Fullstack Serverless

In this tutorial we will build fullstack serverless app that has REST API and React UI components.

• npx create-react-app hello-react
• cd hello-react
• yarn add aws-amplify
• amplify init
• amplify add api
  • Service: REST
  • Project: mypythonapi
  • Path: /greeting
  • Lambda source: Create new lambda function
  • Friendly name: mypythonfunction
  • Function name: mypythonfunction
  • Runtime: Python
  • Others: No
• amplify push --y
• amplify hosting add
  • Select the plugin module to execute: Amazon CloudFront and S3
  • Select the environment setup: DEV (S3 only with HTTP)
  • Hosting bucket name: helloreact-20201222120745-hostingbucket
  • Index doc for the website: index.html
  • Error doc for the website: index.html
• amplify publish
  • http://xxxx.s3-website-eu-west-1.amazonaws.com/

Issue Patch

Amplify provide amplify push --y command to provision resources as cloudformation template. It only provides python >= 3.8 version. Issue is still in progress on github on late December 2020. Below is a workaround on Amazon Linux 2 OS.

aws-amplify/amplify-hosting#595

amazon-linux-extras install python3.8
ln -fs /usr/bin/python3.8 /usr/bin/python3
pip3.8 install pipenv
amplifyPush --simple

Backend API

The Lambda function template generated by amplify add api command. So, there should be edited on your IDE (Cloud9, VSCode, Atom etc.)

You can find index.py file in the /hello-react/amplify/backend/function/mypythonfunction/src/ path.

import json

def handler(event, context):
  body = {
    "message": "Hello from Lambda !"
  }
  
  response = {
    "statusCode": 200,
    "body": json.dumps(body),
    "headers": {
      "Content-Type": "application/json",
      "Access-Control-Allow-Origin": "*"
    }
  }
  
  return response

Then, we are ready to push our backend api to AWS Lambda and API Gateway via amplify push --y command.

• API gateway endpoint: https://xxxx.execute-api.eu-west-1.amazonaws.com/dev
• You can double check properties from aws-export.js file.

// WARNING: DO NOT EDIT. This file is automatically generated by AWS Amplify. It will be overwritten.

const awsmobile = {
    "aws_project_region": "eu-west-1",
    "aws_cloud_logic_custom": [
        {
            "name": "mypythonapi",
            "endpoint": "https://xxxxx.execute-api.eu-west-1.amazonaws.com/dev",
            "region": "eu-west-1"
        }
    ]
};


export default awsmobile;

Frontend

Following block is index.js

• npm install aws-amplify

import React from 'react';
import ReactDOM from 'react-dom';
import './index.css';
import App from './App';
import reportWebVitals from './reportWebVitals';

import Amplify from 'aws-amplify'; // load library dependencies
import awsconfig from './aws-exports'; // load backend exports
Amplify.configure(awsconfig); // configure amplify to use credentials

ReactDOM.render(
  <React.StrictMode>
    <App />
  </React.StrictMode>,
  document.getElementById('root')
);

// If you want to start measuring performance in your app, pass a function
// to log results (for example: reportWebVitals(console.log))
// or send to an analytics endpoint. Learn more: https://bit.ly/CRA-vitals
reportWebVitals();

Following block is app.js

import React, {useState, useEffect } from 'react';
import logo from './logo.svg';
import './App.css';

import { API } from 'aws-amplify' // import amplify dependencies

function App() {
  const [greeting, setGreeting] = useState(null) // construct greeting and setGreeting 
  async function fetchGreeting() { // declare an asynch function called fetchGreeting
    const apiData = await API.get('mypythonapi', '/greeting') // Get API by using amplify library
    setGreeting(apiData.message) // Set message property to the response of fetchGreeting() 
  }
  useEffect(() => { // useEffect hook for async func. transition 
    fetchGreeting()
  }, [])
  
  return (
    <div className="App">
      <header className="App-header">
        <img src={logo} className="App-logo" alt="logo" />
       <h1>{greeting}</h1> <! -- Call greeting constructor --> 
      </header>
    </div>
  );
}

export default App;

References:

• https://docs.amplify.aws/
• https://github.com/dabit3