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  • Configure mod_wsgi WSGIScriptAlias with mod_rewrite

    - by Lazik
    I want to redirect ex.com to www.ex.com but I still want www.ex.com/ to point to my app.wsgi without it showing up in the url. When I use the conf below and I go to ex.com, I get a 404 error saying can't find www.ex.com/app.wsgi/ If I change the WSGIScriptAlias / /var/www/vhosts/ex/app.wsgi to WSGIScriptAlias /app.wsgi /var/www/vhosts/ex/app.wsgi Then all my url look like www.ex.com/app.wsgi/blabla/... Is it possible to use some kind of rule to redirect ex.com to www.ex.com and still keeping / as the app.wsgi root? my conf file <VirtualHost *:80> ServerName www.ex.com ServerAlias ex.com *.ex.com RewriteEngine On RewriteCond %{HTTP_HOST} !^www\. RewriteRule ^(.*)$ http://www.%{HTTP_HOST}/$1 [R=301,L] WSGIDaemonProcess ex user=www-data group=www-data processes=1 threads=5 WSGIScriptAlias / /var/www/vhosts/ex/app.wsgi <Directory /var/www/vhosts/ex> WSGIProcessGroup ex WSGIApplicationGroup %{GLOBAL} Order deny,allow Allow from all </Directory> </VirtualHost>

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  • HP Pavilion: Sound problem after Windows Vista SP2 update

    - by Mehper C. Palavuzlar
    I have HP Pavilion dv-2051et notebook with Windows Vista Home Premium SP1. Recently the sound of my notebook completely went off and I poked up Windows sound settings and IDT HD Sound panel to bring it back, but to no avail (trust me, I looked at every setting). Then I made a system restore to the point located just before Vista SP2 was installed. The sounds came back. Afterwards, I installed Vista SP2 again, and the sounds went off again. SP2 installation causes complete loss of sounds of my notebook. What can I do to overcome this problem? I don't want to stay with SP1 but installing SP2 brings me a huge problem. Anyone experienced this lately? Any recommendations? Thanks in advance.

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  • CodePlex Daily Summary for Monday, June 10, 2013

    CodePlex Daily Summary for Monday, June 10, 2013Popular ReleasesNexusCamera: NexusCamera: Nexus Camera is a control for Windows Phone 7 & 8, which can be used as a menu on the Camera. The idea in making this control when we use a camera nexus. Thanks for Nexus. Need Windows Phone Toolkit https://phone.codeplex.com/ View Sample Camera http://tctechcrunch2011.files.wordpress.com/2012/11/nexus4-camera.jpgVR Player: VR Player 0.3 ALPHA: New plugin system with individual folders TrackIR support Maya and 3ds max formats support Dual screen support Mono layouts (left and right) Cylinder height parameter Barel effect factor parameter Razer hydra filter parameter VRPN bug fixes UI improvements Performances improvements Stabilization and logging with Log4Net New default values base on users feedback CTRL key to open menuZXMAK2: Version 2.7.5.4: - add hayes modem device (thanks to Eltaron) - add host joystick selection - fix joystick bits (swapped in previous version)SimCityPak: SimCityPak 0.1.0.8: SimCityPak 0.1.0.8 New features: Import BMP color palettes for vehicles Import RASTER file (uncompressed 8.8.8.8 DDS files) View different channels of RASTER files or preview of all layers combined Find text in javascripts TGA viewer Ground textures added to lot editor Many additional identified instances and propertiesWsus Package Publisher: Release v1.2.1306.09: Add more verifications on certificate validation. WPP will not let user to try publishing an update until the certificate is valid. Add certificate expiration date on the 'About' form. Filter Approbation to avoid a user to try to approve an update for uninstallation when the update do not support uninstallation. Add the server and console version on the 'About' form. WPP will not let user to publish an update until the server and console are not at the same level. WPP do not let user ...AJAX Control Toolkit: June 2013 Release: AJAX Control Toolkit Release Notes - June 2013 Release Version 7.0607June 2013 release of the AJAX Control Toolkit. AJAX Control Toolkit .NET 4.5 – AJAX Control Toolkit for .NET 4.5 and sample site (Recommended). AJAX Control Toolkit .NET 4 – AJAX Control Toolkit for .NET 4 and sample site (Recommended). AJAX Control Toolkit .NET 3.5 – AJAX Control Toolkit for .NET 3.5 and sample site (Recommended). Notes: - Instructions for using the AJAX Control Toolkit with ASP.NET 4.5 can be found at...Rawr: Rawr 5.2.1: This is the Downloadable WPF version of Rawr!For web-based version see http://elitistjerks.com/rawr.php You can find the version notes at: http://rawr.codeplex.com/wikipage?title=VersionNotes Rawr Addon (NOT UPDATED YET FOR MOP)We now have a Rawr Official Addon for in-game exporting and importing of character data hosted on Curse. The Addon does not perform calculations like Rawr, it simply shows your exported Rawr data in wow tooltips and lets you export your character to Rawr (including ba...VG-Ripper & PG-Ripper: PG-Ripper 1.4.13: changes NEW: Added Support for "ImageJumbo.com" links FIXED: Ripping of Threads with multiple pagesXomega Framework: Xomega.Framework 1.4: Adding support for Visual Studio 2012 and .Net framework 4.5. Minor bug fixes and enhancements.sb0t v.5: sb0t 5.14: Stability fix in script engine. Avatar.exists property fixed in scripting. cb0t custom font protocol re-added and updated to support new Ares.ASP.NET MVC Forum: MVCForum v1.3.5: This is a bug release version, with a couple of small usability features and UI changes. All the small amount of bugs reported in v1.3 have been fixed, no upgrade needed just overwrite the files and everything should just work.Json.NET: Json.NET 5.0 Release 6: New feature - Added serialized/deserialized JSON to verbose tracing New feature - Added support for using type name handling with ISerializable content Fix - Fixed not using default serializer settings with primitive values and JToken.ToObject Fix - Fixed error writing BigIntegers with JsonWriter.WriteToken Fix - Fixed serializing and deserializing flag enums with EnumMember attribute Fix - Fixed error deserializing interfaces with a valid type converter Fix - Fixed error deser...Christoc's DotNetNuke Module Development Template: DotNetNuke 7 Project Templates V2.3 for VS2012: V2.3 - Release Date 6/5/2013 Items addressed in this 2.3 release Fixed bad namespace for BusinessController in one of the C# templates. Updated documentation in all templates. Setting up your DotNetNuke Module Development Environment Installing Christoc's DotNetNuke Module Development Templates Customizing the latest DotNetNuke Module Development Project TemplatesPulse: Pulse 0.6.7.0: A number of small bug fixes to stabilize the previous Beta. Sorry about the never ending "New Version" bug!QlikView Extension - Animated Scatter Chart: Animated Scatter Chart - v1.0: Version 1.0 including Source Code qar File Example QlikView application Tested With: Browser Firefox 20 (x64) Google Chrome 27 (x64) Internet Explorer 9 QlikView QlikView Desktop 11 - SR2 (x64) QlikView Desktop 11.2 - SR1 (x64) QlikView Ajax Client 11.2 - SR2 (based on x64)BarbaTunnel: BarbaTunnel 7.2: Warning: HTTP Tunnel is not compatible with version 6.x and prior, HTTP packet format has been changed. Check Version History for more information about this release.SuperWebSocket, a .NET WebSocket Server: SuperWebSocket 0.8: This release includes these changes below: Upgrade SuperSocket to 1.5.3 which is much more stable Added handshake request validating api (WebSocketServer.ValidateHandshake(TWebSocketSession session, string origin)) Fixed a bug that the m_Filters in the SubCommandBase can be null if the command's method LoadSubCommandFilters(IEnumerable<SubCommandFilterAttribute> globalFilters) is not invoked Fixed the compatibility issue on Origin getting in the different version protocols Marked ISub...BlackJumboDog: Ver5.9.0: 2013.06.04 Ver5.9.0 (1) ?????????????????????????????????($Remote.ini Tmp.ini) (2) ThreadBaseTest?? (3) ????POP3??????SMTP???????????????? (4) Web???????、?????????URL??????????????? (5) Ftp???????、LIST?????????????? (6) ?????????????????????Media Companion: Media Companion MC3.569b: New* Movies - Autoscrape/Batch Rescrape extra fanart and or extra thumbs. * Movies - Alternative editor can add manually actors. * TV - Batch Rescraper, AutoScrape extrafanart, if option enabled. Fixed* Movies - Slow performance switching to movie tab by adding option 'Disable "Not Matching Rename Pattern"' to Movie Preferences - General. * Movies - Fixed only actors with images were scraped and added to nfo * Movies - Fixed filter reset if selected tab was above Home Movies. * Updated Medi...Nearforums - ASP.NET MVC forum engine: Nearforums v9.0: Version 9.0 of Nearforums with great new features for users and developers: SQL Azure support Admin UI for Forum Categories Avoid html validation for certain roles Improve profile picture moderation and support Warn, suspend, and ban users Web administration of site settings Extensions support Visit the Roadmap for more details. Webdeploy package sha1 checksum: 9.0.0.0: e687ee0438cd2b1df1d3e95ecb9d66e7c538293b New ProjectsASP.NET MVC 4 and RequireJS: ASP.NET MVC 4 application with Areas and RequireJSBaseX - Base converter and calculator: Dealing with numbers of any base in .NET.C# Exercises: C# ExercisesClassfinder: ClassfinderCreative OS ALPHA: This is a OS!!!!CSS Exercises: CSS ExercisesCustom Workflow Action: Project showing how to create and use Custom Workflow Action for SharePoint Designer 2013.Devshed Tools: Provides easy to use and compile-time-support solution for various type of projects on the .NET framework. Currently Devshed.Web is in development.Envar Editor: Edit environment variables easily on windowsExcel To Sql: A simplified tool for importing Excel data into SQL.HTML Exercises: HTML ExercisesKnockout.js with ASP.NET MVC: This project implements a system which maps .NET ViewModels to javascript ViewModels for use with knockout.js, using Razor markup syntax.LogoBids: LOGO??????,ORM??OpenAccess ORMManagistics: Management Logistics Application (including: Warehouse, Sale, Purchase, ...)Matrix Switch Preset Utility: A small utility for managing the inputs and outputs from a matrix switch via RS-232. Developed in WPF (VB9) and running on the .Net3.5SP1 framework.MvcSystemsCommander: An ASP.NET C# MVC4 webapp to help systems administrators consolidate common systems administration tasksNewspaperAgent: My small projectOutlook Recovery Software - Efficiently Repair Damaged PST File: This project tells you the easiest way to recover PST file of Outlook. Complete information has been given here to help users.Pattern: Testprocedure: a new procedural programming framework based on .net, by using lambda expression, it can handle async io friendly and provide a full lock-free solutionSharePoint 2013 custom field samples: SharePoint 2013 custom field samples is a research project aims to provide samples for developing custom fields in SharePoint 2013.SharePoint 2013 List Forms: This small framework allows you to manage custom list forms using rendering templates and controls stored in a SharePoint library.The Coconut Cranium Decision Engine: The Coconut Cranium Decision Engine is a boolean decision engine using the most mind-bendingly worse way of working.TxtToSeq: Command line utility to convert Commodore SEQ files to TXT files and vice-versa.ultgw: ult gw

