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
  15 import re
  16
  17 # Matches on a string specifying memory size
  18 MEM = re.compile('^[1-9][0-9]*[MGTP]$')
  19
  20 # Multiplication factors to get Megabytes
  21 FACTORS = {
  22     "M": 1,
  23     "G": 1024,
  24     "T": 1024 * 1024,
  25     "P": 1024 * 1024 * 1024
  26 }
  27
  28 def parse(constraints):
  29     """
  30     Constraints must be expressed as a string containing only spaces
  31     and key value pairs joined by an '='.
  32
  33     """
  34     if constraints is None:
  35         return None
  36
  37     constraints = {
  38         normalize_key(k): normalize_value(v) for k, v in [
  39             s.split("=") for s in constraints.split(" ")]}
  40
  41     return constraints
  42
  43
  44 def normalize_key(key):
  45     key = key.strip()
  46
  47     key = key.replace("-", "_")  # Our _client lib wants "_" in place of "-"
  48     return key
  49
  50
  51 def normalize_value(value):
  52     value = value.strip()
  53
  54     if MEM.match(value):
  55         # Translate aliases to Megabytes. e.g. 1G = 10240
  56         return int(value[:-1]) * FACTORS[value[-1:]]
  57
  58     if "," in value:
  59         # Handle csv strings.
  60         values = value.split(",")
  61         values = [normalize_value(v) for v in values]
  62         return values
  63
  64     return value