Add logic to handle EstablishedPeer messages

server/game_connection_matrix.py

@@ -0,0 +1,22 @@
+from collections import defaultdict
+
+
+class ConnectionMatrix:
+    def __init__(self, established_peers: dict[int, set[int]]):
+        self.established_peers = established_peers
+
+    def get_unconnected_peer_ids(self) -> set[int]:
+        unconnected_peer_ids: set[int] = set()
+
+        players_by_num_peers = defaultdict(list)
+        for player_id, peer_ids in self.established_peers.items():
+            players_by_num_peers[len(peer_ids)].append((player_id, peer_ids))
+
+        connected_peers = dict(self.established_peers)
+        for num_connected, peers in sorted(players_by_num_peers.items()):
+            if num_connected < len(connected_peers) - 1:
+                for player_id, peer_ids in peers:
+                    unconnected_peer_ids.add(player_id)
+                    del connected_peers[player_id]
+
+        return unconnected_peer_ids

server/gameconnection.py

@@ -6,7 +6,7 @@
 import contextlib
 import json
 import logging
-from typing import Any
+from typing import Any, Optional
 
 from sqlalchemy import select
 
@@ -62,6 +62,10 @@ def __init__(
         self.player = player
         player.game_connection = self  # Set up weak reference to self
         self.game = game
+        # None if the EstablishedPeers message is not implemented by the game
+        # version/mode used by the player. For instance, matchmaker might have
+        # it, but custom games might not.
+        self.established_peer_ids: Optional[set[int]] = None
 
         self.setup_timeout = setup_timeout
 
@@ -568,7 +572,16 @@ async def handle_established_peers(
             established a connection to. Is a list stored in a string, separated
             by spaces. As an example: "1321 22 33 43221 2132"
         """
-        pass
+        if int(peer_id) != self.player.id:
+            # TODO: We could capture all reported peer statuses here and
+            # reconcile them similar to how we do with game results in order to
+            # detect discrepancies between what players are reporting.
+            return
+
+        self.established_peer_ids = set(
+            int(peer_id)
+            for peer_id in peer_connected_to.split(" ")
+        )
 
     def _mark_dirty(self):
         if self.game:

server/games/game.py

@@ -17,6 +17,7 @@
     game_stats,
     matchmaker_queue_game
 )
+from server.game_connection_matrix import ConnectionMatrix
 from server.games.game_results import (
     ArmyOutcome,
     ArmyReportedOutcome,
@@ -211,13 +212,41 @@ def players(self) -> list[Player]:
 
     def get_connected_players(self) -> list[Player]:
         """
-        Get a collection of all players currently connected to the game.
+        Get a collection of all players currently connected to the host.
         """
         return [
             player for player in self._connections.keys()
             if player.id in self._configured_player_ids
         ]
 
+    def get_unconnected_players_from_peer_matrix(
+        self,
+    ) -> Optional[list[Player]]:
+        """
+        Get a list of players who are not fully connected to the game based on
+        the established peers matrix if possible. The EstablishedPeers messages
+        might not be implemented by the game in which case this returns None.
+        """
+        if any(
+            conn.established_peer_ids is None
+            for conn in self._connections.values()
+        ):
+            return None
+
+        matrix = ConnectionMatrix(
+            established_peers={
+                player.id: conn.established_peer_ids
+                for player, conn in self._connections.items()
+            }
+        )
+        unconnected_peer_ids = matrix.get_unconnected_peer_ids()
+
+        return [
+            player
+            for player in self._connections.keys()
+            if player.id in unconnected_peer_ids
+        ]
+
     def _is_observer(self, player: Player) -> bool:
         army = self.get_player_option(player.id, "Army")
         return army is None or army < 0

server/ladder_service/ladder_service.py

@@ -667,6 +667,12 @@ async def launch_match(
         try:
             await game.wait_launched(60 + 10 * len(guests))
         except asyncio.TimeoutError:
+            unconnected_players = game.get_unconnected_players_from_peer_matrix()
+            if unconnected_players is not None:
+                raise NotConnectedError(unconnected_players)
+
+            # If the connection matrix was not available, fall back to looking
+            # at who was connected to the host only.
             connected_players = game.get_connected_players()
             raise NotConnectedError([
                 player for player in guests

