Microservices

Intro

Back in the day most systems started as a monolithic system, which basically means the entire application exists in a single code base and is deployed and, importantly, scaled as a single unit.

A monolithic application puts all its functionality into a single process… and scales by replicating the monolith on multiple servers. A monolithic application is harder to scale, as one small change must be deployed across all processes.

What are microservices ?

According to wikipedia, microservices are a software architecture style in which complex applications are composed of small, independent processes communicating with each other using language-agnostic APIs. These services are small, highly decoupled and focus on doing a small task, facilitating a modular approach to system-building.

Software developer advocates James Lewis and Martin Fowler gave the best definition we could find for this increasingly popular architectural pattern:

“The microservice architectural style is an approach to developing a single application as a suite of small services, each running in its own process and communicating with lightweight mechanisms, often an HTTP resource API. These services are built around business capabilities and independently deployable by fully automated deployment machinery. There is a bare minimum of centralized management of these services, which may be written in different programming languages and use different data storage technologies.”

A microservices architecture puts each element of functionality into a separate service…and scales by distributing these services across servers, replicating as needed.

Characteristics of microservices

  • Small with a single responsibility
  • Each application does one thing
  • Small enough to fit your head – If a class is bigger than by head then it is too big
  • Small enough that you can throw them away – Rewrite over Maintain
  • Status aware and Auto scaling – multiple consumers (Competing Consumers pattern example
  • WatchDog process to monitor app-status (expose metrics about itself eg: queue dept) auto-scale to meet throughput requirements.
  • A single capability composed of a small number of activities and exposing a uniform interface (REST)
  • Each is entirely decoupled from it’s clients, scalable, testable and deployable individually.

How does a microservice outshine a monolith?

  1. It makes your app more scalable with smaller teams.
  2. Enables modularity and is more open to change in general.
  3. Uses a smaller codebase.

What are microservice architecture’s limitations?

  1. It can cause communication problems among different parts of the app and within your team.
  2. It requires increased effort later on to catalog, test, and fix incompatibilities.
  3. You should still build the monolith before building the microservices on top of it.

The Revealing Module Pattern

This pattern is the same concept as the module pattern in that it focuses on public & private methods. The only difference is that the revealing module pattern was engineered as a way to ensure that all methods and variables are kept private until they are explicitly exposed; usually through an object literal returned by the closure from which it’s defined.

Advantages

  • Cleaner approach for developers
  • Supports private data
  • Less clutter in the global namespace
  • Localization of functions and variables through closures
  • The syntax of our scripts are even more consistent
  • Explicitly defined public methods and variables which lead to increased readability

Disadvantages

  • The same as Module Pattern

 

The Module Pattern

Going to js-module-pattern, the pattern is used to mimic classes in conventional software engineering and focuses on public and private access to methods & variables. The aim is to improve the reduction of globally scoped variables, thus decreasing the chances of collision with other code throughout an application.

Advantages

  • Cleaner approach for developers
  • Supports private data
  • Less clutter in the global namespace
  • Localization of functions and variables through closures

Disadvantages

  • Private methods are unaccessible.
  • Private methods and functions lose extendability since they are unaccessible.

 Another example of the module pattern that exposes the module a little differently and makes use of a shared private cache. This method encourages more of an object creation approach where we can optimize performance by being efficient with shared storage.

 

WCF vs Web API vs WCF REST vs Web Service (SOAP)

The .Net framework has a number of technologies that allow you to create HTTP services such as Web Service, WCF and Web API.

Web Service

  • It is based on SOAP and return data in XML form.

  • It support only HTTP protocol.
  • It is not open source but can be consumed by any client that understands xml.
  • It can be hosted only on IIS.

WCF

  • It is also based on SOAP and return data in XML form.

  • It is the evolution of the web service(ASMX) and support various protocols like TCP, HTTP, HTTPS, Named Pipes, MSMQ.
  • The main issue with WCF is its tedious and extensive configuration (see WCF Tutorial).
  • It is not open source but can be consumed by any client that understands xml.
  • It can be hosted with in the application or on IIS or using windows services.

WCF Rest

  • To use WCF as WCF Rest service you have to enable webHttpBindings.

  • It support HTTP GET and POST verbs by [WebGet] and [WebInvoke] attributes respectively.
  • To enable other HTTP verbs you have to do some configuration in IIS to accept request of that particular verb on .svc files
  • Passing data through parameters using a WebGet needs configuration. The UriTemplate must be specified
  • It support XML, JSON and ATOM data format.

