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• How to generate Visa checkout token? [on hold]

  - by Muhammad Junaid

  I am on process of creating a Visa checkout plugin but stuck in generating token Here are the token requirment: Format: Alphanumeric; maximum 100 characters in the form of token: x:UNIX_UTC_Timestamp:SHA256_hash, where UNIX_UTC_Timestamp is a UNIX Epoch timestamp SHA256_hash is an SHA256 hash of the following unseparated items: Your shared secret Timestamp from the transaction; exactly the same as UNIX_UTC_Timestamp Resource path (API name). This HTTPS request's query string Note: The query string includes one or more parameters in name-value pair format, whose names are separated from values by equal signs (=); an empty value may be omitted but the name and equal sign must be present. The initial question mark (?) is not included. Note: All parameters must be present. The parameters must be in lexicographic sort order (UTF-8, uppercase hex characters) with parameters separated from each other by an ampersand (&). Note: The query string must be URL encoded (excepting the following characters, per RFC 3986: hyp You can find on Google "visa checkout developer updating 1 px image"

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• How to change the state of a singleton in runtime

  - by user34401

  Consider I am going to write a simple file based logger AppLogger to be used in my apps, ideally it should be a singleton so I can call it via public class AppLogger { public static String file = ".."; public void logToFile() { // Write to file } public static log(String s) { AppLogger.getInstance().logToFile(s); } } And to use it AppLogger::log("This is a log statement"); The problem is, what is the best time I should provide the value of file since it is a just a singleton? Or how to refactor the above code (or skip using singleton) so I can customize the log file path? (Assume I don't need to write to multiple at the same time) p.s. I know I can use library e.g. log4j, but consider it is just a design question, how to refactor the code above?

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• apt-get not recognizing downloaded archives

  - by meteors

  I installed Ubuntu Gnome 13.10. I previously had Ubuntu Gnome 13.04 and had all the archives in the /var/cache/apt/archives/ stored to a removable disk. After installing 13.10 I copied all my archives to the above mentioned path. When I run apt-get install it tries to fetch the archives although I have the archives. Also if instead of apt-get install if I try to install individual .deb files using dpkg -i everything runs fine. These are the permissions of files: How do I fix this. Previously copying archives like this worked fine and downloading duplicates the files.

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• Steps to rebuild gspca_kinect driver module?

  - by Bobby Ray

  I recently purchased a Kinect for Windows and quickly discovered that the camera drivers included in linux kernel 3.0+ aren't compatible with the Kinect for Windows hardware revision. After looking at the source code it seems like a tiny modification is all that is required for compatibility, so I've been trying to recompile the driver - to no avail. I've been referring to this article and this one as well, though they are a bit outdated. When I try to compile the module, I get an error because the header file "gspca.h" can't be found in the include path. I located the missing header in my filesystem, but the file itself is empty. I've also tried downloading the kernel source (3.2.0-24-generic), which allowed me to compile the module, but when I load the module I get an error. -1 Unknown symbol in module Is there a standard way to go about this without first building the kernel? Will building the kernel ensure that I can build the module? Thanks

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• boot loading problem after wubi installation of Ubuntu 12.04 on Win7

  - by user63085

  I was new in Ubuntu OS and I was just trying to use wubi windows installer to get a Ubuntu first for hands-on. I followed exactly the same as the instructions and after reboot win7, there is no Ubuntu selection in windows boot manager, with only Windows 7 showing there evilly -.- What I've found out was that the grub folder inside Ubuntu folder ( in my C:\ drive) was empty, either inside the ubuntu\disks\grub or ubuntu\install\grub. I thought this might be the reason why I could not load ubuntu during startup. Cause I've also looked into the EasyBCD settings, and ubuntu entry with Bootloader Path: \ubuntu\winboot\wubildr.mbr was lying there peacefully, looking perfectly fine. However it was not in boot loader actually. Is there a way to restore the grub folder with grub2, or is there any way to fix this problem so that I can find the "Ubuntu" selection at windows startup? Very appreciate your help :) Henry

