Unable to purge root path ("/") cache entry without clearing entire cache

[antoniy-mihaylov]

We are unable to purge the cache entry for the root path ("/") without clearing the entire cache using a wildcard.

Environment:

• nginx version: 1.27.4
• ngx_cache_purge version: 2.5.4

Setup:

• nginx with ngx_cache_purge module
• Cache key format: $scheme$host$request_uri
• Purge endpoint: location ~ ^/ops/purge(/.*)$ { proxy_cache_purge cache_zone $scheme$host$1; }
• Actual cache key for root: httpmyapp.example.com/ (scheme + host + /)

Problem:

When attempting to purge the root path cache entry:

1. Exact match purge (/ops/purge/) → Returns HTTP 412

   • Expected cache key: httpmyapp.example.com/
   • Result: Not purged (HTTP 412 - NGX_DECLINED)

2. Wildcard purge (/ops/purge/*) → Returns HTTP 200

   • Problem: Purges ALL cache entries, not just the root path
   • This is unacceptable as it clears the entire cache

Questions:

• Does exact key purging work for root path entries?
• Is there something special about purging cache keys that end with just "/" (the root path)?
• Should the cache key httpmyapp.example.com/ be purgeable via exact match?

We would appreciate any guidance on whether this is expected behavior or if there is a configuration/approach we are missing to purge the root path cache entry specifically.