[v3,3/3] python/qemu/machine: use socketpair() for QMP by default

From: Marc-André Lureau <marcandre.lureau@redhat.com>

When no monitor address is given, establish the QMP communication through
a socketpair() (API is also supported on Windows since Python 3.5)

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
---
 python/qemu/machine/machine.py | 24 ++++++++++++++++--------
 1 file changed, 16 insertions(+), 8 deletions(-)

On Wed, Jan 11, 2023 at 3:01 AM <marcandre.lureau@redhat.com> wrote:
>
> From: Marc-André Lureau <marcandre.lureau@redhat.com>
>
> When no monitor address is given, establish the QMP communication through
> a socketpair() (API is also supported on Windows since Python 3.5)
>
> Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
> Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
> ---
>  python/qemu/machine/machine.py | 24 ++++++++++++++++--------
>  1 file changed, 16 insertions(+), 8 deletions(-)
>
> diff --git a/python/qemu/machine/machine.py b/python/qemu/machine/machine.py
> index 748a0d807c..5b2e499e68 100644
> --- a/python/qemu/machine/machine.py
> +++ b/python/qemu/machine/machine.py
> @@ -158,17 +158,13 @@ def __init__(self,
>          self._qmp_timer = qmp_timer
>
>          self._name = name or f"qemu-{os.getpid()}-{id(self):02x}"
> +        self._sock_pair: Optional[Tuple[socket.socket, socket.socket]] = None
>          self._temp_dir: Optional[str] = None
>          self._base_temp_dir = base_temp_dir
>          self._sock_dir = sock_dir
>          self._log_dir = log_dir
>
> -        if monitor_address is not None:
> -            self._monitor_address = monitor_address
> -        else:
> -            self._monitor_address = os.path.join(
> -                self.sock_dir, f"{self._name}-monitor.sock"
> -            )
> +        self._monitor_address = monitor_address
>
>          self._console_log_path = console_log
>          if self._console_log_path:
> @@ -303,7 +299,11 @@ def _base_args(self) -> List[str]:
>          args = ['-display', 'none', '-vga', 'none']
>
>          if self._qmp_set:
> -            if isinstance(self._monitor_address, tuple):
> +            if self._sock_pair:
> +                fd = self._sock_pair[0].fileno()
> +                os.set_inheritable(fd, True)
> +                moncdev = f"socket,id=mon,fd={fd}"
> +            elif isinstance(self._monitor_address, tuple):
>                  moncdev = "socket,id=mon,host={},port={}".format(
>                      *self._monitor_address
>                  )
> @@ -337,10 +337,17 @@ def _pre_launch(self) -> None:
>              self._remove_files.append(self._console_address)
>
>          if self._qmp_set:
> +            monitor_address = None
> +            sock = None
> +            if self._monitor_address is None:
> +                self._sock_pair = socket.socketpair()
> +                sock = self._sock_pair[1]
>              if isinstance(self._monitor_address, str):
>                  self._remove_files.append(self._monitor_address)
> +                monitor_address = self._monitor_address
>              self._qmp_connection = QEMUMonitorProtocol(
> -                self._monitor_address,
> +                address=monitor_address,
> +                sock=sock,
>                  server=True,
>                  nickname=self._name
>              )
> @@ -360,6 +367,7 @@ def _pre_launch(self) -> None:
>          ))
>
>      def _post_launch(self) -> None:
> +        self._sock_pair[0].close()

Needs an assert or an error-check here for _sock_pair to be non-None,
otherwise mypy will shout. Try running "make check-dev" from
qemu.git/python directory as a smoke test.


