how to handle DbContext lifetime in API / backgroundworker - asp.net-core

the past days I have been struggling with injecting a DbContext in MY background worker. On the one hand, I want to inject the dbContext in my backgorund worker, but on the other hand I also want to use it in my API.
The injecting in my API seems to work fine, but since my worker is a singleton, I can not follow the standard lifetime of scoped for my dbcontext, and I have to add it as transient.
I have already tried to create a unit of work, in which I can refresh the context myself in my worker, effectively creating some kind of scoped service. I would refresh the context every time the worker went through his loop once again. This worked, and the application was working as I wanted, but I was no longer able to properly test, since I would create a new DbContext myself in the code. I feel like there must be a better way for to handle this.
My project structure looks like the following:
API => contains controlers + models I use for post requests.
The API project needs to use my database, to get and post data. It uses the repositories for this
Core (class library) => contains some core models
Domain(class library) => Contains my domain models + repositories.
All database work goes through here
Worker => Contains some logic.
The worker needs to use my database, to get and post data. It uses the repositories for this
Services (class library) => Some services that contain some logic.
The worker uses my repositories to get to the database
Tests => Tests for all code.
I want to be able to to integrationTesting as well here.
I currently inject all repositories and services in both my API and worker:
Worker configureservices:
public static IHostBuilder CreateHostBuilder(string[] args) =>
Host.CreateDefaultBuilder(args)
.ConfigureServices((hostContext, services) =>
{
services.AddDbContext<CatAPIDbContext>(ServiceLifetime.Transient);
services.AddTransient(typeof(IFeedingProfileRepository), typeof(FeedingProfileRepository));
services.AddTransient(typeof(IFeedingTimesRepository), typeof(FeedingTimesRepository));
services.AddTransient(typeof(IFeedHistoryRepository), typeof(FeedHistoryRepository));
services.AddTransient(typeof(IMotorController), typeof(MotorController));
services.AddTransient(typeof(IFoodDispenser), typeof(FoodDispenser));
services.AddTransient(typeof(IGenericRepository<>), typeof(GenericRepository<>));
services.AddTransient(typeof(IFeedingTimeChecker), typeof(FeedingTimeChecker));
services.AddHostedService<Worker>();
});
(EDIT)Worker code:
public class Worker : BackgroundService
{
private readonly ILogger<Worker> _logger;
public IFeedingTimeChecker _feedingTimeChecker { get; }
public Worker(ILogger<Worker> logger, IFeedingTimeChecker feedingTimeChecker)
{
_logger = logger;
_feedingTimeChecker = feedingTimeChecker;
}
protected override async Task ExecuteAsync(CancellationToken stoppingToken)
{
while (!stoppingToken.IsCancellationRequested)
{
try
{
_logger.LogInformation("Worker running at: {time}", DateTimeOffset.Now);
_feedingTimeChecker.ResetFeedingTimesGivenIfNeeded();
_feedingTimeChecker.FeedIfNeeded();
}
catch(Exception ex)
{
_logger.LogError(ex.ToString());
}
await Task.Delay(10000, stoppingToken);
}
}
}
(EDIT)FeedingTimeChecker (called by worker)
private FeedingProfile _currentProfile { get; set; }
public DateTime lastResetDataFeedingTimes;
public DateTime lastProfileRefresh;
private readonly ILogger<FeedingTimeChecker> _logger;
private IFeedingProfileRepository _feedingProfileRepository { get; set; }
private IFeedingTimesRepository _feedingTimesRepository { get; set; }
private IFoodDispenser _foodDispenser { get; }
public FeedingTimeChecker(IFeedingProfileRepository feedingProfileRepository, IFeedingTimesRepository feedingTimesRepository,IFoodDispenser foodDispenser, ILogger<FeedingTimeChecker> logger)
{
lastResetDataFeedingTimes = DateTime.MinValue.Date;
lastProfileRefresh = DateTime.MinValue.Date;
_foodDispenser = foodDispenser;
_logger = logger;
_feedingTimesRepository = feedingTimesRepository;
_feedingProfileRepository = feedingProfileRepository;
}
public void UpdateCurrentProfile()
{
if(Time.GetDateTimeNow - TimeSpan.FromSeconds(5) > lastProfileRefresh)
{
_logger.LogInformation("Refreshing current profile");
_currentProfile = _feedingProfileRepository.GetCurrentFeedingProfile();
lastProfileRefresh = Time.GetDateTimeNow;
}
}
API configureServices:
public void ConfigureServices(IServiceCollection services)
{
services.AddMvcCore().SetCompatibilityVersion(CompatibilityVersion.Version_3_0);
services.AddDbContext<CatAPIDbContext>();
services.AddTransient(typeof(IFeedingProfileRepository), typeof(FeedingProfileRepository));
services.AddTransient(typeof(IFeedingTimesRepository), typeof(FeedingTimesRepository));
services.AddTransient(typeof(IFeedHistoryRepository), typeof(FeedHistoryRepository));
services.AddTransient(typeof(IMotorController), typeof(MotorController));
services.AddTransient(typeof(IFoodDispenser), typeof(FoodDispenser));
services.AddTransient(typeof(IGenericRepository<>), typeof(GenericRepository<>));
}
in my repositories I use the dbContext like the following:
public class GenericRepository<T> : IGenericRepository<T> where T : class
{
public CatAPIDbContext _dbContext { get; set; }
public GenericRepository(CatAPIDbContext dbContext)
{
_dbContext = dbContext;
}
public T GetById(object id)
{
return _dbContext.Set<T>().Find(id);
}
}
The result I would expect, is for my worker and API to behave correctly, always getting the lastest data and disposing of the dbContext on every single request, since I use a transient lifetime for my dbContext.
However, in my worker, I always get the following error:
The instance of entity type 'FeedingTime' cannot be tracked because another instance another instance of this type with the same key is already being tracked.
This error occurs when I try to set a column in the FeedingTime table.
A feedingProfile has 0-many feedingTimes, and the feedingProfile constantly retrieved.
Any solution where I can keep a testable clean codebase, but yet not run into this problem would be very welcome.
Thanks in advance

