Initial checkin of gRPC to third_party/

third_party/grpc/src/python/grpcio/grpc/framework/interfaces/face/face.py

Index: third_party/grpc/src/python/grpcio/grpc/framework/interfaces/face/face.py
diff --git a/third_party/grpc/src/python/grpcio/grpc/framework/interfaces/face/face.py b/third_party/grpc/src/python/grpcio/grpc/framework/interfaces/face/face.py
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index 0000000000000000000000000000000000000000..404c3a7937aa58b9f958df1bab27977cc85e6128
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@@ -0,0 +1,996 @@
+# Copyright 2015-2016, Google Inc.
+# All rights reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+#
+#     * Redistributions of source code must retain the above copyright
+# notice, this list of conditions and the following disclaimer.
+#     * Redistributions in binary form must reproduce the above
+# copyright notice, this list of conditions and the following disclaimer
+# in the documentation and/or other materials provided with the
+# distribution.
+#     * Neither the name of Google Inc. nor the names of its
+# contributors may be used to endorse or promote products derived from
+# this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+"""Interfaces defining the Face layer of RPC Framework."""
+
+import abc
+import collections
+import enum
+
+# cardinality, style, abandonment, future, and stream are
+# referenced from specification in this module.
+from grpc.framework.common import cardinality  # pylint: disable=unused-import
+from grpc.framework.common import style  # pylint: disable=unused-import
+from grpc.framework.foundation import abandonment  # pylint: disable=unused-import
+from grpc.framework.foundation import future  # pylint: disable=unused-import
+from grpc.framework.foundation import stream  # pylint: disable=unused-import
+
+
+class NoSuchMethodError(Exception):
+  """Raised by customer code to indicate an unrecognized method.
+
+  Attributes:
+    group: The group of the unrecognized method.
+    name: The name of the unrecognized method.
+  """
+
+  def __init__(self, group, method):
+    """Constructor.
+
+    Args:
+      group: The group identifier of the unrecognized RPC name.
+      method: The method identifier of the unrecognized RPC name.
+    """
+    super(NoSuchMethodError, self).__init__()
+    self.group = group
+    self.method = method
+
+  def __repr__(self):
+    return 'face.NoSuchMethodError(%s, %s)' % (self.group, self.method,)
+
+
+class Abortion(
+    collections.namedtuple(
+        'Abortion',
+        ('kind', 'initial_metadata', 'terminal_metadata', 'code', 'details',))):
+  """A value describing RPC abortion.
+
+  Attributes:
+    kind: A Kind value identifying how the RPC failed.
+    initial_metadata: The initial metadata from the other side of the RPC or
+      None if no initial metadata value was received.
+    terminal_metadata: The terminal metadata from the other side of the RPC or
+      None if no terminal metadata value was received.
+    code: The code value from the other side of the RPC or None if no code value
+      was received.
+    details: The details value from the other side of the RPC or None if no
+      details value was received.
+  """
+
+  @enum.unique
+  class Kind(enum.Enum):
+    """Types of RPC abortion."""
+
+    CANCELLED = 'cancelled'
+    EXPIRED = 'expired'
+    LOCAL_SHUTDOWN = 'local shutdown'
+    REMOTE_SHUTDOWN = 'remote shutdown'
+    NETWORK_FAILURE = 'network failure'
+    LOCAL_FAILURE = 'local failure'
+    REMOTE_FAILURE = 'remote failure'
+
+
+class AbortionError(Exception):
+  """Common super type for exceptions indicating RPC abortion.
+
+    initial_metadata: The initial metadata from the other side of the RPC or
+      None if no initial metadata value was received.
+    terminal_metadata: The terminal metadata from the other side of the RPC or
+      None if no terminal metadata value was received.
+    code: The code value from the other side of the RPC or None if no code value
+      was received.
+    details: The details value from the other side of the RPC or None if no
+      details value was received.
+  """
+  __metaclass__ = abc.ABCMeta
+
+  def __init__(self, initial_metadata, terminal_metadata, code, details):
+    super(AbortionError, self).__init__()
+    self.initial_metadata = initial_metadata
+    self.terminal_metadata = terminal_metadata
+    self.code = code
+    self.details = details
+
+  def __str__(self):
+    return '%s(code=%s, details="%s")' % (
+        self.__class__.__name__, self.code, self.details)
+
+
+class CancellationError(AbortionError):
+  """Indicates that an RPC has been cancelled."""