>          if self._qmp_connection:
>              self._qmp.accept(self._qmp_timer)
>
> --
> 2.39.0
>

Hi

On Wed, Jan 18, 2023 at 2:36 AM John Snow <jsnow@redhat.com> wrote:
>
> On Wed, Jan 11, 2023 at 3:01 AM <marcandre.lureau@redhat.com> wrote:
> >
> > From: Marc-André Lureau <marcandre.lureau@redhat.com>
> >
> > When no monitor address is given, establish the QMP communication through
> > a socketpair() (API is also supported on Windows since Python 3.5)
> >
> > Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
> > Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
> > ---
> >  python/qemu/machine/machine.py | 24 ++++++++++++++++--------
> >  1 file changed, 16 insertions(+), 8 deletions(-)
> >
> > diff --git a/python/qemu/machine/machine.py b/python/qemu/machine/machine.py
> > index 748a0d807c..5b2e499e68 100644
> > --- a/python/qemu/machine/machine.py
> > +++ b/python/qemu/machine/machine.py
> > @@ -158,17 +158,13 @@ def __init__(self,
> >          self._qmp_timer = qmp_timer
> >
> >          self._name = name or f"qemu-{os.getpid()}-{id(self):02x}"
> > +        self._sock_pair: Optional[Tuple[socket.socket, socket.socket]] = None
> >          self._temp_dir: Optional[str] = None
> >          self._base_temp_dir = base_temp_dir
> >          self._sock_dir = sock_dir
> >          self._log_dir = log_dir
> >
> > -        if monitor_address is not None:
> > -            self._monitor_address = monitor_address
> > -        else:
> > -            self._monitor_address = os.path.join(
> > -                self.sock_dir, f"{self._name}-monitor.sock"
> > -            )
> > +        self._monitor_address = monitor_address
> >
> >          self._console_log_path = console_log
> >          if self._console_log_path:
> > @@ -303,7 +299,11 @@ def _base_args(self) -> List[str]:
> >          args = ['-display', 'none', '-vga', 'none']
> >
> >          if self._qmp_set:
> > -            if isinstance(self._monitor_address, tuple):
> > +            if self._sock_pair:
> > +                fd = self._sock_pair[0].fileno()
> > +                os.set_inheritable(fd, True)
> > +                moncdev = f"socket,id=mon,fd={fd}"
> > +            elif isinstance(self._monitor_address, tuple):
> >                  moncdev = "socket,id=mon,host={},port={}".format(
> >                      *self._monitor_address
> >                  )
> > @@ -337,10 +337,17 @@ def _pre_launch(self) -> None:
> >              self._remove_files.append(self._console_address)
> >
> >          if self._qmp_set:
> > +            monitor_address = None
> > +            sock = None
> > +            if self._monitor_address is None:
> > +                self._sock_pair = socket.socketpair()
> > +                sock = self._sock_pair[1]
> >              if isinstance(self._monitor_address, str):
> >                  self._remove_files.append(self._monitor_address)
> > +                monitor_address = self._monitor_address
> >              self._qmp_connection = QEMUMonitorProtocol(
> > -                self._monitor_address,
> > +                address=monitor_address,
> > +                sock=sock,
> >                  server=True,
> >                  nickname=self._name
> >              )
> > @@ -360,6 +367,7 @@ def _pre_launch(self) -> None:
> >          ))
> >
> >      def _post_launch(self) -> None:
> > +        self._sock_pair[0].close()
>
> Needs an assert or an error-check here for _sock_pair to be non-None,
> otherwise mypy will shout. Try running "make check-dev" from
> qemu.git/python directory as a smoke test.

Good catch, it should be:

+        if self._sock_pair:
+            self._sock_pair[0].close()

Let me know if you want me to resend the whole series, or if you can
touch it during picking.

