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 FACTORS = {
  25     "M": 1,
  26     "G": 1024,
  27     "T": 1024 * 1024,
  28     "P": 1024 * 1024 * 1024
  29 }
  30
  31 SNAKE1 = re.compile(r'(.)([A-Z][a-z]+)')
  32 SNAKE2 = re.compile('([a-z0-9])([A-Z])')
  33
  34 def parse(constraints):
  35     """
  36     Constraints must be expressed as a string containing only spaces
  37     and key value pairs joined by an '='.
  38
  39     """
  40     if constraints is None:
  41         return None
  42
  43     if constraints == "":
  44         return None
  45
  46     if type(constraints) is dict:
  47         # Fowards compatibilty: already parsed
  48         return constraints
  49
  50     constraints = {
  51         normalize_key(k): normalize_value(v) for k, v in [
  52             s.split("=") for s in constraints.split(" ")]}
  53
  54     return constraints
  55
  56
  57 def normalize_key(key):
  58     key = key.strip()
  59
  60     key = key.replace("-", "_")  # Our _client lib wants "_" in place of "-"
  61
  62     # Convert camelCase to snake_case
  63     key = SNAKE1.sub(r'\1_\2', key)
  64     key = SNAKE2.sub(r'\1_\2', key).lower()
  65
  66     return key
  67
  68
  69 def normalize_value(value):
  70     value = value.strip()
  71
  72     if MEM.match(value):
  73         # Translate aliases to Megabytes. e.g. 1G = 10240
  74         return int(value[:-1]) * FACTORS[value[-1:]]
  75
  76     if "," in value:
  77         # Handle csv strings.
  78         values = value.split(",")
  79         values = [normalize_value(v) for v in values]
  80         return values
  81
  82     if value.isdigit():
  83         return int(value)
  84
  85     return value