https://github.com/nietaki/crawlie

A simple Elixir library for writing decently-performing crawlers with minimum effort.
https://github.com/nietaki/crawlie

crawler elixir elixir-library genstage

Last synced: about 1 month ago
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A simple Elixir library for writing decently-performing crawlers with minimum effort.

• Host: GitHub
• URL: https://github.com/nietaki/crawlie
• Owner: nietaki
• License: mit
• Created: 2016-12-11T15:42:59.000Z (about 8 years ago)
• Default Branch: master
• Last Pushed: 2021-10-30T00:04:43.000Z (about 3 years ago)
• Last Synced: 2024-11-09T19:41:18.873Z (about 2 months ago)
• Topics: crawler, elixir, elixir-library, genstage
• Language: Elixir
• Homepage:
• Size: 196 KB
• Stars: 89
• Watchers: 5
• Forks: 11
• Open Issues: 8
• Metadata Files:
  • Readme: README.md
  • Changelog: CHANGELOG.md
  • License: LICENSE.txt

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README

        
# Crawlie (the crawler) [![badge](https://travis-ci.org/nietaki/crawlie.svg?branch=master)](https://travis-ci.org/nietaki/crawlie) [![Coverage Status](https://coveralls.io/repos/github/nietaki/crawlie/badge.svg?branch=master)](https://coveralls.io/github/nietaki/crawlie?branch=master) [![Hex.pm](https://img.shields.io/hexpm/v/crawlie.svg)](https://hex.pm/packages/crawlie) [![docs](https://img.shields.io/badge/docs-hexdocs-yellow.svg)](https://hexdocs.pm/crawlie/) [![Built with Spacemacs](https://cdn.rawgit.com/syl20bnr/spacemacs/442d025779da2f62fc86c2082703697714db6514/assets/spacemacs-badge.svg)](http://spacemacs.org)

Crawlie is a simple Elixir library for writing decently-performing crawlers with minimum effort.

## Usage example

See the [crawlie_example](https://github.com/nietaki/crawlie_example) project.

## Inner workings

Crawlie uses Elixir's [GenStage](https://github.com/elixir-lang/gen_stage) to parallelise

the work. Most of the logic is handled by the `Crawlie.Stage.UrlManager`, which consumes the url collection passed by the user, receives the urls extracted by the subsequent processing, makes sure no url is processed more than once, makes sure that the "discovered urls" collection is as small as possible by traversing the url tree in a roughly depth-first manner.

The urls are requested from the `Crawlie.Stage.UrlManager` by a GenStage [Flow](https://hexdocs.pm/flow/Flow.html#content), which in parallel

fetches the urls using HTTPoison, and parses the responses using user-provided callbacks. Discovered urls get sent back to UrlManager.

Here's a rough diagram:

![crawlie architecture diagram](assets/crawlie_arch_v0.2.0.png)

## Statistics

If you're interested in the crawling statistics or want to track the progress in real time, see [`Crawlie.crawl_and_track_stats/3`](https://hexdocs.pm/crawlie/Crawlie.html#crawl_and_track_stats/3). It starts a [`Stats GenServer`](https:/hexdocs.pm/crawlie/Crawlie.Stats.Server.html) in Crawlie's supervision tree, which accumulates the statistics for the crawling session.

## Configuration

See [the docs](https://hexdocs.pm/crawlie/Crawlie.html#crawl/3) for supported options.

## Installation

The package can be installed as:

  1. Add `crawlie` to your list of dependencies in `mix.exs`:

```elixir

def deps do

  [{:crawlie, "~> 1.0.0"}]

end

```

  2. Ensure `crawlie` is started before your application:

```elixir

def application do

  [applications: [:crawlie]]

end

```