scripts/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 import sys
  15
  16 class QMPError(Exception):
  17     pass
  18
  19 class QMPConnectError(QMPError):
  20     pass
  21
  22 class QMPCapabilitiesError(QMPError):
  23     pass
  24
  25 class QMPTimeoutError(QMPError):
  26     pass
  27
  28 class QEMUMonitorProtocol:
  29     def __init__(self, address, server=False, debug=False):
  30         """
  31         Create a QEMUMonitorProtocol class.
  32
  33         @param address: QEMU address, can be either a unix socket path (string)
  34                         or a tuple in the form ( address, port ) for a TCP
  35                         connection
  36         @param server: server mode listens on the socket (bool)
  37         @raise socket.error on socket connection errors
  38         @note No connection is established, this is done by the connect() or
  39               accept() methods
  40         """
  41         self.__events = []
  42         self.__address = address
  43         self._debug = debug
  44         self.__sock = self.__get_sock()
  45         if server:
  46             self.__sock.bind(self.__address)
  47             self.__sock.listen(1)
  48
  49     def __get_sock(self):
  50         if isinstance(self.__address, tuple):
  51             family = socket.AF_INET
  52         else:
  53             family = socket.AF_UNIX
  54         return socket.socket(family, socket.SOCK_STREAM)
  55
  56     def __negotiate_capabilities(self):
  57         greeting = self.__json_read()
  58         if greeting is None or not greeting.has_key('QMP'):
  59             raise QMPConnectError
  60         # Greeting seems ok, negotiate capabilities
  61         resp = self.cmd('qmp_capabilities')
  62         if "return" in resp:
  63             return greeting
  64         raise QMPCapabilitiesError
  65
  66     def __json_read(self, only_event=False):
  67         while True:
  68             data = self.__sockfile.readline()
  69             if not data:
  70                 return
  71             resp = json.loads(data)
  72             if 'event' in resp:
  73                 if self._debug:
  74                     print >>sys.stderr, "QMP:<<< %s" % resp
  75                 self.__events.append(resp)
  76                 if not only_event:
  77                     continue
  78             return resp
  79
  80     error = socket.error
  81
  82     def __get_events(self, wait=False):
  83         """
  84         Check for new events in the stream and cache them in __events.
  85
  86         @param wait (bool): block until an event is available.
  87         @param wait (float): If wait is a float, treat it as a timeout value.
  88
  89         @raise QMPTimeoutError: If a timeout float is provided and the timeout
  90                                 period elapses.
  91         @raise QMPConnectError: If wait is True but no events could be retrieved
  92                                 or if some other error occurred.
  93         """
  94
  95         # Check for new events regardless and pull them into the cache:
  96         self.__sock.setblocking(0)
  97         try:
  98             self.__json_read()
  99         except socket.error as err:
 100             if err[0] == errno.EAGAIN:
 101                 # No data available
 102                 pass
 103         self.__sock.setblocking(1)
 104
 105         # Wait for new events, if needed.
 106         # if wait is 0.0, this means "no wait" and is also implicitly false.
 107         if not self.__events and wait:
 108             if isinstance(wait, float):
 109                 self.__sock.settimeout(wait)
 110             try:
 111                 ret = self.__json_read(only_event=True)
 112             except socket.timeout:
 113                 raise QMPTimeoutError("Timeout waiting for event")
 114             except:
 115                 raise QMPConnectError("Error while reading from socket")
 116             if ret is None:
 117                 raise QMPConnectError("Error while reading from socket")
 118             self.__sock.settimeout(None)
 119
 120     def connect(self, negotiate=True):
 121         """
