Re: [RFC PATCH] python: add qmp-send program to send raw qmp commands to qemu

[John Snow <jsnow@redhat.com>]

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On Tue, Apr 5, 2022, 5:03 AM Damien Hedde <damien.hedde@greensocs.com>
wrote:

>
>
> On 4/4/22 22:34, John Snow wrote:
> > On Wed, Mar 16, 2022 at 5:55 AM Damien Hedde <damien.hedde@greensocs.com>
> wrote:
> >>
> >> It takes an input file containing raw qmp commands (concatenated json
> >> dicts) and send all commands one by one to a qmp server. When one
> >> command fails, it exits.
> >>
> >> As a convenience, it can also wrap the qemu process to avoid having
> >> to start qemu in background. When wrapping qemu, the program returns
> >> only when the qemu process terminates.
> >>
> >> Signed-off-by: Damien Hedde <damien.hedde@greensocs.com>
> >> ---
> >>
> >> Hi all,
> >>
> >> Following our discussion, I've started this. What do you think ?
> >>
> >> I tried to follow Daniel's qmp-shell-wrap. I think it is
> >> better to have similar options (eg: logging). There is also room
> >> for factorizing code if we want to keep them aligned and ease
> >> maintenance.
> >>
> >> There are still some pylint issues (too many branches in main and it
> >> does not like my context manager if else line). But it's kind of a
> >> mess to fix theses so I think it's enough for a first version.
> >
> > Yeah, don't worry about these. You can just tell pylint to shut up
> > while you prototype. Sometimes it's just not worth spending more time
> > on a more beautiful factoring. Oh well.
> >
> >>
> >> I name that qmp-send as Daniel proposed, maybe qmp-test matches better
> >> what I'm doing there ?
> >>
> >
> > I think I agree with Dan's response.
> >
> >> Thanks,
> >> Damien
> >> ---
> >>   python/qemu/aqmp/qmp_send.py | 229 +++++++++++++++++++++++++++++++++++
> >
> > I recommend putting this in qemu/util/qmp_send.py instead.
> >
> > I'm in the process of pulling out the AQMP lib and hosting it
> > separately. Scripts like this I think should stay in the QEMU tree, so
> > moving it to util instead is probably best. Otherwise, I'll *really*
> > have to commit to the syntax, and that's probably a bigger hurdle than
> > you want to deal with.
>
> If it stays in QEMU tree, what licensing should I use ? LGPL does not
> hurt, no ?
>

Whichever you please. GPLv2+ would be convenient and harmonizes well with
other tools. LGPL is only something I started doing so that the "qemu.qmp"
package would be LGPL. Licensing the tools as LGPL was just a sin of
convenience so I could claim a single license for the whole wheel/egg/tgz.

(I didn't want to make separate qmp and qmp-tools packages.)

Go with what you feel is best.


> >
> >>   scripts/qmp/qmp-send         |  11 ++
> >>   2 files changed, 240 insertions(+)
> >>   create mode 100644 python/qemu/aqmp/qmp_send.py
> >>   create mode 100755 scripts/qmp/qmp-send
> >>
> >> diff --git a/python/qemu/aqmp/qmp_send.py b/python/qemu/aqmp/qmp_send.py
> >> new file mode 100644
> >> index 0000000000..cbca1d0205
> >> --- /dev/null
> >> +++ b/python/qemu/aqmp/qmp_send.py
> >
> > Seems broadly fine to me, but I didn't review closely this time. If it
> > works for you, it works for me.
> >
> > As for making QEMU hang: there's a few things you could do, take a
> > look at iotests and see how they handle timeout blocks in synchronous
> > code -- iotests.py line 696 or so, "class Timeout". When writing async
> > code, you can also do stuff like this:
> >
> > async def foo():
> >      await asyncio.wait_for(qmp.execute("some-command", args_etc),
> timeout=30)
> >
> > See https://docs.python.org/3/library/asyncio-task.html#asyncio.wait_for
> >
> > --js
> >
>
> Thanks for the tip,
> --
> Damien
>

Oh, and one more. the legacy.py bindings for AQMP also support a
configurable timeout that applies to most API calls by default.

see https://gitlab.com/jsnow/qemu.qmp/-/blob/main/qemu/qmp/legacy.py#L285

(Branch still in limbo here, but it should still be close to the same in
qemu.git)

I believe this is used by iotests.py when it sets up its machine.py
subclass ("VM", iirc) so that most qmp invocations in iotests have a
default timeout and won't hang tests indefinitely.

--js

>

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