Initial checkin of gRPC to third_party/

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

Index: third_party/grpc/src/python/grpcio/grpc/framework/interfaces/base/base.py
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+# Copyright 2015, 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.
+
+"""The base interface of RPC Framework.
+
+Implementations of this interface support the conduct of "operations":
+exchanges between two distinct ends of an arbitrary number of data payloads
+and metadata such as a name for the operation, initial and terminal metadata
+in each direction, and flow control. These operations may be used for transfers
+of data, remote procedure calls, status indication, or anything else
+applications choose.
+"""
+
+# threading is referenced from specification in this module.
+import abc
+import enum
+import threading  # pylint: disable=unused-import
+
+# abandonment is referenced from specification in this module.
+from grpc.framework.foundation import abandonment  # pylint: disable=unused-import
+
+
+class NoSuchMethodError(Exception):
+  """Indicates that an unrecognized operation has been called.
+
+  Attributes:
+    code: A code value to communicate to the other side of the operation along
+      with indication of operation termination. May be None.
+    details: A details value to communicate to the other side of the operation
+      along with indication of operation termination. May be None.
+  """
+
+  def __init__(self, code, details):
+    """Constructor.
+
+    Args:
+      code: A code value to communicate to the other side of the operation
+        along with indication of operation termination. May be None.
+      details: A details value to communicate to the other side of the
+        operation along with indication of operation termination. May be None.
+    """
+    self.code = code
+    self.details = details
+
+
+class Outcome(object):
+  """The outcome of an operation.
+
+  Attributes:
+    kind: A Kind value coarsely identifying how the operation terminated.
+    code: An application-specific code value or None if no such value was
+      provided.
+    details: An application-specific details value or None if no such value was
+      provided.
+  """
+
+  @enum.unique
+  class Kind(enum.Enum):
+    """Ways in which an operation can terminate."""
+
+    COMPLETED = 'completed'
+    CANCELLED = 'cancelled'
+    EXPIRED = 'expired'
+    LOCAL_SHUTDOWN = 'local shutdown'
+    REMOTE_SHUTDOWN = 'remote shutdown'
+    RECEPTION_FAILURE = 'reception failure'
+    TRANSMISSION_FAILURE = 'transmission failure'
+    LOCAL_FAILURE = 'local failure'
+    REMOTE_FAILURE = 'remote failure'
+
+
+class Completion(object):
+  """An aggregate of the values exchanged upon operation completion.
+
+  Attributes:
+    terminal_metadata: A terminal metadata value for the operaton.
+    code: A code value for the operation.
+    message: A message value for the operation.
+  """
+  __metaclass__ = abc.ABCMeta
+
+
+class OperationContext(object):
+  """Provides operation-related information and action."""
+  __metaclass__ = abc.ABCMeta
+
+  @abc.abstractmethod
+  def outcome(self):
+    """Indicates the operation's outcome (or that the operation is ongoing).
+
+    Returns:
+      None if the operation is still active or the Outcome value for the
+        operation if it has terminated.
+    """
+    raise NotImplementedError()
+
+  @abc.abstractmethod
+  def add_termination_callback(self, callback):
+    """Adds a function to be called upon operation termination.
+
+    Args:
+      callback: A callable to be passed an Outcome value on operation
+        termination.
+
+    Returns:
+      None if the operation has not yet terminated and the passed callback will
+        later be called when it does terminate, or if the operation has already
+        terminated an Outcome value describing the operation termination and the
+        passed callback will not be called as a result of this method call.
+    """
+    raise NotImplementedError()
+
+  @abc.abstractmethod
+  def time_remaining(self):
+    """Describes the length of allowed time remaining for the operation.
+
+    Returns:
+      A nonnegative float indicating the length of allowed time in seconds
+      remaining for the operation to complete before it is considered to have
+      timed out. Zero is returned if the operation has terminated.
+    """
+    raise NotImplementedError()
+
+  @abc.abstractmethod
+  def cancel(self):
+    """Cancels the operation if the operation has not yet terminated."""
+    raise NotImplementedError()
+
+  @abc.abstractmethod
+  def fail(self, exception):
+    """Indicates that the operation has failed.
+
+    Args:
+      exception: An exception germane to the operation failure. May be None.
+    """
+    raise NotImplementedError()
+
+
+class Operator(object):
+  """An interface through which to participate in an operation."""
+  __metaclass__ = abc.ABCMeta
+
+  @abc.abstractmethod
+  def advance(
+      self, initial_metadata=None, payload=None, completion=None,
+      allowance=None):
+    """Progresses the operation.
+
+    Args:
+      initial_metadata: An initial metadata value. Only one may ever be
+        communicated in each direction for an operation, and they must be
+        communicated no later than either the first payload or the completion.
+      payload: A payload value.
+      completion: A Completion value. May only ever be non-None once in either
+        direction, and no payloads may be passed after it has been communicated.
+      allowance: A positive integer communicating the number of additional
+        payloads allowed to be passed by the remote side of the operation.
