index.js

const mysqldump = require('mysqldump');
const cron = require('node-cron');
const path = require('path');
const fs = require('fs');
const diskfree = require('diskfree');
const sgMail = require('@sendgrid/mail')


const sendEmail = (sendTo,sendFrom, sendGridApiKey, subject, email_content) => {
  let msg = {
    to: sendTo,
    from: sendFrom,
    subject,
    text: subject,
    html: email_content,
  }
  sgMail.setApiKey(sendGridApiKey)
  sgMail
    .send(msg)
    .then((response) => {
      console.log("sendgrid ", response[0].statusCode)
      console.log("sendgrid ", response[0].headers)
    })
    .catch((error) => {
      console.error("sendgrid ", error.toString(), JSON.stringify(error, null, 2))
    })
};

let fsPromises = fs.promises;
let success = 0;

let setUpCron =  (options) => {
    validateOptions(options);
    attemptBackup(options);
    cron.schedule(options.cronSchedule, () => {
        attemptBackup(options);
    });
};

let attemptBackup = async (options) => {
    console.log('Starting Backup')
    let timestamp = null;
    try {
        await ensureFreeDiskSpace(options.directory);
        timestamp = await backupDatabase(options.connection, options.directory);
        if(options.maxBackups) await removeOldestBackups(options.maxBackups, options.directory);
    } catch(e) {
        console.error(e);
        return sendFailureEmail(options.sendTo, options.sendFrom, options.sendGridApiKey, e, options.connection.database);
    }

    console.log('Backup Complete', new Date(timestamp), timestamp);
    if(++success % options.sendSuccessEmailAfterXBackups !== 0) return;
    sendSuccessEmail(options.sendTo, options.sendFrom, options.sendGridApiKey, timestamp, options.directory, options.connection.database);
};

let backupCount = async (directory)=>{
    await ensureDirectoryExists(directory);
    let files = await fsPromises.readdir(directory);
    return files.length;
};

let removeOldestBackups = async (maxBackups, directory) => {
    await ensureDirectoryExists(directory);
    let files = await fsPromises.readdir(directory);
    files = files.sort(sortFiles);
    let count = 0;
    let now = Date.now();
    for(let i in files){
        if(++count > maxBackups){
            await fsPromises.unlink(path.join(directory, files[i]));
            console.log("Removing Backup", path.join(directory, files[i]));
        }
    }
};

let removeOldestBackup = async (directory) => {
    await ensureDirectoryExists(directory);
    let files = await fsPromises.readdir(directory);
    files = files.sort(sortFiles);
    if(files.length === 0)return false;
    let toDelete = files.pop();
    await fsPromises.unlink(path.join(directory, toDelete));
    console.log("Removing Backup", path.join(directory, toDelete));
    return true;
};

let backupDatabase = async (connection, directory) => {
    let timestamp = Date.now();
    ensureDirectoryExists(directory);
    let result = await mysqldump({
        connection,
        dumpToFile: path.join(directory, timestamp+'.sql'),
    });
    return timestamp;
};

let ensureFreeDiskSpace = async (directory) => {
    let largestBackup = await largestBackupSizeBytes(directory);
    let free  = await freeSpaceBytes();
    let total  = await totalSpaceBytes();
    console.log('free space', free);
    console.log('total space', total);
    console.log('largest backup', largestBackup);
    if((free / total) < 0.1) { // keep 10% free
        let fileRemoved = await removeOldestBackup(directory);
        if(!fileRemoved) return;
        return await ensureFreeDiskSpace(directory)
    }
};

let freeSpaceBytes = ()=>{
    return new Promise((resolve, reject)=>{
        diskfree.check('/', (err,stats)=>{
            if(err) reject(err);
            resolve(stats.available);
        });
    });
};

let totalSpaceBytes = ()=>{
    return new Promise((resolve, reject)=>{
        diskfree.check('/', (err,stats)=>{
            if(err) reject(err);
            resolve(stats.total);
        });
    });
};

let largestBackupSizeBytes = async (directory) => {
    await ensureDirectoryExists(directory);
    let files = await fsPromises.readdir(directory);
    let largest = 0;
    for (let i in files){
        const stats = await fsPromises.stat(path.join(directory, files[i]));
        if(stats.size < largest) continue;
        largest = stats.size;
    }
    if(!largest) return 0;
    return largest;
};

let sendSuccessEmail = async (sendTo, sendFrom, sendGridApiKey, timestamp, directory, database) => {
    let backups = await backupCount(directory);
    let currentBackups = fs.readdirSync(directory).map(toDate).join('\n');

    await sendEmail(sendTo, sendFrom,sendGridApiKey,database +" Backup Complete", "Your last database backup was on " + new Date(timestamp)+'.\n You have ' + backups +' backups.\n' + currentBackups);
};

let sendFailureEmail = async (sendTo, sendFrom, sendGridKey, e, database) => {
    await sendEmail(sendTo, sendFrom, sendGridKey, database + " Backup Failed", "Here is the error message /n " +e + JSON.stringify(e));
};


let validateOptions = (options) => {
    let requiredFields = ['cronSchedule', 'sendTo', 'connection', 'sendFrom', 'sendGridApiKey', 'sendSuccessEmailAfterXBackups', 'directory'];
    let requiredConnectionFields = ['host', 'user', 'password', 'database'];
    let missing = validateObj(options, requiredFields);
    let missingConnection = validateObj(options.connection, requiredConnectionFields);
    let error = '';
    if(missing.length > 0){
        error = 'You need to include '+ missing.join(', ')+ ' in the options object.\n';
    }
    if(missingConnection.length > 0){
        error += 'You need to include '+ missingConnection.join(', ')+ ' in the options.connection object.\n';
    }
    if(error)throw new Error(error);
};

let validateObj = (object, required) => {
    let missing = [];
    for(let i in required){
        let opt = required[i];
        if(object[opt]) continue;
        missing.push(opt);
    }
    return missing;
};

let sortFiles = (a, b)=>{
    let aTime = parseInt(a.replace('.sql', ''));
    let bTime = parseInt(b.replace('.sql', ''));
    return bTime - aTime;
};

let ensureDirectoryExists = async (directory) => {
    if (!fs.existsSync(directory)) {
        await fsPromises.mkdir(directory);
    }
};
const toDate = (backupFileName) => {
   return new Date(parseInt(backupFileName.replace('.sql', ''))).toISOString()
}

module.exports = setUpCron;