backend: live connection status!

backend/lib/prymn/agents/connection.ex

@@ -1,6 +1,9 @@
 defmodule Prymn.Agents.Connection do
   @moduledoc false
 
+  # TODO: Disconnect after a while of idling. Disconnect when the healthcheck
+  #       fails too many times.
+
   defstruct [:channel, up?: false]
 
   @ping_interval 20000
@@ -46,15 +49,27 @@ defmodule Prymn.Agents.Connection do
   end
 
   @impl true
-  def handle_info({:gun_up, _pid, _protocol}, state) do
-    Logger.info("regained connection (#{inspect(state.channel)})")
+  def handle_info({:gun_up, _pid, _protocol}, %{channel: channel} = state) do
+    Logger.info("[Agent] #{state.channel.host} regained connection")
+
+    Phoenix.PubSub.broadcast!(
+      Prymn.PubSub,
+      "agent:#{channel.host}",
+      {:healthcheck, :up, channel.host}
+    )
 
     {:noreply, %{state | up?: true}}
   end
 
   @impl true
-  def handle_info({:gun_down, _pid, _protocol, reason, _killed_streams}, state) do
-    Logger.info("lost connection (reason: #{inspect(reason)}, #{inspect(state.channel)})")
+  def handle_info({:gun_down, _pid, _proto, reason, _}, %{channel: channel} = state) do
+    Logger.info("[Agent] #{channel.host} lost connection, reason: #{reason}")
+
+    Phoenix.PubSub.broadcast!(
+      Prymn.PubSub,
+      "agent:#{channel.host}",
+      {:healthcheck, :down, channel.host}
+    )
 
     {:noreply, %{state | up?: false}}
   end
@@ -67,8 +82,6 @@ defmodule Prymn.Agents.Connection do
       {:ok, _reply} ->
         :noop
 
-      # IO.inspect(reply)
-
       {:error, error} ->
         Logger.warning("healthcheck error for server #{channel.host}, reason: #{inspect(error)}")
     end

backend/lib/prymn/servers.ex

@@ -37,6 +37,12 @@ defmodule Prymn.Servers do
   """
   def get_server!(id), do: Repo.get!(Server, id)
 
+  @doc """
+  Get a single server by its IP.
+  """
+  @spec get_server_by_ip!(String.t()) :: %Server{}
+  def get_server_by_ip!(ip), do: Repo.get_by!(Server, public_ip: ip)
+
   @doc """
 
   Start a new server connection with the app.
@@ -52,16 +58,19 @@ defmodule Prymn.Servers do
   Registers a server using a registration token.
   """
   def register_server(token, public_ip) do
-    # TODO: Validate public ip
+    with true <- :inet.is_ip_address(public_ip),
+         {:ok, token} <- Base.decode64(token) do
+      public_ip_string =
+        public_ip
+        |> :inet.ntoa()
+        |> to_string()
 
-    case Base.decode64(token) do
-      {:ok, token} ->
-        from(s in Server, where: s.registration_token == ^token, select: s)
-        |> Repo.one()
-        |> update_server(%{public_ip: public_ip})
-
-      :error ->
-        {:error, "token is not a valid base64 encoded string"}
+      from(s in Server, where: s.registration_token == ^token, select: s)
+      |> Repo.one!()
+      |> update_server(%{public_ip: public_ip_string, status: :registered})
+    else
+      false -> {:error, :invalid_ip}
+      :error -> {:error, :bad_token}
     end
   end
 
@@ -111,4 +120,26 @@ defmodule Prymn.Servers do
   def change_server(%Server{} = server, attrs \\ %{}) do
     Server.changeset(server, attrs)
   end
+
+  @doc """
+  Returns a string containing the command that needs to be executed to the
+  remote server in order to register it to the backend.
+  """
+  @spec create_setup_command(%Server{}) :: String.t()
+  def create_setup_command(%Server{registration_token: token}) do
+    build_command = fn token ->
+      if Application.get_env(:prymn, :environment) == :prod do
+        "curl -sSf https://static.prymn.net/get_prymn.sh | sh -s " <> token
+      else
+        # On a dev environment we want to download the local version of the agent
+        agent_path = Path.expand("../agent/target/debug/prymn_agent")
+        get_prymn_path = Path.expand("../agent/get_prymn.sh")
+        "GET_PRYMN_ROOT=file://#{agent_path} #{get_prymn_path} #{token}"
+      end
+    end
+
+    token
+    |> Base.encode64()
+    |> then(build_command)
+  end
 end

