| """ QEMU Monitor Protocol Python class """ |
| # Copyright (C) 2009, 2010 Red Hat Inc. |
| # |
| # Authors: |
| # Luiz Capitulino <lcapitulino@redhat.com> |
| # |
| # This work is licensed under the terms of the GNU GPL, version 2. See |
| # the COPYING file in the top-level directory. |
| |
| import json |
| import errno |
| import socket |
| import logging |
| |
| |
| class QMPError(Exception): |
| """ |
| QMP base exception |
| """ |
| |
| |
| class QMPConnectError(QMPError): |
| """ |
| QMP connection exception |
| """ |
| |
| |
| class QMPCapabilitiesError(QMPError): |
| """ |
| QMP negotiate capabilities exception |
| """ |
| |
| |
| class QMPTimeoutError(QMPError): |
| """ |
| QMP timeout exception |
| """ |
| |
| |
| class QEMUMonitorProtocol: |
| """ |
| Provide an API to connect to QEMU via QEMU Monitor Protocol (QMP) and then |
| allow to handle commands and events. |
| """ |
| |
| #: Logger object for debugging messages |
| logger = logging.getLogger('QMP') |
| |
| 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 |
| @param server: server mode listens on the socket (bool) |
| @raise OSError 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 = None |
| if server: |
| self.__sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1) |
| self.__sock.bind(self.__address) |
| self.__sock.listen(1) |
| |
| def __get_sock(self): |
| if isinstance(self.__address, tuple): |
| family = socket.AF_INET |
| else: |
| family = socket.AF_UNIX |
| return socket.socket(family, socket.SOCK_STREAM) |
| |
| def __negotiate_capabilities(self): |
| greeting = self.__json_read() |
| if greeting is None or "QMP" not in greeting: |
| raise QMPConnectError |
| # Greeting seems ok, negotiate capabilities |
| resp = self.cmd('qmp_capabilities') |
| if resp and "return" in resp: |
| return greeting |
| raise QMPCapabilitiesError |
| |
| def __json_read(self, only_event=False): |
| while True: |
| data = self.__sockfile.readline() |
| if not data: |
| return None |
| resp = json.loads(data) |
| if 'event' in resp: |
| self.logger.debug("<<< %s", resp) |
| self.__events.append(resp) |
| if not only_event: |
| continue |
| return resp |
| |
| def __get_events(self, wait=False): |
| """ |
| Check for new events in the stream and cache them in __events. |
| |
| @param wait (bool): block until an event is available. |
| @param wait (float): If wait is a float, treat it as a timeout value. |
| |
| @raise QMPTimeoutError: If a timeout float is provided and the timeout |
| period elapses. |
| @raise QMPConnectError: If wait is True but no events could be |
| retrieved or if some other error occurred. |
| """ |
| |
| # Check for new events regardless and pull them into the cache: |
| self.__sock.setblocking(0) |
| try: |
| self.__json_read() |
| except OSError as err: |
| if err.errno == errno.EAGAIN: |
| # No data available |
| pass |
| self.__sock.setblocking(1) |
| |
| # Wait for new events, if needed. |
| # if wait is 0.0, this means "no wait" and is also implicitly false. |
| if not self.__events and wait: |
| if isinstance(wait, float): |
| self.__sock.settimeout(wait) |
| try: |
| ret = self.__json_read(only_event=True) |
| except socket.timeout: |
| raise QMPTimeoutError("Timeout waiting for event") |
| except: |
| raise QMPConnectError("Error while reading from socket") |
| if ret is None: |
| raise QMPConnectError("Error while reading from socket") |
| self.__sock.settimeout(None) |
| |
| def __enter__(self): |
| # Implement context manager enter function. |
| return self |
| |
| def __exit__(self, exc_type, exc_value, exc_traceback): |
| # Implement context manager exit function. |
| self.close() |
| return False |
| |
| def connect(self, negotiate=True): |
| """ |
| Connect to the QMP Monitor and perform capabilities negotiation. |
| |
| @return QMP greeting dict, or None if negotiate is false |
| @raise OSError on socket connection errors |
| @raise QMPConnectError if the greeting is not received |
| @raise QMPCapabilitiesError if fails to negotiate capabilities |
| """ |
| self.__sock.connect(self.__address) |
| self.__sockfile = self.__sock.makefile() |
