我又造了個輪子：GrpcGateway

我個人對GRPC是比較感興趣的，最近在玩通過前端調用GRPC。通過前端調用GRPC業界有兩種方式：GRPC Web和GRPC JSON轉碼。

GRPC Web

通過JS或者Blazor WASM調用GRPC，微軟在這方面做的還是很好的，從.NET Core3.0之後就提供了兩種實現GRPC Web的方式（Grpc.AspNetCore.Web與Envoy）。我在之前的一篇里也寫過如何通過Blazor WASM調用GRPC Web。

GRPC JSON

通過Restful api調用一個代理服務，代理服務將數據轉發到GRPC Server就是GRPC JSON。微軟從.NET7開始也正式提供了GRPC JSON轉碼的方式。

為什麼要造輪子

既然有了GRPC Web與GRPC Json，那我為啥還要再造這麼一個輪子？

原因是有位同行看了如何通過Blazor WASM調用GRPC Web 這篇文章後，告訴我微信小程式目前沒辦法通過這種方式調用GRPC。我當時覺得很奇怪，微信小程式也屬於前端，為啥不能調用GRPC呢？

GRPC Web+小程式遇到的問題

只是聽說還不能確認，要自己試一試，於是我用GRPC Web的方式讓小程式調用GRPC，首先需要生成GRPC JS Client代碼：

protoc.exe -I=. test.proto --js_out=import_style=commonjs:.\grpcjs\ --plugin=protoc-gen-grpc=.\protoc-gen-grpc-web.exe --grpc-web_out=import_style=commonjs,mode=grpcwebtext:.\grpcjs\

然後將生成的代碼引入小程式端，發現確實有問題，微信小程式編譯後無法正常識別GRPC的namespace，會報以下錯誤：

proto is not defined

去查了下原因，應該是因為小程式目前不支持protobuf序列化。然後我通過一種取巧的方式手動在生成的GRPC JS中添加了proto變數

var proto = {}

再次嘗試，雖然proto能找到，但是又找不到其他對象，並且最主要的是GRPC JS Client是通過proto工具生成的，每次生成手動定義proto變數也不現實。

GRPC Web+小程式遇到問題總結：

1. 小程式目前不支持protobuf序列化
2. 手動修改生成的GRPC JS Client不友好

既然小程式通過GRPC Web方式調用GRPC失敗，那還有GRPC Json。

GRPC JSON+Envoy+小程式遇到的問題

我使用了Envoy來充當restful代理，調用GRPC。我在之前有一篇通過Envoy JSON代理GRPC的帖子。按這個帖子來了一遍。

計劃通過docker-compose方式運行GRPC Server和Envoy代理。

既然用GRPC，那肯定用http2/http2，在docker里運行.net core必然需要證書，沒有證書就自己搞一個自簽證書。

openssl req -newkey rsa:2048 -nodes -keyout server.key -x509 -days 365 -out server.cer

openssl pkcs12 -export -in server.cer -inkey server.key -out server.pfx

證書有了，在GRPC里配置https

    builder.WebHost.ConfigureKestrel(o =>
    {

        o.ListenAnyIP(1111, p =>
        {
            p.Protocols = HttpProtocols.Http2;
            p.UseHttps("/app/server.pfx", "123456");
        });
    });

然後就開始配置envoy

首先生成grpc proto描述符

protoc.exe -I=.  --descriptor_set_out=.\test.pb --include_imports .\test.proto  --proto_path=.