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  • Globalization, Localization And Why My Application Stopped Launching

    - by Paulo Morgado
    When I was localizing a Windows Phone application I was developing, I set the argument on the constructor of the AssemblyCultureAttribute for the neutral culture (en-US in this particular case) for my application. As it was late at night (or early in the dawn ) I went to sleep and, on the next day, the application wasn’t launching although it compiled just fine. I’ll have to confess that it took me a couple of nights to figure out what I had done to my application. Have you figured out what I did wrong? The documentation for the AssemblyCultureAttribute states that: The attribute is used by compilers to distinguish between a main assembly and a satellite assembly. A main assembly contains code and the neutral culture's resources. A satellite assembly contains only resources for a particular culture, as in [assembly:AssemblyCultureAttribute("de")]. Putting this attribute on an assembly and using something other than the empty string ("") for the culture name will make this assembly look like a satellite assembly, rather than a main assembly that contains executable code. Labeling a traditional code library with this attribute will break it, because no other code will be able to find the library's entry points at runtime. So, what I did was marking the once main assembly as a satellite assembly for the en-US culture which made it impossible to find its entry point. To set the the neutral culture for the assembly resources I should haveused (and eventually did) the NeutralResourcesLanguageAttribute. According to its documentation: The NeutralResourcesLanguageAttribute attribute informs the ResourceManager of the application's default culture, and also informs the ResourceManager that the default culture's resources are found in the main application assembly. When looking up resources in the same culture as the default culture, the ResourceManager automatically uses the resources located in the main assembly instead of searching for a satellite assembly. This improves lookup performance for the first resource you load, and can reduce your working set.

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  • Are `break` and `continue` bad programming practices?

    - by Mikhail
    My boss keeps mentioning nonchalantly that bad programmers use break and continue in loops. I use them all the time because they make sense; let me show you the inspiration: function verify(object) { if (object->value < 0) return false; if (object->value > object->max_value) return false; if (object->name == "") return false; ... } The point here is that first the function checks that the conditions are correct, then executes the actual functionality. IMO same applies with loops: while (primary_condition) { if (loop_count > 1000) break; if (time_exect > 3600) break; if (this->data == "undefined") continue; if (this->skip == true) continue; ... } I think this makes it easier to read & debug; but I also don't see a downside. Please comment.

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  • Unable to run openoffice in headless mode

    - by uswaretech
    I want to automoate some PPT - PDF conversions, so I want to run openoffice in headless mode for scripting. On my machine with X running I can start opemoffice in headless mode via soffice -accept="socket,port=8100;urp;" -headless This doesn't seem to work on a server with X not running. $ soffice -accept="socket,port=8100;urp;" -headless /usr/lib/openoffice/program/soffice.bin X11 error: Can't open display: Set DISPLAY environment variable, use -display option or check permissions of your X-Server (See "man X" resp. "man xhost" for details) $ The error doesnt seem to make sense as well, as the point of specifying -headless was so that I do not need X, while this command seems to look for X.