Related

How to start an ASP.NET Core BackgroundService on demand?

I want to be able to start fire-and-forget jobs in ASP.NET Core 2.2. I have tried the following:
services.AddHostedService<TestHostedService>();
public class TestHostedService : BackgroundService
{
private readonly ILogger _logger;
public TestHostedService(ILoggerFactory loggerFactory)
{
_logger = loggerFactory.CreateLogger<TestHostedService>();
}
public IBackgroundTaskQueue TaskQueue { get; }
protected async override Task ExecuteAsync(
CancellationToken cancellationToken)
{
_logger.LogInformation("TestHostedService is starting.");
_logger.LogInformation("TestHostedService is stopping.");
}
}
However, this automatically starts and I want to be able to start it on demand, similarly to how Hangfire allows:
BackgroundJob.Enqueue<TestJob>(x => x.DoWork());
This also allows the job to naturally use ASP.NET CORE DI.
Question: How to start an ASP.NET Core BackgroundService on demand?
###Background information
I am dealing with an application that needs to fire-and-forget various methods. The already written code looks like this:
Task.Run(() => RunSomething(_serviceScopeFactory));
This means that each method must explicitly deal with getting a scope and retrieving the dependencies which is quite ugly.
If you want to run the BackgroundService in the MVC controller or other service. You could try to inject the IServiceProvider to that class and then loop all the hosted service and find the background service, at last you could call the startasync method.
More details, you could refer to below codes:
Register the service in Startup.cs
services.AddHostedService<TestHostedService>();
Execute the background service in the controller:
public class HomeController : Controller
{
private readonly IServiceProvider _serviceProdiver;
public HomeController(IServiceProvider serviceProdiver) {
_serviceProdiver = serviceProdiver;
}
public async Task<IActionResult> Index()
{
var allBackgroundServices = _serviceProdiver.GetServices<IHostedService>();
foreach (var hostedService in allBackgroundServices)
{
if (hostedService.GetType() == typeof(TestHostedService))
{
await hostedService.StartAsync(CancellationToken.None);
}
}
return View();
}
}
Result:

