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1# Copyright 2018 gRPC authors.
2#
3# Licensed under the Apache License, Version 2.0 (the "License");
4# you may not use this file except in compliance with the License.
5# You may obtain a copy of the License at
6#
7#     http://www.apache.org/licenses/LICENSE-2.0
8#
9# Unless required by applicable law or agreed to in writing, software
10# distributed under the License is distributed on an "AS IS" BASIS,
11# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12# See the License for the specific language governing permissions and
13# limitations under the License.
14"""gRPC's experimental APIs.
15
16These APIs are subject to be removed during any minor version release.
17"""
18
19import copy
20import functools
21import sys
22import warnings
23
24import grpc
25from grpc._cython import cygrpc as _cygrpc
26
27_EXPERIMENTAL_APIS_USED = set()
28
29
30class ChannelOptions(object):
31    """Indicates a channel option unique to gRPC Python.
32
33     This enumeration is part of an EXPERIMENTAL API.
34
35     Attributes:
36       SingleThreadedUnaryStream: Perform unary-stream RPCs on a single thread.
37    """
38    SingleThreadedUnaryStream = "SingleThreadedUnaryStream"
39
40
41class UsageError(Exception):
42    """Raised by the gRPC library to indicate usage not allowed by the API."""
43
44
45# It's important that there be a single insecure credentials object so that its
46# hash is deterministic and can be used for indexing in the simple stubs cache.
47_insecure_channel_credentials = grpc.ChannelCredentials(
48    _cygrpc.channel_credentials_insecure())
49
50
51def insecure_channel_credentials():
52    """Creates a ChannelCredentials for use with an insecure channel.
53
54    THIS IS AN EXPERIMENTAL API.
55    """
56    return _insecure_channel_credentials
57
58
59class ExperimentalApiWarning(Warning):
60    """A warning that an API is experimental."""
61
62
63def _warn_experimental(api_name, stack_offset):
64    if api_name not in _EXPERIMENTAL_APIS_USED:
65        _EXPERIMENTAL_APIS_USED.add(api_name)
66        msg = ("'{}' is an experimental API. It is subject to change or ".
67               format(api_name) +
68               "removal between minor releases. Proceed with caution.")
69        warnings.warn(msg, ExperimentalApiWarning, stacklevel=2 + stack_offset)
70
71
72def experimental_api(f):
73
74    @functools.wraps(f)
75    def _wrapper(*args, **kwargs):
76        _warn_experimental(f.__name__, 1)
77        return f(*args, **kwargs)
78
79    return _wrapper
80
81
82def wrap_server_method_handler(wrapper, handler):
83    """Wraps the server method handler function.
84
85    The server implementation requires all server handlers being wrapped as
86    RpcMethodHandler objects. This helper function ease the pain of writing
87    server handler wrappers.
88
89    Args:
90        wrapper: A wrapper function that takes in a method handler behavior
91          (the actual function) and returns a wrapped function.
92        handler: A RpcMethodHandler object to be wrapped.
93
94    Returns:
95        A newly created RpcMethodHandler.
96    """
97    if not handler:
98        return None
99
100    if not handler.request_streaming:
101        if not handler.response_streaming:
102            # NOTE(lidiz) _replace is a public API:
103            #   https://docs.python.org/dev/library/collections.html
104            return handler._replace(unary_unary=wrapper(handler.unary_unary))
105        else:
106            return handler._replace(unary_stream=wrapper(handler.unary_stream))
107    else:
108        if not handler.response_streaming:
109            return handler._replace(stream_unary=wrapper(handler.stream_unary))
110        else:
111            return handler._replace(
112                stream_stream=wrapper(handler.stream_stream))
113
114
115__all__ = (
116    'ChannelOptions',
117    'ExperimentalApiWarning',
118    'UsageError',
119    'insecure_channel_credentials',
120    'wrap_server_method_handler',
121)
122
123if sys.version_info > (3, 6):
124    from grpc._simple_stubs import unary_unary, unary_stream, stream_unary, stream_stream
125    __all__ = __all__ + (unary_unary, unary_stream, stream_unary, stream_stream)
126