src/python/grpcio/grpc/beta/_server_adaptations.py

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"""Translates gRPC's server-side API into gRPC's server-side Beta API."""

import collections
import threading

import grpc
from grpc.beta import interfaces
from grpc.framework.common import cardinality
from grpc.framework.common import style
from grpc.framework.foundation import abandonment
from grpc.framework.foundation import logging_pool
from grpc.framework.foundation import stream
from grpc.framework.interfaces.face import face

_DEFAULT_POOL_SIZE = 8


class _ServerProtocolContext(interfaces.GRPCServicerContext):

  def __init__(self, servicer_context):
    self._servicer_context = servicer_context

  def peer(self):
    return self._servicer_context.peer()

  def disable_next_response_compression(self):
    pass  # TODO(https://github.com/grpc/grpc/issues/4078): design, implement.


class _FaceServicerContext(face.ServicerContext):

  def __init__(self, servicer_context):
    self._servicer_context = servicer_context

  def is_active(self):
    return self._servicer_context.is_active()

  def time_remaining(self):
    return self._servicer_context.time_remaining()

  def add_abortion_callback(self, abortion_callback):
    raise NotImplementedError(
        'add_abortion_callback no longer supported server-side!')

  def cancel(self):
    self._servicer_context.cancel()

  def protocol_context(self):
    return _ServerProtocolContext(self._servicer_context)

  def invocation_metadata(self):
    return self._servicer_context.invocation_metadata()

  def initial_metadata(self, initial_metadata):
    self._servicer_context.send_initial_metadata(initial_metadata)

  def terminal_metadata(self, terminal_metadata):
    self._servicer_context.set_terminal_metadata(terminal_metadata)

  def code(self, code):
    self._servicer_context.set_code(code)

  def details(self, details):
    self._servicer_context.set_details(details)


def _adapt_unary_request_inline(unary_request_inline):
  def adaptation(request, servicer_context):
    return unary_request_inline(request, _FaceServicerContext(servicer_context))
  return adaptation


def _adapt_stream_request_inline(stream_request_inline):
  def adaptation(request_iterator, servicer_context):
    return stream_request_inline(
        request_iterator, _FaceServicerContext(servicer_context))
  return adaptation


class _Callback(stream.Consumer):

  def __init__(self):
    self._condition = threading.Condition()
    self._values = []
    self._terminated = False
    self._cancelled = False

  def consume(self, value):
    with self._condition:
      self._values.append(value)
      self._condition.notify_all()

  def terminate(self):
    with self._condition:
      self._terminated = True
      self._condition.notify_all()

  def consume_and_terminate(self, value):
    with self._condition:
      self._values.append(value)
      self._terminated = True
      self._condition.notify_all()

  def cancel(self):
    with self._condition:
      self._cancelled = True
      self._condition.notify_all()

  def draw_one_value(self):
    with self._condition:
      while True:
        if self._cancelled:
          raise abandonment.Abandoned()
        elif self._values:
          return self._values.pop(0)
        elif self._terminated:
          return None
        else:
          self._condition.wait()

  def draw_all_values(self):
    with self._condition:
      while True:
        if self._cancelled:
          raise abandonment.Abandoned()
        elif self._terminated:
          all_values = tuple(self._values)
          self._values = None
          return all_values
        else:
          self._condition.wait()


def _pipe_requests(request_iterator, request_consumer, servicer_context):
  for request in request_iterator:
    if not servicer_context.is_active():
      return
    request_consumer.consume(request)
    if not servicer_context.is_active():
      return
  request_consumer.terminate()


def _adapt_unary_unary_event(unary_unary_event):
  def adaptation(request, servicer_context):
    callback = _Callback()
    if not servicer_context.add_callback(callback.cancel):
      raise abandonment.Abandoned()
    unary_unary_event(
        request, callback.consume_and_terminate,
        _FaceServicerContext(servicer_context))
    return callback.draw_all_values()[0]
  return adaptation


def _adapt_unary_stream_event(unary_stream_event):
  def adaptation(request, servicer_context):
    callback = _Callback()
    if not servicer_context.add_callback(callback.cancel):
      raise abandonment.Abandoned()
    unary_stream_event(
        request, callback, _FaceServicerContext(servicer_context))
    while True:
      response = callback.draw_one_value()
      if response is None:
        return
      else:
        yield response
  return adaptation


def _adapt_stream_unary_event(stream_unary_event):
  def adaptation(request_iterator, servicer_context):
    callback = _Callback()
    if not servicer_context.add_callback(callback.cancel):
      raise abandonment.Abandoned()
    request_consumer = stream_unary_event(
        callback.consume_and_terminate, _FaceServicerContext(servicer_context))
    request_pipe_thread = threading.Thread(
        target=_pipe_requests,
        args=(request_iterator, request_consumer, servicer_context,))
    request_pipe_thread.start()
    return callback.draw_all_values()[0]
  return adaptation