How to inject HttpContextAccessor directly from ConfigureServices method

My goal is to set a username string based on the environment I'll be working on that must be:
an arbitrary string for the development and staging environment
the HttpContext.User.Identity.Name in production.
This is because I have to be able to simulate different kind of users and I achieve this by calling the FindByIdAsync method on my custom implementation of UserIdentity using this username string as a parameter, like this:
public class HomeController : Controller
{
UserManager<AppUser> userManager;
AppUser connectedUser;
public HomeController(UserManager<AppUser> usrMgr, IContextUser ctxUser)
{
connectedUser = usrMgr.FindByNameAsync(ctxUser.ContextUserId).Result;
}
}
I started creating three appsettings.{environment}.json file for the three usual development, staging and production environments; development and staging .json files both have this configuration:
...
"Data": {
...
"ConnectedUser" : "__ADMIN"
}
...
while the production environment configuration file doesn't have this key.
I have created a simple interface
public interface IContextUser
{
public string ContextUserId { get; }
}
and its implementation:
public class ContextUser : IContextUser
{
string contextUser;
IHttpContextAccessor contextAccessor;
public ContextUser(IHttpContextAccessor ctxAccessor, string ctxUser = null)
{
contextUser = ctxUser;
contextAccessor = ctxAccessor;
}
public string ContextUserId => contextUser ?? contextAccessor.HttpContext.User.Identity.Name;
}
Now, I thought of simply configuring the ConfigureServices method in the Startup class:
public void ConfigureServices(IServiceCollection services)
{
// --- add other services --- //
string ctxUser = Configuration["Data:ConnectedUser"];
services.AddSingleton(service => new ContextUser( ??? , ctxUser ));
}
but it needs an IHttpContextAccessor object, that seems unavailable at this stage of the application. How can I solve this issue?
The HttpContextAccessor makes use of a static AsyncLocal<T> property under the covers, which means that any HttpContextAccessor implementation will access the same data. This means you can simply do the following:
services.AddSingleton(c => new ContextUser(new HttpContextAccessor(), ctxUser));
// Don't forget to call this; otherwise the HttpContext property will be
// null on production.
services.AddHttpContextAccessor();
If you find this too implicit, or don't the HttpContextAccessor implementation from breaking in the future, you can also do the following:
var accessor = new HttpContextAccessor();
services.AddSingleton<IHttpContextAccessor>(accessor);
services.AddSingleton(c => new ContextUser(accessor, ctxUser));
Or you can "pull out" the registered instance out of the ServiceCollection class:
services.AddHttpContextAccessor();
var accessor = (IHttpContextAccessor)services.Last(
s => s.ServiceType == typeof(IHttpContextAccessor)).ImplementationInstance;
services.AddSingleton(c => new ContextUser(accessor, ctxUser));
What I find a more pleasant solution, however, especially from a design perspective, is to split the ContextUser class; it currently seems to implement two different solutions. You can split those:
public sealed class HttpContextContextUser : IContextUser
{
private readonly IHttpContextAccessor accessor;
public HttpContextContextUser(IHttpContextAccessor accessor) =>
this.accessor = accessor ?? throw new ArgumentNullException("accessor");
public string ContextUserId => this.accessor.HttpContext.User.Identity.Name;
}
public sealed class FixedContextUser : IContextUser
{
public FixedContextUser(string userId) =>
this.ContextUserId = userId ?? throw new ArgumentNullException("userId");
public string ContextUserId { get; }
}
Now, depending on the environment you're running in, you register either one of them:
public void ConfigureServices(IServiceCollection services)
{
services.AddHttpContextAccessor();
if (this.Configuration.IsProduction())
{
services.AddSingleton<IContextUser, HttpContextContextUser>();
}
else
{
string ctxUser = Configuration["Data:ConnectedUser"];
services.AddSingleton<IContextUser>(new FixedContextUser(ctxUser));
}
}

