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  • backgroundworkers or threadpools

    - by vbNewbie
    I am trying to create an app that allows multiple search requests to occur whilst maintaining use of the user interface to allow interaction. For the multiple search requests, I initially only had one search request running with user interaction still capable by using a backgroundworker to do this. Now I need to extend these functions by allowing more search functions and basically just queueing them up. I am not sure whether to use multiple backgroundworkers or use the threadpool since I want to be able to know the progress of each search job at any time.

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  • Replacing Text which does not match a pattern in Oracle

    - by kutekrish
    I have below text in a CLOB in a table Table Name: tbl1 Columns col1 - number (Primary Key) col2 - clob (as below) Row#1 ----- Col1 = 1 Col2 = 1331882981,ab123456,Some text here which can run multiple lines and have a lot of text... ~1331890329,pqr123223,Some more text... Row#2 ----- Col1 = 2 Col2 = 1331882981,abc333,Some text here which can run multiple lines and have a lot of text... ~1331890329,pqrs23,Some more text... Now I need to know how we can get below output Col1 Value ---- --------------------- 1 1331882981,ab123456 1 1331890329,pqr123223 2 1331882981,abc333 2 1331890329,pqrs23 ([0-9]{10},[a-z 0-9]+.), == This is the regular expression to match "1331890329,pqrs23" and I need to know how can replace which are not matching this regex and then split them into multiple rows

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  • Distributing requests to Selenium Grid RC's?

    - by intervigil
    I've got a situation here where I have a central selenium grid hub, and several RC's running on my gogrid account. When I access it to run tests, it basically queues all the incoming test requests and executes them serially on only one of the RC's, instead of spreading them out to use available RC's. The tests come from multiple projects, so I'm not looking to parallelize the tests themselves, just to split the requests that come from multiple projects across the multiple RC's. From everything I've read, it seems like selenium grid should be doing this already, yet I only see one RC used to run every single test. Is there something I'm missing?

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  • Split SQL statements

    - by eaZy
    Hello, I am writing a backend application which needs to be able to send multiple SQL commands to a MySQL server. MySQL = 5.x support multiple statements, but unfortunately we are interfacing with MySQL 4.x. I am trying to find a way (hint: regex) to split SQL statements by their semicolon, but it should ignore semicolons in single and double quotes strings. http://www.dev-explorer.com/articles/multiple-mysql-queries has a very nice regex to do that, but doesn't support double quotes. I'd be happy to hear your suggestions.

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  • How to turn one server into many servers? (Virtualization/VMWare)

    - by user1229962
    I'm hoping for a high level discussion of this problem I know is quickly approaching my application. I have a server that binds on a specific port and manages TCP Sockets from my clients. I know that it is common practice to use VMWare to virtualize servers and run multiple servers at once. How can a single server design be changed to support multiple servers? Multiple servers can't bind to the same port. If I had to guess I would say a proxy server binds to the port and then sends connections off to the other servers to be handled as if it was still a single server application. I'm wondering what options there are and what are the common practices for solving this problem? Thanks in advance!

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  • C#: System.Lazy&lt;T&gt; and the Singleton Design Pattern

    - by James Michael Hare
    So we've all coded a Singleton at one time or another.  It's a really simple pattern and can be a slightly more elegant alternative to global variables.  Make no mistake, Singletons can be abused and are often over-used -- but occasionally you find a Singleton is the most elegant solution. For those of you not familiar with a Singleton, the basic Design Pattern is that a Singleton class is one where there is only ever one instance of the class created.  This means that constructors must be private to avoid users creating their own instances, and a static property (or method in languages without properties) is defined that returns a single static instance. 1: public class Singleton 2: { 3: // the single instance is defined in a static field 4: private static readonly Singleton _instance = new Singleton(); 5:  6: // constructor private so users can't instantiate on their own 7: private Singleton() 8: { 9: } 10:  11: // read-only property that returns the static field 12: public static Singleton Instance 13: { 14: get 15: { 16: return _instance; 17: } 18: } 19: } This is the most basic singleton, notice the key features: Static readonly field that contains the one and only instance. Constructor is private so it can only be called by the class itself. Static property that returns the single instance. Looks like it satisfies, right?  There's just one (potential) problem.  C# gives you no guarantee of when the static field _instance will be created.  This is because the C# standard simply states that classes (which are marked in the IL as BeforeFieldInit) can have their static fields initialized any time before the field is accessed.  This means that they may be initialized on first use, they may be initialized at some other time before, you can't be sure when. So what if you want to guarantee your instance is truly lazy.  That is, that it is only created on first call to Instance?  Well, there's a few ways to do this.  First we'll show the old ways, and then talk about how .Net 4.0's new System.Lazy<T> type can help make the lazy-Singleton cleaner. Obviously, we could take on the lazy construction ourselves, but being that our Singleton may be accessed by many different threads, we'd need to lock it down. 1: public class LazySingleton1 2: { 3: // lock for thread-safety laziness 4: private static readonly object _mutex = new object(); 5:  6: // static field to hold single instance 7: private static LazySingleton1 _instance = null; 8:  9: // property that does some locking and then creates on first call 10: public static LazySingleton1 Instance 11: { 12: get 13: { 14: if (_instance == null) 15: { 16: lock (_mutex) 17: { 18: if (_instance == null) 19: { 20: _instance = new LazySingleton1(); 21: } 22: } 23: } 24:  25: return _instance; 26: } 27: } 28:  29: private LazySingleton1() 30: { 31: } 32: } This is a standard double-check algorithm so that you don't lock if the instance has already been created.  However, because it's possible two threads can go through the first if at the same time the first time back in, you need to check again after the lock is acquired to avoid creating two instances. Pretty straightforward, but ugly as all heck.  Well, you could also take advantage of the C# standard's BeforeFieldInit and define your class with a static constructor.  It need not have a body, just the presence of the static constructor will remove the BeforeFieldInit attribute on the class and guarantee that no fields are initialized until the first static field, property, or method is called.   1: public class LazySingleton2 2: { 3: // because of the static constructor, this won't get created until first use 4: private static readonly LazySingleton2 _instance = new LazySingleton2(); 5:  6: // Returns the singleton instance using lazy-instantiation 7: public static LazySingleton2 Instance 8: { 9: get { return _instance; } 10: } 11:  12: // private to prevent direct instantiation 13: private LazySingleton2() 14: { 15: } 16:  17: // removes BeforeFieldInit on class so static fields not 18: // initialized before they are used 19: static LazySingleton2() 20: { 21: } 22: } Now, while this works perfectly, I hate it.  Why?  Because it's relying on a non-obvious trick of the IL to guarantee laziness.  Just looking at this code, you'd have no idea that it's doing what it's doing.  Worse yet, you may decide that the empty static constructor serves no purpose and delete it (which removes your lazy guarantee).  Worse-worse yet, they may alter the rules around BeforeFieldInit in the future which could change this. So, what do I propose instead?  .Net 4.0 adds the System.Lazy type which guarantees thread-safe lazy-construction.  Using System.Lazy<T>, we get: 1: public class LazySingleton3 2: { 3: // static holder for instance, need to use lambda to construct since constructor private 4: private static readonly Lazy<LazySingleton3> _instance 5: = new Lazy<LazySingleton3>(() => new LazySingleton3()); 6:  7: // private to prevent direct instantiation. 8: private LazySingleton3() 9: { 10: } 11:  12: // accessor for instance 13: public static LazySingleton3 Instance 14: { 15: get 16: { 17: return _instance.Value; 18: } 19: } 20: } Note, you need your lambda to call the private constructor as Lazy's default constructor can only call public constructors of the type passed in (which we can't have by definition of a Singleton).  But, because the lambda is defined inside our type, it has access to the private members so it's perfect. Note how the Lazy<T> makes it obvious what you're doing (lazy construction), instead of relying on an IL generation side-effect.  This way, it's more maintainable.  Lazy<T> has many other uses as well, obviously, but I really love how elegant and readable it makes the lazy Singleton.

