Self parse user data

stacker/blueprints/base.py

@@ -1,11 +1,13 @@
 import copy
 import hashlib
 import logging
+from string import Template as StringTemplate
+from stacker.util import read_value_from_path
 
 from troposphere import (
     Parameter,
     Ref,
-    Template,
+    Template
 )
 
 from ..exceptions import (
@@ -220,7 +222,48 @@ def resolve_variable(var_name, var_def, provided_variable, blueprint_name):
     return value
 
 
+def parse_user_data(variables, raw_user_data, blueprint_name):
+    """Translate a userdata file to into the file contents.
+
+        It supports referencing template variables to create userdata
+        that's supplemented with information from the data, as commonly
+        required when creating EC2 userdata files. Automatically, encodes
+        the data file to base64 after it is processed.
+
+        Args:
+            raw_user_data (str): the user data with the cloud-init info
+
+        Returns:
+            str: The parsed user data, with all the variables values and
+                 refs replaced with their resolved values.
+
+        Raises:
+            MissingVariable: Raised when a variable is in the user_data that
+                             is not given in the blueprint
+
+        """
+    variable_values = {}
+
+    for key in variables.keys():
+        if type(variables[key]) is CFNParameter:
+            variable_values[key] = variables[key].to_parameter_value()
+        else:
+            variable_values[key] = variables[key]
+
+    template = StringTemplate(raw_user_data)
+
+    res = ""
+
+    try:
+        res = template.substitute(variable_values)
+    except Exception as e:
+        raise MissingVariable(blueprint_name, e)
+
+    return res
+
+
 class Blueprint(object):
+
     """Base implementation for rendering a troposphere template.
 
     Args:
@@ -402,6 +445,23 @@ def render_template(self):
         version = hashlib.md5(rendered).hexdigest()[:8]
         return (version, rendered)
 
+    def read_user_data(self, user_data_path):
+        """Reads and parses a user_data file.
+
+        Args:
+            user_data_path (str):
+                path to the userdata file
+
+        Returns:
+            str: the parsed user data file
+
+        """
+        raw_user_data = read_value_from_path(user_data_path)
+
+        variables = self.get_variables()
+
+        return parse_user_data(variables, raw_user_data, self.name)
+
     @property
     def rendered(self):
         if not self._rendered:

stacker/tests/blueprints/test_base.py

@@ -1,10 +1,11 @@
 import unittest
+from mock import patch
 
 from mock import MagicMock
 from troposphere import (
     Base64,
     Ref,
-    s3,
+    s3
 )
 
 from stacker.blueprints.base import (
@@ -14,6 +15,7 @@
     validate_allowed_values,
     validate_variable_type,
     resolve_variable,
+    parse_user_data
 )
 from stacker.blueprints.variables.types import (
     CFNNumber,
@@ -44,6 +46,7 @@ def mock_lookup_handler(value, provider=None, context=None, fqn=False,
 
 
 class TestBuildParameter(unittest.TestCase):
+
     def test_base_parameter(self):
         p = build_parameter("BasicParam", {"type": "String"})
         p.validate()
@@ -72,6 +75,7 @@ class TestBlueprint(Blueprint):
             }
 
         class TestBlueprintSublcass(TestBlueprint):
+
             def defined_variables(self):
                 variables = super(TestBlueprintSublcass,
                                   self).defined_variables()
@@ -528,3 +532,38 @@ class TestBlueprint(Blueprint):
 
         with self.assertRaises(AttributeError):
             TestBlueprint(name="test", context=MagicMock())
+
+    def test_parse_user_data(self):
+        expected = 'name: tom, last: taubkin and $'
+        variables = {
+            'name': 'tom',
+            'last': 'taubkin'
+        }
+
+        raw_user_data = 'name: ${name}, last: $last and $$'
+        blueprint_name = 'test'
+        res = parse_user_data(variables, raw_user_data, blueprint_name)
+        self.assertEqual(res, expected)
+
+    def test_parse_user_data_fails(self):
+        variables = {
+            'name': 'tom',
+        }
+
+        raw_user_data = 'name: ${name}, last: $last and $$'
+        blueprint_name = 'test'
+        with self.assertRaises(MissingVariable):
+            parse_user_data(variables, raw_user_data, blueprint_name)
+
+    @patch('stacker.blueprints.base.read_value_from_path',
+           return_value='contents')
+    @patch('stacker.blueprints.base.parse_user_data')
+    def test_read_user_data(self, parse_mock, file_mock):
+        class TestBlueprint(Blueprint):
+            VARIABLES = {}
+
+        blueprint = TestBlueprint(name="blueprint_name", context=MagicMock())
+        blueprint.resolve_variables({})
+        blueprint.read_user_data('file://test.txt')
+        file_mock.assert_called_with('file://test.txt')
+        parse_mock.assert_called_with({}, 'contents', 'blueprint_name')