ASP.NET Core Integration Testing & Mocking using Moq

I have the following ASP.NET Core integration test using a custom WebApplicationFactory
public class CustomWebApplicationFactory<TEntryPoint> : WebApplicationFactory<TEntryPoint>
where TEntryPoint : class
{
public CustomWebApplicationFactory()
{
this.ClientOptions.AllowAutoRedirect = false;
this.ClientOptions.BaseAddress = new Uri("https://localhost");
}
public ApplicationOptions ApplicationOptions { get; private set; }
public Mock<IClockService> ClockServiceMock { get; private set; }
public void VerifyAllMocks() => Mock.VerifyAll(this.ClockServiceMock);
protected override TestServer CreateServer(IWebHostBuilder builder)
{
this.ClockServiceMock = new Mock<IClockService>(MockBehavior.Strict);
builder
.UseEnvironment("Testing")
.ConfigureTestServices(
services =>
{
services.AddSingleton(this.ClockServiceMock.Object);
});
var testServer = base.CreateServer(builder);
using (var serviceScope = testServer.Host.Services.CreateScope())
{
var serviceProvider = serviceScope.ServiceProvider;
this.ApplicationOptions = serviceProvider.GetRequiredService<IOptions<ApplicationOptions>>().Value;
}
return testServer;
}
}
which looks like it should work but the problem is that the ConfigureTestServices method is never being called, so my mock is never registered with the IoC container. You can find the full source code here.
public class FooControllerTest : IClassFixture<CustomWebApplicationFactory<Startup>>, IDisposable
{
private readonly HttpClient client;
private readonly CustomWebApplicationFactory<Startup> factory;
private readonly Mock<IClockService> clockServiceMock;
public FooControllerTest(CustomWebApplicationFactory<Startup> factory)
{
this.factory = factory;
this.client = factory.CreateClient();
this.clockServiceMock = this.factory.ClockServiceMock;
}
[Fact]
public async Task Delete_FooFound_Returns204NoContent()
{
this.clockServiceMock.SetupGet(x => x.UtcNow).ReturnsAsync(new DateTimeOffset.UtcNow);
var response = await this.client.DeleteAsync("/foo/1");
Assert.Equal(HttpStatusCode.NoContent, response.StatusCode);
}
public void Dispose() => this.factory.VerifyAllMocks();
}
I've blogged about ASP.NET Core Integration Testing & Mocking using Moq. It's not simple and requires some setup but I hope it helps someone out. Here is the basic code you need using ASP.NET Core 3.1:
Startup
The ConfigureServices and Configure methods in your applications Startup class must be virtual. This is so that we can iherit from this class in our tests and replace production versions of certain services with mock versions.
public class Startup
{
private readonly IConfiguration configuration;
private readonly IWebHostingEnvironment webHostingEnvironment;
public Startup(IConfiguration configuration, IWebHostingEnvironment webHostingEnvironment)
{
this.configuration = configuration;
this.webHostingEnvironment = webHostingEnvironment;
}
public virtual void ConfigureServices(IServiceCollection services) =>
...
public virtual void Configure(IApplicationBuilder application) =>
...
}
TestStartup
In your test project, override the Startup class with one that registers the mock and the mock object with IoC.
public class TestStartup : Startup
{
private readonly Mock<IClockService> clockServiceMock;
public TestStartup(IConfiguration configuration, IHostingEnvironment hostingEnvironment)
: base(configuration, hostingEnvironment)
{
this.clockServiceMock = new Mock<IClockService>(MockBehavior.Strict);
}
public override void ConfigureServices(IServiceCollection services)
{
services
.AddSingleton(this.clockServiceMock);
base.ConfigureServices(services);
services
.AddSingleton(this.clockServiceMock.Object);
}
}
CustomWebApplicationFactory
In your test project, write a custom WebApplicationFactory that configures the HttpClient and resolves the mocks from the TestStartup, then exposes them as properties, ready for our integration test to consume them. Note that I'm also changing the environment to Testing and telling it to use the TestStartup class for startup.
Note also that I've implemented IDisposable's `Dispose method to verify all of my strict mocks. This means I don't need to verify any mocks manually myself. Verification of all mock setups happens automatically when xUnit is disposing the test class.
