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- It is very lightweight
- It has a robust HTTP library
- It has robust support from 3rd party libraries for reading and modifying HTTP requests
- It is highly performant
Libraries to use
- Express Koa - Express Koa is a new web application framework for node.js. It provides easy mechanisms to expose web endpoints and process requests and responses in a stack-like approach.
- Connect - Connect provides middleware for node.js that allow HTTP requests and responses can be altered while in 'flight'. The express framework also uses connect middleware and middleware are exposed from the express framework as well.
General Overview
The Express library which includes the Connect middleware Koa framework provides an easy way to modify HTTP request and responses as they are being processed. Each step that the OpenHIM needs to perform can be written as Connect Koa middleware. Each middleware can handle a different aspect of processing that the OpenHIM need to perform such as authentication, authorization, message persistence and message routing. Developing each of these steps as connect Koa middleware allows them to be easily reused and allows us to add new step steps for future versions.
More information on Connect middleware can be found here: http://www.senchalabs.org/connect/ and http://stephensugden.com/middleware_guide/
Koa stack approach to processing requests also fit our usecase well as it allows the middleware to affect both the request and the response as it is travelling through the system.
The Koa framework also gives us some convenience ctx.request and ctx.respose The express library gives us some convenience req and res objects that are designed to be used for web applications but they are equally useful for handling web services.
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