This patch *doesn't* update all of the docstring standards across the QEMU package directory to make our docstring usage consistent. It *doesn't* fix the formatting to make it look pretty or reasonable in generated output. It *does* fix a few small instances where Sphinx would emit a build warning because of malformed ReST -- If we built our Python docs with Sphinx. Signed-off-by: John Snow <jsnow@redhat.com> Reviewed-by: Willian Rampazzo <willianr@redhat.com> Reviewed-by: Wainer dos Santos Moschetta <wainersm@redhat.com> Message-id: 20210629214323.1329806-16-jsnow@redhat.com Signed-off-by: John Snow <jsnow@redhat.com>
424 lines
13 KiB
Python
424 lines
13 KiB
Python
"""
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QEMU Monitor Protocol (QMP) development library & tooling.
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This package provides a fairly low-level class for communicating to QMP
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protocol servers, as implemented by QEMU, the QEMU Guest Agent, and the
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QEMU Storage Daemon. This library is not intended for production use.
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`QEMUMonitorProtocol` is the primary class of interest, and all errors
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raised derive from `QMPError`.
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"""
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# Copyright (C) 2009, 2010 Red Hat Inc.
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#
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# Authors:
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# Luiz Capitulino <lcapitulino@redhat.com>
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#
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# This work is licensed under the terms of the GNU GPL, version 2. See
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# the COPYING file in the top-level directory.
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import errno
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import json
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import logging
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import socket
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from types import TracebackType
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from typing import (
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Any,
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Dict,
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List,
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Optional,
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TextIO,
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Tuple,
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Type,
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TypeVar,
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Union,
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cast,
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)
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#: QMPMessage is an entire QMP message of any kind.
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QMPMessage = Dict[str, Any]
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#: QMPReturnValue is the 'return' value of a command.
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QMPReturnValue = object
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#: QMPObject is any object in a QMP message.
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QMPObject = Dict[str, object]
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# QMPMessage can be outgoing commands or incoming events/returns.
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# QMPReturnValue is usually a dict/json object, but due to QAPI's
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# 'returns-whitelist', it can actually be anything.
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#
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# {'return': {}} is a QMPMessage,
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# {} is the QMPReturnValue.
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InternetAddrT = Tuple[str, int]
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UnixAddrT = str
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SocketAddrT = Union[InternetAddrT, UnixAddrT]
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class QMPError(Exception):
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"""
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QMP base exception
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"""
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class QMPConnectError(QMPError):
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"""
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QMP connection exception
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"""
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class QMPCapabilitiesError(QMPError):
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"""
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QMP negotiate capabilities exception
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"""
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class QMPTimeoutError(QMPError):
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"""
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QMP timeout exception
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"""
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class QMPProtocolError(QMPError):
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"""
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QMP protocol error; unexpected response
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"""
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class QMPResponseError(QMPError):
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"""
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Represents erroneous QMP monitor reply
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"""
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def __init__(self, reply: QMPMessage):
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try:
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desc = reply['error']['desc']
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except KeyError:
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desc = reply
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super().__init__(desc)
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self.reply = reply
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class QMPBadPortError(QMPError):
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"""
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Unable to parse socket address: Port was non-numerical.
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"""
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class QEMUMonitorProtocol:
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"""
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Provide an API to connect to QEMU via QEMU Monitor Protocol (QMP) and then
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allow to handle commands and events.
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"""
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#: Logger object for debugging messages
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logger = logging.getLogger('QMP')
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def __init__(self, address: SocketAddrT,
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server: bool = False,
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nickname: Optional[str] = None):
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"""
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Create a QEMUMonitorProtocol class.