然後定義envoy配置文件

admin:
  address:
    socket_address: {address: 0.0.0.0, port_value: 9901}

static_resources:
  listeners:
  - name: listener1
    address:
      socket_address: {address: 0.0.0.0, port_value: 10000}
    filter_chains:
    - filters:
      - name: envoy.filters.network.http_connection_manager
        typed_config:
          "@type": type.googleapis.com/envoy.extensions.filters.network.http_connection_manager.v3.HttpConnectionManager
          stat_prefix: grpc_json
          codec_type: AUTO
          route_config:
            name: local_route
            virtual_hosts:
            - name: local_service
              domains: ["*"]
              routes:
              - match: {prefix: "/test"}
                route: 
                 cluster: grpc
          http_filters:
          - name: envoy.filters.http.grpc_json_transcoder
            typed_config:
              "@type": type.googleapis.com/envoy.extensions.filters.http.grpc_json_transcoder.v3.GrpcJsonTranscoder
              proto_descriptor: "/etc/envoy/test.pb"
              services: ["test"]
              print_options:
                add_whitespace: true
                always_print_primitive_fields: true
                always_print_enums_as_ints: false
                preserve_proto_field_names: false
              auto_mapping: true
          - name: envoy.filters.http.router
            typed_config:
             "@type": type.googleapis.com/envoy.extensions.filters.http.router.v3.Router
  clusters:
  - name: grpc
    type: static
    connect_timeout: 15s
    lb_policy: ROUND_ROBIN
    dns_lookup_family: V4_ONLY
    typed_extension_protocol_options:
      envoy.extensions.upstreams.http.v3.HttpProtocolOptions:
        "@type": type.googleapis.com/envoy.extensions.upstreams.http.v3.HttpProtocolOptions
        explicit_http_config:
          http2_protocol_options: {}
    load_assignment:
      cluster_name: grpc
      endpoints:
      - lb_endpoints:
        - endpoint:
            address:
              socket_address:
                address: 某ip
                port_value: 1111

下麵就定義envoy的dockerfile，主要是信任自簽證書

#See https://aka.ms/containerfastmode to understand how Visual Studio uses this Dockerfile to build your images for faster debugging.

FROM envoyproxy/envoy-dev:e834c24e061b710348ffd72016d5d1069698b4ff

COPY ["server.crt","/usr/local/share/ca-certificates/"]

RUN ["update-ca-certificates"]

最後就是定義docker-compsoe.yaml

version: '3.4'

services:
  myenvoy:
    image: myenvoy
    container_name: myenvoy
    command: "-c /etc/envoy/envoy.yaml  --log-level debug"
    build:
      context: .
      dockerfile: GrpcServer/DockerfileEnvoy
    volumes:
     - "grpcpbs/:/etc/envoy/"
     - "grpcpbs/logs:/logs"
    ports:
      - "9901:9901"
      - "10000:10000"
    depends_on:
      - grpcserver
    networks:
    - mynetwork
  grpcserver:
    image: grpcserver
    container_name: grpcserver
    networks:
    - mynetwork
    build:
      context: .
      dockerfile: GrpcServer/Dockerfile
    ports:
      - "1111:1111"

networks:
  mynetwork:

最後通過docker-compsoe up -d運行，但是postman調用的時候，envoy與grpcserver的通信連接成功了，但是數據傳輸時總是被 connection reset，去github上找原因也沒找到。至此grpc json+envoy又失敗了。

GRPC JSON+Envoy+小程式遇到問題總結：

1. 數據傳輸時connection 被莫名reset

既然envoy走不通不行，那就自己造一個吧。

開始造輪子

GRPC JSON的形式，原理就是通過一個web api接收restful請求，將請求數據轉發到GRPC Server。

首先創建一個web api命名為GrpcGateway，並引入proto文件，生成grpc client代碼

  <ItemGroup>
    <PackageReference Include="Google.Protobuf" Version="3.20.1" />
    <PackageReference Include="Grpc.Net.Client" Version="2.46.0" />
    <PackageReference Include="Grpc.Tools" Version="2.46.1">
      <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
      <PrivateAssets>all</PrivateAssets>
    </PackageReference>
    <PackageReference Include="Microsoft.Extensions.DependencyInjection.Abstractions" Version="6.0.0" />
  </ItemGroup>
  <ItemGroup>
    <Protobuf Include="..\*.proto" GrpcServices="Client" />
  </ItemGroup>

然後創建一個控制器去接受restful請求，而grpc client可採用反射來創建。

 [ApiController]
    [Route("[controller]")]
    public class ProcessGrpcRequestController : ControllerBase
    {
        private readonly ILogger<ProcessGrpcRequestController> _logger;
        private readonly Func<string, ClientBase> _getGrpcClient;
        public ProcessGrpcRequestController(ILogger<ProcessGrpcRequestController> logger, Func<string, ClientBase> getGrpcClient)
        {
            _logger = logger;
            _getGrpcClient = getGrpcClient;
        }

        /// <summary>
        /// 調用grpc
        /// </summary>
        /// <param name="serviceName">Grpc Service Name 從proto文件中查詢</param>
        /// <param name="method">Grpc Method Name 從proto文件中查詢</param>
        /// <returns></returns>
        [HttpPost("serviceName/{serviceName}/method/{method}")]
        public async Task<IActionResult> ProcessAsync(string serviceName, string method)
        {
            try
            {
                if (string.IsNullOrEmpty(serviceName))
                {
                    return BadRequest("serviceName不能為空");
                }
                if (string.IsNullOrEmpty(method))
                {
                    return BadRequest("method不能為空");
                }

                using var sr = new StreamReader(Request.Body, leaveOpen: true, encoding: Encoding.UTF8);
                var paramJson = await sr.ReadToEndAsync();
                if (string.IsNullOrEmpty(paramJson))
                {
                    return BadRequest("參數不能為空");
                }
                var client = _getGrpcClient(serviceName);
                if (client == null)
                {
                    return NotFound();
                }

                Type t = client.GetType();
                var processMethod = t.GetMethods().Where(e => e.Name == method).FirstOrDefault();
                if (processMethod == null)
                {
                    return NotFound();
                }

                var parameters = processMethod.GetParameters();
                if (parameters == null)
                {
                    return NotFound();
                }

                var param = JsonConvert.DeserializeObject(paramJson, parameters[0].ParameterType);
                if (param == null)
                {
                    return BadRequest("參數不能為空");
                }
                var pt = param.GetType();
                var headers = new Metadata();

                if (Request.Headers.Keys.Contains("Authorization"))
                {
                    headers.Add("Authorization", Request.Headers["Authorization"]);
                }

                var result = processMethod.Invoke(client, new object[] { param, headers, null, null });

                return Ok(result);
            }
            catch(Exception ex) when (
            ex.InnerException !=null && ex.InnerException !=null && ex.InnerException is RpcException && 
            ((ex.InnerException as RpcException).StatusCode == Grpc.Core.StatusCode.Unauthenticated || 
            ((ex.InnerException as RpcException).StatusCode == Grpc.Core.StatusCode.PermissionDenied)))
            {
                _logger.LogError(ex, ex.ToString());
                return Unauthorized();
            }
            catch (Exception ex)
            {
                _logger.LogError(ex, ex.Message);
                return BadRequest(ex.ToString());
            }


        }
    }

然後註入動態反射創建grpc client的方法

            services.AddScoped(p => {
                Func<string, ClientBase> func = serviceName =>
                {
                    var channel = GrpcChannel.ForAddress(grpcServerAddress);

                    var parentClassName = $"{serviceName}";

                    var assembly = Assembly.Load("你的dll名字");
                    var parentType = assembly.GetType(parentClassName);

                    var clientType=  parentType.GetNestedType($"{serviceName}Client");
                    if (clientType == null)
                    {
                        throw new Exception($"serviceName:{serviceName}不存在");
                    }
                    var client = Activator.CreateInstance(clientType, new object[] { channel });
                    return (ClientBase)client;
                };
                return func;
            });

然後定義grpc gateway dockerfile ，最主要需要信任證書

#See https://aka.ms/containerfastmode to understand how Visual Studio uses this Dockerfile to build your images for faster debugging.

FROM mcr.microsoft.com/dotnet/aspnet:6.0 AS base
WORKDIR /app
EXPOSE 16666

FROM mcr.microsoft.com/dotnet/sdk:6.0 AS build
WORKDIR /src
COPY ["MyGateway/MyGateway.csproj", "MyGateway/"]
COPY . .
WORKDIR "/src/MyGateway"

FROM build AS publish
RUN dotnet publish "MyGateway.csproj" -c Release -o /app/publish

FROM base AS final
COPY ["server.crt","/usr/local/share/ca-certificates/"]
RUN ["update-ca-certificates"]
WORKDIR /app
COPY --from=publish /app/publish .
ENTRYPOINT ["dotnet", "MyGateway.dll"]

最後通過定義docker-compose

version: '3.4'

services:
  mygateway:
    image: mygateway
    container_name: mygateway
    networks:
    - mynetwork
    build:
      context: .
      dockerfile: MyGateway/Dockerfile
    ports:
      - "2222:2222"
  grpcserver:
    image: grpcserver
    container_name: grpcserver
    networks:
    - mynetwork
    build:
      context: .
      dockerfile: GrpcServer/Dockerfile
    ports:
      - "1111:1111"

networks:
  mynetwork:

通過docker-compsoe up -d 啟動

通過postman調用，看到200狀態碼，終於成功了，最後試了下小程式也能通過這種方式調用後端GRPC了，整個人都舒服了...