[#6] designing the plugin system

config/config.exs

@@ -1 +1,16 @@
 use Mix.Config
+
+
+# configuration for collectors. The format for each collector is {collector_process_id, module, [target_transfers], label, args}
+config :poa_agent, 
+       :collectors,
+       [
+         {:my_collector, POAAgent.Plugins.Collectors.MyCollector, [:my_transfer], :my_metrics, [host: "localhost", port: 1234]}
+       ]
+
+# configuration for transfers. The format for each collector is {collector_process_id, module, args}
+config :poa_agent, 
+       :transfers,
+       [
+         {:my_transfer, POAAgent.Plugins.Transfers.MyTransfer, [ws_key: "mykey", other_stuff: "hello"]}
+       ]

lib/poa_agent.ex

@@ -1,9 +0,0 @@
-defmodule POAAgent do
-  @moduledoc """
-  Documentation for PoaAgent.
-  """
-
-  def hello do
-    :world
-  end
-end

lib/poa_agent/application.ex

@@ -0,0 +1,17 @@
+defmodule POAAgent.Application do
+  @moduledoc false
+
+  use Application
+
+  def start(_type, _args) do
+    import Supervisor.Spec
+
+    children = [
+      supervisor(POAAgent.Plugins.Transfers.Supervisor, []),
+      supervisor(POAAgent.Plugins.Collectors.Supervisor, [])
+    ]
+
+    opts = [strategy: :one_for_one, name: POAAgent.Supervisor]
+    Supervisor.start_link(children, opts)
+  end
+end

lib/poa_agent/plugins/collector.ex

@@ -0,0 +1,66 @@
+defmodule POAAgent.Plugins.Collector do
+
+  @callback init_collector(args :: term()) ::
+      {:ok, any()}
+
+  @callback collect(state :: any()) :: {:ok, data :: any(), state :: any()}
+
+  @callback terminate(reason, state :: term()) :: term()
+    when reason: :normal | :shutdown | {:shutdown, term()}
+
+  defmacro __using__(_opt) do
+    quote do
+      @behaviour POAAgent.Plugins.Collector
+
+      @doc false
+      def start_link(%{name: name} = state) do
+        GenServer.start_link(__MODULE__, state, name: name)
+      end
+
+      @doc false
+      def init(state) do
+        {:ok, internal_state} = init_collector(state[:args])
+        set_collector_timer()
+        {:ok, Map.put(state, :internal_state, internal_state)}
+      end
+
+      @doc false
+      def handle_call(_msg, _from, state) do
+        {:noreply, state}
+      end
+
+      @doc false
+      def handle_info(:collect, state) do
+        {:ok, data, internal_state} = collect(state.internal_state)
+        transfer(data, state.label, state.transfers)
+        set_collector_timer()
+        {:noreply, %{state | internal_state: internal_state}}
+      end
+      def handle_info(_msg, state) do
+        {:noreply, state}
+      end
+
+      @doc false
+      def handle_cast(msg, state) do
+        {:noreply, state}
+      end
+
+      @doc false
+      def code_change(_old, state, _extra) do
+        {:ok, state}
+      end
+
+      @doc false
+      def transfer(data, label, transfers) do
+        Enum.each(transfers, &GenServer.cast(&1, %{label: label, data: data}))
+        :ok
+      end
+
+      defp set_collector_timer() do
+        Process.send_after(self(), :collect, 5000) # TODO timeout must be configurable
+      end
+
+    end
+  end
+
+end

lib/poa_agent/plugins/collectors/my_collector.ex

@@ -0,0 +1,18 @@
+defmodule POAAgent.Plugins.Collectors.MyCollector do
+  use POAAgent.Plugins.Collector
+
+  def init_collector(args) do
+    IO.puts "init_collector args = #{inspect args}"
+    {:ok, :no_state}
+  end
+
+  def collect(:no_state) do
+    IO.puts "I am collecting data!"
+    {:ok, "data retrieved", :no_state}
+  end
+
+  def terminate(_reason, _state) do
+    :ok
+  end
+
+end