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• Throttling Cache Events

  - by dxfelcey

  The real-time eventing feature in Coherence is great for relaying state changes to other systems or to users. However, sometimes not all changes need to or can be sent to consumers. For instance; If rapid changes cannot be consumed or interpreted as fast as they are being sent. A user looking at changing Stock prices may only be able to interpret and react to 1 change per second. A client may be using low bandwidth connection, so rapidly sending events will only result in them being queued and delayed A large number of clients may need to be notified of state changes and sending 100 events p/s to 1000 clients cannot be supported with the available hardware, but 10 events p/s to 1000 clients can. Note this example assumes that many of the state changes are to the same value. One simple approach to throttling Coherence cache events is to use a cache store to capture changes to one cache (data cache) and insert those changes periodically in another cache (events cache). Consumers interested in state changes to entires in the first cache register an interest (event listener) against the second event cache. By using the cache store write-behind feature rapid updates to the same cache entry are coalesced so that updates are merged and written at the interval configured to the event cache. The time interval at which changes are written to the events cache can easily be configured using the write-behind delay time in the cache configuration, as shown below.   <caching-schemes>     <distributed-scheme>       <scheme-name>CustomDistributedCacheScheme</scheme-name>       <service-name>CustomDistributedCacheService</service-name>       <thread-count>1</thread-count>       <backing-map-scheme>         <read-write-backing-map-scheme>           <scheme-name>CustomRWBackingMapScheme</scheme-name>           <internal-cache-scheme>             <local-scheme />           </internal-cache-scheme>           <cachestore-scheme>             <class-scheme>               <scheme-name>CustomCacheStoreScheme</scheme-name>               <class-name>com.oracle.coherence.test.CustomCacheStore</class-name>               <init-params>                 <init-param>                   <param-type>java.lang.String</param-type>                   <param-value>{cache-name}</param-value>                 </init-param>                 <init-param>                   <param-type>java.lang.String</param-type>                   <!-- The name of the cache to write events to -->                   <param-value>cqc-test</param-value>                 </init-param>               </init-params>             </class-scheme>           </cachestore-scheme>           <write-delay>1s</write-delay>           <write-batch-factor>0</write-batch-factor>         </read-write-backing-map-scheme>       </backing-map-scheme>       <autostart>true</autostart>     </distributed-scheme>   </caching-schemes> The cache store implementation to perform this throttling is trivial and only involves overriding the basic cache store functions. public class CustomCacheStore implements CacheStore { private String publishingCacheName; private String sourceCacheName; public CustomCacheStore(String sourceCacheStore, String publishingCacheName) { this.publishingCacheName = publishingCacheName; this.sourceCacheName = sourceCacheName; } @Override public Object load(Object key) { return null; } @Override public Map loadAll(Collection keyCollection) { return null; } @Override public void erase(Object key) { if (sourceCacheName != publishingCacheName) { CacheFactory.getCache(publishingCacheName).remove(key); CacheFactory.log("Erasing entry: " + key, CacheFactory.LOG_DEBUG); } } @Override public void eraseAll(Collection keyCollection) { if (sourceCacheName != publishingCacheName) { for (Object key : keyCollection) { CacheFactory.getCache(publishingCacheName).remove(key); CacheFactory.log("Erasing collection entry: " + key, CacheFactory.LOG_DEBUG); } } } @Override public void store(Object key, Object value) { if (sourceCacheName != publishingCacheName) { CacheFactory.getCache(publishingCacheName).put(key, value); CacheFactory.log("Storing entry (key=value): " + key + "=" + value, CacheFactory.LOG_DEBUG); } } @Override public void storeAll(Map entryMap) { if (sourceCacheName != publishingCacheName) { CacheFactory.getCache(publishingCacheName).putAll(entryMap); CacheFactory.log("Storing entries: " + entryMap, CacheFactory.LOG_DEBUG); } } }  As you can see each cache store operation on the data cache results in a similar operation on event cache. This is a very simple pattern which has a lot of additional possibilities, but it also has a few drawbacks you should be aware of: This event throttling implementation will use additional memory as a duplicate copy of entries held in the data cache need to be held in the events cache too - 2 if the event cache has backups A data cache may already use a cache store, so a "multiplexing cache store pattern" must also be used to send changes to the existing and throttling cache store.  If you would like to try out this throttling example you can download it here. I hope its useful and let me know if you spot any further optimizations.

