NoSQL Databases

What is NoSQL?

NoSQL database management systems are useful when working with a huge quantity of data and the data's nature does not require a relational model for the data structure. The data could be structured, but it is of minimal importance and what really matters is the ability to store and retrieve great quantities of data, and not the relationships between the elements. For example, to store millions of key-value pairs in one or a few associative arrays or to store millions of data records. This is particularly useful for statistical or real-time analyses for growing list of elements (such as Twitter posts or the Internet server logs from a big group of users).

Advantages of NoSQL databases:

• Horizontally Scalable
• Schema-less
• Cloud Model

NoSQL Categories:

The current NoSQL world fits into 4 basic categories -

1. Key-values Stores are based primarily on Amazon's Dynamo Paper which was written in 2007. The main idea is the existence of a hash table where there is a unique key and a pointer to a particular item of data. These mappings are usually accompanied by cache mechanisms to maximize performance.
2. Column Family Stores were created to store and process very large amounts of data distributed over many machines. There are still keys but they point to multiple columns. In the case of BigTable (Google's Column Family NoSQL model), rows are identified by a row key with the data sorted and stored by this key. The columns are arranged by column family.
3. Document Databases were inspired by Lotus Notes and are similar to key-value stores. The model is basically versioned documents that are collections of other key-value collections. The semi-structured documents are stored in formats like JSON.
4. Graph Databases are built with nodes, relationships between notes and the properties of nodes. Instead of tables of rows and columns and the rigid structure of SQL, a flexible graph model is used which can scale across many machines.

Major NoSQL Players

The major players in NoSQL have emerged primarily because of the organizations that have adopted them. Some of the largest NoSQL technologies include:

1. CouchDB: CouchDB is a database that uses JSON for documents, JavaScript for MapReduce queries,and regular HTTP for an API
2. MongoDB: MongoDB(from "humongous") is a scalable, high-performance, open source NoSQL database. Written in C++
3. SimpleDB: SimpleDB is a highly available and flexible non-relational data store that offloads the work of database administration. Developers simply store and query data items via web services requests and Amazon SimpleDB does the rest.
4. BigTable: BigTable is Google's proprietary column oriented database. Google allows the use of BigTable but only for the Google App Engine.
5. Dynamo: Dynamo was created by Amazon.com and is the most prominent Key-Value NoSQL database. Amazon was in need of a highly scalable distributed platform for their e-commerce businesses so they developed Dynamo. Amazon S3 uses Dynamo as the storage mechanism.
6. Cassandra: Cassandra was open sourced by Facebook and is a column oriented NoSQL database.
7. Neo4J: Neo4j is an open source graph database.

ref:

NoSQL Databases - http://en.wikipedia.org/wiki/NoSQL

Document Oriented Databases -  http://en.wikipedia.org/wiki/Document-oriented_database 

NoSQL and Document Oriented Databases -  http://ruby.about.com/od/nosqldatabases/a/nosql1.htm 

NoSQL Databases - http://newtech.about.com/od/databasemanagement/a/Nosql.htm

10 things you should know about NoSQL databases - http://www.techrepublic.com/blog/10things/10-things-you-should-know-about-nosql-databases/1772

What is a document database - http://dssresources.com/faq/index.php?action=artikel&id=236 

Top NoSQL Databases - http://opensourcebyte.blogspot.com/2012/01/top-nosql-databases.html

Mobile Application Development

Mobile Application Development is the process by which application software is developed for low-power handheld devices, such as personal digital assistants, enterprise digital assistants or mobile phones. These applications are pre-installed on phones during manufacture, can be downloaded by customers from various mobile software distribution platforms, or web applications delivered over HTTP which use server-side or client-side processing (e.g. JavaScript) to provide an "application-like" experience within a Web browser.

Execution Environments:
Android, iOS, BlackBerry, HP webOS, Symbian OS, Bada from Samsung, and Windows Mobile support typical application binaries as found on personal computers with code which executes in the native machine format of the processor (the ARM architecture is a dominant design used on many current models). Windows Mobile can also be compiled to x86 executables for debugging on a PC without a processor emulator, and also supports the Portable Executable (PE) format associated with the .NET Framework. Windows Mobile, Android, HP webOS and iOS offer free SDKs and integrated development environments to developers.

