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# Copyright 2020 The 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.
"""The Python example of utilizing wait-for-ready flag."""
import asyncio
from contextlib import contextmanager
import logging
import socket
from typing import Iterable
import grpc
helloworld_pb2, helloworld_pb2_grpc = grpc.protos_and_services(
"helloworld.proto")
_LOGGER = logging.getLogger(__name__)
_LOGGER.setLevel(logging.INFO)
@contextmanager
def get_free_loopback_tcp_port() -> Iterable[str]:
if socket.has_ipv6:
tcp_socket = socket.socket(socket.AF_INET6)
else:
tcp_socket = socket.socket(socket.AF_INET)
tcp_socket.bind(('', 0))
address_tuple = tcp_socket.getsockname()
yield f"localhost:{address_tuple[1]}"
tcp_socket.close()
class Greeter(helloworld_pb2_grpc.GreeterServicer):
async def SayHello(self, request: helloworld_pb2.HelloRequest,
unused_context) -> helloworld_pb2.HelloReply:
return helloworld_pb2.HelloReply(message=f'Hello, {request.name}!')
def create_server(server_address: str):
server = grpc.aio.server()
helloworld_pb2_grpc.add_GreeterServicer_to_server(Greeter(), server)
bound_port = server.add_insecure_port(server_address)
assert bound_port == int(server_address.split(':')[-1])
return server
async def process(stub: helloworld_pb2_grpc.GreeterStub,
wait_for_ready: bool = None) -> None:
try:
response = await stub.SayHello(helloworld_pb2.HelloRequest(name='you'),
wait_for_ready=wait_for_ready)
message = response.message
except grpc.aio.AioRpcError as rpc_error:
assert rpc_error.code() == grpc.StatusCode.UNAVAILABLE
assert not wait_for_ready
message = rpc_error
else:
assert wait_for_ready
_LOGGER.info("Wait-for-ready %s, client received: %s",
"enabled" if wait_for_ready else "disabled", message)
async def main() -> None:
# Pick a random free port
with get_free_loopback_tcp_port() as server_address:
# Create gRPC channel
channel = grpc.aio.insecure_channel(server_address)
stub = helloworld_pb2_grpc.GreeterStub(channel)
# Fire an RPC without wait_for_ready
fail_fast_task = asyncio.get_event_loop().create_task(
process(stub, wait_for_ready=False))
# Fire an RPC with wait_for_ready
wait_for_ready_task = asyncio.get_event_loop().create_task(
process(stub, wait_for_ready=True))
# Wait for the channel entering TRANSIENT FAILURE state.
state = channel.get_state()
while state != grpc.ChannelConnectivity.TRANSIENT_FAILURE:
await channel.wait_for_state_change(state)
state = channel.get_state()
# Start the server to handle the RPC
server = create_server(server_address)
await server.start()
# Expected to fail with StatusCode.UNAVAILABLE.
await fail_fast_task
# Expected to success.
await wait_for_ready_task
await server.stop(None)
await channel.close()
if __name__ == '__main__':
logging.basicConfig(level=logging.INFO)
asyncio.get_event_loop().run_until_complete(main())
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