+
+
+class ExpirationError(AbortionError):
+  """Indicates that an RPC has expired ("timed out")."""
+
+
+class LocalShutdownError(AbortionError):
+  """Indicates that an RPC has terminated due to local shutdown of RPCs."""
+
+
+class RemoteShutdownError(AbortionError):
+  """Indicates that an RPC has terminated due to remote shutdown of RPCs."""
+
+
+class NetworkError(AbortionError):
+  """Indicates that some error occurred on the network."""
+
+
+class LocalError(AbortionError):
+  """Indicates that an RPC has terminated due to a local defect."""
+
+
+class RemoteError(AbortionError):
+  """Indicates that an RPC has terminated due to a remote defect."""
+
+
+class RpcContext(object):
+  """Provides RPC-related information and action."""
+  __metaclass__ = abc.ABCMeta
+
+  @abc.abstractmethod
+  def is_active(self):
+    """Describes whether the RPC is active or has terminated."""
+    raise NotImplementedError()
+
+  @abc.abstractmethod
+  def time_remaining(self):
+    """Describes the length of allowed time remaining for the RPC.
+
+    Returns:
+      A nonnegative float indicating the length of allowed time in seconds
+      remaining for the RPC to complete before it is considered to have timed
+      out.
+    """
+    raise NotImplementedError()
+
+  @abc.abstractmethod
+  def add_abortion_callback(self, abortion_callback):
+    """Registers a callback to be called if the RPC is aborted.
+
+    Args:
+      abortion_callback: A callable to be called and passed an Abortion value
+        in the event of RPC abortion.
+    """
+    raise NotImplementedError()
+
+  @abc.abstractmethod
+  def cancel(self):
+    """Cancels the RPC.
+
+    Idempotent and has no effect if the RPC has already terminated.
+    """
+    raise NotImplementedError()
+
+  @abc.abstractmethod
+  def protocol_context(self):
+    """Accesses a custom object specified by an implementation provider.
+
+    Returns:
+      A value specified by the provider of a Face interface implementation
+        affording custom state and behavior.
+    """
+    raise NotImplementedError()
+
+
+class Call(RpcContext):
+  """Invocation-side utility object for an RPC."""
+  __metaclass__ = abc.ABCMeta
+
+  @abc.abstractmethod
+  def initial_metadata(self):
+    """Accesses the initial metadata from the service-side of the RPC.
+
+    This method blocks until the value is available or is known not to have been
+    emitted from the service-side of the RPC.
+
+    Returns:
+      The initial metadata object emitted by the service-side of the RPC, or
+        None if there was no such value.
+    """
+    raise NotImplementedError()
+
+  @abc.abstractmethod
+  def terminal_metadata(self):
+    """Accesses the terminal metadata from the service-side of the RPC.
+
+    This method blocks until the value is available or is known not to have been
+    emitted from the service-side of the RPC.
+
+    Returns:
+      The terminal metadata object emitted by the service-side of the RPC, or
+        None if there was no such value.
+    """
+    raise NotImplementedError()
+
+  @abc.abstractmethod
+  def code(self):
+    """Accesses the code emitted by the service-side of the RPC.
+
+    This method blocks until the value is available or is known not to have been
+    emitted from the service-side of the RPC.
+
+    Returns:
+      The code object emitted by the service-side of the RPC, or None if there
+        was no such value.
+    """
+    raise NotImplementedError()
+
+  @abc.abstractmethod
+  def details(self):
+    """Accesses the details value emitted by the service-side of the RPC.
+
+    This method blocks until the value is available or is known not to have been
+    emitted from the service-side of the RPC.
+
+    Returns:
+      The details value emitted by the service-side of the RPC, or None if there
+        was no such value.
+    """
+    raise NotImplementedError()
+
+
+class ServicerContext(RpcContext):
+  """A context object passed to method implementations."""
+  __metaclass__ = abc.ABCMeta
+
+  @abc.abstractmethod
+  def invocation_metadata(self):
+    """Accesses the metadata from the invocation-side of the RPC.
+
+    This method blocks until the value is available or is known not to have been
+    emitted from the invocation-side of the RPC.
+
+    Returns:
+      The metadata object emitted by the invocation-side of the RPC, or None if
+        there was no such value.
