From 0a5248e13291c41243b88f2e19f07cad5160e303 Mon Sep 17 00:00:00 2001
From: Claudiu Popa <cpopa@cloudbasesolutions.com>
Date: Mon, 11 May 2015 16:00:19 +0300
Subject: [PATCH] Don't hard fail when a plugin can't be imported

This patch tries to fix a common problem with a lot of configuration
files out there, which contains invalid plugin paths. Instead of failing
with a traceback, which might be confusing to users, we emit an error
which should be clearer and easily debuggable by a non-Python user.

Change-Id: I1390136b37055207787151ebd80ac83dfaefea4c
---
 cloudbaseinit/plugins/common/factory.py     | 11 ++++++++++-
 cloudbaseinit/tests/plugins/test_factory.py | 11 +++++++++++
 2 files changed, 21 insertions(+), 1 deletion(-)

diff --git a/cloudbaseinit/plugins/common/factory.py b/cloudbaseinit/plugins/common/factory.py
index 50ba7918..b74f4139 100644
--- a/cloudbaseinit/plugins/common/factory.py
+++ b/cloudbaseinit/plugins/common/factory.py
@@ -14,6 +14,7 @@
 
 from oslo.config import cfg
 
+from cloudbaseinit.openstack.common import log as logging
 from cloudbaseinit.utils import classloader
 
 opts = [
@@ -44,11 +45,19 @@ opts = [
 
 CONF = cfg.CONF
 CONF.register_opts(opts)
+LOG = logging.getLogger(__name__)
 
 
 def load_plugins():
     plugins = []
     cl = classloader.ClassLoader()
     for class_path in CONF.plugins:
-        plugins.append(cl.load_class(class_path)())
+        try:
+            plugin_cls = cl.load_class(class_path)
+        except ImportError:
+            LOG.error("Could not import plugin module %r", class_path)
+            continue
+
+        plugin = plugin_cls()
+        plugins.append(plugin)
     return plugins
diff --git a/cloudbaseinit/tests/plugins/test_factory.py b/cloudbaseinit/tests/plugins/test_factory.py
index eec6c49d..ff05240e 100644
--- a/cloudbaseinit/tests/plugins/test_factory.py
+++ b/cloudbaseinit/tests/plugins/test_factory.py
@@ -21,6 +21,7 @@ except ImportError:
 from oslo.config import cfg
 
 from cloudbaseinit.plugins.common import factory
+from cloudbaseinit.tests import testutils
 
 CONF = cfg.CONF
 
@@ -35,3 +36,13 @@ class PluginFactoryTests(unittest.TestCase):
         response = factory.load_plugins()
         self.assertEqual(expected, mock_load_class.call_args_list)
         self.assertTrue(response is not None)
+
+    @testutils.ConfPatcher('plugins', ['missing.plugin'])
+    def test_load_plugins_plugin_failed(self):
+        with testutils.LogSnatcher('cloudbaseinit.plugins.'
+                                   'common.factory') as snatcher:
+            plugins = factory.load_plugins()
+
+        self.assertEqual([], plugins)
+        self.assertEqual(["Could not import plugin module 'missing.plugin'"],
+                         snatcher.output)