Example usage of Surrogate Keys with custom values

[mac-chaffee]

Hello! I'm trying to understand how to use surrogate keys and can't seem to get it to work by merely following the spec.

My use-case is that I need to associate a group of cached files with a "project ID" so I can purge all files for the project when it is modified. I'm using Caddy and Otter.

Here's my Caddy config (using github.com/darkweak/souin/plugins/[email protected])

{
	cache {
		ttl 300s
		max_cacheable_body_bytes 1000000
		otter
		api {
			souin
		}
		# This may be required to enable surrogate-keys? https://github.com/darkweak/souin/issues/306#issuecomment-1429744951
		cdn {
			dynamic
			provider souin
		}
		default_cache_control public
	}
}

localhost {
	route {
		cache
		reverse_proxy web:3000
	}
}

When I want to set a surrogate-key, I include the header in the response in my application code (web:3000):

$ curl -ik -H "Host: picouser-www.localhost" https://localhost                        
HTTP/2 200 
alt-svc: h3=":443"; ma=2592000
cache-control: public
cache-status: Souin; fwd=uri-miss; stored; key=GET-https-picouser-www.localhost-/
content-security-policy: script-src 'self'
content-type: text/html
date: Tue, 22 Oct 2024 02:16:29 GMT
etag: 5fddc78468241bf0dc7e721867874288
last-modified: Mon, 21 Oct 2024 20:21:37 GMT
server: Caddy
strict-transport-security: max-age=31536000; preload
surrogate-key: picouser-www                                <------ Project ID surrogate key is set here
x-frame-options: DENY
content-length: 2051

But the surrogate key is never saved:

$ curl 'https://localhost/souin-api/souin/surrogate_keys' | jq
{
  "GET-https-picouser-www.localhost-/": "<omitted>",
  "IDX_GET-https-picouser-www.localhost-/": "\n�\u0001\n\"GET-https-picouser-www.localhost-/\u0012k\n\u000b\b��ܸ\u0006\u0010���Y\u0012\n\b��ܸ\u0006\u0010��\u0004\u001a\n\b��ܸ\u0006\u0010��\u0004* 5fddc78468241bf0dc7e7218678742882\"GET-https-picouser-www.localhost-/"
}

Likewise, purging via the surrogate key I set also does not clear this cache entry.

I searched through the code and is seems like what I'm doing should work, but I may be missing a config value or something:

souin/pkg/surrogate/providers/common.go

Line 238 in 2968d51

s.storeTag(key, cacheKey, urlRegexp)

Am I using the feature incorrectly? Or could there be a bug? Happy to provide further info!