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  • JMeter Stress testing

    - by mcondiff
    MAMP server hosting a Joomla instance. I'd like to hear the community's thoughts on the best way to stress test the server and find it's breaking point on concurrent users etc. Currently I have setup a test plan which I have going to the home page, grabbing the index.php, css, js and all images and have run tests on 1 to 100 users and a varying number of loops. What I'd like to know is how do I determine at what number of concurrent requests or looping requests is a good way to gauge if my server can handle the proposed increase in traffic? What is a good KB/sec, Throughput, Average, Max, Min via the Aggregate Report and at what number of threads/loops etc? I have googled and have not found immediate answers to these questions and thought to come here. More or less I have just used this http://jakarta.apache.org/jmeter/usermanual/jmeter_proxy_step_by_step.pdf to guide me and then I have been winging it in terms of Thread and Loop numbers. Any light shed on these subject would be much appreciated.

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  • Replacement mouse "feet"?

    - by Jeff Atwood
    The plastic skid pad "feet" on the bottom of my Logitech G9 mouse (which I love!) are getting rather worn down -- to the point that the outer shell of the mouse scrapes on the mousepad a bit. I've had the mouse for about ~2 years now so it does get a lot (I mean lot of use). But, I hate to buy a new mouse when I only need replacement "feet". Where can I obtain replacement mouse feet? Is this even possible?

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  • Practical mysql schema advice for eCommerce store - Products & Attributes

    - by Gravy
    I am currently planning my first eCommerce application (mySQL & Laravel Framework). I have various products, which all have different attributes. Describing products very simply, Some will have a manufacturer, some will not, some will have a diameter, others will have a width, height, depth and others will have a volume. Option 1: Create a master products table, and separate tables for specific product types (polymorphic relations). That way, I will not have any unnecessary null fields in the products table. Option 2: Create a products table, with all possible fields despite the fact that there will be a lot of null rows Option 3: Normalise so that each attribute type has it's own table. Option 4: Create an attributes table, as well as an attribute_values table with the value being varchar regardless of the actual data-type. The products table would have a many:many relationship with the attributes table. Option 5: Common attributes to all or most products put in the products table, and specific attributes to a particular category of product attached to the categories table. My thoughts are that I would like to be able to allow easy product filtering by these attributes and sorting. I would also want the frontend to be fast, less concern over the performance of the inserting and updating of product records. Im a bit overwhelmed with the vast implementation options, and cannot find a suitable answer in terms of the best method of approach. Could somebody point me in the right direction? In an ideal world, I would like to offer the following kind of functionality - http://www.glassesdirect.co.uk/products/ to my eCommerce store. As can be seen, in the sidebar, you can select an attribute the glasses to filter them. e.g. male / female or plastic / metal / titanium etc... Alternatively, should I just dump the mySql relational database idea and learn mongodb?

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  • Connecting to SQL database using SQLCMD

    - by kaleidoscope
    As we all know, there are a number of ways you can connect to your SQL Azure Database. One of the quick options is to try to connect to SQL server is SQLCMD. To start the SQLCMD utility and connect to a named instance of SQL Server Open a Command Prompt window, and type sqlcmd -S myServer\instanceName. Replace myServer\instanceName with the name of the computer and the instance of SQL Server that you want to connect to. Press ENTER. The sqlcmd prompt (1>) indicates that you are connected to the specified instance of SQL Server. SQL Management Studio offers the facility to use SQLCMD from within SQL scripts by using SQLCMD Mode. How to: Enable SQLCMD mode in the Transact-SQL Editor (About how to start the editor, see How to: Start the Transact-SQL Editor.) To toggle SQLCMD mode from the Data menu 1. Open the query in the Transact-SQL editor. 2. On the Data menu, point to Transact-SQL Editor, and click SQLCMD Mode. To toggle SQLCMD mode from the toolbar 1. Open the query in the Transact-SQL editor. 2. On the Transact-SQL Editor toolbar, click SQLCMD Mode. To toggle SQLCMD mode from the shortcut menu 1. Open the query in the Transact-SQL editor. 2. Right-click anywhere in the editor window, and then click SQLCMD Mode. For more information follow below link http://msdn.microsoft.com/en-us/library/ms170207.aspx   Geeta, G

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  • How does firefox chose which plugin to use?

    - by Brian Postow
    I have written a plugin which allows the user to view multi-page TIFF images within firefox. The problem is that Quicktime also thinks it can view TIFF images. How does Firefox chose which one gets used? through trial and error I've determined that: Sometimes, my plugin (Accel VIewTIFF) just runs, and everyone is happy. Sometimes I need to disable Quicktime in the Add-ons window. Sometimes I need to remove the QuickTime plugin files from the / Library/Internet Plug-ins folder (I'm on a mac) Sometimes I can put QuickTime BACK after having successfully run Accel ViewTIFF. I've yet to figure out when (if ever) each step is necessary. Please help me escape the cargo cult! (or at least point me to the right place in a manual.) thanks.

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  • APCUPSD and Hyper V R2

    - by Jason Berg
    I'm about to deploy a Windows Server 2008 R2 machine with the Hyper V role. I'd like to get away from having to use a network management card with my APC UPS as I'm only shutting down 1 server (it just seems like an unneeded point of failure). I'd like to look into using apcupsd instead. Will this work properly if I use a serial connection? Have you got it working yourself? How is the SNMP monitoring? I really like being able to easily monitor my UPS with SNMP when powerchute is installed. Will I be sacrificing this completely? Is the network management card really the way to go with this? If so, why? Bonus question: Is there a better UPS out there that I should be recommending in the future?

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  • Retro Video Game Collection

    - by Matt Christian
    Recently I've decided, in true nerd fashion, to collect either comic books or video games.  Considering I'm much more versed in the technological arts and not in ACTUAL art, I thought collecting old video games would be an interesting venture.  After all, I am a self-described compulsive shopper (my bank statement at the end of the month has a purchase every few days).  (Don't worry, I'm not in debt and still pay my bills on time!) I went to a local video game store in Stevens Point called Gaming Generations which is a neat little shop with loads of old games for great prices.  For example, any NES cartridge on the shelf (not behind glass) is, at most, $4.99 with the cheaper ones around $1.99.  During my first round at GG, I picked up the following: NES: - Fester's Quest - Adventures of Link (Zelda 2, grey cart) - Little Nemo - Total Recall - The Goonies 2 PSX: - Galerians N64: - Mission: Impossible - Hybrid Heaven I was a little cautious, would I even like collecting old games?  As soon as I popped a few of those games in I knew right away the answer was an astounding YES!  Not only is it fun to bring back memories of all these old games, but searching for them in stores is also a blast and saying 'I have that one, I need the second one.' After finding such joy in buying these games, I decided to go search through 4-5 stores in Wausau for old games as well.  While the prices were a bit higher and selection smaller, the search was still fun.  I found the following: NES: - Maniac Mansion - T&C Surf - Chip N Dale: Rescue Rangers - TMNT (the first one) - Mission: Impossible N64: - Turok - Turok 2 Genesis: - Sonic the Hedgehog Dreamcast: - Shenmue And I found a Gamegear for $5!  Now I just need to find games for it... Tonight I will go on one more small expedition into the used, once again stopping at GG and another second hand store to see if I can find any items for my collection.

