python/qemu/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 logging
  15
  16
  17 class QMPError(Exception):
  18     pass
  19
  20
  21 class QMPConnectError(QMPError):
  22     pass
  23
  24
  25 class QMPCapabilitiesError(QMPError):
  26     pass
  27
  28
  29 class QMPTimeoutError(QMPError):
  30     pass
  31
  32
  33 class QEMUMonitorProtocol(object):
  34
  35     #: Logger object for debugging messages
  36     logger = logging.getLogger('QMP')
  37     #: Socket's error class
  38     error = socket.error
  39     #: Socket's timeout
  40     timeout = socket.timeout
  41
  42     def __init__(self, address, server=False):
  43         """
  44         Create a QEMUMonitorProtocol class.
  45
  46         @param address: QEMU address, can be either a unix socket path (string)
  47                         or a tuple in the form ( address, port ) for a TCP
  48                         connection
  49         @param server: server mode listens on the socket (bool)
  50         @raise socket.error on socket connection errors
  51         @note No connection is established, this is done by the connect() or
  52               accept() methods
  53         """
  54         self.__events = []
  55         self.__address = address
  56         self.__sock = self.__get_sock()
  57         self.__sockfile = None
  58         if server:
  59             self.__sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
  60             self.__sock.bind(self.__address)
  61             self.__sock.listen(1)
  62
  63     def __get_sock(self):
  64         if isinstance(self.__address, tuple):
  65             family = socket.AF_INET
  66         else:
  67             family = socket.AF_UNIX
  68         return socket.socket(family, socket.SOCK_STREAM)
  69
  70     def __negotiate_capabilities(self):
  71         greeting = self.__json_read()
  72         if greeting is None or "QMP" not in greeting:
  73             raise QMPConnectError
  74         # Greeting seems ok, negotiate capabilities
  75         resp = self.cmd('qmp_capabilities')
  76         if "return" in resp:
  77             return greeting
  78         raise QMPCapabilitiesError
  79
  80     def __json_read(self, only_event=False):
  81         while True:
  82             data = self.__sockfile.readline()
  83             if not data:
  84                 return
  85             resp = json.loads(data)
  86             if 'event' in resp:
  87                 self.logger.debug("<<< %s", resp)
  88                 self.__events.append(resp)
  89                 if not only_event:
  90                     continue
  91             return resp
  92
  93     def __get_events(self, wait=False):
  94         """
  95         Check for new events in the stream and cache them in __events.
  96
  97         @param wait (bool): block until an event is available.
  98         @param wait (float): If wait is a float, treat it as a timeout value.
  99
 100         @raise QMPTimeoutError: If a timeout float is provided and the timeout
 101                                 period elapses.
 102         @raise QMPConnectError: If wait is True but no events could be
 103                                 retrieved or if some other error occurred.
 104         """
 105
 106         # Check for new events regardless and pull them into the cache:
 107         self.__sock.setblocking(0)
 108         try:
 109             self.__json_read()
 110         except socket.error as err:
 111             if err[0] == errno.EAGAIN:
 112                 # No data available
 113                 pass
 114         self.__sock.setblocking(1)
 115
 116         # Wait for new events, if needed.
 117         # if wait is 0.0, this means "no wait" and is also implicitly false.
 118         if not self.__events and wait:
 119             if isinstance(wait, float):
 120                 self.__sock.settimeout(wait)
 121             try:
 122                 ret = self.__json_read(only_event=True)
 123             except socket.timeout:
 124                 raise QMPTimeoutError("Timeout waiting for event")
 125             except:
 126                 raise QMPConnectError("Error while reading from socket")
 127             if ret is None:
 128                 raise QMPConnectError("Error while reading from socket")
 129             self.__sock.settimeout(None)
 130
 131     def connect(self, negotiate=True):
 132         """
