36
loading...
How I met your...Scraper?
How I met your... Scraper?
Hello developer pal!, glad to see you here.
In this post, I'll share my experience after running into a topic I had not met before... web scraping!.
Show Me The Topics
The topics to be focused on are:
Disclaimer: This post comes from a particular scenario I've been struggling with, I'm not preaching this is the best approach to follow for web scraping, nor the worst, any contribution is more than welcome in the threads below!
Note: There is available also a template project on GitHub in case it could be useful and save you some time.
A couple weeks ago, I got subscribed to a weekly delivery service, I am pretty happy with the service!, it is fast, efficient, always on time!, since day 1 the service has had no issues, not even delays, what's the only fallback I have found so far?, the booking process!
This could be a little picky from my end, I know, but see the steps I need to do every-single-day:
These steps needs to be done every-single-day, and it is a pain in the back, cause if for some reason I forget to do it, my preferred time could have been taken, and I need to look for a different time, then I need to be aware of the delivery time(it would be different a week from today than the rest of the days); am I clear why this is a pain?, I hope so...
After a few days of missing the booking, I decided to automate the process with the help of some tools, I was not sure about how to start, so I research and gladly met web scrapping(don't get me wrong, I had heard about it, but there is a slightly difference between hearing and researching with a purpose, at least form my end 🤷).
So, what's the web scraping?, there are plenty of definitions out there on the Internet, the one that is more accurate for this post purposes is:
Web scraping is the process of using bots to extract content and data from a website.
- Source: What is web scraping?
This is exactly what this post is about, create a sort of robot that will fill in information on my behalf in a site and later it will extract a result for me, and put it on my inbox.
The tools used for accomplishing this enterprise are:
Main Dependencies
Dev Dependencies
package.json
"dependencies": {
"express": "^4.17.1",
"nodemailer": "^6.6.2",
"puppeteer": "^10.1.0"
},
"devDependencies": {
"eslint-config-prettier": "^8.3.0",
"eslint-plugin-prettier": "^3.4.0",
"nodemon": "^2.0.9",
"prettier": "^2.3.2"
}Prettier and Nodemon come handy for having a nice experience, not mandatory though, fell free to use any other tool.For this project, the structure is simple and set as follows:
scraper-template/
├── index.js
├── package.json
└── routes/
├── booking.js
└── screenshots/
├── home-page.png
└── services/
├── bookingHandler.js
├── emailSender.jsThere is one route for express to serve, two services for booking and emailing the results and a folder for screenshots, which only steps in development environment.
The
index.js is a simple file with a 20 lines extension:const express = require('express');
const app = express();
const port = process.env.PORT || 3000;
const booking = require('./routes/booking');
app.get('/', (req, res) => {
res.json({ message: 'ok' });
});
app.use('/booking', booking);
/* Error handler middleware */
app.use((err, req, res, next) => {
const statusCode = err.statusCode || 500;
console.error(err.message, err.stack);
res.status(statusCode).json({ message: err.message });
return;
});
app.listen(port, '0.0.0.0', () => {
console.log(`Scrapper app listening at http://localhost:${port}`);
});The
routes/booking.js includes the expressjs, services and config references, let's decompose it!:express.js
The references to the packages used:
const express = require('express');
const router = express.Router();
...
...services.js
The references to the defined services for handling the bookings and sending emails, a preview can be found below on Services Visualization
...
...
const emailSender = require('../services/emailSender');
const bookingHandler = require('../services/bookingHandler');
...
...config.js
All the vales in here are
process.env vars, these includes keys for login(webSiteUser, webSitePassword), email impersonation(authUser, appPassword) and email receivers(emailFrom, emailTo):...
...
const {
webSiteUser,
webSitePassword,
authUser,
appPassword,
emailFrom,
emailTo,
preferTime,
} = require('../config');book-me endpoint
This route does the booking process for a user with a preferred time(if any):
router.get('/book-me', async function (req, res, next) {
try {
const bookMeResult = await bookingHandler.bookMe(
webSiteUser,
webSitePassword,
preferTime
);
res.send(`The result of the booking was::${bookMeResult}`);
} catch (err) {
console.error(`Error while booking me for next week`, err.message);
next(err);
}
});
...
...book-me endpoint
This route gets the bookings the user has set for the upcoming week:
...
...
router.get('/my-bookings', async function (req, res, next) {
try {
const bookingResult = await bookingHandler.myBookings(
webSiteUser,
webSitePassword
);
emailSender.sendEmail(bookingResult, {
authUser,
appPassword,
emailFrom,
emailTo,
});
res.format({
html: () => res.send(bookingResult),
});
} catch (err) {
console.error(`Error while getting the booking for this week`, err.message);
next(err);
}
});Service
emailSender:
Service
bookingHandler:
Here is where the magic begins!, only one reference for rule the whole process:
const puppeteer = require('puppeteer');After this import,
puppeteer is ready to roll!; there are plenty of examples on the internet, most of them apply all the concepts for web scraping in one single file, this is not the case.This project applies some separations that, from my perspective, makes it easier to understand what's going on every step throughout the whole process, so let's dive into the sections:
-- Start the Browser --
The first interaction is starting the Browser.
