Expose RemoteError exception in the public API

If a remote endpoint raises an exception which the client is not allowed
to (or cannot) deserialize, then RPCClient.call() raises a RemoteError
exception instead.

Make this exception type part of the public API.

Change-Id: I70be0ab7d40af3224d93d6bd0522c1a82f6303c3

doc/source/rpcclient.rst

@@ -6,3 +6,5 @@ RPC Client
 
 .. autoclass:: RPCClient
    :members:
+
+.. autoexception:: RemoteError

oslo/messaging/_drivers/common.py

@@ -23,6 +23,7 @@ import sys
 import traceback
 
 from oslo.config import cfg
+from oslo import messaging
 import six
 
 from oslo.messaging.openstack.common import importutils
@@ -341,7 +342,7 @@ def deserialize_remote_exception(conf, data):
     # order to prevent arbitrary code execution.
     conf.register_opts(_exception_opts)
     if module not in conf.allowed_rpc_exception_modules:
-        return RemoteError(name, failure.get('message'), trace)
+        return messaging.RemoteError(name, failure.get('message'), trace)
 
     try:
         mod = importutils.import_module(module)
@@ -351,7 +352,7 @@ def deserialize_remote_exception(conf, data):
 
         failure = klass(*failure.get('args', []), **failure.get('kwargs', {}))
     except (AttributeError, TypeError, ImportError):
-        return RemoteError(name, failure.get('message'), trace)
+        return messaging.RemoteError(name, failure.get('message'), trace)
 
     ex_type = type(failure)
     str_override = lambda self: message

oslo/messaging/rpc/__init__.py

@@ -21,6 +21,7 @@ __all__ = [
     'RPCDispatcher',
     'RPCDispatcherError',
     'RPCVersionCapError',
+    'RemoteError',
     'UnsupportedVersion',
     'expected_exceptions',
     'get_rpc_server',

oslo/messaging/rpc/client.py

@@ -20,6 +20,7 @@ __all__ = [
     'ClientSendError',
     'RPCClient',
     'RPCVersionCapError',
+    'RemoteError',
 ]
 
 import inspect
@@ -41,6 +42,26 @@ _client_opts = [
 _LOG = logging.getLogger(__name__)
 
 
+class RemoteError(exceptions.MessagingException):
+
+    """Signifies that a remote endpoint method has raised an exception.
+
+    Contains a string representation of the type of the original exception,
+    the value of the original exception, and the traceback.  These are
+    sent to the parent as a joined string so printing the exception
+    contains all of the relevant info.
+    """
+
+    def __init__(self, exc_type=None, value=None, traceback=None):
+        self.exc_type = exc_type
+        self.value = value
+        self.traceback = traceback
+        msg = ("Remote error: %(exc_type)s %(value)s\n%(traceback)s." %
+               dict(exc_type=self.exc_type, value=self.value,
+                    traceback=self.traceback))
+        super(RemoteError, self).__init__(msg)
+
+
 class RPCVersionCapError(exceptions.MessagingException):
 
     def __init__(self, version, version_cap):
@@ -335,7 +356,7 @@ class RPCClient(object):
         :type method: str
         :param kwargs: a dict of method arguments
         :param kwargs: dict
-        :raises: MessagingTimeout
+        :raises: MessagingTimeout, RemoteError
         """
         return self.prepare().call(ctxt, method, **kwargs)
 

