每次调用都会实例化 GRPC 服务

Question

我在 .NET core 3.1 下创建了一个 GRPC 服务主机（使用来自 https://github.com/grpc/grpc-dotnet 的 Grpc.AspNetCore v2.30）。通过在“ProxyService”构造函数中放置断点，我可以看到每次调用都会实例化该类 - 每次来自客户端的 GRPC 调用时，都会触发断点。如何将其配置为始终使用相同的 ProxyService 实例？

这些是程序和启动类：

    class Program
    {
        const int _port = 23456;

        static void Main(string[] args)
        {
            CreateHostBuilder(args).Build().Run();
            Console.WriteLine("started - press any key to quit...");
            Console.ReadKey();
        }

        public static IHostBuilder CreateHostBuilder(string[] args) =>
            Host.CreateDefaultBuilder(args)
                .ConfigureWebHostDefaults(webBuilder =>
                {
                    webBuilder.ConfigureKestrel(options =>
                    {
                        options.ConfigureEndpointDefaults(o =>
                        {
                            o.Protocols = HttpProtocols.Http2;
                            
                        });
                        options.ListenAnyIP(_port);
                    });
                    webBuilder.UseStartup<Startup>();
                });
    }

    public class ProxyService : StreamingApi.Protos.StreamingApi.StreamingApiBase
    {
        public ProxyService()
        {
    // gets here with every client call
        }

        public override Task<UpdateResponse> Update(UpdateRequest request, ServerCallContext context)
        {
            return Task.FromResult(new UpdateResponse());
        }
    }

   class Startup
    {
        public void ConfigureServices(IServiceCollection services)
        {
            services.AddGrpc();
        }

        public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
        {
            if (env.IsDevelopment())
            {
                app.UseDeveloperExceptionPage();
            }

            app.UseRouting();

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

Answer 1

首先，让我猜猜你为什么要这样做：

• 您在 ProxyService 内部有一些繁重的逻辑，例如某种初始化；
• 您有一些静态变量要在调用之间共享；

要解决第一种情况，您应该使用任一方法本身：

    public ProxyService(IFooBar foobar)
    {
        this.foobar = foobar;
    }
    public override Task<UpdateResponse> Update(UpdateRequest request, ServerCallContext context)
    {
        await this.foobar.InitializeAsync();
        return Task.FromResult(new UpdateResponse());
    }

或系统中的其他触发器，例如“服务启动时”：

    public interface IFooBarInitilizer :IHostedService
    {
    }
    public class FooBarInitilizer : IFooBarInitilizer 
    {
        public async Task StartAsync(CancellationToken token){ await this.foobar.InitializeAsync(); }
    }

    //in your Configure
    public void ConfigureServices(IServiceCollection services)
    {
        services.AddGrpc();
        services.AddSingleton<IFooBarInitializer, FooBarInitializer>();
        services.AddHostedService(x=> x.GetService<IFooBarInitializer>());
    }

第二种情况更简单，因为你可以通过接口依赖指定你的共享资源：

    public void ConfigureServices(IServiceCollection services)
    {
        services.AddGrpc();
        services.AddSingleton<IFooBarResource, FooBarResource>();
    }

    
public class ProxyService : StreamingApi.Protos.StreamingApi.StreamingApiBase
{
    public ProxyService(IFooBarResource myStaticResource)
    {
        this.myStaticResource = myStaticResource;
    }

    public override Task<UpdateResponse> Update(UpdateRequest request, ServerCallContext context)
    {
        var somethingGood = this.myStaticResource.GetMeSomethingGood();
        return Task.FromResult(new UpdateResponse());
    }
}