On Wed, Jan 18, 2023 at 3:03 AM Marc-André Lureau
<marcandre.lureau@gmail.com> wrote:
>
> Hi
>
> On Wed, Jan 18, 2023 at 2:36 AM John Snow <jsnow@redhat.com> wrote:
> >
> > On Wed, Jan 11, 2023 at 3:01 AM <marcandre.lureau@redhat.com> wrote:
> > >
> > > From: Marc-André Lureau <marcandre.lureau@redhat.com>
> > >
> > > When no monitor address is given, establish the QMP communication through
> > > a socketpair() (API is also supported on Windows since Python 3.5)
> > >
> > > Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
> > > Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
> > > ---
> > >  python/qemu/machine/machine.py | 24 ++++++++++++++++--------
> > >  1 file changed, 16 insertions(+), 8 deletions(-)
> > >
> > > diff --git a/python/qemu/machine/machine.py b/python/qemu/machine/machine.py
> > > index 748a0d807c..5b2e499e68 100644
> > > --- a/python/qemu/machine/machine.py
> > > +++ b/python/qemu/machine/machine.py
> > > @@ -158,17 +158,13 @@ def __init__(self,
> > >          self._qmp_timer = qmp_timer
> > >
> > >          self._name = name or f"qemu-{os.getpid()}-{id(self):02x}"
> > > +        self._sock_pair: Optional[Tuple[socket.socket, socket.socket]] = None
> > >          self._temp_dir: Optional[str] = None
> > >          self._base_temp_dir = base_temp_dir
> > >          self._sock_dir = sock_dir
> > >          self._log_dir = log_dir
> > >
> > > -        if monitor_address is not None:
> > > -            self._monitor_address = monitor_address
> > > -        else:
> > > -            self._monitor_address = os.path.join(
> > > -                self.sock_dir, f"{self._name}-monitor.sock"
> > > -            )
> > > +        self._monitor_address = monitor_address
> > >
> > >          self._console_log_path = console_log
> > >          if self._console_log_path:
> > > @@ -303,7 +299,11 @@ def _base_args(self) -> List[str]:
> > >          args = ['-display', 'none', '-vga', 'none']
> > >
> > >          if self._qmp_set:
> > > -            if isinstance(self._monitor_address, tuple):
> > > +            if self._sock_pair:
> > > +                fd = self._sock_pair[0].fileno()
> > > +                os.set_inheritable(fd, True)
> > > +                moncdev = f"socket,id=mon,fd={fd}"
> > > +            elif isinstance(self._monitor_address, tuple):
> > >                  moncdev = "socket,id=mon,host={},port={}".format(
> > >                      *self._monitor_address
> > >                  )
> > > @@ -337,10 +337,17 @@ def _pre_launch(self) -> None:
> > >              self._remove_files.append(self._console_address)
> > >
> > >          if self._qmp_set:
> > > +            monitor_address = None
> > > +            sock = None
> > > +            if self._monitor_address is None:
> > > +                self._sock_pair = socket.socketpair()
> > > +                sock = self._sock_pair[1]
> > >              if isinstance(self._monitor_address, str):
> > >                  self._remove_files.append(self._monitor_address)
> > > +                monitor_address = self._monitor_address
> > >              self._qmp_connection = QEMUMonitorProtocol(
> > > -                self._monitor_address,
> > > +                address=monitor_address,
> > > +                sock=sock,
> > >                  server=True,
> > >                  nickname=self._name
> > >              )
> > > @@ -360,6 +367,7 @@ def _pre_launch(self) -> None:
> > >          ))
> > >
> > >      def _post_launch(self) -> None:
> > > +        self._sock_pair[0].close()
> >
> > Needs an assert or an error-check here for _sock_pair to be non-None,
> > otherwise mypy will shout. Try running "make check-dev" from
> > qemu.git/python directory as a smoke test.
>
> Good catch, it should be:
>
> +        if self._sock_pair:
> +            self._sock_pair[0].close()
>
> Let me know if you want me to resend the whole series, or if you can
> touch it during picking.

Touching it up during picking, running tests, PR soon. Thanks,
--js

Hi!

By my investigation, this commit (bd4c0ef409140bd1be393407c04005ac077d4574) breaks long qmp output again.