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  • Oracle Social Network -The Social Glue for Enterprise Applications

    - by kellsey.ruppel
    by Peter Reiser  - Social Business Evangelist, Oracle WebCenter  Tom Petrocelli of Enterprise Strategy Group published a report recently, “Oracle Social Network: The Social Glue for Enterprise Applications”, on Oracle Social Network (OSN) and how traditional social products create social silos whereas OSN is the “social glue” for enterprise applications.  This report supports the point of Oracle’s Social Business Strategy to seamless integrate social capabilities into the main business processes. Quote from report: “Oracle has adopted the correct approach to creating a social layer and socially enabled applications. Oracle Social Network is not simply another enterprise social network product; it is a complete social layer for the enterprise application stack. This approach will serve Oracle users well in the future.” OSN allow to capture the related Conversations of a business process right where it’s happens – within the respective Business application.  Fusion CRM is an excellent example for this approach. Quote from report: “Oracle’s new software, Oracle Social Network, is an example of a solution to the silo problem. While Oracle fields a typical enterprise social network application with microblogging, file sharing, shared documents or wikis, and activity streams, the front-end application is only a small part of what Oracle Social Network does. Instead, Oracle Social Network is a platform that provides social features as a service to other enterprise applications. In effect, Oracle Social Network socially enables all of Oracle’s enterprise applications—all enterprise applications really—with not only the same features, but also the same conversations. As a result, the social conversations act as a conduit for inter-application communication and collaboration.” Source: ESG Research Report, Oracle Social Network: The Social Glue for Enterprise Applications, August 2012. You can download the report here.

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  • guvciew/youtube problem

    - by Anonymous
    I'm fairly new to Linux. Running on 12.10 Ubuntu. I've been running into some problems recording videos. Cheese crashes (as I've read from other users), YouTube will not allow me to select Allow (flash in Chrome and in Firefox). I managed to get 1 video uploaded from my cam and it worked about half the time, cut the audio off, lagged, etc. My computer is fine 4gigs, 32-bit i5 so it shouldn't be a problem. Now onto guv, I managed to get 1 video to work and after that every video I save it comes up with an orange file that looks like a film. I tried to change the file name, open in VLC, everything. I love Ubuntu and I'm never going back to Windows, ever One other thing to note is I am allowed to click "allowed" in Tiny chat. I even went to the adobe website to allow everything to bypass allow, deny option and nothing. Even went out of my way to add youtube/upload/cam for it to allow it and nothing. I realize right now Flash has been terrible for the past couple of months (especially in Chrome). What my question is well first and foremost, how do I fix this, if possible? I've thought about running Wine but I haven't heard anything good about it and I've already re reformated Ubuntu twice. Is there a codec pack I need too? Like I said everything works fine, especially in Chrome. It allows me to broadcast, no lag, and my mic works fine. guv would be my best option at this point because everything I've tried has given me nothing but trouble Thanks and I hope you guys can give me an answer. I've been at this for 2-3 days straight now. I could even go out of my way to not use Youtube and use something similar if it came down to it.

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  • Online remount btrfs of root filesystem with different subvolume (snapshot) [migrated]

    - by goncalopp
    Let's say you have a btrfs root filesystem on an online system. You want to revert the filesystem to an earlier state, of which you have a snapshot: remount /dev/sdaX / -o remount,subvol=snapshots/Y For the record, I've done this in a test system, and it does not work. The command returns with no errors, but the subvolume mounted is the same. If this did work, what would be the consequences? My guess is that open file descriptors would still point to the old subvolume, thus possibly leading to "data loss" on the new subvolume, if one was not careful. Assuming one goes to the trouble of closing and reopening all open file descriptors, does this sound feasible? Or are there other types of problems?

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  • Read-only file system

    - by John
    The title might not be as descriptive as I would like it to be but couldn't come up with a better one. My server's file system went into Read-only. And I don't understand why it does so and how to solve it. I can SSH into the server and when trying to start apache2 for example I get the following : username@srv1:~$ sudo service apache2 start [sudo] password for username: sudo: unable to open /var/lib/sudo/username/1: Read-only file system * Starting web server apache2 (30)Read-only file system: apache2: could not open error log file /var/log/apache2/error.log. Unable to open logs Action 'start' failed. The Apache error log may have more information. When I try restarting the server I get : username@srv1:~$ sudo shutdown -r now [sudo] password for username: sudo: unable to open /var/lib/sudo/username/1: Read-only file system Once I restart it manually it just start up without any warning or message saying something is wrong. I hope somebody could point me into the right direction to resolve this issue. Thanks in advance!

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  • Add game mechanics through equipment?

    - by Sidar
    In a game with different weapons and armor that actually affect more than just player stats, how would you achieve such effect? (These are just examples not concrete ideas ) For example we could have a handgun, uzi and then you have the graviton-gun. The first two would just shoot bullets, the third one does more than just shoot a simple projectile. It could allow the player to hold an enemy and drag it to use it as a meat shield. The player could also wear generic armor but at some point wears armor that can absorb projectiles. After absorbing enough projectiles you can shoot a giant blast. All these weapons/armor have different "behaviors" that either just raise stats or actually add new mechanics. In a simple case most guns would have similar properties and changing a few settings would create a new weapon (handgun shoots at an interval of x amount of seconds, lower this number and you have a machinegun). This obviously does not work if you intend to do more than just shoot projectiles. I'm pretty much stuck on writing the interface structure. While weapons and armor have different purposes they should both be able to process certain effects that change or add mechanics in the game world.

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  • Visual Studio 11 not 2011

    - by Daniel Moth
    A little pet peeve of mine is when people incorrectly refer to the Developer Preview (or the upcoming Beta) as Visual Studio 2011 instead of the correct Visual Studio 11. The "11" refers to the version number (internally we call it Dev11). What the product will be called when it is released is anyone's guess (it could keep the name or it could have a year appended to it, or it could be something else, who knows). Even if it does have a year appended to the name, I think it is a safe bet it won't be last year! For reference, version 10 was the previous version of Visual Studio which happened to be released in 2010, hence it got the name Visual Studio 2010. That is what confuses new people to this product I guess... they think that the two-digit number matches the year, just because it coincided like that last year. (btw, internally we called it Dev10). For further reference, older releases were: Visual Studio 2008 (v9) aka "Orcas", Visual Studio 2005 (v8) aka "Whidbey", Visual Studio .NET 2003 (v7.1) aka "Everett", and Visual Studio .NET 2002 (v7) aka "Rainier". Before that, we were in the pre-.NET era with Visual Studio 6 (where the version and the product name matched, without the year appended to the name). So next time you hear someone saying "Visual Studio 2011", point them to this post for some mini-education... thanks. Comments about this post by Daniel Moth welcome at the original blog.

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  • AWS RDS connection count

    - by wmarbut
    I am using AWS RDS with MySQL for a project and have a "large" instance. The documentation is clear on what this means as far as compute resources and RAM goes, but I can't find anything that documents how many open database connections that I can have. The app that I am using is PHP and it utilizes PDO with persistent connections. This means that the number of open connections could reach the maximum number of PHP child processes running at any given point. How do I ensure that my RDS instance has a max connections setting high enough to be comfortable with this?

