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Re: [libvirt-users] event handler



Michal Privoznik писал 2013-10-14 12:04:
On 14.10.2013 10:57, Alexandr wrote:
Michal Privoznik писал 2013-10-14 11:39:
On 14.10.2013 10:33, Alexandr wrote:
Michal Privoznik писал 2013-10-14 08:48:
On 14.10.2013 02:42, Alexandr wrote:
good day to all.
i still have not solved my problem with event handling.
currently i have following code


void libvirt_eventloop_thr_func()
{
    while(true) //TODO: stop somehow on exit
    {
        if(virEventRunDefaultImpl() < 0)
        {
            virErrorPtr err = virGetLastError();
fprintf(stderr, "Failed to run event loop: %s\n", err &&
err->message ? err->message : "Unknown error");
        }
    }
}



...

    virSetErrorFunc(NULL, libvirt_error_handler);
    libvirt_connection = virConnectOpen("qemu:///system");

Move this line ^^^ ...

    if (virEventRegisterDefaultImpl() < 0)
    {
        virErrorPtr err = virGetLastError();
        fprintf(stderr, "Failed to register event implementation:
%s\n",
err && err->message ? err->message: "Unknown error");
            return -1;
    }
    {
        int callback =
virConnectDomainEventRegisterAny(libvirt_connection, NULL,
VIR_DOMAIN_EVENT_ID_LIFECYCLE,
VIR_DOMAIN_EVENT_CALLBACK(domain_event_handler), NULL, NULL);
        if(callback == -1)
        {
std::cout<<"Error: failed to register domain event handle
callback\n";
            return -1;
        }
    }

    boost::thread(boost::bind(&libvirt_eventloop_thr_func));

... over here. The virConnectOpen detects if there's an even loop
registered. And in your case you don't have any registered when
calling it.

Michal

thank you very match, it now working as expected, but one thing are
missed from documentations, current api docs says what i do not need to
call virInitialize(), but if i call virEventRegisterDefaultImpl()
without calling virInitialize() programm crashing (i have not used
virInitialize() in my programm, just virConnectOpen() as docs said).
problem solved now.

From virInitialize documentation [1]:

"The only time it would be necessary to call virInitialize is if the
application did not invoke virConnectOpen as its first API call."

Which is your case. But if you believe this can be written better,
propose a patch and I'll review it.

Michal

1: http://libvirt.org/html/libvirt-libvirt.html#virInitialize

yes, i read this, but my first api call is virSetErrorFunc(), and this
api call working fine without virInitialize(), this create a little
confusion.

The fact that some functions *seem* to work well even without
virInitialize() called doesn't mean that you shouldn't call it. When I
started to write some programs involving libvirt I've looked into
virsh.c a lot and basically copied the main structure. virsh is
guaranteed to work and use the correct sequence of APIs. The other
option is to look at examples, e.g. event-test [2].

Michal

2:
http://libvirt.org/git/?p=libvirt.git;a=blob;f=examples/domain-events/events-c/event-test.c;h=52aa3d08d7326e422c12a8521717c3d55b2d8afd;hb=HEAD#l458

maybe write something like "virInitialize() must be first api call except situations when first call is virConnectOpen()" ?


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