Enterprise configuration management

Almost every application requires some form of configuration information. This information can be as simple as a database connection string or as complex as multipart and hierarchical user preference information. How and where to store an application’s configuration data are questions you often face as a developer.

Any large enterprise application has many moving blocks. They all need to be configured for a proper working of the application. As the application size increases or for scalability the same configuration has to be repeated in different applications. For most applications once the configuration has been changed the application needs to be restarted.

Sample Code (create a blank console project, add json.net nuget)

using Newtonsoft.Json;
using Newtonsoft.Json.Linq;
using System.Collections.Generic;
using System.Linq;

namespace CM
{
    // configuration management API, 
    //1. allow clients specify typesafe models for configuations
    //2. Store flat data on server (table) which is easy to edit
    //3. can be extended to have inheritance of values (overrides)
    //4. can be extended to lock / unlock certain property by admins etc.
    
    class Program
    {
        //Sample configuration model
        internal class SampleConfigModal
        {
            public SampleConfigModal()
            {
                Address = new Address();
            }
            public string Name { get; set; }
            public Address Address { get; set; }
            public int Age { get; set; }


        }
        public class Address
        {
            public string Street { get; set; }

        }

        // this is how client api will look like
        static void Main(string[] args)
        {
            // sample client code
            var data = new SampleConfigModal() { Name = "Rajnish", Age = 18, Address = new Address() { Street = "Oxley" } };

            // save Configuration
            SaveConfiguration("app", "section", data);

            //get Configuration
            var data2 = GetConfiguration("app", "section");
        }

        // Client side framework api -> call to rest end point
        private static T GetConfiguration(string appName, string SectionName) where T : new()
        {
            var defaultValue = new T();
            var samplePayload = JsonConvert.SerializeObject(defaultValue);
            var payload = GetConfiguration(appName, SectionName, samplePayload);
            return JsonConvert.DeserializeObject(payload);
        }

        // Client side framework api -> call to rest end point
        private static void SaveConfiguration(string appName, string SectionName, T data)
        {
            var payload = Newtonsoft.Json.JsonConvert.SerializeObject(data);
            SaveConfigurationa(appName, SectionName, payload);
        }


        //---------------------------------------- Server Code -------------------------- 
        //-------------- server has no knowledge of configuration structure or model

        private static Dictionary<string, string> storage;

        private static void SaveConfigurationa(string appName, string SectionName, string payload, string enumForHierarchyLevel = null)
        {
            // transformer
            var section = string.Format("{0}.{1}", appName, SectionName);
            var data = (JObject)JsonConvert.DeserializeObject(payload);
            var keyValueData = Flatten(data, section);

            // check if user has permission for level overrides
            // store with proper overides

            // store the flat list in sql or data 
            //| KEY |           |Value|            |OverrideType| - default,sysadmin,appadmin,groups,user etc
            //app.section.Name, Rajnish
            //app.section.Address.Street, Oxley
            //app.section.Age, 18

            storage = keyValueData;
        }

        private static string GetConfiguration(string appName, string SectionName, string samplePayload)
        {
            var section = string.Format("{0}.{1}", appName, SectionName);
            var data = (JObject)JsonConvert.DeserializeObject(samplePayload);
            var keyValueSample = Flatten(data, section);
            // update data from sql or data store
            // apply property override rules and get value from overrides if exists
            var keyValueData = keyValueSample.Select(x => new KeyValuePair<string, string>(x.Key, storage[x.Key]));

            //read these
            //app.section.Name, Rajnish
            //app.section.Address.Street, Oxley
            //app.section.Age, 18

            UnFlatten(data, section, keyValueData);

            var formatedData = JsonConvert.SerializeObject(data);
            /*
             * {
                  "Name": "Rajnish",
                  "Address": {
                    "Street": "Oxley"
                  },
                  "Age": "18"
                }
             * */
            return formatedData;