tests/unit_tests/test_connection_matrix.py

@@ -0,0 +1,246 @@
+from server.game_connection_matrix import ConnectionMatrix
+
+
+def test_all_connected():
+    # One by hand example
+    matrix = ConnectionMatrix(
+        established_peers={
+            0: {1, 2, 3},
+            1: {0, 2, 3},
+            2: {0, 1, 3},
+            3: {0, 1, 2},
+        },
+    )
+    assert matrix.get_unconnected_peer_ids() == set()
+
+    # Check every fully connected grid, including the empty grid
+    for num_players in range(0, 16 + 1):
+        matrix = ConnectionMatrix(
+            established_peers={
+                player_id: {
+                    peer_id
+                    for peer_id in range(num_players)
+                    if peer_id != player_id
+                }
+                for player_id in range(num_players)
+            },
+        )
+        assert matrix.get_unconnected_peer_ids() == set()
+
+
+def test_1v1_not_connected():
+    matrix = ConnectionMatrix(
+        established_peers={
+            0: set(),
+            1: set(),
+        },
+    )
+    assert matrix.get_unconnected_peer_ids() == {0, 1}
+
+
+def test_2v2_one_player_not_connected():
+    # 0 is not connected to anyone
+    matrix = ConnectionMatrix(
+        established_peers={
+            0: set(),
+            1: {2, 3},
+            2: {1, 3},
+            3: {1, 2},
+        },
+    )
+    assert matrix.get_unconnected_peer_ids() == {0}
+
+
+def test_2v2_two_players_not_connected():
+    # 0 is not connected to anyone
+    # 1 is not connected to anyone
+    matrix = ConnectionMatrix(
+        established_peers={
+            0: set(),
+            1: set(),
+            2: {3},
+            3: {2},
+        },
+    )
+    assert matrix.get_unconnected_peer_ids() == {0, 1}
+
+
+def test_2v2_not_connected():
+    # Not possible for only 3 players to be completely disconnected in a 4
+    # player game. Either 1, 2, or all can be disconnected.
+    matrix = ConnectionMatrix(
+        established_peers={
+            0: set(),
+            1: set(),
+            2: set(),
+            3: set(),
+        },
+    )
+    assert matrix.get_unconnected_peer_ids() == {0, 1, 2, 3}
+
+
+def test_2v2_one_pair_not_connected():
+    # 0 and 1 are not connected to each other
+    matrix = ConnectionMatrix(
+        established_peers={
+            0: {2, 3},
+            1: {2, 3},
+            2: {0, 1, 3},
+            3: {0, 1, 2},
+        },
+    )
+    assert matrix.get_unconnected_peer_ids() == {0, 1}
+
+
+def test_2v2_two_pairs_not_connected():
+    # 0 and 1 are not connected to each other
+    # 1 and 2 are not connected to each other
+    matrix = ConnectionMatrix(
+        established_peers={
+            0: {2, 3},
+            1: {3},
+            2: {0, 3},
+            3: {0, 1, 2},
+        },
+    )
+    assert matrix.get_unconnected_peer_ids() == {1}
+
+
+def test_2v2_two_disjoint_pairs_not_connected():
+    # 0 and 1 are not connected to each other
+    # 2 and 3 are not connected to each other
+    matrix = ConnectionMatrix(
+        established_peers={
+            0: {2, 3},
+            1: {2, 3},
+            2: {0, 1},
+            3: {0, 1},
+        },
+    )
+    assert matrix.get_unconnected_peer_ids() == {0, 1, 2, 3}
+
+
+def test_2v2_three_pairs_not_connected():
+    # 0 and 1 are not connected to each other
+    # 1 and 2 are not connected to each other
+    # 2 and 3 are not connected to each other
+    matrix = ConnectionMatrix(
+        established_peers={
+            0: {2, 3},
+            1: {3},
+            2: {0},
+            3: {0, 1},
+        },
+    )
+    assert matrix.get_unconnected_peer_ids() == {1, 2}
+
+
+def test_3v3_one_player_not_connected():
+    # 0 is not connected to anyone
+    matrix = ConnectionMatrix(
+        established_peers={
+            0: set(),
+            1: {2, 3, 4, 5},
+            2: {1, 3, 4, 5},
+            3: {1, 2, 4, 5},
+            4: {1, 2, 3, 5},
+            5: {1, 2, 3, 4},
+        },
+    )
+    assert matrix.get_unconnected_peer_ids() == {0}
+
+
+def test_3v3_two_players_not_connected():
+    # 0 is not connected to anyone
+    # 1 is not connected to anyone
+    matrix = ConnectionMatrix(
+        established_peers={
+            0: set(),
+            1: set(),
+            2: {3, 4, 5},
+            3: {2, 4, 5},
+            4: {2, 3, 5},
+            5: {2, 3, 4},
+        },
+    )
+    assert matrix.get_unconnected_peer_ids() == {0, 1}
+
+
+def test_3v3_three_players_not_connected():
+    # 0 is not connected to anyone
+    # 1 is not connected to anyone
+    # 2 is not connected to anyone
+    matrix = ConnectionMatrix(
+        established_peers={
+            0: set(),
+            1: set(),
+            2: set(),
+            3: {4, 5},
+            4: {3, 5},
+            5: {3, 4},
+        },
+    )
+    assert matrix.get_unconnected_peer_ids() == {0, 1, 2}
+
+
+def test_3v3_four_players_not_connected():
+    # 0 is not connected to anyone
+    # 1 is not connected to anyone
+    # 2 is not connected to anyone
+    # 3 is not connected to anyone
+    matrix = ConnectionMatrix(
+        established_peers={
+            0: set(),
+            1: set(),
+            2: set(),
+            3: set(),
+            4: {5},
+            5: {4},
+        },
+    )
+    assert matrix.get_unconnected_peer_ids() == {0, 1, 2, 3}
+
+
+def test_3v3_not_connected():
+    matrix = ConnectionMatrix(
+        established_peers={
+            0: set(),
+            1: set(),
+            2: set(),
+            3: set(),
+            4: set(),
+            5: set(),
+        },
+    )
+    assert matrix.get_unconnected_peer_ids() == {0, 1, 2, 3, 4, 5}
+
+
+def test_3v3_one_pair_not_connected():
+    # 0 and 1 are not connected to each other
+    matrix = ConnectionMatrix(
+        established_peers={
+            0: {2, 3, 4, 5},
+            1: {2, 3, 4, 5},
+            2: {0, 1, 3, 4, 5},
+            3: {0, 1, 2, 4, 5},
+            4: {0, 1, 2, 3, 5},
+            5: {0, 1, 2, 3, 4},
+        },
+    )
+    assert matrix.get_unconnected_peer_ids() == {0, 1}
+
+
+def test_3v3_one_player_and_one_pair_not_connected():
+    # 0 is not connected to anyone
+    # 1 and 2 are not connected to each other
+    matrix = ConnectionMatrix(
+        established_peers={
+            0: set(),
+            1: {3, 4, 5},
+            2: {3, 4, 5},
+            3: {1, 2, 4, 5},
+            4: {1, 2, 3, 5},
+            5: {1, 2, 3, 4},
+        },
+    )
+    assert matrix.get_unconnected_peer_ids() == {0, 1, 2}