+    """
+    raise NotImplementedError()
+
+  @abc.abstractmethod
+  def initial_metadata(self, initial_metadata):
+    """Accepts the service-side initial metadata value of the RPC.
+
+    This method need not be called by method implementations if they have no
+    service-side initial metadata to transmit.
+
+    Args:
+      initial_metadata: The service-side initial metadata value of the RPC to
+        be transmitted to the invocation side of the RPC.
+    """
+    raise NotImplementedError()
+
+  @abc.abstractmethod
+  def terminal_metadata(self, terminal_metadata):
+    """Accepts the service-side terminal metadata value of the RPC.
+
+    This method need not be called by method implementations if they have no
+    service-side terminal metadata to transmit.
+
+    Args:
+      terminal_metadata: The service-side terminal metadata value of the RPC to
+        be transmitted to the invocation side of the RPC.
+    """
+    raise NotImplementedError()
+
+  @abc.abstractmethod
+  def code(self, code):
+    """Accepts the service-side code of the RPC.
+
+    This method need not be called by method implementations if they have no
+    code to transmit.
+
+    Args:
+      code: The code of the RPC to be transmitted to the invocation side of the
+        RPC.
+    """
+    raise NotImplementedError()
+
+  @abc.abstractmethod
+  def details(self, details):
+    """Accepts the service-side details of the RPC.
+
+    This method need not be called by method implementations if they have no
+    service-side details to transmit.
+
+    Args:
+      details: The service-side details value of the RPC to be transmitted to
+        the invocation side of the RPC.
+    """
+    raise NotImplementedError()
+
+
+class ResponseReceiver(object):
+  """Invocation-side object used to accept the output of an RPC."""
+  __metaclass__ = abc.ABCMeta
+
+  @abc.abstractmethod
+  def initial_metadata(self, initial_metadata):
+    """Receives the initial metadata from the service-side of the RPC.
+
+    Args:
+      initial_metadata: The initial metadata object emitted from the
+        service-side of the RPC.
+    """
+    raise NotImplementedError()
+
+  @abc.abstractmethod
+  def response(self, response):
+    """Receives a response from the service-side of the RPC.
+
+    Args:
+      response: A response object emitted from the service-side of the RPC.
+    """
+    raise NotImplementedError()
+
+  @abc.abstractmethod
+  def complete(self, terminal_metadata, code, details):
+    """Receives the completion values emitted from the service-side of the RPC.
+
+    Args:
+      terminal_metadata: The terminal metadata object emitted from the
+        service-side of the RPC.
+      code: The code object emitted from the service-side of the RPC.
+      details: The details object emitted from the service-side of the RPC.
+    """
+    raise NotImplementedError()
+
+
+class UnaryUnaryMultiCallable(object):
+  """Affords invoking a unary-unary RPC in any call style."""
+  __metaclass__ = abc.ABCMeta
+
+  @abc.abstractmethod
+  def __call__(
+      self, request, timeout, metadata=None, with_call=False,
+      protocol_options=None):
+    """Synchronously invokes the underlying RPC.
+
+    Args:
+      request: The request value for the RPC.
+      timeout: A duration of time in seconds to allow for the RPC.
+      metadata: A metadata value to be passed to the service-side of
+        the RPC.
+      with_call: Whether or not to include return a Call for the RPC in addition
+        to the response.
+      protocol_options: A value specified by the provider of a Face interface
+        implementation affording custom state and behavior.
+
+    Returns:
+      The response value for the RPC, and a Call for the RPC if with_call was
+        set to True at invocation.
+
+    Raises:
+      AbortionError: Indicating that the RPC was aborted.
+    """
+    raise NotImplementedError()
+
+  @abc.abstractmethod
+  def future(self, request, timeout, metadata=None, protocol_options=None):
+    """Asynchronously invokes the underlying RPC.
+
+    Args:
+      request: The request value for the RPC.
+      timeout: A duration of time in seconds to allow for the RPC.
+      metadata: A metadata value to be passed to the service-side of
+        the RPC.
+      protocol_options: A value specified by the provider of a Face interface
+        implementation affording custom state and behavior.
+
+    Returns:
+      An object that is both a Call for the RPC and a future.Future. In the
+        event of RPC completion, the return Future's result value will be the
+        response value of the RPC. In the event of RPC abortion, the returned
+        Future's exception value will be an AbortionError.