def _adapt_stream_stream_event(stream_stream_event):
  def adaptation(request_iterator, servicer_context):
    callback = _Callback()
    if not servicer_context.add_callback(callback.cancel):
      raise abandonment.Abandoned()
    request_consumer = stream_stream_event(
        callback, _FaceServicerContext(servicer_context))
    request_pipe_thread = threading.Thread(
        target=_pipe_requests,
        args=(request_iterator, request_consumer, servicer_context,))
    request_pipe_thread.start()
    while True:
      response = callback.draw_one_value()
      if response is None:
        return
      else:
        yield response
  return adaptation


class _SimpleMethodHandler(
    collections.namedtuple(
        '_MethodHandler',
        ('request_streaming', 'response_streaming', 'request_deserializer',
         'response_serializer', 'unary_unary', 'unary_stream', 'stream_unary',
         'stream_stream',)),
    grpc.RpcMethodHandler):
  pass


def _simple_method_handler(
    implementation, request_deserializer, response_serializer):
  if implementation.style is style.Service.INLINE:
    if implementation.cardinality is cardinality.Cardinality.UNARY_UNARY:
      return _SimpleMethodHandler(
          False, False, request_deserializer, response_serializer,
          _adapt_unary_request_inline(implementation.unary_unary_inline), None,
          None, None)
    elif implementation.cardinality is cardinality.Cardinality.UNARY_STREAM:
      return _SimpleMethodHandler(
          False, True, request_deserializer, response_serializer, None,
          _adapt_unary_request_inline(implementation.unary_stream_inline), None,
          None)
    elif implementation.cardinality is cardinality.Cardinality.STREAM_UNARY:
      return _SimpleMethodHandler(
          True, False, request_deserializer, response_serializer, None, None,
          _adapt_stream_request_inline(implementation.stream_unary_inline),
          None)
    elif implementation.cardinality is cardinality.Cardinality.STREAM_STREAM:
      return _SimpleMethodHandler(
          True, True, request_deserializer, response_serializer, None, None,
          None,
          _adapt_stream_request_inline(implementation.stream_stream_inline))
  elif implementation.style is style.Service.EVENT:
    if implementation.cardinality is cardinality.Cardinality.UNARY_UNARY:
      return _SimpleMethodHandler(
          False, False, request_deserializer, response_serializer,
          _adapt_unary_unary_event(implementation.unary_unary_event), None,
          None, None)
    elif implementation.cardinality is cardinality.Cardinality.UNARY_STREAM:
      return _SimpleMethodHandler(
          False, True, request_deserializer, response_serializer, None,
          _adapt_unary_stream_event(implementation.unary_stream_event), None,
          None)
    elif implementation.cardinality is cardinality.Cardinality.STREAM_UNARY:
      return _SimpleMethodHandler(
          True, False, request_deserializer, response_serializer, None, None,
          _adapt_stream_unary_event(implementation.stream_unary_event), None)
    elif implementation.cardinality is cardinality.Cardinality.STREAM_STREAM:
      return _SimpleMethodHandler(
          True, True, request_deserializer, response_serializer, None, None,
          None, _adapt_stream_stream_event(implementation.stream_stream_event))


class _GenericRpcHandler(grpc.GenericRpcHandler):

  def __init__(
      self, method_implementations, multi_method_implementation,
      request_deserializers, response_serializers):
    self._method_implementations = method_implementations
    self._multi_method_implementation = multi_method_implementation
    self._request_deserializers = request_deserializers or {}
    self._response_serializers = response_serializers or {}

  def service(self, handler_call_details):
    try:
      group_name, method_name = handler_call_details.method.split(b'/')[1:3]
    except ValueError:
      return None
    else:
      method_implementation = self._method_implementations.get(
          (group_name, method_name,))
      if method_implementation is not None:
        return _simple_method_handler(
            method_implementation,
            self._request_deserializers.get((group_name, method_name,)),
            self._response_serializers.get((group_name, method_name,)))
      elif self._multi_method_implementation is None:
        return None
      else:
        try:
          return None  #TODO(nathaniel): call the multimethod.
        except face.NoSuchMethodError:
          return None


class _Server(interfaces.Server):

  def __init__(self, server):
    self._server = server

  def add_insecure_port(self, address):
    return self._server.add_insecure_port(address)

  def add_secure_port(self, address, server_credentials):
    return self._server.add_secure_port(address, server_credentials)

  def start(self):
    self._server.start()

  def stop(self, grace):
    return self._server.stop(grace)

  def __enter__(self):
    self._server.start()
    return self

  def __exit__(self, exc_type, exc_val, exc_tb):
    self._server.stop(None)
    return False


def server(
    service_implementations, multi_method_implementation, request_deserializers,
    response_serializers, thread_pool, thread_pool_size):
  generic_rpc_handler = _GenericRpcHandler(
      service_implementations, multi_method_implementation,
      request_deserializers, response_serializers)
  if thread_pool is None:
    effective_thread_pool = logging_pool.pool(
        _DEFAULT_POOL_SIZE if thread_pool_size is None else thread_pool_size)
  else:
    effective_thread_pool = thread_pool
  return _Server(grpc.server((generic_rpc_handler,), effective_thread_pool))