Mobile Web apps vs. Mobile Native apps: 
Is it better to deploy web apps or native apps? The answer is: both. Thanks to the recent improvements in the browsers of smartphones and tablet computers, web apps on mobile devices work well. Native apps do provide more access to native hardware features at this time. However, the decision isn't only about which is better. Users who are test-driving new solutions are hesitant to install a native application. Some are simply not ready to commit to our solution. They want to test-drive it before they install a native application. And native apps do require some maintenance and updates. By supporting both web apps and native apps, we can maintain a zero-install policy for our innovation. Also, users cycle through more devices than you might expect. When they get a new device, they test-drive it first with the web app before they install a native app. There are always trade-offs among function, design, and time to deploy.

Popular cross platform mobile frameworks:
Rhodes - is a Ruby-based framework that allows you to build your application a very similiar way to the way you’d build a Ruby Application. It offers support for iPhone, Android, BlackBerry, Windows Mobile, and Windows Phone 7.

Titanium Mobile by Appcelerator - Take your hard won web skills and turn them into mobile app development skills. It boasts support for letting you use JavaScript, HTML, and CSS. It features a JavaScript API that provides access to native UI elements. The magic in Titanium happens during runtime in it’s bridge between the JavaScript and the native SDK. The bridge reads your JavaScript and uses it to build views that have the same features and performance as an application written in that native language. Currently, Titanium Mobile supports iPhone and Android (with BlackBerry support in beta mode for paid subscribers).

MoSync - Takes a different approach to cross-platform mobile development in that it doesn’t use web technologies at all. It has it’s own SDK built with C/C++ that gives the developer access to many of the standard C libraries, graphic and media classes, the networking layer, native UI elements and more. At this point, it offers support for the Java ME environment, Windows Mobile, Symbian S60, Android, iOS, and Moblin/MeeGo. BlackBerry and Windows 7 support is coming soon. Just like RhoMobile, MoSync is more enterprise focused and you won’t find a lot applications in the app stores built with MoSync.

PhoneGap - Wraps a mobile web application exposing access to device features through a consistent API; it uses JavaScript as an abstraction layer between your mobile Web app and the device. PhoneGap currently supports iOS, Android, BlackBerry, webOS, Windows Mobile, Symbian, and Bada.

Other frameworks - Mono, Bada ...

ref:
Mobile Application Development - http://en.wikipedia.org/wiki/Mobile_application_development

Mobile Development Resources(Blogs/...) - http://www.shawngrimes.me/2012/03/mobile-development-overview/

How to approach mobile development today - http://blogs.msdn.com/b/obloch/archive/2012/03/08/how-to-approach-mobile-development-today.aspx 

Apple Roadmap to start developing iOS Apps  - https://developer.apple.com/library/ios/#referencelibrary/GettingStarted/RoadMapiOS/Introduction/Introduction.html

Becoming iOS Developer(by Josh Smith) - http://joshsmithonwpf.wordpress.com/2012/02/19/becoming-an-ios-developer/

Getting Started with the Mobile SDK for iOS - http://wiki.developerforce.com/

OS X Developer Library - https://developer.apple.com/library/mac/#documentation/General/Conceptual/ConcurrencyProgrammingGuide/Introduction/Introduction.html#//apple_ref/doc/uid/TP40008091-CH1-SW1

Beginner's guide to Mobile Web Development - http://mobiforge.com/starting/story/a-beginners-guide-mobile-web-development

Mobile Development SDKs compared - http://www.softwaresweden.com/2010/02/16/mobile-development-sdks-compared-mosync-phonegap-and-appwhirl/

Cross Platform Mobile Development Frameworks - http://floatlearning.com/2011/07/which-cross-platform-framework-is-right-for-me/

5 Cross-Platform Mobile Development Tools You Should Try - http://mashable.com/2010/08/11/cross-platform-mobile-development-tools/

Identify Memory Leaks and Memory Corruption in VC++ Application

Identify Memory Corruption: 

1.gflags (part of Windows Debugging Tools) tool can be used to find Memory Corruption issues. All we need is to download Windows Debugging tools(which comes with both gflags.exe & WinDbg).

ref: http://blogs.msdn.com/b/webdav_101/archive/2010/06/22/detecting-heap-corruption-using-gflags-and-dumps.aspx

