Getting started

Aker holds no key of its own. Your app passes its product name, its version and the root public keys it trusts, and decides itself what a lock blocks.

1. Keep the licence somewhere

The gate reads and writes the licence through a module that implements Aker.Store. A record is any map or struct with :envelope, :licence_id, :serial, :term_end and :last_seen_at.

defmodule MyApp.LicenceStore do
  @behaviour Aker.Store

  @impl true
  def current(_opts), do: {:ok, MyApp.Repo.one(MyApp.Licence.newest())}

  @impl true
  def store(attrs, actor, _opts) do
    if actor == :system or MyApp.Accounts.admin?(actor),
      do: MyApp.Licence.insert(attrs),
      else: {:error, :forbidden}
  end

  @impl true
  def touch(record, last_seen_at, _opts), do: MyApp.Licence.touch(record, last_seen_at)
end

The gate passes the actor from your call to store/3 untouched, and a renewal stores as :system. Your store decides who may write.

2. Start the gate

def gate_options do
  {:ok, root_keys} = Aker.PublicKeys.decode(Application.fetch_env!(:my_app, :root_keys))

  [
    name: MyApp.Licence,
    product: "my_app",
    product_version: to_string(Application.spec(:my_app, :vsn)),
    root_keys: root_keys,
    licence_dir: System.get_env("MY_APP_LICENCE_DIR"),
    machine_id_path: System.get_env("MY_APP_MACHINE_ID_PATH"),
    store: {MyApp.LicenceStore, []},
    server: [base_url: "https://licensing.example.com"],
    on_lock: &MyApp.Workers.stop_all/0,
    on_unlock: &MyApp.Workers.start_all/0,
    settings: [licence_dir: "MY_APP_LICENCE_DIR", machine_id_path: "MY_APP_MACHINE_ID_PATH"]
  ]
end

# In your application's children:
{Aker.Gate, MyApp.gate_options()}

The gate checks the licence at boot, then every hour. In the term's last week each hourly tick asks the server for the next term's licence.

3. Read the lock

Aker.Gate.locked?(MyApp.Licence)
# => true until a licence passes

A gate name no check has run under reads {:locked, :not_checked}, so an app that never starts the gate runs locked. Read the status on each page or job that the licence guards.

4. Activate, load and refresh

Aker.Gate.activate(MyApp.gate_options(), "ABCD-EFGH-2345", current_user)
Aker.Gate.load(MyApp.gate_options(), File.read!("licence.json"), current_user)
Aker.Gate.refresh(MyApp.gate_options(), current_user)

These trust your app to have checked who may call them. Check the caller before you call.