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[PULL 2/4] python/machine: raise VMLaunchFailure exception from launch()
From: |
John Snow |
Subject: |
[PULL 2/4] python/machine: raise VMLaunchFailure exception from launch() |
Date: |
Wed, 2 Feb 2022 20:59:44 -0500 |
This allows us to pack in some extra information about the failure,
which guarantees that if the caller did not *intentionally* cause a
failure (by capturing this Exception), some pretty good clues will be
printed at the bottom of the traceback information.
This will help make failures in the event of a non-negative return code
more obvious when they go unhandled; the current behavior in
_post_shutdown() is to print a warning message only in the event of
signal-based terminations (for negative return codes).
(Note: In Python, catching BaseException instead of Exception catches a
broader array of Exception events, including SystemExit and
KeyboardInterrupt. We do not want to "wrap" such exceptions as a
VMLaunchFailure, because that will 'downgrade' the exception from a
BaseException to a regular Exception. We do, however, want to perform
cleanup in either case, so catch on the broadest scope and
wrap-and-re-raise only in the more targeted scope.)
Signed-off-by: John Snow <jsnow@redhat.com>
Reviewed-by: Hanna Reitz <hreitz@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Message-id: 20220201041134.1237016-3-jsnow@redhat.com
Signed-off-by: John Snow <jsnow@redhat.com>
---
python/qemu/machine/machine.py | 45 ++++++++++++++++++++---
tests/qemu-iotests/tests/mirror-top-perms | 3 +-
2 files changed, 40 insertions(+), 8 deletions(-)
diff --git a/python/qemu/machine/machine.py b/python/qemu/machine/machine.py
index 67ab06ca2b..a5972fab4d 100644
--- a/python/qemu/machine/machine.py
+++ b/python/qemu/machine/machine.py
@@ -74,6 +74,35 @@ class QEMUMachineAddDeviceError(QEMUMachineError):
"""
+class VMLaunchFailure(QEMUMachineError):
+ """
+ Exception raised when a VM launch was attempted, but failed.
+ """
+ def __init__(self, exitcode: Optional[int],
+ command: str, output: Optional[str]):
+ super().__init__(exitcode, command, output)
+ self.exitcode = exitcode
+ self.command = command
+ self.output = output
+
+ def __str__(self) -> str:
+ ret = ''
+ if self.__cause__ is not None:
+ name = type(self.__cause__).__name__
+ reason = str(self.__cause__)
+ if reason:
+ ret += f"{name}: {reason}"
+ else:
+ ret += f"{name}"
+ ret += '\n'
+
+ if self.exitcode is not None:
+ ret += f"\tExit code: {self.exitcode}\n"
+ ret += f"\tCommand: {self.command}\n"
+ ret += f"\tOutput: {self.output}\n"
+ return ret
+
+
class AbnormalShutdown(QEMUMachineError):
"""
Exception raised when a graceful shutdown was requested, but not performed.
@@ -397,7 +426,7 @@ def launch(self) -> None:
try:
self._launch()
- except:
+ except BaseException as exc:
# We may have launched the process but it may
# have exited before we could connect via QMP.
# Assume the VM didn't launch or is exiting.
@@ -408,11 +437,15 @@ def launch(self) -> None:
else:
self._post_shutdown()
- LOG.debug('Error launching VM')
- if self._qemu_full_args:
- LOG.debug('Command: %r', ' '.join(self._qemu_full_args))
- if self._iolog:
- LOG.debug('Output: %r', self._iolog)
+ if isinstance(exc, Exception):
+ raise VMLaunchFailure(
+ exitcode=self.exitcode(),
+ command=' '.join(self._qemu_full_args),
+ output=self._iolog
+ ) from exc
+
+ # Don't wrap 'BaseException'; doing so would downgrade
+ # that exception. However, we still want to clean up.
raise
def _launch(self) -> None:
diff --git a/tests/qemu-iotests/tests/mirror-top-perms
b/tests/qemu-iotests/tests/mirror-top-perms
index 0a51a613f3..b5849978c4 100755
--- a/tests/qemu-iotests/tests/mirror-top-perms
+++ b/tests/qemu-iotests/tests/mirror-top-perms
@@ -21,7 +21,6 @@
import os
-from qemu.aqmp import ConnectError
from qemu.machine import machine
from qemu.qmp import QMPConnectError
@@ -107,7 +106,7 @@ class TestMirrorTopPerms(iotests.QMPTestCase):
self.vm_b.launch()
print('ERROR: VM B launched successfully, '
'this should not have happened')
- except (QMPConnectError, ConnectError):
+ except (QMPConnectError, machine.VMLaunchFailure):
assert 'Is another process using the image' in self.vm_b.get_log()
result = self.vm.qmp('block-job-cancel',
--
2.31.1
- [PULL 0/4] Python patches, John Snow, 2022/02/02
- [PULL 1/4] python/aqmp: Fix negotiation with pre-"oob" QEMU, John Snow, 2022/02/02
- [PULL 2/4] python/machine: raise VMLaunchFailure exception from launch(),
John Snow <=
- [PULL 4/4] python/aqmp: add socket bind step to legacy.py, John Snow, 2022/02/02
- [PULL 3/4] python: upgrade mypy to 0.780, John Snow, 2022/02/02
- Re: [PULL 0/4] Python patches, Peter Maydell, 2022/02/03
- Re: [PULL 0/4] Python patches, John Snow, 2022/02/03
- Re: [PULL 0/4] Python patches, Peter Maydell, 2022/02/03
- Re: [PULL 0/4] Python patches, John Snow, 2022/02/03
- Re: [PULL 0/4] Python patches, Peter Maydell, 2022/02/08
- Re: [PULL 0/4] Python patches, John Snow, 2022/02/15
- Re: [PULL 0/4] Python patches, Peter Maydell, 2022/02/15
- Re: [PULL 0/4] Python patches, John Snow, 2022/02/15