qemu/QMP/qmp.py
Luiz Capitulino 1d00a07de9 QMP: Revamp the Python class example
This commit simplifies and fixes a number of problems in the Python
QEMUMonitorProtocol example class.

It's almost a rewrite and it DOES BREAK the qmp-shell script (which
is going to be fixed in the next commit).

However, I'm not going to split this in different commits because it
could get up to 10 commits, it's really not worth it for a simple
demo class.

Highlights:

 o TCP sockets support
 o QMP events support
 o Add documentation
 o Fix a number of unhandled errors
 o Simplify methods that send commands to the Monitor

Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>
2010-11-17 09:51:07 -02:00

132 lines
3.7 KiB
Python

# QEMU Monitor Protocol Python class
#
# Copyright (C) 2009, 2010 Red Hat Inc.
#
# Authors:
# Luiz Capitulino <lcapitulino@redhat.com>
#
# This work is licensed under the terms of the GNU GPL, version 2. See
# the COPYING file in the top-level directory.
import json
import errno
import socket
class QMPError(Exception):
pass
class QMPConnectError(QMPError):
pass
class QMPCapabilitiesError(QMPError):
pass
class QEMUMonitorProtocol:
def __init__(self, address):
"""
Create a QEMUMonitorProtocol class.
@param address: QEMU address, can be either a unix socket path (string)
or a tuple in the form ( address, port ) for a TCP
connection
@note No connection is established, this is done by the connect() method
"""
self.__events = []
self.__address = address
self.__sock = self.__get_sock()
self.__sockfile = self.__sock.makefile()
def __get_sock(self):
if isinstance(self.__address, tuple):
family = socket.AF_INET
else:
family = socket.AF_UNIX
return socket.socket(family, socket.SOCK_STREAM)
def __json_read(self):
while True:
data = self.__sockfile.readline()
if not data:
return
resp = json.loads(data)
if 'event' in resp:
self.__events.append(resp)
continue
return resp
error = socket.error
def connect(self):
"""
Connect to the QMP Monitor and perform capabilities negotiation.
@return QMP greeting dict
@raise socket.error on socket connection errors
@raise QMPConnectError if the greeting is not received
@raise QMPCapabilitiesError if fails to negotiate capabilities
"""
self.__sock.connect(self.__address)
greeting = self.__json_read()
if greeting is None or not greeting.has_key('QMP'):
raise QMPConnectError
# Greeting seems ok, negotiate capabilities
resp = self.cmd('qmp_capabilities')
if "return" in resp:
return greeting
raise QMPCapabilitiesError
def cmd_obj(self, qmp_cmd):
"""
Send a QMP command to the QMP Monitor.
@param qmp_cmd: QMP command to be sent as a Python dict
@return QMP response as a Python dict or None if the connection has
been closed
"""
try:
self.__sock.sendall(json.dumps(qmp_cmd))
except socket.error, err:
if err[0] == errno.EPIPE:
return
raise socket.error(err)
return self.__json_read()
def cmd(self, name, args=None, id=None):
"""
Build a QMP command and send it to the QMP Monitor.
@param name: command name (string)
@param args: command arguments (dict)
@param id: command id (dict, list, string or int)
"""
qmp_cmd = { 'execute': name }
if args:
qmp_cmd['arguments'] = args
if id:
qmp_cmd['id'] = id
return self.cmd_obj(qmp_cmd)
def get_events(self):
"""
Get a list of available QMP events.
"""
self.__sock.setblocking(0)
try:
self.__json_read()
except socket.error, err:
if err[0] == errno.EAGAIN:
# No data available
pass
self.__sock.setblocking(1)
return self.__events
def clear_events(self):
"""
Clear current list of pending events.
"""
self.__events = []
def close(self):
self.__sock.close()
self.__sockfile.close()