text: # Lint as: python3
  # Copyright 2019, The TensorFlow Federated 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.
  """A set of utilities for components of simulation serving infrastructure."""
  
  import concurrent
  import time
  
  import grpc
  
  from tensorflow_federated.proto.v0 import executor_pb2_grpc
  from tensorflow_federated.python.common_libs import py_typecheck
  from tensorflow_federated.python.core import framework
  
  _ONE_DAY_IN_SECONDS = 60 * 60 * 24
  
  
  def run_server(executor, num_threads, port, credentials=None, options=None):
    """Runs a gRPC server hosting a simulation component in this process.
  
    The server runs indefinitely, but can be stopped by a keyboard interrrupt.
  
    Args:
      executor: The executor to be hosted by the server.
      num_threads: The number of network threads to use for handling gRPC calls.
      port: The port to listen on (for gRPC), must be a non-zero integer.
      credentials: The optional credentials to use for the secure connection if
        any, or `None` if the server should open an insecure port. If specified,
        must be a valid `ServerCredentials` object that can be accepted by the
        gRPC server's `add_secure_port()`.
      options: The optional `list` of server options, each in the `(key, value)`
        format accepted by the `grpc.server()` constructor.
  
    Raises:
      ValueError: If `num_threads` or `port` are invalid.
    """
    py_typecheck.check_type(executor, framework.Executor)
    py_typecheck.check_type(num_threads, int)
    py_typecheck.check_type(port, int)
    if credentials is not None:
      py_typecheck.check_type(credentials, grpc.ServerCredentials)
    if num_threads < 1:
      raise ValueError('The number of threads must be a positive integer.')
    if port < 1:
      raise ValueError('The server port must be a positive integer.')
    service = framework.ExecutorService(executor)
    server_kwargs = {}
    if options is not None:
      server_kwargs['options'] = options
    server = grpc.server(
        concurrent.futures.ThreadPoolExecutor(max_workers=num_threads),
        **server_kwargs)
    full_port_string = '[::]:{}'.format(port)
    if credentials is not None:
      server.add_secure_port(full_port_string, credentials)
    else:
      server.add_insecure_port(full_port_string)
    executor_pb2_grpc.add_ExecutorServicer_to_server(service, server)
    server.start()
    try:
      while True:
        time.sleep(_ONE_DAY_IN_SECONDS)
    except KeyboardInterrupt:
      server.stop(None)
  