全域性錯誤處理服務端

微軟已經實施了Interceptors，它們類似於Filter或Middlewares在ASP.NET MVC的核心或的WebAPI，它們可以用於全域性異常處理，日誌記錄，驗證等。
這是伺服器端Interceptor自己的實現，Continuation是必須等待的Task，然後，如果引發了任何異常，則可以根據所獲得的異常來控制RpcException和關聯的StatusCode

using Grpc.Core;
using Grpc.Core.Interceptors;
using Microsoft.Extensions.Logging;
using System;
using System.Data.SqlClient;
using System.Threading.Tasks;

namespace DemoGrpc.Web.Logging
{
    public class LoggerInterceptor : Interceptor
    {
        private readonly ILogger<LoggerInterceptor> _logger;

        public LoggerInterceptor(ILogger<LoggerInterceptor> logger)
        {
            _logger = logger;
        }

        public async override Task<TResponse> UnaryServerHandler<TRequest, TResponse>(
            TRequest request,
            ServerCallContext context,
            UnaryServerMethod<TRequest, TResponse> continuation)
        {
            LogCall(context);
            try
            {
                return await continuation(request, context);
            }
            catch (SqlException e)
            {
                _logger.LogError(e, $"An SQL error occured when calling {context.Method}");
                Status status;

                if (e.Number == -2)
                {
                    status = new Status(StatusCode.DeadlineExceeded, "SQL timeout");
                }
                else
                {
                    status = new Status(StatusCode.Internal, "SQL error");
                }
                throw new RpcException(status);
            }
            catch (Exception e)
            {
                _logger.LogError(e, $"An error occured when calling {context.Method}");
                throw new RpcException(Status.DefaultCancelled, e.Message);
            }
            
        }

        private void LogCall(ServerCallContext context)
        {
            var httpContext = context.GetHttpContext();
            _logger.LogDebug($"Starting call. Request: {httpContext.Request.Path}");
        }
    }
}

 

註冊方式如下

using DemoGrpc.Web.Logging;
using DemoGrpc.Web.Services;
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.Http;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;

namespace DemoGrpc.Web
{
    public class Startup
    {
        public Startup(IConfiguration configuration)
        {
            Configuration = configuration;
        }

        public IConfiguration Configuration { get; }

        public void ConfigureServices(IServiceCollection services)
        {
            //註冊GRpc全域性異常捕獲
            services.AddGrpc(options =>
            {
                options.Interceptors.Add<LoggerInterceptor>();
            });
        }

        // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
        public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
        {
            if (env.IsDevelopment())
            {
                app.UseDeveloperExceptionPage();
            }
            else
            {
                app.UseHsts();
            }

            app.UseHttpsRedirection();

            app.UseRouting();

            app.UseEndpoints(endpoints =>
            {
                endpoints.MapGrpcService<CountryGrpcService>();

                endpoints.MapGet("/", async context =>
                {
                    await context.Response.WriteAsync("Communication with gRPC endpoints must be made through a gRPC client. To learn how to create a client, visit: https://go.microsoft.com/fwlink/?linkid=2086909");
                });
            });
        }
    }
}

 

第二種方法也可以捕獲到GRpc異常，但是寫法比較粗糙。不推薦使用

using AutoMapper;
using DemoGrpc.Domain.Entities;
using DemoGrpc.Protobufs;
using DempGrpc.Services.Interfaces;
using Grpc.Core;
using System;
using System.Threading.Tasks;

public class CountryGrpcService : CountryService.CountryServiceBase
{
    private readonly ICountryService _countryService;
    private readonly IMapper _mapper;

    public CountryGrpcService(ICountryService countryService, IMapper mapper)
    {
        _countryService = countryService;
        _mapper = mapper;
    }

    public override async Task<CountriesReply> GetAll(EmptyRequest request, ServerCallContext context)
    {
        try
        {
            var countries = await _countryService.GetAsync();
            return _mapper.Map<CountriesReply>(countries);
        }
        catch (Exception e)
        {
            throw new RpcException(Status.DefaultCancelled, e.Message);
        }
    }
}
 

Rpc異常資訊介紹如下

具體地址：https://grpc.github.io/grpc/csharp/api/Grpc.Core.StatusCode.html

RpcException有相對應的過載：具體如下，可以自定義異常返回的資訊

全域性錯誤處理客戶端

客戶端也可以通過攔截器處理錯誤(實現客戶端事件，如AsyncUnaryCall):

using Grpc.Core;
using Grpc.Core.Interceptors;
using Microsoft.Extensions.Logging;
using System.Threading.Tasks;

namespace ConsoleAppGRPC.Logging
{
    public class LoggerInterceptor : Interceptor
    {
        private readonly ILogger<LoggerInterceptor> _logger;

        public LoggerInterceptor(ILogger<LoggerInterceptor> logger)
        {
            _logger = logger;
        }

        public override AsyncUnaryCall<TResponse> AsyncUnaryCall<TRequest, TResponse>(
            TRequest request,
            ClientInterceptorContext<TRequest, TResponse> context,
            AsyncUnaryCallContinuation<TRequest, TResponse> continuation)
        {
            LogCall(context.Method);

            var call = continuation(request, context);

            return new AsyncUnaryCall<TResponse>(HandleResponse(call.ResponseAsync), call.ResponseHeadersAsync, call.GetStatus, call.GetTrailers, call.Dispose);
        }

        private async Task<TResponse> HandleResponse<TResponse>(Task<TResponse> t)
        {
            try
            {
                var response = await t;
                _logger.LogDebug($"Response received: {response}");
                return response;
            }
            catch (RpcException ex)
            {
                _logger.LogError($"Call error: {ex.Message}");
                return default;
            }
        }

        private void LogCall<TRequest, TResponse>(Method<TRequest, TResponse> method) where TRequest : class where TResponse : class
        {
            _logger.LogDebug($"Starting call. Type: {method.Type}. Request: {typeof(TRequest)}. Response: {typeof(TResponse)}");
        }
    }
}

使用方法：

using DemoGrpc.Domain.Entities;
using DemoGrpc.Protobufs;
using Microsoft.Extensions.DependencyInjection;
using System;
using System.Linq;
using System.Threading.Tasks;
using static DemoGrpc.Protobufs.CountryService;
using Microsoft.Extensions.Logging;
using ConsoleAppGRPC.Logging;

namespace ConsoleAppGRPC
{
    class Program
    {
        static async Task Main(string[] args)
        {
            var services = new ServiceCollection();
            services.AddScoped<LoggerInterceptor>();
            services.AddLogging(logging =>
            {
                logging.AddConsole();
                logging.SetMinimumLevel(LogLevel.Debug);
            });

            services.AddGrpcClient<CountryServiceClient>(o =>
            {
                o.Address = new Uri("https://localhost:5001");
            }).AddInterceptor<LoggerInterceptor>();

            var provider = services.BuildServiceProvider();
            var client = provider.GetRequiredService<CountryServiceClient>();
            var logger = provider.GetRequiredService<ILogger<Program>>();

            var countries = (await client.GetAllAsync(new EmptyRequest()))?.Countries.Select(x => new Country
            {
                CountryId = x.Id,
                Description = x.Description,
                CountryName = x.Name
            }).ToList();

            if (countries != null)
            {
                logger.LogInformation("Found countries");
                countries.ForEach(x => Console.WriteLine($"Found country {x.CountryName} ({x.CountryId}) {x.Description}"));
            }
            else
            {
                logger.LogDebug("No countries found");
            }
        }
    }
}

得到的結果資訊

結論
我們在本文中看到了如何全域性處理錯誤。攔截器、RpcException、狀態程式碼和返回資訊的使用為我們提供了一定的靈活性，比如定製錯誤和向客戶端傳送相關錯誤的可能性。