her

wisper.py

@@ -1,8 +1,20 @@
 import asyncio
+import contextlib
+import os
 from dataclasses import dataclass, field
 from datetime import datetime, timezone
 
 
+def _positive_int_env(name: str, default: int) -> int:
+    raw_value = os.getenv(name, "").strip()
+    if not raw_value:
+        return default
+    try:
+        return max(1, int(raw_value))
+    except ValueError:
+        return default
+
+
 @dataclass(slots=True)
 class WisperEvent:
     role: str
@@ -19,19 +31,29 @@ class WisperBus:
     def __init__(self) -> None:
         self._subscribers: set[asyncio.Queue[WisperEvent]] = set()
         self._lock = asyncio.Lock()
+        self._subscriber_snapshot: tuple[asyncio.Queue[WisperEvent], ...] = ()
+        self._subscriber_queue_size = _positive_int_env(
+            "WISPER_SUBSCRIBER_QUEUE_SIZE", 512
+        )
 
     async def subscribe(self) -> asyncio.Queue[WisperEvent]:
-        queue: asyncio.Queue[WisperEvent] = asyncio.Queue()
+        queue: asyncio.Queue[WisperEvent] = asyncio.Queue(
+            maxsize=self._subscriber_queue_size
+        )
         async with self._lock:
             self._subscribers.add(queue)
+            self._subscriber_snapshot = tuple(self._subscribers)
         return queue
 
     async def unsubscribe(self, queue: asyncio.Queue[WisperEvent]) -> None:
         async with self._lock:
             self._subscribers.discard(queue)
+            self._subscriber_snapshot = tuple(self._subscribers)
 
     async def publish(self, event: WisperEvent) -> None:
-        async with self._lock:
-            subscribers = list(self._subscribers)
-        for queue in subscribers:
-            queue.put_nowait(event)
+        for queue in self._subscriber_snapshot:
+            if queue.full():
+                with contextlib.suppress(asyncio.QueueEmpty):
+                    queue.get_nowait()
+            with contextlib.suppress(asyncio.QueueFull):
+                queue.put_nowait(event)