Re: [Qemu-devel] [RFC PATCH v2] qmp.py: Fix exception parsing partial JSON

[Eduardo Habkost]

On Fri, Jun 08, 2018 at 07:57:55PM +0200, Lukáš Doktor wrote:
> Hello guys,
> 
> Dne 7.6.2018 v 01:06 Philippe Mathieu-Daudé napsal(a):
> > On 06/06/2018 05:05 PM, Eduardo Habkost wrote:
> >> On Wed, Jun 06, 2018 at 04:27:31PM -0300, Philippe Mathieu-Daudé wrote:
> >>> The readline() call returns partial data.
> >>
> >> How can this be reproduced?  Despite not being forbidden by the
> >> QMP specification, QEMU normally doesn't break QMP replies in
> >> multiple lines, and readline() is not supposed to return a
> >> partial line unless it encounters EOF.
> > 
> > $ git rev-parse HEAD
> > c1c2a435905ae76b159c573b0c0d6f095b45ebc6
> > 
> > config copy/pasted from:
> > https://wiki.qemu.org/index.php/Documentation/QMP#Trying_it
> > (now looking at it, it seems I'm mixing configs...)
> > 
> > $ cat qmp.conf
> > [chardev "qmp"]
> >   backend = "socket"
> >   path = "/tmp/qmp.sock"
> >   server = "on"
> >   wait = "off"
> > [mon "qmp"]
> >   mode = "control"
> >   chardev = "qmp"
> >   pretty = "on"
> > 
> 
> nice, pretty printing..., didn't expected that.

Oh, so *that*'s the root cause.  Thanks, I stared at this
configuration for a while and I couldn't see what could cause
extra newlines to appear in the output.  :)

[...]
> >>> I'm sure there is a nicer/more pythonic way to do this, but this works 
> >>> for me,
> >>> sorry :)
> >>
> >> It looks like there's no elegant solution for this:
> >> https://stackoverflow.com/a/21709058
> >>
> 
> Yep, that looks nicer, but even the original solution should
> not be that bad as it should be rarely used. What troubles me
> more is the possible infinite loop. Would you mind adding a
> timeout?

We already have a socket timeout, so I assume this is alrady
covered?

-- 
Eduardo