asyncio.get_event_loop raises error instead of spawning new loop when no loop is running.

>>> import uvloop, asyncio
>>> asyncio.get_event_loop()
<_UnixSelectorEventLoop running=False closed=False debug=False>
>>> uvloop.install()
>>> asyncio.get_event_loop()
Traceback (most recent call last):
  File "<python-input-4>", line 1, in <module>
    asyncio.get_event_loop()
    ~~~~~~~~~~~~~~~~~~~~~~^^
  File "/usr/local/lib/python3.13/site-packages/uvloop/__init__.py", line 206, in get_event_loop
    raise RuntimeError(
    ...<2 lines>...
    )
RuntimeError: There is no current event loop in thread 'MainThread'.
>>>

As you can see in the snippet above when run on un-patched asyncio it's returning a new loop. But uvloop raises error because of the method override which was not there in previous version inheriting the original new loop spawning function.

Got this issue with aiohttp.GunicornUVLoopWebWorker after updating uvloop to 0.22.1.
Note that uvloop==0.21.0 does work properly, and uvloop==0.22.1 does not.
For now added the following to my requirements.txt: uvloop!=0.22.1 — I hope the issue will be fixed in the next version.

Roger; I'm looking into this

Same issue here. It looks like 0.22.x's EventLoopPolicy overrides its base class asyncio.events.BaseDefaultEventLoopPolicy's get_event_loop function, and removes the creating new loop behavior.

Require uvloop version not equal to 0.22.0 and 0.22.1

Same here; uvicorn couldn't start. The thing took a while to figure out because it started to happen without code/image changes:

Traceback (most recent call last):
  File "/usr/local/bin/uvicorn", line 7, in <module>
    sys.exit(main())
             ^^^^^^
  File "/usr/local/lib/python3.11/site-packages/click/core.py", line 829, in __call__
    return self.main(*args, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/site-packages/click/core.py", line 782, in main
    rv = self.invoke(ctx)
         ^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/site-packages/click/core.py", line 1066, in invoke
    return ctx.invoke(self.callback, **ctx.params)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/site-packages/click/core.py", line 610, in invoke
    return callback(*args, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/site-packages/uvicorn/main.py", line 362, in main
    run(**kwargs)
  File "/usr/local/lib/python3.11/site-packages/uvicorn/main.py", line 386, in run
    server.run()
  File "/usr/local/lib/python3.11/site-packages/uvicorn/server.py", line 48, in run
    loop = asyncio.get_event_loop()
           ^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/site-packages/uvloop/__init__.py", line 206, in get_event_loop
    raise RuntimeError(
RuntimeError: There is no current event loop in thread 'MainThread'.

Same here, multiple project, including sglang and verl is impacted

Same here.

mlserver[mlflow]==1.7.0 failed to start

2025-10-29 13:49:42,186 [mlserver.parallel] INFO - New worker with PID 89 on default inference pool is now ready.
Process Worker-20:
Traceback (most recent call last):
  File "/usr/local/lib/python3.11/multiprocessing/process.py", line 314, in _bootstrap
    self.run()
  File "/usr/local/lib/python3.11/site-packages/mlserver/parallel/worker.py", line 70, in run
    self._ignore_signals()
  File "/usr/local/lib/python3.11/site-packages/mlserver/parallel/worker.py", line 81, in _ignore_signals
    loop = asyncio.get_event_loop()
           ^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/site-packages/uvloop/__init__.py", line 206, in get_event_loop
    raise RuntimeError(
RuntimeError: There is no current event loop in thread 'MainThread'.
Process Worker-19:
Traceback (most recent call last):
  File "/usr/local/lib/python3.11/multiprocessing/process.py", line 314, in _bootstrap
    self.run()
  File "/usr/local/lib/python3.11/site-packages/mlserver/parallel/worker.py", line 70, in run
    self._ignore_signals()
  File "/usr/local/lib/python3.11/site-packages/mlserver/parallel/worker.py", line 81, in _ignore_signals
    loop = asyncio.get_event_loop()
           ^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/site-packages/uvloop/__init__.py", line 206, in get_event_loop
    raise RuntimeError(
RuntimeError: There is no current event loop in thread 'MainThread'.
Process Worker-16:

kubectl exec -n kserve 5f9885f6d9-wzg6d -- pip list | grep -E "(uvloop|mlserver)"
Defaulted container "kserve-container" out of: kserve-container, storage-initializer (init)
mlserver                                 1.7.1
mlserver-mlflow                          1.7.1
uvloop                                   0.22.1