 133         Connect to the QMP Monitor and perform capabilities negotiation.
 134
 135         @return QMP greeting dict
 136         @raise socket.error on socket connection errors
 137         @raise QMPConnectError if the greeting is not received
 138         @raise QMPCapabilitiesError if fails to negotiate capabilities
 139         """
 140         self.__sock.connect(self.__address)
 141         self.__sockfile = self.__sock.makefile()
 142         if negotiate:
 143             return self.__negotiate_capabilities()
 144
 145     def accept(self):
 146         """
 147         Await connection from QMP Monitor and perform capabilities negotiation.
 148
 149         @return QMP greeting dict
 150         @raise socket.error on socket connection errors
 151         @raise QMPConnectError if the greeting is not received
 152         @raise QMPCapabilitiesError if fails to negotiate capabilities
 153         """
 154         self.__sock.settimeout(15)
 155         self.__sock, _ = self.__sock.accept()
 156         self.__sockfile = self.__sock.makefile()
 157         return self.__negotiate_capabilities()
 158
 159     def cmd_obj(self, qmp_cmd):
 160         """
 161         Send a QMP command to the QMP Monitor.
 162
 163         @param qmp_cmd: QMP command to be sent as a Python dict
 164         @return QMP response as a Python dict or None if the connection has
 165                 been closed
 166         """
 167         self.logger.debug(">>> %s", qmp_cmd)
 168         try:
 169             self.__sock.sendall(json.dumps(qmp_cmd).encode('utf-8'))
 170         except socket.error as err:
 171             if err[0] == errno.EPIPE:
 172                 return
 173             raise socket.error(err)
 174         resp = self.__json_read()
 175         self.logger.debug("<<< %s", resp)
 176         return resp
 177
 178     def cmd(self, name, args=None, cmd_id=None):
 179         """
 180         Build a QMP command and send it to the QMP Monitor.
 181
 182         @param name: command name (string)
 183         @param args: command arguments (dict)
 184         @param cmd_id: command id (dict, list, string or int)
 185         """
 186         qmp_cmd = {'execute': name}
 187         if args:
 188             qmp_cmd['arguments'] = args
 189         if cmd_id:
 190             qmp_cmd['id'] = cmd_id
 191         return self.cmd_obj(qmp_cmd)
 192
 193     def command(self, cmd, **kwds):
 194         """
 195         Build and send a QMP command to the monitor, report errors if any
 196         """
 197         ret = self.cmd(cmd, kwds)
 198         if "error" in ret:
 199             raise Exception(ret['error']['desc'])
 200         return ret['return']
 201
 202     def pull_event(self, wait=False):
 203         """
 204         Pulls a single event.
 205
 206         @param wait (bool): block until an event is available.
 207         @param wait (float): If wait is a float, treat it as a timeout value.
 208
 209         @raise QMPTimeoutError: If a timeout float is provided and the timeout
 210                                 period elapses.
 211         @raise QMPConnectError: If wait is True but no events could be
 212                                 retrieved or if some other error occurred.
 213
 214         @return The first available QMP event, or None.
 215         """
 216         self.__get_events(wait)
 217
 218         if self.__events:
 219             return self.__events.pop(0)
 220         return None
 221
 222     def get_events(self, wait=False):
 223         """
 224         Get a list of available QMP events.
 225
 226         @param wait (bool): block until an event is available.
 227         @param wait (float): If wait is a float, treat it as a timeout value.
 228
 229         @raise QMPTimeoutError: If a timeout float is provided and the timeout
 230                                 period elapses.
 231         @raise QMPConnectError: If wait is True but no events could be
 232                                 retrieved or if some other error occurred.
 233
 234         @return The list of available QMP events.
 235         """
 236         self.__get_events(wait)
 237         return self.__events
 238
 239     def clear_events(self):
 240         """
 241         Clear current list of pending events.
 242         """
 243         self.__events = []
 244
 245     def close(self):
 246         self.__sock.close()
 247         self.__sockfile.close()
 248
 249     def settimeout(self, timeout):
 250         self.__sock.settimeout(timeout)
 251
 252     def get_sock_fd(self):
 253         return self.__sock.fileno()
 254
 255     def is_scm_available(self):
 256         return self.__sock.family == socket.AF_UNIX