Re: [PATCH 0/5] qmp-shell modifications for non-interactive use

[Daniel P . Berrangé]

On Wed, Feb 23, 2022 at 10:57:29AM +0100, Damien Hedde wrote:
> 
> 
> On 2/22/22 11:31, Daniel P. Berrangé wrote:
> > On Tue, Feb 22, 2022 at 10:38:09AM +0100, Damien Hedde wrote:
> > > 
> > > 
> > > Here I just wanted to propose a simple way to just send a
> > > bunch of commands from a source file and stop if something unexpected
> > > happens.
> > > Only goal is to be able to share a file on the ml and allow people to
> > > reproduce easily.
> > > We can already redirect the input, but it is almost impossible to see
> > > if something failed.
> > 
> > Yes, I see what you mean. So the problem with using 'socat' or similar
> > is that we fill the input with commands and response appear asynchronously,
> > so we can't match them up easily. This is actually a problem seen in the
> > block I/O tests which just send QMP stuff in a batch.
> > 
> > While you could do this by invoking socat once for each command, that
> > gets silly with the repeated QMP handshake for each command.
> > 
> > The thing about using qmp-shell is that it does a bunch of extra stuff
> > targetted at humans on top, and history tells us it isn't a good idea
> > to mix stuff for humans and machines in the same tool/interface.
> > 
> > How about instead creating a separate 'qmp-send' command that is not
> > much more than a "QMP-aware socat".  By which I mean, it just reads
> > raw QMP commands from stdin, sends each one to the server, but
> > crucially waits for a reply after sending each, and stops on first
> > error reponse.
> 
> By 'qmp-send' command, you mean another script in scripts/qmp ?
> Yes

Yep.

> If we go for another script, I would rather do one with wrap
> feature (like your series) to start qemu as well.

Sure, that would certainly make sense.  I actually wanted to add
the wrap feature directly into the existing qmp-shell, but it was
not viable while maintaining back compat. With a new qmp-send
command you can easily make "wrap mode" supported from the start.

Regards,
Daniel
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