"""Logical Unit base class.
Subclasses must follow these rules:
- - implement CheckPrereq which also fills in the opcode instance
- with all the fields (even if as None)
+ - implement ExpandNames
+ - implement CheckPrereq
- implement Exec
- implement BuildHooksEnv
- redefine HPATH and HTYPE
self.cfg = context.cfg
self.sstore = sstore
self.context = context
+ self.needed_locks = None
self.__ssh = None
for attr_name in self._OP_REQP:
ssh = property(fget=__GetSSH)
+ def ExpandNames(self):
+ """Expand names for this LU.
+
+ This method is called before starting to execute the opcode, and it should
+ update all the parameters of the opcode to their canonical form (e.g. a
+ short node name must be fully expanded after this method has successfully
+ completed). This way locking, hooks, logging, ecc. can work correctly.
+
+ LUs which implement this method must also populate the self.needed_locks
+ member, as a dict with lock levels as keys, and a list of needed lock names
+ as values. Rules:
+ - Use an empty dict if you don't need any lock
+ - If you don't need any lock at a particular level omit that level
+ - Don't put anything for the BGL level
+ - If you want all locks at a level use None as a value
+ (this reflects what LockSet does, and will be replaced before
+ CheckPrereq with the full list of nodes that have been locked)
+
+ Examples:
+ # Acquire all nodes and one instance
+ self.needed_locks = {
+ locking.LEVEL_NODE: None,
+ locking.LEVEL_INSTANCES: ['instance1.example.tld'],
+ }
+ # Acquire just two nodes
+ self.needed_locks = {
+ locking.LEVEL_NODE: ['node1.example.tld', 'node2.example.tld'],
+ }
+ # Acquire no locks
+ self.needed_locks = {} # No, you can't leave it to the default value None
+
+ """
+ # The implementation of this method is mandatory only if the new LU is
+ # concurrent, so that old LUs don't need to be changed all at the same
+ # time.
+ if self.REQ_BGL:
+ self.needed_locks = {} # Exclusive LUs don't need locks.
+ else:
+ raise NotImplementedError
+
def CheckPrereq(self):
"""Check prerequisites for this LU.
not fulfilled. Its return value is ignored.
This method should also update all the parameters of the opcode to
- their canonical form; e.g. a short node name must be fully
- expanded after this method has successfully completed (so that
- hooks, logging, etc. work correctly).
+ their canonical form if it hasn't been done by ExpandNames before.
"""
raise NotImplementedError