To design a web crawler that avoids detection, I would first clarify the scope: the volume of data, the number of machines available, and the timeframe. Key detection vectors include traffic volume, request frequency, and user-agent strings. My design would address these by:
- Rate Limiting and Politeness: Implementing delays between requests and respecting
robots.txt to avoid overwhelming the server.
- User-Agent Rotation: Using a diverse set of realistic user-agent strings to mimic different browsers and devices.
- IP Rotation: Employing proxies or a distributed network to spread requests across multiple IP addresses.
- Handling Dynamic Content: Utilizing headless browsers (like Puppeteer or Selenium) for JavaScript-heavy sites.
- Error Handling and Retries: Gracefully managing network errors and temporary blocks with exponential backoff.
- Data Storage: Designing an efficient storage solution for the downloaded content.
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