From 036c8e56e0408dd54306d6ae230ff246ea95a918 Mon Sep 17 00:00:00 2001
From: Joseph Schorr <joseph.schorr@coreos.com>
Date: Thu, 2 Apr 2015 18:54:09 -0400
Subject: [PATCH] Add proper error handling when the config volume is mounted
 in a read-only state.

---
 endpoints/api/suconfig.py |  1 +
 endpoints/decorated.py    |  9 +++++++++
 util/config/provider.py   | 16 +++++++++++++---
 3 files changed, 23 insertions(+), 3 deletions(-)

diff --git a/endpoints/api/suconfig.py b/endpoints/api/suconfig.py
index 10741d9f3..b1152231c 100644
--- a/endpoints/api/suconfig.py
+++ b/endpoints/api/suconfig.py
@@ -15,6 +15,7 @@ from auth.permissions import SuperUserPermission
 from auth.auth_context import get_authenticated_user
 from data.database import User
 from util.config.configutil import add_enterprise_config_defaults
+from util.config.provider import CannotWriteConfigException
 from util.config.validator import validate_service_for_config, SSL_FILENAMES
 from data.runmigration import run_alembic_migration
 
diff --git a/endpoints/decorated.py b/endpoints/decorated.py
index 182f41a45..b51e1ee2e 100644
--- a/endpoints/decorated.py
+++ b/endpoints/decorated.py
@@ -4,6 +4,7 @@ import json
 from flask import make_response
 from app import app
 from util.useremails import CannotSendEmailException
+from util.config.provider import CannotWriteConfigException
 from data import model
 
 logger = logging.getLogger(__name__)
@@ -17,3 +18,11 @@ def handle_dme(ex):
 def handle_emailexception(ex):
   message = 'Could not send email. Please contact an administrator and report this problem.'
   return make_response(json.dumps({'message': message}), 400)
+
+@app.errorhandler(CannotWriteConfigException)
+def handle_configexception(ex):
+  message = ('Configuration could not be written to the mounted volume. \n' +
+             'Please make sure the mounted volume is not read-only and restart ' +
+             'the setup process. \n\nIssue: %s' % ex)
+
+  return make_response(json.dumps({'message': message}), 400)
\ No newline at end of file
diff --git a/util/config/provider.py b/util/config/provider.py
index 5a2d92757..32bc4c6f9 100644
--- a/util/config/provider.py
+++ b/util/config/provider.py
@@ -6,6 +6,10 @@ from StringIO import StringIO
 
 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)
@@ -24,8 +28,11 @@ def _import_yaml(config_obj, config_file):
 
 
 def _export_yaml(config_obj, config_file):
-  with open(config_file, 'w') as f:
-    f.write(yaml.safe_dump(config_obj, encoding='utf-8', allow_unicode=True))
+  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):
@@ -116,7 +123,10 @@ class FileConfigProvider(BaseProvider):
     return open(os.path.join(self.config_volume, filename), mode)
 
   def save_volume_file(self, filename, flask_file):
-    flask_file.save(os.path.join(self.config_volume, filename))
+    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()