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