Add QEMU QMP wrapper.

setup.py

@@ -70,6 +70,7 @@ setup(name=name,
           'onetimeupload = slapos.onetimeupload:main',
           'pubsubnotifier = slapos.pubsub.notifier:main',
           'pubsubserver = slapos.pubsub:main',
+          'qemu-qmp-client = slapos.qemuqmpclient:main',
           'shacache = slapos.shacache:main',
           'slapbuilder = slapos.builder:main',
           'slapcontainer = slapos.container:main',

slapos/qemuqmpclient/__init__.py

+##############################################################################
+#
+# Copyright (c) 2013 Vifib SARL and Contributors. All Rights Reserved.
+#
+# WARNING: This program as such is intended to be used by professional
+# programmers who take the whole responsibility of assessing all potential
+# consequences resulting from its eventual inadequacies and bugs
+# End users who are looking for a ready-to-use solution with commercial
+# guarantees and support are strongly adviced to contract a Free Software
+# Service Company
+#
+# This program is Free Software; you can redistribute it and/or
+# modify it under the terms of the GNU General Public License
+# as published by the Free Software Foundation; either version 3
+# of the License, or (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program; if not, write to the Free Software
+# Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
+#
+##############################################################################
+
+import argparse
+import json
+import os
+import socket
+import time
+
+QMP_STOP_ACTION = 'suspend'
+QMP_RESUME_ACTION = 'resume'
+QMP_CAPABILITIES_ACTION = 'capabilities'
+
+def parseArgument():
+  """
+  Very basic argument parser. Might blow up for anything else than
+  "./executable mysocket.sock stop/resume".
+  """
+  parser = argparse.ArgumentParser()
+  parser.add_argument('unix_socket_location')
+  parser.add_argument(
+      'action',
+      choices=[QMP_STOP_ACTION, QMP_RESUME_ACTION, QMP_CAPABILITIES_ACTION]
+  )
+  args = parser.parse_args()
+  return args.unix_socket_location, args.action
+
+
+class QemuQMPWrapper(object):
+  """
+  Small wrapper around Qemu's QMP to control a qemu VM.
+  See http://git.qemu.org/?p=qemu.git;a=blob;f=qmp-commands.hx for
+  QMP API definition.
+  """
+  def __init__(self, unix_socket_location):
+    self.socket = self.connectToQemu(unix_socket_location)
+    self.capabilities()
+
+  @staticmethod
+  def connectToQemu(unix_socket_location):
+    """
+    Create a socket, connect to qemu, be sure it answers, return socket.
+    """
+    if not os.path.exists(unix_socket_location):
+      raise Exception('unix socket %s does not exist.' % unix_socket_location)
+
+    print 'Connecting to qemu...'
+    so = socket.socket(socket.AF_UNIX, socket.SOCK_STREAM)
+    connected = False
+    while not connected:
+      try:
+        so.connect(unix_socket_location)
+      except socket.error:
+        time.sleep(1)
+        print 'Could not connect, retrying...'
+      else:
+        connected = True
+    so.recv(1024)
+
+    return so
+
+
+  def _send(self, message):
+    self.socket.send(json.dumps(message))
+    data = self.socket.recv(1024)
+    try:
+      return json.loads(data)
+    except ValueError:
+      print 'Wrong data: %s' % data
+
+  def _getVMStatus(self):
+    response = self._send({'execute': 'query-status'})
+    if response:
+      return self._send({'execute': 'query-status'})['return']['status']
+    else:
+      raise IOError('Empty answer')
+
+  def _waitForVMStatus(self, wanted_status):
+    while True:
+      try:
+        actual_status = self._getVMStatus()
+        if actual_status == wanted_status:
+          return
+        else:
+          print 'VM in %s status, wanting it to be %s, retrying...' % (
+              actual_status, wanted_status)
+          time.sleep(1)
+      except IOError:
+          print 'VM not ready, retrying...'
+
+
+  def capabilities(self):
+    print 'Asking for capabilities...'
+    self._send({'execute': 'qmp_capabilities'})
+
+  def suspend(self):
+    print 'Suspending VM...'
+    self._send({'execute': 'stop'})
+    self._waitForVMStatus('paused')
+
+  def resume(self):
+    print 'Resuming VM...'
+    self._send({'execute': 'cont'})
+    self._waitForVMStatus('running')
+
+
+def main():
+  unix_socket_location, action = parseArgument()
+  qemu_wrapper = QemuQMPWrapper(unix_socket_location)
+
+  if action == QMP_STOP_ACTION:
+    qemu_wrapper.suspend()
+  elif action == QMP_RESUME_ACTION:
+    qemu_wrapper.resume()
+  elif action == QMP_CAPABILITIES_ACTION:
+    qemu_wrapper.capabilities()
+
+if __name__ == '__main__':
+  main()