backend/lib/prymn/servers/server.ex

@@ -8,9 +8,11 @@ defmodule Prymn.Servers.Server do
     field :provider, Ecto.Enum, values: [:Hetzner, :Custom]
     field :registration_token, :binary, redact: true
 
-    field :connection_status, Ecto.Enum,
-      values: [:awaiting, :connecting, :installing, :connected, :disconnected],
-      default: :awaiting
+    field :status, Ecto.Enum,
+      values: [:unregistered, :registered],
+      default: :unregistered
+
+    field :connection_status, :string, virtual: true
 
     timestamps()
   end
@@ -18,8 +20,9 @@ defmodule Prymn.Servers.Server do
   @doc false
   def changeset(server, attrs) do
     server
-    |> cast(attrs, [:name, :provider, :registration_token])
+    |> cast(attrs, [:name, :public_ip, :provider, :registration_token, :status])
     |> validate_required([:name, :provider])
     |> validate_inclusion(:provider, [:Custom], message: "Provider not available (yet)")
+    |> unique_constraint([:public_ip])
   end
 end

backend/lib/prymn_web/controllers/server_controller.ex

@@ -1,19 +1,36 @@
 defmodule PrymnWeb.ServerController do
-  use PrymnWeb, :controller
-
   alias Prymn.Servers
+  require Logger
+
+  use PrymnWeb, :controller
 
   @doc """
   Used by clients to request a new server connection to the prymn backend
   validating their registration token.
   """
-  def register(conn, %{"token" => token, "ip" => ip}) do
-    case Servers.register_server(token, ip) do
+  def register(conn, %{"token" => token}) do
+    case Servers.register_server(token, conn.remote_ip) do
       {:ok, _server} ->
         json(conn, %{"connected" => true})
 
+      {:error, :invalid_ip} ->
+        Logger.error("could not register a server because we received an invalid ip")
+
+        put_status(conn, 500)
+        |> json(%{"errors" => ["invalid ip received"]})
+
+      {:error, :bad_token} ->
+        put_status(conn, 400)
+        |> json(%{"errors" => %{"token" => "token is not valid"}})
+
+      {:error, %Ecto.Changeset{} = changeset} ->
+        errors = Ecto.Changeset.traverse_errors(changeset, fn {msg, _} -> msg end)
+
+        put_status(conn, 400)
+        |> json(%{"errors" => errors})
+
       {:error, error} ->
-        raise inspect(error)
+        raise "An unhandled error was received #{inspect(error)}"
     end
   end
 end

backend/lib/prymn_web/live/server_live/index.ex

@@ -1,15 +1,25 @@
 defmodule PrymnWeb.ServerLive.Index do
-  use PrymnWeb, :live_view
-
   alias Prymn.Servers
 
+  use PrymnWeb, :live_view
+
   @impl true
   def mount(_params, _session, socket) do
-    # Run this for every server:
-    #   make sure an agent connection is made (async "cheap" request)
-    #     then wait for events
-    #     pubsub will eventually send a connected or a disconnected (and anything else) event
-    {:ok, stream(socket, :servers, Servers.list_servers())}
+    servers = Servers.list_servers()
+    pid = self()
+
+    for %{public_ip: public_ip} <- servers, public_ip != nil do
+      :ok = Phoenix.PubSub.subscribe(Prymn.PubSub, "agent:#{public_ip}")
+
+      Task.start_link(fn ->
+        case Prymn.Agents.ensure_connection("#{public_ip}:50012") do
+          :ok -> Process.send(pid, {:healthcheck, :up, public_ip}, [])
+          {:error, _error} -> Process.send(pid, {:healthcheck, :down, public_ip}, [])
+        end
+      end)
+    end
+
+    {:ok, stream(socket, :servers, servers)}
   end
 