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• How to make a launcher that will first navigate to a folder and then execute a command that resides in normal /usr/bin/

  - by Nirmik

  Okay this Question is basically directed for using GRIVE the linux client for Google Drive Details on how to do it are Here. The thing is that,evrytime i want the folder to sync,I have to navigate to the google drive folder and then execute the grive commnd. I want to make it simple..I want to make a launcher(I know how to make a *.desktop file). But in a .desktop file you always give path to executable file(generally .sh). Here,there is no script in the Grive folder.The app is as usual in /usr/bin/grive Now how do I make the launcher to first navigate to the grive folder and then execut the grive command.. Thanx :)

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• How can I get my game to show up in the Games Explorer on Windows?

  - by Kraemer

  I want to create an installer for a game which allows for an icon to be put in the Games Explorer for Vista and Windows 7. I have created the GDF, then built the script for project and obtained the .h, .gdf and .rc files. But I can't compile (using Visual Studio 2010) the .rc file into an executable to be used after that in order to create the installer. I get the following error after I set the executable path: "Could not load file or assembly'Microsoft.VisualStudio.HpcDebugger.Impl, Version 10.0.0.0, Culture=neutral, PublickKeyToken=b03f5f7f11d50a3a' or one of its dependencies. The system cannot find the file specified." Any ideas what I'm doing wrong?

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• Is software support an option for your career?

  - by Maria Sandu

  Normal 0 false false false EN-US X-NONE X-NONE MicrosoftInternetExplorer4 If you have a technical background, why should you choose a career in support? We have invited Serban to answer these questions and to give us an overview of one of the biggest technical teams in Oracle Romania. He’s been with Oracle for 7 years leading the local PeopleSoft Financials & Supply Chain Support team. Back in 2013 Serban started building a new support team in Romania – Fusion HCM. His current focus is building a strong support team for Fusion HCM, latest solution for Business HR Professionals from Oracle. The solution is offered both on Premise (customer site installation) but more important as a Cloud offering – SaaS.  So, why should a technical person choose Software Support over other technical areas?  “I think it is mainly because of the high level of technical skills required to provide the best technical solutions to our customers. Oracle Software Support covers complex solutions going from Database or Middleware to a vast area of business applications (basically covering any needs that a large enterprise may have). Working with such software requires very strong skills both technical and functional for the different areas, going from Finance, Supply Chain Management, Manufacturing, Sales to other very specific business processes. Our customers are large enterprises that already have a support layer inside their organization and therefore the Oracle Technical Support Engineers are working with highly specialized staff (DBA’s, System/Application Admins, Implementation Consultants). This is a very important aspect for our engineers because they need to be highly skilled to match our customer’s specialist’s expectations”.  What’s the career path in your team? “Technical Analysts joining our teams have a clear growth path. The main focus is to become a master of the product they will support. I think one need 1 or 2 years to reach a good level of understanding the product and delivering optimal solutions because of the complexity of our products. At a later stage, engineers can choose their professional development areas based on the business needs and preferences and then further grow towards as technical expert or a management role. We have analysts that have more than 15 years of technical expertise and they still learn and grow in technical area. Important fact is, due to the expansion of the Romanian Software support center, there are various management opportunities. So, if you want to leverage your experience and if you want to have people management responsibilities Oracle Software Support is the place to be!”  Our last question to Serban was about the benefits of being part of Oracle Software Support. Here is what he said: “We believe that Oracle delivers “State of the art” Support level to our customers. This is not possible without high investment in our staff. We commit from the start to support any technical analyst that joins us (being junior or very senior) with any training needs they have for their job. We have various technical trainings as well as soft-skills trainings required for a customer facing professional to be successful in his role. Last but not least, we’re aiming to make Oracle Romania SW Support a global center of excellence which means we’re investing a lot in our employees.”  If you’re looking for a job where you can combine your strong technical skills with customer interaction Oracle Software Support is the place to be! Send us your CV at [email protected]. /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin-top:0in; mso-para-margin-right:0in; mso-para-margin-bottom:10.0pt; mso-para-margin-left:0in; line-height:115%; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi;}

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• The true cost to get my XNA game on XBox?

