Gonzo Proxy

Such proxy redirects requests from clients to different servers (globally or within a single local network). It can be used for load balancing in different Internet services, for testing web applications, for secured access to local network servers (all "non-client" traffic is ignored).

It seems there might be a confusion in your request. Polly is a resilience and transient-fault-handling library in C# for dealing with issues like network failures, timeouts, and other transient errors. It is not directly related to parsing courses or web scraping.

If you are looking to parse a course from a website using C#, you might want to use a combination of HTTP requests and HTML parsing libraries. Here's a basic example using the HtmlAgilityPack library for HTML parsing and HttpClient for making HTTP requests

Install HtmlAgilityPack:

You can install the HtmlAgilityPack library using NuGet Package Manager Console:

Install-Package HtmlAgilityPack

Example Code

Here's a simple example of how you might use HttpClient and HtmlAgilityPack to parse course information from a website:

using System;
using System.Net.Http;
using HtmlAgilityPack;

class Program
{
    static async System.Threading.Tasks.Task Main(string[] args)
    {
        // URL of the course page
        string courseUrl = "https://example.com/courses";

        // Make an HTTP request to get the HTML content
        using (HttpClient client = new HttpClient())
        {
            string htmlContent = await client.GetStringAsync(courseUrl);

            // Use HtmlAgilityPack to parse the HTML
            HtmlDocument doc = new HtmlDocument();
            doc.LoadHtml(htmlContent);

            // Extract course information (modify as per the HTML structure)
            HtmlNodeCollection courseNodes = doc.DocumentNode.SelectNodes("//div[@class='course']");
            if (courseNodes != null)
            {
                foreach (HtmlNode courseNode in courseNodes)
                {
                    string courseTitle = courseNode.SelectSingleNode(".//h2")?.InnerText.Trim();
                    string courseDescription = courseNode.SelectSingleNode(".//p")?.InnerText.Trim();

                    Console.WriteLine($"Title: {courseTitle}");
                    Console.WriteLine($"Description: {courseDescription}");
                    Console.WriteLine();
                }
            }
            else
            {
                Console.WriteLine("No course information found on the page.");
            }
        }
    }
}

This is a basic example, and you'll need to adapt it based on the actual HTML structure of the course page you are working with.

Distributing scraping correctly involves implementing techniques to handle rate limiting, avoid overloading servers, and ensuring your scraping activities are respectful and compliant with the website's terms of service. If you're encountering 503 errors (Service Unavailable), it likely indicates that the server is overwhelmed or intentionally blocking excessive requests. Here are some strategies to address this issue:

1. Add Delays Between Requests:

   • Introduce delays between your requests to avoid hitting the server too quickly. This is commonly known as "throttling" your requests.
   • Use libraries like puppeteer (for headless browser scraping) or p-queue to manage the rate of your requests.

2. Randomize Delays:

   • Instead of using fixed delays, consider randomizing them to mimic more natural user behavior.
   • This helps in avoiding detection and mitigation mechanisms that are triggered by constant patterns.

3. Use Proxies:

   • Rotate IP addresses using proxies to distribute requests across multiple IP addresses.
   • This can help overcome IP-based rate limiting or blocking.

4. Implement User Agents:

   • Use a variety of user agents to simulate requests from different browsers and devices.
   • Websites often have different policies for different types of clients.

5. Respect robots.txt:

   • Check the robots.txt file of the website to understand which parts of the site are off-limits for scraping.
   • Avoid scraping prohibited areas mentioned in robots.txt.

6. Session Management:

   • Use session management techniques to maintain a persistent session when scraping across multiple requests.
   • Some websites may have protection mechanisms based on session data.

7. Handle Captchas:

   • Be prepared to handle captchas if the website employs them to detect automated scraping.
   • Consider using tools like CAPTCHA solving services if necessary.

8. Error Handling:

   • Implement robust error handling to deal with different HTTP status codes.
   • Log errors and adjust your scraping strategy accordingly.

9. Reduce Concurrent Requests:

   • Limit the number of concurrent requests to avoid overwhelming the server.
   • Use libraries like p-queue to control concurrency.

10. Monitor and Adjust:

    • Continuously monitor your scraping activities and adjust your strategy based on the website's response.
    • If you receive a 503 error, consider backing off and retrying after a delay.

Remember, it's essential to respect the website's terms of service and not engage in aggressive scraping practices that could negatively impact the site. If you continue to encounter issues, consider reaching out to the website's administrators to seek permission or explore alternative data sources or APIs if available.

You need to open the settings menu, go to "Data and disk", and then - "Proxy settings". There you can enter the address, port number of the intermediate server, as well as username and password for authorization (if necessary).

It means a private proxy server used by several users. For example, one of them has bought a paid proxy and lets his friend use it for a fee. That is, he "shared" his proxy (shared means "common").