Re: [Libguestfs] Libguestfs gobject bindings
On Fri, Jan 13, 2012 at 12:28:50PM +0000, Daniel P. Berrange wrote:
GIO provides all the infrastructure you need to do this, via the
GSimpleAsyncResult object, and its g_simple_async_result_run_in_thread
method.
So it does; we could use that. Might want to only offer this for
functions that are truly long-running. I doubt anyone will be happy
with launching threads to handle guestfs_set_verbose et al.
We could flag long-running functions. cf. 'Progress' flag in
generator/generator_actions.ml -- which brings me on to the subject of
if we need to do anything special for long-running functions that
generate progress messages?
And second question: event API? error handling in the GObject API
(does GObject have any concept of exceptions)?
> virt-manager & guestfs-browser use libguestfs by creating a
separate
> thread and sending it instructions. It's not that hard to implement,
> so for the moment I'd say forget about providing async functions.
GTK doesn't play nice with threads though, so you have to deal with
message passing back & forth between threads. With the way the GIO
framework works, threads are always hidden, so your app code just
deals with signals which always occurs in the main thread & can thus
use GTK safely.
Right ... virt-manager & guestfs-browser take care of this. I still
think it's not too hard, but I have no objection to offering people a
choice of methods (using g_simple_async_result_run_in_thread).
> > The only issue would be if you wanted to add in
'GCancellable' to
> > the existing blocking APIs. I imagine there's no easy way to allow
> > cancellation of API calls at the libguestfs level, so it is probably
> > not worth it.
>
> Actually, this is possible for some (by no means all) calls:
> http://libguestfs.org/guestfs.3.html#cancelling_long_transfers
> You can also kill the qemu subprocess, although you risk losing any
> state you were writing to the disk.
Ok, then for any of APIs which support this cancellation mode, I'd
strongly suggest adding the GCancellable * argument to the existing
method definitions.
Yes. We should add a note to the generator flags for functions that
do support this. Currently it's just FileIn/FileOut functions, but it
could be worth having a flag in case we extend this in future.
Rich.
--
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