public class CustomWebApplicationFactory<TEntryPoint> : WebApplicationFactory<TEntryPoint>
where TEntryPoint : class
{
public CustomWebApplicationFactory()
{
this.ClientOptions.AllowAutoRedirect = false;
this.ClientOptions.BaseAddress = new Uri("https://localhost");
}
public ApplicationOptions ApplicationOptions { get; private set; }
public Mock<IClockService> ClockServiceMock { get; private set; }
public void VerifyAllMocks() => Mock.VerifyAll(this.ClockServiceMock);
protected override void ConfigureClient(HttpClient client)
{
using (var serviceScope = this.Services.CreateScope())
{
var serviceProvider = serviceScope.ServiceProvider;
this.ApplicationOptions = serviceProvider.GetRequiredService<IOptions<ApplicationOptions>>().Value;
this.ClockServiceMock = serviceProvider.GetRequiredService<Mock<IClockService>>();
}
base.ConfigureClient(client);
}
protected override void ConfigureWebHost(IWebHostBuilder builder) =>
builder
.UseEnvironment("Testing")
.UseStartup<TestStartup>();
protected override void Dispose(bool disposing)
{
if (disposing)
{
this.VerifyAllMocks();
}
base.Dispose(disposing);
}
}
Integration Tests
I'm using xUnit to write my tests. Note that the generic type passed to CustomWebApplicationFactory is Startup and not TestStartup. This generic type is used to find the location of your application project on disk and not to start the application.
I setup a mock in my test and I've implemented IDisposable to verify all mocks for all my tests at the end but you can do this step in the test method itself if you like.
Note also, that I'm not using xUnit's IClassFixture to only boot up the application once as the ASP.NET Core documentation tells you to do. If I did so, I'd have to reset the mocks between each test and also you would only be able to run the integration tests serially one at a time. With the method below, each test is fully isolated and they can be run in parallel. This uses up more CPU and each test takes longer to execute but I think it's worth it.
public class FooControllerTest : CustomWebApplicationFactory<Startup>
{
private readonly HttpClient client;
private readonly Mock<IClockService> clockServiceMock;
public FooControllerTest()
{
this.client = this.CreateClient();
this.clockServiceMock = this.ClockServiceMock;
}
[Fact]
public async Task GetFoo_Default_Returns200OK()
{
this.clockServiceMock.Setup(x => x.UtcNow).ReturnsAsync(new DateTimeOffset(2000, 1, 1));
var response = await this.client.GetAsync("/foo");
Assert.Equal(HttpStatusCode.OK, response.StatusCode);
}
}
xunit.runner.json
I'm using xUnit. We need to turn off shadown copying, so any separate files like appsettings.json are placed in the right place beside the application DLL file. This ensures that our application running in an integration test can still read the appsettings.json file.
{
"shadowCopy": false
}
appsettings.Testing.json
Should you have configuration that you want to change just for your integration tests, you can add a appsettings.Testing.json file into your application. This configuration file will only be read in our integration tests because we set the environment name to 'Testing'.
The best way to handle this is to factor out parts of your Startup that will need to be substituted during test. For example, instead of calling services.AddDbContext<MyContext>(...); directly in ConfigureServices, create a virtual private method like:
protected virtual void ConfigureDatabase(IServiceCollection services)
{
services.AddDbContext<MyContext>(...);
}
Then, in your test project, create a class like TestStartup which derives from your SUT's Startup class. Then, you can override these virtual methods to sub in your test services, mocks, etc.
Finally, just do something like:
builder
.UseEnvironment("Testing")
.UseStartup<TestStartup>();
You should create a fake startup:
public class FakeStartup : Startup
{
public FakeStartup(IConfiguration configuration)
: base(configuration)
{
}
public override void ConfigureServices(IServiceCollection services)
{
base.ConfigureServices(services);
// Your fake go here
//services.AddScoped<IService, FakeService>();
}
}
Then use it with IClassFixture<CustomWebApplicationFactory<FakeStartup>>.
Make sure to make your original ConfigureServices method virtual.

