Webservices

Slides
Authors

Cyriel Mallart

Ludovic Deneuville

Rémi Pépin

The Plan

  • API
  • Webservice
    • Definition
    • Examples
    • Microservices Architecture
  • Hyper Text Transfer Protocol
    • Definition
    • Examples

API

Definition

API = Application Programming Interface

Note

Interface between two computers or two programs.

It is an application that provides services to other applications.

The application implements an API or exposes an API.

A fairly broad term that covers:

API in a Nutshell

  • Exposes methods/functions to users
  • Reusable
  • Black box
  • Contract between provider and user on inputs/outputs

Pour reprendre l’exemple du dessus, le module d’authentification peut être utilisé aussi bien par les utilisateurs pour la version site marchand, que par les admins pour la partie administration.

Note

An API provides a service to users without them needing to know how it works. They only know what it expects as input and what it produces!

Webservices

A specific type of API.

Question

In your opinion, does X allow everyone to directly access their databases?

Bien sûr non !

Wait what?!

  • But many sites use X’s data!
  • How do they do it?

Any ideas?

Solution: Web Scraper

Involves writing an application that:

  • Connects to a site
  • Reads the page to extract information

Problems:

  • Creates artificial traffic (on the site’s side)
  • Any change in the site breaks our application
  • Managing JavaScript 😱😱😱😱

Dire que derrière un site il y a du HTML.

Montrer un exemple ?

Prix SNCF à l’INSEE

Another Solution: Create an Entry Point for Machines

  • Accessible from the web
  • Made for machines
  • Controls what is made accessible

Interface between the outside and our system

Démo

Webservices

  • Web application
  • Accessible via HTTP/HTTPS request
  • No graphical interface
  • Returns data understandable by machines (JSON, XML, etc.)

Webservice : une API particulière que nous allons utiliser

Several Types

  • REST: most common, the type you will handle, JSON
  • SOAP: more complete but heavier than REST, XML
  • RPC: Remote Procedure Call

REST est un style architectural qui définit un ensemble de contraintes et de principes

In Summary

Note

A web service is an application module, accessible over the HTTP protocol via a URL that will respond to a request

➡️ Like a website, but for machines

Microservices Architecture

E-commerce site:

  • Authentication WS
  • Account management WS
  • Payment WS
  • Search WS
  • Data analysis WS
  • Cart management WS

Microservices Architecture

  • Each module is an independent web service
  • It is the client-side application that will contact them
Note

Useful for large companies with many developers and parallel projects.

Un dessin pourrait peut-être aider

How Does It Work?

The Client-Server Concept

  • THE MODEL THAT GOVERNS THE WEB
  • Machines waiting for requests: servers
  • Machines making requests: clients
  • The client initiates contact, the server responds

Real-Life Comparison

  • You are walking down the street and want a Double shot espresso and Cream
  • You enter a Starbucks and order your coffee
  • The server processes your request and gives you your coffee
  • You leave with your coffee

Vous vous moquez de comment à été fait votre café, tant que c’est bon

Hyper Text Transfer Protocol (HTTP)

HTTP

Client-server communication protocol developed for the World Wide Web

Not the only one: FTP, SMTP, IRC…

There are non-client-server protocols: BitTorrent

Avez vous une idée de requête HTTP ?

  • Internet est l’infrastructure
  • Web est un service qui fonctionne dessus

https : http + SSL

Le navigateur cache le protocole

Secure Sockets Layer (SSL)

Secure connection between a client and a server:

  • The client sends a message to the server
  • The server responds and sends its certificate
  • The client verifies the validity of the certificate
  • The client generates a session key encrypted with the server’s public key
  • Both parties communicate with the session key

Commencer par parler chiffrage :

  • Chiffrage symétrique : Une seule clé est utilisée pour chiffrer et déchiffrer les données
  • Chiffrage asymétrique : une clé publique pour chiffrer les données et une clé privée pour les déchiffrer

Certificat :

  • Clé publique
  • Informations sur le propriétaire
  • Période de validité
  • Autorité de certification
  • Signature numérique : message haché puis chiffré avec clé privée

Video

Les éléments d’une requête

  • Location of the resource: URL (domain name + path)
  • Method used (GET, POST, UPDATE, DELETE…)
  • Request parameters
  • Request body

Les paramètres sont derrière le ?

Le corps vous ne le voyez pas, mais il est possible de le voir.

Dans le navigateur, on ne fait que des GET

Elements of a Request

GET https://pokeapi.co/api/v2/pokemon?limit=10&offset=200

  • method
  • protocol
  • ws address
  • endpoint
  • parameters

Pour aller plus loin : IP, DNS

HTTP Methods

  • POST
  • GET
  • UPDATE
  • DELETE
Important

C’est le CRUD !

Comme en SQL

Example

  • GET http://web-services.domensai.ecole/attack
    • retrieve all attacks
  • GET http://web-services.domensai.ecole/attack/2684
    • retrieve an attack by its id
  • DELETE http://web-services.domensai.ecole/attack/2684
    • delete an attack
  • POST http://web-services.domensai.ecole/attack
    • add an attack
  • PUT http://web-services.domensai.ecole/attack/2684
    • modify an attack
body
{
  "name": "tickle",
  "attack_type": "physical attack",
  "power": 2,
  "accuracy": 5,
  "description": "string"
}
  • PATCH http://web-services.domensai.ecole/attack/2684
    • modifier seulement certains attributs d’une attaque

In Summary

  • HTTP is the protocol of the web
  • Method
  • URL
  • Parameters in URL or body

Contacting/Creating a Webservice

Contacting a Webservice

A tool: an HTTP client

  • A web browser (quite limited)
  • Insomnia/Postman/Bruno
  • Vscode with plugins
  • Python with the requests plugin

Contacting a Webservice in Python

import requests
# Building the request
url = "https://data.rennesmetropole.fr/api/records/1.0/search/"
parameters = {"dataset": "etat-du-trafic-en-temps-reel", "rows": 2}
# Launching the request
res = requests.get(url=url, params=parameters)
# Displaying the result
print(res.json())
print("\nNumber of rows: ", res.json()["parameters"]["rows"])
import json
import requests
url = "https://anapioficeandfire.com/api/"
end_point = "characters"
parameters = {"gender": "Female", "isAlive": True, "culture": "Braavosi"}
response = requests.get(url=url + end_point, params=parameters)
# Check if the server responded
if response.status_code != 200:
    raise Exception(f"Cannot reach (HTTP {response.status_code}): {response.text}")
print(json.dumps(response.json()))
  • Very easy
  • res.json() returns a dictionary
  • get() can become post(), put(), etc.

Creating a Webservice in Python

  • May seem complex 😵
  • But there are tools to help us 😎
  • No need to be a computer expert! 🐱‍💻

3 Frameworks

FastApi pour le TP2

FastApi: The Basics

from fastapi import FastAPI
app = FastAPI()
@app.get("/")

async def root():
    return {"message": "Hello World"}

if __name__ == "__main__":
    uvicorn.run(app, host="0.0.0.0", port=8000)

FastApi

  • It is easy to code your endpoints
  • The documentation is extremely well done
  • You focus on the essentials