gRPC config - interceptor creation and lifetime (#24338)

aspnetcore/grpc/configuration.md

@@ -25,7 +25,7 @@ The following table describes options for configuring gRPC services:
 | `CompressionProviders` | gzip | A collection of compression providers used to compress and decompress messages. Custom compression providers can be created and added to the collection. The default configured providers support **gzip** compression. |
 | `ResponseCompressionAlgorithm` | `null` | The compression algorithm used to compress messages sent from the server. The algorithm must match a compression provider in `CompressionProviders`. For the algorithm to compress a response, the client must indicate it supports the algorithm by sending it in the **grpc-accept-encoding** header. |
 | `ResponseCompressionLevel` | `null` | The compress level used to compress messages sent from the server. |
-| `Interceptors` | None | A collection of interceptors that are run with each gRPC call. Interceptors are run in the order they are registered. Globally configured interceptors are run before interceptors configured for a single service. For more information about gRPC interceptors, see [gRPC Interceptors vs. Middleware](xref:grpc/migration#grpc-interceptors-vs-middleware). |
+| `Interceptors` | None | A collection of interceptors that are run with each gRPC call. Interceptors are run in the order they are registered. Globally configured interceptors are run before interceptors configured for a single service.<br/><br/>Interceptors have a per-request lifetime by default. The interceptor constructor is called and parameters are resolved from [dependency injection (DI)](xref:fundamentals/dependency-injection). An interceptor type can also be registered with DI to override how it is created and its lifetime.<br/><br/>Interceptors offer similar functionalities compared to ASP.NET Core middleware. For more information, see [gRPC Interceptors vs. Middleware](xref:grpc/migration#grpc-interceptors-vs-middleware). |
 | `IgnoreUnknownServices` | `false` | If `true`, calls to unknown services and methods don't return an **UNIMPLEMENTED** status, and the request passes to the next registered middleware in ASP.NET Core. |
 
 Options can be configured for all services by providing an options delegate to the `AddGrpc` call in `Startup.ConfigureServices`:
@@ -36,6 +36,10 @@ Options for a single service override the global options provided in `AddGrpc` a
 
 [!code-csharp[](~/grpc/configuration/sample/GrcpService/Startup2.cs?name=snippet)]
 
+Service interceptors have a per-request lifetime by default. Registering the interceptor type with DI overrides how an interceptor is created and its lifetime.
+
+[!code-csharp[](~/grpc/configuration/sample/GrcpService/Startup3.cs?name=snippet)]
+
 ## Configure client options
 
 gRPC client configuration is set on `GrpcChannelOptions`. Configuration options are in the [`Grpc.Net.Client`](https://www.nuget.org/packages/Grpc.Net.Client) package.

aspnetcore/grpc/configuration/sample/GrcpService/Startup3.cs

@@ -0,0 +1,45 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Threading.Tasks;
+using Microsoft.AspNetCore.Builder;
+using Microsoft.AspNetCore.Hosting;
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Hosting;
+
+namespace GrcpService
+{
+    public class Startup2
+    {
+        // This method gets called by the runtime. Use this method to add services to the container.
+        // For more information on how to configure your application, visit https://go.microsoft.com/fwlink/?LinkID=398940
+#region snippet
+        public void ConfigureServices(IServiceCollection services)
+        {
+            services.AddGrpc(options =>
+            {
+                options.Inteceptors.Add<LoggingInterceptor>();
+            });
+            services.AddSingleton<LoggingInterceptor>();
+        }
+#endregion
+
+        // 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();
+            }
+
+            app.UseRouting();
+
+            app.UseEndpoints(endpoints =>
+            {
+                // 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
+                endpoints.MapGrpcService<GreeterService>();
+            });
+        }
+    }
+}