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# 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
import logging
class QMPError(Exception):
pass
class QMPConnectError(QMPError):
pass
class QMPCapabilitiesError(QMPError):
pass
class QMPTimeoutError(QMPError):
pass
class QEMUMonitorProtocol(object):
#: Logger object for debugging messages
logger = logging.getLogger('QMP')
#: Socket's error class
error = socket.error
#: Socket's timeout
timeout = socket.timeout
def __init__(self, address, server=False):
"""
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
@param server: server mode listens on the socket (bool)
@raise socket.error on socket connection errors
@note No connection is established, this is done by the connect() or
accept() methods
"""
self.__events = []
self.__address = address
self.__sock = self.__get_sock()
self.__sockfile = None
if server:
self.__sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
self.__sock.bind(self.__address)
self.__sock.listen(1)
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 __negotiate_capabilities(self):
greeting = self.__json_read()
if greeting is None or "QMP" not in greeting:
raise QMPConnectError
# Greeting seems ok, negotiate capabilities
resp = self.cmd('qmp_capabilities')
if "return" in resp:
return greeting
raise QMPCapabilitiesError
def __json_read(self, only_event=False):
while True:
data = self.__sockfile.readline()
if not data:
return
resp = json.loads(data)
if 'event' in resp:
self.logger.debug("<<< %s", resp)
self.__events.append(resp)
if not only_event:
continue
return resp
def __get_events(self, wait=False):
"""
Check for new events in the stream and cache them in __events.
@param wait (bool): block until an event is available.
@param wait (float): If wait is a float, treat it as a timeout value.
@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.
"""
# Check for new events regardless and pull them into the cache:
self.__sock.setblocking(0)
try:
self.__json_read()
except socket.error as err:
if err[0] == errno.EAGAIN:
# No data available
pass
self.__sock.setblocking(1)
# Wait for new events, if needed.
# if wait is 0.0, this means "no wait" and is also implicitly false.
if not self.__events and wait:
if isinstance(wait, float):
self.__sock.settimeout(wait)
try:
ret = self.__json_read(only_event=True)
except socket.timeout:
raise QMPTimeoutError("Timeout waiting for event")
except:
raise QMPConnectError("Error while reading from socket")
if ret is None:
raise QMPConnectError("Error while reading from socket")
self.__sock.settimeout(None)
def connect(self, negotiate=True):
"""
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)
self.__sockfile = self.__sock.makefile()
if negotiate:
return self.__negotiate_capabilities()
def accept(self):
"""
Await connection from 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.settimeout(15)
self.__sock, _ = self.__sock.accept()
self.__sockfile = self.__sock.makefile()
return self.__negotiate_capabilities()
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
"""
self.logger.debug(">>> %s", qmp_cmd)
try:
self.__sock.sendall(json.dumps(qmp_cmd))
except socket.error as err:
if err[0] == errno.EPIPE:
return
raise socket.error(err)
resp = self.__json_read()
self.logger.debug("<<< %s", resp)
return resp
def cmd(self, name, args=None, cmd_id=None):
"""
Build a QMP command and send it to the QMP Monitor.
@param name: command name (string)
@param args: command arguments (dict)
@param cmd_id: command id (dict, list, string or int)
"""
qmp_cmd = {'execute': name}
if args:
qmp_cmd['arguments'] = args
if cmd_id:
qmp_cmd['id'] = cmd_id
return self.cmd_obj(qmp_cmd)
def command(self, cmd, **kwds):
"""
Build and send a QMP command to the monitor, report errors if any
"""
ret = self.cmd(cmd, kwds)
if "error" in ret:
raise Exception(ret['error']['desc'])
return ret['return']
def pull_event(self, wait=False):
"""
Pulls a single event.
@param wait (bool): block until an event is available.
@param wait (float): If wait is a float, treat it as a timeout value.
@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.
@return The first available QMP event, or None.
"""
self.__get_events(wait)
if self.__events:
return self.__events.pop(0)
return None
def get_events(self, wait=False):
"""
Get a list of available QMP events.
@param wait (bool): block until an event is available.
@param wait (float): If wait is a float, treat it as a timeout value.
@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.
@return The list of available QMP events.
"""
self.__get_events(wait)
return self.__events
def clear_events(self):
"""
Clear current list of pending events.
"""
self.__events = []
def close(self):
self.__sock.close()
self.__sockfile.close()
def settimeout(self, timeout):
self.__sock.settimeout(timeout)
def get_sock_fd(self):
return self.__sock.fileno()
def is_scm_available(self):
return self.__sock.family == socket.AF_UNIX
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