QMP/qmp.py

   1 # QEMU Monitor Protocol Python class
   2 #
   3 # Copyright (C) 2009, 2010 Red Hat Inc.
   4 #
   5 # Authors:
   6 #  Luiz Capitulino <lcapitulino@redhat.com>
   7 #
   8 # This work is licensed under the terms of the GNU GPL, version 2.  See
   9 # the COPYING file in the top-level directory.
  10
  11 import json
  12 import errno
  13 import socket
  14
  15 class QMPError(Exception):
  16     pass
  17
  18 class QMPConnectError(QMPError):
  19     pass
  20
  21 class QMPCapabilitiesError(QMPError):
  22     pass
  23
  24 class QEMUMonitorProtocol:
  25     def __init__(self, address, server=False):
  26         """
  27         Create a QEMUMonitorProtocol class.
  28
  29         @param address: QEMU address, can be either a unix socket path (string)
  30                         or a tuple in the form ( address, port ) for a TCP
  31                         connection
  32         @param server: server mode listens on the socket (bool)
  33         @raise socket.error on socket connection errors
  34         @note No connection is established, this is done by the connect() or
  35               accept() methods
  36         """
  37         self.__events = []
  38         self.__address = address
  39         self.__sock = self.__get_sock()
  40         if server:
  41             self.__sock.bind(self.__address)
  42             self.__sock.listen(1)
  43
  44     def __get_sock(self):
  45         if isinstance(self.__address, tuple):
  46             family = socket.AF_INET
  47         else:
  48             family = socket.AF_UNIX
  49         return socket.socket(family, socket.SOCK_STREAM)
  50
  51     def __negotiate_capabilities(self):
  52         self.__sockfile = self.__sock.makefile()
  53         greeting = self.__json_read()
  54         if greeting is None or not greeting.has_key('QMP'):
  55             raise QMPConnectError
  56         # Greeting seems ok, negotiate capabilities
  57         resp = self.cmd('qmp_capabilities')
  58         if "return" in resp:
  59             return greeting
  60         raise QMPCapabilitiesError
  61
  62     def __json_read(self, only_event=False):
  63         while True:
  64             data = self.__sockfile.readline()
  65             if not data:
  66                 return
  67             resp = json.loads(data)
  68             if 'event' in resp:
  69                 self.__events.append(resp)
  70                 if not only_event:
  71                     continue
  72             return resp
  73
  74     error = socket.error
  75
  76     def connect(self):
  77         """
  78         Connect to the QMP Monitor and perform capabilities negotiation.
  79
  80         @return QMP greeting dict
  81         @raise socket.error on socket connection errors
  82         @raise QMPConnectError if the greeting is not received
  83         @raise QMPCapabilitiesError if fails to negotiate capabilities
  84         """
  85         self.__sock.connect(self.__address)
  86         return self.__negotiate_capabilities()
  87
  88     def accept(self):
  89         """
  90         Await connection from QMP Monitor and perform capabilities negotiation.
  91
  92         @return QMP greeting dict
  93         @raise socket.error on socket connection errors
  94         @raise QMPConnectError if the greeting is not received
  95         @raise QMPCapabilitiesError if fails to negotiate capabilities
  96         """
  97         self.__sock, _ = self.__sock.accept()
  98         return self.__negotiate_capabilities()
  99
 100     def cmd_obj(self, qmp_cmd):
 101         """
 102         Send a QMP command to the QMP Monitor.
 103
 104         @param qmp_cmd: QMP command to be sent as a Python dict
 105         @return QMP response as a Python dict or None if the connection has
 106                 been closed
 107         """
 108         try:
 109             self.__sock.sendall(json.dumps(qmp_cmd))
 110         except socket.error, err:
 111             if err[0] == errno.EPIPE:
 112                 return
 113             raise socket.error(err)
 114         return self.__json_read()
 115
 116     def cmd(self, name, args=None, id=None):
 117         """
 118         Build a QMP command and send it to the QMP Monitor.
 119
 120         @param name: command name (string)
 121         @param args: command arguments (dict)
 122         @param id: command id (dict, list, string or int)
 123         """
 124         qmp_cmd = { 'execute': name }
 125         if args:
 126             qmp_cmd['arguments'] = args
 127         if id:
 128             qmp_cmd['id'] = id
 129         return self.cmd_obj(qmp_cmd)
 130
 131     def command(self, cmd, **kwds):
 132         ret = self.cmd(cmd, kwds)
 133         if ret.has_key('error'):
 134             raise Exception(ret['error']['desc'])
 135         return ret['return']
 136
 137     def get_events(self, wait=False):
 138         """
 139         Get a list of available QMP events.
 140
 141         @param wait: block until an event is available (bool)
 142         """
 143         self.__sock.setblocking(0)
 144         try:
 145             self.__json_read()
 146         except socket.error, err:
 147             if err[0] == errno.EAGAIN:
 148                 # No data available
 149                 pass
 150         self.__sock.setblocking(1)
 151         if not self.__events and wait:
 152             self.__json_read(only_event=True)
 153         return self.__events
 154
 155     def clear_events(self):
 156         """
 157         Clear current list of pending events.
 158         """
 159         self.__events = []
 160
 161     def close(self):
 162         self.__sock.close()
 163         self.__sockfile.close()