Can I use Ruby for large-scale web scraping projects?

Yes, you can use Ruby for large-scale web scraping projects. Ruby is a versatile and powerful programming language that has a rich ecosystem of libraries (gems) that facilitate web scraping tasks. While languages like Python may be more popular for web scraping due to frameworks like Scrapy, Ruby still holds its ground with tools like Nokogiri for parsing HTML/XML and HTTParty or Mechanize for handling HTTP requests.

For large-scale web scraping projects, you'll need to consider the following:

• Concurrency and Parallelism: Large-scale scraping often requires making many HTTP requests simultaneously. Ruby has several concurrency models, including multi-threading and event-driven IO (with EventMachine) which can be used to speed up the scraping process.
• Robust Error Handling: You'll need to anticipate and handle a variety of errors, such as network issues, HTTP errors, and changes in the target website's structure.
• Rate Limiting: To avoid getting banned or blocked by the website you're scraping, you'll need to respect their robots.txt file and implement rate limiting and polite scraping practices.
• Data Storage: Decide how to store the scraped data. This could be in a database, a CSV file, or another format. Ruby has libraries for interfacing with all major databases and data formats.
• Distributed Scraping: For truly large-scale scraping, you might need to distribute your scraping tasks across multiple machines or IP addresses. Tools like Sidekiq can help manage background jobs at scale.
• Scraping Frameworks: Although not as common as in the Python ecosystem, there are Ruby frameworks dedicated to web scraping, such as Kimurai, which can provide a good starting point for building scalable scrapers.

Below is a simple example of a Ruby web scraper using Nokogiri and HTTParty:

require 'httparty'
require 'nokogiri'

url = 'https://example.com/products'
response = HTTParty.get(url)
parsed_page = Nokogiri::HTML(response.body)

products = parsed_page.css('.product') # Assuming products have a class named 'product'

products.each do |product|
  title = product.css('.product-title').text
  price = product.css('.product-price').text
  puts "Title: #{title}, Price: #{price}"
end

In the above example, replace 'https://example.com/products' with the actual URL you wish to scrape, and .product, .product-title, and .product-price with the appropriate selectors for the content you're targeting.

If you're dealing with a large volume of pages, you might want to use threads to handle multiple pages at once. Here's a basic example with threading:

require 'httparty'
require 'nokogiri'
require 'thread'

def scrape_page(url)
  response = HTTParty.get(url)
  parsed_page = Nokogiri::HTML(response.body)
  # ... process the page
end

urls = ['https://example.com/products?page=1', 'https://example.com/products?page=2', ...]
threads = []

urls.each do |url|
  threads << Thread.new { scrape_page(url) }
end

threads.each(&:join)

Remember that for large-scale projects, you'll need a more sophisticated setup—with error handling, logging, and possibly a queuing system for the URLs to be processed.

Always make sure to comply with the terms and conditions of the websites you are scraping from, and consider the legal and ethical implications of your scraping activities.