Awesome
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.
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 "https://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, handler: :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 handler
parse
is invoked. In the parse handler, 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 a handler.
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
- driver
- delay
- headers
- cookies
- threads
- middleware
- proxy
- blacklist
- whitelist
Headers
class MyScraper < Vessel::Cargo
headers "Content-Type" => "text/plain",
"Referer" => "http://example.com"
end
Headful mode
You can disable headless mode by passing driver_options
settings:
MyScraper.run(driver_options: { headless: false })
Selectors
- at_css
- css
- at_xpath
- xpath
Middleware
To be continued
License
The gem is available as open source under the terms of the MIT License.