  - by Fëanor

  There seem to be many hurdles to get ones game onto Xbox, so far I have uncovered: You need Visual Studio (once your game becomes commercial you cannot use Express - but have to pay for professional). $1000+ You then buy a XBox to find you also need a harddrive - so buy a Xbox harddrive too. $400 You need to buy XBox Gold LIVE subscription. $70 You need to buy AppHub Creators Club subscription $100 Then after all that I cannot even find the place on my XBox to download Indie games?!!! Seriously WTF - after doing all this I could have come proficient in WebGL and done it all for free... Before I go all the way down this path (hole) are there any other hidden hurdels before I can publish my game? UPDATE: "Indie Games are not available in Australia, due to the requirement for all games to be rated by the Australian Classification Board, and the prohibitive expenses involved."....... im going to have to break something....

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• returning null vs returning zero, which would be better?

  - by Dark Star1

  I inherited a project that I am managing and having to maintain pending the redevelopment of the code base. At the moment I am being tasked with adding little feature all over the place and have gotten into the habit of returning null instead of zero in parts of the code where I am working on. The problem is we have a client that is using this code and parts of code that require data from my implemented features recieve a null and dump the stack trace in UI. I would like to avoid this entirely from my input but without the nullPointer exceptions there's the potential that errors would be introduced into the client's data which may go un-noticed. Usually I would have come up with my own error notification system but I have never inherited a project before. so I am unsure whether to continue down this path. I still believe that the stack dump is preferable to un-noticed data corruption/inaccuracies.

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• Weird execution of ruby/git executables in Windows [migrated]

  - by Frexuz

  Something strange has happened. I can't run some command line executables in Windows anymore. Steps: Open cmd Run an executable, such as ruby -v or git -h When I do that, a new command prompt opens, running that command (I think, it's too fast to see), and instantly closes again. I've managed to print screen the new command prompt, and it shows that it's running inside this path: C:\Documents and Settings\Administrator\Local Settings\Temp\3582-490 Inside this folder, is the executable I'm tring to run. If I run ruby, then ruby.exe is in there. If I run git, then git.exe is in there. And it's always emptying the folder in between, so there is always just one .exe file

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• How important is index size when searching?

  - by Michael K

  My company has recently began using Apache Solr to search its data. As we learn how to use it we have gone down the path of indexing multiple fields to get the results we need. Most of these are either N-Grammed or Edge-N-Grammed. Gramming by nature takes up a lot of space, which takes more time to search. Space is cheap, but time is less so. Index time is not too important, since a delta-import (only get the changes since last index) is extremely quick and you only pay a penalty on the first import. What we've not been able to determine is what effect the index size has on query times. Obviously a larger index takes longer to search, but the time added by n-gramming a field is difficult to predict. How do you determine whether a field is worth gramming? Can you predict how much longer a query will take when you gram a field?

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• What do you do when the code isn't complicated enough?

  - by Chris

  After six months of development on a project, our stakeholders have had a "gut check" and have decided that the path that we've been walking (a custom designed application framework and data access layer) is holding us (the developers) back from quickly developing the features they would like to see. After several days of debate management and the development team have decided to scrap the current incarnation and start over using ASP.net MVC, with Entity Framework as the bases of the a 'quick and dirty', lets just get it done project. In days following, our senior developer who has never worked with MVC or Entity Framework has finally gotten into a sample project and done some work. His take on ASP.net MVC, "this is not software engineering". So my question is this; what do you do, when one doesn't think the code is complicated enough?

