errorhandler.py

# 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 logging

LOG = logging.getLogger(__name__)


class BaseOperationError(Exception):
    MSG_TEMPLATE = ("A {error_type} error ({error_code}) occurred "
                    "when calling the {operation_name} operation: "
                    "{error_message}")

    def __init__(self, error_code, error_message, error_type, operation_name,
                 http_status_code):
        msg = self.MSG_TEMPLATE.format(
            error_code=error_code, error_message=error_message,
            error_type=error_type, operation_name=operation_name)
        super(BaseOperationError, self).__init__(msg)
        self.error_code = error_code
        self.error_message = error_message
        self.error_type = error_type
        self.operation_name = operation_name
        self.http_status_code = http_status_code


class ClientError(BaseOperationError):
    pass


class ServerError(BaseOperationError):
    pass


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.
    """

    def __call__(self, http_response, parsed, model, **kwargs):
        LOG.debug('HTTP Response Code: %d', http_response.status_code)
        error_type = None
        error_class = None
        if http_response.status_code >= 500:
            error_type = 'server'
            error_class = ServerError
        elif http_response.status_code >= 400 or http_response.status_code == 301:
            error_type = 'client'
            error_class = ClientError
        if error_class is not None:
            code, message = self._get_error_code_and_message(parsed)
            raise error_class(
                error_code=code, error_message=message,
                error_type=error_type, operation_name=model.name,
                http_status_code=http_response.status_code)

    def _get_error_code_and_message(self, response):
        code = 'Unknown'
        message = 'Unknown'
        if 'Error' in response:
            error = response['Error']
            return error.get('Code', code), error.get('Message', message)
        return (code, message)