+    """
+    raise NotImplementedError()
+
+class ProtocolReceiver(object):
+  """A means of receiving protocol values during an operation."""
+  __metaclass__ = abc.ABCMeta
+
+  @abc.abstractmethod
+  def context(self, protocol_context):
+    """Accepts the protocol context object for the operation.
+
+    Args:
+      protocol_context: The protocol context object for the operation.
+    """
+    raise NotImplementedError()
+
+
+class Subscription(object):
+  """Describes customer code's interest in values from the other side.
+
+  Attributes:
+    kind: A Kind value describing the overall kind of this value.
+    termination_callback: A callable to be passed the Outcome associated with
+      the operation after it has terminated. Must be non-None if kind is
+      Kind.TERMINATION_ONLY. Must be None otherwise.
+    allowance: A callable behavior that accepts positive integers representing
+      the number of additional payloads allowed to be passed to the other side
+      of the operation. Must be None if kind is Kind.FULL. Must not be None
+      otherwise.
+    operator: An Operator to be passed values from the other side of the
+      operation. Must be non-None if kind is Kind.FULL. Must be None otherwise.
+    protocol_receiver: A ProtocolReceiver to be passed protocol objects as they
+      become available during the operation. Must be non-None if kind is
+      Kind.FULL.
+  """
+  __metaclass__ = abc.ABCMeta
+
+  @enum.unique
+  class Kind(enum.Enum):
+
+    NONE = 'none'
+    TERMINATION_ONLY = 'termination only'
+    FULL = 'full'
+
+
+class Servicer(object):
+  """Interface for service implementations."""
+  __metaclass__ = abc.ABCMeta
+
+  @abc.abstractmethod
+  def service(self, group, method, context, output_operator):
+    """Services an operation.
+
+    Args:
+      group: The group identifier of the operation to be serviced.
+      method: The method identifier of the operation to be serviced.
+      context: An OperationContext object affording contextual information and
+        actions.
+      output_operator: An Operator that will accept output values of the
+        operation.
+
+    Returns:
+      A Subscription via which this object may or may not accept more values of
+        the operation.
+
+    Raises:
+      NoSuchMethodError: If this Servicer does not handle operations with the
+        given group and method.
+      abandonment.Abandoned: If the operation has been aborted and there no
+        longer is any reason to service the operation.
+    """
+    raise NotImplementedError()
+
+
+class End(object):
+  """Common type for entry-point objects on both sides of an operation."""
+  __metaclass__ = abc.ABCMeta
+
+  @abc.abstractmethod
+  def start(self):
+    """Starts this object's service of operations."""
+    raise NotImplementedError()
+
+  @abc.abstractmethod
+  def stop(self, grace):
+    """Stops this object's service of operations.
+
+    This object will refuse service of new operations as soon as this method is
+    called but operations under way at the time of the call may be given a
+    grace period during which they are allowed to finish.
+
+    Args:
+      grace: A duration of time in seconds to allow ongoing operations to
+        terminate before being forcefully terminated by the stopping of this
+        End. May be zero to terminate all ongoing operations and immediately
+        stop.
+
+    Returns:
+      A threading.Event that will be set to indicate all operations having
+        terminated and this End having completely stopped. The returned event
+        may not be set until after the full grace period (if some ongoing
+        operation continues for the full length of the period) or it may be set
+        much sooner (if for example this End had no operations in progress at
+        the time its stop method was called).
+    """
+    raise NotImplementedError()
+
+  @abc.abstractmethod
+  def operate(
+      self, group, method, subscription, timeout, initial_metadata=None,
+      payload=None, completion=None, protocol_options=None):
+    """Commences an operation.
+
+    Args:
+      group: The group identifier of the invoked operation.
+      method: The method identifier of the invoked operation.
+      subscription: A Subscription to which the results of the operation will be
+        passed.
+      timeout: A length of time in seconds to allow for the operation.
+      initial_metadata: An initial metadata value to be sent to the other side
+        of the operation. May be None if the initial metadata will be later
+        passed via the returned operator or if there will be no initial metadata
+        passed at all.
+      payload: An initial payload for the operation.
+      completion: A Completion value indicating the end of transmission to the
+        other side of the operation.
+      protocol_options: A value specified by the provider of a Base interface
+        implementation affording custom state and behavior.
+
+    Returns:
+      A pair of objects affording information about the operation and action
+        continuing the operation. The first element of the returned pair is an
+        OperationContext for the operation and the second element of the
+        returned pair is an Operator to which operation values not passed in
+        this call should later be passed.
+    """
+    raise NotImplementedError()
+
+  @abc.abstractmethod
+  def operation_stats(self):
+    """Reports the number of terminated operations broken down by outcome.
+
+    Returns:
+      A dictionary from Outcome.Kind value to an integer identifying the number
+        of operations that terminated with that outcome kind.
+    """
+    raise NotImplementedError()
+
+  @abc.abstractmethod
+  def add_idle_action(self, action):
+    """Adds an action to be called when this End has no ongoing operations.
+
+    Args:
+      action: A callable that accepts no arguments.
+    """
+    raise NotImplementedError()