Identify Memory Leaks: 
1. Visual Leak Detector tool is a free, robust, open-source memory leak detection system for Visual C++. After installing it, you just need to tell Visual C++ where to find the included header(vld.h) and library file(vld.lib). 
ref: http://vld.codeplex.com/, http://www.codeproject.com/Articles/9815/Visual-Leak-Detector-Enhanced-Memory-Leak-Detectio

2. Debugdiag is a Debug Diagnostic Too designed to assist in troubleshooting issues such as hangs, slow performance, memory leaks or fragmentation, and crashes in any user-mode process. The tool includes additional debugging scripts focused on Internet Information Services (IIS) applications, SharePoint, web data access components, COM+ and related Microsoft technologies.
ref: http://blogs.technet.com/b/stefan_gossner/archive/2011/07/18/finally-debugdiag-1-2-available-on-microsoft-download-center.aspx

3. _CrtSetDbgFlag() API from C Run-Time Library will display memory leaks in the Debug output window. 
ref: http://msdn.microsoft.com/en-us/library/e5ewb1h3(v=vs.80).aspx

4. Application Verifier tool can be used for identifying errors caused by heap corruption, incorrect handle and critical section usage. It may not work for a Application which is mix of UnManaged & Managed code.
ref: http://msdn.microsoft.com/en-us/library/ms220948.aspx


Other tools include Devpartner studio BoundsChecker, Rational Purify, SmartBear AQTimer, SoftwareVerify C++ Performance Validator ...

Performance Profiling:
Intel offers an array of application performance tools that are optimized to take advantage of the Intel® processors. You can employ these tools for developing the most efficient programs without having to write assembly code. These performance tools(Intel VTune Amplifier) will help you analyze your application and find and resolve the problem areas. The following sections summarize each of the recommended Intel® performance tools.
ref: http://www.ncsa.illinois.edu/UserInfo/Resources/Software/Intel/Compilers/9.0/main_cls/mergedProjects/optaps_cls/common/optaps_time_perf.htm

Developing Apps using HTML5

HTML5 is an umbrella term describing a set of HTML, CSS and JavaScript specifications designed to enable developers to build the next generation of Web sites and applications. What’s notable in that definition is its three parts: HTML, CSS and JavaScript. They define how developers use improved markup, richer style capabilities and new JavaScript APIs to make the most of new Web development features. 


ie, HTML5 = HTML + CSS + JavaScript

WebSockets:


The WebSocket specification defines an API establishing "socket" connections between a web browser and a server. In plain words: There is an persistent connection between the client and the server and both parties can start sending data at any time.

Defined in the Communications section of the HTML5 specification, HTML5 Web Sockets represents the next evolution of web communications - a full-duplex, bidirectional communications channel that operates through a single socket over the Web. HTML5 Web Sockets provides a true standard that you can use to build scalable, real-time web applications. In addition, since it provides a socket that is native to the browser, it eliminates many of the problems Comet solutions are prone to. Web Sockets removes the overhead and dramatically reduces complexity.


Adopting HTML5 in your Applications:


Adopting HTML5, rather than being a wholesale choice, is about making a technology-by technology evaluation and determining which technologies are right for your application. For each HTML5 technology you evaluate, look at (at least) the following factors when deciding whether that technology is ready for you to adopt:

1. How widely implemented across all major browsers is the technology?
2. How would you adopt this technology and “polyfill” support for browsers that don’t support a given feature?

The first factor is the most important, and when combined with an understanding of the browsers commonly used by visitors to your site, should give you a clear picture of which subset of the 100-plus specifications is worth evaluating further. That subset should consist of a set of stable specifications you can reliably adopt today for your users.

However, even with that stable set of HTML5 technologies, you shouldn’t ignore your users who haven’t moved to a newer browser. If you’re heavily involved in the day-to-day development for your site, you no doubt have some rough idea of the percentages of users visiting your site with a given browser. For most of us, it would be easy to look at the percentage of users visiting with an older browser and come to the conclusion that adopting any HTML5 technologies would negatively impact those users. Luckily there’s “polyfilling” to save us from waiting until some foggy date in the future to adopt HTML5.

