What Elements Does a Web Scraping Project Include?

Data extraction from the internet is becoming very popular. More and more companies are leveraging the power of web scraping. But that doesn't mean technical challenges have disappeared. Building a sustainable scraping infrastructure requires knowledge and experience.

In this article, we will briefly describe the main elements of a successful web scraping project. As well as the functional blocks you need to take care of to build a proper web data pipeline.

Functional Blocks:

• Web spiders
• Spider management
• JavaScript rendering
• Data validation
• Proxy management

Web spiders

Let's start with the obvious - web spiders. In the scraping community, a web spider is a script or program that extracts data from a web page. Spiders are essential for finding information on the internet. There are many libraries and tools we can use. In Python, you have Scrapy, a scraping framework, or BeautifulSoup. If you program in Java, you have Jsoup or HTMLUnit. In JavaScript, it's Puppeteer or Cheerio. These are just the most popular ones, but there are many other libraries and headless browsers that can be used for scraping. If you've never done scraping before, it can be hard to decide.

For one-off small projects, it doesn't matter which library you use. Choose the one that's easiest to get started with in your preferred programming language. For example, BeautifulSoup (or Scrapy) or Jsoup. But for long-term projects where you need to maintain your web spiders and possibly build add-ons on top of them, you should choose a tool that allows you to focus on the specific project needs rather than the basic scraping logic.

Web spider management

Now that we've covered spiders, the next element that should be in your scraping stack is web spider management. Web spider management involves creating an abstraction over your web spiders. A web spider management platform like Scrapy Cloud allows you to quickly get an overview of how your spiders are performing. You can schedule jobs, view scraped data, and automate spiders. You can stay updated on project status without managing servers.

JavaScript rendering

JavaScript, as a technology, is widely used on modern websites. Unfortunately, this complicates your scraping project if the data you want to extract is rendered via JS. But also, if data is passed from the backend to the frontend using AJAX calls, you can obtain that data by inspecting the site and mimicking the AJAX request in your spider to capture a JSON/XML file.

Typically, when you know a site uses JS to render its content, your first instinct might be to use a headless browser like Selenium, Puppeteer, Playwright, etc. That may be necessary if you are trying to bypass anti-bot measures.

The trade-off with headless browsers is that in the short term it's much faster to just render JS and get data, but in the long term it requires significantly more hardware resources. So if execution time and hardware resources matter to you, first thoroughly inspect the site and check if there are any AJAX requests or hidden API calls in the background. If so, try to replicate that in your scraper instead of executing JS.

If there is truly no other way to get the data and you have to execute JS regardless, only then use a headless browser.

Data quality

The next building block is ensuring data quality. All our scraping efforts are worthwhile only if the output is the correct data in the correct format. To ensure this, we can do several things:

• validate output data against a predefined JSON schema
• check coverage of extracted fields
• check for duplicates
• compare two scraping jobs.

It's also useful to set up alerts and notifications that trigger when a certain action occurs.

Proxy management

The last but very important block to mention is proxy management. Proxies are necessary for large-scale projects - when you need to frequently make a large number of requests.

First of all, you need to have an understanding of what is and isn't possible when it comes to scaling. You can't solve all problems by simply throwing more hardware (proxies) at them. Sometimes further scaling is impossible. For example, if your target site has 50,000 visitors per month and you want to scrape it 50,000 times in a month... that won't work. You need to consider the traffic profile of the site before ensuring that your expectations are realistic regarding the number of requests you want to make with your scraper. You can estimate which proxies and how many you need based on target sites, request volume, and geolocation.

There are projects where we need continuous maintenance and we process hundreds of millions or even billions of URLs. For such volume, you will definitely need a proxy solution. You can also simply buy proxies and implement your own proxy management logic. Keep in mind that if scraping is not the core of your business or project, it may make sense to outsource web scraping and save a lot of time on development/maintenance.

Scraping Ethics

Before concluding this article, it's important to talk about scraping ethics. When you scrape a website, you must ensure you are following ethical principles. Here are some best practices you can follow to not violate ethical principles.

Don't be a burden

The most important rule when scraping a website is to not harm it. Don't make too many requests. Too frequent requests can hinder the server's ability to serve other visitors. Limit the request rate according to the target website.

Robots.txt

Before starting to scrape, always check the robots.txt file. This will give you an idea of which parts of the site you can freely visit and which pages you should not visit.

User-agent

Define a user-agent that clearly describes you or your company. Additionally, it's best to include contact information in the user-agent so that users can inform you if they have issues with what you are doing.

Pages behind authentication

There are cases where access to certain pages is only possible if you are logged in. If you want to scrape these pages, you need to be very careful. If you are logged in and/or have explicitly agreed to the site's terms and conditions that state you cannot scrape, then you CANNOT scrape. You must always comply with any agreement you enter into, including the website's terms and conditions and privacy policy.

Final Note

Getting started with scraping is very easy. But as you scale up, it becomes increasingly difficult to keep your web spiders running. You need an action plan to address issues like website layout changes, maintaining high data quality, and proxy server needs. If you refine the functional blocks mentioned, you will be on the right track.

Learn More About Scraping Tools

ESK Solutions has been working in the scraping field for 5 years. During this time, we have accumulated vast experience and knowledge in data scraping.