   @impl true
@@ -29,12 +39,22 @@ defmodule PrymnWeb.ServerLive.Index do
 
   @impl true
   def handle_info({:connect, %Servers.Server{} = server}, socket) do
-    socket =
-      if server.provider == :Custom,
-        do: push_navigate(socket, to: ~p"/servers/#{server}"),
-        else: stream_insert(socket, :servers, server)
+    {:noreply, stream_insert(socket, :servers, server)}
+  end
 
-    {:noreply, socket}
+  @impl true
+  def handle_info({:healthcheck, status, ip}, socket) do
+    server = Servers.get_server_by_ip!(ip)
+
+    status =
+      case status do
+        :up -> "Connected"
+        :down -> "Disconnected"
+      end
+
+    {:noreply,
+     socket
+     |> stream_insert(:servers, Map.put(server, :connection_status, status))}
   end
 
   @impl true

backend/lib/prymn_web/live/server_live/index.html.heex

@@ -13,19 +13,23 @@
   row_click={fn {_id, server} -> JS.navigate(~p"/servers/#{server}") end}
   row_indicator={
     fn
-      {_id, %Servers.Server{connection_status: :awaiting}} ->
-        ~H(<span class="text-grey-600">Awaiting connection</span>)
+      {_id, %Servers.Server{status: :unregistered}} ->
+        ~H(<span class="text-grey-600">Awaiting registration</span>)
 
-      {_id, %Servers.Server{connection_status: :connecting}} ->
-        ~H(<span class="text-purple-600">Connecting</span>)
+      {_id, %Servers.Server{connection_status: nil, status: :registered}} ->
+        ~H(<span class="text-yellow-600">Connecting...</span>)
 
-      {_id, %Servers.Server{connection_status: :connected}} ->
+      {_id, %Servers.Server{connection_status: "Connected"}} ->
         ~H(<span class="text-green-600">Connected</span>)
+
+      {_id, %Servers.Server{connection_status: "Disconnected"}} ->
+        ~H(<span class="text-red-600">Disconnected</span>)
     end
   }
   indicator_label="Status"
 >
   <:col :let={{_id, server}} label="Name"><%= server.name %></:col>
+  <:col :let={{_id, server}} label="IP"><%= server.public_ip || "N/A" %></:col>
   <:action :let={{id, server}}>
     <.link
       phx-click={JS.push("delete", value: %{id: server.id}) |> hide("##{id}")}

backend/lib/prymn_web/live/server_live/show.ex

@@ -15,6 +15,7 @@ defmodule PrymnWeb.ServerLive.Show do
     {:noreply,
      socket
      |> assign(:page_title, server.name)
-     |> assign(:server, server)}
+     |> assign(:server, server)
+     |> assign(:registration_command, Servers.create_setup_command(server))}
   end
 end

backend/lib/prymn_web/live/server_live/show.html.heex

@@ -2,7 +2,7 @@
   Server <%= @server.name %>
 </.header>
 
-<section :if={@server.connection_status == :awaiting} class="my-10">
+<section :if={@server.status == :unregistered} class="my-10">
   <p class="mb-9">
     Connect to your server using root credentials and execute the following command:
   </p>
@@ -10,7 +10,7 @@
     <code class="flex gap-4">
       <span class="select-none text-gray-500">#</span>
       <span class="flex-1">
-        your command here that contains token: <%= Base.encode64(@server.registration_token) %>
+        <%= @registration_command %>
       </span>
     </code>
     <button type="button" tabindex="-1">

backend/priv/repo/migrations/20230609164352_create_servers.exs

@@ -6,12 +6,13 @@ defmodule Prymn.Repo.Migrations.CreateServers do
       add :name, :string
       add :public_ip, :string
       add :provider, :string
-      add :connection_status, :string
+      add :status, :string
       add :registration_token, :binary
 
       timestamps()
     end
 
     create index("servers", [:registration_token], unique: true)
+    create index("servers", [:public_ip], unique: true)
   end
 end