0

在 dart 中使用 gprc 工作时，如果第一个 rpc 调用的响应类型是流式响应，则客户端应用程序在调用流处理程序时无法连接到服务器。我在构建包helloworld中的示例时发现了这个问题。

有什么方法可以确保建立连接？还是我做错了什么？

我已经尝试过了，await channel.getConnection();但没有任何区别。

grpc版本：3.0.2

  1. helloworld.proto：
// Copyright 2015 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.

syntax = "proto3";

option java_multiple_files = true;
option java_package = "io.grpc.examples.helloworld";
option java_outer_classname = "HelloWorldProto";
option objc_class_prefix = "HLW";

package helloworld;

// The greeting service definition.
service Greeter {
  // Sends a greeting
  rpc SayHello (HelloRequest) returns (HelloReply) {}
  rpc SayHelloStream (HelloRequest) returns (stream HelloReply) {}
}

// The request message containing the user's name.
message HelloRequest {
  string name = 1;
}

// The response message containing the greetings
message HelloReply {
  string message = 1;
}
  1. server.dart：
// Copyright (c) 2018, the gRPC project authors. Please see the AUTHORS file
// for details. All rights reserved.
//
// 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.

/// Dart implementation of the gRPC helloworld.Greeter server.
import 'package:grpc/grpc.dart';
import 'package:helloworld/src/generated/helloworld.pbgrpc.dart';

class GreeterService extends GreeterServiceBase {
  @override
  Stream<HelloReply> sayHelloStream(
      ServiceCall call, HelloRequest request) async* {
    for (var i = 0; i < 10; i++) {
      yield HelloReply()..message = 'Hello, ${request.name}!';
      await Future.delayed(Duration(seconds: 1));
    }
  }

  @override
  Future<HelloReply> sayHello(ServiceCall call, HelloRequest request) async {
    return HelloReply()..message = 'Hello, ${request.name}!';
  }
}

Future<void> main(List<String> args) async {
  final server = Server(
    [GreeterService()],
    const <Interceptor>[],
    CodecRegistry(codecs: const [GzipCodec(), IdentityCodec()]),
  );
  await server.serve(port: 50051);
  print('Server listening on port ${server.port}...');
}
  1. client.dart
// Copyright (c) 2018, the gRPC project authors. Please see the AUTHORS file
// for details. All rights reserved.
//
// 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.

/// Dart implementation of the gRPC helloworld.Greeter client.
import 'package:grpc/grpc.dart';
import 'package:helloworld/src/generated/helloworld.pbgrpc.dart';

Future<void> main(List<String> args) async {
  final channel = ClientChannel(
    'localhost',
    port: 50051,
    options: ChannelOptions(
      credentials: ChannelCredentials.insecure(),
      codecRegistry:
          CodecRegistry(codecs: const [GzipCodec(), IdentityCodec()]),
    ),
  );
  final stub = GreeterClient(channel);

  final name = args.isNotEmpty ? args[0] : 'world';

  try {
    // works if this call is made first
    // final response = await stub.sayHello(HelloRequest()..name = name);
    // print('Greeter client received: ${response.message}');

    // this has no effect
    // await channel.getConnection();

    final responseStream = stub.sayHelloStream(
      HelloRequest()..name = name,
    );
    
    // This doesn't work standalone.
    responseStream
        .listen((value) => print('Greeter client received: ${value.message}'));

    // Works when using await for
    // await for (var value in responseStream) {
    //   print('Greeter client received: ${value.message}');
    // }
  } catch (e) {
    print('Caught error: $e');
  }
  await channel.shutdown();
}

预期结果：它应该可以正常工作并Greeter client received: ${value.message}'以 1 秒的间隔打印 10 次。

实际结果：运行client.dart时收到以下错误。

gRPC Error (code: 14, codeName: UNAVAILABLE, message: Error connecting: Connection shutting down., details: null, rawResponse: null, trailers: {})

添加以下行（如注释中所示）没有问题，结果按预期打印 1 + 10 次。

// final response = await stub.sayHello(HelloRequest()..name = name);
// print('Greeter client received: ${response.message}');
4

0 回答 0