Add an example for leader election based multiple controller

examples/leader_example/lib/leader_example/application.ex

@@ -0,0 +1,20 @@
+defmodule LeaderExample.Application do
+  # See https://hexdocs.pm/elixir/Application.html
+  # for more information on OTP Applications
+  @moduledoc false
+
+  use Application
+
+  def start(_type, _args) do
+    # List all child processes to be supervised
+    children = [
+      # Starts a worker by calling: LeaderExample.Worker.start_link(arg)
+      # {LeaderExample.Worker, arg},
+    ]
+
+    # See https://hexdocs.pm/elixir/Supervisor.html
+    # for other strategies and supported options
+    opts = [strategy: :one_for_one, name: LeaderExample.Supervisor]
+    Supervisor.start_link(children, opts)
+  end
+end

examples/leader_example/lib/leader_example/leader.ex

@@ -0,0 +1,77 @@
+defmodule LeaderExample.Leader do
+  use Tres.Controller
+
+  @behaviour :locks_leader
+
+  require Logger
+
+  def start_link(datapath_id, args) do
+    :locks_leader.start_link(__MODULE__, [datapath_id, args], [])
+  end
+
+  def init([{datapath_id, _aux_id}, _args]) do
+    :ok = Logger.debug("Switch Ready: datapath_id: #{inspect(datapath_id)}")
+    :ok = role_request(datapath_id, role: :slave, generation_id: 0)
+    {:ok, %{am_leader: false, gen_id: 0, datapath_id: datapath_id}}
+  end
+
+  def elected(state, _info, _cand) do
+    :ok = Logger.info("Elected: #{inspect(Node.self)} for #{state.datapath_id} gen_id: #{state.gen_id}")
+    :ok = role_request(state.datapath_id, role: :master, generation_id: state.gen_id)
+    {:ok, {:elected, {Node.self(), state.gen_id + 1}}, %{state|am_leader: true}}
+  end
+
+  def surrendered(%{am_leader: true} = state, {:elected, {_node, next_gen_id}}, _info) do
+    :ok = Logger.info("network split possible detected")
+    :ok = role_request(state.datapath_id, role: :slave, generation_id: state.gen_id)
+    {:ok, %{state|am_leader: false, gen_id: next_gen_id}}
+  end
+
+  def surrendered(state, {:elected, {node, next_gen_id}}, _info) do
+    :ok = Logger.info("Surrendered: elected node is #{node} for #{state.datapath_id}")
+    :ok = role_request(state.datapath_id, role: :slave, generation_id: state.gen_id)
+    {:ok, %{state|am_leader: false, gen_id: next_gen_id}}
+  end
+
+  def handle_DOWN(_pid, state, _info) do
+    :ok = Logger.warn("DOWN detected")
+    {:ok, state}
+  end
+
+  def handle_leader_call(msg, from, state, _info) do
+    :ok = Logger.info("leader call with: #{inspect(msg)} from: #{inspect(from)} on #{Node.self()}")
+    {:reply, :ok, state}
+  end
+
+  def handle_leader_cast(_msg, state, _info) do
+    {:ok, state}
+  end
+
+  def from_leader(_from_leader, state, _info) do
+    {:ok, state}
+  end
+
+  def handle_call(_msg, _from, state, _info) do
+    {:reply, :ok, state}
+  end
+
+  def handle_cast(_msg, state, _info) do
+    {:noreply, state}
+  end
+
+  def handle_info(%Role.Reply{datapath_id: dpid} = role, %{datapath_id: dpid} = state, _info) do
+    :ok = Logger.info("#{Node.self()} is on #{role.role} for #{dpid}")
+    {:noreply, state}
+  end
+  def handle_info(_msg, state, _info) do
+    {:noreply, state}
+  end
+
+  def code_change(_from_vsn, state, _info, _extra) do
+    {:ok, state}
+  end
+
+  def terminate(_reason, _state) do
+    :ok
+  end
+end