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| title | author | description | monikerRange | ms.author | ms.date | no-loc | uid | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| gRPC services with ASP.NET Core | juntaoluo | Learn the basic concepts when writing gRPC services with ASP.NET Core. | >= aspnetcore-3.0 | johluo | 09/03/2019 |
|
grpc/aspnetcore |
gRPC services with ASP.NET Core
This document shows how to get started with gRPC services using ASP.NET Core.
Prerequisites
Visual Studio
Visual Studio Code
Visual Studio for Mac
Get started with gRPC service in ASP.NET Core
View or download sample code (how to download).
Visual Studio
See Get started with gRPC services for detailed instructions on how to create a gRPC project.
Visual Studio Code / Visual Studio for Mac
Run dotnet new grpc -o GrpcGreeter from the command line.
Add gRPC services to an ASP.NET Core app
gRPC requires the Grpc.AspNetCore package.
Configure gRPC
In Startup.cs:
- gRPC is enabled with the
AddGrpcmethod. - Each gRPC service is added to the routing pipeline through the
MapGrpcServicemethod.
[!code-csharp] [!INCLUDEabout the series]
ASP.NET Core middlewares and features share the routing pipeline, therefore an app can be configured to serve additional request handlers. The additional request handlers, such as MVC controllers, work in parallel with the configured gRPC services.
Configure Kestrel
Kestrel gRPC endpoints:
- Require HTTP/2.
- Should be secured with Transport Layer Security (TLS).
HTTP/2
gRPC requires HTTP/2. gRPC for ASP.NET Core validates HttpRequest.Protocol is HTTP/2.
Kestrel supports HTTP/2 on most modern operating systems. Kestrel endpoints are configured to support HTTP/1.1 and HTTP/2 connections by default.
TLS
Kestrel endpoints used for gRPC should be secured with TLS. In development, an endpoint secured with TLS is automatically created at https://localhost:5001 when the ASP.NET Core development certificate is present. No configuration is required. An https prefix verifies the Kestrel endpoint is using TLS.
In production, TLS must be explicitly configured. In the following appsettings.json example, an HTTP/2 endpoint secured with TLS is provided:
Alternatively, Kestrel endpoints can be configured in Program.cs:
Protocol negotiation
TLS is used for more than securing communication. The TLS Application-Layer Protocol Negotiation (ALPN) handshake is used to negotiate the connection protocol between the client and the server when an endpoint supports multiple protocols. This negotiation determines whether the connection uses HTTP/1.1 or HTTP/2.
If an HTTP/2 endpoint is configured without TLS, the endpoint's ListenOptions.Protocols must be set to HttpProtocols.Http2. An endpoint with multiple protocols (for example, HttpProtocols.Http1AndHttp2) can't be used without TLS because there is no negotiation. All connections to the unsecured endpoint default to HTTP/1.1, and gRPC calls fail.
For more information on enabling HTTP/2 and TLS with Kestrel, see Kestrel endpoint configuration.
[!NOTE] macOS doesn't support ASP.NET Core gRPC with TLS. Additional configuration is required to successfully run gRPC services on macOS. For more information, see Unable to start ASP.NET Core gRPC app on macOS.
Integration with ASP.NET Core APIs
gRPC services have full access to the ASP.NET Core features such as Dependency Injection (DI) and Logging. For example, the service implementation can resolve a logger service from the DI container via the constructor:
public class GreeterService : Greeter.GreeterBase
{
public GreeterService(ILogger<GreeterService> logger)
{
}
}
By default, the gRPC service implementation can resolve other DI services with any lifetime (Singleton, Scoped, or Transient).
Resolve HttpContext in gRPC methods
The gRPC API provides access to some HTTP/2 message data, such as the method, host, header, and trailers. Access is through the ServerCallContext argument passed to each gRPC method:
ServerCallContext does not provide full access to HttpContext in all ASP.NET APIs. The GetHttpContext extension method provides full access to the HttpContext representing the underlying HTTP/2 message in ASP.NET APIs: