Add support for parsing YAML override config, in addition to Python config

app.py

@@ -1,8 +1,9 @@
 import logging
 import os
 import json
+import yaml
 
-from flask import Flask
+from flask import Flask as BaseFlask, Config as BaseConfig
 from flask.ext.principal import Principal
 from flask.ext.login import LoginManager
 from flask.ext.mail import Mail
@@ -24,7 +25,34 @@ from data.userevent import UserEventsBuilderModule
 from datetime import datetime
 
 
-OVERRIDE_CONFIG_FILENAME = 'conf/stack/config.py'
+class Config(BaseConfig):
+  """ Flask config enhanced with a `from_yamlfile` method """
+   
+  def from_yamlfile(self, config_file):
+    with open(config_file) as f:
+      c = yaml.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():
+          self[key] = c[key]
+
+class Flask(BaseFlask):
+  """ Extends the Flask class to implement our custom Config class. """
+
+  def make_config(self, instance_relative=False):
+    root_path = self.instance_path if instance_relative else self.root_path
+    return Config(root_path, self.default_config)
+
+
+OVERRIDE_CONFIG_YAML_FILENAME = 'conf/stack/config.yaml'
+OVERRIDE_CONFIG_PY_FILENAME = 'conf/stack/config.py'
+
 OVERRIDE_CONFIG_KEY = 'QUAY_OVERRIDE_CONFIG'
 LICENSE_FILENAME = 'conf/stack/license.enc'
 
@@ -42,9 +70,13 @@ else:
   logger.debug('Loading default config.')
   app.config.from_object(DefaultConfig())
 
-  if os.path.exists(OVERRIDE_CONFIG_FILENAME):
+  if os.path.exists(OVERRIDE_CONFIG_PY_FILENAME):
-    logger.debug('Applying config file: %s', OVERRIDE_CONFIG_FILENAME)
+    logger.debug('Applying config file: %s', OVERRIDE_CONFIG_PY_FILENAME)
-    app.config.from_pyfile(OVERRIDE_CONFIG_FILENAME)
+    app.config.from_pyfile(OVERRIDE_CONFIG_PY_FILENAME)
+
+  if os.path.exists(OVERRIDE_CONFIG_YAML_FILENAME):
+    logger.debug('Applying config file: %s', OVERRIDE_CONFIG_YAML_FILENAME)
+    app.config.from_yamlfile(OVERRIDE_CONFIG_YAML_FILENAME)
 
   environ_config = json.loads(os.environ.get(OVERRIDE_CONFIG_KEY, '{}'))
   app.config.update(environ_config)