[libvirt-users] event handler

[Alexandr]

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()" ?