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• Using apt-get from Canada

  - by Advant Edge

  I am using Ubuntu Server 12.04 LTS, and until yesterday, everything was quite peachy. I have installed several packages (MySQL, apache2) and to my knowledge have those configured correctly. Upon configuration of phpMyAdmin, I found that I was missing the directory path /etc/phpmyadmin, which got me thinking about the install. I am new to Ubuntu, so I guess I missed the message telling me that I did not download phpMyAdmin successfully. Anyway, trying to use apt-get yesterday/today results in "Failed to fetch..." messages, even if just to run sudo apt-get update. Some notable details: ···no GUI, command line only (sudo apt-get gksu fails, go figure) ···can ping 4.2.2.2, so I know the internet is out there (somewhere) ···this is a dedicated computer, using Samba to share files with Windows, which does work ···attempted to edit my /sources.list file, for various American/Canadian mirror, to no effect ···ensured I have correct DNS settings in /etc/networks/interfaces I'm not sure where along the way it happened, but I seem to have lost connections to repositories... :) Any advice (including GO BACK TO WINDOWS) is appreciated.

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• APress Deal of the Day - 11/Nov/2011 - Accelerated C# 2010

  - by TATWORTH

  Today's $10 Deal of the day from Apress at http://www.apress.com/9781430225379 is Accelerated C# 2010 "C# 2010 offers powerful new features, and this book is the fastest path to mastering them—and the rest of C#—for both experienced C# programmers moving to C# 2010 and programmers moving to C# from another object-oriented language. " I cannot improve on the description on thew APress web site: "If you're an experienced C# programmer, you need to understand how C# has changed with C# 2010. If you're an experienced object-oriented programmer moving to C#, you want to ramp up quickly in the language while learning the latest features and techniques. In either case, this book is for you. The first three chapters succinctly present C# fundamentals, for those new to or reviewing C#. The rest of the book covers all the major C# features, in great detail, explaining how they work and how best to use them. Whatever your background or need, you’ll treasure this book for as long as you code in C# 2010."   Can't code withoutThe best C# & VB.NET refactoring plugin for Visual Studio

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• Function names - "standardized" prefixes

  - by dnsmkl

  Imagine you have such routines /*just do X. Fail if any precondition is not met*/ doX() /*take care of preconditions and then do X*/ takeCareOfPreconditionsCheckIfNeededAtAllAndThenDoX() A little bit more concrete example: /*create directory. Most probably fail with error if any precondition is not met (folder already exists, parent does not exists)*/ createDirectory(path_name) /*take care of preconditions (creates full path till folder if needed, checks if not exists yet) and then creates the directory*/ CheckIfNotExistsYet_CreateDirectory_andFullPathIfNeeded(path_name) How do you name such routines, so it would be clear what does what? I have come to some my own "convetion" like: naiveCreateDirectory, ForceDirectoryExists, ... But I imagine this is very standard situation. Maybe there already exists some norms/convetions for this?

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• How can I change resolution of "my video" in Skype?

  - by koushik

  I have a logitech Quickcam Pro 9000 connected to my ubuntu desktop and it works fine with Skype. However, Skype inputs and sends my video at the native (for the webcam I think) resolution of 1600 x 1200. I can confirm that the camera supports a wide variety of resolutions starting from 160 x 120 upto 1600 x 1200 (including e.g., 320 x 240, 352 x 288) using cheese. I can select these resolutions and see the output is appropriately scaled. Also, I don't see any improvements in smoothness of motion in the captured video so I suspect the original 1600 x 1200 is scaled down in the path somewhere. Is it possible to somehow to enable this scaling capability towards Skype?

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• Cron doesn't execute one of the scheduled jobs

  - by user288633

  I'm using a lubuntu desktop, distribution Ubuntu 13.10, i686. This is my problem: in the job list scheduled by cron a job hasn't effect, but in /var/log/syslog its execution is traced. This is the relative log line: Jun 4 09:06:01 kiosk CRON[14189]: (root) CMD (/usr/bin/xinput set-prop 12 --type=float "Coordinate Transformation Matrix" 0 -1 1 1 0 0 0 0 1 /tmp/mybackup.log) This job should rotate touchscreen mapping. I try different solutions: I substitute in crontab the with bash -c "", I set "export DISPLAY=:0.0" ("for Graphics related job in Unix Environment we need to set first the DISPLAY...") before the command,...and many other! I know there are a lots of details affect cron execution (path, environment variables, special character and other) and I have no more idea by now :( Could some gentleman suggest me an idea? where can I find the problem? Thanks in advance!