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  • howto only tunnel specific hosts route through openvpn client on tomato

    - by kcome
    I am relatively newbie in networking world although I did coding and know some sysadmin background for a long time. and here I'm only one step from my destination. The whole picture is : at home I use one LinkSys E3000 as the gateway(don't know yet if this is it's name), wireless AP and no other routing/switching devices. It serves 1 PC and 1 Mac with LAN, 1 Mac Mini + 1 iPad + 2 smartphones with WIFI. My goal is use an openvpn client on the E3000 (with tomato firmware) and make my iPad and smartphone's all WiFi traffic through it, and other devices route remain the same non-openvpn route. So far I'm able to connect openvpn client on E3000 to an openvpn server, tunnel all my devices' all traffic through that openvpn connection. What's left is howto selectively route by source IP (at least in my guessing) to the tunnel while don't bother others. I had learned some 'iptables' and 'route' in past few days however without much luck, so here comes my question. Here are some info which will help you get the structure. ifconfig -a output, some useless lines striped, and in the web interface C0:C1:C0:1A:E0:28 is WAN, C0:C1:C0:1A:E0:27 is LAN, C0:C1:C0:1A:E0:29 is 2.4G wifi AP, C0:C1:C0:1A:E0:2A is 5G wifi AP. root@router:/tmp/home/root# ifconfig -a br0 Link encap:Ethernet HWaddr C0:C1:C0:1A:E0:27 inet addr:192.168.1.1 Bcast:192.168.1.255 Mask:255.255.255.0 UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 eth0 Link encap:Ethernet HWaddr C0:C1:C0:1A:E0:27 UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 eth1 Link encap:Ethernet HWaddr C0:C1:C0:1A:E0:29 UP BROADCAST RUNNING ALLMULTI MULTICAST MTU:1500 Metric:1 eth2 Link encap:Ethernet HWaddr C0:C1:C0:1A:E0:2A UP BROADCAST RUNNING ALLMULTI MULTICAST MTU:1500 Metric:1 lo Link encap:Local Loopback inet addr:127.0.0.1 Mask:255.0.0.0 inet6 addr: ::1/128 Scope:Host ppp0 Link encap:Point-to-Point Protocol inet addr:172.200.1.43 P-t-P:172.200.0.1 Mask:255.255.255.255 UP POINTOPOINT RUNNING MULTICAST MTU:1480 Metric:1 vlan1 Link encap:Ethernet HWaddr C0:C1:C0:1A:E0:27 UP BROADCAST RUNNING ALLMULTI MULTICAST MTU:1500 Metric:1 vlan2 Link encap:Ethernet HWaddr C0:C1:C0:1A:E0:28 UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 wl0.1 Link encap:Ethernet HWaddr C0:C1:C0:1A:E0:29 BROADCAST MULTICAST MTU:1500 Metric:1 brctl show output root@router:/tmp/home/root# brctl show bridge name bridge id STP enabled interfaces br0 8000.c0c1c01ae027 no vlan1 eth1 eth2 before openvpn route-up script root@router:/tmp/home/root# route -n Kernel IP routing table Destination Gateway Genmask Flags Metric Ref Use Iface 172.200.0.1 0.0.0.0 255.255.255.255 UH 0 0 0 ppp0 192.168.1.0 0.0.0.0 255.255.255.0 U 0 0 0 br0 127.0.0.0 0.0.0.0 255.0.0.0 U 0 0 0 lo 0.0.0.0 172.200.0.1 0.0.0.0 UG 0 0 0 ppp0 openvpn server push PUSH: Received control message: 'PUSH_REPLY,redirect-gateway,dhcp-option DNS 8.8.8.8,route 172.20.0.1,topology net30,ping 10,ping-restart 120,ifconfig 172.20.0.6 172.20.0.5' openvpn's stock route-up script Apr 24 14:52:06 router daemon.notice openvpn[1768]: /sbin/ifconfig tun11 172.20.0.6 pointopoint 172.20.0.5 mtu 1500 Apr 24 14:52:08 router daemon.notice openvpn[1768]: /sbin/route add -net 72.14.177.29 netmask 255.255.255.255 gw 172.200.0.1 Apr 24 14:52:08 router daemon.notice openvpn[1768]: /sbin/route add -net 0.0.0.0 netmask 128.0.0.0 gw 172.20.0.5 Apr 24 14:52:08 router daemon.notice openvpn[1768]: /sbin/route add -net 128.0.0.0 netmask 128.0.0.0 gw 172.20.0.5 Apr 24 14:52:08 router daemon.notice openvpn[1768]: /sbin/route add -net 172.20.0.1 netmask 255.255.255.255 gw 172.20.0.5 route after openvpn root@router:/tmp/home/root# route -n Kernel IP routing table Destination Gateway Genmask Flags Metric Ref Use Iface 172.20.0.5 0.0.0.0 255.255.255.255 UH 0 0 0 tun11 72.14.177.29 172.200.0.1 255.255.255.255 UGH 0 0 0 ppp0 172.200.0.1 0.0.0.0 255.255.255.255 UH 0 0 0 ppp0 172.20.0.1 172.20.0.5 255.255.255.255 UGH 0 0 0 tun11 192.168.1.0 0.0.0.0 255.255.255.0 U 0 0 0 br0 127.0.0.0 0.0.0.0 255.0.0.0 U 0 0 0 lo 0.0.0.0 172.20.0.5 128.0.0.0 UG 0 0 0 tun11 128.0.0.0 172.20.0.5 128.0.0.0 UG 0 0 0 tun11 0.0.0.0 172.200.0.1 0.0.0.0 UG 0 0 0 ppp0 something I had noticed and tried: * on the web interface of openvpn client there is an option "Create NAT on tunnel", if i check this, there is the following script (probably executed after openvpn connection established) root@router:/tmp/home/root# cat /tmp/etc/openvpn/fw/client1-fw.sh #!/bin/sh iptables -I INPUT -i tun11 -j ACCEPT iptables -I FORWARD -i tun11 -j ACCEPT iptables -t nat -I POSTROUTING -s 192.168.1.0/255.255.255.0 -o tun11 -j MASQUERADE if i uncheck this option, the last line will not appear. Then I guess probably the my issue will be solved by iptables and NAT related commands, I just haven't got enough knowledge to figure them out. I tried run iptables -t nat -I POSTROUTING -s 192.168.1.6 -o tun11 -j MASQUERADE manually after openvpn connected (192.168.1.6 is the ip address of my iPad), then my iPad get internet with openvpn tunnel, however all other devices can't reach internet. in case if needed, here is the iptables about NAT root@router:/tmp/home/root# iptables -t nat -L -n Chain PREROUTING (policy ACCEPT) target prot opt source destination DROP all -- 0.0.0.0/0 192.168.1.0/24 WANPREROUTING all -- 0.0.0.0/0 172.200.1.43 upnp all -- 0.0.0.0/0 172.200.1.43 Chain POSTROUTING (policy ACCEPT) target prot opt source destination MASQUERADE all -- 0.0.0.0/0 0.0.0.0/0 SNAT all -- 192.168.1.0/24 192.168.1.0/24 to:192.168.1.1 Chain OUTPUT (policy ACCEPT) target prot opt source destination Chain WANPREROUTING (1 references) target prot opt source destination DNAT icmp -- 0.0.0.0/0 0.0.0.0/0 to:192.168.1.1 Chain upnp (1 references) target prot opt source destination DNAT udp -- 0.0.0.0/0 0.0.0.0/0 udp dpt:5353 to:192.168.1.3:5353 Thanks in advance for helping and read this so much, I hope i made every info you need to give a help :)

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  • Running a simple integration scenario using the Oracle Big Data Connectors on Hadoop/HDFS cluster

