Crawly
Overview
Crawly is an application framework for crawling web sites and extracting structured data which can be used for a wide range of useful applications, like data mining, information processing or historical archival.
Requirements
- Elixir
~> 1.10
- Works on GNU/Linux, Windows, macOS X, and BSD.
Quickstart
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Add Crawly as a dependencies:
# mix.exs defp deps do [ {:crawly, "~> 0.13.0"}, {:floki, "~> 0.26.0"} ] end
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Fetch dependencies:
$ mix deps.get
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Create a spider
# lib/crawly_example/books_to_scrape.ex defmodule BooksToScrape do use Crawly.Spider @impl Crawly.Spider def base_url(), do: "https://books.toscrape.com/" @impl Crawly.Spider def init() do: [start_urls: ["https://books.toscrape.com/"]] @impl Crawly.Spider def parse_item(response) do # Parse response body to document {:ok, document} = Floki.parse_document(response.body) # Create item (for pages where items exists) items = document |> Floki.find(".product_pod") |> Enum.map(fn x -> %{ title: Floki.find(x, "h3 a") |> Floki.attribute("title") |> Floki.text(), price: Floki.find(x, ".product_price .price_color") |> Floki.text(), } end) next_requests = document |> Floki.find(".next a") |> Floki.attribute("href") |> Enum.map(fn url -> Crawly.Utils.build_absolute_url(url, response.request.url) |> Crawly.Utils.request_from_url() end) %{items: items, requests: next_requests} end end
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Configure Crawly
By default, Crawly does not require any configuration. But obviously you will need a configuration for fine tuning the crawls:
# in config.exs config :crawly, closespider_timeout: 10, concurrent_requests_per_domain: 8, middlewares: [ Crawly.Middlewares.DomainFilter, Crawly.Middlewares.UniqueRequest, {Crawly.Middlewares.UserAgent, user_agents: ["Crawly Bot"]} ], pipelines: [ {Crawly.Pipelines.Validate, fields: [:url, :title]}, {Crawly.Pipelines.DuplicatesFilter, item_id: :title}, Crawly.Pipelines.JSONEncoder, {Crawly.Pipelines.WriteToFile, extension: "jl", folder: "/tmp"} ]
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Start the Crawl:
$ iex -S mix iex(1)> Crawly.Engine.start_spider(EslSpider)
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Results can be seen with:
$ cat /tmp/EslSpider.jl
Need more help?
I have decided to create a public telegram channel, so it's now possible to be connected, and it's possible to ask questions and get answers faster!
Please join me on: https://t.me/crawlyelixir
Browser rendering
Crawly can be configured in the way that all fetched pages will be browser rendered, which can be very useful if you need to extract data from pages which has lots of asynchronous elements (for example parts loaded by AJAX).
You can read more here:
Experimental UI
The CrawlyUI project is an add-on that aims to provide an interface for managing and rapidly developing spiders.
Checkout the code from GitHub or try it online CrawlyUIDemo
See more at Experimental UI
Documentation
Roadmap
- Pluggable HTTP client
- Retries support
- Cookies support
- XPath support - can be actually done with meeseeks
- Project generators (spiders)
- UI for jobs management
Articles
- Blog post on Erlang Solutions website: https://www.erlang-solutions.com/blog/web-scraping-with-elixir.html
- Blog post about using Crawly inside a machine learning project with Tensorflow (Tensorflex): https://www.erlang-solutions.com/blog/how-to-build-a-machine-learning-project-in-elixir.html
- Web scraping with Crawly and Elixir. Browser rendering: https://medium.com/@oltarasenko/web-scraping-with-elixir-and-crawly-browser-rendering-afcaacf954e8
- Web scraping with Elixir and Crawly. Extracting data behind authentication: https://oltarasenko.medium.com/web-scraping-with-elixir-and-crawly-extracting-data-behind-authentication-a52584e9cf13
- What is web scraping, and why you might want to use it?
- Using Elixir and Crawly for price monitoring
- Building a Chrome-based fetcher for Crawly
Example projects
- Blog crawler: https://github.com/oltarasenko/crawly-spider-example
- E-commerce websites: https://github.com/oltarasenko/products-advisor
- Car shops: https://github.com/oltarasenko/crawly-cars
- JavaScript based website (Splash example): https://github.com/oltarasenko/autosites
Contributors
We would gladly accept your contributions!
Documentation
Please find documentation on the HexDocs
Production usages
Using Crawly on production? Please let us know about your case!
Copyright and License
Copyright (c) 2019 Oleg Tarasenko
Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.