        }
        
        // Server side json helper

        private static void UnFlatten(JObject jsonObject, string prefix, IEnumerable<KeyValuePair<string, string>> data)
        {
            foreach (var item in data)
            {
                var keyName = item.Key.Substring(prefix.Length + 1);
                var storageValue = item.Value;
                if (keyName.Contains("."))
                {
                    var keys = keyName.Split('.');
                    var jtoken = (JToken)jsonObject;
                    foreach (var k in keys)
                    {
                        jtoken = jtoken.SelectToken(k);
                    }
                    ((JValue)jtoken).Value = storageValue;
                }
                else
                {
                    jsonObject[keyName] = storageValue;
                }
            }
        }

        private static Dictionary<string, string> Flatten(JObject jsonObject, string prefix)
        {

            IEnumerable jTokens = jsonObject.Descendants().Where(p => p.Count() == 0);
            Dictionary<string, string> results = jTokens.Aggregate(new Dictionary<string, string>(), (properties, jToken) =>
            {
                properties.Add(string.Format("{0}.{1}", prefix, jToken.Path), jToken.ToString());
                return properties;
            });
            return results;
        }
    }
}

Future of web – OWIN & vNext

The ASP.NET Framework has been around for over ten years, and the platform has enabled the development of countless Web sites and services. As Web application development strategies have evolved, the framework has been able to evolve in step with technologies like ASP.NET MVC and ASP.NET Web API.

Web Evolution

  • Classic ASP – At the time, ASP was one of the primary technologies for creating dynamic, data-driven Web sites and applications by interweaving markup and server-side script. The ASP runtime supplied server-side script with a set of objects that abstracted core aspects of the underlying HTTP protocol and Web server and provided access to additional services such session and application state management, cache, etc. While powerful, classic ASP applications became a challenge to manage as they grew in size and complexity. This was largely due to the lack of structure found in in scripting environments coupled with the duplication of code resulting from the interleaving of code and markup
  • ASP.Net – The first version of ASP.NET – also known as “Web Forms” provided a similar design time experience along with a server-side event model for user interface components and a set of infrastructure features (such as ViewState) to create a seamless developer experience between client and server side programming. Web Forms effectively hid the Web’s stateless nature under a stateful event model that was familiar to WinForms developers.
    • ASP.Net MVC – ASP.NET team took several evolutionary steps to enable ASP.NET as a family of pluggable Web components rather than a single framework.One of the early changes was the rise in popularity of the well-known model-view-controller (MVC) design pattern thanks to Web development frameworks like Ruby on Rails. This style of building Web applications gave the developer greater control over her application’s markup while still preserving the separation of markup and business logic, which was one of the initial selling points for ASP.NET.
    • ASP.Net Web API – Another major shift in Web application development was the shift from dynamic, server-generated Web pages to static initial markup with dynamic sections of the page generated from client-side script communicating with backend Web APIs through AJAX requests. This architectural shift helped propel the rise of Web APIs, and the development of the ASP.NET Web API framework. As in the case of ASP.NET MVC, the release of ASP.NET Web API provided another opportunity to evolve ASP.NET further as a more modular framework.

By decoupling framework components from one another and then releasing them on NuGet, frameworks could now iterate more independently and more quickly.A modern Web application generally supports static file serving, dynamic page generation, Web API, and more recently real-time/push notifications. Expecting that each of these services should be run and managed independently was simply not realistic.

What was needed was a single hosting abstraction that would enable a developer to compose an application from a variety of different components and frameworks, and then run that application on a supporting host.

The Open Web Interface for .NET (OWIN)

Inspired by the benefits achieved by Rack in the Ruby community, several members of the .NET community set out to create an abstraction between Web servers and framework components. Two design goals for the OWIN abstraction were that it was simple and that it took the fewest possible dependencies on other framework types. These two goals help ensure:

New components could be more easily developed and consumed.
Applications could be more easily ported between hosts and potentially entire platforms/operating systems.
The resulting abstraction consists of two core elements. The first is the environment dictionary. This data structure is responsible for storing all of the state necessary for processing an HTTP request and response, as well as any relevant server state. The environment dictionary is defined as follows:

IDictionary<string, object>
An OWIN-compatible Web server is responsible for populating the environment dictionary with data such as the body streams and header collections for an HTTP request and response. It is then the responsibility of the application or framework components to populate or update the dictionary with additional values and write to the response body stream.

