Vessel - high-level web crawling framework

Fast as Chrome, dead simple and yet extendable.

It is Ruby high-level web crawling framework based on Ferrum for extracting the data you need from websites. It can be used in a wide range of scenarios, like data mining, monitoring or historical archival. For automated testing we recommend Cuprite.

Thanks to Evrone design team. Read about Vessel & other projects supported by Evrone here.

Install

Add this to your Gemfile:

gem "vessel"

A look around

In order to show you how Vessel works we are going to crawl together famous quotes website:

require "json"
require "vessel"

class QuotesToScrapeCom < Vessel::Cargo
  domain "quotes.toscrape.com"
  start_urls "http://quotes.toscrape.com/tag/humor/"

  def parse
    css("div.quote").each do |quote|
      yield({
        author: quote.at_xpath("span/small").text,
        text: quote.at_css("span.text").text
      })
    end

    if next_page = at_xpath("//li[@class='next']/a[@href]")
      url = absolute_url(next_page.attribute(:href))
      yield request(url: url, method: :parse)
    end
  end
end

quotes = []
QuotesToScrapeCom.run { |q| quotes << q }
puts JSON.generate(quotes)

Save this to quotes.rb file and run bundle exec ruby quotes.rb > quotes.json. When this finishes you will have a list of the quotes in JSON format in the quotes.json file.

How it all works? First Vessel using Ferrum spawns Chrome which goes to one or more urls in start_urls, in our case it's only one. After Chrome reports back that page is loaded with all the resources it needs the first default callback parse is invoked. In the parse callback, we loop through the quote elements using a CSS Selector, yield a Hash with the extracted quote text and author and look for a link to the next page and schedule another request using the same parse method as callback.

Notice that all requests are scheduled and handled concurrently. We use thread pool to work with all your requests with one page per core by default or add threads max: n to a class. If you yield more than one request Ruby will send them to Chrome which will load pages in parallel. Thus crawler is lightweight and speedy.

Settings

• domain
• start_urls
• delay
• timeout
• threads
• middleware

Selectors

• at_css
• css
• at_xpath
• xpath

Middleware

To be continued

License

Copyright 2018-2020 Machinio

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.