Background

Hello all, I have a machine in production running an elixir application (no access to iex, only to erl) and I am tasked with running an analysis on why we are consuming so much CPU. The idea here would be to launch observer, check the processes tab and see the processes with the most reductions.

How am I connecting?

To connect I am following a tutorial from a blog:

• Elixir/Erlang, Running OTP Observer Remotely

Their instructions are as follows:

1. launch the app in the production machine with a cookie and a name
2. from local run: ssh user@public_ip "epmd -names" to get the name of the app and the port used
3. create a ssh tunel to the remote machine: ssh -L 4369:user@public_ip:4369 -L 42877:user@public_ip:42877 user@public_ip (4369 is the epmd port by default, 42877 is the port of the app)
4. connect to the remote machine via public ip: erl -name "user@public_ip" -setcookie "mah_cookie" -hidden -run observer

Problem

And now in theory I should be able to use observer on the machine. Instead however I am greeted with the following error:

Protocol ‘inet_tcp’: register/listen error: epmd_close

Questions

1. What am I doing wrong?
   I read that in older version of erlang I can’t monitor a machine with observer if they are in different networks (which is the case, because I want to monitor this machine from my localhost) but I didn’t find any information regarding modern days.
2. If this is in fact impossible, what alternatives do I have?