| if negotiate: |
| return self.__negotiate_capabilities() |
| return None |
| |
| def accept(self, timeout=15.0): |
| """ |
| Await connection from QMP Monitor and perform capabilities negotiation. |
| |
| @param timeout: timeout in seconds (nonnegative float number, or |
| None). The value passed will set the behavior of the |
| underneath QMP socket as described in [1]. Default value |
| is set to 15.0. |
| @return QMP greeting dict |
| @raise OSError on socket connection errors |
| @raise QMPConnectError if the greeting is not received |
| @raise QMPCapabilitiesError if fails to negotiate capabilities |
| |
| [1] |
| https://docs.python.org/3/library/socket.html#socket.socket.settimeout |
| """ |
| self.__sock.settimeout(timeout) |
| self.__sock, _ = self.__sock.accept() |
| self.__sockfile = self.__sock.makefile() |
| return self.__negotiate_capabilities() |
| |
| def cmd_obj(self, qmp_cmd): |
| """ |
| Send a QMP command to the QMP Monitor. |
| |
| @param qmp_cmd: QMP command to be sent as a Python dict |
| @return QMP response as a Python dict or None if the connection has |
| been closed |
| """ |
| self.logger.debug(">>> %s", qmp_cmd) |
| try: |
| self.__sock.sendall(json.dumps(qmp_cmd).encode('utf-8')) |
| except OSError as err: |
| if err.errno == errno.EPIPE: |
| return None |
| raise err |
| resp = self.__json_read() |
| self.logger.debug("<<< %s", resp) |
| return resp |
| |
| def cmd(self, name, args=None, cmd_id=None): |
| """ |
| Build a QMP command and send it to the QMP Monitor. |
| |
| @param name: command name (string) |
| @param args: command arguments (dict) |
| @param cmd_id: command id (dict, list, string or int) |
| """ |
| qmp_cmd = {'execute': name} |
| if args: |
| qmp_cmd['arguments'] = args |
| if cmd_id: |
| qmp_cmd['id'] = cmd_id |
| return self.cmd_obj(qmp_cmd) |
| |
| def command(self, cmd, **kwds): |
| """ |
| Build and send a QMP command to the monitor, report errors if any |
| """ |
| ret = self.cmd(cmd, kwds) |
| if "error" in ret: |
| raise Exception(ret['error']['desc']) |
| return ret['return'] |
| |
| def pull_event(self, wait=False): |
| """ |
| Pulls a single event. |
| |
| @param wait (bool): block until an event is available. |
| @param wait (float): If wait is a float, treat it as a timeout value. |
| |
| @raise QMPTimeoutError: If a timeout float is provided and the timeout |
| period elapses. |
| @raise QMPConnectError: If wait is True but no events could be |
| retrieved or if some other error occurred. |
| |
| @return The first available QMP event, or None. |
| """ |
| self.__get_events(wait) |
| |
| if self.__events: |
| return self.__events.pop(0) |
| return None |
| |
| def get_events(self, wait=False): |
| """ |
| Get a list of available QMP events. |
| |
| @param wait (bool): block until an event is available. |
| @param wait (float): If wait is a float, treat it as a timeout value. |
| |
| @raise QMPTimeoutError: If a timeout float is provided and the timeout |
| period elapses. |
| @raise QMPConnectError: If wait is True but no events could be |
| retrieved or if some other error occurred. |
| |
| @return The list of available QMP events. |
| """ |
| self.__get_events(wait) |
| return self.__events |
| |
| def clear_events(self): |
| """ |
| Clear current list of pending events. |
| """ |
| self.__events = [] |
| |
| def close(self): |
| """ |
| Close the socket and socket file. |
| """ |
| if self.__sock: |
| self.__sock.close() |
| if self.__sockfile: |
| self.__sockfile.close() |
| |
| def settimeout(self, timeout): |
| """ |
| Set the socket timeout. |
| |
| @param timeout (float): timeout in seconds, or None. |
| @note This is a wrap around socket.settimeout |
| """ |
| self.__sock.settimeout(timeout) |
| |
| def get_sock_fd(self): |
| """ |
| Get the socket file descriptor. |
| |
| @return The file descriptor number. |
| """ |
| return self.__sock.fileno() |
| |
| def is_scm_available(self): |
| """ |
| Check if the socket allows for SCM_RIGHTS. |
| |
| @return True if SCM_RIGHTS is available, otherwise False. |
| """ |
| return self.__sock.family == socket.AF_UNIX |
