modules/libjuju/juju/constraints.py

   1 #
   2 # Module that parses constraints
   3 #
   4 # The current version of juju core expects the client to take
   5 # constraints given in the form "mem=10G foo=bar" and parse them into
   6 # json that looks like {"mem": 10240, "foo": "bar"}. This module helps us
   7 # accomplish that task.
   8 #
   9 # We do not attempt to duplicate the checking done in
  10 # client/_client.py:Value here. That class will verify that the
  11 # constraints keys are valid, and that we can successfully dump the
  12 # constraints dict to json.
  13 #
  14 # Once https://bugs.launchpad.net/juju/+bug/1645402 is addressed, this
  15 # module should be deprecated.
  16 #
  17
  18 import re
  19
  20 # Matches on a string specifying memory size
  21 MEM = re.compile('^[1-9][0-9]*[MGTP]$')
  22
  23 # Multiplication factors to get Megabytes
  24 # https://github.com/juju/juju/blob/master/constraints/constraints.go#L666
  25 FACTORS = {
  26     "M": 1,
  27     "G": 1024,
  28     "T": 1024 * 1024,
  29     "P": 1024 * 1024 * 1024
  30 }
  31
  32 LIST_KEYS = {'tags', 'spaces'}
  33
  34 SNAKE1 = re.compile(r'(.)([A-Z][a-z]+)')
  35 SNAKE2 = re.compile('([a-z0-9])([A-Z])')
  36
  37
  38 def parse(constraints):
  39     """
  40     Constraints must be expressed as a string containing only spaces
  41     and key value pairs joined by an '='.
  42
  43     """
  44     if not constraints:
  45         return None
  46
  47     if type(constraints) is dict:
  48         # Fowards compatibilty: already parsed
  49         return constraints
  50
  51     constraints = {
  52         normalize_key(k): (
  53             normalize_list_value(v) if k in LIST_KEYS else
  54             normalize_value(v)
  55         ) for k, v in [s.split("=") for s in constraints.split(" ")]}
  56
  57     return constraints
  58
  59
  60 def normalize_key(key):
  61     key = key.strip()
  62
  63     key = key.replace("-", "_")  # Our _client lib wants "_" in place of "-"
  64
  65     # Convert camelCase to snake_case
  66     key = SNAKE1.sub(r'\1_\2', key)
  67     key = SNAKE2.sub(r'\1_\2', key).lower()
  68
  69     return key
  70
  71
  72 def normalize_value(value):
  73     value = value.strip()
  74
  75     if MEM.match(value):
  76         # Translate aliases to Megabytes. e.g. 1G = 10240
  77         return int(value[:-1]) * FACTORS[value[-1:]]
  78
  79     if value.isdigit():
  80         return int(value)
  81
  82     return value
  83
  84
  85 def normalize_list_value(value):
  86     values = value.strip().split(',')
  87     return [normalize_value(value) for value in values]