lib/poa_agent/plugins/collectors/supervisor.ex

@@ -0,0 +1,22 @@
+defmodule POAAgent.Plugins.Collectors.Supervisor do
+  @moduledoc false
+
+  def start_link do
+    Supervisor.start_link(__MODULE__, :ok, name: __MODULE__)
+  end
+
+  def init(:ok) do
+    import Supervisor.Spec
+
+    # create the children from the config file
+    collectors = Application.get_env(:poa_agent, :collectors)
+
+    children = for {name, module, transfers, label, args} <- collectors do
+      worker(module, [%{name: name, transfers: transfers, label: label, args: args}])
+    end
+
+    opts = [strategy: :one_for_one]
+    supervise(children, opts)
+  end
+
+end

lib/poa_agent/plugins/transfer.ex

@@ -0,0 +1,53 @@
+defmodule POAAgent.Plugins.Transfer do
+
+  @callback init_transfer(args :: term()) ::
+      {:ok, any()}
+
+  @callback data_received(label :: atom(), data :: any(), state :: any()) :: {:ok, any()}
+
+  @callback terminate(reason, state :: term()) :: term()
+    when reason: :normal | :shutdown | {:shutdown, term()}
+
+  defmacro __using__(_opt) do
+    quote do
+      @behaviour POAAgent.Plugins.Transfer
+
+      @doc false
+      def start_link(%{name: name} = state) do
+        GenServer.start_link(__MODULE__, state, name: name)
+      end
+
+      @doc false
+      def init(state) do
+        {:ok, internal_state} = init_transfer(state[:args])
+        {:ok, Map.put(state, :internal_state, internal_state)}
+      end
+
+      @doc false
+      def handle_call(_msg, _from, state) do
+        {:noreply, state}
+      end
+
+      @doc false
+      def handle_info(_msg, state) do
+        {:noreply, state}
+      end
+
+      @doc false
+      def handle_cast(%{label: label, data: data}, state) do
+        {:ok, internal_state} = data_received(label, data, state.internal_state)
+        {:noreply, %{state | internal_state: internal_state}}
+      end
+      def handle_cast(msg, state) do
+        {:noreply, state}
+      end
+
+      @doc false
+      def code_change(_old, state, _extra) do
+        {:ok, state}
+      end
+
+    end
+  end
+
+end

lib/poa_agent/plugins/transfers/my_transfer.ex

@@ -0,0 +1,18 @@
+defmodule POAAgent.Plugins.Transfers.MyTransfer do
+  use POAAgent.Plugins.Transfer
+
+  def init_transfer(args) do
+    IO.puts "init_transfer args = #{inspect args}"
+    {:ok, :no_state}
+  end
+
+  def data_received(label, data, state) do
+    IO.puts "Received data with label #{inspect label}, data #{inspect data} and internal_state #{inspect state}"
+    {:ok, :no_state}
+  end
+
+  def terminate(_reason, _state) do
+    :ok
+  end
+
+end

lib/poa_agent/plugins/transfers/supervisor.ex

@@ -0,0 +1,22 @@
+defmodule POAAgent.Plugins.Transfers.Supervisor do
+  @moduledoc false
+
+  def start_link do
+    Supervisor.start_link(__MODULE__, :ok, name: __MODULE__)
+  end
+
+  def init(:ok) do
+    import Supervisor.Spec
+
+    # create the children from the config file
+    transfers = Application.get_env(:poa_agent, :transfers)
+
+    children = for {name, module, args} <- transfers do
+      worker(module, [%{name: name, args: args}])
+    end
+
+    opts = [strategy: :one_for_one]
+    supervise(children, opts)
+  end
+
+end

mix.exs

@@ -13,7 +13,8 @@ defmodule POAAgent.MixProject do
 
   def application do
     [
-      extra_applications: [:logger]
+      extra_applications: [:logger],
+      mod: {POAAgent.Application, []}
     ]
   end
 

test/poa_agent_test.exs

@@ -3,6 +3,6 @@ defmodule POAAgentTest do
   doctest POAAgent
 
   test "greets the world" do
-    assert POAAgent.hello() == :world
+    # assert POAAgent.hello() == :world
   end
 end