    - by hamsun
    Between the elephant ( the tradional image of the Hadoop framework) and the Oracle Iron Man (Big Data..) an english setter could be seen as the link to the right data Data, Data, Data, we are living in a world where data technology based on popular applications , search engines, Webservers, rich sms messages, email clients, weather forecasts and so on, have a predominant role in our life. More and more technologies are used to analyze/track our behavior, try to detect patterns, to propose us "the best/right user experience" from the Google Ad services, to Telco companies or large consumer sites (like Amazon:) ). The more we use all these technologies, the more we generate data, and thus there is a need of huge data marts and specific hardware/software servers (as the Exadata servers) in order to treat/analyze/understand the trends and offer new services to the users. Some of these "data feeds" are raw, unstructured data, and cannot be processed effectively by normal SQL queries. Large scale distributed processing was an emerging infrastructure need and the solution seemed to be the "collocation of compute nodes with the data", which in turn leaded to MapReduce parallel patterns and the development of the Hadoop framework, which is based on MapReduce and a distributed file system (HDFS) that runs on larger clusters of rather inexpensive servers. Several Oracle products are using the distributed / aggregation pattern for data calculation ( Coherence, NoSql, times ten ) so once that you are familiar with one of these technologies, lets says with coherence aggregators, you will find the whole Hadoop, MapReduce concept very similar. Oracle Big Data Appliance is based on the Cloudera Distribution (CDH), and the Oracle Big Data Connectors can be plugged on a Hadoop cluster running the CDH distribution or equivalent Hadoop clusters. In this paper, a "lab like" implementation of this concept is done on a single Linux X64 server, running an Oracle Database 11g Enterprise Edition Release 11.2.0.4.0, and a single node Apache hadoop-1.2.1 HDFS cluster, using the SQL connector for HDFS. The whole setup is fairly simple: Install on a Linux x64 server ( or virtual box appliance) an Oracle Database 11g Enterprise Edition Release 11.2.0.4.0 server Get the Apache Hadoop distribution from: http://mir2.ovh.net/ftp.apache.org/dist/hadoop/common/hadoop-1.2.1. Get the Oracle Big Data Connectors from: http://www.oracle.com/technetwork/bdc/big-data-connectors/downloads/index.html?ssSourceSiteId=ocomen. Check the java version of your Linux server with the command: java -version java version "1.7.0_40" Java(TM) SE Runtime Environment (build 1.7.0_40-b43) Java HotSpot(TM) 64-Bit Server VM (build 24.0-b56, mixed mode) Decompress the hadoop hadoop-1.2.1.tar.gz file to /u01/hadoop-1.2.1 Modify your .bash_profile export HADOOP_HOME=/u01/hadoop-1.2.1 export PATH=$PATH:$HADOOP_HOME/bin export HIVE_HOME=/u01/hive-0.11.0 export PATH=$PATH:$HADOOP_HOME/bin:$HIVE_HOME/bin (also see my sample .bash_profile) Set up ssh trust for Hadoop process, this is a mandatory step, in our case we have to establish a "local trust" as will are using a single node configuration copy the new public keys to the list of authorized keys connect and test the ssh setup to your localhost: We will run a "pseudo-Hadoop cluster", in what is called "local standalone mode", all the Hadoop java components are running in one Java process, this is enough for our demo purposes. We need to "fine tune" some Hadoop configuration files, we have to go at our $HADOOP_HOME/conf, and modify the files: core-site.xml hdfs-site.xml mapred-site.xml check that the hadoop binaries are referenced correctly from the command line by executing: hadoop -version As Hadoop is managing our "clustered HDFS" file system we have to create "the mount point" and format it , the mount point will be declared to core-site.xml as: The layout under the /u01/hadoop-1.2.1/data will be created and used by other hadoop components (MapReduce = /mapred/...) HDFS is using the /dfs/... layout structure format the HDFS hadoop file system: Start the java components for the HDFS system As an additional check, you can use the GUI Hadoop browsers to check the content of your HDFS configurations: Once our HDFS Hadoop setup is done you can use the HDFS file system to store data ( big data : )), and plug them back and forth to Oracle Databases by the means of the Big Data Connectors ( which is the next configuration step). You can create / use a Hive db, but in our case we will make a simple integration of "raw data" , through the creation of an External Table to a local Oracle instance ( on the same Linux box, we run the Hadoop HDFS one node cluster and one Oracle DB). Download some public "big data", I use the site: http://france.meteofrance.com/france/observations, from where I can get *.csv files for my big data simulations :). Here is the data layout of my example file: Download the Big Data Connector from the OTN (oraosch-2.2.0.zip), unzip it to your local file system (see picture below) Modify your environment in order to access the connector libraries , and make the following test: [oracle@dg1 bin]$./hdfs_stream Usage: hdfs_stream locationFile [oracle@dg1 bin]$ Load the data to the Hadoop hdfs file system: hadoop fs -mkdir bgtest_data hadoop fs -put obsFrance.txt bgtest_data/obsFrance.txt hadoop fs -ls /user/oracle/bgtest_data/obsFrance.txt [oracle@dg1 bg-data-raw]$ hadoop fs -ls /user/oracle/bgtest_data/obsFrance.txt Found 1 items -rw-r--r-- 1 oracle supergroup 54103 2013-10-22 06:10 /user/oracle/bgtest_data/obsFrance.txt [oracle@dg1 bg-data-raw]$hadoop fs -ls hdfs:///user/oracle/bgtest_data/obsFrance.txt Found 1 items -rw-r--r-- 1 oracle supergroup 54103 2013-10-22 06:10 /user/oracle/bgtest_data/obsFrance.txt Check the content of the HDFS with the browser UI: Start the Oracle database, and run the following script in order to create the Oracle database user, the Oracle directories for the Oracle Big Data Connector (dg1 it’s my own db id replace accordingly yours): #!