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• TFS Backup Plan Wizard Tool

  - by Enrique Lima

  With the release of the “September – 2010” TFS 2010 Power Tools, came an addition to the Team Foundation Server Administration Console.  This addition is the Team Foundation Backups Tree item.  The tool is used to create backup plans and to work with it you run through a wizard, just like you would in configuring TFS or any of the extensions it has. The areas covered through the tool include: Backup to a Network Backup Path, retention configuration. Under Advanced Options, the extension to be used for the Full and Transactional backups. The capability to include external databases, meaning, include the reporting databases and SharePoint databases as part of the plan. There are further options as you can see, that includes being able to define a task scheduler account, be able to set alerts for notifications on execution of the plans, and last the option to configure the schedule for the plan execution.  All in all a very good tool and great way to safeguard the investment you’ve made.

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• Cron won't execute if am not logged in

  - by JonaMX

  I have a cron that makes a backup of MySql, if I execute on shell it works pretty well even if I'm logged when cron supposed to execute works fine, but if I'm not logged just won't execute, I don't know what could happened, any suggestion ? Crontab 00 04 * * * /home/administrador/scripts/respaldo.sh respaldo.sh #!/bin/sh mysql -uroot -p[PASS] ccs < /home/administrador/scripts/limpia.sql mysqldump -uroot -p[PASS] --routines ccs > /home/administrador/backups/backup_$(date +%Y%m%d).sql mysqlcheck -uroot -p[PASS] --auto-repair --optimize ccs cd /home/administrador/backups/ tar -zcf backup_$(date +%Y%m%d).tgz backup_$(date +%Y%m%d).sql rm backup_$(date +%Y%m%d).sql find -name '*.tgz' -type f -mtime +90 -exec rm -f {} \; respaldo.sh has execute permission SOLUTION The problema was that the /home/adminsitrador directory was an encrypted folder so when the user is logged in the folder it's decrypted and everything works but when the user it's logged off the folder it's encrypted and the cron can't access to that path, so I've changed the cron script and backup to another unencrypted folder and to root user and now everything it's working pretty well, thanks to all for your help !

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• Read data from a folder in main domain folder (CPanel\WHM)

  - by Memphis Raines

  I have defined a host in my CPanel\WHM server and put all my websites under one host account. The host Main Domain is domain.com, and all other websites are Add-on Domains: domain.com --folder --domain1 --domain2 --domain3 ... The thing I need is that when calling domain.com in browser, the server read files from another folder. for example when call http://domain.com it shows us http://domain.com/folder BUT I don't mean a redirection, I want server do this in background without showing visitors the real path. I couldn't do this with Domain WildCard Redirection because it got error. How can I do this? With htaccess or ... ?

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• Qualifying 'happiness' in software development?

  - by mummey

  It occurred to me today that often the real goal of questions asked on sites such as this one (where the questions tend to be more open-ended than say, SO) is for the OP to become happier upon achieving the result. We often excuse this by saying our desire is to be more productive or release a better product, but if you continue to look down this path you can determine that the OP seeks greater productivity or product-quality because those are important to his/her 'happiness'. With that in-mind I ask this: Have their been efforts to study software development from this perspective? In other words, what practises increase happiness in those who develop software as a career, and who, if anyone, has researched this specifically? As I mentioned above, they may include strategies that increase productivity or improve product quality, but by no means should they be limited to just those.

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• My Oracle Support Accreditation for Database and Enterprise Manager

  - by A. G.

  Have you actively used My Oracle Support for 6-9 months? Take your expertise to the next level—become accredited! By completing the accreditation learning series, you can increase your proficiency with My Oracle Support’s core functions and build skills to help you leverage Oracle solutions, tools, and knowledge that enable productivity. Accreditation learning paths are available for Oracle Database and Enterprise Manager, which focus on product-specific best practices, recommendations, and tool enablement—up leveling your capabilities with these Oracle products. Course topics include:   Oracle Database Staying informed  Install Patching Upgrade Performance Security Scalability Enterprise Manager Staying informed  Supportability Certification Patching Upgrade Performance Diagnostic Tools Troubleshooting Visit the My Oracle Support Accreditation Index and get started with the Level 1 My Oracle Support Accreditation path and product-specific Level 2 learning paths for Oracle Database and Enterprise Manager.

