Allow importing extra config (#3906)

* allow importing extra config

* changelog

* fix typo

* add test

CHANGELOG.md

@@ -31,6 +31,7 @@ All notable changes to this project will be documented in this file.
 - Add 'browser_versions.csv' to CSV export
 - Add `CLICKHOUSE_MAX_BUFFER_SIZE_BYTES` env var which defaults to `100000` (100KB)
 - Add alternative SMTP adapter plausible/analytics#3654
+- Add `EXTRA_CONFIG_PATH` env var to specify extra Elixir config plausible/analytics#3906
 
 ### Removed
 - Removed the nested custom event property breakdown UI when filtering by a goal in Goal Conversions

mix.exs

@@ -19,8 +19,10 @@ defmodule Plausible.MixProject do
       releases: [
         plausible: [
           include_executables_for: [:unix],
-          applications: [plausible: :permanent],
-          steps: [:assemble, :tar]
+          config_providers: [
+            {Config.Reader,
+             path: {:system, "RELEASE_ROOT", "/import_extra_config.exs"}, imports: []}
+          ]
         ]
       ],
       dialyzer: [

rel/overlays/import_extra_config.exs

@@ -0,0 +1,8 @@
+import Config
+import Plausible.ConfigHelpers
+
+config_dir = System.get_env("CONFIG_DIR", "/run/secrets")
+
+if extra_config_path = get_var_from_path_or_env(config_dir, "EXTRA_CONFIG_PATH") do
+  import_config extra_config_path
+end

test/plausible/config_test.exs

@@ -272,6 +272,44 @@ defmodule Plausible.ConfigTest do
     end
   end
 
+  describe "extra config" do
+    test "no-op when no extra path is set" do
+      put_system_env_undo({"EXTRA_CONFIG_PATH", nil})
+
+      assert Config.Reader.read!("rel/overlays/import_extra_config.exs") == []
+    end
+
+    test "raises if path is invalid" do
+      put_system_env_undo({"EXTRA_CONFIG_PATH", "no-such-file"})
+
+      assert_raise File.Error, ~r/could not read file/, fn ->
+        Config.Reader.read!("rel/overlays/import_extra_config.exs")
+      end
+    end
+
+    @tag :tmp_dir
+    test "reads extra config", %{tmp_dir: tmp_dir} do
+      extra_config_path = Path.join(tmp_dir, "config.exs")
+
+      File.write!(extra_config_path, """
+      import Config
+
+      config :plausible, Plausible.Repo,
+        after_connect: {Postgrex, :query!, ["SET search_path TO global_prefix", []]}
+      """)
+
+      put_system_env_undo({"EXTRA_CONFIG_PATH", extra_config_path})
+
+      assert Config.Reader.read!("rel/overlays/import_extra_config.exs") == [
+               {:plausible,
+                [
+                  {Plausible.Repo,
+                   [after_connect: {Postgrex, :query!, ["SET search_path TO global_prefix", []]}]}
+                ]}
+             ]
+    end
+  end
+
   defp runtime_config(env) do
     put_system_env_undo(env)
     Config.Reader.read!("config/runtime.exs", env: :prod)