Concurrent Web Scraper in Go

A concurrent web scraper that extracts links from a list of URLs.

Features:

• Concurrency: Utilizes goroutines and channels to fetch and process web pages concurrently, improving efficiency.
• Worker Pool: Employs a worker pool pattern to control the number of concurrent requests and avoid overloading the target websites.
• Link Extraction: Extracts all links (<a> tags) from the HTML source code of the web pages.
• Absolute URLs: Resolves relative links to absolute URLs using the base URL of each page.
• Synchronization: Uses sync.WaitGroup to synchronize the worker goroutines and ensure proper execution order.

How it works:

1. Worker Pool: A fixed number of worker goroutines are launched.
2. URL Distribution: The URLs to be scraped are sent to the workers through a channel (urlChan).
3. Fetching and Parsing: Each worker fetches a URL, parses the HTML content using golang.org/x/net/html, and extracts the links.
4. Absolute URL Conversion: Relative links are converted to absolute URLs using the base URL of the page.
5. Result Collection: The extracted links are sent back to the main goroutine through a channel (results).
6. Output: The main goroutine collects and prints the extracted links.

Concurrency Mechanisms:

• Goroutines: Enable concurrent execution of the worker functions.
• Channels: Facilitate communication and data transfer between goroutines.
• sync.WaitGroup: Used to wait for all worker goroutines to finish before closing the results channel.

Usage:

1. Make sure you have Go installed on your system.
2. Save the code as a .go file (e.g., scraper.go).
3. edit the list of URLs to fetch
4. Run the program using go run scraper.go.

Dependencies:

• golang.org/x/net/html: For HTML parsing.

Example Usage:

The program currently scrapes the following URLs:

• "https://google.com"
• "https://old.reddit.com/"
• "https://timevko.website"

You can modify the urls slice in the main function to scrape different websites.

Potential Improvements:

• Error Handling: More robust error handling for network requests and HTML parsing.
• Politeness: Implement delays between requests to avoid overloading the target servers.
• Data Storage: Store the extracted links in a file or database.
• Command-line Arguments: Allow users to specify the URLs and other options through command-line arguments.
• Deduplication: Remove duplicate links from the output.
• Advanced Extraction: Use CSS selectors (e.g., with the goquery library) for more specific link extraction.