CDN (Content Delivery Network) cache refresh is the process of updating or invalidating cached content on CDN edge servers to ensure users receive the latest version of a file or webpage. This is crucial when content changes frequently, such as with dynamic websites, news updates, or software downloads.
Mechanism of CDN Cache Refresh
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Cache Invalidation
- When a file is updated on the origin server, the CDN must remove the outdated cached copy.
- This can be triggered manually (via API or console) or automatically (via rules or time-based expiration).
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Time-to-Live (TTL) Expiration
- Each cached file has a predefined TTL (e.g., 1 hour, 1 day). Once expired, the CDN fetches the fresh version from the origin server.
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Manual Purge
- Users can manually purge specific files or entire directories from the CDN cache, forcing the CDN to fetch new content from the origin.
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Versioning (File Naming)
- Changing the file name (e.g.,
script_v2.js instead of script.js) ensures the CDN treats it as a new file, bypassing the old cached version.
Example
A news website updates an article titled breaking-news.html. To ensure users see the latest version:
- The website admin manually purges
breaking-news.html from the CDN cache.
- Alternatively, the CDN is configured to check the origin server every 5 minutes (short TTL) for updates.
Tencent Cloud CDN Cache Refresh
Tencent Cloud CDN provides efficient cache refresh mechanisms:
- URL Purge: Manually invalidate specific URLs or directories.
- Directory Purge: Refresh entire folders at once.
- Preloading: Pre-cache content before it’s requested to reduce latency.
- TTL Settings: Customize cache expiration for different file types.
Tencent Cloud CDN ensures fast and reliable content delivery with flexible cache management options.