Reputation: 21031
I have a QueueTask Hosted service (.NET Core's new background service) that I'd like to test. My queuedHosted service looks like so:
public QueuedHostedService(IServiceProvider serviceProvider, IBackgroundTaskQueue taskQueue, ILoggerFactory loggerFactory)
{
TaskQueue = taskQueue;
_logger = loggerFactory.CreateLogger<QueuedHostedService>();
_serviceProvider = serviceProvider;
}
protected async override Task ExecuteAsync(CancellationToken stoppingToken)
{
using (var scope = _serviceProvider.CreateScope())
{
while (false == stoppingToken.IsCancellationRequested)
{
var workItem = await TaskQueue.DequeueAsync(stoppingToken);
try
{
await workItem(scope.ServiceProvider, stoppingToken);
}
catch (Exception ex)
{
this._logger.LogError(ex, $"Error occurred executing {nameof(workItem)}.");
}
}
}
}
It just reads tasks from the queue and executes them as they come in. I've already verified that the Hosted Service is working in Production. I wrote a test for it like so:
[TestMethod]
public async Task Verify_Hosted_Service_Executes_Task()
{
IServiceCollection services = new ServiceCollection();
services.AddSingleton<ILoggerFactory, NullLoggerFactory>();
services.AddHostedService<QueuedHostedService>();
services.AddSingleton<IBackgroundTaskQueue, BackgroundTaskQueue>();
var serviceProvider = services.BuildServiceProvider();
var backgroundQueue = serviceProvider.GetService<IBackgroundTaskQueue>();
var isExecuted = false;
backgroundQueue.QueueBackgroundWorkItem(async (sp, ct) => {
isExecuted = true;
});
await Task.Delay(10000);
Assert.IsTrue(isExecuted);
}
However, my callback is never hit. How can I get my task to execute on the Background Service?
Edit
I was mimicking the startup, and assumed my background service would just work, but apparently my service is never started.
How is the Hosted Service normally Started from .NET Core?
Upvotes: 29
Views: 25696
Reputation: 247641
Hosted services are started by the framework as part of the WebHost's start process
// Fire IHostedService.Start
await _hostedServiceExecutor.StartAsync(cancellationToken).ConfigureAwait(false);
via the HostedServiceExecutor
which would take a collection of all the registered IHostedService
, enumerate them and start them in turn
public HostedServiceExecutor(ILogger<HostedServiceExecutor> logger, IEnumerable<IHostedService> services)
{
_logger = logger;
_services = services;
}
public async Task StartAsync(CancellationToken token)
{
try
{
await ExecuteAsync(service => service.StartAsync(token));
}
catch (Exception ex)
{
_logger.ApplicationError(LoggerEventIds.HostedServiceStartException, "An error occurred starting the application", ex);
}
}
But since you are testing the hosted service on its own, you have to act as the framework and start the service yourself.
[TestMethod]
public async Task Verify_Hosted_Service_Executes_Task() {
IServiceCollection services = new ServiceCollection();
services.AddSingleton<ILoggerFactory, NullLoggerFactory>();
services.AddHostedService<QueuedHostedService>();
services.AddSingleton<IBackgroundTaskQueue, BackgroundTaskQueue>();
var serviceProvider = services.BuildServiceProvider();
var service = serviceProvider.GetService<IHostedService>() as QueuedHostedService;
var backgroundQueue = serviceProvider.GetService<IBackgroundTaskQueue>();
await service.StartAsync(CancellationToken.None);
var isExecuted = false;
backgroundQueue.QueueBackgroundWorkItem(async (sp, ct) => {
isExecuted = true;
});
await Task.Delay(10000);
Assert.IsTrue(isExecuted);
await service.StopAsync(CancellationToken.None);
}
Upvotes: 38