Merge pull request #503 from Kraigie/gateway-state-machine

Convert shard sessions into state machines

appup.ex

@@ -6,7 +6,9 @@
     # Upgrade instructions
     {'0.9.0-alpha1',
      [
-       {:load_module, Nostrum.Cache.GuildCache}
+       # Top shard supervisor was not registered, so could not restart shard
+       # supervisor to load new gateway logic
+       {:restart_application, :nostrum}
      ]},
     {'0.8.0',
      [
@@ -17,7 +19,7 @@
     # Downgrade instructions
     {'0.9.0-alpha1',
      [
-       {:load_module, Nostrum.Cache.GuildCache}
+       {:restart_application, :nostrum}
      ]},
     {'0.8.0',
      [

lib/nostrum/application.ex

@@ -36,7 +36,7 @@ defmodule Nostrum.Application do
 
     if Application.get_env(:nostrum, :dev),
       do: Supervisor.start_link(children ++ [DummySupervisor], strategy: :one_for_one),
-      else: Supervisor.start_link(children, strategy: :one_for_one)
+      else: Supervisor.start_link(children, strategy: :one_for_one, name: Nostrum.Supervisor)
   end
 
   defp check_executables do

lib/nostrum/shard/event.ex

@@ -20,42 +20,42 @@ defmodule Nostrum.Shard.Event do
 
     if payload.t == :READY do
       Logger.info("READY")
-      %{state | session: payload.d.session_id}
+
+      {%{state | session: payload.d.session_id, resume_gateway: payload.d.resume_gateway_url}, []}
     else
-      state
+      {state, []}
     end
   end
 
   def handle(:heartbeat, _payload, state) do
     Logger.debug("HEARTBEAT PING")
-    {state, Payload.heartbeat_payload(state.seq)}
+    {{state, Payload.heartbeat_payload(state.seq)}, []}
   end
 
   def handle(:heartbeat_ack, _payload, state) do
     Logger.debug("HEARTBEAT_ACK")
-    %{state | last_heartbeat_ack: DateTime.utc_now(), heartbeat_ack: true}
+    {%{state | last_heartbeat_ack: DateTime.utc_now(), heartbeat_ack: true}, []}
   end
 
-  def handle(:hello, payload, state) do
-    state = %{
-      state
-      | heartbeat_interval: payload.d.heartbeat_interval
-    }
-
-    GenServer.cast(state.conn_pid, :heartbeat)
+  def handle(:hello, payload, old_state) do
+    state = Map.put(old_state, :heartbeat_interval, payload.d.heartbeat_interval)
+    # Jitter it as documented. But only for Hello - the subsequent timeouts
+    # must not jitter it anymore, but send out at this interval.
+    heartbeat_next = :rand.uniform(state.heartbeat_interval)
+    heartbeat_action = {:state_timeout, heartbeat_next, :send_heartbeat}
 
     if session_exists?(state) do
       Logger.info("RESUMING")
-      {state, Payload.resume_payload(state)}
+      {{state, Payload.resume_payload(state)}, heartbeat_action}
     else
       Logger.info("IDENTIFYING")
-      {state, Payload.identity_payload(state)}
+      {{state, Payload.identity_payload(state)}, heartbeat_action}
     end
   end
 
   def handle(:invalid_session, _payload, state) do
     Logger.info("INVALID_SESSION")
-    {state, Payload.identity_payload(state)}
+    {{state, Payload.identity_payload(state)}, []}
   end
 
   def handle(:reconnect, _payload, state) do