You’d choose a config provider, copy it into the release, and that’s it, I think.
Somewhere in rel/config.exs
environment :prod do
set config_providers: [
{Mix.Releases.Config.Providers.Elixir, ["${RELEASE_ROOT_DIR}/etc/config.exs"]}
]
set overlays: [
{:copy, "rel/config/config.exs", "etc/config.exs"}
]
end
In rel/config/config.exs
use Mix.Config
config :app, db_path: System.get_env("DB_PATH")
You don’t need to set it yourself.
I’m not sure if distillery scripts use it for replacing ${RELEASE_ROOT_DIR} in its config.
The only use-case that I have for REPLACE_OS_VARS is setting the node name of the app to the ip address of the machine which is read at startup.
In rel/config.exs
environment :prod do
# ...
set(vm_args: "rel/vm.args")
set(pre_configure_hooks: "rel/hooks/pre_configure")
# ...
end
in rel/hooks/pre_configure/export_host_ipv4
#!/usr/bin/env bash
export HOST_IPV4
export REPLACE_OS_VARS=true
HOST_IPV4=$(
# just as an example, might not work actually
ifconfig \
| sed -En 's/127.0.0.1//;s/.*inet (addr:)?(([0-9]*\.){3}[0-9]*).*/\2/p' \
| grep '^10\.' # only interested in private network
)
and in rel/vm.args
-name app@${HOST_IPV4}
% ... etc
Ok so this is a dumb question, but with config providers where do I actually provide the variables now? Like where and how do I ‘pass them in’?
Depends on the tools that you use. In kubernetes, I think env vars are set via yaml configs, in docker, ENV is used. In systemd Environment=, etc …
For anyone else here i found this good article Elixir: Runtime vs. compile time configuration | AmberBit Sp. z o. o.
I would personally recommend going with Docker for deployments on VPS systems. This helps you not becoming dependent on an individual provider and makes it easier to create repeatable deployments.
Check out this guide on Getting Started with Elixir and Docker I’ve created and let me know if you find it helpful!
