Does nginx plus/oss hold the unhashed cache key or uri metadata in memory?

"How Do I...?"
1

What I’m trying to do:

I am trying to create a module that shows the original urls of the cached content in nginx.

An example would be /media/image.jpg is requested repeatedly and cached by nginx proxy. And lets say we have an endpoint that when requested dumps all the uri metadata of the active cache like.

{md5: SG...A32, uri: "/media/image.jpg"}
{md5: DF...AB4, uri: "/media/image2.jpg"}

For my purposes the original unhashed cache key would also work which has the default definition of

proxy_cache_key $scheme$proxy_host$request_uri;

Now I have done a preliminary exploration of the nginx source code and suspect this is not held in memory at all in nginx oss. However, as the nginx plus does support wildcard purgers, I figure it must hold this information in memory somewhere to do a regex search for a wildcard purge.

Where I’m stuck:

I can not find any documentation for if nginx plus (given up on oss for now I think) holds that information in memory and how could one reach it inside a dynamically loaded module.

What I’ve already tried:

I have created a module that dumps the cache shared memory with these fields


{"zone":"mycache","md5":"c510b260709c96464511de161764e0aa","mem":84,"disk":342992,"uses":5,"expire":1745848168}

Note: disk size is also not held and I do a stat call from the module to the file.

I am aware this information is held on disk but it is too costly for my circumstance do read that much seperate files from the disk on production.

I also did gcore dump the nginx processes and tried to find the string I am looking for in memory for which I succeeded. However I believe (or at least could not figure out a way to prove otherwise) it is just stale non-yet-zeroed memory from the actual request proccesing.

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