arachnod

Arachnod

High performance crawler for Nodejs

Powerful & Easy to use web crawler for Nodejs. Arachnod has been designed for heavy and long running tasks, for performance & efective resource usage. For it's goals Arachnod uses Redis's power as a backend. Covering all heavy & time consuming tasks such as controlling urls & their tasks to store & distribute information among the Arachnod's child tasks (Spiderlings). Arachnod also avoids to use any server-side DOM requiring technics such as jQuery with JSdom to use resources properly. Frankly, I have tested JSdom for along time with no luck, always memory leaks & high memory usage. Libxml based XPath solutions were not actually real, Instead, Arachnod uses Cheerio for accessing DOM elements. Also uses SuperAgent as HTTP Client.

How to install

$ npm install arachnod

Or via Git $ git clone [e-mail]:risyasin/arachnod.git

Then, install required Nodejs modules with npm $ npm install

Please make sure you have a running redis-server

How to use

var bot = require('arachnod');
    
bot.on('hit', function (doc, $) {
    
    // Do whatever you want to do parsed html content.
    
    var desc = $('article.entry-content').text();
    
    console.log(doc.path, desc);
    
    // if you don't need to follow all links.
    bot.pause();
    
    
});


bot.crawl({
    'redis': '127.0.0.1',
    'parallel': 4,
    'start': 'https://github.com/risyasin/arachnod',
    'resume': false
});


bot.on('error', function (err, task) {
    console.log('Bot error:', err, err.stack, task);
});


bot.on('end', function (err, status) {
    console.log('Bot finished:', err, status);
});

Documentation

Parameters

Parameter Name	Description
start	Start url for crawling (Mandatory)
parallel	Number of child processes that will handle network tasks (Default: 8) Do not this more than 20.
redis	Host name or IP address that Redis runs on (Default: 127.0.0.1)
redisPort	Port number for Redis (Default: 6379)
verbose	Arachnod will tell you more, 1 (silence) - 10 (everything). Default: 1.
resume	Resume support, Simply, does not resets queues if there is any. (Default: false)
ignorePaths	Ignores paths starts with. Must be multiple in array syntax such as ['/blog','/gallery']
ignoreParams	Ignores query string parameters, Must be in array syntax. such as ['color','type']
sameDomain	Stays in the same hostname. (will be implemented at v1)
useCookies	Using cookies (will be implemented at v0.4)
obeyRobotsTxt	As it's name says. Honors the robots.txt (will be implemented at v0.5)

Events

Event Name	Description
hit	Emits when a url has been downloaded & processed, sends two parameters in order doc Parsed url info, $ as Cheerio object.
error	Emits when an error occurs at any level including child processes. Single parameter Error or Exception.
end	Emits when reached at the end of tasks queue. Return statistics.
stats	Emits bot stats whenever a child changes it's states (such as downloading or querying queues). Use wisely.

Methods

Method Name	Description
crawl(Parameters)	Starts a new crawling session with parameters
pause()	Stops bot but does not delete any task queue.
resume()	Starts back a paused session. Useful to control resource usage in low spec systems (single core etc.).
queue(url)	Adds given url to task queue.
getStats()	Returns various statistics such as downloaded, checked, finished url counts, memory size etc.

What's Next

• Regex support for ignore parameters
• Cookie support
• Robots.txt & rel=nofollow support
• Actions for content-type or any given response headers
• Custom headers
• Custom POST/PUT method queues
• Free-Ride mode (will be fun)
• Stats for each download/hit event
• Plugin support

Support

If you love to use Arachnod. Help me to improve it. Feel free to make pull request for anything useful.

License

Copyright 2015 yasin inat

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.