being adequately provided, and then adjust it as needed. If an application is not meeting its service level objectives and the reason is that it's not getting enough CPU cycles, adjust its CPU resource accordingly. If the reason is that the application isn't getting enough RAM to keep its working set in memory, then adjust its RAM assignment appropriately so it stops swapping. Simple idea, but that's a task we keep dumping on system administrators. In other words - don't hold the number of CPU shares constant and watch the achievement of service level vary. Instead, hold the service level constant, and dynamically adjust the number of CPU shares (or amount of other resources like RAM or I/O bandwidth) in order to meet the objective. Instrumenting non-instrumented applications There's one little problem here: how do I measure application performance in a way relating to a service level. I don't want to do it based on internal resources like number of CPU seconds it received per minute - We need to make resource decisions based on externally visible and meaningful measures of performance, not synthetic items or internal resource counters. If I have a way of marking the beginning and end of a transaction, I can then measure whether or not the application is meeting an objective based on it. If I can observe the delay factors for an application, I can see which resource shortages are slowing an application enough to keep it from meeting its objectives. I can then adjust resource allocations to relieve those shortages. Fortunately, Solaris provides facilities for both marking application progress and determining what factors cause application latency. The Solaris DTrace facility let's me introspect on application behavior: in particular I can see events like "receive a web hit" and "respond to that web hit" so I can get transaction rate and response time. DTrace (and tools like prstat) let me see where latency is being added to an application, so I know which resource to adjust. Summary After a delay of a mere few years, I am the proud creator of a patent (advice to anyone interested in going through the process: don't hold your breath!). The fundamental idea is fairly simple: instead of holding resource constant and suffering variable levels of success meeting service level objectives, properly characterise the service level objective in meaningful terms, instrument the application to see if it's meeting the objective, and then have a workload manager change resource allocations to remove delays preventing service level attainment. I've done it by hand for a long time - I think that's what a computer should do for me.

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• Powershell Run-As Script

  - by marc dekeyser

  Disclaimer: This script is not of my own making. I found it on a share somewhere and it is so handy I started using in a bunch of scripts. To the writer: If you're out there, somewhere, when you see this, thank you! Check if script is running as Adminstrator and if not use RunAs    # Use Check Switch to check if admin        param([Switch]$Check)        $IsAdmin = ([Security.Principal.WindowsPrincipal] [Security.Principal.WindowsIdentity]::GetCurrent()`        ).IsInRole([Security.Principal.WindowsBuiltInRole] "Administrator")            if ($Check) { return $IsAdmin }        if ($MyInvocation.ScriptName -ne "")    {         if (-not $IsAdmin)         {             try            {                 $arg = "-file `"$($MyInvocation.ScriptName)`""                Start-Process "$psHome\powershell.exe" -Verb Runas -ArgumentList $arg -ErrorAction 'stop'             }            catch            {                Write-Warning "Error - Failed to restart script with runas"                 break                          }            exit # Quit this session of powershell        }     }     else     {         Write-Warning "Error - Script must be saved as a .ps1 file first"         break     } write-host "Script Running As Administrator" -foregroundcolor redWrite-host ""

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• Improving exception handling ?

  - by n00b

  Hello, I am a newbie programmer and I recently started learning about exception handling in Java. I know what try, catch and finally blocks do, but I really need to understand how to use them well and where to handle something in the call stack... I have a project right now that involves I/O and all I'm doing is handling the exception in the lowest possible method in the call stack. I'm sure my exception handling can be improved, so I'm asking you guys how you think of exception handling? How did you guys get good at this and how can I better wrap my head around this idea?

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• Declarative Transactions in Node.js

  - by James Kingsbery

  Back in the day, it was common to manage database transactions in Java by writing code that did it. Something like this: Transaction tx = session.startTransaction(); ... try { tx.commit(); } catch (SomeException e){ tx.rollback(); } at the beginning and end of every method. This had some obvious problems - it's redundant, hides the intent of what's happening, etc. So, along came annotation-driven transactions: @Transaction public SomeResultObj getResult(...){ ... } Is there any support for declarative transaction management in node.js?

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• Database Insider Newsletter: February 2011 Edition Available

  - by jenny.gelhausen

  The February edition of the Database Insider Newsletter is now available. This edition covers the upcoming IOUG's Day of Real World Performance Tour What's coming for Collaborate 2011 How Oracle helps you steer clear of security pitfalls and much more... Enjoy! var gaJsHost = (("https:" == document.location.protocol) ? "https://ssl." : "http://www."); document.write(unescape("%3Cscript src='" + gaJsHost + "google-analytics.com/ga.js' type='text/javascript'%3E%3C/script%3E")); try { var pageTracker = _gat._getTracker("UA-13185312-1"); pageTracker._trackPageview(); } catch(err) {}

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• Crappy school, what to do? [closed]

  - by zhenka

  I started programming fairly late. I am 24 years old and about to graduate from a local public university with a really poorly designed curriculum and teachers. Most of the work felt like busy work, and no matter how much I try, it all feels like a waste. I know what a good curriculum looks like. I know what books I should read, but alas it's not so in my university. There is no way at this point that I can catch up to those graduating from places like MIT. My question and this is a serious one: what do I do? Do I just postpone learning the theory I would have learned until later and focus on software engineering skills? How important is the theory in terms of landing a job in New York? Any particular things I should focus on to land a software engineer job? I am very motivated and I just wish someone would give me the time and a chance.

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