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• Using XA Transactions in Coherence-based Applications

  - by jpurdy

  While the costs of XA transactions are well known (e.g. increased data contention, higher latency, significant disk I/O for logging, availability challenges, etc.), in many cases they are the most attractive option for coordinating logical transactions across multiple resources. There are a few common approaches when integrating Coherence into applications via the use of an application server's transaction manager: Use of Coherence as a read-only cache, applying transactions to the underlying database (or any system of record) instead of the cache. Use of TransactionMap interface via the included resource adapter. Use of the new ACID transaction framework, introduced in Coherence 3.6.   Each of these may have significant drawbacks for certain workloads. Using Coherence as a read-only cache is the simplest option. In this approach, the application is responsible for managing both the database and the cache (either within the business logic or via application server hooks). This approach also tends to provide limited benefit for many workloads, particularly those workloads that either have queries (given the complexity of maintaining a fully cached data set in Coherence) or are not read-heavy (where the cost of managing the cache may outweigh the benefits of reading from it). All updates are made synchronously to the database, leaving it as both a source of latency as well as a potential bottleneck. This approach also prevents addressing "hot data" problems (when certain objects are updated by many concurrent transactions) since most database servers offer no facilities for explicitly controlling concurrent updates. Finally, this option tends to be a better fit for key-based access (rather than filter-based access such as queries) since this makes it easier to aggressively invalidate cache entries without worrying about when they will be reloaded. The advantage of this approach is that it allows strong data consistency as long as optimistic concurrency control is used to ensure that database updates are applied correctly regardless of whether the cache contains stale (or even dirty) data. Another benefit of this approach is that it avoids the limitations of Coherence's write-through caching implementation. TransactionMap is generally used when Coherence acts as system of record. TransactionMap is not generally compatible with write-through caching, so it will usually be either used to manage a standalone cache or when the cache is backed by a database via write-behind caching. TransactionMap has some restrictions that may limit its utility, the most significant being: The lock-based concurrency model is relatively inefficient and may introduce significant latency and contention. As an example, in a typical configuration, a transaction that updates 20 cache entries will require roughly 40ms just for lock management (assuming all locks are granted immediately, and excluding validation and writing which will require a similar amount of time). This may be partially mitigated by denormalizing (e.g. combining a parent object and its set of child objects into a single cache entry), at the cost of increasing false contention (e.g. transactions will conflict even when updating different child objects). If the client (application server JVM) fails during the commit phase, locks will be released immediately, and the transaction may be partially committed. In practice, this is usually not as bad as it may sound since the commit phase is usually very short (all locks having been previously acquired). Note that this vulnerability does not exist when a single NamedCache is used and all updates are confined to a single partition (generally implying the use of partition affinity). The unconventional TransactionMap API is cumbersome but manageable. Only a few methods are transactional, primarily get(), put() and remove(). The ACID transactions framework (accessed via the Connection class) provides atomicity guarantees by implementing the NamedCache interface, maintaining its own cache data and transaction logs inside a set of private partitioned caches. This feature may be used as either a local transactional resource or as logging XA resource. However, a lack of database integration precludes the use of this functionality for most applications. A side effect of this is that this feature has not seen significant adoption, meaning that any use of this is subject to the usual headaches associated with being an early adopter (greater chance of bugs and greater risk of hitting an unoptimized code path). As a result, for the moment, we generally recommend against using this feature. In summary, it is possible to use Coherence in XA-oriented applications, and several customers are doing this successfully, but it is not a core usage model for the product, so care should be taken before committing to this path. For most applications, the most robust solution is normally to use Coherence as a read-only cache of the underlying data resources, even if this prevents taking advantage of certain product features.

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