default_value_client_interceptor.py

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# Copyright 2017 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.
"""Interceptor that adds headers to outgoing requests."""
 
import grpc
 
 
class _ConcreteValue(grpc.Future):
 
    def __init__(self, result):
        self._result = result
 
    def cancel(self):
        return False
 
    def cancelled(self):
        return False
 
    def running(self):
        return False
 
    def done(self):
        return True
 
    def result(self, timeout=None):
        return self._result
 
    def exception(self, timeout=None):
        return None
 
    def traceback(self, timeout=None):
        return None
 
    def add_done_callback(self, fn):
        fn(self._result)
 
 
class DefaultValueClientInterceptor(grpc.UnaryUnaryClientInterceptor,
                                    grpc.StreamUnaryClientInterceptor):
 
    def __init__(self, value):
        self._default = _ConcreteValue(value)
 
    def _intercept_call(self, continuation, client_call_details,
                        request_or_iterator):
        response = continuation(client_call_details, request_or_iterator)
        return self._default if response.exception() else response
 
    def intercept_unary_unary(self, continuation, client_call_details, request):
        return self._intercept_call(continuation, client_call_details, request)
 
    def intercept_stream_unary(self, continuation, client_call_details,
                               request_iterator):
        return self._intercept_call(continuation, client_call_details,
                                    request_iterator)