def getval(h, path):
""" Obtain data from a xenstore path.
h : transaction handle
path : xenstore-path to node
Returns data read from xenstore-tree.
Raises xen.lowlevel.xs.Error on error.
"""
DEBUG("Read xenstore value for key: %s" % path, "snapwatchd/xslib")
return h.read('', path)
def unwatch(h, path):
""" Wrapper to unwatch a xenstore-node
h : transaction handle
path : xenstore-path to unwatch
Returns None on success
Raises xen.lowlevel.xs.Error on error
"""
DEBUG("Unwatch %s from xenstore" % path, "snapwatchd/xslib")
return h.unwatch(path, '')
def set_watch(h, path):
""" Wrapper to set watch on xenstore-path.
h : transaction handle
path : xenstore-path to set watch on
Returns None on success
Raises xen.lowlevel.xs.Error on error
"""
DEBUG("Setting watch on %s in xenstore" % path, "snapwatchd/xslib")
return h.watch(path, '')
def dirlist(h, base):
""" Get a directory listing of the xenstore nodes as specified by the `base` argument.
h : transaction handle
base : path to list
Returns : list of sub-directory nodes
None if key doesn't exist
Raises xen.lowlevel.xs.Error on error.
"""
DEBUG("Get directory listing for xenstore-path: %s" % base,
"snapwatchd/xslib")
return h.ls('', base)
def setval(h, path, value):
""" Set data at a specific xenstore node.
h : transaction handle
path : xenstore-path to write into
value : value to be written into xenstore-node
Returns:
True on success
False on failure/exception
"""
try:
DEBUG("Set value: %s at xenstore-path %s" % (value, path),
"snapwatchd/xslib")
if h.write('', path, value) == None:
return True
else:
return False
except:
DEBUG(
"Unable to write value[%s] at xenstore-path [%s]" % (value, path),
"snapwatchd/xslib")
return False
def xs_exists(h, path):
""" Check if a specific xenstore-node exists.
h : transaction handle
path : xenstore-path
Returns:
True if path exists
False if path doesn't exist
"""
try:
DEBUG("Checking if xenstore-path: [%s] exists" % path,
"snapwatchd/xslib")
if getval(h, path) != None:
return True
else:
return False
except:
return False
def remove_xs_entry(h, dom_uuid, dom_path):
""" Remove node from vss-xenstore-tree
h : transaction handle
dom_uuid : UUID of domain
dom_path : domain path on xenstore
XENSTORE PATH: /vss/dom_uuid/dom_path
Returns None on success
Raises exception on failure
"""
path = "/vss/%s/%s" % (dom_uuid, dom_path)
DEBUG("Removing xenstore-entry [%s] from xenstore-tree" % path,
"snapwatchd/xslib")
if xs_exists(h, path):
try:
h.rm('', path)
except Exception, e:
raise Exception("xenstore-node %s remove failed, err: %s" %
(path, e))
def get_xs_handle():
""" Obtain a handle to interact with xenstore via the xen-lowlevel library. """
DEBUG("Get a new xenstore handle.", "snapwatchd/xslib")
return xen.lowlevel.xs.xs()