Kungfuig        

Intro

Live config supporting many different backends.

Kungfuig (pronounced: [ˌkʌŋˈfig]) provides an easy way to plug live configuration into everything.

It provides backends for env and system and supports custom backends.

Installation

def deps do
  [
    {:kungfuig, "~> 0.1"}
  ]
end

Using

Kungfuig is the easy way to read the external configuration from sources that are not controlled by the application using it, such as Redis, or Database.

Here is the example of backend implementation for the config read from external MySQL.

defmodule MyApp.Kungfuig.MySQL do
  @moduledoc false

  use Kungfuig.Backend

  @impl Kungfuig.Backend
  def get(_meta) do
    with {:ok, host} <- System.fetch_env("MYSQL_HOST"),
         {:ok, db} <- System.fetch_env("MYSQL_DB"),
         {:ok, user} <- System.fetch_env("MYSQL_USER"),
         {:ok, pass} <- System.fetch_env("MYSQL_PASS"),
         {:ok, pid} when is_pid(pid) <-
           MyXQL.start_link(hostname: host, database: db, username: user, password: pass),
         result <- MyXQL.query!(pid, "SELECT * FROM some_table") do
      GenServer.stop(pid)

      result =
        result.rows
        |> Flow.from_enumerable()
        |> Flow.map(fn [_, field1, field2, _, _] -> {field1, field2} end)
        |> Flow.partition(key: &elem(&1, 0))
        |> Flow.reduce(fn -> %{} end, fn {field1, field2}, acc ->
          Map.update(
            acc,
            String.to_existing_atom(field1),
            [field2],
            &[field2 | &1]
          )
        end)

      Logger.info("Loaded #{Enum.count(result)} values from " <> host)

      {:ok, result}
    else
      :error ->
        Logger.warn("Skipped reconfig, one of MYSQL_{HOST,DB,USER,PASS} is missing")
        :ok

      error ->
        Logger.error("Reconfiguring failed. Error: " <> inspect(error))
        {:error, error}
    end
  end
end

Testing

Simply implement a stub returning an expected config and you are all set.

defmodule MyApp.Kungfuig.Stub do
  @moduledoc false

  use Kungfuig.Backend

  @impl Kungfuig.Backend
  def get(_meta), do: %{foo: :bar, baz: [42]}
end

Changelog

• 1.0.0 — modern Elixir v1.16
• 0.4.4 — fix a bug with hardcoded names (Supervisor and Blender)
• 0.4.2 — allow imminent: true option to Kungfuig.Backend
• 0.4.0 — allow named Kungfuig.Supervisor (thanks @vbroskas)
• 0.3.0 — allow validation through NimbleOptions (per backend and global)
• 0.2.0 — scaffold for backends + several callbacks (and the automatic one for Blender)

Documentation