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
