What Is the gRPC Communication Framework

gRPC is a high-performance, open source, general-purpose RPC framework developed by Google. It is based on HTTP/2 and supports multiple languages (such as Go, Java, Python, C++, Node.js, Ruby, C#, Objective-C, PHP, and Dart).

gRPC uses Protocol Buffers as its interface definition language (IDL). Protocol Buffers is a lightweight and efficient structured data serialization method, similar to XML or JSON, but smaller, faster, and simpler.

basket-service-grpc

Implementing a Service with gRPC in ASP.NET Core

To define a gRPC service, you need to create a gRPC service definition file (a .proto file) and then use the gRPC tools to generate the server and client code.

gRPC Services with OpenAPI

dotnet add package Microsoft.AspNetCore.Grpc.Swagger

<IncludeHttpRuleProtos>true</IncludeHttpRuleProtos>

var builder = WebApplication.CreateBuilder(args);
builder.Services.AddGrpc().AddJsonTranscoding();
builder.Services.AddGrpcSwagger();
builder.Services.AddSwaggerGen(c =>
{
    c.SwaggerDoc("v1",
        new OpenApiInfo { Title = "gRPC transcoding", Version = "v1" });
});

var app = builder.Build();
app.UseSwagger();
if (app.Environment.IsDevelopment())
    app.UseSwaggerUI(c =>
    {
        c.SwaggerEndpoint("/swagger/v1/swagger.json", "My API V1");
    });
}
app.MapGrpcService<GreeterService>();

app.Run();

// My amazing greeter service.
service Greeter {
  // Sends a greeting.
  rpc SayHello (HelloRequest) returns (HelloReply) {
    option (google.api.http) = {
      get: "/v1/greeter/{name}"
    };
  }
}

message HelloRequest {
  // Name to say hello to.
  string name = 1;
}
message HelloReply {
  // Hello reply message.
  string message = 1;
}

Unit Testing gRPC Services

dotnet add package moq

public class GreeterServiceTests
{
    [Fact]
    public async Task SayHello_ReturnsHello()
    {
        // Arrange
        var mockLogger = new Mock<ILogger<GreeterService>>();
        var service = new GreeterService(mockLogger.Object);
        var request = new HelloRequest { Name = "Unit Test" };
        var context = new ServerCallContext();

        // Act
        var reply = await service.SayHello(request, context);

        // Assert
        Assert.Equal("Hello Unit Test", reply.Message);
    }
}

Integration Testing gRPC Services

dotnet add package Microsoft.AspNetCore.TestHost

public class GreeterServiceIntegrationTests
{
    private readonly TestServer _server;
    private readonly Greeter.GreeterClient _client;

    public GreeterServiceIntegrationTests()
    {
        _server = new TestServer(new WebHostBuilder()
            .ConfigureServices(services =>
            {
                services.AddGrpc();
            })
            .Configure(app =>
            {
                app.UseRouting();
                app.UseEndpoints(endpoints =>
                {
                    endpoints.MapGrpcService<GreeterService>();
                });
            }));
        _client = new Greeter.GreeterClient(_server.CreateGrpcChannel());
    }

    [Fact]
    public async Task SayHello_ReturnsHello()
    {
        // Arrange
        var request = new HelloRequest { Name = "Integration Test" };

        // Act
        var reply = await _client.SayHelloAsync(request);

        // Assert
        Assert.Equal("Hello Integration Test", reply.Message);
    }
}