def string_from_id(self, rc_id):
"""The reverse of the id_from_string() method. Given a supplied numeric
identifier for a resource class, we look up the corresponding string
representation, either in the list of standard resource classes or via
a DB lookup. The results of these DB lookups are cached since the
lookups are so frequent.
:param rc_id: The numeric representation of the resource class to look
up a string identifier for.
:returns: string identifier for the resource class, or None, if no such
resource class was found in the list of standard resource
classes or the resource_classes database table.
:raises `exception.ResourceClassNotFound` if rc_id cannot be found in
either the standard classes or the DB.
"""
# First check the fields.ResourceClass.STANDARD values
try:
return fields.ResourceClass.STANDARD[rc_id]
except IndexError:
pass
with lockutils.lock(_LOCKNAME):
if rc_id in self.str_cache:
return self.str_cache[rc_id]
# Otherwise, check the database table
_refresh_from_db(self.ctx, self)
if rc_id in self.str_cache:
return self.str_cache[rc_id]
raise exception.ResourceClassNotFound(resource_class=rc_id)
def id_from_string(self, rc_str):
"""Given a string representation of a resource class -- e.g. "DISK_GB"
or "IRON_SILVER" -- return the integer code for the resource class. For
standard resource classes, this integer code will match the list of
resource classes on the fields.ResourceClass field type. Other custom
resource classes will cause a DB lookup into the resource_classes
table, however the results of these DB lookups are cached since the
lookups are so frequent.
:param rc_str: The string representation of the resource class to look
up a numeric identifier for.
:returns integer identifier for the resource class, or None, if no such
resource class was found in the list of standard resource
classes or the resource_classes database table.
:raises `exception.ResourceClassNotFound` if rc_str cannot be found in
either the standard classes or the DB.
"""
# First check the standard resource classes
if rc_str in fields.ResourceClass.STANDARD:
return fields.ResourceClass.STANDARD.index(rc_str)
with lockutils.lock(_LOCKNAME):
if rc_str in self.id_cache:
return self.id_cache[rc_str]
# Otherwise, check the database table
_refresh_from_db(self.ctx, self)
if rc_str in self.id_cache:
return self.id_cache[rc_str]
raise exception.ResourceClassNotFound(resource_class=rc_str)
def all_from_string(self, rc_str):
"""Given a string representation of a resource class -- e.g. "DISK_GB"
or "CUSTOM_IRON_SILVER" -- return all the resource class info.
:param rc_str: The string representation of the resource class for
which to look up a resource_class.
:returns: dict representing the resource class fields, if the
resource class was found in the list of standard
resource classes or the resource_classes database table.
:raises: `exception.ResourceClassNotFound` if rc_str cannot be found in
either the standard classes or the DB.
"""
# First check the standard resource classes
if rc_str in fields.ResourceClass.STANDARD:
return {'id': fields.ResourceClass.STANDARD.index(rc_str),
'name': rc_str,
'updated_at': None,
'created_at': None}
with lockutils.lock(_LOCKNAME):
if rc_str in self.all_cache:
return self.all_cache[rc_str]
# Otherwise, check the database table
_refresh_from_db(self.ctx, self)
if rc_str in self.all_cache:
return self.all_cache[rc_str]
raise exception.ResourceClassNotFound(resource_class=rc_str)