Add scalable session thresholds

3 files changed, 58 insertions, 5 deletions

diff --git a/lib/chessh/schema/node.ex b/lib/chessh/schema/node.ex
index 867a6e2..8834aef 100644
--- a/lib/chessh/schema/node.ex
+++ b/lib/chessh/schema/node.ex
@@ -5,7 +5,7 @@ defmodule Chessh.Node do
 
   @primary_key {:id, :string, []}
   schema "nodes" do
-    field(:last_start, :utc_datetime)
+    field(:last_start, :utc_datetime_usec)
   end
 
   def changeset(node, attrs) do
@@ -18,7 +18,7 @@ defmodule Chessh.Node do
       nil -> %Chessh.Node{id: node_id}
       node -> node
     end
-    |> Chessh.Node.changeset(%{last_start: DateTime.utc_now()})
+    |> changeset(%{last_start: DateTime.utc_now()})
     |> Repo.insert_or_update()
   end
 end
diff --git a/lib/chessh/schema/player.ex b/lib/chessh/schema/player.ex
index 4b6a324..8eaffee 100644
--- a/lib/chessh/schema/player.ex
+++ b/lib/chessh/schema/player.ex
@@ -9,11 +9,18 @@ defmodule Chessh.Player do
     field(:password, :string, virtual: true)
     field(:hashed_password, :string)
 
+    field(:authentications, :integer, default: 0)
+
     has_many(:keys, Chessh.Key)
 
     timestamps()
   end
 
+  def authentications_changeset(player, attrs) do
+    player
+    |> cast(attrs, [:authentications])
+  end
+
   def registration_changeset(player, attrs, opts \\ []) do
     player
     |> cast(attrs, [:username, :password])
diff --git a/lib/chessh/schema/player_session.ex b/lib/chessh/schema/player_session.ex
index 84f15ee..ce3fc1f 100644
--- a/lib/chessh/schema/player_session.ex
+++ b/lib/chessh/schema/player_session.ex
@@ -1,10 +1,12 @@
 defmodule Chessh.PlayerSession do
-  alias Chessh.Repo
+  alias Chessh.{Repo, Player, PlayerSession, Utils}
   use Ecto.Schema
   import Ecto.{Query, Changeset}
+  require Logger
 
   schema "player_sessions" do
-    field(:login, :utc_datetime)
+    field(:process, :string)
+    field(:login, :utc_datetime_usec)
 
     belongs_to(:node, Chessh.Node, type: :string)
     belongs_to(:player, Chessh.Player)
@@ -17,7 +19,7 @@ defmodule Chessh.PlayerSession do
 
   def concurrent_sessions(player) do
     Repo.aggregate(
-      from(p in Chessh.PlayerSession,
+      from(p in PlayerSession,
         where: p.player_id == ^player.id
       ),
       :count
@@ -31,4 +33,48 @@ defmodule Chessh.PlayerSession do
       )
     )
   end
+
+  def player_within_concurrent_sessions_and_satisfies(username, auth_fn) do
+    max_sessions =
+      Application.get_env(:chessh, RateLimits)
+      |> Keyword.get(:max_concurrent_user_sessions)
+
+    Repo.transaction(fn ->
+      case Repo.one(
+             from(p in Player,
+               where: p.username == ^String.Chars.to_string(username),
+               lock: "FOR UPDATE"
+             )
+           ) do
+        nil ->
+          Logger.error("Player with username #{username} does not exist")
+          send(self(), {:authed, false})
+
+        player ->
+          authed =
+            auth_fn.(player) &&
+              PlayerSession.concurrent_sessions(player) < max_sessions
+
+          Repo.insert(%PlayerSession{
+            login: DateTime.utc_now(),
+            node_id: System.fetch_env!("NODE_ID"),
+            player: player,
+            # TODO: This PID may be wrong - need to determine if this PID is shared with disconnectfun
+            process: Utils.pid_to_str(self())
+          })
+
+          player
+          |> Player.authentications_changeset(%{authentications: player.authentications + 1})
+          |> Repo.update()
+
+          send(self(), {:authed, authed})
+      end
+    end)
+
+    receive do
+      {:authed, authed} -> authed
+    after
+      3_000 -> false
+    end
+  end
 end