ganeti.cmdlib.tags.TagsLU

Check prerequisites.

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, etc. 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 (note that in this case DeclareLocks won't be called at all for that level)
• if you need locks at a level, but you can't calculate it in this function, initialise that level with an empty list and do further processing in LogicalUnit.DeclareLocks (see that function's docstring)
• don't put anything for the BGL level
• if you want all locks at a level use locking.ALL_SET as a value

If you need to share locks (rather than acquire them exclusively) at one level you can modify self.share_locks, setting a true value (usually 1) for that level. By default locks are not shared.

This function can also define a list of tasklets, which then will be executed in order instead of the usual LU-level CheckPrereq and Exec functions, if those are not defined by the LU.

Examples:

  # Acquire all nodes and one instance
  self.needed_locks = {
    locking.LEVEL_NODE: locking.ALL_SET,
    locking.LEVEL_INSTANCE: ['instance1.example.com'],
  }
  # Acquire just two nodes
  self.needed_locks = {
    locking.LEVEL_NODE: ['node1-uuid', 'node2-uuid'],
  }
  # Acquire no locks
  self.needed_locks = {} # No, you can't leave it to the default value None