This diff is fixing for me (copy from BaseDefaultEventLoopPolicy):

--- a/uvloop/__init__.py    (index)
+++ b/uvloop/__init__.py    (working tree)
@@ -193,6 +193,7 @@ def __getattr__(name: str) -> _typing.Any:

         class _Local(threading.local):
             _loop: _typing.Optional[_AbstractEventLoop] = None
+            _set_called: bool = False

         def __init__(self) -> None:
             self._local = self._Local()
@@ -202,6 +203,28 @@ def __getattr__(name: str) -> _typing.Any:

             Returns an instance of EventLoop or raises an exception.
             """
+            if (self._local._loop is None and
+                    not self._local._set_called and
+                    threading.current_thread() is threading.main_thread()):
+                stacklevel = 2
+                try:
+                    f = _sys._getframe(1)
+                except AttributeError:
+                    pass
+                else:
+                    # Move up the call stack so that the warning is attached
+                    # to the line outside asyncio itself.
+                    while f:
+                        module = f.f_globals.get('__name__')
+                        if not (module == 'asyncio' or module.startswith('asyncio.')):
+                            break
+                        f = f.f_back
+                        stacklevel += 1
+                import warnings
+                warnings.warn('There is no current event loop',
+                              DeprecationWarning, stacklevel=stacklevel)
+                self.set_event_loop(self.new_event_loop())
+
             if self._local._loop is None:
                 raise RuntimeError(
                     'There is no current event loop in thread %r.'
@@ -214,6 +237,7 @@ def __getattr__(name: str) -> _typing.Any:
             self, loop: _typing.Optional[_AbstractEventLoop]
         ) -> None:
             """Set the event loop."""
+            self._local._set_called = True
             if loop is not None and not isinstance(loop, _AbstractEventLoop):
                 raise TypeError(
                     f"loop must be an instance of AbstractEventLoop or None, "

Create loop in `get_event_loop` if needed

Pin uvloop<0.22 and add sanity test for it

Create missing loop in get_event_loop in main thread

Pin uvloop<0.22 and add sanity test for it

So I ran into this and got curious why it's happening because it seems like a deliberate change. The change in behaviour has a logical reason. In py3.14 the default behaviour changed to raising a runtime error if there is no current loop. See https://docs.python.org/3/library/asyncio-eventloop.html#asyncio.get_event_loop

Even in python 3.8 and up it already resulted in deprecation warnings to rely on this behaviour. So a proper fix for this would mean applying a version guard to emit a deprecation warning for older python. This would look something like:

import warnings
from sys import version_info

...

        def get_event_loop(self) -> _AbstractEventLoop:
            """Get the event loop for the current context.

            Returns an instance of EventLoop or raises an exception.
            """
            if self._local._loop is None:
                if version_info[1] < 14:
                    // make new event loop, probably the way cpython does it as @shadchin suggested above..
                else:
                    raise RuntimeError(
                        'There is no current event loop in thread %r.'
                        % threading.current_thread().name
                    )

            return self._local._loop

That is assuming you want a version diff like this in your code. But otherwise it might be best to bump up the uvloop python version requirements.

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`asyncio.get_event_loop` raises error instead of spawning new loop when no loop is running. #702

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asyncio.get_event_loop raises error instead of spawning new loop when no loop is running. #702

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MarSoft commented on Oct 18, 2025

fantix commented on Oct 18, 2025

andylin-hao commented on Oct 20, 2025

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shadchin commented on Jan 7, 2026

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`asyncio.get_event_loop` raises error instead of spawning new loop when no loop is running. #702