feat(socket): add cache mechanism for SocketSignal

ophyd_devices/utils/socket.py

@@ -3,6 +3,7 @@ import functools
 import socket
 import time
 import typing
+import uuid
 
 import numpy as np
 from bec_lib import bec_logger
@@ -82,8 +83,28 @@ def data_type(val):
 
 
 class SocketSignal(abc.ABC, Signal):
+    """
+    Base class for signals that interact with a socket connection. Subclasses
+    must implement the '_socket_get'and 'socket_set' methods to define how to
+    read from and write to the socket respectively. The signal also implements
+    an in-built caching mechanism if 'get' is called in a callback
+    from a subscription to avoid multiple socket reads in a recursion. It is important
+    that children keep the logic in 'read' and 'get' and implement the socket read logic
+    in '_socket_get' to ensure the caching mechanism works correctly.
+
+    Args:
+        name (str): The name of the signal.
+        readback_timeout (float): Time in seconds to wait between socket read attempts before
+                                  returning cached value.
+    """
+
     SUB_SETPOINT = "setpoint"
 
+    def __init__(self, *, name, **kwargs):
+
+        super().__init__(name=name, **kwargs)
+        self._active_socket_callbacks: set[str] = set()
+
     @abc.abstractmethod
     def _socket_get(self): ...
 
@@ -91,9 +112,22 @@ class SocketSignal(abc.ABC, Signal):
     def _socket_set(self, val): ...
 
     def get(self):
+        old_value = self._readback
         self._readback = self._socket_get()
+        timestamp = time.time()
+        self._metadata["timestamp"] = timestamp
+        self._run_subs(
+            sub_type=self.SUB_VALUE, old_value=old_value, value=self._readback, timestamp=timestamp
+        )
         return self._readback
 
+    def _run_subs(self, *args, sub_type, **kwargs):
+        if sub_type in self._active_socket_callbacks:
+            return
+        self._active_socket_callbacks.add(sub_type)
+        super()._run_subs(*args, sub_type=sub_type, **kwargs)
+        self._active_socket_callbacks.remove(sub_type)
+
     def put(
         self,
         value,