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diff --git a/definate/yaml_validator.py b/definate/yaml_validator.py
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+#!/usr/bin/python
+#
+# Copyright 2012 Google Inc. All Rights Reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""Tools to allow the verification of the YAML configuration for Definate."""
+
+__author__ = 'msu@google.com (Martin Suess)'
+
+
+class Error(Exception):
+  """Base error class."""
+
+
+class DefinateConfigError(Error):
+  """Exception to use when Definate fails reading the configuration."""
+
+
+class YamlValidator(object):
+  """Class to verify the sanity of a YAML configuration."""
+
+  def CheckConfigurationItem(self, dictionary, item, typ=None):
+    """Checks for the presence of an item in a dictionary.
+
+    Args:
+      dictionary: Configuration part that should be checked.
+      item: Name of the key to check as string.
+      typ: Type of the value to check. Default is to not check the type.
+
+    Raises:
+      DefinateConfigError: The configuration is not sane.
+    """
+    if not dictionary or item not in dictionary:
+      raise DefinateConfigError('"%s" is not defined in config: %s'
+                                % (item, dictionary))
+    if typ and type(dictionary[item]) is not typ:
+      raise DefinateConfigError('Type of "%s" is %s, expected %s.' %
+                                (item, str(type(dictionary[item])), str(typ)))
+
+  def CheckConfiguration(self, config, structure, max_recursion_depth=30):
+    """Recursively checks the sanity and structure of the configuration.
+
+    This method checks the sanity of the configuration structure for Definate
+    and raises a DefinateConfigError if the configuration is not sane.
+
+    Args:
+      config: Dictionary generated from the YAML configuration file which should
+        be checked.
+      structure: Structure of the configuration against which should be checked.
+      max_recursion_depth: Defines the maximum amount of recursion cycles before
+        checking is aborted. Default is 30.
+
+    Raises:
+      DefinateConfigError: The configuration is not sane.
+    """
+    max_depth = max_recursion_depth - 1
+    if max_depth <= 0:
+      raise DefinateConfigError('Maximum recursion depth reached. Please check '
+                                'configuration manually.')
+    if type(structure) in [dict, list]:
+      for item in structure:
+        value = item
+        if type(structure) is dict:
+          value = structure[item]
+
+        self.CheckConfigurationItem(config, item, typ=type(value))
+        if type(value) is dict:
+          self.CheckConfiguration(config[item], value, max_depth)
+        elif type(value) is list:
+          for (i, list_value) in enumerate(value):
+            self.CheckConfiguration(config[item][i], list_value, max_depth)
+    elif type(structure) is type(config):
+      return
+    else:
+      raise DefinateConfigError('Type of "%s" is %s, expected %s.' % (
+          config, str(type(config)), str(structure)))