In asp.net WebApi v2, the OWIN pipeline becomes the default. It is eventually going to be the standard pipeline under any asp.net project.

Without OWIN, the asp.net bits are coupled to the way IIS communicates with the application. OWIN abstracts web servers and framework components. That means that your application code will now be aware of the OWIN interface, but not of the webserver that is serving the request.

In return, applications can be more easily ported between hosts and potentially entire platforms/operating systems. For example, the ability to host an application in a console or any process allows Mono to host it without efforts…

The second aspect is that it works as a pipeline.

You can plug any middlewares (and as many as you want) between the webserver and your application.
This allows for more modular solutions. You can develop redistributable middlewares that can impact the request/response coming to/from your application, but keep these modules separated from the application code.

To persuade yourself of the benefits of this modular approach, take a look at the nuget packages available for OWIN : http://www.nuget.org/packages?q=owin

A lot of these packages were previously core asp.net functionality, and have been extracted as middleware.
For example, adding support to login using various OAuth providers becomes an infrastructure concern (a middleware) and does not need to be part of your application code anymore :

Learn more about OWIN

Project Katana

Whereas both the OWIN specification and Owin.dll are community owned and community run open source efforts, the Katana project represents the set of OWIN components that, while still open source, are built and released by Microsoft. These components include both infrastructure components, such as hosts and servers, as well as functional components, such as authentication components and bindings to frameworks such as SignalR and ASP.NET Web API. The project has the following three high level goals:

Portable – Components should be able to be easily substituted for new components as they become available. This includes all types of components, from the framework to the server and host. The implication of this goal is that third party frameworks can seamlessly run on Microsoft servers while Microsoft frameworks can potentially run on third party servers and hosts.
Modular/flexible – Unlike many frameworks which include a myriad of features that are turned on by default, Katana project components should be small and focused, giving control over to the application developer in determining which components to use in her application.
Lightweight/performant/scalable – By breaking the traditional notion of a framework into a set of small, focused components which are added explicitly by the application developer, a resulting Katana application can consume fewer computing resources, and as a result, handle more load, than with other types of servers and frameworks. As the requirements of the application demand more features from the underlying infrastructure, those can be added to the OWIN pipeline, but that should be an explicit decision on the part of the application developer. Additionally, the substitutability of lower level components means that as they become available, new high performance servers can seamlessly be introduced to improve the performance of OWIN applications without breaking those applications.

And Now.. 

ASP.Net 5 – vNext 

The next generation of ASP.net

ASP.NET 5 is a significant redesign of ASP.NET.

ASP.NET 5 includes the following features:

  • New flexible and cross-platform runtime
  • ASP.NET MVC and Web API have been unified into a single programming model
  • New modular HTTP request pipeline
  • Cloud-ready environment configuration
  • Modular design, depedency injection and lot more.
  • Unified programming model that combines MVC, Web API,SignalR and Web Pages
  • Ability to see changes without re-building the project
  • Side-by-side versioning of the .NET Framework
  • Ability to self-host or host on IIS
  • New tools in Visual Studio 2015
  • Open source in GitHub
  • Can run on Mono, on Mac and Linux

Learn more : http://www.asp.net/vnext

 

Asp.Net MVC flavours

The main purpose of the MVC (Model, View and Controller) architecture is to make separation of the business layer (logic) and the application layer (data)  from the presentation layer to the user. Model-View-Controller is a software pattern for achieving isolation between different application components. Its always desirable for software applications (especially web-based applications) that there must be clear separation between business logic and the user interface. A model represents the state of a particular aspect of the application. A controller handles interactions and updates the model to reflect a change in state of the application, and then passes information to the view. A view accepts necessary information from the controller and renders a user interface to display that information. Over past few years many version of ASP.Net MVC were release moving towards more and more mature framework for web development.Below is brief comparison of features release in each version

