CommandQuery.GoogleCloudFunctions ⚡

Command Query Separation for Google Cloud Functions

• Provides generic function support for commands and queries with HTTP functions
• Enables APIs based on HTTP POST and GET

Get Started

0. Install Google.Cloud.Functions.Templates
   • https://www.nuget.org/packages/Google.Cloud.Functions.Templates/
1. Create a new gcf-http project
   • Tutorial
2. Install the CommandQuery.GoogleCloudFunctions package from NuGet
   • PM> Install-Package CommandQuery.GoogleCloudFunctions
3. Create functions
   • Preferably named Command and Query
4. Create commands and command handlers
   • Implement ICommand and ICommandHandler<in TCommand>
   • Or ICommand<TResult> and ICommandHandler<in TCommand, TResult>
5. Create queries and query handlers
   • Implement IQuery<TResult> and IQueryHandler<in TQuery, TResult>
6. Configure services in Startup.cs

Commands

using CommandQuery.GoogleCloudFunctions; using Google.Cloud.Functions.Framework; using Google.Cloud.Functions.Hosting; using Microsoft.AspNetCore.Http; namespace CommandQuery.Sample.GoogleCloudFunctions { [FunctionsStartup(typeof(Startup))] public class Command(ICommandFunction commandFunction) : IHttpFunction { public async Task HandleAsync(HttpContext context) { var commandName = context.Request.Path.Value!.Substring("/api/command/".Length); await commandFunction.HandleAsync(commandName, context, context.RequestAborted); } } }

• The function is requested via HTTP POST with the Content-Type application/json in the header.
• The name of the command is the slug of the URL.
• The command itself is provided as JSON in the body.
• If the command succeeds; the response is empty with the HTTP status code 200.
• If the command fails; the response is an error message with the HTTP status code 400 or 500.

Commands with result:

• If the command succeeds; the response is the result as JSON with the HTTP status code 200.

Queries

using CommandQuery.GoogleCloudFunctions; using Google.Cloud.Functions.Framework; using Google.Cloud.Functions.Hosting; using Microsoft.AspNetCore.Http; namespace CommandQuery.Sample.GoogleCloudFunctions { [FunctionsStartup(typeof(Startup))] public class Query(IQueryFunction queryFunction) : IHttpFunction { public async Task HandleAsync(HttpContext context) { var queryName = context.Request.Path.Value!.Substring("/api/query/".Length); await queryFunction.HandleAsync(queryName, context, context.RequestAborted); } } }

• The function is requested via:
  • HTTP POST with the Content-Type application/json in the header and the query itself as JSON in the body
  • HTTP GET and the query itself as query string parameters in the URL
• The name of the query is the slug of the URL.
• If the query succeeds; the response is the result as JSON with the HTTP status code 200.
• If the query fails; the response is an error message with the HTTP status code 400 or 500.

Configuration

Configuration in Startup.cs:

using CommandQuery.GoogleCloudFunctions; using CommandQuery.Sample.Contracts.Commands; using CommandQuery.Sample.Contracts.Queries; using CommandQuery.Sample.Handlers; using CommandQuery.Sample.Handlers.Commands; using CommandQuery.Sample.Handlers.Queries; using Google.Cloud.Functions.Hosting; using Microsoft.AspNetCore.Builder; using Microsoft.AspNetCore.Hosting; using Microsoft.Extensions.DependencyInjection; namespace CommandQuery.Sample.GoogleCloudFunctions { public class Startup : FunctionsStartup { public override void ConfigureServices(WebHostBuilderContext context, IServiceCollection services) => services //.AddSingleton(new JsonSerializerOptions(JsonSerializerDefaults.Web)) // Add commands and queries .AddCommandFunction(typeof(FooCommandHandler).Assembly, typeof(FooCommand).Assembly) .AddQueryFunction(typeof(BarQueryHandler).Assembly, typeof(BarQuery).Assembly) // Add handler dependencies .AddTransient<IDateTimeProxy, DateTimeProxy>() .AddTransient<ICultureService, CultureService>(); public override void Configure(WebHostBuilderContext context, IApplicationBuilder app) { // Validation app.ApplicationServices.GetService<ICommandProcessor>()!.AssertConfigurationIsValid(); app.ApplicationServices.GetService<IQueryProcessor>()!.AssertConfigurationIsValid(); } } }

The extension methods AddCommandFunction and AddQueryFunction will add functions and all command/query handlers in the given assemblies to the IoC container. You can pass in a params array of Assembly arguments if your handlers are located in different projects. If you only have one project you can use typeof(Startup).Assembly as a single argument.

Testing

You can integration test your functions with the Google.Cloud.Functions.Testing package.

using System.Net; using System.Net.Http.Json; using CommandQuery.Sample.Contracts.Commands; using FluentAssertions; using Google.Cloud.Functions.Testing; using NUnit.Framework; namespace CommandQuery.Sample.GoogleCloudFunctions.Tests { public class CommandTests { [SetUp] public void SetUp() { Server = new FunctionTestServer<Command>(); Client = Server.CreateClient(); } [TearDown] public void TearDown() { Client.Dispose(); Server.Dispose(); } [Test] public async Task should_handle_command() { var response = await Client.PostAsJsonAsync("/api/command/FooCommand", new FooCommand { Value = "Foo" }); response.StatusCode.Should().Be(HttpStatusCode.OK); } [Test] public async Task should_handle_errors() { var response = await Client.PostAsJsonAsync("/api/command/FooCommand", new FooCommand()); await response.ShouldBeErrorAsync("Value cannot be null or empty"); } FunctionTestServer<Command> Server = null!; HttpClient Client = null!; } }

Samples

• CommandQuery.Sample.GoogleCloudFunctions
• CommandQuery.Sample.GoogleCloudFunctions.Tests