/bin/bash export ORAENV_ASK=NO export ORACLE_SID=dg1 . oraenv sqlplus /nolog <<EOF CONNECT / AS sysdba; CREATE OR REPLACE DIRECTORY osch_bin_path AS '/u01/orahdfs-2.2.0/bin'; CREATE USER BGUSER IDENTIFIED BY oracle; GRANT CREATE SESSION, CREATE TABLE TO BGUSER; GRANT EXECUTE ON sys.utl_file TO BGUSER; GRANT READ, EXECUTE ON DIRECTORY osch_bin_path TO BGUSER; CREATE OR REPLACE DIRECTORY BGT_LOG_DIR as '/u01/BG_TEST/logs'; GRANT READ, WRITE ON DIRECTORY BGT_LOG_DIR to BGUSER; CREATE OR REPLACE DIRECTORY BGT_DATA_DIR as '/u01/BG_TEST/data'; GRANT READ, WRITE ON DIRECTORY BGT_DATA_DIR to BGUSER; EOF Put the following in a file named t3.sh and make it executable, hadoop jar $OSCH_HOME/jlib/orahdfs.jar \ oracle.hadoop.exttab.ExternalTable \ -D oracle.hadoop.exttab.tableName=BGTEST_DP_XTAB \ -D oracle.hadoop.exttab.defaultDirectory=BGT_DATA_DIR \ -D oracle.hadoop.exttab.dataPaths="hdfs:///user/oracle/bgtest_data/obsFrance.txt" \ -D oracle.hadoop.exttab.columnCount=7 \ -D oracle.hadoop.connection.url=jdbc:oracle:thin:@//localhost:1521/dg1 \ -D oracle.hadoop.connection.user=BGUSER \ -D oracle.hadoop.exttab.printStackTrace=true \ -createTable --noexecute then test the creation fo the external table with it: [oracle@dg1 samples]$ ./t3.sh ./t3.sh: line 2: /u01/orahdfs-2.2.0: Is a directory Oracle SQL Connector for HDFS Release 2.2.0 - Production Copyright (c) 2011, 2013, Oracle and/or its affiliates. All rights reserved. Enter Database Password:] The create table command was not executed. The following table would be created. CREATE TABLE "BGUSER"."BGTEST_DP_XTAB" ( "C1" VARCHAR2(4000), "C2" VARCHAR2(4000), "C3" VARCHAR2(4000), "C4" VARCHAR2(4000), "C5" VARCHAR2(4000), "C6" VARCHAR2(4000), "C7" VARCHAR2(4000) ) ORGANIZATION EXTERNAL ( TYPE ORACLE_LOADER DEFAULT DIRECTORY "BGT_DATA_DIR" ACCESS PARAMETERS ( RECORDS DELIMITED BY 0X'0A' CHARACTERSET AL32UTF8 STRING SIZES ARE IN CHARACTERS PREPROCESSOR "OSCH_BIN_PATH":'hdfs_stream' FIELDS TERMINATED BY 0X'2C' MISSING FIELD VALUES ARE NULL ( "C1" CHAR(4000), "C2" CHAR(4000), "C3" CHAR(4000), "C4" CHAR(4000), "C5" CHAR(4000), "C6" CHAR(4000), "C7" CHAR(4000) ) ) LOCATION ( 'osch-20131022081035-74-1' ) ) PARALLEL REJECT LIMIT UNLIMITED; The following location files would be created. osch-20131022081035-74-1 contains 1 URI, 54103 bytes 54103 hdfs://localhost:19000/user/oracle/bgtest_data/obsFrance.txt Then remove the --noexecute flag and create the external Oracle table for the Hadoop data. Check the results: The create table command succeeded. CREATE TABLE "BGUSER"."BGTEST_DP_XTAB" ( "C1" VARCHAR2(4000), "C2" VARCHAR2(4000), "C3" VARCHAR2(4000), "C4" VARCHAR2(4000), "C5" VARCHAR2(4000), "C6" VARCHAR2(4000), "C7" VARCHAR2(4000) ) ORGANIZATION EXTERNAL ( TYPE ORACLE_LOADER DEFAULT DIRECTORY "BGT_DATA_DIR" ACCESS PARAMETERS ( RECORDS DELIMITED BY 0X'0A' CHARACTERSET AL32UTF8 STRING SIZES ARE IN CHARACTERS PREPROCESSOR "OSCH_BIN_PATH":'hdfs_stream' FIELDS TERMINATED BY 0X'2C' MISSING FIELD VALUES ARE NULL ( "C1" CHAR(4000), "C2" CHAR(4000), "C3" CHAR(4000), "C4" CHAR(4000), "C5" CHAR(4000), "C6" CHAR(4000), "C7" CHAR(4000) ) ) LOCATION ( 'osch-20131022081719-3239-1' ) ) PARALLEL REJECT LIMIT UNLIMITED; The following location files were created. osch-20131022081719-3239-1 contains 1 URI, 54103 bytes 54103 hdfs://localhost:19000/user/oracle/bgtest_data/obsFrance.txt This is the view from the SQL Developer: and finally the number of lines in the oracle table, imported from our Hadoop HDFS cluster SQL select count(*) from "BGUSER"."BGTEST_DP_XTAB"; COUNT(*) ---------- 1151 In a next post we will integrate data from a Hive database, and try some ODI integrations with the ODI Big Data connector. Our simplistic approach is just a step to show you how these unstructured data world can be integrated to Oracle infrastructure. Hadoop, BigData, NoSql are great technologies, they are widely used and Oracle is offering a large integration infrastructure based on these services. Oracle University presents a complete curriculum on all the Oracle related technologies: NoSQL: Introduction to Oracle NoSQL Database Using Oracle NoSQL Database Big Data: Introduction to Big Data Oracle Big Data Essentials Oracle Big Data Overview Oracle Data Integrator: Oracle Data Integrator 12c: New Features Oracle Data Integrator 11g: Integration and Administration Oracle Data Integrator: Administration and Development Oracle Data Integrator 11g: Advanced Integration and Development Oracle Coherence 12c: Oracle Coherence 12c: New Features Oracle Coherence 12c: Share and Manage Data in Clusters Oracle Coherence 12c: Oracle GoldenGate 11g: Fundamentals for Oracle Oracle GoldenGate 11g: Fundamentals for SQL Server Oracle GoldenGate 11g Fundamentals for Oracle Oracle GoldenGate 11g Fundamentals for DB2 Oracle GoldenGate 11g Fundamentals for Teradata Oracle GoldenGate 11g Fundamentals for HP NonStop Oracle GoldenGate 11g Management Pack: Overview Oracle GoldenGate 11g Troubleshooting and Tuning Oracle GoldenGate 11g: Advanced Configuration for Oracle Other Resources: Apache Hadoop : http://hadoop.apache.org/ is the homepage for these technologies. "Hadoop Definitive Guide 3rdEdition" by Tom White is a classical lecture for people who want to know more about Hadoop , and some active "googling " will also give you some more references. About the author: Eugene Simos is based in France and joined Oracle through the BEA-Weblogic Acquisition, where he worked for the Professional Service, Support, end Education for major accounts across the EMEA Region. He worked in the banking sector, ATT, Telco companies giving him extensive experience on production environments. Eugen currently specializes in Oracle Fusion Middleware teaching an array of courses on Weblogic/Webcenter, Content,BPM /SOA/Identity-Security/GoldenGate/Virtualisation/Unified Comm Suite) throughout the EMEA region.

