Just to follow up: I did figure out how to lean heavily on FreeBSD’s rc system. The main thing is running the app under daemon(8) rather than using the elixir daemon. This produces a pid file, and so the service can use the built-in stop / restart / status behavior.

The following RC script is auto-generated by ExFreeBSD:

#!/bin/sh
#
# PROVIDE: release_test
# REQUIRE: DAEMON

. /etc/rc.subr

name=release_test
rcvar=${name}_enable
pidfile="/var/run/${name}.pid"
procname="/usr/local/libexec/release_test/erts-13.0.2/bin/beam.smp"

: ${release_test_env_file:=/usr/local/etc/release_test.env}

command="/usr/local/libexec/release_test/bin/release_test"
extra_commands="remote"
start_cmd="daemon -f -t $name -p $pidfile $command start"
remote_cmd=release_test_remote
#rpc_cmd=release_test_rpc

release_test_remote()
{
  export TERM=xterm
  $command remote
}

#release_test_rpc()
#{
#  $command rpc "$1"
#}

load_rc_config $name
run_rc_command "$@"

Okay. Do you have any suggestions on how to do a “real” restart, so I can reload the env vars?

I can run _build/dev/rel/release_test/bin/release_test stop but that can take a minute or two, and I’m not sure how to tell when it’s done in an automated way.

Typically daemons will write a pid file somewhere that you can use to reliably check the status. I don’t see anything like that.

I may be misunderstanding here - how do you do that? I can open up a new terminal tab, run the same second command, and get the same result. So, that’s not it.

Interesting… my takeaway from reading all this is that you should not configure Elixir apps using env vars, because once the erlang process is running, that’s it - there’s no way to get new env vars into it.

Instead, you use env vars to configure the erlang process. Then your application reads its own config from a file. Some of those tools you linked look like they’re intended to simulate env vars by reading the config from env-var-like files - but they’re not actually env vars.

I think for production releases, it’s probably important to cleanly separate these, and not load any app config from env vars since that only applies to app start. Vapor looks like it should do the trick there, but reading a config file should be simple enough. Thank you for the pointers!