This commit is two backports squashed into one to avoid regressions.
python: *really* remove get_event_loop
A prior commit, aa1ff990, switched away from using get_event_loop *by
default*, but this is not good enough to avoid deprecation warnings as
`asyncio.get_event_loop_policy().get_event_loop()` is *also*
deprecated. Replace this mechanism with explicit calls to
asyncio.get_new_loop() and revise the cleanup mechanisms in __del__ to
match.
python: avoid creating additional event loops per thread
"Too hasty by far!", commit 21ce2ee4 attempted to avoid deprecated
behavior altogether by calling new_event_loop() directly if there was no
loop currently running, but this has the unfortunate side effect of
potentially creating multiple event loops per thread if tests
instantiate multiple QMP connections in a single thread. This behavior
is apparently not well-defined and causes problems in some, but not all,
combinations of Python interpreter version and platform environment.
Partially revert to Daniel Berrange's original patch, which calls
get_event_loop and simply suppresses the deprecation warning in
Python<=3.13. This time, however, additionally register new loops
created with new_event_loop() so that future calls to get_event_loop()
will return the loop already created.
Reported-by: Richard W.M. Jones <rjo...@redhat.com>
Reported-by: Daniel P. Berrangé <berra...@redhat.com>
Signed-off-by: John Snow <js...@redhat.com>
cherry picked from commit
python-qemu-qmp@21ce2ee4f2df87efe84a27b9c5112487f4670622
cherry picked from commit
python-qemu-qmp@c08fb82b38212956ccffc03fc6d015c3979f42fe
Signed-off-by: John Snow <js...@redhat.com>
Reviewed-by: Daniel P. Berrangé <berra...@redhat.com>
---
python/qemu/qmp/legacy.py | 46 +++++++++++++++++++++++---------------
python/qemu/qmp/qmp_tui.py | 10 ++-------
python/qemu/qmp/util.py | 27 ++++++++++++++++++++++
3 files changed, 57 insertions(+), 26 deletions(-)
diff --git a/python/qemu/qmp/legacy.py b/python/qemu/qmp/legacy.py
index 735d42971e9..e46695ae2c8 100644
--- a/python/qemu/qmp/legacy.py
+++ b/python/qemu/qmp/legacy.py
@@ -38,6 +38,7 @@
from .error import QMPError
from .protocol import Runstate, SocketAddrT
from .qmp_client import QMPClient
+from .util import get_or_create_event_loop
#: QMPMessage is an entire QMP message of any kind.
@@ -86,17 +87,13 @@ def __init__(self,
"server argument should be False when passing a socket")
self._qmp = QMPClient(nickname)
-
- try:
- self._aloop = asyncio.get_running_loop()
- except RuntimeError:
- # No running loop; since this is a sync shim likely to be
- # used in fully sync programs, create one if neccessary.
- self._aloop = asyncio.get_event_loop_policy().get_event_loop()
-
self._address = address
self._timeout: Optional[float] = None
+ # This is a sync shim intended for use in fully synchronous
+ # programs. Create and set an event loop if necessary.
+ self._aloop = get_or_create_event_loop()
+
if server:
assert not isinstance(self._address, socket.socket)
self._sync(self._qmp.start_server(self._address))
@@ -313,17 +310,30 @@ def send_fd_scm(self, fd: int) -> None:
self._qmp.send_fd_scm(fd)
def __del__(self) -> None:
- if self._qmp.runstate == Runstate.IDLE:
- return
+ if self._qmp.runstate != Runstate.IDLE:
+ self._qmp.logger.warning(
+ "QEMUMonitorProtocol object garbage collected without a prior "
+ "call to close()"
+ )
if not self._aloop.is_running():
- self.close()
- else:
- # Garbage collection ran while the event loop was running.
- # Nothing we can do about it now, but if we don't raise our
- # own error, the user will be treated to a lot of traceback
- # they might not understand.
+ if self._qmp.runstate != Runstate.IDLE:
+ # If the user neglected to close the QMP session and we
+ # are not currently running in an asyncio context, we
+ # have the opportunity to close the QMP session. If we
+ # do not do this, the error messages presented over
+ # dangling async resources may not make any sense to the
+ # user.
+ self.close()
+
+ if self._qmp.runstate != Runstate.IDLE:
+ # If QMP is still not quiesced, it means that the garbage
+ # collector ran from a context within the event loop and we
+ # are simply too late to take any corrective action. Raise
+ # our own error to give meaningful feedback to the user in
+ # order to prevent pages of asyncio stacktrace jargon.
raise QMPError(
- "QEMUMonitorProtocol.close()"
- " was not called before object was garbage collected"
+ "QEMUMonitorProtocol.close() was not called before object was "
+ "garbage collected, and could not be closed due to GC running "
+ "in the event loop"
)
diff --git a/python/qemu/qmp/qmp_tui.py b/python/qemu/qmp/qmp_tui.py
index 12bdc17c99e..d946c205131 100644
--- a/python/qemu/qmp/qmp_tui.py
+++ b/python/qemu/qmp/qmp_tui.py
@@ -51,7 +51,7 @@
from .message import DeserializationError, Message, UnexpectedTypeError
from .protocol import ConnectError, Runstate
from .qmp_client import ExecInterruptedError, QMPClient
-from .util import pretty_traceback
+from .util import get_or_create_event_loop, pretty_traceback
# The name of the signal that is used to update the history list
@@ -387,13 +387,7 @@ def run(self, debug: bool = False) -> None:
"""
screen = urwid.raw_display.Screen()
screen.set_terminal_properties(256)
-
- try:
- self.aloop = asyncio.get_running_loop()
- except RuntimeError:
- # No running asyncio event loop. Create one if necessary.
- self.aloop = asyncio.get_event_loop_policy().get_event_loop()
-
+ self.aloop = get_or_create_event_loop()
self.aloop.set_debug(debug)
# Gracefully handle SIGTERM and SIGINT signals
diff --git a/python/qemu/qmp/util.py b/python/qemu/qmp/util.py
index 0b3e781373d..47ec39a8b5e 100644
--- a/python/qemu/qmp/util.py
+++ b/python/qemu/qmp/util.py
@@ -10,6 +10,7 @@
import sys
import traceback
from typing import TypeVar, cast
+import warnings
T = TypeVar('T')
@@ -20,6 +21,32 @@
# --------------------------
+def get_or_create_event_loop() -> asyncio.AbstractEventLoop:
+ """
+ Return this thread's current event loop, or create a new one.
+
+ This function behaves similarly to asyncio.get_event_loop() in
+ Python<=3.13, where if there is no event loop currently associated
+ with the current context, it will create and register one. It should
+ generally not be used in any asyncio-native applications.
+ """
+ try:
+ with warnings.catch_warnings():
+ # Python <= 3.13 will trigger deprecation warnings if no
+ # event loop is set, but will create and set a new loop.
+ warnings.simplefilter("ignore")
+ loop = asyncio.get_event_loop()
+ except RuntimeError:
+ # Python 3.14+: No event loop set for this thread,
+ # create and set one.
+ loop = asyncio.new_event_loop()
+ # Set this loop as the current thread's loop, to be returned
+ # by calls to get_event_loop() in the future.
+ asyncio.set_event_loop(loop)
+
+ return loop
+
+
async def flush(writer: asyncio.StreamWriter) -> None:
"""
Utility function to ensure a StreamWriter is *fully* drained.
--
2.50.1