Web API

  • This is the new framework for building HTTP services with easy and simple way.

  • Web API is open source an ideal platform for building REST-ful services over the .NET Framework.
  • Unlike WCF Rest service, it use the full featues of HTTP (like URIs, request/response headers, caching, versioning, various content formats)
  • It also supports the MVC features such as routing, controllers, action results, filter, model binders, IOC container or dependency injection, unit testing that makes it more simple and robust.
  • It can be hosted with in the application or on IIS.
  • It is light weight architecture and good for devices which have limited bandwidth like smart phones.
  • Responses are formatted by Web API’s MediaTypeFormatter into JSON, XML or whatever format you want to add as a MediaTypeFormatter.

To whom choose between WCF or WEB API

  • Choose WCF when you want to create a service that should support special scenarios such as one way messaging, message queues, duplex communication etc.

  • Choose WCF when you want to create a service that can use fast transport channels when available, such as TCP, Named Pipes, or maybe even UDP (in WCF 4.5), and you also want to support HTTP when all other transport channels are unavailable.
  • Choose Web API when you want to create a resource-oriented services over HTTP that can use the full features of HTTP (like URIs, request/response headers, caching, versioning, various content formats).
  • Choose Web API when you want to expose your service to a broad range of clients including browsers, mobiles, iphone and tablets.

Asp.net MVC vs Asp.net Web API

Asp.net MVC framework can return JSON data by using JsonResult and can also handle simple AJAX requests. Asp.net Web API is the new framework for building HTTP services with easy and simple way.

  1. Asp.Net MVC is used to create web applications that returns both views and data but Asp.Net Web API is used to create full blown HTTP services with easy and simple way that returns only data not view.

  2. Web API helps to build REST-ful services over the .NET Framework and it also support content-negotiation(it’s about deciding the best response format data that could be acceptable by the client. it could be JSON, XML, ATOM or other formatted data), self hosting which are not in MVC.

  3. Web API also takes care of returning data in particular format like JSON, XML or any other based upon the Accept header in the request and you don’t worry about that. MVC only return data in JSON format using JsonResult.

  4. In Web API the request are mapped to the actions based on HTTP verbs but in MVC it is mapped to actions name.

  5. Asp.Net Web API is new framework and part of the core ASP.NET framework. The model binding, filters, routing and others MVC features exist in Web API are different from MVC and exists in the new System.Web.Http assembly. In MVC, these featues exist with in System.Web.Mvc. Hence Web API can also be used with Asp.Net and as a stand alone service layer.

  6. You can mix Web API and MVC controller in a single project to handle advanced AJAX requests which may return data in JSON, XML or any others format and building a full blown HTTP service. Typically, this will be called Web API self hosting.

  7. When you have mixed MVC and Web API controller and you want to implement the authorization then you have to create two filters one for MVC and another for Web API since boths are different.

  8. Web API is light weight architecture and except the web application it can also be used with smartphone apps.

Asp.net Web API Features

Web API is the great framework for exposing your data and service to different-different devices. It is open source an ideal platform for building REST-ful services over the .NET Framework. Unlike WCF Rest service, it use the full features of HTTP (like URIs, request/response headers, caching, versioning, various content formats) and you don’t need to define any extra config settings for different devices unlike WCF Rest service.

Web API Features

  • It supports convention-based CRUD Actions since it works with HTTP verbs GET, POST, PUT and DELETE.
  • Responses have an Accept header and HTTP status code.
  • Responses are formatted by Web API’s MediaTypeFormatter into JSON, XML or whatever format you want to add as a MediaTypeFormatter.
  • It may accepts and generates the content which may not be object oriented like images, PDF files etc.
  • It has automatic support for OData. Hence by placing the new [Queryable] attribute on a controller method that returns IQueryable, clients can use the method for OData query composition.
  • It can be hosted with in the application or on IIS.
  • It also supports the MVC features such as routing, controllers, action results, filter, model binders, IOC container or dependency injection that makes it more simple and robust.

Why to choose Web API ?

  • If we need a Web Service and don’t need SOAP, then ASP.Net Web API is best choice.
  • It is Used to build simple, non-SOAP-based HTTP Services on top of existing WCF message pipeline.
  • It doesn’t have tedious and extensive configuration like WCF REST service.
  • Simple service creation with Web API. With WCF REST Services, service creation is difficult.
  • It is only based on HTTP and easy to define, expose and consume in a REST-ful way.
  • It is light weight architecture and good for devices which have limited bandwidth like smart phones.
  • It is open source.