chore: import upstream snapshot with attribution

frigate/comms/inter_process.py

@@ -0,0 +1,87 @@
+"""Facilitates communication between processes."""
+
+import logging
+import multiprocessing as mp
+import threading
+from collections.abc import Callable
+from multiprocessing.synchronize import Event as MpEvent
+from typing import Any
+
+import zmq
+
+from frigate.comms.base_communicator import Communicator
+
+logger = logging.getLogger(__name__)
+
+SOCKET_REP_REQ = "ipc:///tmp/cache/comms"
+
+
+class InterProcessCommunicator(Communicator):
+    def __init__(self) -> None:
+        self.context = zmq.Context()
+        self.socket = self.context.socket(zmq.REP)
+        self.socket.bind(SOCKET_REP_REQ)
+        self.stop_event: MpEvent = mp.Event()
+
+    def publish(self, topic: str, payload: Any, retain: bool = False) -> None:
+        """There is no communication back to the processes."""
+        pass
+
+    def subscribe(self, receiver: Callable) -> None:
+        self._dispatcher = receiver
+        self.reader_thread = threading.Thread(target=self.read)
+        self.reader_thread.start()
+
+    def read(self) -> None:
+        while not self.stop_event.is_set():
+            while True:  # load all messages that are queued
+                has_message, _, _ = zmq.select([self.socket], [], [], 1)
+
+                if not has_message:
+                    break
+
+                try:
+                    raw = self.socket.recv_json(flags=zmq.NOBLOCK)
+
+                    if isinstance(raw, list):
+                        (topic, value) = raw
+                        response = self._dispatcher(topic, value)
+                    else:
+                        logging.warning(
+                            f"Received unexpected data type in ZMQ recv_json: {type(raw)}"
+                        )
+                        response = None
+
+                    if response is not None:
+                        self.socket.send_json(response)
+                    else:
+                        self.socket.send_json([])
+                except zmq.ZMQError:
+                    break
+
+    def stop(self) -> None:
+        self.stop_event.set()
+        self.reader_thread.join()
+        self.socket.close(linger=0)
+        self.context.destroy(linger=0)
+
+
+class InterProcessRequestor:
+    """Simplifies sending data to InterProcessCommunicator and getting a reply."""
+
+    def __init__(self) -> None:
+        self.context = zmq.Context()
+        self.socket = self.context.socket(zmq.REQ)
+        self.socket.connect(SOCKET_REP_REQ)
+
+    def send_data(self, topic: str, data: Any) -> Any:
+        """Sends data and then waits for reply."""
+        try:
+            self.socket.send_json((topic, data))
+            return self.socket.recv_json()
+        except zmq.ZMQError:
+            return ""
+
+    def stop(self) -> None:
+        self.socket.close(linger=0)
+        self.context.destroy(linger=0)