Simple test:

$ cd python
$ cat test.py
#!/usr/bin/env python3

import sys
from qemu.machine import QEMUMachine

monitor_address = sys.argv[2] if len(sys.argv) > 2 else None
vm = QEMUMachine('../build/qemu-system-x86_64',
                  monitor_address=monitor_address)
vm.launch()

for x in range(int(sys.argv[1])):
     vm.qmp('blockdev-add', {'driver': 'null-co', 'node-name': f'x{x}'})

vm.qmp('query-named-block-nodes')
vm.shutdown()


./test.py 1000 /tmp/sock

   - works, but if use default behavior (socketpair) we get:

$ ./test.py 1000
Traceback (most recent call last):
   File "/home/vsementsov/work/src/qemu/master/python/./test.py", line 14, in <module>
     vm.qmp('query-named-block-nodes')
   File "/home/vsementsov/work/src/qemu/master/python/qemu/machine/machine.py", line 686, in qmp
     ret = self._qmp.cmd(cmd, args=qmp_args)
   File "/home/vsementsov/work/src/qemu/master/python/qemu/qmp/legacy.py", line 216, in cmd
     return self.cmd_obj(qmp_cmd)
   File "/home/vsementsov/work/src/qemu/master/python/qemu/qmp/legacy.py", line 190, in cmd_obj
     self._sync(
   File "/home/vsementsov/work/src/qemu/master/python/qemu/qmp/legacy.py", line 105, in _sync
     return self._aloop.run_until_complete(
   File "/usr/lib/python3.10/asyncio/base_events.py", line 646, in run_until_complete
     return future.result()
   File "/usr/lib/python3.10/asyncio/tasks.py", line 408, in wait_for
     return await fut
   File "/home/vsementsov/work/src/qemu/master/python/qemu/qmp/qmp_client.py", line 547, in _raw
     return await self._execute(msg, assign_id=assign_id)
   File "/home/vsementsov/work/src/qemu/master/python/qemu/qmp/qmp_client.py", line 496, in _execute
     return await self._reply(exec_id)
   File "/home/vsementsov/work/src/qemu/master/python/qemu/qmp/qmp_client.py", line 463, in _reply
     raise result
qemu.qmp.qmp_client.ExecInterruptedError: Disconnected
Exception ignored in: <function QEMUMonitorProtocol.__del__ at 0x7f8708283eb0>
Traceback (most recent call last):
   File "/home/vsementsov/work/src/qemu/master/python/qemu/qmp/legacy.py", line 318, in __del__
   File "/home/vsementsov/work/src/qemu/master/python/qemu/qmp/legacy.py", line 289, in close
   File "/home/vsementsov/work/src/qemu/master/python/qemu/qmp/legacy.py", line 105, in _sync
   File "/usr/lib/python3.10/asyncio/base_events.py", line 646, in run_until_complete
   File "/usr/lib/python3.10/asyncio/tasks.py", line 408, in wait_for
   File "/home/vsementsov/work/src/qemu/master/python/qemu/qmp/protocol.py", line 413, in disconnect
   File "/home/vsementsov/work/src/qemu/master/python/qemu/qmp/protocol.py", line 725, in _wait_disconnect
   File "/home/vsementsov/work/src/qemu/master/python/qemu/qmp/protocol.py", line 876, in _bh_loop_forever
   File "/home/vsementsov/work/src/qemu/master/python/qemu/qmp/protocol.py", line 914, in _bh_recv_message
   File "/home/vsementsov/work/src/qemu/master/python/qemu/qmp/protocol.py", line 1015, in _recv
   File "/home/vsementsov/work/src/qemu/master/python/qemu/qmp/qmp_client.py", line 402, in _do_recv
   File "/home/vsementsov/work/src/qemu/master/python/qemu/qmp/protocol.py", line 979, in _readline
   File "/usr/lib/python3.10/asyncio/streams.py", line 534, in readline
ValueError: Separator is not found, and chunk exceed the limit



./test.py 100
   - works well.