+    """
+    raise NotImplementedError()
+
+  @abc.abstractmethod
+  def event(
+      self, request, receiver, abortion_callback, timeout,
+      metadata=None, protocol_options=None):
+    """Asynchronously invokes the underlying RPC.
+
+    Args:
+      request: The request value for the RPC.
+      receiver: A ResponseReceiver to be passed the response data of the RPC.
+      abortion_callback: A callback to be called and passed an Abortion value
+        in the event of RPC abortion.
+      timeout: A duration of time in seconds to allow for the RPC.
+      metadata: A metadata value to be passed to the service-side of
+        the RPC.
+      protocol_options: A value specified by the provider of a Face interface
+        implementation affording custom state and behavior.
+
+    Returns:
+      A Call for the RPC.
+    """
+    raise NotImplementedError()
+
+
+class UnaryStreamMultiCallable(object):
+  """Affords invoking a unary-stream RPC in any call style."""
+  __metaclass__ = abc.ABCMeta
+
+  @abc.abstractmethod
+  def __call__(self, request, timeout, metadata=None, protocol_options=None):
+    """Invokes the underlying RPC.
+
+    Args:
+      request: The request value for the RPC.
+      timeout: A duration of time in seconds to allow for the RPC.
+      metadata: A metadata value to be passed to the service-side of
+        the RPC.
+      protocol_options: A value specified by the provider of a Face interface
+        implementation affording custom state and behavior.
+
+    Returns:
+      An object that is both a Call for the RPC and an iterator of response
+        values. Drawing response values from the returned iterator may raise
+        AbortionError indicating abortion of the RPC.
+    """
+    raise NotImplementedError()
+
+  @abc.abstractmethod
+  def event(
+      self, request, receiver, abortion_callback, timeout,
+      metadata=None, protocol_options=None):
+    """Asynchronously invokes the underlying RPC.
+
+    Args:
+      request: The request value for the RPC.
+      receiver: A ResponseReceiver to be passed the response data of the RPC.
+      abortion_callback: A callback to be called and passed an Abortion value
+        in the event of RPC abortion.
+      timeout: A duration of time in seconds to allow for the RPC.
+      metadata: A metadata value to be passed to the service-side of
+        the RPC.
+      protocol_options: A value specified by the provider of a Face interface
+        implementation affording custom state and behavior.
+
+    Returns:
+      A Call object for the RPC.
+    """
+    raise NotImplementedError()
+
+
+class StreamUnaryMultiCallable(object):
+  """Affords invoking a stream-unary RPC in any call style."""
+  __metaclass__ = abc.ABCMeta
+
+  @abc.abstractmethod
+  def __call__(
+      self, request_iterator, timeout, metadata=None,
+      with_call=False, protocol_options=None):
+    """Synchronously invokes the underlying RPC.
+
+    Args:
+      request_iterator: An iterator that yields request values for the RPC.
+      timeout: A duration of time in seconds to allow for the RPC.
+      metadata: A metadata value to be passed to the service-side of
+        the RPC.
+      with_call: Whether or not to include return a Call for the RPC in addition
+        to the response.
+      protocol_options: A value specified by the provider of a Face interface
+        implementation affording custom state and behavior.
+
+    Returns:
+      The response value for the RPC, and a Call for the RPC if with_call was
+        set to True at invocation.
+
+    Raises:
+      AbortionError: Indicating that the RPC was aborted.
+    """
+    raise NotImplementedError()
+
+  @abc.abstractmethod
+  def future(
+      self, request_iterator, timeout, metadata=None, protocol_options=None):
+    """Asynchronously invokes the underlying RPC.
+
+    Args:
+      request_iterator: An iterator that yields request values for the RPC.
+      timeout: A duration of time in seconds to allow for the RPC.
+      metadata: A metadata value to be passed to the service-side of
+        the RPC.
+      protocol_options: A value specified by the provider of a Face interface
+        implementation affording custom state and behavior.
+
+    Returns:
+      An object that is both a Call for the RPC and a future.Future. In the
+        event of RPC completion, the return Future's result value will be the
+        response value of the RPC. In the event of RPC abortion, the returned
+        Future's exception value will be an AbortionError.
+    """
+    raise NotImplementedError()
+
+  @abc.abstractmethod
+  def event(
+      self, receiver, abortion_callback, timeout, metadata=None,
+      protocol_options=None):
+    """Asynchronously invokes the underlying RPC.
+
+    Args:
+      receiver: A ResponseReceiver to be passed the response data of the RPC.
