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Go Web Scraping Quick Start Guide

By : Smith

3.5 (2)

Go Web Scraping Quick Start Guide

3.5 (2)

By: Smith

Overview of this book

Web scraping is the process of extracting information from the web using various tools that perform scraping and crawling. Go is emerging as the language of choice for scraping using a variety of libraries. This book will quickly explain to you, how to scrape data data from various websites using Go libraries such as Colly and Goquery. The book starts with an introduction to the use cases of building a web scraper and the main features of the Go programming language, along with setting up a Go environment. It then moves on to HTTP requests and responses and talks about how Go handles them. You will also learn about a number of basic web scraping etiquettes. You will be taught how to navigate through a website, using a breadth-first and then a depth-first search, as well as find and follow links. You will get to know about the ways to track history in order to avoid loops and to protect your web scraper using proxies. Finally the book will cover the Go concurrency model, and how to run scrapers in parallel, along with large-scale distributed web scraping.

Preface

Preface

Who this book is for

What this book covers

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Free Chapter

Introducing Web Scraping and Go

Introducing Web Scraping and Go

What is web scraping?

Why do you need a web scraper?

What is Go?

Why is Go a good fit for web scraping?

How to set up a Go development environment

Summary

The Request/Response Cycle

The Request/Response Cycle

What do HTTP requests look like?

What do HTTP responses look like?

What are HTTP status codes?

What do HTTP requests/responses look like in Go?

Summary

Web Scraping Etiquette

Web Scraping Etiquette

What is a robots.txt file?

What is a User-Agent string?

How to throttle your scraper

How to use caching

Summary

Parsing HTML

Parsing HTML

What is the HTML format?

Searching using the strings package

Searching using the regexp package

Searching using XPath queries

Searching using Cascading Style Sheets selectors

Summary

Web Scraping Navigation

Web Scraping Navigation

Following links

Submitting forms

Avoiding loops

Breadth-first versus depth-first crawling

Navigating with JavaScript

Summary

Protecting Your Web Scraper

Protecting Your Web Scraper

Virtual private servers

Proxies

Virtual private networks

Boundaries

Summary

Scraping with Concurrency

Scraping with Concurrency

What is concurrency

Concurrency pitfalls

The Go concurrency model

sync package helpers

Summary

Scraping at 100x

Scraping at 100x

Components of a web scraping system

Scraping HTML pages with colly

Scraping JavaScript pages with chrome-protocol

Distributed scraping with dataflowkit

Summary

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What is a User-Agent string?

When an HTTP client makes a request to a web server, they identify who they are. This holds true for web scrapers and normal browsers alike. Have you ever wondered why a website knows that you are a Windows or a Mac user? This information is contained inside your User-Agent string. Here is an example User-Agent string for a Firefox browser on a Linux computer:

Mozilla/5.0 (X11; Linux x86_64; rv:57.0) Gecko/20100101 Firefox/57.0

You can see that this string identifies the family, name, and version of the web browser, as well as the operating system. This string will be sent with every request from this browser inside of a request header, such as the following:

GET /index.html HTTP/1.1
Host: example.com
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:57.0) Gecko/20100101 Firefox/57.0

Not all User-Agent strings contain this much information. HTTP clients...

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