Memory leak in rails app..creating log file

We've been dealing with a memory leak issue with our Rails app. We're using Ruby 2.5 and We're suspecting that it has to do with symbols not being garbage collectible. I'd like to implement a file where I log the symbols size (Symbol.all_symbols.size) during the life of the application. It should be updated after every request (after_action inside ApplicationController). I'm not sure how to implement this and what the file should look like. I could use some help.