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  • Professional WordPress Business Themes

    - by Matt
    Every now and then JustSkins.com receives quote requests for WordPress design for business websites. Most companies now keep up to date with a blog on their corporate website, that showcases their day to day activities & progresses.  Getting such professional wordpress driven website designed from the scratch costs you a lot. If you have decided to make WordPress the CMS for your business website, there are some Professional WordPress themes you can take a look at. We have created this list to help you save some time to do all the trying and the testing. Optimize by WooThemes Last year one of the most popular Business theme by WooThemes was the Coffee Break theme, Optimize is further adaptation of the same. It is simple, sleek design with great functionality. The customizable front page lets you showcase your work or product etc. Demo | Price: $70, Developer Price: $150 | DOWNLOAD WooThemes is also offering their whole Business theme pack for a very very reasonable fee, If you like multiple designs from them you can get this big deal for only $125 Onyx , Impacto by Simple Themes Simple Themes has been making very crisp & beautiful WordPress Themes & are also very reasonably priced. If their themes solve your purpose $39 membership for 3 months is a good deal.  If you are looking to create quick website, landing page or micro site their templates are best. Demo | Price: $39 for 3 Months Membership Rejuvenate by Templatic One of the most beautiful Premium WordPress Theme, Available in 4 elegant color schemes. This theme can be used for your Beauty, Spa and Studio Business. Demo | Price: $65  | DOWNLOAD Templatic has created great professional business templates, such as Gourmet, Real Estate, Job Board, Automobile & lots More. You can also get a Best Value Offer in $299 for all of Templatic Themes. TheProfessional by ElegantThemes Elegant Themes is known to provide very beautiful & straightforward designs. The professional wordpress theme is a simple, crisp & concise Theme you can use to create a business website. The 3 short blurbs on the homepage are simple, which can be used to point them to your major offerings and the prominent slider indicates a clear call to action. There are 52 themes to choose from & Elegant Themes is giving a great offer at such a small yearly fee. Demo | Price: $39 Yearly Membership  | DOWNLOAD Elegant Themes has a cluster of 52 magnificent themes, and all you have to do is pay $39 to win access to all of them. Join today! Some of the Professional designs that I like for a business website are SimplePress and Corporation. Extatic by Chimera Themes The theme includes plenty of great features including custom feature tour pages, portfolio sections, static feature areas, pricing table page, 20+ shortcodes, multiple page/post options, unlimited custom sidebars which can be assigned to posts/pages, advanced theme style editor and options page and much more. Its a must buy Demo | Price: $37 | DOWNLOAD Corporate by Clover Themes Simple Theme for a small business. Corporate is an clean, powerful and feature-rich corporate theme with dynamic and energy design. Demo | Price: $69.95 | DOWNLOAD Bizco by Themify Bizco is a very professional template for wordpress targeted at corporate and product based businesses. This theme is simple yet highly functional and is suitable for showcasing features of your service or product. With the custom page template you can change the display of your pages and posts easily with our visual custom panel. Demo | Price: $70  |DOWNLOAD Devision by Themetrust Devision is a small business wordpress theme that can be used to make a business website within a few minutes. It makes it very easy to showcase and highlight your services or product on the homepage. Demo | Price: Euro 39 | DOWNLOAD BizPress by WPZoom A professional business WordPress theme from WPZoom suitable for companies, organizations, product showcases or other business websites. The theme comes with 4 colour options, featured products / services slider on the homepage, drop down menus, theme options page etc. Demo | Price: $ 69 | DOWNLOAD Clean Classy Corporate by ThemeFuse A very impressive WordPress business theme, that can be used in multiple ways. It is suitable for many kinds, like web products, services, hosting etc etc. Clean Classy Corporate WordPress Theme has a clean crisp look and is professional in appeal. Demo | Price: $49  | DOWNLOAD Insdustry by ThemeJam A powerful Business WordPress Template along with lots of options, colors, and customizable features. This is one for almost any kind of blogger, corporate, or organization. Lots of features, gives it the kind of scalability you might need to create any kind of website. Demo | Price: $ 59 | DOWNLOAD AppPress by ChimeraThemes This professional business WordPress theme includes 5 different colour schemes, advanced theme options page, multiple homepage sliders, custom widgets and page templates. The theme also includes a range of other unique features such as custom title, live style editor to modify colours, font styles, sizes etc, and 20+ shortcodes for creating pricing tables, content columns, boxes, buttons and others. Demo | Price: $ 37 | DOWNLOAD Why WordPress Professional Template? You can modify them, these usually come with a lot of fancy features that enable you to create the website as per your usability & choice. In some cases the  Premium WordPress business themes can be accessed through a subscription service. Premium Vs Free WordPress Themes There are very good Free WordPress themes out there that you can use to modify and code further or create what you want, but this possible when you are technically able. On the contrary Premium WordPress business themes offers great features & can save you a lot of time and money. It varies from business to business, some like to keep their website simple while most want to keep cool nifty features and abilities to scale it differently for various sections, products or categories. All this & more is possible with a Professional Business theme that is suitable/close to your needs.