MVC 5 – October 2013

  • Bootstrap replaced the default MVC template.
  • ASP.NET Identity for authentication and identity management.
  • Authentication Filters for authenticating user by custom or third-party authentication provider.
  • With the help of Filter overrides, we can now override filters on a method or controller.
  • Attribute Routing is now integrated into MVC 5

MVC 4 – August 2012

  • ASP.NET Web API, a framework that simplifies the creation of HTTP services and serving a wide range of clients.
  • Follow to create your first ASP.NET Web API service
  • Adaptive rendering and other look-n-feel improvements to Default Project Templates.
  • A truly Empty Project Template.
  • MVC4 also uses Razor View Engine as a default view engine with some new features like condition attribute and ‘Tilde slash’
  • Based on jQuery Mobile, new Mobile Project Template introduced.
  • Support for adding controller to other project folders also.
  • Task Support for Asynchronous Controllers.
  • Controlling Bundling and Minification through web.config.
  • Support for OAuth and OpenID logins using DotNetOpenAuth library.
  • Support for Windows Azure SDK 1.6 and new releases.
  • MVC4 provides better support for Jquery like Jquery Mobile
  • Client side validation, Jquery validation and enhanced support for asynchronous methods
  • Supports many new features for mobile apps and also provides new mobile project template and default templates are refreshed and modernized

MVC 3 – January 2011

  • New Project Templates having support for HTML 5 and CSS 3.
  • Improved Model validation.
  • Razor View Engine (.cshtml for c# and .vbhtml for Visual Basic) introduced apart from Web Forms view engine (.aspx)
  • Having support for Multiple View Engines i.e. Web Forms view engine, Razor or open source.
  • Controller improvements like ViewBag property and ActionResults Types etc.
  • Unobtrusive JavaScript approach, Ajax and Client side Validation, Jquery Validation and JSON binding support
  • Chart, WebGrid, Crypto,WebImage, WebMail Controls
  • Improved Dependency Injection with new IDependencyResolver.It provides powerful hooks with Dependency Injection and Global Action Filters
  • Partial page output caching.
  • TempData, ViewData ,ViewBag
  • Supports not only Master Page but also Layout Page

MVC 2 – March 2010

  • MVC 2 uses only Web Forms view engine (.aspx) as a default View Engine.
  • (HTML Syntax) Web Forms view engine syntax: <%=Html code %>
  • TempData, ViewData
  • Jquery support is Good
  • Supports only Master Page
  • Client-side Validation and Asynchronous controllers
  • support controllers to process requests asynchronously
  • Supports validations using the RangeAttribute, RequiredAttribute, StringLengthAttribute, and RegexAttribute attributes.

MVC 1 – March 2009

MVC CTP – December 2007 

* Notes

  • View Engine is responsible for rendering of the HTML code from your views to the browser.
  • In ViewData, dictionary of objects are accessible via strings as keys
  • ViewBag was added in the C# 4.0 which uses the dynamic feature that allows to add properties of an object dynamically . We can say that ViewBag = ViewData + dynamic feature around the ViewData dictionary

Authorization Vs Authentication

Authentication

Authentication is the mechanism whereby systems may securely identify their users. Authentication systems provide an answers to the questions:

  • Who is the user?
  • Is the user really who he/she represents himself to be?

Authentication is the process of obtaining identification credentials from a user ( such as name and password ), and validating those credentials against some authority. If the credentials are valid, the entity that submitted the credentials is considered an authenticated identity.

ASP.NET implements authentication through authentication providers, the modules that contain the code to authenticate the requestor’s credentials. Following are built in ASP.Net authentication providers.

