fix!: Fix SingleThreadedAgentRuntime busy loop (#4855)

* Fix high cpu usage

* Use queue for shutdown

* mypy fixes

* formatting

* missing import

python/packages/autogen-core/src/autogen_core/_queue.py

@@ -0,0 +1,264 @@
+# Copy of Asyncio queue: https://github.com/python/cpython/blob/main/Lib/asyncio/queues.py
+# So that shutdown can be used in <3.13
+# Modified to work outside of the asyncio package
+
+import asyncio
+import collections
+import threading
+from typing import Generic, TypeVar
+
+_global_lock = threading.Lock()
+
+
+class _LoopBoundMixin:
+    _loop = None
+
+    def _get_loop(self) -> asyncio.AbstractEventLoop:
+        loop = asyncio.get_running_loop()
+
+        if self._loop is None:
+            with _global_lock:
+                if self._loop is None:
+                    self._loop = loop
+        if loop is not self._loop:
+            raise RuntimeError(f"{self!r} is bound to a different event loop")
+        return loop
+
+
+class QueueShutDown(Exception):
+    """Raised when putting on to or getting from a shut-down Queue."""
+
+    pass
+
+
+T = TypeVar("T")
+
+
+class Queue(_LoopBoundMixin, Generic[T]):
+    def __init__(self, maxsize: int = 0):
+        self._maxsize = maxsize
+        self._getters = collections.deque[asyncio.Future[None]]()
+        self._putters = collections.deque[asyncio.Future[None]]()
+        self._unfinished_tasks = 0
+        self._finished = asyncio.Event()
+        self._finished.set()
+        self._queue = collections.deque[T]()
+        self._is_shutdown = False
+
+    # These three are overridable in subclasses.
+
+    def _get(self) -> T:
+        return self._queue.popleft()
+
+    def _put(self, item: T) -> None:
+        self._queue.append(item)
+
+    # End of the overridable methods.
+
+    def _wakeup_next(self, waiters: collections.deque[asyncio.Future[None]]) -> None:
+        # Wake up the next waiter (if any) that isn't cancelled.
+        while waiters:
+            waiter = waiters.popleft()
+            if not waiter.done():
+                waiter.set_result(None)
+                break
+
+    def __repr__(self) -> str:
+        return f"<{type(self).__name__} at {id(self):#x} {self._format()}>"
+
+    def __str__(self) -> str:
+        return f"<{type(self).__name__} {self._format()}>"
+
+    def _format(self) -> str:
+        result = f"maxsize={self._maxsize!r}"
+        if getattr(self, "_queue", None):
+            result += f" _queue={list(self._queue)!r}"
+        if self._getters:
+            result += f" _getters[{len(self._getters)}]"
+        if self._putters:
+            result += f" _putters[{len(self._putters)}]"
+        if self._unfinished_tasks:
+            result += f" tasks={self._unfinished_tasks}"
+        if self._is_shutdown:
+            result += " shutdown"
+        return result
+
+    def qsize(self) -> int:
+        """Number of items in the queue."""
+        return len(self._queue)
+
+    @property
+    def maxsize(self) -> int:
+        """Number of items allowed in the queue."""
+        return self._maxsize
+
+    def empty(self) -> bool:
+        """Return True if the queue is empty, False otherwise."""
+        return not self._queue
+
+    def full(self) -> bool:
+        """Return True if there are maxsize items in the queue.
+
+        Note: if the Queue was initialized with maxsize=0 (the default),
+        then full() is never True.
+        """
+        if self._maxsize <= 0:
+            return False
+        else:
+            return self.qsize() >= self._maxsize
+
+    async def put(self, item: T) -> None:
+        """Put an item into the queue.
+
+        Put an item into the queue. If the queue is full, wait until a free
+        slot is available before adding item.
+
+        Raises QueueShutDown if the queue has been shut down.
+        """
+        while self.full():
+            if self._is_shutdown:
+                raise QueueShutDown
+            putter = self._get_loop().create_future()
+            self._putters.append(putter)
+            try:
+                await putter
+            except:
+                putter.cancel()  # Just in case putter is not done yet.
+                try:
+                    # Clean self._putters from canceled putters.
+                    self._putters.remove(putter)
+                except ValueError:
+                    # The putter could be removed from self._putters by a
+                    # previous get_nowait call or a shutdown call.
+                    pass
+                if not self.full() and not putter.cancelled():
+                    # We were woken up by get_nowait(), but can't take
+                    # the call.  Wake up the next in line.
+                    self._wakeup_next(self._putters)
+                raise
+        return self.put_nowait(item)
+
+    def put_nowait(self, item: T) -> None:
+        """Put an item into the queue without blocking.