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  • Building and Deploying Windows Azure Web Sites using Git and GitHub for Windows

    - by shiju
    Microsoft Windows Azure team has released a new version of Windows Azure which is providing many excellent features. The new Windows Azure provides Web Sites which allows you to deploy up to 10 web sites  for free in a multitenant shared environment and you can easily upgrade this web site to a private, dedicated virtual server when the traffic is grows. The Meet Windows Azure Fact Sheet provides the following information about a Windows Azure Web Site: Windows Azure Web Sites enable developers to easily build and deploy websites with support for multiple frameworks and popular open source applications, including ASP.NET, PHP and Node.js. With just a few clicks, developers can take advantage of Windows Azure’s global scale without having to worry about operations, servers or infrastructure. It is easy to deploy existing sites, if they run on Internet Information Services (IIS) 7, or to build new sites, with a free offer of 10 websites upon signup, with the ability to scale up as needed with reserved instances. Windows Azure Web Sites includes support for the following: Multiple frameworks including ASP.NET, PHP and Node.js Popular open source software apps including WordPress, Joomla!, Drupal, Umbraco and DotNetNuke Windows Azure SQL Database and MySQL databases Multiple types of developer tools and protocols including Visual Studio, Git, FTP, Visual Studio Team Foundation Services and Microsoft WebMatrix Signup to Windows and Enable Azure Web Sites You can signup for a 90 days free trial account in Windows Azure from here. After creating an account in Windows Azure, go to https://account.windowsazure.com/ , and select to preview features to view the available previews. In the Web Sites section of the preview features, click “try it now” which will enables the web sites feature Create Web Site in Windows Azure To create a web sites, login to the Windows Azure portal, and select Web Sites from and click New icon from the left corner  Click WEB SITE, QUICK CREATE and put values for URL and REGION dropdown. You can see the all web sites from the dashboard of the Windows Azure portal Set up Git Publishing Select your web site from the dashboard, and select Set up Git publishing To enable Git publishing , you must give user name and password which will initialize a Git repository Clone Git Repository We can use GitHub for Windows to publish apps to non-GitHub repositories which is well explained by Phil Haack on his blog post. Here we are going to deploy the web site using GitHub for Windows. Let’s clone a Git repository using the Git Url which will be getting from the Windows Azure portal. Let’s copy the Git url and execute the “git clone” with the git url. You can use the Git Shell provided by GitHub for Windows. To get it, right on the GitHub for Windows, and select open shell here as shown in the below picture. When executing the Git Clone command, it will ask for a password where you have to give password which specified in the Windows Azure portal. After cloning the GIT repository, you can drag and drop the local Git repository folder to GitHub for Windows GUI. This will automatically add the Windows Azure Web Site repository onto GitHub for Windows where you can commit your changes and publish your web sites to Windows Azure. Publish the Web Site using GitHub for Windows We can add multiple framework level files including ASP.NET, PHP and Node.js, to the local repository folder can easily publish to Windows Azure from GitHub for Windows GUI. For this demo, let me just add a simple Node.js file named Server.js which handles few request handlers. 1: var http = require('http'); 2: var port=process.env.PORT; 3: var querystring = require('querystring'); 4: var utils = require('util'); 5: var url = require("url"); 6:   7: var server = http.createServer(function(req, res) { 8: switch (req.url) { //checking the request url 9: case '/': 10: homePageHandler (req, res); //handler for home page 11: break; 12: case '/register': 13: registerFormHandler (req, res);//hamdler for register 14: break; 15: default: 16: nofoundHandler (req, res);// handler for 404 not found 17: break; 18: } 19: }); 20: server.listen(port); 21: //function to display the html form 22: function homePageHandler (req, res) { 23: console.log('Request handler home was called.'); 24: res.writeHead(200, {'Content-Type': 'text/html'}); 25: var body = '<html>'+ 26: '<head>'+ 27: '<meta http-equiv="Content-Type" content="text/html; '+ 28: 'charset=UTF-8" />'+ 29: '</head>'+ 30: '<body>'+ 31: '<form action="/register" method="post">'+ 32: 'Name:<input type=text value="" name="name" size=15></br>'+ 33: 'Email:<input type=text value="" name="email" size=15></br>'+ 34: '<input type="submit" value="Submit" />'+ 35: '</form>'+ 36: '</body>'+ 37: '</html>'; 38: //response content 39: res.end(body); 40: } 41: //handler for Post request 42: function registerFormHandler (req, res) { 43: console.log('Request handler register was called.'); 44: var pathname = url.parse(req.url).pathname; 45: console.log("Request for " + pathname + " received."); 46: var postData = ""; 47: req.on('data', function(chunk) { 48: // append the current chunk of data to the postData variable 49: postData += chunk.toString(); 50: }); 51: req.on('end', function() { 52: // doing something with the posted data 53: res.writeHead(200, "OK", {'Content-Type': 'text/html'}); 54: // parse the posted data 55: var decodedBody = querystring.parse(postData); 56: // output the decoded data to the HTTP response 57: res.write('<html><head><title>Post data</title></head><body><pre>'); 58: res.write(utils.inspect(decodedBody)); 59: res.write('</pre></body></html>'); 60: res.end(); 61: }); 62: } 63: //Error handler for 404 no found 64: function nofoundHandler(req, res) { 65: console.log('Request handler nofound was called.'); 66: res.writeHead(404, {'Content-Type': 'text/plain'}); 67: res.end('404 Error - Request handler not found'); 68: } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } If there is any change in the local repository folder, GitHub for Windows will automatically detect the changes. In the above step, we have just added a Server.js file so that GitHub for Windows will detect the changes. Let’s commit the changes to the local repository before publishing the web site to Windows Azure. After committed the all changes, you can click publish button which will publish the all changes to Windows Azure repository. The following screen shot shows deployment history from the Windows Azure portal.   GitHub for Windows is providing a sync button which can use for synchronizing between local repository and Windows Azure repository after making any commit on the local repository after any changes. Our web site is running after the deployment using Git Summary Windows Azure Web Sites lets the developers to easily build and deploy websites with support for multiple framework including ASP.NET, PHP and Node.js and can easily deploy the Web Sites using Visual Studio, Git, FTP, Visual Studio Team Foundation Services and Microsoft WebMatrix. In this demo, we have deployed a Node.js Web Site to Windows Azure using Git. We can use GitHub for Windows to publish apps to non-GitHub repositories and can use to publish Web SItes to Windows Azure.

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  • Linux-Containers — Part 1: Overview

