Response cache (#2)

* Response caching to reduce device loading

* Refactor response caching

* Process review comments

src/thorlabs_mff_fastcs/controllers.py

@@ -1,7 +1,10 @@
 from __future__ import annotations
 
+import asyncio
+from collections.abc import Callable, Coroutine
 from dataclasses import dataclass
-from typing import Any, Callable
+from datetime import datetime
+from typing import Any
 
 from fastcs.attributes import AttrR, AttrW
 from fastcs.connections.serial_connection import (
@@ -58,6 +61,48 @@ def read_hardware_v(self, response: bytes) -> int:
 protocol = ThorlabsAPTProtocol()
 
 
+@dataclass
+class ResponseCache:
+ _last_update: datetime | None = None
+ _response: str | None = None
+ _update_event: asyncio.Event = asyncio.Event()
+
+ def __post_init__(self) -> None:
+ self._update_event.set()
+
+ def _has_expired(self, time_step: float) -> bool:
+ if self._last_update is None:
+ return True
+ delta_t = datetime.now() - self._last_update
+ return delta_t.total_seconds() > time_step
+
+ def _update_response(self, response: str | None) -> None:
+ self._response = response
+ self._last_update = datetime.now()
+
+ async def get_response(
+ self, expiry_period: float, to_await: Coroutine[Any, Any, str | None]
+ ):
+ # Immediately short circuit if not expired
+ if self._has_expired(expiry_period):
+ # Wait if an update is in progress
+ if self._update_event.is_set():
+ self._update_event.clear() # Lock
+ response = await to_await
+ self._update_response(response)
+ self._update_event.set() # Free
+ return response
+ else:
+ await self._update_event.wait()
+
+ response = self._response
+ to_await.close() # Solves RuntimeWarning: coroutine not awaited
+ return response
+
+
+info_cache = ResponseCache()
+
+
 @dataclass
 class ThorlabsMFFHandlerW:
  cmd: Callable
@@ -81,16 +126,27 @@ class ThorlabsMFFHandlerR:
  response_size: int
  response_handler: Callable
  update_period: float = 0.2
+ cache: ResponseCache | None = None
 
  async def update(
  self,
  controller: ThorlabsMFF,
  attr: AttrR,
  ) -> None:
- response = await controller.conn.send_query(
- self.cmd(),
- self.response_size,
- )
+ if self.cache is not None:
+ response = await self.cache.get_response(
+ self.update_period,
+ controller.conn.send_query(
+ self.cmd(),
+ self.response_size,
+ ),
+ )
+ else:
+ response = await controller.conn.send_query(
+ self.cmd(),
+ self.response_size,
+ )
+
  response = self.response_handler(response)
  if attr.dtype is bool:
  await attr.set(int(response))
@@ -127,6 +183,7 @@ class ThorlabsMFF(Controller):
  90,
  protocol.read_model,
  update_period=10,
+ cache=info_cache,
  ),
  group="Information",
  )
@@ -137,6 +194,7 @@ class ThorlabsMFF(Controller):
  90,
  protocol.read_type,
  update_period=10,
+ cache=info_cache,
  ),
  group="Information",
  )
@@ -147,6 +205,7 @@ class ThorlabsMFF(Controller):
  90,
  protocol.read_serial_no,
  update_period=10,
+ cache=info_cache,
  ),
  group="Information",
  )
@@ -157,6 +216,7 @@ class ThorlabsMFF(Controller):
  90,
  protocol.read_firmware_v,
  update_period=10,
+ cache=info_cache,
  ),
  group="Information",
  )
@@ -167,6 +227,7 @@ class ThorlabsMFF(Controller):
  90,
  protocol.read_hardware_v,
  update_period=10,
+ cache=info_cache,
  ),
  group="Information",
  )