+      abortion_callback: A callback to be called and passed an Abortion value
+        in the event of RPC abortion.
+      timeout: A duration of time in seconds to allow for the RPC.
+      metadata: A metadata value to be passed to the service-side of
+        the RPC.
+      protocol_options: A value specified by the provider of a Face interface
+        implementation affording custom state and behavior.
+
+    Returns:
+      A single object that is both a Call object for the RPC and a
+        stream.Consumer to which the request values of the RPC should be passed.
+    """
+    raise NotImplementedError()
+
+
+class StreamStreamMultiCallable(object):
+  """Affords invoking a stream-stream RPC in any call style."""
+  __metaclass__ = abc.ABCMeta
+
+  @abc.abstractmethod
+  def __call__(
+      self, request_iterator, timeout, metadata=None, protocol_options=None):
+    """Invokes the underlying RPC.
+
+    Args:
+      request_iterator: An iterator that yields request values for the RPC.
+      timeout: A duration of time in seconds to allow for the RPC.
+      metadata: A metadata value to be passed to the service-side of
+        the RPC.
+      protocol_options: A value specified by the provider of a Face interface
+        implementation affording custom state and behavior.
+
+    Returns:
+      An object that is both a Call for the RPC and an iterator of response
+        values. Drawing response values from the returned iterator may raise
+        AbortionError indicating abortion of the RPC.
+    """
+    raise NotImplementedError()
+
+  @abc.abstractmethod
+  def event(
+      self, receiver, abortion_callback, timeout, metadata=None,
+      protocol_options=None):
+    """Asynchronously invokes the underlying RPC.
+
+    Args:
+      receiver: A ResponseReceiver to be passed the response data of the RPC.
+      abortion_callback: A callback to be called and passed an Abortion value
+        in the event of RPC abortion.
+      timeout: A duration of time in seconds to allow for the RPC.
+      metadata: A metadata value to be passed to the service-side of
+        the RPC.
+      protocol_options: A value specified by the provider of a Face interface
+        implementation affording custom state and behavior.
+
+    Returns:
+      A single object that is both a Call object for the RPC and a
+        stream.Consumer to which the request values of the RPC should be passed.
+    """
+    raise NotImplementedError()
+
+
+class MethodImplementation(object):
+  """A sum type that describes a method implementation.
+
+  Attributes:
+    cardinality: A cardinality.Cardinality value.
+    style: A style.Service value.
+    unary_unary_inline: The implementation of the method as a callable value
+      that takes a request value and a ServicerContext object and returns a
+      response value. Only non-None if cardinality is
+      cardinality.Cardinality.UNARY_UNARY and style is style.Service.INLINE.
+    unary_stream_inline: The implementation of the method as a callable value
+      that takes a request value and a ServicerContext object and returns an
+      iterator of response values. Only non-None if cardinality is
+      cardinality.Cardinality.UNARY_STREAM and style is style.Service.INLINE.
+    stream_unary_inline: The implementation of the method as a callable value
+      that takes an iterator of request values and a ServicerContext object and
+      returns a response value. Only non-None if cardinality is
+      cardinality.Cardinality.STREAM_UNARY and style is style.Service.INLINE.
+    stream_stream_inline: The implementation of the method as a callable value
+      that takes an iterator of request values and a ServicerContext object and
+      returns an iterator of response values. Only non-None if cardinality is
+      cardinality.Cardinality.STREAM_STREAM and style is style.Service.INLINE.
+    unary_unary_event: The implementation of the method as a callable value that
+      takes a request value, a response callback to which to pass the response
+      value of the RPC, and a ServicerContext. Only non-None if cardinality is
+      cardinality.Cardinality.UNARY_UNARY and style is style.Service.EVENT.
+    unary_stream_event: The implementation of the method as a callable value
+      that takes a request value, a stream.Consumer to which to pass the
+      response values of the RPC, and a ServicerContext. Only non-None if
+      cardinality is cardinality.Cardinality.UNARY_STREAM and style is
+      style.Service.EVENT.
+    stream_unary_event: The implementation of the method as a callable value
+      that takes a response callback to which to pass the response value of the
+      RPC and a ServicerContext and returns a stream.Consumer to which the
+      request values of the RPC should be passed. Only non-None if cardinality
+      is cardinality.Cardinality.STREAM_UNARY and style is style.Service.EVENT.
