On Wed, Sep 22, 2021 at 8:50 PM John Snow <jsnow@redhat.com> wrote:
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:
I strongly suspect that this line needs to actually be "if not
(self._user_killed or self._quit_issued):" to also handle the
force-kill cases.