The application was developed on ASP NET Core 3. To log user actions, I decided to use a single method in the Project class. Faced the problem of using one singleton dbContext from different threads.
Startup.cs
public void ConfigureServices(IServiceCollection services)
{
string connection = Configuration.GetConnectionString("ConnectionDB");
services.AddDbContext<DataBaseContext>(options => options.UseSqlServer(connection), ServiceLifetime.Transient, ServiceLifetime.Singleton);
services.AddSingleton<Project>();
}
Project.cs
public async Task AddUserLog(string action, string message, int userId)
{
try
{
UserLog userLog = new UserLog()
{
Action = action,
Message = message,
UserId = userId
Datepoint = DateTime.Now
};
_dbContext.UserLog.Add(userLog);
await _dbContext.SaveChangesAsync();
}
catch (Exception ex)
{
await AddSystemLog("Project", "AddUserLog", ex.Message);
}
}
SchemeController.cs
public class SchemeController : ControllerBase
{
private readonly Project _project;
public SchemeController(Project project)
{
_project = project;
}
[Authorize(Policy = "AdvancedControl")]
[HttpPost("[action]")]
public async Task SomeMethode()
{
for (int i = 0; i < 10; i++)
{
await _project.AddUserLog("Text", "Message", 42);
}
}
}
Already at the second iteration of the loop, I catch an exception in the AddUserLog method: "A second operation started on this context before a previous operation completed. This is usually caused by different threads using the same instance of DbContext."
I suggest several solutions:
Add the log to the buffer table and then save it to the database by timer. But this is not the best way out;
Block the method while it is being saved to the database.
But I don’t like any of the options.
Please tell me the correct approach in solving this issue.
So, you trying to use shared resource (singleton Project
class) to perform parallel operations (save UserLog
s) while your shared resource implementation is not thread-safe (exceptions raised).
You have at lease three ways to solve this:
Project
per scope instead of singletone;Project
There is no one "correct" way - all 3 are correct. Choose one you like (or combine several).
Usually using scoped dbcontext is recommended (because connections are pooled), but it's the creator of app who should decide.