server: make state-save debounce timing configurable

server/app/config.py

@@ -39,6 +39,8 @@ class StorageConfigSection(BaseModel):
     """Persistent state file location."""
 
     state_file: str = "runtime/items.json"
+    state_save_debounce_ms: int = Field(default=200, gt=0)
+    state_save_max_delay_ms: int = Field(default=1000, gt=0)
 
 
 class WorldConfigSection(BaseModel):

server/app/server.py

@@ -73,8 +73,6 @@ CLIENT_PACKET_ADAPTER = TypeAdapter(ClientPacket)
 MAX_ACTIVE_PIANO_KEYS_PER_CLIENT = 12
 PIANO_RECORDING_MAX_MS = 30_000
 PIANO_RECORDING_MAX_EVENTS = 4096
-STATE_SAVE_DEBOUNCE_MS = 200
-STATE_SAVE_MAX_DELAY_MS = 1000
 
 
 class SignalingServer:
@@ -89,6 +87,8 @@ class SignalingServer:
         max_message_size: int = 2_000_000,
         state_file: Path | None = None,
         grid_size: int = 41,
+        state_save_debounce_ms: int = 200,
+        state_save_max_delay_ms: int = 1000,
     ):
         """Initialize runtime state, TLS context, and item service."""
 
@@ -105,6 +105,8 @@ class SignalingServer:
         self.grid_size = max(1, grid_size)
         self.instance_id = str(uuid.uuid4())
         self.server_version = self._resolve_server_version()
+        self.state_save_debounce_ms = max(1, int(state_save_debounce_ms))
+        self.state_save_max_delay_ms = max(self.state_save_debounce_ms, int(state_save_max_delay_ms))
         self._pending_state_save_handle: asyncio.TimerHandle | None = None
         self._pending_state_save_started_at: float | None = None
 
@@ -160,13 +162,13 @@ class SignalingServer:
         if self._pending_state_save_started_at is None:
             self._pending_state_save_started_at = now
         elapsed_ms = int((now - self._pending_state_save_started_at) * 1000)
-        if elapsed_ms >= STATE_SAVE_MAX_DELAY_MS:
+        if elapsed_ms >= self.state_save_max_delay_ms:
             self._flush_state_save()
             return
         if self._pending_state_save_handle is not None:
             self._pending_state_save_handle.cancel()
-        remaining_ms = max(0, STATE_SAVE_MAX_DELAY_MS - elapsed_ms)
-        delay_ms = min(STATE_SAVE_DEBOUNCE_MS, remaining_ms)
+        remaining_ms = max(0, self.state_save_max_delay_ms - elapsed_ms)
+        delay_ms = min(self.state_save_debounce_ms, remaining_ms)
         self._pending_state_save_handle = loop.call_later(delay_ms / 1000, self._flush_state_save)
 
     def _is_nickname_taken(self, nickname: str, exclude_client_id: str | None = None) -> bool:
@@ -1344,5 +1346,7 @@ def run() -> None:
         max_message_size=config.network.max_message_bytes,
         state_file=state_file,
         grid_size=config.world.grid_size,
+        state_save_debounce_ms=config.storage.state_save_debounce_ms,
+        state_save_max_delay_ms=config.storage.state_save_max_delay_ms,
     )
     asyncio.run(server.start())

server/config.example.toml

@@ -21,6 +21,10 @@ level = "INFO"
 [storage]
 # Item persistence file. Relative paths are resolved from this config file directory.
 state_file = "runtime/items.json"
+# Debounce window for coalesced item-state writes.
+state_save_debounce_ms = 200
+# Maximum delay before a pending state write is forced.
+state_save_max_delay_ms = 1000
 
 [world]
 # Grid width/height in cells. Valid coordinates are 0..grid_size-1.

server/tests/test_config.py

@@ -10,6 +10,8 @@ def test_load_config_defaults_when_path_none() -> None:
     assert cfg.server.bind_ip == "127.0.0.1"
     assert cfg.network.allow_insecure_ws is True
     assert cfg.storage.state_file == "runtime/items.json"
+    assert cfg.storage.state_save_debounce_ms == 200
+    assert cfg.storage.state_save_max_delay_ms == 1000
     assert cfg.world.grid_size == 41
 
 
@@ -23,3 +25,18 @@ allow_insecure_ws = false
     )
     with pytest.raises(ValueError):
         load_config(config_path)
+
+
+def test_load_config_reads_state_save_timing(tmp_path: Path) -> None:
+    config_path = tmp_path / "config.toml"
+    config_path.write_text(
+        """
+[storage]
+state_file = "runtime/items.json"
+state_save_debounce_ms = 150
+state_save_max_delay_ms = 900
+""".strip()
+    )
+    cfg = load_config(config_path)
+    assert cfg.storage.state_save_debounce_ms == 150
+    assert cfg.storage.state_save_max_delay_ms == 900