#!/usr/bin/python

"""
Picks a host to "create" (boot) a VM on, and does so.

Current load-balancing algorithm: wherever there's more free RAM.

TODO: use a lock to avoid creating the same VM twice in a race
"""

from invirt.remote import bcast
from subprocess import PIPE, Popen, call
import sys
import yaml

def choose_host():
    # Query each of the hosts.
    # XXX will the output of 'xm info' always be parseable YAML?
    results = bcast('info')
    return max((int(o['free_memory']), s) for (s, o) in results)[1]

def main(argv):
    if len(argv) < 2:
        print >> sys.stderr, "usage: sipb-xen-remote-create <machine> [<other args...>]"
        return 2
    machine_name = argv[1]
    args = argv[2:]

    p = Popen(['/usr/sbin/sipb-xen-remote-proxy-web', 'listvms'], stdout=PIPE)
    output = p.communicate()[0]
    if p.returncode != 0:
        raise RuntimeError("Command '%s' returned non-zero exit status %d"
                           % ('sipb-xen-remote-proxy-web', p.returncode)) 
    vms = yaml.load(output, yaml.CSafeLoader)

    if machine_name in vms:
        host = vms[machine_name]['host']
        print >> sys.stderr, ("machine '%s' is already running on host %s"
                              % (machine_name, host))
        return 1

    host = choose_host()
    print 'Creating on host %s...' % host
    sys.stdout.flush()
    return call(['remctl', host, 'remote', 'control',
                 machine_name, 'create'] + args)

if __name__ == '__main__':
    sys.exit(main(sys.argv))

# vim:et:sw=4:ts=4
