Purge never finishes

Hello @David Littlewood,

Thanks for reaching out to Microsoft Q&A.

I see you're having some trouble with the cache purge not completing on Azure Front Door. This can be frustrating! Here are a few things to consider that might help you resolve the issue:

1. Purging Process: Typically, purging cached content can take up to 10 minutes to propagate across all Azure Front Door POP locations. If it takes longer than that, it's worth checking the caching settings.
2. Check Caching Status: Ensure that caching is enabled on your endpoint. You can check this in the Azure portal under the Optimizations pane.
3. Cache Purge Call Limits: Azure Front Door has a limit of 100 concurrent purge requests at any given time. If you've exceeded this limit, additional purge requests won't process until the number of concurrent requests goes down.
4. Caching Behavior: Verify that your request doesn’t include an Authorization header, as this may result in the response not being cached due to HTTP RFC compliance.
5. Asset Versioning: Consider versioning your assets with new URLs when updates are made. This ensures that users always get the latest version without relying on cache purges.
6. Request Headers: You may want to check the response headers, like x-cache, to gain insights into how the content is being served. If you see terms like MISS or PRIVATE_NOSTORE, it indicates issues with caching.

Reference documents:

Caching with Azure Front Door

Cache purging in Azure Front Door

Troubleshoot Azure Front Door Standard and Premium CDN Caching Issues

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