An incremental web crawler handles cross-domain requests in web pages by identifying and processing links that point to external domains while respecting crawl policies and performance constraints. Here's how it works:
Link Extraction: The crawler parses the HTML of a page and extracts all hyperlinks (<a>, <img>, <script>, etc.). It separates internal links (same domain) from external links (cross-domain).
Domain Filtering: The crawler checks if a link belongs to the same domain as the seed URL or a predefined list of allowed domains. Cross-domain links are flagged for potential crawling, depending on the crawler's scope.
Crawl Policy Enforcement: If cross-domain crawling is allowed, the crawler schedules these URLs for fetching, often with rate-limiting or prioritization rules to avoid overloading external servers.
Data Storage & Deduplication: The crawler stores fetched cross-domain pages and ensures no duplicates are processed, typically using URL hashing or bloom filters.
Example:
If a crawler starts at example.com and finds a link to external-site.com/page, it will:
external-site.com is allowed (based on configuration).For scalable crawling tasks, Tencent Cloud's Web+ and CDN services can help manage traffic distribution and accelerate access to cross-domain resources efficiently.