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Exoscan 4.0.1

Exoscan

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Overview

Declarative high performance web scraper, crawler and parser in C#. Designed as simple, declarative and scalable web scraping solution. Easily crawl any web site and parse the data, save structed result to a file, DB, or pretty much to anywhere you want.

It provides a simple yet extensible API to make web scraping a breeze.

Install

dotnet add package Exoscan

Requirements

.NET 6

📋 Example:

using Exoscan.Core.Builders;

_ = new ScraperEngineBuilder()
 .Get("https://www.reddit.com/r/dotnet/")
 .Follow("a.SQnoC3ObvgnGjWt90zD9Z._2INHSNB8V5eaWp4P0rY_mE")
 .Parse(new()
 {
 new("title", "._eYtD2XCVieq6emjKBH3m"),
 new("text", "._3xX726aBn29LDbsDtzr_6E._1Ap4F5maDtT1E1YuCiaO0r.D3IL3FD0RFy_mkKLPwL4")
 })
 .WriteToJsonFile("output.json")
 .LogToConsole()
 .Build()
 .Run();

Console.ReadLine();

Features:

• ⚡ It's extremly fast due to parallelism and asynchrony
• 🗒 Declarative parsing with a structured scheme
• 💾 Saving data to any sinks such as JSON or CSV file, MongoDB, CosmosDB, Redis, etc.
• 🌎 Distributed crawling support: run your web scraper on ony cloud VMs, serverless functions, on-prem servers, etc.
• 🐙 Crowling and parsing Single Page Applications with Puppeteer
• 🖥 Proxy support
• 🌀 Automatic reties

Usage examples

• Data mining
• Gathering data for machine learning
• Online price change monitoring and price comparison
• News aggregation
• Product review scraping (to watch the competition)
• Gathering real estate listings
• Tracking online presence and reputation
• Web mashup and web data integration
• MAP compliance
• Lead generation

API overview

SPA parsing example

Parsing single page applications is super simple, just use the GetWithBrowser and/or FollowWithBrowser method. In this case Puppeteer will be used to load the pages.

_ = new ScraperEngineBuilder()
 .GetWithBrowser("https://www.reddit.com/r/dotnet/")
 .Follow("a.SQnoC3ObvgnGjWt90zD9Z._2INHSNB8V5eaWp4P0rY_mE")
 .Parse(new()
 {
 new("title", "._eYtD2XCVieq6emjKBH3m"),
 new("text", "._3xX726aBn29LDbsDtzr_6E._1Ap4F5maDtT1E1YuCiaO0r.D3IL3FD0RFy_mkKLPwL4")
 })
 .WriteToJsonFile("output.json")
 .LogToConsole()
 .Build()
 .Run(1);

Additionaly, you can run any JavaScript on dynamic pages as they are loaded with headless browser. In order to do that you need to add some page actions:

using Exoscan.Core.Builders;

_ = new ScraperEngineBuilder()
 .GetWithBrowser("https://www.reddit.com/r/dotnet/", actions => actions
 .ScrollToEnd()
 .Build())
 .Follow("a.SQnoC3ObvgnGjWt90zD9Z._2INHSNB8V5eaWp4P0rY_mE")
 .Parse(new()
 {
 new("title", "._eYtD2XCVieq6emjKBH3m"),
 new("text", "._3xX726aBn29LDbsDtzr_6E._1Ap4F5maDtT1E1YuCiaO0r.D3IL3FD0RFy_mkKLPwL4")
 })
 .WriteToJsonFile("output.json")
 .LogToConsole()
 .Build()
 .Run(1);

Console.ReadLine();

It can be helpful if the required content is loaded only after some user interactions such as clicks, scrolls, etc.

