Exposing proto files in a gRPC service over a frameworkless and lightweight API
source link: https://anthonygiretti.com/2020/07/06/exposing-proto-files-in-a-grpc-service-over-a-frameworkless-and-lightweight-api/
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Exposing proto files in a gRPC service over a frameworkless and lightweight API
Introduction
A few days ago I introduced the notion of nano service in ASP.NET Core or rather how to implement a REST API without any particular framework (https://anthonygiretti.com/2020/06/29/nano-services-with-asp-net-core-or-how-to-build-a-light-api/). Since then, I have challenged myself regularly on the possibilities of relevant applications of this idea. Well, I found a very interesting use case: exposing the protobuffs of a gRPC service without using a framework and having to manage collisions with the gRPC framework of ASP.NET Core. This article will show you how to do it in the simplest way possible.
Implementing a ProtoService
Well, in order to make a clearer code, I have implemented a service (then unit testable) instead of writing the whole implementation in the Startup.cs file. The way I implement it (fetching files in the constructor) it’s because I will use Singleton lifetime of ASP.NET Core DI system and let it manage the my service instance, I could have implemented myself a thread safe constructor. Implementation of the ProtoService:
using System.Collections.Generic; using System.IO; using System.Linq; using System.Text.Json; using System.Threading.Tasks; using Microsoft.AspNetCore.Hosting;
namespace DemoGrpc.Web.Services { public class ProtoService { private readonly string _baseDirectory; private readonly Dictionary<string, IEnumerable<string>> _protosByVersion;
public ProtoService(IWebHostEnvironment webHost) { _baseDirectory = webHost.ContentRootPath; _protosByVersion = Get(_baseDirectory); }
public async Task<string> GetAllAsync() { using (var stream = new MemoryStream()) { await JsonSerializer.SerializeAsync(stream, _protosByVersion); stream.Position = 0; using var reader = new StreamReader(stream); return await reader.ReadToEndAsync(); }
}
public string Get(int version, string protoName) { var filePath = $"{_baseDirectory}\\protos\\v{version}\\{protoName}"; var exist = File.Exists(filePath);
return exist ? filePath : null; }
private Dictionary<string, IEnumerable<string>> Get(string baseDirectory) =>
Directory.GetDirectories($"{baseDirectory}\\protos") .Select(x => new { version = x, protos = Directory.GetFiles(x).Select(Path.GetFileName)}) .ToDictionary(o => Path.GetRelativePath("protos", o.version), o => o.protos); } }
Once done we can instantiate the service in the Starup.cs file and expose endpoints.
Exposing endpoints
I’m expising here 2 endpoints:
- GET /protos that provides a json collection of protobuf files grouped version with the WriteAsync extension.
- GET /protos/v{version:int}/{protoName} that provides the protobuf file in text format with the SendFileAsync extension.
After route parameters conversion to their right type, the Startup file looks like this:
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; using CountryGrpcServiceV1 = DemoGrpc.Web.Services.V1.CountryGrpcService; using System.Net;
namespace DemoGrpc.Web { public class Startup { public Startup(IConfiguration configuration) { Configuration = configuration; }
public IConfiguration Configuration { get; }
public void ConfigureServices(IServiceCollection services) { services.AddGrpc();
services.AddSingleton<ProtoService>(); }
// 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 => { var protoService = endpoints.ServiceProvider.GetRequiredService<ProtoService>();
endpoints.MapGrpcService<CountryGrpcServiceV1>();
endpoints.MapGet("/protos", async context => { await context.Response.WriteAsync(await protoService.GetAllAsync()); });
endpoints.MapGet("/protos/v{version:int}/{protoName}", async context => { var version = int.Parse((string)context.Request.RouteValues["version"]); var protoName = (string)context.Request.RouteValues["protoName"];
var filePath = protoService.Get(version, protoName);
if (filePath != null) { await context.Response.SendFileAsync(filePath); } else { context.Response.StatusCode = (int) HttpStatusCode.NotFound; } }); }); } } }
Demo:
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