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  • Inside the Concurrent Collections: ConcurrentBag

    - by Simon Cooper
    Unlike the other concurrent collections, ConcurrentBag does not really have a non-concurrent analogy. As stated in the MSDN documentation, ConcurrentBag is optimised for the situation where the same thread is both producing and consuming items from the collection. We'll see how this is the case as we take a closer look. Again, I recommend you have ConcurrentBag open in a decompiler for reference. Thread Statics ConcurrentBag makes heavy use of thread statics - static variables marked with ThreadStaticAttribute. This is a special attribute that instructs the CLR to scope any values assigned to or read from the variable to the executing thread, not globally within the AppDomain. This means that if two different threads assign two different values to the same thread static variable, one value will not overwrite the other, and each thread will see the value they assigned to the variable, separately to any other thread. This is a very useful function that allows for ConcurrentBag's concurrency properties. You can think of a thread static variable: [ThreadStatic] private static int m_Value; as doing the same as: private static Dictionary<Thread, int> m_Values; where the executing thread's identity is used to automatically set and retrieve the corresponding value in the dictionary. In .NET 4, this usage of ThreadStaticAttribute is encapsulated in the ThreadLocal class. Lists of lists ConcurrentBag, at its core, operates as a linked list of linked lists: Each outer list node is an instance of ThreadLocalList, and each inner list node is an instance of Node. Each outer ThreadLocalList is owned by a particular thread, accessible through the thread local m_locals variable: private ThreadLocal<ThreadLocalList<T>> m_locals It is important to note that, although the m_locals variable is thread-local, that only applies to accesses through that variable. The objects referenced by the thread (each instance of the ThreadLocalList object) are normal heap objects that are not specific to any thread. Thinking back to the Dictionary analogy above, if each value stored in the dictionary could be accessed by other means, then any thread could access the value belonging to other threads using that mechanism. Only reads and writes to the variable defined as thread-local are re-routed by the CLR according to the executing thread's identity. So, although m_locals is defined as thread-local, the m_headList, m_nextList and m_tailList variables aren't. This means that any thread can access all the thread local lists in the collection by doing a linear search through the outer linked list defined by these variables. Adding items So, onto the collection operations. First, adding items. This one's pretty simple. If the current thread doesn't already own an instance of ThreadLocalList, then one is created (or, if there are lists owned by threads that have stopped, it takes control of one of those). Then the item is added to the head of that thread's list. That's it. Don't worry, it'll get more complicated when we account for the other operations on the list! Taking & Peeking items This is where it gets tricky. If the current thread's list has items in it, then it peeks or removes the head item (not the tail item) from the local list and returns that. However, if the local list is empty, it has to go and steal another item from another list, belonging to a different thread. It iterates through all the thread local lists in the collection using the m_headList and m_nextList variables until it finds one that has items in it, and it steals one item from that list. Up to this point, the two threads had been operating completely independently. To steal an item from another thread's list, the stealing thread has to do it in such a way as to not step on the owning thread's toes. Recall how adding and removing items both operate on the head of the thread's linked list? That gives us an easy way out - a thread trying to steal items from another thread can pop in round the back of another thread's list using the m_tail variable, and steal an item from the back without the owning thread knowing anything about it. The owning thread can carry on completely independently, unaware that one of its items has been nicked. However, this only works when there are at least 3 items in the list, as that guarantees there will be at least one node between the owning thread performing operations on the list head and the thread stealing items from the tail - there's no chance of the two threads operating on the same node at the same time and causing a race condition. If there's less than three items in the list, then there does need to be some synchronization between the two threads. In this case, the lock on the ThreadLocalList object is used to mediate access to a thread's list when there's the possibility of contention. Thread synchronization In ConcurrentBag, this is done using several mechanisms: Operations performed by the owner thread only take out the lock when there are less than three items in the collection. With three or greater items, there won't be any conflict with a stealing thread operating on the tail of the list. If a lock isn't taken out, the owning thread sets the list's m_currentOp variable to a non-zero value for the duration of the operation. This indicates to all other threads that there is a non-locked operation currently occuring on that list. The stealing thread always takes out the lock, to prevent two threads trying to steal from the same list at the same time. After taking out the lock, the stealing thread spinwaits until m_currentOp has been set to zero before actually performing the steal. This ensures there won't be a conflict with the owning thread when the number of items in the list is on the 2-3 item borderline. If any add or remove operations are started in the meantime, and the list is below 3 items, those operations try to take out the list's lock and are blocked until the stealing thread has finished. This allows a thread to steal an item from another thread's list without corrupting it. What about synchronization in the collection as a whole? Collection synchronization Any thread that operates on the collection's global structure (accessing anything outside the thread local lists) has to take out the collection's global lock - m_globalListsLock. This single lock is sufficient when adding a new thread local list, as the items inside each thread's list are unaffected. However, what about operations (such as Count or ToArray) that need to access every item in the collection? In order to ensure a consistent view, all operations on the collection are stopped while the count or ToArray is performed. This is done by freezing the bag at the start, performing the global operation, and unfreezing at the end: The global lock is taken out, to prevent structural alterations to the collection. m_needSync is set to true. This notifies all the threads that they need to take out their list's lock irregardless of what operation they're doing. All the list locks are taken out in order. This blocks all locking operations on the lists. The freezing thread waits for all current lockless operations to finish by spinwaiting on each m_currentOp field. The global operation can then be performed while the bag is frozen, but no other operations can take place at the same time, as all other threads are blocked on a list's lock. Then, once the global operation has finished, the locks are released, m_needSync is unset, and normal concurrent operation resumes. Concurrent principles That's the essence of how ConcurrentBag operates. Each thread operates independently on its own local list, except when they have to steal items from another list. When stealing, only the stealing thread is forced to take out the lock; the owning thread only has to when there is the possibility of contention. And a global lock controls accesses to the structure of the collection outside the thread lists. Operations affecting the entire collection take out all locks in the collection to freeze the contents at a single point in time. So, what principles can we extract here? Threads operate independently Thread-static variables and ThreadLocal makes this easy. Threads operate entirely concurrently on their own structures; only when they need to grab data from another thread is there any thread contention. Minimised lock-taking Even when two threads need to operate on the same data structures (one thread stealing from another), they do so in such a way such that the probability of actually blocking on a lock is minimised; the owning thread always operates on the head of the list, and the stealing thread always operates on the tail. Management of lockless operations Any operations that don't take out a lock still have a 'hook' to force them to lock when necessary. This allows all operations on the collection to be stopped temporarily while a global snapshot is taken. Hopefully, such operations will be short-lived and infrequent. That's all the concurrent collections covered. I hope you've found it as informative and interesting as I have. Next, I'll be taking a closer look at ThreadLocal, which I came across while analyzing ConcurrentBag. As you'll see, the operation of this class deserves a much closer look.

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  • Easy Credential Caching for Git

    A common question since launching our Git support is whether there is a way to cache your username and password so you don’t have to enter it on every push.  Well thanks to Andrew Nurse from the ASP.Net team, there is now a great solution for this! Credential Caching in Windows to the Rescue Using the Git extension point for credential caching, Andrew created an integration into the Windows Credentials store. After installing git-credential-winstore instead of getting that standard prompt for a username/password, you will get a Windows Security prompt. From here your credentials for CodePlex will be stored securely within the Windows Credential Store. Setup The setup is pretty easy. Download the application from Andrew's git-credential-winstore project. Launch the executable and select yes to have it prompt for credentials. That's it. Make sure you are running the latest version of msysgit, since the credential's API is fairly new. Thanks to Andrew for sharing his work.  If you have suggestions or improvements you can fork the code here.

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  • Friend of Red Gate

    - by Nick Harrison
    Friend of Red Gate I recently joined the friend of Red Gate program.   I am very honored to be included in this group.    This program is a big part of Red Gates community outreach.   If you are not familiar with Red Gate, I urge you to check them out.    They have some wonderful tools for the SQL Server community and the DotNet community.    They are also building up some tools for Exchange and Oracle. I was invited to join this program primarliy because of my work with Simple Talk and promoting one of their newest products, Reflector. Reflector is a wonderful tool.   I doubt that anyone who has ever used it would argue that point. Red Gate did a wonderful job taking over the support of Reflector.   I know many people had their doubts.    The initial release under Red Gate should set those fears to rest.   I was very impressed with how their developers interacted with their users during the preview phase! Red Gate is also a good partner for the community.    They activly support the community, sponsoring Code Camps, sponsoring User Groups, supporting the Forums, etc. And their tools are pretty amazing as well.

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