Re: GSoC Intro - TUI interface for QMP

[John Snow]

On 6/8/21 11:01 AM, Markus Armbruster wrote:
> John Snow <jsnow@redhat.com> writes:
>
> [...]
>
> > A challenge will be where to pull the help text from. The QEMU server
> > is not capable (today) of sending help information over the QMP socket
> > itself.
> >
> > We will need to implement a QMP command inside of QEMU directly that
> > is capable of delivering this information to the client so that it can
> > render it.
> >
> > Since not all versions of QEMU will have this feature, the qmp-shell
> > will need to be able to gracefully deal with the lack of help text,
> > displaying an error indicating that this version of QEMU does not have
> > help information compiled into it.
>
> The doc text is bulky: my bld/docs/manual/interop/qemu-qmp-ref.html is
> 1.7 MiB and growing.  Less lavish markup results in smaller data.  We
> may want to store it compressed, or load it on demand.  We might even
> have to make it compile-time optional for some use cases.

ACK, understood.

raw QAPI directory, including only the json files, is "only" 551.3 kB.

I assume we can compile help text to something json (or json-like) and 
then compress it. Perhaps we could compile something like 
qapi-help-introspect.json.tgz and load it on-demand from the QEMU binary 
when help text is requested.

We could prototype under the experimental QMP command x-help, and limit 
it to sending help for just one command at a time to limit data transfer.

The client could cache the information. (Against what kind of an 
identifier? Can QEMU report some kind of token that uniquely identifies 
its binary or uniquely identifies the set of QAPI commands it supports?)

This has the potential to exceed our capacity this summer, but a 
prototype experiment might be helpful to inform future work anyway.

--js