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[PATCH v2 12/17] python/machine: Handle QMP errors on close more meticul
From: |
John Snow |
Subject: |
[PATCH v2 12/17] python/machine: Handle QMP errors on close more meticulously |
Date: |
Wed, 22 Sep 2021 20:49:33 -0400 |
To use the AQMP backend, Machine just needs to be a little more diligent
about what happens when closing a QMP connection. The operation is no
longer a freebie in the async world; it may return errors encountered in
the async bottom half on incoming message receipt, etc.
(AQMP's disconnect, ultimately, serves as the quiescence point where all
async contexts are gathered together, and any final errors reported at
that point.)
Because async QMP continues to check for messages asynchronously, it's
almost certainly likely that the loop will have exited due to EOF after
issuing the last 'quit' command. That error will ultimately be bubbled
up when attempting to close the QMP connection. The manager class here
then is free to discard it -- if it was expected.
Signed-off-by: John Snow <jsnow@redhat.com>
---
Yes, I regret that this class has become quite a dumping ground for
complexity around the exit path. It's in need of a refactor to help
separate out the exception handling and cleanup mechanisms from the
VM-related stuff, but it's not a priority to do that just yet -- but
it's on the list.
Signed-off-by: John Snow <jsnow@redhat.com>
---
python/qemu/machine/machine.py | 48 +++++++++++++++++++++++++++++-----
1 file changed, 42 insertions(+), 6 deletions(-)
diff --git a/python/qemu/machine/machine.py b/python/qemu/machine/machine.py
index 0bd40bc2f76..c33a78a2d9f 100644
--- a/python/qemu/machine/machine.py
+++ b/python/qemu/machine/machine.py
@@ -342,9 +342,15 @@ def _post_shutdown(self) -> None:
# Comprehensive reset for the failed launch case:
self._early_cleanup()
- if self._qmp_connection:
- self._qmp.close()
- self._qmp_connection = None
+ try:
+ self._close_qmp_connection()
+ except Exception as err: # pylint: disable=broad-except
+ LOG.warning(
+ "Exception closing QMP connection: %s",
+ str(err) if str(err) else type(err).__name__
+ )
+ finally:
+ assert self._qmp_connection is None
self._close_qemu_log_file()
@@ -420,6 +426,31 @@ def _launch(self) -> None:
close_fds=False)
self._post_launch()
+ def _close_qmp_connection(self) -> None:
+ """
+ Close the underlying QMP connection, if any.
+
+ Dutifully report errors that occurred while closing, but assume
+ that any error encountered indicates an abnormal termination
+ process and not a failure to close.
+ """
+ if self._qmp_connection is None:
+ return
+
+ try:
+ self._qmp.close()
+ except EOFError:
+ # EOF can occur as an Exception here when using the Async
+ # QMP backend. It indicates that the server closed the
+ # stream. If we successfully issued 'quit' at any point,
+ # then this was expected. If the remote went away without
+ # our permission, it's worth reporting that as an abnormal
+ # shutdown case.
+ if not self._quit_issued:
+ raise
+ finally:
+ self._qmp_connection = None
+
def _early_cleanup(self) -> None:
"""
Perform any cleanup that needs to happen before the VM exits.
@@ -460,9 +491,14 @@ def _soft_shutdown(self, timeout: Optional[int]) -> None:
self._early_cleanup()
if self._qmp_connection:
- if not self._quit_issued:
- # Might raise ConnectionReset
- self.qmp('quit')
+ try:
+ if not self._quit_issued:
+ # May raise ExecInterruptedError or StateError if the
+ # connection dies or has *already* died.
+ self.qmp('quit')
+ finally:
+ # Regardless, we want to quiesce the connection.
+ self._close_qmp_connection()
# May raise subprocess.TimeoutExpired
self._subp.wait(timeout=timeout)
--
2.31.1
- [PATCH v2 03/17] python/aqmp: Return cleared events from EventListener.clear(), (continued)
- [PATCH v2 03/17] python/aqmp: Return cleared events from EventListener.clear(), John Snow, 2021/09/22
- [PATCH v2 02/17] python/aqmp: add .empty() method to EventListener, John Snow, 2021/09/22
- [PATCH v2 04/17] python/aqmp: add send_fd_scm, John Snow, 2021/09/22
- [PATCH v2 05/17] python/aqmp: Add dict conversion method to Greeting object, John Snow, 2021/09/22
- [PATCH v2 07/17] python/aqmp: Disable logging messages by default, John Snow, 2021/09/22
- [PATCH v2 06/17] python/aqmp: Reduce severity of EOFError-caused loop terminations, John Snow, 2021/09/22
- [PATCH v2 08/17] python/qmp: clear events on get_events() call, John Snow, 2021/09/22
- [PATCH v2 09/17] python/qmp: add send_fd_scm directly to QEMUMonitorProtocol, John Snow, 2021/09/22
- [PATCH v2 10/17] python, iotests: remove socket_scm_helper, John Snow, 2021/09/22
- [PATCH v2 11/17] python/machine: remove has_quit argument, John Snow, 2021/09/22
- [PATCH v2 12/17] python/machine: Handle QMP errors on close more meticulously,
John Snow <=
- [PATCH v2 15/17] python/aqmp: Create sync QMP wrapper for iotests, John Snow, 2021/09/22
- [PATCH v2 16/17] python/aqmp: Remove scary message, John Snow, 2021/09/22
- [PATCH v2 13/17] iotests: Accommodate async QMP Exception classes, John Snow, 2021/09/22
- [PATCH v2 14/17] iotests: Conditionally silence certain AQMP errors, John Snow, 2021/09/22
- [PATCH v2 17/17] python, iotests: replace qmp with aqmp, John Snow, 2021/09/22