# Simple wrapper arround cgroups so we don't have to worry the type of
# virtualization the sliver runs on (lxc, qemu/kvm, etc.) managed by libvirt
#
# Xavi Leon <xleon@ac.upc.edu>

import os
import pyinotify
import logger

# Base dir for libvirt
BASE_DIR = '/cgroup/libvirt/'
VIRT_TECHS = ['lxc']

# Global cgroup mapping. 
CGROUPS = dict()

class CgroupWatch(pyinotify.ProcessEvent):

    def process_IN_CREATE(self, event):
	path = os.path.join(event.path, event.name)
	CGROUPS[event.name] = path
	logger.verbose("Cgroup Notify: Created cgroup %s on %s" % \
			(event.name, event.path))
        
    def process_IN_DELETE(self, event):
        try:
	    del CGROUPS[event.name]
        except:
            logger.verbose("Cgroup Notify: Cgroup %s does not exist, continuing..."%event.name)
	logger.verbose("Cgroup Notify: Deleted cgroup %s on %s" % \
			(event.name, event.path))


logger.verbose("Cgroups: Recognizing already existing cgroups...")
for virt in VIRT_TECHS:
    filenames = os.listdir(os.path.join(BASE_DIR, virt))
    for filename in filenames:
	path = os.path.join(BASE_DIR, virt, filename)
	if os.path.isdir(path):
	    CGROUPS[filename] = path

logger.verbose("Cgroups: Initializing watchers...")
wm = pyinotify.WatchManager()
notifier = pyinotify.ThreadedNotifier(wm, CgroupWatch())
for virt in VIRT_TECHS:
	wdd = wm.add_watch(os.path.join(BASE_DIR, virt),
			   pyinotify.IN_DELETE | pyinotify.IN_CREATE,
			   rec=False)
notifier.daemon = True
notifier.start()

def get_cgroup_path(name):
    """ Returns the base path for the cgroup with a specific name """
    assert CGROUPS.has_key(name), \
	    "No sliver %s managed by libvirt through cgroup!" % name
    return CGROUPS[name]

def get_base_path():
    return BASE_DIR

def get_cgroups():
    """ Returns the list of cgroups active at this moment on the node """
    return CGROUPS.keys()

def write(name, key, value):
    """ Writes a value to the file key with the cgroup with name """
    base_path = get_cgroup_path(name)
    with open(os.path.join(base_path, key), 'w') as f:
        print >>f, value

def append(name, key, value):
    """ Appends a value to the file key with the cgroup with name """
    base_path = get_cgroup_path(name)
    with open(os.path.join(base_path, key), 'a') as f:
        print >>f, value