Golang Colly: How to Use & Rotate Proxies

In this guide for The Golang Web Scraping Playbook, we will look at how to integrate the 3 most common types of proxies into our Go Colly based web scraper.

Using proxies with the Go Colly library allows you to spread your requests over multiple IP addresses making it harder for websites to detect & block your web scrapers.

In this guide we will walk you through the 3 most common proxy integration methods and show you how to use them with Go Colly:

• Using Proxy IPs With Go Colly
• Proxy Authentication With Go Colly
• The 3 Most Common Proxy Formats
• Proxy Integration #1: Rotating Through Proxy IP List
• Proxy Integration #2: Using Proxy Gateway
• Proxy Integration #3: Using Proxy API Endpoint

Let's begin...

Using Proxy IPs With Go Colly​

Using a proxy with Go Colly is very straight forward. We simply need to set a proxy on the collector using the SetProxy() method.

package main

import (
	"bytes"
	"log"
	"github.com/gocolly/colly"
)

func main() {
	// Instantiate default collector
	c := colly.NewCollector(colly.AllowURLRevisit())

	// Set Proxy
	c.SetProxy("http://proxy.example.com:8080")

	// Print the Response
	c.OnResponse(func(r *colly.Response) {
		log.Printf("%s\n", bytes.Replace(r.Body, []byte("\n"), nil, -1))
	})

	// On Error Print Error
	c.OnError(func(_ *colly.Response, err error) {
		log.Println("Something went wrong:", err)
	})

	// Request Page
	c.Visit("http://httpbin.org/ip")
}

This method will work for all request methods Go Colly supports: GET, POST, PUT, DELETE, PATCH, HEAD.

Proxy Authentication With Go Colly​

To authenticate a proxy using a username and password we simply need to add the username and password to the proxy strings.

package main

import (
	"bytes"
	"log"
	"github.com/gocolly/colly"
)

func main() {
	// Instantiate default collector
	c := colly.NewCollector(colly.AllowURLRevisit())

	// Set Proxy
	c.SetProxy("http://USERNAME:PASSWORD@proxy.example.com:8080")

	// Print the Response
	c.OnResponse(func(r *colly.Response) {
		log.Printf("%s\n", bytes.Replace(r.Body, []byte("\n"), nil, -1))
	})

	// On Error Print Error
	c.OnError(func(_ *colly.Response, err error) {
		log.Println("Something went wrong:", err)
	})

	// Request Page
	c.Visit("http://httpbin.org/ip")
}

The 3 Most Common Proxy Formats​

That covered the basics of integrating a proxy into Go Colly, in the next sections we will show you how to integrate Go Colly into the 3 most common proxy formats:

• Rotating Through List of Proxy IPs
• Using Proxy Gateways
• Using Proxy APIs

A couple years ago, proxy providers would sell you a list of proxy IP addresses and you would configure your scraper to rotate through these IP addresses and use a new one with each request.

However, today more and more proxy providers don't sell raw lists of proxy IP addresses anymore. Instead providing access to their proxy pools via proxy gateways or proxy API endpoints.

We will look at how to integrate with all 3 proxy formats.

Proxy Integration #1: Rotating Through Proxy IP List​

Here a proxy provider will normally provide you with a list of proxy IP addresses that you will need to configure your scraper to rotate through and select a new IP address for every request.

The proxy list you recieve will look something like this:

'http://Username:Password@85.237.57.198:20000',
'http://Username:Password@85.237.57.198:21000',
'http://Username:Password@85.237.57.198:22000',
'http://Username:Password@85.237.57.198:23000',

To integrate them into our Go Colly scraper we can use Go Colly's Proxy Switcher functionality. First we need to install Proxy Switcher.

go get github.com/gocolly/colly/proxy

Next, create a rotating proxy instance and add this to our collector using the SetProxyFunc().

package main

import (
	"bytes"
	"log"
	"github.com/gocolly/colly"
	"github.com/gocolly/colly/proxy"
)

func main() {
	// Instantiate default collector
	c := colly.NewCollector(colly.AllowURLRevisit())


	proxyList := []string{
		"http://Username:Password@85.237.57.198:20000",
      "http://Username:Password@85.237.57.198:21000",
      "http://Username:Password@85.237.57.198:22000",
      "http://Username:Password@85.237.57.198:23000",
	}

