A WIP commit on an event-based error handler. Needs tests, etc. but would appreciate review of basic approach.

garnaat · garnaat · commit 2fb19025377f · 2013-08-29T08:43:33.000-07:00
diff --git a/awscli/clidriver.py b/awscli/clidriver.py
@@ -32,7 +32,6 @@
 from awscli.arguments import BooleanArgument
 from awscli.arguments import CLIArgument
 from awscli.arguments import UnknownArgumentError
-from awscli.arguments import BadArgumentError
 
 
 LOG = logging.getLogger('awscli.clidriver')
@@ -472,7 +471,14 @@ def _create_operation_parser(self, arg_table):
 
 
 class CLIOperationCaller(object):
-    """Call an AWS operation and format the response."""
+    """
+    Call an AWS operation and format the response.
+
+    This class handles the non-error path.  If an HTTP error occurs
+    on the call to the service operation, it will be detected and
+    handled by the :class:`awscli.errorhandler.ErrorHandler` which
+    is registered on the ``after-call`` event.
+    """
 
     def __init__(self, session):
         self._session = session
@@ -492,7 +498,6 @@ def invoke(self, operation_object, parameters, parsed_globals):
                                                                  **parameters)
             self._display_response(operation_object, response_data,
                                    parsed_globals)
-            return self._handle_http_response(http_response, response_data)
 
     def _display_response(self, operation, response, args):
         output = args.output
@@ -501,33 +506,3 @@ def _display_response(self, operation, response, args):
         formatter = get_formatter(output, args)
         formatter(operation, response)
 
-    def _handle_http_response(self, http_response, response_data):
-        if http_response.status_code >= 500:
-            msg = self._session.get_data('messages/ServerError')
-            code, message = self._get_error_code_and_message(response_data)
-            sys.stderr.write(msg.format(error_code=code,
-                                        error_message=message))
-            sys.stderr.write('\n')
-            return http_response.status_code - 399
-        if http_response.status_code >= 400:
-            msg = self._session.get_data('messages/ClientError')
-            code, message = self._get_error_code_and_message(response_data)
-            sys.stderr.write(msg.format(error_code=code,
-                                        error_message=message))
-            sys.stderr.write('\n')
-            return http_response.status_code - 399
-        return 0
-
-    def _get_error_code_and_message(self, response):
-        code = 'Unknown'
-        message = 'Unknown'
-        if 'Errors' in response:
-            if isinstance(response['Errors'], list):
-                error = response['Errors'][-1]
-                if 'Code' in error:
-                    code = error['Code']
-                elif 'Type' in error:
-                    code = error['Type']
-                if 'Message' in error:
-                    message = error['Message']
-        return (code, message)
diff --git a/awscli/data/messages.json b/awscli/data/messages.json
diff --git a/awscli/errorhandler.py b/awscli/errorhandler.py
@@ -0,0 +1,62 @@
+# Copyright 2013 Amazon.com, Inc. or its affiliates. All Rights Reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License"). You
+# may not use this file except in compliance with the License. A copy of
+# the License is located at
+#
+#     http://aws.amazon.com/apache2.0/
+#
+# or in the "license" file accompanying this file. This file is
+# distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF
+# ANY KIND, either express or implied. See the License for the specific
+# language governing permissions and limitations under the License.
+
+import sys
+import logging
+
+LOG = logging.getLogger(__name__)
+
+
+class ErrorHandler(object):
+    """
+    This class is responsible for handling any HTTP errors that occur
+    when a service operation is called.  It is registered for the
+    ``after-call`` event and will have the opportunity to inspect
+    all operation calls.  If the HTTP response contains an error
+    ``status_code`` an appropriate error message will be printed and
+    the handler will short-circuit all further processing by exiting
+    with an appropriate error code.
+    """
+
+    ClientError = "A client error ({error_code}) occurred: {error_message}"
+    ServerError = "A server error ({error_code}) occurred: {error_message}"
+
+    def __call__(self, http_response, parsed, operation, **kwargs):
+        LOG.debug('HTTP Response Code: %d', http_response.status_code)
+        if http_response.status_code >= 500:
+            code, message = self._get_error_code_and_message(parsed)
+            sys.stderr.write(self.ServerError.format(error_code=code,
+                                                     error_message=message))
+            sys.stderr.write('\n')
+            sys.exit(http_response.status_code - 399)
+        if http_response.status_code >= 400 or http_response.status_code == 301:
+            code, message = self._get_error_code_and_message(parsed)
+            sys.stderr.write(self.ClientError.format(error_code=code,
+                                                     error_message=message))
+            sys.stderr.write('\n')
+            sys.exit(http_response.status_code - 399)
+        return 0
+
+    def _get_error_code_and_message(self, response):
+        code = 'Unknown'
+        message = 'Unknown'
+        if 'Errors' in response:
+            if isinstance(response['Errors'], list):
+                error = response['Errors'][-1]
+                if 'Code' in error:
+                    code = error['Code']
+                elif 'Type' in error:
+                    code = error['Type']
+                if 'Message' in error:
+                    message = error['Message']
+        return (code, message)
diff --git a/awscli/handlers.py b/awscli/handlers.py
@@ -17,6 +17,7 @@
 
 """
 from awscli.argprocess import ParamShorthand
+from awscli.errorhandler import ErrorHandler
 from awscli.customizations.streamingoutputarg import add_streaming_output_arg
 from awscli.customizations.addexamples import add_examples
 from awscli.customizations.removals import register_removals
@@ -33,9 +34,12 @@
 from awscli.customizations.sessendemail import register_ses_send_email
 from awscli.customizations.iamvirtmfa import IAMVMFAWrapper
 
+
 def awscli_initialize(event_handlers):
     param_shorthand = ParamShorthand()
     event_handlers.register('process-cli-arg', param_shorthand)
+    error_handler = ErrorHandler()
+    event_handlers.register('after-call.*.*', error_handler)
     # The following will get fired for every option we are
     # documenting.  It will attempt to add an example_fn on to
     # the parameter object if the parameter supports shorthand