    - by Lenz Grimmer
    "Containers" by Jean-Pierre Martineau (CC BY-NC-SA 2.0). Linux Containers (LXC) provide a means to isolate individual services or applications as well as of a complete Linux operating system from other services running on the same host. To accomplish this, each container gets its own directory structure, network devices, IP addresses and process table. The processes running in other containers or the host system are not visible from inside a container. Additionally, Linux Containers allow for fine granular control of resources like RAM, CPU or disk I/O. Generally speaking, Linux Containers use a completely different approach than "classicial" virtualization technologies like KVM or Xen (on which Oracle VM Server for x86 is based on). An application running inside a container will be executed directly on the operating system kernel of the host system, shielded from all other running processes in a sandbox-like environment. This allows a very direct and fair distribution of CPU and I/O-resources. Linux containers can offer the best possible performance and several possibilities for managing and sharing the resources available. Similar to Containers (or Zones) on Oracle Solaris or FreeBSD jails, the same kernel version runs on the host as well as in the containers; it is not possible to run different Linux kernel versions or other operating systems like Microsoft Windows or Oracle Solaris for x86 inside a container. However, it is possible to run different Linux distribution versions (e.g. Fedora Linux in a container on top of an Oracle Linux host), provided it supports the version of the Linux kernel that runs on the host. This approach has one caveat, though - if any of the containers causes a kernel crash, it will bring down all other containers (and the host system) as well. For example, Oracle's Unbreakable Enterprise Kernel Release 2 (2.6.39) is supported for both Oracle Linux 5 and 6. This makes it possible to run Oracle Linux 5 and 6 container instances on top of an Oracle Linux 6 system. Since Linux Containers are fully implemented on the OS level (the Linux kernel), they can be easily combined with other virtualization technologies. It's certainly possible to set up Linux containers within a virtualized Linux instance that runs inside Oracle VM Server for Oracle VM Virtualbox. Some use cases for Linux Containers include: Consolidation of multiple separate Linux systems on one server: instances of Linux systems that are not performance-critical or only see sporadic use (e.g. a fax or print server or intranet services) do not necessarily need a dedicated server for their operations. These can easily be consolidated to run inside containers on a single server, to preserve energy and rack space. Running multiple instances of an application in parallel, e.g. for different users or customers. Each user receives his "own" application instance, with a defined level of service/performance. This prevents that one user's application could hog the entire system and ensures, that each user only has access to his own data set. It also helps to save main memory — if multiple instances of a same process are running, the Linux kernel can share memory pages that are identical and unchanged across all application instances. This also applies to shared libraries that applications may use, they are generally held in memory once and mapped to multiple processes. Quickly creating sandbox environments for development and testing purposes: containers that have been created and configured once can be archived as templates and can be duplicated (cloned) instantly on demand. After finishing the activity, the clone can safely be discarded. This allows to provide repeatable software builds and test environments, because the system will always be reset to its initial state for each run. Linux Containers also boot significantly faster than "classic" virtual machines, which can save a lot of time when running frequent build or test runs on applications. Safe execution of an individual application: if an application running inside a container has been compromised because of a security vulnerability, the host system and other containers remain unaffected. The potential damage can be minimized, analyzed and resolved directly from the host system. Note: Linux Containers on Oracle Linux 6 with the Unbreakable Enterprise Kernel Release 2 (2.6.39) are still marked as Technology Preview - their use is only recommended for testing and evaluation purposes. The Open-Source project "Linux Containers" (LXC) is driving the development of the technology behind this, which is based on the "Control Groups" (CGroups) and "Name Spaces" functionality of the Linux kernel. Oracle is actively involved in the Linux Containers development and contributes patches to the upstream LXC code base. Control Groups provide means to manage and monitor the allocation of resources for individual processes or process groups. Among other things, you can restrict the maximum amount of memory, CPU cycles as well as the disk and network throughput (in MB/s or IOP/s) that are available for an application. Name Spaces help to isolate process groups from each other, e.g. the visibility of other running processes or the exclusive access to a network device. It's also possible to restrict a process group's access and visibility of the entire file system hierarchy (similar to a classic "chroot" environment). CGroups and Name Spaces provide the foundation on which Linux containers are based on, but they can actually be used independently as well. A more detailed description of how Linux Containers can be created and managed on Oracle Linux will be explained in the second part of this article. Additional links related to Linux Containers: OTN Article: The Role of Oracle Solaris Zones and Linux Containers in a Virtualization Strategy Linux Containers on Wikipedia - Lenz Grimmer Follow me on: Personal Blog | Facebook | Twitter | Linux Blog |

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  • ASP.NET MVC 3: Razor’s @: and <text> syntax

    - by ScottGu
    This is another in a series of posts I’m doing that cover some of the new ASP.NET MVC 3 features: New @model keyword in Razor (Oct 19th) Layouts with Razor (Oct 22nd) Server-Side Comments with Razor (Nov 12th) Razor’s @: and <text> syntax (today) In today’s post I’m going to discuss two useful syntactical features of the new Razor view-engine – the @: and <text> syntax support. Fluid Coding with Razor ASP.NET MVC 3 ships with a new view-engine option called “Razor” (in addition to the existing .aspx view engine).  You can learn more about Razor, why we are introducing it, and the syntax it supports from my Introducing Razor blog post.  Razor minimizes the number of characters and keystrokes required when writing a view template, and enables a fast, fluid coding workflow. Unlike most template syntaxes, you do not need to interrupt your coding to explicitly denote the start and end of server blocks within your HTML. The Razor parser is smart enough to infer this from your code. This enables a compact and expressive syntax which is clean, fast and fun to type. For example, the Razor snippet below can be used to iterate a list of products: When run, it generates output like:   One of the techniques that Razor uses to implicitly identify when a code block ends is to look for tag/element content to denote the beginning of a content region.  For example, in the code snippet above Razor automatically treated the inner <li></li> block within our foreach loop as an HTML content block because it saw the opening <li> tag sequence and knew that it couldn’t be valid C#.  This particular technique – using tags to identify content blocks within code – is one of the key ingredients that makes Razor so clean and productive with scenarios involving HTML creation. Using @: to explicitly indicate the start of content Not all content container blocks start with a tag element tag, though, and there are scenarios where the Razor parser can’t implicitly detect a content block. Razor addresses this by enabling you to explicitly indicate the beginning of a line of content by using the @: character sequence within a code block.  The @: sequence indicates that the line of content that follows should be treated as a content block: As a more practical example, the below snippet demonstrates how we could output a “(Out of Stock!)” message next to our product name if the product is out of stock: Because I am not wrapping the (Out of Stock!) message in an HTML tag element, Razor can’t implicitly determine that the content within the @if block is the start of a content block.  We are using the @: character sequence to explicitly indicate that this line within our code block should be treated as content. Using Code Nuggets within @: content blocks In addition to outputting static content, you can also have code nuggets embedded within a content block that is initiated using a @: character sequence.  For example, we have two @: sequences in the code snippet below: Notice how within the second @: sequence we are emitting the number of units left within the content block (e.g. - “(Only 3 left!”). We are doing this by embedding a @p.UnitsInStock code nugget within the line of content. Multiple Lines of Content Razor makes it easy to have multiple lines of content wrapped in an HTML element.  For example, below the inner content of our @if container is wrapped in an HTML <p> element – which will cause Razor to treat it as content: For scenarios where the multiple lines of content are not wrapped by an outer HTML element, you can use multiple @: sequences: Alternatively, Razor also allows you to use a <text> element to explicitly identify content: The <text> tag is an element that is treated specially by Razor. It causes Razor to interpret the inner contents of the <text> block as content, and to not render the containing <text> tag element (meaning only the inner contents of the <text> element will be rendered – the tag itself will not).  This makes it convenient when you want to render multi-line content blocks that are not wrapped by an HTML element.  The <text> element can also optionally be used to denote single-lines of content, if you prefer it to the more concise @: sequence: The above code will render the same output as the @: version we looked at earlier.  Razor will automatically omit the <text> wrapping element from the output and just render the content within it.  Summary Razor enables a clean and concise templating syntax that enables a very fluid coding workflow.  Razor’s smart detection of <tag> elements to identify the beginning of content regions is one of the reasons that the Razor approach works so well with HTML generation scenarios, and it enables you to avoid having to explicitly mark the beginning/ending of content regions in about 95% of if/else and foreach scenarios. Razor’s @: and <text> syntax can then be used for scenarios where you want to avoid using an HTML element within a code container block, and need to more explicitly denote a content region. Hope this helps, Scott P.S. In addition to blogging, I am also now using Twitter for quick updates and to share links. Follow me at: twitter.com/scottgu

