[libvirt] [RFC PATCH] qemu: new API for tracking arbitrary monitor events

[Daniel P. Berrange]

On Thu, Dec 19, 2013 at 04:59:28PM +0100, Michal Privoznik wrote:
> On 19.12.2013 16:15, Eric Blake wrote:
> > Several times in the past, qemu has implemented a new event,
> > but libvirt has not yet caught up to reporting that event to
> > the user applications.  While it is possible to track libvirt
> > logs to see that an unknown event was received and ignored,
> > it would be nicer to copy what 'virsh qemu-monitor-command'
> > does, and expose this information to the end developer as
> > one of our unsupported qemu-specific commands.
> > 
> > If you find yourself needing to use this API for more than
> > just development purposes, please ask on the libvirt list
> > for a supported counterpart event to be added in libvirt.so.
> > 
> > While the supported virConnectDomainEventRegisterAny() API
> > takes an id which determines the signature of the callback,
> > this version takes a string filter and always uses the same
> > signature.  Furthermore, I chose to expose this as a new API
> > instead of trying to add a new eventID at the top level, in
> > part because the generic option lacks event name filtering,
> > and in part because the normal domain event namespace should
> > not be polluted by a qemu-only event.  I also added a flags
> > argument; unused for now, but we might decide to use it to
> > allow a user to request event names by glob or regex instead
> > of literal match.
> > 
> > * include/libvirt/libvirt-qemu.h
> > (virConnectDomainQemuMonitorEventCallback)
> > (virConnectDomainQemuMonitorEventRegister)
> > (virConnectDomainQemuMonitorEventDeregister): New prototypes.
> > * src/libvirt-qemu.c (virConnectDomainQemuMonitorEventRegister)
> > (virConnectDomainQemuMonitorEventDeregister): New functions.
> > * src/libvirt_qemu.syms (LIBVIRT_QEMU_1.2.1): Export them.
> > * src/driver.h (virDrvConnectDomainQemuMonitorEventRegister)
> > (virDrvConnectDomainQemuMonitorEventDeregister): New callbacks.
> > 
> > Signed-off-by: Eric Blake <eblake at redhat.com>
> > ---
> > 
> > Before I go and implement the guts of this new API, I first
> > wanted to get approval from the list that I'm on the right track.
> > 
> >  include/libvirt/libvirt-qemu.h |  31 ++++++++++-
> >  src/driver.h                   |  15 +++++
> >  src/libvirt-qemu.c             | 123 +++++++++++++++++++++++++++++++++++++++++
> >  src/libvirt_qemu.syms          |   6 ++
> >  4 files changed, 174 insertions(+), 1 deletion(-)
> > 
> > diff --git a/include/libvirt/libvirt-qemu.h b/include/libvirt/libvirt-qemu.h
> > index 3e79a8c..5403093 100644
> > --- a/include/libvirt/libvirt-qemu.h
> > +++ b/include/libvirt/libvirt-qemu.h
> > @@ -4,7 +4,7 @@
> >   * Description: Provides the interfaces of the libvirt library to handle
> >   *              qemu specific methods
> >   *
> > - * Copyright (C) 2010, 2012 Red Hat, Inc.
> > + * Copyright (C) 2010, 2012-2013 Red Hat, Inc.
> >   *
> >   * This library is free software; you can redistribute it and/or
> >   * modify it under the terms of the GNU Lesser General Public
> > @@ -54,6 +54,35 @@ typedef enum {
> >  char *virDomainQemuAgentCommand(virDomainPtr domain, const char *cmd,
> >                                  int timeout, unsigned int flags);
> > 
> > +/**
> > + * virConnectDomainQemuMonitorEventCallback:
> > + * @conn: the connection pointer
> > + * @dom: the domain pointer
> > + * @event: the name of the event
> > + * @details: the JSON details of the event
> > + * @opaque: application specified data
> > + *
> > + * The callback signature to use when registering for a qemu monitor
> > + * event with virConnectDomainQemuMonitorEventRegister().
> > + */
> > +typedef void (*virConnectDomainQemuMonitorEventCallback)(virConnectPtr conn,
> > +                                                         virDomainPtr dom,
> > +                                                         const char *event,
> > +                                                         const char *details,
> > +                                                         void *opaque);
> 
> 
> So for instance on this event:
> 2013-12-19 15:55:05.575+0000: 18630: debug : qemuMonitorJSONIOProcessLine:172 : QEMU_MONITOR_RECV_EVENT: mon=0x7f8c80008910 event={"timestamp": {"seconds": 1387468505, "microseconds": 574652}, "event": "SPICE_INITIALIZED", "data": {"server": {"auth": "none", "port": "5900", "family": "ipv4", "host": "127.0.0.1"}, "client": {"port": "39285", "family": "ipv4", "channel-type": 4, "connection-id": 375558326, "host": "127.0.0.1", "channel-id": 0, "tls": false}}}
> 
> the callback will be invoked with:
> event="SPICE_INITIALIZED"
> details="{"server": {"auth": ....}}"?
> 
> After all, I don't think we should do anything clever about it. Apps dealing with monitor/agent code (e.g. command passthru) are dealing with JSON anyway.

Agreed, just sending out the JSON 'data' block as-is seems fine to me.

Daniel
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