docuconf for Elixir

mix deps.get

# Until the first release, from the main branch:
{:docuconf, github: "Docuconf/docuconf-elixir", branch: "main"}

defmodule Orders.Env do
  @moduledoc "Every environment variable the orders service reads."
  use Docuconf, name: "orders"

  env :port, :integer, description: "HTTP listen port", default: 8080, min: 1, max: 65535

  # Atom values come back as atoms, ready for Logger.
  env :log_level, {:in, [:debug, :info, :warning, :error]},
    description: "Minimum log level",
    default: :info

  # A secret: docuconf never prints its value (not in errors, and not when
  # Orders.Env is inspected or logged), and the contract tells the platform
  # to supply it from a Kubernetes Secret.
  secret :database_url, :url,
    description: "Postgres connection string",
    required: true,
    schemes: ["postgres"],
    max_length: 2048

  env :allowed_origins, {:list, :string},
    description: "Origins allowed to call the API (CORS)",
    min_items: 1,
    default: ["http://localhost:3000"]

  @doc """
  Time limit for one request.

  Raise it when clients upload large order batches. Keep it below the load
  balancer's idle timeout, or the client sees a reset rather than a `504`.
  """
  env :request_timeout, :duration,
    min: "1s",
    max: "5m",
    default: "30s"

  env :worker_count, :integer,
    description: "Order processing workers",
    min: 1,
    max: 64,
    default: 4
end

import Config

# Every variable is validated here, at boot. All problems are reported
# together, the process exits with status 1, and the report is written to
# /dev/termination-log in Kubernetes.
env = Orders.Env.load!()

config :orders, env: env
config :logger, level: env.log_level

DATABASE_URL=postgres://orders:pw@localhost:5432/orders mix run --no-halt

$ PORT=0 mix run --no-halt
...
docuconf: 2 configuration problems:
  - DATABASE_URL [missing_required]: required, but not set
  - PORT [out_of_range]: "0" is below min 1

defmodule Orders.EnvTest do
  use ExUnit.Case, async: true

  # load/1 with an explicit env: map never reads or changes the process environment.
  test "defaults" do
    {:ok, env} = Orders.Env.load(env: %{"DATABASE_URL" => "postgres://orders@db/orders"})
    assert env.port == 8080
    assert env.worker_count == 4
  end

  test "rejects bad values" do
    {:error, error} = Orders.Env.load(env: %{"PORT" => "70000"})
    found = Enum.map(error.violations, &{&1.input, &1.code})
    assert {"PORT", :out_of_range} in found
    assert {"DATABASE_URL", :missing_required} in found
  end
end

mix test --no-start

mix docuconf.export

// Code generated by docuconf. DO NOT EDIT.
package orders

import "docuconf.dev/contract"

contract.#Contract & {
	apiVersion: "docuconf.dev/v1alpha1"
	kind: "ConfigContract"
	metadata: {
		name: "orders"
		appVersion: "1.0.0"
		generator: {
			language: "elixir"
			sdk: "docuconf"
			version: "0.1.0"
		}
	}
	vars: {
		ALLOWED_ORIGINS: {
			type: "list"
			description: "Origins allowed to call the API (CORS)"
			items: "string"
			encoding: "csv"
			separator: ","
			minItems: 1
			default: ["http://localhost:3000"]
		}
		DATABASE_URL: {
			type: "url"
			description: "Postgres connection string"
			required: true
			secret: true
			schemes: ["postgres"]
			maxLength: 2048
		}
		LOG_LEVEL: {
			type: "enum"
			description: "Minimum log level"
			values: ["debug", "info", "warning", "error"]
			default: "info"
		}
		PORT: {
			type: "int"
			description: "HTTP listen port"
			min: 1
			max: 65535
			default: 8080
		}
		REQUEST_TIMEOUT: {
			type: "duration"
			description: "Time limit for one request"
			details: "Raise it when clients upload large order batches. Keep it below the load\nbalancer's idle timeout, or the client sees a reset rather than a `504`."
			encoding: "go"
			min: "1s"
			max: "5m"
			default: "30s"
		}
		WORKER_COUNT: {
			type: "int"
			description: "Order processing workers"
			min: 1
			max: 64
			default: 4
		}
	}
}