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  • Oracle Unveils Oracle Social Relationship Management Suite at Oracle OpenWorld

    - by Richard Lefebvre
    New Service Enables Companies to Listen, Engage, Create, Market and Analyze Interactions across Multiple Social Platforms in Real-Time During his keynote presentation, Oracle CEO Larry Ellison announced the Oracle Social Relationship Management (SRM) Suite.   Oracle Social Relationship Management Suite is an integrated enterprise service that enables companies to listen, engage, create, market, and analyze interactions across multiple social platforms in real-time providing a holistic view of the consumer.   Oracle Social Relationship Management Suite is integrated with Oracle’s enterprise applications, including Oracle Fusion Marketing, Oracle Fusion Sales Catalog, Oracle ATG Web Commerce, and Oracle Enterprise Resource Planning (ERP), allowing organizations to use social to transform their corporate business processes and systems.   Additionally, Oracle Social Relationship Management Suite is integrated with Oracle Platform Services, including Oracle Java Cloud Service and Oracle Database Cloud Service, enabling marketing teams to integrate social with their custom Web pages, landing pages and marketing tools. Unleashing the Power of Social • Providing a holistic view of consumer interactions, Oracle Social Relationship Management Suite includes: Oracle Social Network (OSN): Provides a secure collaboration platform that supports real-time collaboration and networking for users inside and outside the organization. Oracle Social Marketing: Enables marketers to centrally create, publish, moderate, manage, measure and report across multiple social campaigns and platforms. It also helps marketers publish social content, engage fans and customize their brand's look and feel. Oracle Social Engagement & Monitoring Cloud Service: Enables organizations to analyze social media interactions while also empowering customer service and sales teams to effectively engage with customers and prospects. It gives organizations the tools they need to understand customers and take the appropriate actions by monitoring, listening, learning, and responding to signals and trends across the social web. Oracle Social Sites: provides brands and agencies a powerful and rich editing experience that end users can leverage to dynamically develop and launch social sites. Oracle Data and Insights. A service that caters to a growing enterprise need for externally information by providing information, directory and insights about common business entities. Supporting Quote “By fundamentally changing the way organizations connect with their different stakeholders, social is changing the rules of business,” said Thomas Kurian, executive vice president, Oracle Product Development. “With the Oracle Social Relationship Management Suite we are empowering our customers to embrace this change by integrating the tools required to listen, engage, create, market and analyze social interactions into existing applications and services.”

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  • When to do code reviews when doing continuous integration?

    - by SpecialEd
    We are trying to switch to a continuous integration environment but are not sure when to do code reviews. From what I've read of continuous integration, we should be attempting to check in code as often as multiple times a day. I assume, this even means for features that are not yet complete. So the question is, when do we do the code reviews? We can't do it before we check in the code, because that would slow down the process where we will not be able to do daily checkins, let alone multiple checkins per day. Also, if the code we are checking in merely compiles but is not feature complete, doing a code review then is pointless, as most code reviews are best done as the feature is finalized. Does this mean we should do code reviews when a feature is completed, but that unreviewed code will get into the repository?

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  • Can’t use Sub Reports and Shared Datasets in BIDS - Data Retrieval failed for the subreport '###', located at ### Please check the log files

    - by simonsabin
    SQL Server 2008 R2 brings us a great new feature of shared data sets. This allows datasets used by parameters and multiple reports to be defined in one place and used in multiple reports. I’ve been developing a report for SQLBits that required use of sub reports. They all use a shared data set for the agenda items. Initially I was developing in report builder but have now gone back to BIDS. In doing this however all the reports bust reporting the following error Data Retrieval failed for the subreport...(read more)

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  • Multi-Threaded Application vs. Single Threaded Application

    Why would we use a multi threaded application vs. a single threaded application? First we must define multithreading. Multithreading is a feature of an operating system that allows programs to run subcomponents or threads in parallel. Typically most applications only need to use one thread because they do not perform time consuming tasks. The use of multiple threads allows an application to distribute long running tasks so that they can be executed in parallel. This gives the user the perceived appearance that the application is working faster due to the fact that while one thread is waiting on an IO process the remaining tasks can make use of the available CPU. The allows working threads to execute in tandem so that they can be competed sooner. Multithreading Benefits Improved responsiveness — Users usually report improved responsiveness compared to single thread applications. Faster applications — Multiple threads can lead to improved application performance. Prioritization — Threads can be assigned a priority which would allow higher priority tasks to take precedence over lower priority tasks. Single Threading Benefits Programming and debugging —These activities are easier compared to multithreaded applications due to the reduced complexity Less Overhead — Threads add overhead to an application When developing multi-threaded applications, the following must be considered. Deadlocks occur when two threads hold a monitor that the other one requires. In essence each task is blocking the other and both tasks are waiting for the other monitor to be released. This forces an application to hang or deadlock. Resource allocation is used to prevent deadlocks because the system determines if approving the resource request will render the system in an unsafe state. An unsafe state could result in a deadlock. The system only approves requests that will lead to safe states. Thread Synchronization is used when multiple threads use the same instance of an object. The threads accessing the object can then be locked and then synchronized so that each task can interact with the static object on at a time.

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  • Link To Work Item &ndash; Visual Studio extension to link changeset(s) to work item directly from VS history window

    - by Utkarsh Shigihalli
    Originally posted on: http://geekswithblogs.net/onlyutkarsh/archive/2014/08/11/link-to-work-item-ndash-visual-studio-extension-to-link.aspxBy linking work items and other objects, you can track related work, dependencies, and changes made over time. As the following illustration shows, specific link types are used to track specific work items and actions. (– via MSDN) While making a check-in, Visual Studio 2013 provides you a quick way to search and assign a work item via pending changes section in Team Explorer. However, if you forget to assign the work item during your check-in, things really get cumbersome as Visual Studio does not provide an easy way of assigning. For example, you usually have to open the work item and then link the changeset which involves approx. 7-8 mouse clicks. Now, you will really feel the difficulty if you have to assign work item to multiple changesets, you have to repeat the same steps again. Hence, I decided to develop a small Visual Studio extension to perform this action of linking work item to changeset bit easier. How to use the extension? First, download and install the extension from VS Gallery (Supports VS 2013 Professional and above). Once you install, you will see a new "Link To Work Item" menu item when you right click on a changeset in history window. Clicking Link To Work Item menu, will open a new dialog with which you can search for a work item. As you can see in below screenshot, this dialog displays the search result and also the type of the work item. You can also open work item from this dialog by right clicking on the work item and clicking 'Open'. Finally, clicking Save button, will actually link the work item to changeset. One feature which I think helpful, is you can select multiple changesets from history window and assign the work item to all those changesets.  To summarize the features Directly assign work items to changesets from history window Assign work item to multiple changesets Know the type of the work item before assigning. Open the work item from search results It also supports all default Visual Studio themes. Below is a small demo showcasing the working of this extension. Finally, if you like the extension, do not forget to rate and review the extension in VS Gallery. Also, do not hesitate to provide your suggestions, improvements and any issues you may encounter via github.

