初始化提交

backend/app/services/event_bus.py

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+"""进程内 SSE 事件总线。
+
+后台任务 ``append_event`` 写入 DB（持久化）后，同时 publish 到本总线；SSE generator
+从内存队列实时读取并转发给前端，避免轮询 DB 带来的延迟与开销。
+
+约束：仅进程内有效，进程重启即失。多进程 / 多副本部署需替换为 Redis Pub/Sub 等共享
+通道；本地开发（单进程 uvicorn）适用。事件历史仍以 DB 为持久事实源，总线仅承担实时转发。
+"""
+
+from __future__ import annotations
+
+import asyncio
+from collections import defaultdict
+
+from app.schemas.runtime import EventResponse
+
+_TERMINAL_EVENT_TYPES = {"run.completed", "run.failed", "run.cancelled"}
+
+
+class RunEventBus:
+    """按 run_id 缓存事件并广播给订阅者。"""
+
+    def __init__(self) -> None:
+        self._events: dict[str, list[EventResponse]] = defaultdict(list)
+        self._subscribers: dict[str, list[asyncio.Queue[EventResponse]]] = defaultdict(list)
+
+    def publish(self, run_id: str, event: EventResponse) -> None:
+        self._events[run_id].append(event)
+        for queue in self._subscribers.get(run_id, []):
+            queue.put_nowait(event)
+
+    def list_after(self, run_id: str, *, after_sequence: int) -> list[EventResponse]:
+        """返回 run 内 sequence 大于 after_sequence 的事件（用于断线重连补发）。"""
+        events = self._events.get(run_id, [])
+        if after_sequence <= 0:
+            return list(events)
+        return [event for event in events if event.sequence > after_sequence]
+
+    def subscribe(self, run_id: str) -> asyncio.Queue[EventResponse]:
+        queue: asyncio.Queue[EventResponse] = asyncio.Queue()
+        self._subscribers[run_id].append(queue)
+        return queue
+
+    def unsubscribe(self, run_id: str, queue: asyncio.Queue[EventResponse]) -> None:
+        subscribers = self._subscribers.get(run_id)
+        if subscribers is None:
+            return
+        self._subscribers[run_id] = [q for q in subscribers if q is not queue]
+
+    @staticmethod
+    def is_terminal(event: EventResponse) -> bool:
+        return event.type in _TERMINAL_EVENT_TYPES
+
+
+bus = RunEventBus()