src/python/grpcio_status/grpc_status/rpc_status.py

# Copyright 2018 The gRPC Authors
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License 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.
"""Reference implementation for status mapping in gRPC Python."""

import collections

import grpc

# TODO(https://github.com/bazelbuild/bazel/issues/6844)
# Due to Bazel issue, the namespace packages won't resolve correctly.
# Adding this unused-import as a workaround to avoid module-not-found error
# under Bazel builds.
import google.protobuf  # pylint: disable=unused-import
from google.rpc import status_pb2

_CODE_TO_GRPC_CODE_MAPPING = {x.value[0]: x for x in grpc.StatusCode}

_GRPC_DETAILS_METADATA_KEY = 'grpc-status-details-bin'


class _Status(
        collections.namedtuple(
            '_Status', ('code', 'details', 'trailing_metadata')), grpc.Status):
    pass


def _code_to_grpc_status_code(code):
    try:
        return _CODE_TO_GRPC_CODE_MAPPING[code]
    except KeyError:
        raise ValueError('Invalid status code %s' % code)


def from_call(call):
    """Returns a google.rpc.status.Status message corresponding to a given grpc.Call.

    This is an EXPERIMENTAL API.

    Args:
      call: A grpc.Call instance.

    Returns:
      A google.rpc.status.Status message representing the status of the RPC.

    Raises:
      ValueError: If the gRPC call's code or details are inconsistent with the
        status code and message inside of the google.rpc.status.Status.
    """
    for key, value in call.trailing_metadata():
        if key == _GRPC_DETAILS_METADATA_KEY:
            rich_status = status_pb2.Status.FromString(value)
            if call.code().value[0] != rich_status.code:
                raise ValueError(
                    'Code in Status proto (%s) doesn\'t match status code (%s)'
                    % (_code_to_grpc_status_code(rich_status.code),
                       call.code()))
            if call.details() != rich_status.message:
                raise ValueError(
                    'Message in Status proto (%s) doesn\'t match status details (%s)'
                    % (rich_status.message, call.details()))
            return rich_status
    return None


def to_status(status):
    """Convert a google.rpc.status.Status message to grpc.Status.

    This is an EXPERIMENTAL API.

    Args:
      status: a google.rpc.status.Status message representing the non-OK status
        to terminate the RPC with and communicate it to the client.

    Returns:
      A grpc.Status instance representing the input google.rpc.status.Status message.
    """
    return _Status(
        code=_code_to_grpc_status_code(status.code),
        details=status.message,
        trailing_metadata=((_GRPC_DETAILS_METADATA_KEY,
                            status.SerializeToString()),))