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  • The Beginner’s Guide To Tabbed Browsing

    - by Chris Hoffman
    Tabs allow you to open multiple web pages in a single browser window without cluttering your desktop. Mastering tabbed browsing can speed up your browsing experience and make multiple web pages easier to manage. Tabbed browsing was once the domain of geeks using alternative browsers, but every popular browser now supports tabbed browsing – even mobile browsers on smartphones and tablets. This article is intended for beginners. If you know someone that doesn’t fully understand tabbed browsing and how awesome it is, feel free to send it to them! How Hackers Can Disguise Malicious Programs With Fake File Extensions Can Dust Actually Damage My Computer? What To Do If You Get a Virus on Your Computer

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  • Best Practices - updated: which domain types should be used to run applications

    - by jsavit
    This post is one of a series of "best practices" notes for Oracle VM Server for SPARC (formerly named Logical Domains). This is an updated and enlarged version of the post on this topic originally posted October 2012. One frequent question "what type of domain should I use to run applications?" There used to be a simple answer: "run applications in guest domains in almost all cases", but now there are more things to consider. Enhancements to Oracle VM Server for SPARC and introduction of systems like the current SPARC servers including the T4 and T5 systems, the Oracle SuperCluster T5-8 and Oracle SuperCluster M6-32 provide scale and performance much higher than the original servers that ran domains. Single-CPU performance, I/O capacity, memory sizes, are much larger now, and far more demanding applications are now being hosted in logical domains. The general advice continues to be "use guest domains in almost all cases", meaning, "use virtual I/O rather than physical I/O", unless there is a specific reason to use the other domain types. The sections below will discuss the criteria for choosing between domain types. Review: division of labor and types of domain Oracle VM Server for SPARC offloads management and I/O functionality from the hypervisor to domains (also called virtual machines), providing a modern alternative to older VM architectures that use a "thick", monolithic hypervisor. This permits a simpler hypervisor design, which enhances reliability, and security. It also reduces single points of failure by assigning responsibilities to multiple system components, further improving reliability and security. Oracle VM Server for SPARC defines the following types of domain, each with their own roles: Control domain - management control point for the server, runs the logical domain daemon and constraints engine, and is used to configure domains and manage resources. The control domain is the first domain to boot on a power-up, is always an I/O domain, and is usually a service domain as well. It doesn't have to be, but there's no reason to not leverage it for virtual I/O services. There is one control domain per T-series system, and one per Physical Domain (PDom) on an M5-32 or M6-32 system. M5 and M6 systems can be physically domained, with logical domains within the physical ones. I/O domain - a domain that has been assigned physical I/O devices. The devices may be one more more PCIe root complexes (in which case the domain is also called a root complex domain). The domain has native access to all the devices on the assigned PCIe buses. The devices can be any device type supported by Solaris on the hardware platform. a SR-IOV (Single-Root I/O Virtualization) function. SR-IOV lets a physical device (also called a physical function) or PF) be subdivided into multiple virtual functions (VFs) which can be individually assigned directly to domains. SR-IOV devices currently can be Ethernet or InfiniBand devices. direct I/O ownership of one or more PCI devices residing in a PCIe bus slot. The domain has direct access to the individual devices An I/O domain has native performance and functionality for the devices it owns, unmediated by any virtualization layer. It may also have virtual devices. Service domain - a domain that provides virtual network and disk devices to guest domains. The services are defined by commands that are run in the control domain. It usually is an I/O domain as well, in order for it to have devices to virtualize and serve out. Guest domain - a domain whose devices are all virtual rather than physical: virtual network and disk devices provided by one or more service domains. In common practice, this is where applications are run. Device considerations Consider the following when choosing between virtual devices and physical devices: Virtual devices provide the best flexibility - they can be dynamically added to and removed from a running domain, and you can have a large number of them up to a per-domain device limit. Virtual devices are compatible with live migration - domains that exclusively have virtual devices can be live migrated between servers supporting domains. On the other hand: Physical devices provide the best performance - in fact, native "bare metal" performance. Virtual devices approach physical device throughput and latency, especially with virtual network devices that can now saturate 10GbE links, but physical devices are still faster. Physical I/O devices do not add load to service domains - all the I/O goes directly from the I/O domain to the device, while virtual I/O goes through service domains, which must be provided sufficient CPU and memory capacity. Physical I/O devices can be other than network and disk - we virtualize network, disk, and serial console, but physical devices can be the wide range of attachable certified devices, including things like tape and CDROM/DVD devices. In some cases the lines are now blurred: virtual devices have better performance than previously: starting with Oracle VM Server for SPARC 3.1 there is near-native virtual network performance. There is more flexibility with physical devices than before: SR-IOV devices can now be dynamically reconfigured on domains. Tradeoffs one used to have to make are now relaxed: you can often have the flexibility of virtual I/O with performance that previously required physical I/O. You can have the performance and isolation of SR-IOV with the ability to dynamically reconfigure it, just like with virtual devices. Typical deployment A service domain is generally also an I/O domain: otherwise it wouldn't have access to physical device "backends" to offer to its clients. Similarly, an I/O domain is also typically a service domain in order to leverage the available PCI buses. Control domains must be I/O domains, because they boot up first on the server and require physical I/O. It's typical for the control domain to also be a service domain too so it doesn't "waste" the I/O resources it uses. A simple configuration consists of a control domain that is also the one I/O and service domain, and some number of guest domains using virtual I/O. In production, customers typically use multiple domains with I/O and service roles to eliminate single points of failure, as described in Availability Best Practices - Avoiding Single Points of Failure . Guest domains have virtual disk and virtual devices provisioned from more than one service domain, so failure of a service domain or I/O path or device does not result in an application outage. This also permits "rolling upgrades" in which service domains are upgraded one at a time while their guests continue to operate without disruption. (It should be noted that resiliency to I/O device failures can also be provided by the single control domain, using multi-path I/O) In this type of deployment, control, I/O, and service domains are used for virtualization infrastructure, while applications run in guest domains. Changing application deployment patterns The above model has been widely and successfully used, but more configuration options are available now. Servers got bigger than the original T2000 class machines with 2 I/O buses, so there is more I/O capacity that can be used for applications. Increased server capacity made it attractive to run more vertically-scaled applications, such as databases, with higher resource requirements than the "light" applications originally seen. This made it attractive to run applications in I/O domains so they could get bare-metal native I/O performance. This is leveraged by the Oracle SuperCluster engineered systems mentioned previously. In those engineered systems, I/O domains are used for high performance applications with native I/O performance for disk and network and optimized access to the Infiniband fabric. Another technical enhancement is Single Root I/O Virtualization (SR-IOV), which make it possible to give domains direct connections and native I/O performance for selected I/O devices. Not all I/O domains own PCI complexes, and there are increasingly more I/O domains that are not service domains. They use their I/O connectivity for performance for their own applications. However, there are some limitations and considerations: at this time, a domain using physical I/O cannot be live-migrated to another server. There is also a need to plan for security and introducing unneeded dependencies: if an I/O domain is also a service domain providing virtual I/O to guests, it has the ability to affect the correct operation of its client guest domains. This is even more relevant for the control domain. where the ldm command must be protected from unauthorized (or even mistaken) use that would affect other domains. As a general rule, running applications in the service domain or the control domain should be avoided. For reference, an excellent guide to secure deployment of domains by Stefan Hinker is at Secure Deployment of Oracle VM Server for SPARC. To recap: Guest domains with virtual I/O still provide the greatest operational flexibility, including features like live migration. They should be considered the default domain type to use unless there is a specific requirement that mandates an I/O domain. I/O domains can be used for applications with the highest performance requirements. Single Root I/O Virtualization (SR-IOV) makes this more attractive by giving direct I/O access to more domains, and by permitting dynamic reconfiguration of SR-IOV devices. Today's larger systems provide multiple PCIe buses - for example, 16 buses on the T5-8 - making it possible to configure multiple I/O domains each owning their own bus. Service domains should in general not be used for applications, because compromised security in the domain, or an outage, can affect domains that depend on it. This concern can be mitigated by providing guests' their virtual I/O from more than one service domain, so interruption of service in one service domain does not cause an application outage. The control domain should in general not be used to run applications, for the same reason. Oracle SuperCluster uses the control domain for applications, but it is an exception. It's not a general purpose environment; it's an engineered system with specifically configured applications and optimization for optimal performance. These are recommended "best practices" based on conversations with a number of Oracle architects. Keep in mind that "one size does not fit all", so you should evaluate these practices in the context of your own requirements. Summary Higher capacity servers that run Oracle VM Server for SPARC are attractive for applications with the most demanding resource requirements. New deployment models permit native I/O performance for demanding applications by running them in I/O domains with direct access to their devices. This is leveraged in SPARC SuperCluster, and can be leveraged in T-series servers to provision high-performance applications running in domains. Carefully planned, this can be used to provide peak performance for critical applications. That said, the improved virtual device performance in Oracle VM Server means that the default choice should still be guest domains with virtual I/O.