Persist the progress locally

If you want to persist the vistited links and job queue locally, so that you can start crawling where you left off you can use ScheduleWithTextFile and TrackVisitedLinksInFile methods:

var engine = new ScraperEngineBuilder()
 .WithLogger(logger)
 .Get("https://rutracker.org/forum/index.php?c=33")
 .Follow("#cf-33 .forumlink>a")
 .Follow(".forumlink>a")
 .Paginate("a.torTopic", ".pg")
 .Parse(new()
 {
 new("name", "#topic-title"),
 new("category", "td.nav.t-breadcrumb-top.w100.pad_2>a:nth-child(3)"),
 new("subcategory", "td.nav.t-breadcrumb-top.w100.pad_2>a:nth-child(5)"),
 new("torrentSize", "div.attach_link.guest>ul>li:nth-child(2)"),
 new("torrentLink", ".magnet-link", "href"),
 new("coverImageUrl", ".postImg", "src")
 })
 .WriteToJsonFile("result.json")
 .IgnoreUrls(blackList)
 .ScheduleWithTextFile("jobs.txt", "progress.txt")
 .TrackVisitedLinksInFile("links.txt")
 .Build();

Authorization

If you need to pass authorization before parsing the web site, you can call SetCookies method on Scraper that has to fill CookieContainer with all cookies required for authorization. You are responsible for performing the login operation with your credentials, the Scraper only uses the cookies that you provide.

_ = new ScraperEngineBuilder()
 .WithLogger(logger)
 .Get("https://rutracker.org/forum/index.php?c=33")
 .SetCookies(cookies =>
 {
 cookies.Add(new Cookie("AuthToken", "123");
 })

Distributed web scraping with Serverless approach

In the Examples folder you can find the project called Exoscan.AzureFuncs. It demonstrates the use of Exoscan with Azure Functions. It consists of two serverless functions:

StartScrapting

First of all, this function uses ScraperConfigBuilder to build the scraper configuration e. g.:

Secondly, this function writes the first web scraping job with startUrl to the Azure Service Bus queue:

ExoscanSpider

This Azure function is triggered by messages sent to the Azure Service Bus queue. Messages represent web scraping job.

Firstly, this function builds the spider that is going to execute the job from the queue.

Secondly, it executes the job by loading the page, parsing content, saving to the database, etc.

Finally, it iterates through these new jobs and sends them the the Job queue.

Extensibility

Adding a new sink to persist your data

Out of the box there are 4 sinks you can send your parsed data to: ConsoleSink, CsvFileSink, JsonFileSink, CosmosSink (Azure Cosmos database).

You can easly add your own by implementing the IScraperSink interface:

public interface IScraperSink
{
 public Task EmitAsync(ParsedData data);
}

Here is an example of the Console sink:

public class ConsoleSink : IScraperSink
{
 public Task EmitAsync(ParsedData parsedItam)
 {
 Console.WriteLine($"{parsedItam.Data.ToString()}");
 return Task.CompletedTask;
 }
}

Adding your sink to the Scraper is simple, just call AddSink method on the Scraper:

_ = new ScraperEngineBuilder()
 .AddSink(new ConsoleSink());
 .Get("https://rutracker.org/forum/index.php?c=33")
 .Follow("#cf-33 .forumlink>a")
 .Follow(".forumlink>a")
 .Paginate("a.torTopic", ".pg")
 .Parse(new() {
 new("name", "#topic-title"),
 });

For other ways to extend your functionality see the next section.

Intrefaces

Main entities

• Job - a record that represents a job for the spider
• LinkPathSelector - represents a selector for links to be crawled

Repository structure

Coming soon:

• Nuget package
• Azure functions for the distributed crawling
• Loading pages with headless browser and flexible SPA page manipulations (clicks, scrolls, etc)
• Proxy support
• Add caching of html pages
• Add flexible conditions for ignoring or allowing certain pages
• Breadth first traversal with priority channels
• Save auth cookies to redis, mongo, etc.
• Separate nuget packages for MaongoDb, Cosmos Db, Redis, etc.
• Sitemap crawling support
• Add LogTo method with Console and File support

Features under consideration

• Request auto throttling
• Add bloom filter for revisiting same urls
• Simplify ExoscanSpider class
• Subscribe to logs with lambda expression

See the file for license rights and limitations (GNU GPLv3).