On 11.01.23 11:01, marcandre.lureau@redhat.com wrote:
> From: Marc-André Lureau <marcandre.lureau@redhat.com>
> 
> When no monitor address is given, establish the QMP communication through
> a socketpair() (API is also supported on Windows since Python 3.5)
> 
> Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
> Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
> ---
>   python/qemu/machine/machine.py | 24 ++++++++++++++++--------
>   1 file changed, 16 insertions(+), 8 deletions(-)
> 
> diff --git a/python/qemu/machine/machine.py b/python/qemu/machine/machine.py
> index 748a0d807c..5b2e499e68 100644
> --- a/python/qemu/machine/machine.py
> +++ b/python/qemu/machine/machine.py
> @@ -158,17 +158,13 @@ def __init__(self,
>           self._qmp_timer = qmp_timer
>   
>           self._name = name or f"qemu-{os.getpid()}-{id(self):02x}"
> +        self._sock_pair: Optional[Tuple[socket.socket, socket.socket]] = None
>           self._temp_dir: Optional[str] = None
>           self._base_temp_dir = base_temp_dir
>           self._sock_dir = sock_dir
>           self._log_dir = log_dir
>   
> -        if monitor_address is not None:
> -            self._monitor_address = monitor_address
> -        else:
> -            self._monitor_address = os.path.join(
> -                self.sock_dir, f"{self._name}-monitor.sock"
> -            )
> +        self._monitor_address = monitor_address
>   
>           self._console_log_path = console_log
>           if self._console_log_path:
> @@ -303,7 +299,11 @@ def _base_args(self) -> List[str]:
>           args = ['-display', 'none', '-vga', 'none']
>   
>           if self._qmp_set:
> -            if isinstance(self._monitor_address, tuple):
> +            if self._sock_pair:
> +                fd = self._sock_pair[0].fileno()
> +                os.set_inheritable(fd, True)
> +                moncdev = f"socket,id=mon,fd={fd}"
> +            elif isinstance(self._monitor_address, tuple):
>                   moncdev = "socket,id=mon,host={},port={}".format(
>                       *self._monitor_address
>                   )
> @@ -337,10 +337,17 @@ def _pre_launch(self) -> None:
>               self._remove_files.append(self._console_address)
>   
>           if self._qmp_set:
> +            monitor_address = None
> +            sock = None
> +            if self._monitor_address is None:
> +                self._sock_pair = socket.socketpair()
> +                sock = self._sock_pair[1]
>               if isinstance(self._monitor_address, str):
>                   self._remove_files.append(self._monitor_address)
> +                monitor_address = self._monitor_address
>               self._qmp_connection = QEMUMonitorProtocol(
> -                self._monitor_address,
> +                address=monitor_address,
> +                sock=sock,
>                   server=True,
>                   nickname=self._name
>               )
> @@ -360,6 +367,7 @@ def _pre_launch(self) -> None:
>           ))
>   
>       def _post_launch(self) -> None:
> +        self._sock_pair[0].close()
>           if self._qmp_connection:
>               self._qmp.accept(self._qmp_timer)
>

On Fri, Mar 17, 2023 at 10:36:37PM +0300, Vladimir Sementsov-Ogievskiy wrote:
> Hi!
> 
> By my investigation, this commit (bd4c0ef409140bd1be393407c04005ac077d4574) breaks long qmp output again.

> 
> ./test.py 1000 /tmp/sock
> 
>   - works, but if use default behavior (socketpair) we get:
> 
> $ ./test.py 1000
> Traceback (most recent call last):

snip

>   File "/usr/lib/python3.10/asyncio/streams.py", line 534, in readline
> ValueError: Separator is not found, and chunk exceed the limit

After going off in the weeds I realized this message is the key bit. We
failed to pass the raised recv limit to asyncio when using a pre-opened
socket. Since the QMP reply was greater than 64kb asyncio raised an
exception. This was a pre-existing latent bug, exposed with the patch
to enable use of socketpair(). I've CC'd you on a patch to fix this.

With regards,
Daniel