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  • 10 Ways to Get a Document into AxCMS.net

    - by Axinom
    Since AxCMS.net 9.1 there is a possibility to upload multiple files simultenously (with a simple Silverlight component). While I was waiting for my files to upload, I started to think about which other methods we currently have in AxCMS.net for uploading documents. I came up with 10 and same evening this article was ready: 10 Ways to Get a Document into AxCMS.net The Classic: Individual Manual Upload Document Creation Box Upload Multiple Files Files from a Remote URL Files from Windows SharePoint Services (WSS) WebDAV ZIP Create Documents Programmatically Apply Auto-Formatting Send the Documents via Email Always choose the most appropriate way to upload your documents into AxCMS.net. Consider size of the documents, how many you have, where to they come from and which other tools you use.  

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  • C#/.NET Little Wonders: A Redux

    - by James Michael Hare
    I gave my Little Wonders presentation to the Topeka Dot Net Users' Group today, so re-posting the links to all the previous posts for them. The Presentation: C#/.NET Little Wonders: A Presentation The Original Trilogy: C#/.NET Five Little Wonders (part 1) C#/.NET Five More Little Wonders (part 2) C#/.NET Five Final Little Wonders (part 3) The Subsequent Sequels: C#/.NET Little Wonders: ToDictionary() and ToList() C#/.NET Little Wonders: DateTime is Packed With Goodies C#/.NET Little Wonders: Fun With Enum Methods C#/.NET Little Wonders: Cross-Calling Constructors C#/.NET Little Wonders: Constraining Generics With Where Clause C#/.NET Little Wonders: Comparer<T>.Default C#/.NET Little Wonders: The Useful (But Overlooked) Sets The Concurrent Wonders: C#/.NET Little Wonders: The Concurrent Collections (1 of 3) - ConcurrentQueue and ConcurrentStack C#/.NET Little Wonders: The Concurrent Collections (2 of 3) - ConcurrentDictionary Tweet   Technorati Tags: .NET,C#,Little Wonders

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  • How to use TCP/IP Nagle algorithm at Apple Push Notification

    - by Mahbubur R Aaman
    From Apple's Developer Library The binary interface employs a plain TCP socket for binary content that is streaming in nature. For optimum performance, you should batch multiple notifications in a single transmission over the interface, either explicitly or using a TCP/IP Nagle algorithm. How to use TCP/IP Nagle algorithm in case Apple's Push Notification? How to batch multiple notification in a single transmission over the interface? Additional # In Apple's Push Notification Urban Airship is a familiar name to send large amount of push notification within several minutes. Does they use TCP/IP Nagle algorithm?

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  • SQL SERVER – Sharing your ETL Resources Across Applications with Ease

    - by pinaldave
    Frequently an organization will find that the same resources are used in multiple ETL applications, for example, the same database, general purpose processing logic, or file system locations.  Creating an easy way to reuse these resources across multiple applications would increase efficiency and reduce errors.  Moreover, not every ETL developer has the same skill set, and it is likely that one developer will be more adept at writing code while another is more comfortable configuring database connections.  Real productivity gains will come when these developers are able to work independently while still making their work available to others assigned to the same project.  These are the benefits of a centralized version control system. Of course, most version control systems could be used to store and serve files, but the real need is to store and serve entire ETL applications so that each developer’s ongoing work can immediately benefit from another developer’s completed work.  In other words, the version control system needs to be tightly integrated with the tools used to develop the ETL application. The following screen shot shows such a tool. Desktop ETL tool that tightly integrates with a central version control system Developers can checkout or commit entire projects or just a single artifact.  Each artifact may be managed independently so if you need to go back to an earlier version of one artifact, changes you may have made to other artifacts are not lost.  By being tightly integrated into the graphical environment used to create and edit the project artifacts, it is extremely easy and straight-forward to move your files to and from the version control system and there is no dependency on another vendor’s version control system.  The built in version control system is optimized for managing the artifacts of ETL applications. It is equally important that the version control system supports all of the actions one typically performs such as rollbacks, locking and unlocking of files, and the ability to resolve conflicts.  Note that this particular ETL tool also has the capability to switch back and forth between multiple version control systems. It also needs to be easy to determine the status of an artifact.  Not just that it has been committed or modified, but when and by whom.  Generally you must query the version control system for this information, but having it displayed within the development environment is more desirable. Who’s ETL tool works in this fashion?  Last month I mentioned the data integration solution offered by expressor software.  The version control features I described in this post are all available in their just released expressor 3.1 Standard Edition through the integration of their expressor Studio development environment with a centralized metadata repository and version control system. You can download their Studio application, which is free, or evaluate the full Standard Edition on your own hardware.  It may be worth your time. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: Pinal Dave, PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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  • Why lock-free data structures just aren't lock-free enough