Paul Irish (a developer on the jQuery and Modernizr projects) defines a polyfill as “… a shim that mimics a future API, providing fallback functionality to older browsers.” A polyfill is like spackle for your Web sites; it’s a way to determine if a given HTML5 feature is available to the user currently browsing your site, and to provide either a shim that “fills in” that support or a course of graceful degradation that enables your site to still function fully.

The most popular library associated with polyfilling is Modernizr, the JavaScript library I mentioned earlier. Modernizr provides some basic polyfills for semantic markup, feature detection for major HTML5 technologies and support for conditional CSS based on supported features. As noted, Modernizr will be the subject of an upcoming article; it will also feature prominently (along with many other polyfilling libraries) throughout this series. To learn more, download Modernizr at modernizr.com. 


Windows 8 Metro Style Apps:


Windows 8  Metro style apps have a brand new look and feel, run on a variety of devices, and you sell them on the Windows Store.Metro style apps can be developed using HTML5, Cascading Style Sheets, Level 3 (CSS3), and JavaScript.

Windows provides two sets of APIs for building Metro style apps: 

1. WinRT(Windows Runtime) 
2. Windows Library for JavaScript

Windows Runtime: These JavaScript, C#, Visual Basic, and C++ APIs provide access to all core platform features. The namespaces are exposed using API metadata format(Windows.winmd) similar to that used by the .NET framework (Ecma-335).

Windows Library for JavaScript: These JavaScript APIs provide controls, CSS styles, and helper functions that help you write object-oriented code. The WinJS namespace covers functionality that is similar to the Windows.UI.XAML namespaces in the Windows Runtime. When you reference these JavaScript files in your app, you must add base.js first, then ui.js

Metro style apps only: Windows Metro style app APIs that are expressed as HTML or XAML elements are supported only in Metro style apps, and are not supported in desktop apps or Metro style enabled desktop browsers.

ref:

Building HTML5 Applications - http://msdn.microsoft.com/en-us/magazine/ee532098.aspx?sdmr=Brandon%20Satrom&sdmi=authors


Creating Mobile Web Applications with HTML 5 - 
http://www.ibm.com/developerworks/xml/library/x-html5mobile1/index.html
http://www.ibm.com/developerworks/xml/library/x-html5mobile2/index.html
http://www.ibm.com/developerworks/xml/library/x-html5mobile3/index.html
http://www.ibm.com/developerworks/xml/library/x-html5mobile4/index.html
http://www.ibm.com/developerworks/xml/library/x-html5mobile5/index.html


Building Apps with HTML5: What You Need to Know - http://msdn.microsoft.com/en-us/magazine/hh335062.aspx

Creating Media Apps for Windows Phone - http://msdn.microsoft.com/en-us/magazine/hh975340.aspx

Develop HTML5 applications using Apache Cordova - http://msdn.microsoft.com/en-us/magazine/hh975345.aspx 


Why WebSockets - http://www.websocket.org/quantum.html


Modernizr: an open-source JavaScript library that helps you build the next generation of HTML5 and CSS3-powered websites - http://modernizr.com/

Microsoft ScriptJunikie Website for HTML5 sample code - http://msdn.microsoft.com/en-us/magazine/ee729207.aspx

Using HTML5 to Create Mobile Experiences - http://msdn.microsoft.com/en-us/magazine/hh975346.aspx

Developing an Advanced Windows Phone 7.5 App that Connects to the Cloud - http://msdn.microsoft.com/en-us/library/gg490765

Transforming a Android App into Windows Phone App - http://msdn.microsoft.com/en-us/magazine/hh965662.aspx

Develop Metro style apps using Visual Studio 2012 RC - http://msdn.microsoft.com/en-us/library/windows/apps/br211384.aspx

Apache Incubator -  http://en.wikipedia.org/wiki/Apache_Incubator 

WinRT(Windows Runtime)

WinRT is the new Windows Runtime (Windows 8 or above required) that expose Operating System functionality in an object oriented fashion. WinRT is Microsoft's 2011 programming model that forms the backbone of the new Metro-style apps (also known as Immersive) in their new Windows 8 operating system. WinRT supports development in C++ (usually with Component Extensions, C++/CX) and the managed languages C# and VB.NET, as well as JavaScript. Programs can be written using Windows Runtime that will run on both the Intel and ARM editions of Windows 8 without modification. WinRT is essentially a COM-based API, although relying on an enhanced COM. Because of its COM-like basis, WinRT allows relatively easy interfacing from multiple languages, just as COM does, but it's essentially an unmanaged, native API. It's Microsoft's implementation of the XAML-based UI system. Unlike WPF which was exposed only to the .NET world and Silverlight which was only exposed to the browser, this new implementation is available to C++ developers, HTML/Javascript developers and also .NET developers.

