implementations.py

# Copyright 2015-2016 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.
"""Entry points into the Beta API of gRPC Python."""

# threading is referenced from specification in this module.
import threading  # pylint: disable=unused-import

# interfaces, cardinality, and face are referenced from specification in this
# module.
import grpc
from grpc import _auth
from grpc.beta import _client_adaptations
from grpc.beta import _metadata
from grpc.beta import _server_adaptations
from grpc.beta import interfaces  # pylint: disable=unused-import
from grpc.framework.common import cardinality  # pylint: disable=unused-import
from grpc.framework.interfaces.face import \
    face  # pylint: disable=unused-import

# pylint: disable=too-many-arguments

ChannelCredentials = grpc.ChannelCredentials
ssl_channel_credentials = grpc.ssl_channel_credentials
CallCredentials = grpc.CallCredentials


def metadata_call_credentials(metadata_plugin, name=None):

    def plugin(context, callback):

        def wrapped_callback(beta_metadata, error):
            callback(_metadata.unbeta(beta_metadata), error)

        metadata_plugin(context, wrapped_callback)

    return grpc.metadata_call_credentials(plugin, name=name)


def google_call_credentials(credentials):
    """Construct CallCredentials from GoogleCredentials.

  Args:
    credentials: A GoogleCredentials object from the oauth2client library.

  Returns:
    A CallCredentials object for use in a GRPCCallOptions object.
  """
    return metadata_call_credentials(_auth.GoogleCallCredentials(credentials))


access_token_call_credentials = grpc.access_token_call_credentials
composite_call_credentials = grpc.composite_call_credentials
composite_channel_credentials = grpc.composite_channel_credentials


class Channel(object):
    """A channel to a remote host through which RPCs may be conducted.

  Only the "subscribe" and "unsubscribe" methods are supported for application
  use. This class' instance constructor and all other attributes are
  unsupported.
  """

    def __init__(self, channel):
        self._channel = channel

    def subscribe(self, callback, try_to_connect=None):
        """Subscribes to this Channel's connectivity.

    Args:
      callback: A callable to be invoked and passed an
        interfaces.ChannelConnectivity identifying this Channel's connectivity.
        The callable will be invoked immediately upon subscription and again for
        every change to this Channel's connectivity thereafter until it is
        unsubscribed.
      try_to_connect: A boolean indicating whether or not this Channel should
        attempt to connect if it is not already connected and ready to conduct
        RPCs.
    """
        self._channel.subscribe(callback, try_to_connect=try_to_connect)

    def unsubscribe(self, callback):
        """Unsubscribes a callback from this Channel's connectivity.

    Args:
      callback: A callable previously registered with this Channel from having
        been passed to its "subscribe" method.
    """
        self._channel.unsubscribe(callback)


def insecure_channel(host, port):
    """Creates an insecure Channel to a remote host.

  Args:
    host: The name of the remote host to which to connect.
    port: The port of the remote host to which to connect.
      If None only the 'host' part will be used.

  Returns:
    A Channel to the remote host through which RPCs may be conducted.
  """
    channel = grpc.insecure_channel(host if port is None else '%s:%d' %
                                    (host, port))
    return Channel(channel)


def secure_channel(host, port, channel_credentials):
    """Creates a secure Channel to a remote host.

  Args:
    host: The name of the remote host to which to connect.
    port: The port of the remote host to which to connect.
      If None only the 'host' part will be used.
    channel_credentials: A ChannelCredentials.

  Returns:
    A secure Channel to the remote host through which RPCs may be conducted.
  """
    channel = grpc.secure_channel(
        host if port is None else '%s:%d' % (host, port), channel_credentials)
    return Channel(channel)


class StubOptions(object):
    """A value encapsulating the various options for creation of a Stub.

  This class and its instances have no supported interface - it exists to define
  the type of its instances and its instances exist to be passed to other
  functions.
  """

    def __init__(self, host, request_serializers, response_deserializers,
                 metadata_transformer, thread_pool, thread_pool_size):
        self.host = host
        self.request_serializers = request_serializers
        self.response_deserializers = response_deserializers
        self.metadata_transformer = metadata_transformer
        self.thread_pool = thread_pool
        self.thread_pool_size = thread_pool_size


_EMPTY_STUB_OPTIONS = StubOptions(None, None, None, None, None, None)


def stub_options(host=None,
                 request_serializers=None,
                 response_deserializers=None,
                 metadata_transformer=None,
                 thread_pool=None,
                 thread_pool_size=None):
    """Creates a StubOptions value to be passed at stub creation.

  All parameters are optional and should always be passed by keyword.