  • Windows Authentication Provider
  • Forms Authentication Provider
  • Passport Authentication Provider

Authorization

Authorization, by contrast, is the mechanism by which a system determines what level of access a particular authenticated user should have to secured resources controlled by the system.

Authorization systems provide answers to the questions:

  • Is user X authorized to access resource R?
  • Is user X authorized to perform operation P?
  • Is user X authorized to perform operation P on resource R?

Once an identity has been authenticated, the authorization process determines whether that identity has access to a given resource.

ASP.NET implements authorization through authorization providers, the modules that contain the code to authorize access to a given resource. ASP.NET includes the following authorization modules.

  • File Authorization Provider
  • URL authorization

Authentication and authorization are somewhat tightly-coupled mechanisms – authorization systems depend on secure authentication systems to ensure that users are who they claim to be and thus prevent unauthorized users from gaining access to secured resources.

ASP.NET Membership (Providers)

ASP.NET Roles (Providers)

 

Silverlight WebSockets – Duplex Communication

A duplex communication system is a system composed of two connected parties or devices that can communicate with one another in both directions. Duplex communication is required when you need to send some data in the reverse direction i.e. from Server to client. For scenario purpose assume that something happens on server (some event is received from source) and message from server should be sent to connected clients. Off-course the solution should be highly scalable with low latency client and server.

Let’s talk about silverlight client in our scenario

 There could be couple of options with silverlight client demonstrated by Gill Cleeren In series of article “The duplex story: looking at duplex communication in Silverlight 4

Silverlight 4.0 now supports 3 different types of duplex communications

  • HTTP Polling Duplex: Duplex requires that the server can itself initiate communication, which is not supported by HTTP, HTTP Polling duplex (HTTP long polling, or Comet-style) protocol allows us to do bi-directional communication over HTTP. What happens behind the scenes is the following:
    • The Silverlight client initiates the communication by sending an initial request to the service.
    • After the client is registered with the service, it continuously starts polling the service for updates.
    • Whenever the service has new messages to send to the client, they are queued up until a new poll arrives from the client.

The HTTP Polling Duplex is therefore not real duplexing: it creates an illusion of duplex communication by polling (at network layer) so frequently that it looks as if the messages are pushed from the service to the client. If you still want to use this method here is the link for you to tune performance of http polling duplex.

  • Sockets: Socket is implemented through the use of a TcpListener, Being pure TCP endpoints, sockets are fast and true duplex communicators. However sockets in Silverlight can only work over ports between 4502 and 4534 making it unsuitable for duplex communication over the internet. Secondly you need to build policy server to provide clientaccesspolicy.xml for sockets.Note that Silverlight 4 also allows that the policy calls are made over HTTP.
  • net.tcp binding: this entirely new binding, added in Silverlight 4, also supports duplex communication. net.tcp combines advantages of both polling duplex and sockets. Its programming model is, just like polling duplex, based on WCF. That means that we can take advantage of automatic proxy generation inside Visual Studio.
  • Poll based communication: Not scalable, out of scope.

So what’s next?

 HTML 5 – WebSockets

Web socket protocol or WebSockets are “TCP for the Web,” a next-generation bidirectional communication technology for web applications being standardized in part of Web Applications 1.0.

The Web Sockets API enables web applications to handle bidirectional communications with server-side process in a straightforward way. Once you get a Web Socket connection, you can send data from browser to server by calling a send() method, and receive data from server to browser by an onmessage event handler. The protocol is not raw TCP because it needs to provide the browser’s “same-origin” security model. It’s also not HTTP because web socket traffic differers from HTTP’s request-response model. you do need a new server implementation to communicate with web sockets .

web socket prototype is out now at http://html5labs.interoperabilitybridges.com/prototypes/available-for-download/websockets/html5protos_Download or websocket msi from here

 for more information see : http://tomasz.janczuk.org/2010/12/websockets-wcf-service-silverlight-and.html

Please also find the published websocket transport binding (Incomplete project)  here which i was trying to build using custom duplex WCF channel.