 122         Connect to the QMP Monitor and perform capabilities negotiation.
 123
 124         @return QMP greeting dict
 125         @raise socket.error on socket connection errors
 126         @raise QMPConnectError if the greeting is not received
 127         @raise QMPCapabilitiesError if fails to negotiate capabilities
 128         """
 129         self.__sock.connect(self.__address)
 130         self.__sockfile = self.__sock.makefile()
 131         if negotiate:
 132             return self.__negotiate_capabilities()
 133
 134     def accept(self):
 135         """
 136         Await connection from QMP Monitor and perform capabilities negotiation.
 137
 138         @return QMP greeting dict
 139         @raise socket.error on socket connection errors
 140         @raise QMPConnectError if the greeting is not received
 141         @raise QMPCapabilitiesError if fails to negotiate capabilities
 142         """
 143         self.__sock, _ = self.__sock.accept()
 144         self.__sockfile = self.__sock.makefile()
 145         return self.__negotiate_capabilities()
 146
 147     def cmd_obj(self, qmp_cmd):
 148         """
 149         Send a QMP command to the QMP Monitor.
 150
 151         @param qmp_cmd: QMP command to be sent as a Python dict
 152         @return QMP response as a Python dict or None if the connection has
 153                 been closed
 154         """
 155         if self._debug:
 156             print >>sys.stderr, "QMP:>>> %s" % qmp_cmd
 157         try:
 158             self.__sock.sendall(json.dumps(qmp_cmd))
 159         except socket.error as err:
 160             if err[0] == errno.EPIPE:
 161                 return
 162             raise socket.error(err)
 163         resp = self.__json_read()
 164         if self._debug:
 165             print >>sys.stderr, "QMP:<<< %s" % resp
 166         return resp
 167
 168     def cmd(self, name, args=None, id=None):
 169         """
 170         Build a QMP command and send it to the QMP Monitor.
 171
 172         @param name: command name (string)
 173         @param args: command arguments (dict)
 174         @param id: command id (dict, list, string or int)
 175         """
 176         qmp_cmd = { 'execute': name }
 177         if args:
 178             qmp_cmd['arguments'] = args
 179         if id:
 180             qmp_cmd['id'] = id
 181         return self.cmd_obj(qmp_cmd)
 182
 183     def command(self, cmd, **kwds):
 184         ret = self.cmd(cmd, kwds)
 185         if ret.has_key('error'):
 186             raise Exception(ret['error']['desc'])
 187         return ret['return']
 188
 189     def pull_event(self, wait=False):
 190         """
 191         Get and delete the first available QMP event.
 192
 193         @param wait (bool): block until an event is available.
 194         @param wait (float): If wait is a float, treat it as a timeout value.
 195
 196         @raise QMPTimeoutError: If a timeout float is provided and the timeout
 197                                 period elapses.
 198         @raise QMPConnectError: If wait is True but no events could be retrieved
 199                                 or if some other error occurred.
 200
 201         @return The first available QMP event, or None.
 202         """
 203         self.__get_events(wait)
 204
 205         if self.__events:
 206             return self.__events.pop(0)
 207         return None
 208
 209     def get_events(self, wait=False):
 210         """
 211         Get a list of available QMP events.
 212
 213         @param wait (bool): block until an event is available.
 214         @param wait (float): If wait is a float, treat it as a timeout value.
 215
 216         @raise QMPTimeoutError: If a timeout float is provided and the timeout
 217                                 period elapses.
 218         @raise QMPConnectError: If wait is True but no events could be retrieved
 219                                 or if some other error occurred.
 220
 221         @return The list of available QMP events.
 222         """
 223         self.__get_events(wait)
 224         return self.__events
 225
 226     def clear_events(self):
 227         """
 228         Clear current list of pending events.
 229         """
 230         self.__events = []
 231
 232     def close(self):
 233         self.__sock.close()
 234         self.__sockfile.close()
 235
 236     timeout = socket.timeout
 237
 238     def settimeout(self, timeout):
 239         self.__sock.settimeout(timeout)
 240
 241     def get_sock_fd(self):
 242         return self.__sock.fileno()
 243
 244     def is_scm_available(self):
 245         return self.__sock.family == socket.AF_UNIX