  Args:
    host: A host string to set on RPC calls.
    request_serializers: A dictionary from service name-method name pair to
      request serialization behavior.
    response_deserializers: A dictionary from service name-method name pair to
      response deserialization behavior.
    metadata_transformer: A callable that given a metadata object produces
      another metadata object to be used in the underlying communication on the
      wire.
    thread_pool: A thread pool to use in stubs.
    thread_pool_size: The size of thread pool to create for use in stubs;
      ignored if thread_pool has been passed.

  Returns:
    A StubOptions value created from the passed parameters.
  """
    return StubOptions(host, request_serializers, response_deserializers,
                       metadata_transformer, thread_pool, thread_pool_size)


def generic_stub(channel, options=None):
    """Creates a face.GenericStub on which RPCs can be made.

  Args:
    channel: A Channel for use by the created stub.
    options: A StubOptions customizing the created stub.

  Returns:
    A face.GenericStub on which RPCs can be made.
  """
    effective_options = _EMPTY_STUB_OPTIONS if options is None else options
    return _client_adaptations.generic_stub(
        channel._channel,  # pylint: disable=protected-access
        effective_options.host,
        effective_options.metadata_transformer,
        effective_options.request_serializers,
        effective_options.response_deserializers)


def dynamic_stub(channel, service, cardinalities, options=None):
    """Creates a face.DynamicStub with which RPCs can be invoked.

  Args:
    channel: A Channel for the returned face.DynamicStub to use.
    service: The package-qualified full name of the service.
    cardinalities: A dictionary from RPC method name to cardinality.Cardinality
      value identifying the cardinality of the RPC method.
    options: An optional StubOptions value further customizing the functionality
      of the returned face.DynamicStub.

  Returns:
    A face.DynamicStub with which RPCs can be invoked.
  """
    effective_options = _EMPTY_STUB_OPTIONS if options is None else options
    return _client_adaptations.dynamic_stub(
        channel._channel,  # pylint: disable=protected-access
        service,
        cardinalities,
        effective_options.host,
        effective_options.metadata_transformer,
        effective_options.request_serializers,
        effective_options.response_deserializers)


ServerCredentials = grpc.ServerCredentials
ssl_server_credentials = grpc.ssl_server_credentials


class ServerOptions(object):
    """A value encapsulating the various options for creation of a Server.

  This class and its instances have no supported interface - it exists to define
  the type of its instances and its instances exist to be passed to other
  functions.
  """

    def __init__(self, multi_method_implementation, request_deserializers,
                 response_serializers, thread_pool, thread_pool_size,
                 default_timeout, maximum_timeout):
        self.multi_method_implementation = multi_method_implementation
        self.request_deserializers = request_deserializers
        self.response_serializers = response_serializers
        self.thread_pool = thread_pool
        self.thread_pool_size = thread_pool_size
        self.default_timeout = default_timeout
        self.maximum_timeout = maximum_timeout


_EMPTY_SERVER_OPTIONS = ServerOptions(None, None, None, None, None, None, None)


def server_options(multi_method_implementation=None,
                   request_deserializers=None,
                   response_serializers=None,
                   thread_pool=None,
                   thread_pool_size=None,
                   default_timeout=None,
                   maximum_timeout=None):
    """Creates a ServerOptions value to be passed at server creation.

  All parameters are optional and should always be passed by keyword.

  Args:
    multi_method_implementation: A face.MultiMethodImplementation to be called
      to service an RPC if the server has no specific method implementation for
      the name of the RPC for which service was requested.
    request_deserializers: A dictionary from service name-method name pair to
      request deserialization behavior.
    response_serializers: A dictionary from service name-method name pair to
      response serialization behavior.
    thread_pool: A thread pool to use in stubs.
    thread_pool_size: The size of thread pool to create for use in stubs;
      ignored if thread_pool has been passed.
    default_timeout: A duration in seconds to allow for RPC service when
      servicing RPCs that did not include a timeout value when invoked.
    maximum_timeout: A duration in seconds to allow for RPC service when
      servicing RPCs no matter what timeout value was passed when the RPC was
      invoked.

  Returns:
    A StubOptions value created from the passed parameters.
  """
    return ServerOptions(multi_method_implementation, request_deserializers,
                         response_serializers, thread_pool, thread_pool_size,
                         default_timeout, maximum_timeout)


def server(service_implementations, options=None):
    """Creates an interfaces.Server with which RPCs can be serviced.

  Args:
    service_implementations: A dictionary from service name-method name pair to
      face.MethodImplementation.
    options: An optional ServerOptions value further customizing the
      functionality of the returned Server.

  Returns:
    An interfaces.Server with which RPCs can be serviced.
  """
    effective_options = _EMPTY_SERVER_OPTIONS if options is None else options
    return _server_adaptations.server(
        service_implementations, effective_options.multi_method_implementation,
        effective_options.request_deserializers,
        effective_options.response_serializers, effective_options.thread_pool,
        effective_options.thread_pool_size)