+    stream_stream_event: The implementation of the method as a callable value
+      that takes a stream.Consumer to which to pass the response values of the
+      RPC and a ServicerContext and returns a stream.Consumer to which the
+      request values of the RPC should be passed. Only non-None if cardinality
+      is cardinality.Cardinality.STREAM_STREAM and style is
+      style.Service.EVENT.
+  """
+  __metaclass__ = abc.ABCMeta
+
+
+class MultiMethodImplementation(object):
+  """A general type able to service many methods."""
+  __metaclass__ = abc.ABCMeta
+
+  @abc.abstractmethod
+  def service(self, group, method, response_consumer, context):
+    """Services an RPC.
+
+    Args:
+      group: The group identifier of the RPC.
+      method: The method identifier of the RPC.
+      response_consumer: A stream.Consumer to be called to accept the response
+        values of the RPC.
+      context: a ServicerContext object.
+
+    Returns:
+      A stream.Consumer with which to accept the request values of the RPC. The
+        consumer returned from this method may or may not be invoked to
+        completion: in the case of RPC abortion, RPC Framework will simply stop
+        passing values to this object. Implementations must not assume that this
+        object will be called to completion of the request stream or even called
+        at all.
+
+    Raises:
+      abandonment.Abandoned: May or may not be raised when the RPC has been
+        aborted.
+      NoSuchMethodError: If this MultiMethod does not recognize the given group
+        and name for the RPC and is not able to service the RPC.
+    """
+    raise NotImplementedError()
+
+
+class GenericStub(object):
+  """Affords RPC invocation via generic methods."""
+  __metaclass__ = abc.ABCMeta
+
+  @abc.abstractmethod
+  def blocking_unary_unary(
+      self, group, method, request, timeout, metadata=None,
+      with_call=False, protocol_options=None):
+    """Invokes a unary-request-unary-response method.
+
+    This method blocks until either returning the response value of the RPC
+    (in the event of RPC completion) or raising an exception (in the event of
+    RPC abortion).
+
+    Args:
+      group: The group identifier of the RPC.
+      method: The method identifier of the RPC.
+      request: The request value for the RPC.
+      timeout: A duration of time in seconds to allow for the RPC.
+      metadata: A metadata value to be passed to the service-side of the RPC.
+      with_call: Whether or not to include return a Call for the RPC in addition
+        to the response.
+      protocol_options: A value specified by the provider of a Face interface
+        implementation affording custom state and behavior.
+
+    Returns:
+      The response value for the RPC, and a Call for the RPC if with_call was
+        set to True at invocation.
+
+    Raises:
+      AbortionError: Indicating that the RPC was aborted.
+    """
+    raise NotImplementedError()
+
+  @abc.abstractmethod
+  def future_unary_unary(
+      self, group, method, request, timeout, metadata=None,
+      protocol_options=None):
+    """Invokes a unary-request-unary-response method.
+
+    Args:
+      group: The group identifier of the RPC.
+      method: The method identifier of the RPC.
+      request: The request value for the RPC.
+      timeout: A duration of time in seconds to allow for the RPC.
+      metadata: A metadata value to be passed to the service-side of the RPC.
+      protocol_options: A value specified by the provider of a Face interface
+        implementation affording custom state and behavior.
+
+    Returns:
+      An object that is both a Call for the RPC and a future.Future. In the
+        event of RPC completion, the return Future's result value will be the
+        response value of the RPC. In the event of RPC abortion, the returned
+        Future's exception value will be an AbortionError.
+    """
+    raise NotImplementedError()
+
+  @abc.abstractmethod
+  def inline_unary_stream(
+      self, group, method, request, timeout, metadata=None,
+      protocol_options=None):
+    """Invokes a unary-request-stream-response method.
+
+    Args:
+      group: The group identifier of the RPC.
+      method: The method identifier of the RPC.
+      request: The request value for the RPC.
+      timeout: A duration of time in seconds to allow for the RPC.
+      metadata: A metadata value to be passed to the service-side of the RPC.
+      protocol_options: A value specified by the provider of a Face interface
+        implementation affording custom state and behavior.
+
+    Returns:
+      An object that is both a Call for the RPC and an iterator of response
+        values. Drawing response values from the returned iterator may raise
+        AbortionError indicating abortion of the RPC.