tests/test_exception_serialization.py

@@ -17,6 +17,7 @@ import sys
 
 import testscenarios
 
+from oslo import messaging
 from oslo.messaging._drivers import common as exceptions
 from oslo.messaging.openstack.common import jsonutils
 from tests import utils as test_utils
@@ -160,7 +161,7 @@ class DeserializeRemoteExceptionTestCase(test_utils.BaseTestCase):
               args=['test'],
               kwargs={},
               str='test\ntraceback\ntraceback\n',
-              msg='test',
+              message='test',
               remote_name='Exception',
               remote_args=('test\ntraceback\ntraceback\n', ),
               remote_kwargs={})),
@@ -172,7 +173,7 @@ class DeserializeRemoteExceptionTestCase(test_utils.BaseTestCase):
               args=[],
               kwargs={},
               str='test\ntraceback\ntraceback\n',
-              msg='I am Nova',
+              message='I am Nova',
               remote_name='NovaStyleException_Remote',
               remote_args=('I am Nova', ),
               remote_kwargs={})),
@@ -184,7 +185,7 @@ class DeserializeRemoteExceptionTestCase(test_utils.BaseTestCase):
               args=['testing'],
               kwargs={},
               str='test\ntraceback\ntraceback\n',
-              msg='testing',
+              message='testing',
               remote_name='NovaStyleException_Remote',
               remote_args=('testing', ),
               remote_kwargs={})),
@@ -196,7 +197,7 @@ class DeserializeRemoteExceptionTestCase(test_utils.BaseTestCase):
               args=[],
               kwargs={'who': 'Oslo'},
               str='test\ntraceback\ntraceback\n',
-              msg='I am Oslo',
+              message='I am Oslo',
               remote_name='KwargsStyleException_Remote',
               remote_args=('I am Oslo', ),
               remote_kwargs={})),
@@ -204,7 +205,7 @@ class DeserializeRemoteExceptionTestCase(test_utils.BaseTestCase):
          dict(allowed=[],
               clsname='Exception',
               modname='exceptions',
-              cls=exceptions.RemoteError,
+              cls=messaging.RemoteError,
               args=[],
               kwargs={},
               str=("Remote error: Exception test\n"
@@ -212,8 +213,7 @@ class DeserializeRemoteExceptionTestCase(test_utils.BaseTestCase):
               msg=("Remote error: Exception test\n"
                    "[u'traceback\\ntraceback\\n']."),
               remote_name='RemoteError',
-              remote_args=("Remote error: Exception test\n"
-                           "[u'traceback\\ntraceback\\n'].", ),
+              remote_args=(),
               remote_kwargs={'exc_type': 'Exception',
                              'value': 'test',
                              'traceback': 'traceback\ntraceback\n'})),
@@ -221,7 +221,7 @@ class DeserializeRemoteExceptionTestCase(test_utils.BaseTestCase):
          dict(allowed=['notexist'],
               clsname='Exception',
               modname='notexist',
-              cls=exceptions.RemoteError,
+              cls=messaging.RemoteError,
               args=[],
               kwargs={},
               str=("Remote error: Exception test\n"
@@ -229,8 +229,7 @@ class DeserializeRemoteExceptionTestCase(test_utils.BaseTestCase):
               msg=("Remote error: Exception test\n"
                    "[u'traceback\\ntraceback\\n']."),
               remote_name='RemoteError',
-              remote_args=("Remote error: Exception test\n"
-                           "[u'traceback\\ntraceback\\n'].", ),
+              remote_args=(),
               remote_kwargs={'exc_type': 'Exception',
                              'value': 'test',
                              'traceback': 'traceback\ntraceback\n'})),
@@ -238,7 +237,7 @@ class DeserializeRemoteExceptionTestCase(test_utils.BaseTestCase):
          dict(allowed=['exceptions'],
               clsname='FarcicalError',
               modname='exceptions',
-              cls=exceptions.RemoteError,
+              cls=messaging.RemoteError,
               args=[],
               kwargs={},
               str=("Remote error: FarcicalError test\n"
@@ -246,8 +245,7 @@ class DeserializeRemoteExceptionTestCase(test_utils.BaseTestCase):
               msg=("Remote error: FarcicalError test\n"
                    "[u'traceback\\ntraceback\\n']."),
               remote_name='RemoteError',
-              remote_args=("Remote error: FarcicalError test\n"
-                           "[u'traceback\\ntraceback\\n'].", ),
+              remote_args=(),
               remote_kwargs={'exc_type': 'FarcicalError',
                              'value': 'test',
                              'traceback': 'traceback\ntraceback\n'})),
@@ -255,7 +253,7 @@ class DeserializeRemoteExceptionTestCase(test_utils.BaseTestCase):
          dict(allowed=['exceptions'],
               clsname='Exception',
               modname='exceptions',
-              cls=exceptions.RemoteError,
+              cls=messaging.RemoteError,
               args=[],
               kwargs={'foobar': 'blaa'},
               str=("Remote error: Exception test\n"
@@ -263,8 +261,7 @@ class DeserializeRemoteExceptionTestCase(test_utils.BaseTestCase):
               msg=("Remote error: Exception test\n"
                    "[u'traceback\\ntraceback\\n']."),
               remote_name='RemoteError',
-              remote_args=("Remote error: Exception test\n"
-                           "[u'traceback\\ntraceback\\n'].", ),
+              remote_args=(),
               remote_kwargs={'exc_type': 'Exception',
                              'value': 'test',
                              'traceback': 'traceback\ntraceback\n'})),
@@ -272,7 +269,7 @@ class DeserializeRemoteExceptionTestCase(test_utils.BaseTestCase):
          dict(allowed=['exceptions'],
               clsname='SystemExit',
               modname='exceptions',
-              cls=exceptions.RemoteError,
+              cls=messaging.RemoteError,
               args=[],
               kwargs={},
               str=("Remote error: SystemExit test\n"
@@ -280,8 +277,7 @@ class DeserializeRemoteExceptionTestCase(test_utils.BaseTestCase):
               msg=("Remote error: SystemExit test\n"
                    "[u'traceback\\ntraceback\\n']."),
               remote_name='RemoteError',
-              remote_args=("Remote error: SystemExit test\n"
-                           "[u'traceback\\ntraceback\\n'].", ),
+              remote_args=(),
               remote_kwargs={'exc_type': 'SystemExit',
                              'value': 'test',
                              'traceback': 'traceback\ntraceback\n'})),
@@ -310,5 +306,8 @@ class DeserializeRemoteExceptionTestCase(test_utils.BaseTestCase):
         self.assertIsInstance(ex, self.cls)
         self.assertEqual(ex.__class__.__name__, self.remote_name)
         self.assertEqual(str(ex), self.str)
-        self.assertEqual(ex.message, self.msg)
+        if hasattr(self, 'msg'):
+            self.assertEqual(ex.msg, self.msg)
+        else:
+            self.assertEqual(ex.message, self.message)
         self.assertEqual(ex.args, self.remote_args)