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@param address: QEMU address, can be either a unix socket path (string)
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or a tuple in the form ( address, port ) for a TCP
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connection
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@param server: server mode listens on the socket (bool)
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@raise OSError on socket connection errors
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@note No connection is established, this is done by the connect() or
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accept() methods
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"""
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self.__events: List[QMPMessage] = []
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self.__address = address
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self.__sock = self.__get_sock()
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self.__sockfile: Optional[TextIO] = None
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self._nickname = nickname
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if self._nickname:
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self.logger = logging.getLogger('QMP').getChild(self._nickname)
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if server:
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self.__sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
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self.__sock.bind(self.__address)
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self.__sock.listen(1)
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def __get_sock(self) -> socket.socket:
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if isinstance(self.__address, tuple):
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family = socket.AF_INET
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else:
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family = socket.AF_UNIX
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return socket.socket(family, socket.SOCK_STREAM)
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def __negotiate_capabilities(self) -> QMPMessage:
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greeting = self.__json_read()
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if greeting is None or "QMP" not in greeting:
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raise QMPConnectError
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# Greeting seems ok, negotiate capabilities
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resp = self.cmd('qmp_capabilities')
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if resp and "return" in resp:
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return greeting
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raise QMPCapabilitiesError
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def __json_read(self, only_event: bool = False) -> Optional[QMPMessage]:
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assert self.__sockfile is not None
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while True:
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data = self.__sockfile.readline()
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if not data:
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return None
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# By definition, any JSON received from QMP is a QMPMessage,
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# and we are asserting only at static analysis time that it
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# has a particular shape.
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resp: QMPMessage = json.loads(data)
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if 'event' in resp:
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self.logger.debug("<<< %s", resp)
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self.__events.append(resp)
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if not only_event:
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continue
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return resp
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def __get_events(self, wait: Union[bool, float] = False) -> None:
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"""
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Check for new events in the stream and cache them in __events.
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@param wait (bool): block until an event is available.
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@param wait (float): If wait is a float, treat it as a timeout value.
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@raise QMPTimeoutError: If a timeout float is provided and the timeout
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period elapses.
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@raise QMPConnectError: If wait is True but no events could be
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retrieved or if some other error occurred.
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"""
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# Current timeout and blocking status
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current_timeout = self.__sock.gettimeout()
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# Check for new events regardless and pull them into the cache:
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self.__sock.settimeout(0) # i.e. setblocking(False)
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try:
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self.__json_read()
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except OSError as err:
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# EAGAIN: No data available; not critical
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if err.errno != errno.EAGAIN:
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raise
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finally:
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self.__sock.settimeout(current_timeout)
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# Wait for new events, if needed.
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# if wait is 0.0, this means "no wait" and is also implicitly false.
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if not self.__events and wait:
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if isinstance(wait, float):
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self.__sock.settimeout(wait)
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try:
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ret = self.__json_read(only_event=True)
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except socket.timeout as err:
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raise QMPTimeoutError("Timeout waiting for event") from err
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except Exception as err:
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msg = "Error while reading from socket"
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raise QMPConnectError(msg) from err
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finally:
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self.__sock.settimeout(current_timeout)
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if ret is None:
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raise QMPConnectError("Error while reading from socket")
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T = TypeVar('T')
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def __enter__(self: T) -> T:
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# Implement context manager enter function.
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return self
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def __exit__(self,
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# pylint: disable=duplicate-code
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# see https://github.com/PyCQA/pylint/issues/3619
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exc_type: Optional[Type[BaseException]],
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exc_val: Optional[BaseException],
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exc_tb: Optional[TracebackType]) -> None:
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# Implement context manager exit function.
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self.close()
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@classmethod
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def parse_address(cls, address: str) -> SocketAddrT:
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"""
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Parse a string into a QMP address.
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Figure out if the argument is in the port:host form.
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If it's not, it's probably a file path.
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"""
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components = address.split(':')
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if len(components) == 2:
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try:
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port = int(components[1])
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except ValueError:
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msg = f"Bad port: '{components[1]}' in '{address}'."
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raise QMPBadPortError(msg) from None
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return (components[0], port)
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# Treat as filepath.
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return address
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def connect(self, negotiate: bool = True) -> Optional[QMPMessage]:
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"""
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Connect to the QMP Monitor and perform capabilities negotiation.
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@return QMP greeting dict, or None if negotiate is false
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@raise OSError on socket connection errors
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@raise QMPConnectError if the greeting is not received
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@raise QMPCapabilitiesError if fails to negotiate capabilities
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"""
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self.__sock.connect(self.__address)
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self.__sockfile = self.__sock.makefile(mode='r')
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if negotiate:
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return self.__negotiate_capabilities()
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return None
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def accept(self, timeout: Optional[float] = 15.0) -> QMPMessage:
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"""
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Await connection from QMP Monitor and perform capabilities negotiation.
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@param timeout: timeout in seconds (nonnegative float number, or
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None). The value passed will set the behavior of the
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underneath QMP socket as described in [1].
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Default value is set to 15.0.