+    """
+    raise NotImplementedError()
+
+  @abc.abstractmethod
+  def blocking_stream_unary(
+      self, group, method, request_iterator, timeout, metadata=None,
+      with_call=False, protocol_options=None):
+    """Invokes a stream-request-unary-response method.
+
+    This method blocks until either returning the response value of the RPC
+    (in the event of RPC completion) or raising an exception (in the event of
+    RPC abortion).
+
+    Args:
+      group: The group identifier of the RPC.
+      method: The method identifier of the RPC.
+      request_iterator: An iterator that yields request values for the RPC.
+      timeout: A duration of time in seconds to allow for the RPC.
+      metadata: A metadata value to be passed to the service-side of the RPC.
+      with_call: Whether or not to include return a Call for the RPC in addition
+        to the response.
+      protocol_options: A value specified by the provider of a Face interface
+        implementation affording custom state and behavior.
+
+    Returns:
+      The response value for the RPC, and a Call for the RPC if with_call was
+        set to True at invocation.
+
+    Raises:
+      AbortionError: Indicating that the RPC was aborted.
+    """
+    raise NotImplementedError()
+
+  @abc.abstractmethod
+  def future_stream_unary(
+      self, group, method, request_iterator, timeout, metadata=None,
+      protocol_options=None):
+    """Invokes a stream-request-unary-response method.
+
+    Args:
+      group: The group identifier of the RPC.
+      method: The method identifier of the RPC.
+      request_iterator: An iterator that yields request values for the RPC.
+      timeout: A duration of time in seconds to allow for the RPC.
+      metadata: A metadata value to be passed to the service-side of the RPC.
+      protocol_options: A value specified by the provider of a Face interface
+        implementation affording custom state and behavior.
+
+    Returns:
+      An object that is both a Call for the RPC and a future.Future. In the
+        event of RPC completion, the return Future's result value will be the
+        response value of the RPC. In the event of RPC abortion, the returned
+        Future's exception value will be an AbortionError.
+    """
+    raise NotImplementedError()
+
+  @abc.abstractmethod
+  def inline_stream_stream(
+      self, group, method, request_iterator, timeout, metadata=None,
+      protocol_options=None):
+    """Invokes a stream-request-stream-response method.
+
+    Args:
+      group: The group identifier of the RPC.
+      method: The method identifier of the RPC.
+      request_iterator: An iterator that yields request values for the RPC.
+      timeout: A duration of time in seconds to allow for the RPC.
+      metadata: A metadata value to be passed to the service-side of the RPC.
+      protocol_options: A value specified by the provider of a Face interface
+        implementation affording custom state and behavior.
+
+    Returns:
+      An object that is both a Call for the RPC and an iterator of response
+        values. Drawing response values from the returned iterator may raise
+        AbortionError indicating abortion of the RPC.
+    """
+    raise NotImplementedError()
+
+  @abc.abstractmethod
+  def event_unary_unary(
+      self, group, method, request, receiver, abortion_callback, timeout,
+      metadata=None, protocol_options=None):
+    """Event-driven invocation of a unary-request-unary-response method.
+
+    Args:
+      group: The group identifier of the RPC.
+      method: The method identifier of the RPC.
+      request: The request value for the RPC.
+      receiver: A ResponseReceiver to be passed the response data of the RPC.
+      abortion_callback: A callback to be called and passed an Abortion value
+        in the event of RPC abortion.
+      timeout: A duration of time in seconds to allow for the RPC.
+      metadata: A metadata value to be passed to the service-side of the RPC.
+      protocol_options: A value specified by the provider of a Face interface
+        implementation affording custom state and behavior.
+
+    Returns:
+      A Call for the RPC.
+    """
+    raise NotImplementedError()
+
+  @abc.abstractmethod
+  def event_unary_stream(
+      self, group, method, request, receiver, abortion_callback, timeout,
+      metadata=None, protocol_options=None):
+    """Event-driven invocation of a unary-request-stream-response method.
+
+    Args:
+      group: The group identifier of the RPC.
+      method: The method identifier of the RPC.
+      request: The request value for the RPC.
+      receiver: A ResponseReceiver to be passed the response data of the RPC.
+      abortion_callback: A callback to be called and passed an Abortion value
+        in the event of RPC abortion.
+      timeout: A duration of time in seconds to allow for the RPC.
+      metadata: A metadata value to be passed to the service-side of the RPC.
+      protocol_options: A value specified by the provider of a Face interface
+        implementation affording custom state and behavior.