WinRT is a new set of APIs that have the following properties:

• It implements the new Metro look.
• Has a simple UI programming model for Windows developers (You do not need to learn Win32, what an HDC, WndProc or LPARAM is).
• It exposes the WPF/Silverlight XAML UI model to developers.
• The APIs are all designed to be asynchronous.
• It is a sandboxed API, designed for creating self-contained, AppStore-ready applications. You wont get everything you want to create for example Backup Software or Hard Disk Partitioning software.
• The API definitions is exposed in the ECMA 335 metadata format (the same one that .NET uses, you can find those as ".winmd" files).

WinRT wraps both the new UI system as well as old Win32 APIs and it happens that this implementation is based on top of COM.

ref:

Asynchronous Programming in C++ Using PPL - http://msdn.microsoft.com/en-us/magazine/hh781007.aspx

Windows Runtime - http://en.wikipedia.org/wiki/Windows_Runtime

WinRT Overview - http://winrt.codeplex.com/

Demystifying WinRT - http://tirania.org/blog/archive/2011/Sep-15.html

Parallel Patterns Library (PPL) - http://msdn.microsoft.com/en-us/library/dd492418.aspx

Browser default TIMEOUT Settings

TIMEOUTs are Browser dependent ...

HTTP Error 408 Request timeout

The Web server (running the Web site) thinks that there has been too long an interval of time between 1) the establishment of an IP connection (socket) between the client (e.g. your Web browser ) and the server and 2) the receipt of any data on that socket, so the server has dropped the connection. The socket connection has actually been lost - the Web server has 'timed out' on that particular socket connection. The request from the client must be repeated - in a timely manner.

408 errors in the HTTP cycle:

Any client (e.g. your Web browser) goes through the following cycle:

• Obtain an IP address from the IP name of the site (the site URL without the leading 'http://'). This lookup (conversion of IP name to IP address) is provided by domain name servers (DNSs).
• Open an IP socket connection to that IP address.
• Write an HTTP data stream through that socket.
• Receive an HTTP data stream back from the Web server in response. This data stream contains status codes whose values are determined by the HTTP protocol. Parse this data stream for status codes and other useful information.
• This error occurs in the final step above when the client receives an HTTP status code that it recognizes as '408'. (Last updated: March 2012).

Internet Explorer:


Internet Explorer imposes a time-out limit for the server to return data. By default, the time-out limit is as follows:

Internet Explorer 4.0 and Internet Explorer 4.01	5 minutes
Internet Explorer 5.x and Internet Explorer 6.x	60 minutes
Internet Explorer 7 and Internet Explorer 8	60 minutes

When the server is experiencing a problem, Internet Explorer does not wait endlessly for the server to return data. 


Applications that use the WinINet API directly will experience the following ReceiveTimeout values:

WinINet.dll version 4.x	5 minutes
WinINet.dll versions 5.x and 6.x	60 minutes
WinINet.dll versions 7.x and 8.x	30 seconds

You can locate the version of WinINet.dll in the %windir%\system32 directory.


How to change the IE ReceiveTimeout limit via Windows Registry:

• Start Registry Editor (Click Start, click Run, type regedit, and then click OK).
• Locate the following subkey:
• HKEY_CURRENT_USER\SOFTWARE\Microsoft\Windows\CurrentVersion\Internet Settings
• In this subkey, add a ReceiveTimeout DWORD entry that has the appropriate timeout value in milliseconds.

Firefox:


Firefox user preferences can be viewed and modified by typing about:config in the Browser AddressBar.


ref:


Default timeout settings for Internet Explorer - http://support.microsoft.com/kb/181050, http://support.microsoft.com/kb/813827


Http Keep-Alive Timeouts of the Browsers - http://blog.fastmail.fm/2011/06/28/http-keep-alive-connection-timeouts/