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Tue, 6 Oct 2020 23:59:10 +0000 (UTC) Received: from scv.redhat.com (ovpn-120-38.rdu2.redhat.com [10.10.120.38]) by smtp.corp.redhat.com (Postfix) with ESMTP id 9189E60BFA; Tue, 6 Oct 2020 23:59:09 +0000 (UTC) From: John Snow To: qemu-devel@nongnu.org Subject: [PATCH 19/20] python/qemu/qmp.py: Straighten out exception hierarchy Date: Tue, 6 Oct 2020 19:58:16 -0400 Message-Id: <20201006235817.3280413-20-jsnow@redhat.com> In-Reply-To: <20201006235817.3280413-1-jsnow@redhat.com> References: <20201006235817.3280413-1-jsnow@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=jsnow@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Received-SPF: pass client-ip=216.205.24.124; envelope-from=jsnow@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/10/06 00:55:20 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -27 X-Spam_score: -2.8 X-Spam_bar: -- X-Spam_report: (-2.8 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.733, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=unavailable autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Kevin Wolf , Eduardo Habkost , qemu-block@nongnu.org, Max Reitz , Cleber Rosa , John Snow Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" 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 Reviewed-by: Kevin Wolf --- 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'])