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@return QMP greeting dict
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@raise OSError on socket connection errors
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@raise QMPConnectError if the greeting is not received
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@raise QMPCapabilitiesError if fails to negotiate capabilities
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[1]
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https://docs.python.org/3/library/socket.html#socket.socket.settimeout
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"""
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self.__sock.settimeout(timeout)
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self.__sock, _ = self.__sock.accept()
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self.__sockfile = self.__sock.makefile(mode='r')
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return self.__negotiate_capabilities()
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def cmd_obj(self, qmp_cmd: QMPMessage) -> QMPMessage:
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"""
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Send a QMP command to the QMP Monitor.
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@param qmp_cmd: QMP command to be sent as a Python dict
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@return QMP response as a Python dict
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"""
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self.logger.debug(">>> %s", qmp_cmd)
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self.__sock.sendall(json.dumps(qmp_cmd).encode('utf-8'))
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resp = self.__json_read()
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if resp is None:
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raise QMPConnectError("Unexpected empty reply from server")
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self.logger.debug("<<< %s", resp)
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return resp
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def cmd(self, name: str,
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args: Optional[Dict[str, object]] = None,
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cmd_id: Optional[object] = None) -> QMPMessage:
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"""
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Build a QMP command and send it to the QMP Monitor.
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@param name: command name (string)
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@param args: command arguments (dict)
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@param cmd_id: command id (dict, list, string or int)
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"""
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qmp_cmd: QMPMessage = {'execute': name}
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if args:
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qmp_cmd['arguments'] = args
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if cmd_id:
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qmp_cmd['id'] = cmd_id
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return self.cmd_obj(qmp_cmd)
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def command(self, cmd: str, **kwds: object) -> QMPReturnValue:
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"""
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Build and send a QMP command to the monitor, report errors if any
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"""
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ret = self.cmd(cmd, kwds)
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if 'error' in ret:
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raise QMPResponseError(ret)
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if 'return' not in ret:
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raise QMPProtocolError(
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"'return' key not found in QMP response '{}'".format(str(ret))
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)
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return cast(QMPReturnValue, ret['return'])
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def pull_event(self,
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wait: Union[bool, float] = False) -> Optional[QMPMessage]:
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"""
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Pulls a single event.
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@param wait (bool): block until an event is available.
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@param wait (float): If wait is a float, treat it as a timeout value.
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@raise QMPTimeoutError: If a timeout float is provided and the timeout
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period elapses.
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@raise QMPConnectError: If wait is True but no events could be
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retrieved or if some other error occurred.
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@return The first available QMP event, or None.
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"""
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self.__get_events(wait)
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if self.__events:
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return self.__events.pop(0)
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return None
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def get_events(self, wait: bool = False) -> List[QMPMessage]:
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"""
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Get a list of available QMP events.
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@param wait (bool): block until an event is available.
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@param wait (float): If wait is a float, treat it as a timeout value.
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@raise QMPTimeoutError: If a timeout float is provided and the timeout
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period elapses.
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@raise QMPConnectError: If wait is True but no events could be
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retrieved or if some other error occurred.
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@return The list of available QMP events.
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"""
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self.__get_events(wait)
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return self.__events
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def clear_events(self) -> None:
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"""
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Clear current list of pending events.
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"""
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self.__events = []
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def close(self) -> None:
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"""
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Close the socket and socket file.
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"""
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if self.__sock:
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self.__sock.close()
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if self.__sockfile:
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self.__sockfile.close()
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def settimeout(self, timeout: Optional[float]) -> None:
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"""
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Set the socket timeout.
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@param timeout (float): timeout in seconds (non-zero), or None.
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@note This is a wrap around socket.settimeout
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@raise ValueError: if timeout was set to 0.
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"""
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if timeout == 0:
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msg = "timeout cannot be 0; this engages non-blocking mode."
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msg += " Use 'None' instead to disable timeouts."
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raise ValueError(msg)
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self.__sock.settimeout(timeout)
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def get_sock_fd(self) -> int:
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"""
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Get the socket file descriptor.
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@return The file descriptor number.
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"""
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return self.__sock.fileno()
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def is_scm_available(self) -> bool:
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"""
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Check if the socket allows for SCM_RIGHTS.
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@return True if SCM_RIGHTS is available, otherwise False.
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"""
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return self.__sock.family == socket.AF_UNIX
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