Does Pholcus provide support for rotating user agents?

Pholcus is a distributed, high-concurrency and powerful web crawler software written in the Go language. It is designed to handle a variety of crawl needs, from simple to complex. One of the common requirements for web crawlers is the ability to rotate user agents, which can help in evading detection by websites that may block or throttle crawlers.

Pholcus itself does not provide a built-in feature specifically named "rotating user agents". However, because Pholcus is highly customizable and extensible, you can implement user agent rotation yourself within the framework.

To rotate user agents in Pholcus, you can maintain a list of user agent strings and then select one at random (or in a predefined order) to use for each request. Below is a conceptual example of how you could implement user agent rotation in Go using Pholcus. Please note that this is a simplified example for illustration purposes, and actual implementation details may vary based on the version of Pholcus you are using and your specific requirements.

package main

import (
    "github.com/henrylee2cn/pholcus/exec"
    "github.com/henrylee2cn/pholcus/spiders"
    "github.com/henrylee2cn/pholcus/web"
    "math/rand"
    "time"
)

// List of user agents to rotate
var userAgents = []string{
    "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/58.0.3029.110 Safari/537.3",
    "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_5) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/13.1.1 Safari/605.1.15",
    // Add more user agents as needed
}

func main() {
    // Set up Pholcus to run your spiders, etc.

    // Random seed for user agent rotation
    rand.Seed(time.Now().UnixNano())

    // Register your spider(s)
    spiders.Register()

    // Run Pholcus as a web server
    web.Run()
}

// RotateUserAgent selects a random user agent from the list
func RotateUserAgent() string {
    return userAgents[rand.Intn(len(userAgents))]
}

// Example usage within a spider or a request
// req := &request.Request{
//     Url:        "http://example.com",
//     Method:     "GET",
//     Header:     http.Header{"User-Agent": []string{RotateUserAgent()}},
//     // Other fields...
// }

In this example, we have a userAgents slice that contains several user agent strings. The RotateUserAgent function selects a random user agent from this list using the rand package. You would call RotateUserAgent wherever you're setting up your requests within your Pholcus spiders to set the User-Agent header.

Keep in mind that websites may use various techniques to detect web scraping activities, so rotating user agents is just one of many strategies that might be employed to avoid detection. It's also important to respect the website's robots.txt file and terms of service. Additionally, you should implement proper error handling and possibly rate limiting to ensure your web crawler behaves responsibly.