python: support recording QMP session to a file

When running QMP commands with very large response payloads, it is often
not easy to spot the info you want. If we can save the response to a
file then tools like 'grep' or 'jq' can be used to extract information.

For convenience of processing, we merge the QMP command and response
dictionaries together:

  {
      "arguments": {},
      "execute": "query-kvm",
      "return": {
          "enabled": false,
          "present": true
      }
  }

Example usage

  $ ./scripts/qmp/qmp-shell-wrap -l q.log -p -- ./build/qemu-system-x86_64 -display none
  Welcome to the QMP low-level shell!
  Connected
  (QEMU) query-kvm
  {
      "return": {
          "enabled": false,
          "present": true
      }
  }
  (QEMU) query-mice
  {
      "return": [
          {
              "absolute": false,
              "current": true,
              "index": 2,
              "name": "QEMU PS/2 Mouse"
          }
      ]
  }

 $ jq --slurp '. | to_entries[] | select(.value.execute == "query-kvm") |
               .value.return.enabled' < q.log
   false

Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
Message-id: 20220128161157.36261-3-berrange@redhat.com
Signed-off-by: John Snow <jsnow@redhat.com>
This commit is contained in:
Daniel P. Berrangé 2022-01-28 16:11:57 +00:00 committed by John Snow
parent 439125293c
commit 5c66d7d8de
2 changed files with 25 additions and 7 deletions

View File

@ -89,6 +89,7 @@ import readline
from subprocess import Popen
import sys
from typing import (
IO,
Iterator,
List,
NoReturn,
@ -170,7 +171,8 @@ class QMPShell(QEMUMonitorProtocol):
def __init__(self, address: SocketAddrT,
pretty: bool = False,
verbose: bool = False,
server: bool = False):
server: bool = False,
logfile: Optional[str] = None):
super().__init__(address, server=server)
self._greeting: Optional[QMPMessage] = None
self._completer = QMPCompleter()
@ -180,6 +182,10 @@ class QMPShell(QEMUMonitorProtocol):
'.qmp-shell_history')
self.pretty = pretty
self.verbose = verbose
self.logfile = None
if logfile is not None:
self.logfile = open(logfile, "w", encoding='utf-8')
def close(self) -> None:
# Hook into context manager of parent to save shell history.
@ -320,11 +326,11 @@ class QMPShell(QEMUMonitorProtocol):
self._cli_expr(cmdargs[1:], qmpcmd['arguments'])
return qmpcmd
def _print(self, qmp_message: object) -> None:
def _print(self, qmp_message: object, fh: IO[str] = sys.stdout) -> None:
jsobj = json.dumps(qmp_message,
indent=4 if self.pretty else None,
sort_keys=self.pretty)
print(str(jsobj))
print(str(jsobj), file=fh)
def _execute_cmd(self, cmdline: str) -> bool:
try:
@ -347,6 +353,9 @@ class QMPShell(QEMUMonitorProtocol):
print('Disconnected')
return False
self._print(resp)
if self.logfile is not None:
cmd = {**qmpcmd, **resp}
self._print(cmd, fh=self.logfile)
return True
def connect(self, negotiate: bool = True) -> None:
@ -414,8 +423,9 @@ class HMPShell(QMPShell):
def __init__(self, address: SocketAddrT,
pretty: bool = False,
verbose: bool = False,
server: bool = False):
super().__init__(address, pretty, verbose, server)
server: bool = False,
logfile: Optional[str] = None):
super().__init__(address, pretty, verbose, server, logfile)
self._cpu_index = 0
def _cmd_completion(self) -> None:
@ -508,6 +518,8 @@ def main() -> None:
help='Verbose (echo commands sent and received)')
parser.add_argument('-p', '--pretty', action='store_true',
help='Pretty-print JSON')
parser.add_argument('-l', '--logfile',
help='Save log of all QMP messages to PATH')
default_server = os.environ.get('QMP_SOCKET')
parser.add_argument('qmp_server', action='store',
@ -526,7 +538,7 @@ def main() -> None:
parser.error(f"Bad port number: {args.qmp_server}")
return # pycharm doesn't know error() is noreturn
with shell_class(address, args.pretty, args.verbose) as qemu:
with shell_class(address, args.pretty, args.verbose, args.logfile) as qemu:
try:
qemu.connect(negotiate=not args.skip_negotiation)
except ConnectError as err:
@ -550,6 +562,8 @@ def main_wrap() -> None:
help='Verbose (echo commands sent and received)')
parser.add_argument('-p', '--pretty', action='store_true',
help='Pretty-print JSON')
parser.add_argument('-l', '--logfile',
help='Save log of all QMP messages to PATH')
parser.add_argument('command', nargs=argparse.REMAINDER,
help='QEMU command line to invoke')
@ -574,7 +588,8 @@ def main_wrap() -> None:
return # pycharm doesn't know error() is noreturn
try:
with shell_class(address, args.pretty, args.verbose, True) as qemu:
with shell_class(address, args.pretty, args.verbose,
True, args.logfile) as qemu:
with Popen(cmd):
try:

View File

@ -114,7 +114,10 @@ ignore_missing_imports = True
# no Warning level messages displayed, use "--disable=all --enable=classes
# --disable=W".
disable=consider-using-f-string,
consider-using-with,
too-many-arguments,
too-many-function-args, # mypy handles this with less false positives.
too-many-instance-attributes,
no-member, # mypy also handles this better.
[pylint.basic]