Is there a way to limit the rate of requests with Scraper (Rust)?

Yes, you can limit the rate of requests when using a web scraping library in Rust, such as scraper. However, scraper itself is primarily a HTML parsing library and does not directly provide functionality for making HTTP requests or controlling the rate of these requests.

To control the rate of requests, you would typically use a combination of scraper for parsing the HTML content and another library such as reqwest for making HTTP requests, along with some rate-limiting logic.

Here's a basic example of how you might implement rate limiting with reqwest and scraper in Rust:

use reqwest;
use scraper::{Html, Selector};
use std::thread;
use std::time::Duration;

async fn fetch_html(url: &str) -> Result<String, reqwest::Error> {
    // Make an HTTP GET request to the specified URL
    let res = reqwest::get(url).await?;
    // Return the text of the response
    res.text().await
}

async fn process_url(url: &str) {
    if let Ok(html) = fetch_html(url).await {
        // Parse the HTML document
        let document = Html::parse_document(&html);
        let selector = Selector::parse("a").unwrap();
        for element in document.select(&selector) {
            if let Some(href) = element.value().attr("href") {
                println!("Found link: {}", href);
            }
        }
    } else {
        println!("Failed to fetch {}", url);
    }
}

#[tokio::main]
async fn main() {
    // List of URLs to scrape
    let urls = vec![
        "http://example.com",
        "http://example.org",
        "http://example.net",
    ];

    // Delay between requests
    let delay = Duration::from_secs(1);

    for url in urls {
        process_url(url).await;
        // Sleep for the specified delay duration
        thread::sleep(delay);
    }
}

In this example:

• We use the reqwest library to make HTTP GET requests asynchronously.
• We use the scraper library to parse and extract information from the HTML response.
• We apply a fixed delay between requests using thread::sleep(delay) to limit the rate of requests.

Please note that this is a very simple rate-limiting mechanism. In a real-world scenario, you might want to implement more sophisticated rate limiting, which could include:

• Respecting the robots.txt file of the website.
• Implementing exponential backoff in case of server errors or rate limit responses (HTTP status 429).
• Using a more advanced rate-limiting library or creating a custom rate limiter with features like token bucket or leaky bucket algorithms.

When scraping websites, always be mindful of the website's terms of service and ensure that your scraping activities do not overload the server or violate any rules set by the site owner.