From 49a608b8c22db72d47e7676ff9c3b87d1d408736 Mon Sep 17 00:00:00 2001 From: John Snow Date: Tue, 26 Oct 2021 13:56:06 -0400 Subject: [PATCH] python/machine: Handle QMP errors on close more meticulously 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 Reviewed-by: Hanna Reitz Reviewed-by: Kevin Wolf Message-id: 20211026175612.4127598-3-jsnow@redhat.com Signed-off-by: John Snow --- 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 0bd40bc2f76e..a0cf69786b4b 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._user_killed or 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)