Puppeteer works perfectly with Chronium and Nightly, for this project the reference used is the default one, with Chrome(the web site to scrap only opens on Chrome), but if Firefox preferred, take a look at this thread on StackOverflow.In the piece of code below, there is a var initialized for
isProduction, this var is ready for being used when deployed on a web platform(Heroku we'll talk about it later), and another for isDev, I repeat, this is for explanation purposes, it is not required to have 2 when one of them can be denied and cause the same result.When
isProduction the launch is done headless by default, it means that the process is done in the background without any UI, also some args are included for a better performance, refer to the list of Chromium flags here.When
isDev, the headless is false, and args also include one for opening te dev tools after loading the browser.const isProduction = process.env.NODE_ENV === 'production' ? true : false;
const isDev = !isProduction;
const authenticationError = 'Failed the authentication process';
const bookingError = 'Failed the booking process';
async function startBrowser() {
let browser = null;
let context = null;
let page = null;
if (isProduction) {
browser = await puppeteer.launch({
args: ['--no-sandbox', '--disable-setuid-sandbox', '--disable-dev-shm-usage'],
});
page = await browser.newPage();
} else {
browser = await puppeteer.launch({
headless: false,
defaultViewport: null,
slowMo: 75,
args: [
'--auto-open-devtools-for-tabs',
'--disable-web-security',
'--disable-features=IsolateOrigins,site-per-process',
'--flag-switches-begin --disable-site-isolation-trials --flag-switches-end',
],
});
context = await browser.createIncognitoBrowserContext();
page = await context.newPage();
}
return { browser, page };
}As seen above, the site is loaaded in Incognito, but can be opened in a regular tab.
-- Do Login --
For doing the login, some
puppeteer features come in play:goto: allows the navigation to a web sitetype: types a value in an input fieldclick: allows clicking on buttons, table cells, submitswaitForSelector: recommended for allowing the page to recognize a particular selector before moving alongscreenshot: takes a screenshot on demand, and store it in the app(it is possible to redirect the screenshots to remote services, in dev just place them in a root folder)
async function doLogIn(page, webSiteUser, webSitePassword) {
await page.goto(constants.baseUrl + constants.loginEndpoint, {
timeout: constants.timeOut,
waitUntil: 'load',
});
isDev && console.log('Navigation to Landing Page Succeeded!!!');
await page.type('#loginform-email', webSiteUser);
await page.type('#loginform-password', webSitePassword);
await page.click('button[type="submit"]');
isDev && console.log('Login submitted');
await page.waitForSelector('#sidebar');
isDev && (await page.screenshot({ path: 'screenshots/home-page.png' }));
return await findLink(page, constants.scheduleEndpoint);
}Something to remark in the code above is that when dealing on development environment, the screenshots are taken, in production those are skipped(on purpose for the sake of the example)
-- Find a link --
This can change from page to page, but for this project, there is a link that was tracked down to the point that only
loggedin members are able to see, for finding this or any other, a function is available, which receives as parameters the page instance and the endpoint to look for as an href:async function findLink(page, endpoint) {
const pageLinks = await page.evaluate(() =>
Array.from(document.querySelectorAll('a[href]'), a => a.getAttribute('href')),
);
return pageLinks.includes(endpoint) || null;
}-- Close the Browser --
Just pass the
browser instance as parameter and close it.async function closeBrowser(browser) {
return browser.close();
}Note: not going to elaborate on the details of the booking process, just take into account:
Puppeteer
Email service is contained in 30 lines of code, it is a define structure required by the import of
nodemailerNote: When using
Gmail, it is mandatory to enable less secure apps, this will create a new password for just the particular application you are trying to link to, can read more here in nodemailer or in Google Supportconst nodemailer = require('nodemailer');
async function sendEmail(weekBookings, { authUser, appPassword, emailFrom, emailTo }) {
const mail = nodemailer.createTransport({
service: 'gmail',
auth: {
user: authUser,
pass: appPassword,
},
});
const mailOptions = {
from: emailFrom,
to: emailTo,
subject: 'Your bookings for this week',
html: weekBookings,
};
mail.sendMail(mailOptions, (error, info) => {
if (error) {
console.log(error);
} else {
console.log('Email sent: ' + info.response);
}
});
}
module.exports = {
sendEmail,
};There is not too much complication in here, pass the
authUser, appPassword, email from/to and the html to be send as email.How to be sure that everything is working as expected?, well two options:
-- Locally --
For running this locally Postman is the tool(don't judge me too much, I am used to it... used to Postman I meant, anyway)
WEB_SITE_USER=YOUR_USER@YOUR_EMAIL_DOMAIN.com WEB_SITE_PASSWORD=YOUR_PASSWORD
[email protected] GMAIL_APP_PASSWORD=YOUR_APP_PASSWORD
[email protected] [email protected]
BOOKING_PREFER_TIME=06:55:00 npm run devThis command will start the local server using
nodemon setting all the expected process.env variables in port 3000 by default, so just use Postman for hitting http://localhost:3000/booking/book-me or http://localhost:3000/booking/my-bookings and a result will be retrieved.-- Remote --
For deploying remotely the platform used id Heroku, not getting in details but found this helpful post in case you decide to follow that path(read carefully the
All the
Heroku's sections, and highly suggested to use Kaffeine).All the
process.env passed to the terminal when running locally are set as Heroku's environment variables, then the deploy is transparent.Sometimes the sites you try to scrap are sort of "protected" by
Captcha, I say "sort of" cause there are ways to skip it, even some companies pay to regular users to help them to recognize captchas, you can read more over here.The page scraped for this post behaves "interesting", sometimes the
reCaptcha is ignored, some others appear right after submitting the login, so randomly fails; I opened an issue in puppeteer-extra, an npm lib extension for puppeteer which works hand-to-hand with 2captcha, I'm watching the issue closely, in case of getting a fix for the random issue I'll edit the post.In case you were wondering, the hit of the endpoints after deployed to
Heroku are done by a Cron-Job, it is fast and easy, and I received a custom email when the process randomly fails(the idea is to make it work permanently!).As shown above, the web scraping is a great technique for making life easier, some hiccups could appear along the way(Captcha, Deploy servers restrictions or conditions) though some how it is possible to make it through!; maybe you could have a better way to do it, let's discuss in a thread below!
Thanks for reading!
36