How to send constantly updates using .Net Core SignalR?

I am new to SignalR and I would like to build such app -- every second a hub sends current time to all connected clients.
I found tutorial, but it is for .Net Framework (not Core): https://learn.microsoft.com/en-us/aspnet/signalr/overview/getting-started/tutorial-high-frequency-realtime-with-signalr So on one hand I don't know how to translate it to .Net Core SignalR, on the other hand I don't know how to write it from scratch (the limiting condition is the fact a hub is a volatile entity, so I cannot have state in it).
I need something static (I guess) with state -- let's say Broadcaster, when I create some cyclic action which in turn will send updates to clients. If such approach is OK, how to initialize this Broadcaster?
Currently I added such static class:
public static class CrazyBroadcaster
{
public static void Initialize(IServiceProvider serviceProvider)
{
var scope = serviceProvider.CreateScope();
var hub = scope.ServiceProvider.GetRequiredService<IHubContext<ChatHub>>();
var sub = Observable.Interval(TimeSpan.FromSeconds(1)).Subscribe(_ => hub.Clients.All.SendAsync("Bar", DateTimeOffset.UtcNow));
}
}
Yes, I know it is leaky. I call this method at the end of Startup.Configure, probably tons of violations here, but so far it is my best shot.
The missing piece was hosted service, i.e. the code that runs in the background -- https://learn.microsoft.com/en-US/aspnet/core/fundamentals/host/hosted-services?view=aspnetcore-2.2.
So my crazy class is now transformed into:
public sealed class HostedBroadcaster : IHostedService, IDisposable
{
private readonly IHubContext<ChatHub> hubContext;
private IDisposable subscription;
public HostedBroadcaster(IHubContext<ChatHub> hubContext)
{
this.hubContext = hubContext;
}
public void Dispose()
{
this.subscription?.Dispose();
}
public Task StartAsync(CancellationToken cancellationToken)
{
this.subscription = Observable.Interval(TimeSpan.FromSeconds(1)).Subscribe(_ => hubContext.Clients.All.SendAsync("Bar", DateTimeOffset.UtcNow));
return Task.CompletedTask;
}
public Task StopAsync(CancellationToken cancellationToken)
{
this.subscription?.Dispose();
return Task.CompletedTask;
}
}

Is there a reliable way to scope Ninject bound services to an NServicebus message handler?

I want to bind my Entity Framework context to be scoped per NServicebus message. Would the following code successfully do that?
Bind<IDbContext>().To<MyContext>()
.InScope(x => x.Kernel.Get<IBus>().CurrentMessageContext.Id);
Background
I have a NServicebus service that has several IMessageHandlers that read IEvents off an MSMQ Queue.
Each handler converts the message and saves it to a MS SQL Database by way of a particular IRepository sitting over an Entity Framework context.
The repositories needed by each handler are injected via ninject using NServicebus.ObjectBuilder.Ninject
public class Product
{
public string Code { get; set; }
public Category Category { get; set; }
}
public class Category
{
public string Code { get; set; }
}
public class SampleContext : IDbContext
{
IDbSet<Product> Products { get; }
IDbSet<Category> Categories{ get; }
}
public class ProductRepository : IProductRepository
{
private IDbContext _context;
public ProductRepository(IDbContext ctx) { _context = ctx; }
public void Add(Product p)
{
_context.Products.Add(p);
_context.SaveChanges();
}
}
public class CategoryRepository : ICategoryRepository
{
private IDbContext _context;
public CategoryRepository (IDbContext ctx) { _context = ctx; }
public Category GetByCode(string code)
{
return _context.Categories.FirstOrDefault(x => x.Code == code);
}
}
public class AddProductMessageHandler : IMessageHandler<IAddProductEvent>
{
private IProductRepository _products;
private ICategoryRepository _categories;
public AddProductMessageHandler(IProductRepository p, ICategoryRepository c)
{
_products = p;
_categories = c;
}
public void Handle(IAddProductEvent e)
{
var p = new Product();
p.Code = e.ProductCode;
p.Category = _categories.GetByCode(e.CategoryCode);
_products.Add(p);
}
}
Issue
If the EF context is bound in Transient scope (default) then each bound repository in the handler has it's own instance of the context.
Bind<IDbContext>().To<SampleContext>();
This causes issues if I load an object from one repository and then save it via another.
Likewise, if it's bound in Singleton scope, then the same context is used by all repositories, but then it slowly fills up with tracked changes and goobles up all my ram (and gets slower and slower to boot).
Bind<IDbContext>().To<SampleContext>().InSingletonScope();
Question
Ideally I would like each message handler to have 1 EF context that all required repositories (of that handler) use to load and save entities.
Is scoping the context to the current messages Id property a safe/reliable/good way of doing this?
Bind<IDbContext>().To<SampleContext>()
.InScope(x => x.Kernel.Get<IBus>().CurrentMessageContext.Id);
See my blogpost here which describes the scoping apart from NSB 4.0
http://www.planetgeek.ch/2013/01/16/nservicebus-unitofworkscope-with-ninject/
If you have 3.0 you can look into the current develop branch and port the extension methods to your code. You only have to change the scope name.
I'm not familiar with EF Context so please disregard if the answer below does not make any sense.
If EF Context is similar to a NH ISession, then I think the better option is to use a UoW the same way as NH implementation.
You can read more about UoW here.