I know this question has been asked many times and it's also covered in official memcached FAQ. But my case is - I want to use it just for admin panel purposes. I want to see keys with values in my admin page so it doesn't matter if it's slow and against the best practices. Please advise, if it's possible.
There's no way to do it that's guaranteed to work. The only way I found is the way you'll find on google, but there's a restriction: Only 1 MB will be returned - it may not be all keys. And it will probably be quite slow..
If you really, really has to have all those keys you'd probably have to hack the source code.
I would say: no, you can't.
Why do you need all those key? I would consider redesigning your application to not make your admin panel dependent of the internals of a caching server
List all memcached keys/values