Some error handling improvements

openstack/common/messaging/__init__.py

@@ -13,10 +13,14 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 
-from .exceptions import MessagingException
-from .exceptions import MessagingTimeout
 from .rpc.client import RPCClient
 from .rpc.server import BlockingRPCServer
 from .serializer import Serializer
 from .target import Target
 from .transport import get_transport
+
+from .exceptions import MessagingException
+from .exceptions import MessagingTimeout
+
+from .transport import DriverLoadFailure
+from .transport import InvalidTransportURL

openstack/common/messaging/_drivers/impl_fake.py

@@ -20,7 +20,7 @@ import Queue
 import time
 
 from openstack.common.gettextutils import _
-from openstack.common.messaging import exceptions
+from openstack.common import messaging
 from openstack.common.messaging._drivers import base
 from openstack.common.messaging import _utils as utils
 
@@ -119,7 +119,7 @@ class FakeDriver(base.BaseDriver):
                 break
 
             if timeout and (time.time() - start_time > timeout):
-                raise exceptions.MessagingTimeout(
+                raise messaging.MessagingTimeout(
                     _('No listeners found for topic %s') % target.topic)
 
             time.sleep(.05)

openstack/common/messaging/exceptions.py

@@ -13,9 +13,16 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 
+
 class MessagingException(Exception):
-    pass
+    """Base class for exceptions."""
+
+    def __init__(self, msg=None):
+        self.msg = msg
+
+    def __str__(self):
+        return self.msg
 
 
 class MessagingTimeout(MessagingException):
-    pass
+    """Raised if message sending times out."""

openstack/common/messaging/transport.py

@@ -21,6 +21,9 @@ import urlparse
 from oslo.config import cfg
 from stevedore import driver
 
+from openstack.common.messaging import exceptions
+
+
 _transport_opts = [
     cfg.StrOpt('transport_url',
                default=None,
@@ -75,6 +78,24 @@ class Transport(object):
         return self._driver.listen(target)
 
 
+class InvalidTransportURL(exceptions.MessagingException):
+    """Raised if transport URL is invalid."""
+
+    def __init__(self, url, msg):
+        super(InvalidTransportURL, self).__init__(msg)
+        self.url = url
+
+
+class DriverLoadFailure(exceptions.MessagingException):
+    """Raised if a transport driver can't be loaded."""
+
+    def __init__(self, driver, ex):
+        msg = 'Failed to load transport driver "%s": %s' % (driver, ex)
+        super(DriverLoadFailure, self).__init__(msg)
+        self.driver = driver
+        self.ex = ex
+
+
 def get_transport(conf, url=None):
     """A factory method for Transport objects.
 
@@ -102,6 +123,8 @@ def get_transport(conf, url=None):
     url = url or conf.transport_url
     if url is not None:
         rpc_backend = urlparse.urlparse(url).scheme
+        if not rpc_backend:
+            raise InvalidTransportURL(url, 'No scheme specified in "%s"' % url)
     else:
         rpc_backend = conf.rpc_backend
 
@@ -109,9 +132,13 @@ def get_transport(conf, url=None):
     if url is not None:
         kwargs['url'] = url
 
-    mgr = driver.DriverManager('openstack.common.messaging.drivers',
+    try:
-                               rpc_backend,
+        mgr = driver.DriverManager('openstack.common.messaging.drivers',
-                               invoke_on_load=True,
+                                   rpc_backend,
-                               invoke_args=[conf],
+                                   invoke_on_load=True,
-                               invoke_kwds=kwargs)
+                                   invoke_args=[conf],
+                                   invoke_kwds=kwargs)
+    except RuntimeError as ex:
+        raise DriverLoadFailure(rpc_backend, ex)
+
     return Transport(mgr.driver)