    - by Alex.Davies
    Today's post will explore why the current ways to communicate between threads don't scale, and show you a possible way to build scalable parallel programming on top of shared memory. The problem with shared memory Soon, we will have dozens, hundreds and then millions of cores in our computers. It's inevitable, because individual cores just can't get much faster. At some point, that's going to mean that we have to rethink our architecture entirely, as millions of cores can't all access a shared memory space efficiently. But millions of cores are still a long way off, and in the meantime we'll see machines with dozens of cores, struggling with shared memory. Alex's tip: The best way for an application to make use of that increasing parallel power is to use a concurrency model like actors, that deals with synchronisation issues for you. Then, the maintainer of the actors framework can find the most efficient way to coordinate access to shared memory to allow your actors to pass messages to each other efficiently. At the moment, NAct uses the .NET thread pool and a few locks to marshal messages. It works well on dual and quad core machines, but it won't scale to more cores. Every time we use a lock, our core performs an atomic memory operation (eg. CAS) on a cell of memory representing the lock, so it's sure that no other core can possibly have that lock. This is very fast when the lock isn't contended, but we need to notify all the other cores, in case they held the cell of memory in a cache. As the number of cores increases, the total cost of a lock increases linearly. A lot of work has been done on "lock-free" data structures, which avoid locks by using atomic memory operations directly. These give fairly dramatic performance improvements, particularly on systems with a few (2 to 4) cores. The .NET 4 concurrent collections in System.Collections.Concurrent are mostly lock-free. However, lock-free data structures still don't scale indefinitely, because any use of an atomic memory operation still involves every core in the system. A sync-free data structure Some concurrent data structures are possible to write in a completely synchronization-free way, without using any atomic memory operations. One useful example is a single producer, single consumer (SPSC) queue. It's easy to write a sync-free fixed size SPSC queue using a circular buffer*. Slightly trickier is a queue that grows as needed. You can use a linked list to represent the queue, but if you leave the nodes to be garbage collected once you're done with them, the GC will need to involve all the cores in collecting the finished nodes. Instead, I've implemented a proof of concept inspired by this intel article which reuses the nodes by putting them in a second queue to send back to the producer. * In all these cases, you need to use memory barriers correctly, but these are local to a core, so don't have the same scalability problems as atomic memory operations. Performance tests I tried benchmarking my SPSC queue against the .NET ConcurrentQueue, and against a standard Queue protected by locks. In some ways, this isn't a fair comparison, because both of these support multiple producers and multiple consumers, but I'll come to that later. I started on my dual-core laptop, running a simple test that had one thread producing 64 bit integers, and another consuming them, to measure the pure overhead of the queue. So, nothing very interesting here. Both concurrent collections perform better than the lock-based one as expected, but there's not a lot to choose between the ConcurrentQueue and my SPSC queue. I was a little disappointed, but then, the .NET Framework team spent a lot longer optimising it than I did. So I dug out a more powerful machine that Red Gate's DBA tools team had been using for testing. It is a 6 core Intel i7 machine with hyperthreading, adding up to 12 logical cores. Now the results get more interesting. As I increased the number of producer-consumer pairs to 6 (to saturate all 12 logical cores), the locking approach was slow, and got even slower, as you'd expect. What I didn't expect to be so clear was the drop-off in performance of the lock-free ConcurrentQueue. I could see the machine only using about 20% of available CPU cycles when it should have been saturated. My interpretation is that as all the cores used atomic memory operations to safely access the queue, they ended up spending most of the time notifying each other about cache lines that need invalidating. The sync-free approach scaled perfectly, despite still working via shared memory, which after all, should still be a bottleneck. I can't quite believe that the results are so clear, so if you can think of any other effects that might cause them, please comment! Obviously, this benchmark isn't realistic because we're only measuring the overhead of the queue. Any real workload, even on a machine with 12 cores, would dwarf the overhead, and there'd be no point worrying about this effect. But would that be true on a machine with 100 cores? Still to be solved. The trouble is, you can't build many concurrent algorithms using only an SPSC queue to communicate. In particular, I can't see a way to build something as general purpose as actors on top of just SPSC queues. Fundamentally, an actor needs to be able to receive messages from multiple other actors, which seems to need an MPSC queue. I've been thinking about ways to build a sync-free MPSC queue out of multiple SPSC queues and some kind of sign-up mechanism. Hopefully I'll have something to tell you about soon, but leave a comment if you have any ideas.

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  • Single Instance of Child Forms in MDI Applications

    - by Akshay Deep Lamba
    In MDI application we can have multiple forms and can work with multiple forms i.e. MDI childs at a time but while developing applications we don't pay attention to the minute details of memory management. Take this as an example, when we develop application say preferably an MDI application, we have multiple child forms inside one parent form. On MDI parent form we would like to have menu strip and tab strip which in turn calls other forms which build the other parts of the application. This also makes our application looks pretty and eye-catching (not much actually). Now on a first go when a user clicks a menu item or a button on a tab strip an application initialize a new instance of a form and shows it to the user inside the MDI parent, if a user again clicks the same button the application creates another new instance for the form and presents it to the user, this will result in the un-necessary usage of the memory. Therefore, if you wish to have your application to prevent generating new instances of the forms then use the below method which will first check if the the form is visible among the list of all the child forms and then compare their types, if the form types matches with the form we are trying to initialize then the form will get activated or we can say it will be bring to front else it will be initialize and set visible to the user in the MDI parent window. The method we are using: private bool CheckForDuplicateForm(Form newForm) { bool bValue = false; foreach (Form frm in this.MdiChildren) { if (frm.GetType() == newForm.GetType()) { frm.Activate(); bValue = true; } } return bValue; } Usage: First we need to initialize the form using the NEW keyword ReportForm ReportForm = new ReportForm(); We can now check if there is another form present in the MDI parent. Here, we will use the above method to check the presence of the form and set the result in a bool variable as our function return bool value. bool frmPresent = CheckForDuplicateForm(Reportfrm); Once the above check is done then depending on the value received from the method we can set our form. if (frmPresent) return; else if (!frmPresent) { Reportfrm.MdiParent = this; Reportfrm.Show(); } In the end this is the code you will have at you menu item or tab strip click: ReportForm Reportfrm = new ReportForm(); bool frmPresent = CheckForDuplicateForm(Reportfrm); if (frmPresent) return; else if (!frmPresent) { Reportfrm.MdiParent = this; Reportfrm.Show(); }

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  • What rules of etiquette should be followed at software conferences?

    - by shemnon
    Whether as an attendee, a speaker, or a vendor I wanted to know what the unspoken rules of etiquette are at software conferences. Other than the blindingly obvious ones (like don't assault the winner of the iPad raffle because you didn't win). What are some of the rules that should be followed, even if you feel they don't need to be said? i.e. what t-shirts are acceptable (like from competing technologies or conferences), playing Wii at vendor booths at Microsoft sponsored conferences, cancelling sessions due to low (one hand) attendance, showering, 'Attendees of Size' spilling over into your seat, talking and eating during sessions or keynotes, etc. Please, one rule per answer, with the summary in bold leading the answer. Post multiple answers if you have multiple rules.

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