Code_HW2.txt

const express = require('express');
const mariadb = require('mariadb');
const path = require('path');
const axios = require('axios');
const bodyParser = require('body-parser');
const { error } = require('console');
const app = express();
const ip = '34.56.60.41';   // ip and replicaIp are switched on other VM
const replicaIp = '35.239.139.129';
const port = 80;

const pool = mariadb.createPool({
 host: '127.0.0.1',
 port: 3306,
 user: 'lgetter2',
 password: 'secret',
 database: 'hw2',
 connectionLimit: 5
});

app.use(bodyParser.urlencoded({ extended: true }));
app.use(express.json());

app.get('/greeting', async (req, res) => {
  res.status(200).send('Hello World!');
});

app.post('/register', async (req, res) => {
  const username = req.body.username;
  let conn;
  try {
    conn = await pool.getConnection();
    await conn.query('INSERT INTO users(username) VALUES (?)', [username]);
    axios.post(`http://${replicaIp}/register-replica`, { username : username });
    res.status(200).send();
  } catch (err) {
    res.status(500).send(`Error adding user: ${err}`);
  } finally {
    if (conn) conn.release();
  }
});

app.post('/register-replica', async (req, res) => {
  const username = req.body.username;
  let conn;
  try {
    conn = await pool.getConnection();
    await conn.query('INSERT INTO users(username) VALUES (?)', [username]);
    res.status(200).send();
  } catch (err) {
    res.status(500).send(`Error adding user: ${err}`);
  } finally {
    if (conn) conn.release();
  }
});

app.get('/list', async (req, res) => {
  let conn;
  try {
    conn = await pool.getConnection();
    const users = await conn.query('SELECT username FROM users');
    const usernames = users.map(user => user.username);
    res.status(200).json({ users : usernames });
  } catch (err) {
    res.status(500).send(`Error retrieving users: ${err}`);
  } finally {
    if (conn) conn.release();
  }
});

app.post('/clear', async (req, res) => {
  let conn;
  try {
    conn = await pool.getConnection();
    await conn.query('DELETE FROM users');
    axios.post(`http://${replicaIp}/clear-replica`);
    res.status(200).send();
  } catch (err) {
    res.status(500).send(`Error deleting users: ${err}`);
  } finally {
    if (conn) conn.release();
  }
});

app.post('/clear-replica', async (req, res) => {
  const username = req.body.username;
  let conn;
  try {
    conn = await pool.getConnection();
    await conn.query('DELETE FROM users');
    res.status(200).send();
  } catch (err) {
    res.status(500).send(`Error adding user: ${err}`);
  } finally {
    if (conn) conn.release();
  }
});

app.listen(port, () => {
  console.log(`Server is running on http://${ip}:${port}`);
});