Be a little more rigorous about which exception we use, and when.
Primarily, this makes QMPCapabilitiesError an extension of
QMPprotocolError.
The family of errors:
QMPError (generic base)
QMPConnectError (For connection issues)
QMPTimeoutError (when waiting for an event expires)
QMPProtocolError (unexpected/garbled responses)
QMPCapabilitiesError (handshake problems)
QMPResponseError (For in-band QMP error returns)
Signed-off-by: John Snow <js...@redhat.com>
---
python/qemu/qmp.py | 45 ++++++++++++++++++++++++++++++---------------
1 file changed, 30 insertions(+), 15 deletions(-)
diff --git a/python/qemu/qmp.py b/python/qemu/qmp.py
index bdbd1e9bdbb..1349632c101 100644
--- a/python/qemu/qmp.py
+++ b/python/qemu/qmp.py
@@ -41,7 +41,7 @@
class QMPError(Exception):
"""
- QMP base exception
+ QMP base exception; all QMP errors derive from this.
"""
@@ -51,7 +51,13 @@ class QMPConnectError(QMPError):
"""
-class QMPCapabilitiesError(QMPError):
+class QMPProtocolError(QMPError):
+ """
+ QMP protocol error; unexpected response
+ """
+
+
+class QMPCapabilitiesError(QMPProtocolError):
"""
QMP negotiate capabilities exception
"""
@@ -63,15 +69,9 @@ class QMPTimeoutError(QMPError):
"""
-class QMPProtocolError(QMPError):
- """
- QMP protocol error; unexpected response
- """
-
-
class QMPResponseError(QMPError):
"""
- Represents erroneous QMP monitor reply
+ Represents in-band QMP replies indicating command failure
"""
def __init__(self, reply: QMPMessage):
try:
@@ -125,14 +125,23 @@ def __get_sock(self) -> socket.socket:
return socket.socket(family, socket.SOCK_STREAM)
def __negotiate_capabilities(self) -> QMPMessage:
+ """
+ @raise QMPConnectError on failure to receive the greeting.
+ @raise QMPCapabilitiesError on malformed greeting, or malformed
+ capabilities handshake response.
+ """
greeting = self.__json_read()
- if greeting is None or "QMP" not in greeting:
- raise QMPConnectError
+ if greeting is None:
+ raise QMPConnectError("Did not receive QMP greeting")
+ if 'QMP' not in greeting:
+ msg = f"Did not understand greeting: '{str(greeting)}'"
+ raise QMPCapabilitiesError(msg)
# Greeting seems ok, negotiate capabilities
resp = self.cmd('qmp_capabilities')
if resp and "return" in resp:
return greeting
- raise QMPCapabilitiesError
+ msg = "Did not understand capabilities reply"
+ raise QMPCapabilitiesError(f"{msg}: {str(resp)}")
def __json_read(self, only_event: bool = False) -> Optional[QMPMessage]:
assert self.__sockfile is not None
@@ -158,10 +167,12 @@ def __get_events(self, wait: Union[bool, float] = False)
-> None:
@param wait (bool): block until an event is available.
@param wait (float): If wait is a float, treat it as a timeout value.
+ @raise OSError: For backing socket connection errors
@raise QMPTimeoutError: If a timeout float is provided and the timeout
period elapses.
@raise QMPConnectError: If wait is True but no events could be
retrieved or if some other error occurred.
+ @raise QMPProtocolError: If a garbled message is received.
"""
# Check for new events regardless and pull them into the cache:
@@ -187,7 +198,7 @@ def __get_events(self, wait: Union[bool, float] = False) ->
None:
msg = "Error while reading from socket"
raise QMPConnectError(msg) from err
if ret is None:
- raise QMPConnectError("Error while reading from socket")
+ raise QMPProtocolError("Unexpected empty message from server")
self.__sock.settimeout(None)
def __enter__(self) -> 'QEMUMonitorProtocol':
@@ -245,12 +256,13 @@ def cmd_obj(self, qmp_cmd: QMPMessage) -> QMPMessage:
@param qmp_cmd: QMP command to be sent as a Python dict
@return QMP response as a Python dict
+ @raise QMPProtocolError on unexpected empty messages.
"""
self.logger.debug(">>> %s", qmp_cmd)
self.__sock.sendall(json.dumps(qmp_cmd).encode('utf-8'))
resp = self.__json_read()
if resp is None:
- raise QMPConnectError("Unexpected empty reply from server")
+ raise QMPProtocolError("Unexpected empty reply from server")
self.logger.debug("<<< %s", resp)
return resp
@@ -274,13 +286,16 @@ def cmd(self, name: str,
def command(self, cmd: str, **kwds: Any) -> QMPReturnValue:
"""
Build and send a QMP command to the monitor, report errors if any
+
+ @raise QMPResponseError if the server returns an in-band error reply.
+ @raise QMPProtocolError if the server reply is not understood.
"""
ret = self.cmd(cmd, kwds)
if 'error' in ret:
raise QMPResponseError(ret)
if 'return' not in ret:
raise QMPProtocolError(
- "'return' key not found in QMP response '{}'".format(str(ret))
+ f"'return' key not found in QMP response '{str(ret)}'"
)
return cast(QMPReturnValue, ret['return'])
--
2.26.2
