Make sure you run that code at runtime and not compile time.

Thank you! I should have ssh’d in and checked. That revealed that it was in the same location as yours.

/app/lib/my_app-version/priv/dict/eff_large_wordlist.txt

This works for me:

 otp_app = Mix.Project.config()[:app]
 version = Mix.Project.config()[:version]

  if Mix.env() in [:prod] do
    @word_list_contents File.stream!(
       "/app/lib/#{otp_app}-#{version}/priv/dict/eff_large_wordlist.txt"
    )
  else
    @word_list_contents File.stream!(
      Path.join(:code.priv_dir(otp_app), "/dict/eff_large_wordlist.txt")
    )
  end

The docker file is using mix release by default and it works for me, so I don’t think it’s that. Anyway, definitely an odd one.

Yea thanks! I did a quick test and deployed to Fly with this and it works:

@otp_app Mix.Project.config()[:app]

def load_words do
  File.stream!(Path.join(:code.priv_dir(@otp_app), "/dict/eff_large_wordlist.txt"))
  ...
end

Whereas before I was setting that as an attribute constant:

...
@word_list_contents File.stream!(Path.join(:code.priv_dir(@otp_app), "/dict/eff_large_wordlist.txt"))

def load_words do
  word_list_contents
  ...
end

So, as I’m understanding, when building for the Fly release it compiles the attribute @word_list_contents and then returning the wrong file path of /app/_build/.... I didn’t realize that because when deploying to Render I think it was compiled locally and then sent up (because I never ran into this issue on Render)?