Commit 37628f11 authored by Stefan Hajnoczi's avatar Stefan Hajnoczi Committed by Luiz Capitulino
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QMP: add server mode to QEMUMonitorProtocol 



QEMU supports socket chardevs that establish connections like a server
or a client.  The QEMUMonitorProtocol class only supports connecting as
a client.  It is not possible to connect race-free when launching QEMU
since trying to connect before QEMU has bound and is listening on the
socket results in failure.

Add the QEMUMonitorProtocol(server=True) argument to bind and listen on
the socket.  The QEMU process can then be launched and connects to the
already existing QMP socket without a race condition:

  qmp = qmp.QEMUMonitorProtocol(monitor_path, server=True)
  popen = subprocess.Popen(args)
  qmp.accept()

Signed-off-by: default avatarStefan Hajnoczi <stefanha@linux.vnet.ibm.com>
Signed-off-by: default avatarLuiz Capitulino <lcapitulino@redhat.com>
parent 91b8eddf

QMP/qmp.py

+32 −11
Original line number Diff line number Diff line
@@ -22,19 +22,24 @@ class QMPCapabilitiesError(QMPError): 
    pass



class QEMUMonitorProtocol:

    def __init__(self, address):

    def __init__(self, address, server=False):

        """

        Create a QEMUMonitorProtocol class.



        @param address: QEMU address, can be either a unix socket path (string)

                        or a tuple in the form ( address, port ) for a TCP

                        connection

        @note No connection is established, this is done by the connect() method

        @param server: server mode listens on the socket (bool)

        @raise socket.error on socket connection errors

        @note No connection is established, this is done by the connect() or

              accept() methods

        """

        self.__events = []

        self.__address = address

        self.__sock = self.__get_sock()

        self.__sockfile = self.__sock.makefile()

        if server:

            self.__sock.bind(self.__address)

            self.__sock.listen(1)



    def __get_sock(self):

        if isinstance(self.__address, tuple):
@@ -43,6 +48,17 @@ class QEMUMonitorProtocol: 
            family = socket.AF_UNIX

        return socket.socket(family, socket.SOCK_STREAM)



    def __negotiate_capabilities(self):

        self.__sockfile = self.__sock.makefile()

        greeting = self.__json_read()

        if greeting is None or not greeting.has_key('QMP'):

            raise QMPConnectError

        # Greeting seems ok, negotiate capabilities

        resp = self.cmd('qmp_capabilities')

        if "return" in resp:

            return greeting

        raise QMPCapabilitiesError



    def __json_read(self, only_event=False):

        while True:

            data = self.__sockfile.readline()
@@ -67,14 +83,19 @@ class QEMUMonitorProtocol: 
        @raise QMPCapabilitiesError if fails to negotiate capabilities

        """

        self.__sock.connect(self.__address)

        greeting = self.__json_read()

        if greeting is None or not greeting.has_key('QMP'):

            raise QMPConnectError

        # Greeting seems ok, negotiate capabilities

        resp = self.cmd('qmp_capabilities')

        if "return" in resp:

            return greeting

        raise QMPCapabilitiesError

        return self.__negotiate_capabilities()



    def accept(self):

        """

        Await connection from QMP Monitor and perform capabilities negotiation.



        @return QMP greeting dict

        @raise socket.error on socket connection errors

        @raise QMPConnectError if the greeting is not received

        @raise QMPCapabilitiesError if fails to negotiate capabilities

        """

        self.__sock, _ = self.__sock.accept()

        return self.__negotiate_capabilities()



    def cmd_obj(self, qmp_cmd):

        """