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flask_api.md

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FLASK

What Is Flask?

Flask is a lightweight WSGI web application framework. It is designed to make getting started quick and easy, with the ability to scale up to complex applications. It began as a simple wrapper around Werkzeug and Jinja and has become one of the most popular Python web application frameworks.

WSGI

The Web Server Gateway Interface (Web Server Gateway Interface, WSGI) has been used as a standard for Python web application development. WSGI is the specification of a common interface between web servers and web applications.

Werkzeug

Werkzeug is a WSGI toolkit that implements requests, response objects, and utility functions. This enables a web frame to be built on it. The Flask framework uses Werkzeg as one of its bases.

jinja2

jinja2 is a popular template engine for Python.A web template system combines a template with a specific data source to render a dynamic web page.

REST APIs

An API, or application programming interface, is a set of rules that define how applications or devices can connect to and communicate with each other. A REST API is an API that conforms to the design principles of the REST, or representational state transfer architectural style. For this reason, REST APIs are sometimes referred to RESTful APIs.

At the most basic level, an API is a mechanism that enables an application or service to access a resource within another application or service. The application or service doing the accessing is called the client, and the application or service containing the resource is called the server.

Some APIs, such as SOAP or XML-RPC, impose a strict framework on developers. But REST APIs can be developed using virtually any programming language and support a variety of data formats. The only requirement is that they align to the following six REST design principles - also known as architectural constraints:

  1. Uniform interface: All API requests for the same resource should look the same, no matter where the request comes from. The REST API should ensure that the same piece of data, such as the name or email address of a user, belongs to only one uniform resource identifier (URI). Resources shouldn’t be too large but should contain every piece of information that the client might need.

  2. Client-server decoupling: In REST API design, client and server applications must be completely independent of each other. The only information the client application should know is the URI of the requested resource; it can't interact with the server application in any other ways. Similarly, a server application shouldn't modify the client application other than passing it to the requested data via HTTP.

  3. Statelessness: REST APIs are stateless, meaning that each request needs to include all the information necessary for processing it. In other words, REST APIs do not require any server-side sessions. Server applications aren’t allowed to store any data related to a client request.

  4. Cacheability: When possible, resources should be cacheable on the client or server side. Server responses also need to contain information about whether caching is allowed for the delivered resource. The goal is to improve performance on the client side, while increasing scalability on the server side.

  5. Layered system architecture: In REST APIs, the calls and responses go through different layers. As a rule of thumb, don’t assume that the client and server applications connect directly to each other. There may be a number of different intermediaries in the communication loop. REST APIs need to be designed so that neither the client nor the server can tell whether it communicates with the end application or an intermediary.

  6. Code on demand (optional). REST APIs usually send static resources, but in certain cases, responses can also contain executable code (such as Java applets). In these cases, the code should only run on-demand.

REST API Methods

These HTTP methods are used with REST APIs:

Method Description
GET Retrieve information about the REST API resource
POST Create a REST API resource
PUT Update a REST API resource
DELETE Delete a REST API resource or related component

Advantages of using Flask framework are:

  • There is a built-in development server and a fast debugger provided.
  • Lightweight
  • Secure cookies are supported.
  • Templating using Jinja2.
  • Request dispatching using REST.
  • Support for unit testing is built-in.

Bring up Flask

Note: Please make the following changes in the Dockerfile
ENV POSTGRES_HOST='127.0.0.1'
In the above line replace '127.0.0.1' with your local system ip

Build docker image

docker build -t ws3 .

Bring up flask app

docker run -p 5000:5000 "ws3:latest"