[libvirt-users] Callback re-registration after libvirtd restart

[Daniel Kučera]

Hi Daniel,

I tried that but it doesn't work:

func libvirt_close_callback(conn *libvirt.Connect, reason
libvirt.ConnectCloseReason){
    log.Printf("close callback: %+v", reason)
}

func event_listen() {
    log.Printf("event_listen %s", conf.Libvirt.LocalUrl)
    hv, err := libvirt.NewConnect(conf.Libvirt.LocalUrl)

    err = hv.RegisterCloseCallback(libvirt_close_callback)
    if err != nil {
        log.Printf("unable to register close callback")
        return
    }
...

The callback fires only when I kill my app,

^CGot signal:%!(EXTRA syscall.Signal=interrupt)
close callback: 0

but not when I restart libvirtd. I tried using both local and remote
connect URIs: qemu+ssh://10.130.16.101/system, qemu+ssh://localhost/system,
qemu+ssh:///system

Thanks.

D.


2017-05-17 15:24 GMT+02:00 Daniel P. Berrange <berrange at redhat.com>:

> On Wed, May 17, 2017 at 03:08:23PM +0200, Daniel Kučera wrote:
> > Hi all,
> >
> > I'm using libvirt-go and I following code to listen for lifecycle events:
> >
> > func event_listen() {
> >     log.Printf("event_listen %s", conf.Libvirt.LocalUrl)
> >     hv, err := libvirt.NewConnect(conf.Libvirt.LocalUrl)
> >
> >     lifecycleCallback := func(c *libvirt.Connect, d *libvirt.Domain,
> event
> > *libvirt.DomainEventLifecycle) {
> >         event_message(c, d, "lifecycle", event)
> >     }
> >
> >     _, err = hv.DomainEventLifecycleRegister(nil, lifecycleCallback)
> >     if err != nil {
> >         log.Printf("unable to register event callback")
> >         return
> >     }
> >
> >     log.Printf("Libvirt event listener started")
> >
> >     go func() {
> >         for err == nil {
> >             err = libvirt.EventRunDefaultImpl()
> >             log.Printf("EventRunDefaultImpl err: %+v", err)
> >         }
> >         time.Sleep(time.Second)
> >         event_listen()
> >     }()
> >
> > }
> >
> > It works ok until I restart libvirtd (service libvirtd restart). After
> > that, the inner go func waits some time and continues without error. But
> > the callback is not working anymore.
> >
> > My question is, how can I detect hv reconnect (I guess it's happening in
> > background) so I know when to reinitialize callbacks?
>
> There is a separate event you can listen to that notifies when the
> connection
> is closed. See the RegisterCloseCallback() method on the Connect object.
>
> Basically register a callback there, and when it fires, unregister your
> existing domain event callbacks, and close your existing Connect object
> handle. Then fire a goroutine that loops once every few seconds trying
> to open a new Connect object, and when that succeeds register new
> domain event callbacks.
>
> Regards,
> Daniel
> --
> |: https://berrange.com      -o-    https://www.flickr.com/photos/
> dberrange :|
> |: https://libvirt.org         -o-
> https://fstop138.berrange.com :|
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> dberrange :|
>
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