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[libvirt] serial console/events example script



Hi all,

A while back I wrote the attached code to demonstrate how to use
events and serial console to create a serial console that stays up
even when the VM is down.  Is it worth adding to the examples?  It
might need some work, as I am not terribly strong with Python.

Dave
#!/usr/bin/python -u
import sys, os, logging, libvirt, tty, termios, atexit

def reset_term():
    termios.tcsetattr(0, termios.TCSADRAIN, attrs)

def error_handler(unused, error):
    # The console stream errors on VM shutdown; we don't care
    if (error[0] == libvirt.VIR_ERR_RPC and
        error[1] == libvirt.VIR_FROM_STREAMS):
        return
    logging.warn(error)

class Console(object):
    def __init__(self, uri, uuid):
        self.uri = uri
        self.uuid = uuid
        self.connection = libvirt.open(uri)
        self.domain = self.connection.lookupByUUIDString(uuid)
        self.state = self.domain.state(0)
        self.connection.domainEventRegister(lifecycle_callback, self)
        self.stream = None
        self.run_console = True
        logging.info("%s initial state %d, reason %d",
                     self.uuid, self.state[0], self.state[1])

def check_console(console):
    if (console.state[0] == libvirt.VIR_DOMAIN_RUNNING or
        console.state[0] == libvirt.VIR_DOMAIN_PAUSED):
        if console.stream == None:
            console.stream = console.connection.newStream(libvirt.VIR_STREAM_NONBLOCK)
            console.domain.openConsole(None, console.stream, 0)
            console.stream.eventAddCallback(libvirt.VIR_STREAM_EVENT_READABLE, stream_callback, console)
    else:
        if console.stream:
            console.stream.eventRemoveCallback()
            console.stream = None

    return console.run_console

def stdin_callback(watch, fd, events, console):
    readbuf = os.read(fd, 1024)
    if readbuf.startswith(""):
        console.run_console = False
        return
    if console.stream:
        console.stream.send(readbuf)

def stream_callback(stream, events, console):
    try:
        received_data = console.stream.recv(1024)
    except:
        return
    os.write(0, received_data)

def lifecycle_callback (connection, domain, event, detail, console):
    console.state = console.domain.state(0)
    logging.info("%s transitioned to state %d, reason %d",
                 console.uuid, console.state[0], console.state[1])

# main
if len(sys.argv) != 3:
    print "Usage:", sys.argv[0], "URI UUID"
    print "for example:", sys.argv[0], "'qemu:///system' '32ad945f-7e78-c33a-e96d-39f25e025d81'"
    sys.exit(1)

uri = sys.argv[1]
uuid = sys.argv[2]

print "Escape character is ^]"
logging.basicConfig(filename='msg.log', level=logging.DEBUG)
logging.info("URI: %s", uri)
logging.info("UUID: %s", uuid)

libvirt.virEventRegisterDefaultImpl()
libvirt.registerErrorHandler(error_handler, None)

atexit.register(reset_term)
attrs = termios.tcgetattr(0)
tty.setraw(0)

console = Console(uri, uuid)
console.stdin_watch = libvirt.virEventAddHandle(0, libvirt.VIR_EVENT_HANDLE_READABLE, stdin_callback, console)

while check_console(console):
    libvirt.virEventRunDefaultImpl()

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