diff options
| -rw-r--r-- | python/qemu/aqmp/protocol.py | 89 |
1 files changed, 62 insertions, 27 deletions
diff --git a/python/qemu/aqmp/protocol.py b/python/qemu/aqmp/protocol.py index 33358f5cd7..009883f64d 100644 --- a/python/qemu/aqmp/protocol.py +++ b/python/qemu/aqmp/protocol.py @@ -317,6 +317,62 @@ class AsyncProtocol(Generic[T]): # Section: Session machinery # -------------------------- + async def _session_guard(self, coro: Awaitable[None], emsg: str) -> None: + """ + Async guard function used to roll back to `IDLE` on any error. + + On any Exception, the state machine will be reset back to + `IDLE`. Most Exceptions will be wrapped with `ConnectError`, but + `BaseException` events will be left alone (This includes + asyncio.CancelledError, even prior to Python 3.8). + + :param error_message: + Human-readable string describing what connection phase failed. + + :raise BaseException: + When `BaseException` occurs in the guarded block. + :raise ConnectError: + When any other error is encountered in the guarded block. + """ + # Note: After Python 3.6 support is removed, this should be an + # @asynccontextmanager instead of accepting a callback. + try: + await coro + except BaseException as err: + self.logger.error("%s: %s", emsg, exception_summary(err)) + self.logger.debug("%s:\n%s\n", emsg, pretty_traceback()) + try: + # Reset the runstate back to IDLE. + await self.disconnect() + except: + # We don't expect any Exceptions from the disconnect function + # here, because we failed to connect in the first place. + # The disconnect() function is intended to perform + # only cannot-fail cleanup here, but you never know. + emsg = ( + "Unexpected bottom half exception. " + "This is a bug in the QMP library. " + "Please report it to <qemu-devel@nongnu.org> and " + "CC: John Snow <jsnow@redhat.com>." + ) + self.logger.critical("%s:\n%s\n", emsg, pretty_traceback()) + raise + + # CancelledError is an Exception with special semantic meaning; + # We do NOT want to wrap it up under ConnectError. + # NB: CancelledError is not a BaseException before Python 3.8 + if isinstance(err, asyncio.CancelledError): + raise + + # Any other kind of error can be treated as some kind of connection + # failure broadly. Inspect the 'exc' field to explore the root + # cause in greater detail. + if isinstance(err, Exception): + raise ConnectError(emsg, err) from err + + # Raise BaseExceptions un-wrapped, they're more important. + raise + @property def _runstate_event(self) -> asyncio.Event: # asyncio.Event() objects should not be created prior to entrance into @@ -371,34 +427,13 @@ class AsyncProtocol(Generic[T]): """ assert self.runstate == Runstate.IDLE - try: - phase = "connection" - await self._establish_connection(address, ssl, accept) - - phase = "session" - await self._establish_session() + await self._session_guard( + self._establish_connection(address, ssl, accept), + 'Failed to establish connection') - except BaseException as err: - emsg = f"Failed to establish {phase}" - self.logger.error("%s: %s", emsg, exception_summary(err)) - self.logger.debug("%s:\n%s\n", emsg, pretty_traceback()) - try: - # Reset from CONNECTING back to IDLE. - await self.disconnect() - except: - emsg = "Unexpected bottom half exception" - self.logger.critical("%s:\n%s\n", emsg, pretty_traceback()) - raise - - # NB: CancelledError is not a BaseException before Python 3.8 - if isinstance(err, asyncio.CancelledError): - raise - - if isinstance(err, Exception): - raise ConnectError(emsg, err) from err - - # Raise BaseExceptions un-wrapped, they're more important. - raise + await self._session_guard( + self._establish_session(), + 'Failed to establish session') assert self.runstate == Runstate.RUNNING |