+
+    Returns:
+      A Call for the RPC.
+    """
+    raise NotImplementedError()
+
+  @abc.abstractmethod
+  def event_stream_unary(
+      self, group, method, receiver, abortion_callback, timeout,
+      metadata=None, protocol_options=None):
+    """Event-driven invocation of a unary-request-unary-response method.
+
+    Args:
+      group: The group identifier of the RPC.
+      method: The method identifier of the RPC.
+      receiver: A ResponseReceiver to be passed the response data of the RPC.
+      abortion_callback: A callback to be called and passed an Abortion value
+        in the event of RPC abortion.
+      timeout: A duration of time in seconds to allow for the RPC.
+      metadata: A metadata value to be passed to the service-side of the RPC.
+      protocol_options: A value specified by the provider of a Face interface
+        implementation affording custom state and behavior.
+
+    Returns:
+      A pair of a Call object for the RPC and a stream.Consumer to which the
+        request values of the RPC should be passed.
+    """
+    raise NotImplementedError()
+
+  @abc.abstractmethod
+  def event_stream_stream(
+      self, group, method, receiver, abortion_callback, timeout,
+      metadata=None, protocol_options=None):
+    """Event-driven invocation of a unary-request-stream-response method.
+
+    Args:
+      group: The group identifier of the RPC.
+      method: The method identifier of the RPC.
+      receiver: A ResponseReceiver to be passed the response data of the RPC.
+      abortion_callback: A callback to be called and passed an Abortion value
+        in the event of RPC abortion.
+      timeout: A duration of time in seconds to allow for the RPC.
+      metadata: A metadata value to be passed to the service-side of the RPC.
+      protocol_options: A value specified by the provider of a Face interface
+        implementation affording custom state and behavior.
+
+    Returns:
+      A pair of a Call object for the RPC and a stream.Consumer to which the
+        request values of the RPC should be passed.
+    """
+    raise NotImplementedError()
+
+  @abc.abstractmethod
+  def unary_unary(self, group, method):
+    """Creates a UnaryUnaryMultiCallable for a unary-unary method.
+
+    Args:
+      group: The group identifier of the RPC.
+      method: The method identifier of the RPC.
+
+    Returns:
+      A UnaryUnaryMultiCallable value for the named unary-unary method.
+    """
+    raise NotImplementedError()
+
+  @abc.abstractmethod
+  def unary_stream(self, group, method):
+    """Creates a UnaryStreamMultiCallable for a unary-stream method.
+
+    Args:
+      group: The group identifier of the RPC.
+      method: The method identifier of the RPC.
+
+    Returns:
+      A UnaryStreamMultiCallable value for the name unary-stream method.
+    """
+    raise NotImplementedError()
+
+  @abc.abstractmethod
+  def stream_unary(self, group, method):
+    """Creates a StreamUnaryMultiCallable for a stream-unary method.
+
+    Args:
+      group: The group identifier of the RPC.
+      method: The method identifier of the RPC.
+
+    Returns:
+      A StreamUnaryMultiCallable value for the named stream-unary method.
+    """
+    raise NotImplementedError()
+
+  @abc.abstractmethod
+  def stream_stream(self, group, method):
+    """Creates a StreamStreamMultiCallable for a stream-stream method.
+
+    Args:
+      group: The group identifier of the RPC.
+      method: The method identifier of the RPC.
+
+    Returns:
+      A StreamStreamMultiCallable value for the named stream-stream method.
+    """
+    raise NotImplementedError()
+
+
+class DynamicStub(object):
+  """Affords RPC invocation via attributes corresponding to afforded methods.
+
+  Instances of this type may be scoped to a single group so that attribute
+  access is unambiguous.
+
+  Instances of this type respond to attribute access as follows: if the
+  requested attribute is the name of a unary-unary method, the value of the
+  attribute will be a UnaryUnaryMultiCallable with which to invoke an RPC; if
+  the requested attribute is the name of a unary-stream method, the value of the
+  attribute will be a UnaryStreamMultiCallable with which to invoke an RPC; if
+  the requested attribute is the name of a stream-unary method, the value of the
+  attribute will be a StreamUnaryMultiCallable with which to invoke an RPC; and
+  if the requested attribute is the name of a stream-stream method, the value of
+  the attribute will be a StreamStreamMultiCallable with which to invoke an RPC.
+  """
+  __metaclass__ = abc.ABCMeta