Event Callback function called twice for each event in libvirt

Issue

newVM is a function that creates new VM. For every guest VM the event callback function is being executed 2 times though the timer callback is executed correctly only one time at every interval. I am not able to figure out the reason for the same

eventLoopThread = None
libvirt.virEventRegisterDefaultImpl()

def virEventLoopNativeStart():
    global eventLoopThread
    eventLoopThread = threading.Thread(target=virEventLoopNativeRun, name="libvirtEventLoop")
    eventLoopThread.setDaemon(True)
    eventLoopThread.start()

def domainEventCallback(conn, dom, event, detail, opaque):
    print(" event callback %s %s %s", event, dom.name(), dom.state())

def domainTimeoutCalllback(timer, opaque):
    print(" Timeout ")

def virEventLoopNativeRun():
    while True:
        libvirt.virEventRunDefaultImpl()

virEventLoopNativeStart()
conn = libvirt.open('qemu:///system')
if conn == None:
    print('Failed to open connection to qemu:///system', file=sys.stderr)
    exit(1)
conn.domainEventRegister(domainEventCallback, None)
conn.setKeepAlive(5, 3)

def newVM(xmldata): #xmldata is XML to define guest machine
    try: 
        conn = libvirt.open('qemu:///system')
        if conn == None:
            print('Failed to open connection to qemu:///system', file=sys.stderr)
            exit(1)

        dom = conn.defineXML(xmldata)
        if dom == None:
            print('Failed to define a domain from an XML definition.', file=sys.stderr)
            exit(1)

        if dom.create() < 0:
            print('Can not boot guest domain.', file=sys.stderr)
            exit(1)
    
        libvirt.virEventAddTimeout(runTime, domainTimeoutCalllback, None)
    except libvirt.libvirtError:
        abort(404, "Libvirt could not be configured")

Solution

It is normal for the domain event callback to be invoked many times during startup - it will be given different arguments values each time.

Answered By - DanielB