+
+        If no free slot is immediately available, raise QueueFull.
+
+        Raises QueueShutDown if the queue has been shut down.
+        """
+        if self._is_shutdown:
+            raise QueueShutDown
+        if self.full():
+            raise asyncio.QueueFull
+        self._put(item)
+        self._unfinished_tasks += 1
+        self._finished.clear()
+        self._wakeup_next(self._getters)
+
+    async def get(self) -> T:
+        """Remove and return an item from the queue.
+
+        If queue is empty, wait until an item is available.
+
+        Raises QueueShutDown if the queue has been shut down and is empty, or
+        if the queue has been shut down immediately.
+        """
+        while self.empty():
+            if self._is_shutdown and self.empty():
+                raise QueueShutDown
+            getter = self._get_loop().create_future()
+            self._getters.append(getter)
+            try:
+                await getter
+            except:
+                getter.cancel()  # Just in case getter is not done yet.
+                try:
+                    # Clean self._getters from canceled getters.
+                    self._getters.remove(getter)
+                except ValueError:
+                    # The getter could be removed from self._getters by a
+                    # previous put_nowait call, or a shutdown call.
+                    pass
+                if not self.empty() and not getter.cancelled():
+                    # We were woken up by put_nowait(), but can't take
+                    # the call.  Wake up the next in line.
+                    self._wakeup_next(self._getters)
+                raise
+        return self.get_nowait()
+
+    def get_nowait(self) -> T:
+        """Remove and return an item from the queue.
+
+        Return an item if one is immediately available, else raise QueueEmpty.
+
+        Raises QueueShutDown if the queue has been shut down and is empty, or
+        if the queue has been shut down immediately.
+        """
+        if self.empty():
+            if self._is_shutdown:
+                raise QueueShutDown
+            raise asyncio.QueueEmpty
+        item = self._get()
+        self._wakeup_next(self._putters)
+        return item
+
+    def task_done(self) -> None:
+        """Indicate that a formerly enqueued task is complete.
+
+        Used by queue consumers. For each get() used to fetch a task,
+        a subsequent call to task_done() tells the queue that the processing
+        on the task is complete.
+
+        If a join() is currently blocking, it will resume when all items have
+        been processed (meaning that a task_done() call was received for every
+        item that had been put() into the queue).
+
+        shutdown(immediate=True) calls task_done() for each remaining item in
+        the queue.
+
+        Raises ValueError if called more times than there were items placed in
+        the queue.
+        """
+        if self._unfinished_tasks <= 0:
+            raise ValueError("task_done() called too many times")
+        self._unfinished_tasks -= 1
+        if self._unfinished_tasks == 0:
+            self._finished.set()
+
+    async def join(self) -> None:
+        """Block until all items in the queue have been gotten and processed.
+
+        The count of unfinished tasks goes up whenever an item is added to the
+        queue. The count goes down whenever a consumer calls task_done() to
+        indicate that the item was retrieved and all work on it is complete.
+        When the count of unfinished tasks drops to zero, join() unblocks.
+        """
+        if self._unfinished_tasks > 0:
+            await self._finished.wait()
+
+    def shutdown(self, immediate: bool = False) -> None:
+        """Shut-down the queue, making queue gets and puts raise QueueShutDown.
+
+        By default, gets will only raise once the queue is empty. Set
+        'immediate' to True to make gets raise immediately instead.
+
+        All blocked callers of put() and get() will be unblocked. If
+        'immediate', a task is marked as done for each item remaining in
+        the queue, which may unblock callers of join().
+        """
+        self._is_shutdown = True
+        if immediate:
+            while not self.empty():
+                self._get()
+                if self._unfinished_tasks > 0:
+                    self._unfinished_tasks -= 1
+            if self._unfinished_tasks == 0:
+                self._finished.set()
+        # All getters need to re-check queue-empty to raise ShutDown
+        while self._getters:
+            getter = self._getters.popleft()
+            if not getter.done():
+                getter.set_result(None)
+        while self._putters:
+            putter = self._putters.popleft()
+            if not putter.done():
+                putter.set_result(None)