Extract the config provider into its own sub-module

util/config/provider/__init__.py

@@ -0,0 +1,10 @@
+from util.config.provider.fileprovider import FileConfigProvider
+from util.config.provider.testprovider import TestConfigProvider
+
+def get_config_provider(config_volume, yaml_filename, py_filename, testing=False):
+  """ Loads and returns the config provider for the current environment. """
+  if testing:
+    return TestConfigProvider()
+
+  return FileConfigProvider(config_volume, yaml_filename, py_filename)
+

util/config/provider/baseprovider.py

@@ -0,0 +1,77 @@
+import yaml
+import logging
+
+logger = logging.getLogger(__name__)
+
+class CannotWriteConfigException(Exception):
+  """ Exception raised when the config cannot be written. """
+  pass
+
+def import_yaml(config_obj, config_file):
+  with open(config_file) as f:
+    c = yaml.safe_load(f)
+    if not c:
+      logger.debug('Empty YAML config file')
+      return
+
+    if isinstance(c, str):
+      raise Exception('Invalid YAML config file: ' + str(c))
+
+    for key in c.iterkeys():
+      if key.isupper():
+        config_obj[key] = c[key]
+
+  return config_obj
+
+
+def export_yaml(config_obj, config_file):
+  try:
+    with open(config_file, 'w') as f:
+      f.write(yaml.safe_dump(config_obj, encoding='utf-8', allow_unicode=True))
+  except IOError as ioe:
+    raise CannotWriteConfigException(str(ioe))
+
+
+class BaseProvider(object):
+  """ A configuration provider helps to load, save, and handle config override in the application.
+  """
+
+  def update_app_config(self, app_config):
+    """ Updates the given application config object with the loaded override config. """
+    raise NotImplementedError
+
+  def get_yaml(self):
+    """ Returns the contents of the YAML config override file, or None if none. """
+    raise NotImplementedError
+
+  def save_yaml(self, config_object):
+    """ Updates the contents of the YAML config override file to those given. """
+    raise NotImplementedError
+
+  def yaml_exists(self):
+    """ Returns true if a YAML config override file exists in the config volume. """
+    raise NotImplementedError
+
+  def volume_exists(self):
+    """ Returns whether the config override volume exists. """
+    raise NotImplementedError
+
+  def volume_file_exists(self, filename):
+    """ Returns whether the file with the given name exists under the config override volume. """
+    raise NotImplementedError
+
+  def get_volume_file(self, filename, mode='r'):
+    """ Returns a Python file referring to the given name under the config override volumne. """
+    raise NotImplementedError
+
+  def save_volume_file(self, filename, flask_file):
+    """ Saves the given flask file to the config override volume, with the given
+        filename.
+    """
+    raise NotImplementedError
+
+  def requires_restart(self, app_config):
+    """ If true, the configuration loaded into memory for the app does not match that on disk,
+        indicating that this container requires a restart.
+    """
+    raise NotImplementedError

util/config/provider/fileprovider.py

@@ -0,0 +1,66 @@
+import os
+import logging
+
+from util.config.provider.baseprovider import (BaseProvider, import_yaml, export_yaml,
+                                               CannotWriteConfigException)
+
+logger = logging.getLogger(__name__)
+
+class FileConfigProvider(BaseProvider):
+  """ Implementation of the config provider that reads the data from the file system. """
+  def __init__(self, config_volume, yaml_filename, py_filename):
+    self.config_volume = config_volume
+    self.yaml_filename = yaml_filename
+    self.py_filename = py_filename
+
+    self.yaml_path = os.path.join(config_volume, yaml_filename)
+    self.py_path = os.path.join(config_volume, py_filename)
+
+  def update_app_config(self, app_config):
+    if os.path.exists(self.py_path):
+      logger.debug('Applying config file: %s', self.py_path)
+      app_config.from_pyfile(self.py_path)
+
+    if os.path.exists(self.yaml_path):
+      logger.debug('Applying config file: %s', self.yaml_path)
+      import_yaml(app_config, self.yaml_path)
+
+  def get_yaml(self):
+    if not os.path.exists(self.yaml_path):
+      return None
+
+    config_obj = {}
+    import_yaml(config_obj, self.yaml_path)
+    return config_obj
+
+  def save_yaml(self, config_obj):
+    export_yaml(config_obj, self.yaml_path)
+
+  def yaml_exists(self):
+    return self.volume_file_exists(self.yaml_filename)
+
+  def volume_exists(self):
+    return os.path.exists(self.config_volume)
+
+  def volume_file_exists(self, filename):
+    return os.path.exists(os.path.join(self.config_volume, filename))
+
+  def get_volume_file(self, filename, mode='r'):
+    return open(os.path.join(self.config_volume, filename), mode)
+
+  def save_volume_file(self, filename, flask_file):
+    try:
+      flask_file.save(os.path.join(self.config_volume, filename))
+    except IOError as ioe:
+      raise CannotWriteConfigException(str(ioe))
+
+  def requires_restart(self, app_config):
+    file_config = self.get_yaml()
+    if not file_config:
+      return False
+
+    for key in file_config:
+      if app_config.get(key) != file_config[key]:
+        return True
+
+    return False

util/config/provider/testprovider.py

@@ -0,0 +1,45 @@
+import json
+from StringIO import StringIO
+
+from util.config.provider.baseprovider import BaseProvider
+
+class TestConfigProvider(BaseProvider):
+  """ Implementation of the config provider for testing. Everything is kept in-memory instead on
+      the real file system. """
+  def __init__(self):
+    self.files = {}
+    self._config = None
+
+  def update_app_config(self, app_config):
+    self._config = app_config
+
+  def get_yaml(self):
+    if not 'config.yaml' in self.files:
+      return None
+
+    return json.loads(self.files.get('config.yaml', '{}'))
+
+  def save_yaml(self, config_obj):
+    self.files['config.yaml'] = json.dumps(config_obj)
+
+  def yaml_exists(self):
+    return 'config.yaml' in self.files
+
+  def volume_exists(self):
+    return True
+
+  def volume_file_exists(self, filename):
+    return filename in self.files
+
+  def save_volume_file(self, filename, flask_file):
+    self.files[filename] = ''
+
+  def get_volume_file(self, filename, mode='r'):
+    return StringIO(self.files[filename])
+
+  def requires_restart(self, app_config):
+    return False
+
+  def reset_for_test(self):
+    self._config['SUPER_USERS'] = ['devtable']
+    self.files = {}