	// Create Rotating Proxy Switcher
	rp, err := proxy.RoundRobinProxySwitcher(proxyList...)
	if err != nil {
		log.Fatal(err)
	}

   // Set Collector To Use Proxy Switcher Function
	c.SetProxyFunc(rp)

	// Print the Response
	c.OnResponse(func(r *colly.Response) {
		log.Printf("%s\n", bytes.Replace(r.Body, []byte("\n"), nil, -1))
	})

	// On Error Print Error
	c.OnError(func(_ *colly.Response, err error) {
		log.Println("Something went wrong:", err)
	})

	// Fetch httpbin.org/ip five times
	for i := 0; i < 5; i++ {
		c.Visit("http://httpbin.org/ip")
	}
}

This is a simplistic example, as when scraping at scale we would also need to build a mechanism to monitor the performance of each individual IP address and remove it from the proxy rotation if it got banned or blocked.

Proxy Integration #2: Using Proxy Gateway​

Increasingly, a lot of proxy providers aren't selling lists of proxy IP addresses anymore. Instead, they give you access to their proxy pools via a proxy gateway.

Here, you only have to integrate a single proxy into your Go Colly scraper and the proxy provider will manage the proxy rotation, selection, cleaning, etc. on their end for you.

This is the most common way to use residential and mobile proxies, and becoming increasingly common when using datacenter proxies too.

Here is an example of how to integrate a BrightData's residential proxy gateway into our Go Colly scraper:

package main

import (
	"bytes"
	"log"
	"github.com/gocolly/colly"
)

func main() {
	// Instantiate default collector
	c := colly.NewCollector(colly.AllowURLRevisit())

	// Set Proxy
	c.SetProxy("http://zproxy.lum-superproxy.io:22225")

	// Print the Response
	c.OnResponse(func(r *colly.Response) {
		log.Printf("%s\n", bytes.Replace(r.Body, []byte("\n"), nil, -1))
	})

	// On Error Print Error
	c.OnError(func(_ *colly.Response, err error) {
		log.Println("Something went wrong:", err)
	})

	// Request Page
	c.Visit("http://httpbin.org/ip")
}

As you can see, it is easier to integrate than using a proxy list as you don't have to worry about implementing all the proxy rotation logic.

Proxy Integration #3: Using Proxy API Endpoint​

Recently, a lot of proxy providers have started offering smart proxy APIs that take care of managing your proxy infrastructure for you by rotating proxies and headers for you so you can focus on extracting the data you need.

Here you typically, send the URL you want to scrape to their API endpoint and then they will return the HTML response.

Although every proxy API provider has a slightly different API integration, they are all very similar and are very easy to integrate with.

Here is an example of how to integrate with the ScrapeOps Proxy Manager:

package main

import (
	"bytes"
	"log"
	"github.com/gocolly/colly"
	"net/url"
)

func main() {
	// Instantiate default collector
	c := colly.NewCollector(colly.AllowURLRevisit())

	// Print the Response
	c.OnResponse(func(r *colly.Response) {
		log.Printf("%s\n", bytes.Replace(r.Body, []byte("\n"), nil, -1))
	})

	// On Error Print Error
	c.OnError(func(_ *colly.Response, err error) {
		log.Println("Something went wrong:", err)
	})

	// Create Proxy API URL
	u, err := url.Parse("https://proxy.scrapeops.io/v1/")
	if err != nil {
		log.Fatal(err)
	}

	// Add Query Parameters
	q := u.Query()
	q.Set("api_key", "YOUR_API_KEY")
	q.Set("url", "http://httpbin.org/ip")
	u.RawQuery = q.Encode()

	// Request Page
	c.Visit(u.RawQuery)
}

Here you simply send the URL you want to scrape to the ScrapeOps API endpoint in the url query parameter, along with your API key in the api_key query parameter, and ScrapeOps will deal with finding the best proxy for that domain and return the HTML response to you.

You can get your own free API key with 1,000 free requests by signing up here.

More Web Scraping Tutorials​

So that's how you can integrate proxies into your Go Colly scrapers.

If you would like to learn more about Web Scraping, then be sure to check out The Web Scraping Playbook.

Or check out one of our more in-depth guides:

• How to Scrape The Web Without Getting Blocked Guide
• The State of Web Scraping 2020
• The Ethics of Web Scraping