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Memory leak in Xamarin Forms app when using DI in a Task

I am creating a Xamarin Forms application, and I am using the Xamarin Profiler to show that I have a memory leak. I have tracked the memory leak down to where it is happening, but I can't understand WHY it is happening.
I have a class (we will call it MyClass for now). And that class is using a Timer to call a service once every second. That service makes a REST call to retrieve a bunch of information, and then serializes the results back into an object....
MyClass:
public class MyClass : ContentPage
{
private readonly IMyService myService;
public MyClass() : base()
{
}
protected override async void OnAppearing()
{
StartTimer();
}
private void StartTimer()
{
Task.Run(async() =>
{
while(true)
{
myService = ((App)App.Current)
.serviceProvider
.GetRequiredService<IMyService>();
//--- everytime I call myService.GetSystemStatus(), my allocated memory continues to rise
MyResponse response = await myService.GetSystemStatus();
Device.BeginInvokeOnMainThread(() =>
{
// update the UI here...
});
await Task.Delay(1000);
}
});
}
}
MyService (Singleton):
public class MyService : IMyService
{
private readonly IMyHttpClientFactory httpClientFactory;
public MyService(IMyHttpClientFactory httpClientFactory)
{
this.httpClientFactory = httpClientFactory;
}
public async Task<MyResponse> GetSystemStatus()
{
return await httpClientFactory.Create().GetAsync<MyResponse>(
"http://example.com/api/status"
);
}
}
MyHttpClientFactory (Singleton):
public class MyHttpClientFactory : IMyHttpClientFactory
{
private readonly IServiceProvider _serviceProvider;
public MyHttpClientFactory(IServiceProvider serviceProvider)
{
_serviceProvider = serviceProvider;
}
public MyHttpClient Create()
{
return _serviceProvider.GetRequiredService<MyHttpClient>();
}
}
MyHttpClient:
public class MyHttpClient : IDisposable
{
private HttpClient _httpClient;
public MyHttpClient ()
{
_httpClient = new HttpClient();
_httpClient.Timeout = TimeSpan.FromSeconds(10);
}
public async Task<T> GetAsync<T>(string url) where T : new()
{
string s = await GetStringAsync(url);
return JsonConvert.DeserializeObject<T>(s);
}
public async Task<string> GetStringAsync(string url)
{
using (var response = await _httpClient.GetAsync(url))
{
response.EnsureSuccessStatusCode();
return await response.Content.ReadAsStringAsync();
}
}
}
My services are defined as follows:
public partial class App : Application
public ServiceProvider serviceProvider;
public App()
{
IServiceCollection services = new ServiceCollection();
ConfigureServices(services);
serviceProvider = services.BuildServiceProvider();
InitializeComponent();
}
private void ConfigureServices(IServiceCollection services)
{
services.AddHttpClient<MyHttpClient>("MyHttpClient", x =>
{
x.Timeout = TimeSpan.FromSeconds(5);
});
services.AddSingleton<IMyHttpClientFactory, MyHttpClientFactory>();
services.AddSingleton<IMyService, MyService>();
}
}
Best I can tell, the memory is going up because I am referencing the DI MyService inside a separate thread. But I am not sure if this is the reason or if there is something else that would be causing the leak?
Any advice would be greatly appreciated!!!
Thanks!

From what I understand from your code and your comments, it looks like you're looping by calling StartTimer() inside the Device.StartTimer() method.
According to the documentation, Device.StartTimer() is recurring and will occur every X seconds, depending of your interval parameter.
By removing the call to StartTimer() (the one between t.Dispose() and return false of MyClass.StartTimer, your code should work as expected and you will not create a new timer every x seconds

What could be the cause of the leak:
Your MyHttpClient class implements the IDisposable interface, yet the code to use an instance of this class is not leveraging the disposable nature of the object.
Even though the internal HttpClient instance is wrapped in a using statement, the MyHttpClient instance will not be disposed of as you would expect.
// from MyHttpClient class
public async Task<MyResponse> GetSystemStatus()
{
// no using statement here
return await httpClientFactory.Create().GetAsync<MyResponse>(
"http://example.com/api/status"
);
}
// should be:
public async Task<MyResponse> GetSystemStatus()
{
using (var client = await httpClientFactory.Create())
{
return await client.GetAsync<MyResponse>("http://example.com/api/status");
}
}
Another thing to try is to change the location of the resolution of the MyService instance to inside the Task since this is where it is used. This will allow the task to own the resource, and allow it to be collected when the task is complete.
private void StartTimer()
{
Device.StartTimer(TimeSpan.FromSeconds(1), () =>
{
Task t = Task.Run(async() =>
{
// resolve the service here
myService = ((App)App.Current)
.serviceProvider
.GetRequiredService<IMyService>();
MyResponse response = await myService.GetSystemStatus();
Device.BeginInvokeOnMainThread(() =>
{
// update the UI here...
});
});
t.Wait();
t.Dispose();
StartTimer();
return false;
});
}
A couple of additional observations of your code:
In your HttpClientFactory's Create() method, you are resolving an instance of your client from the DI container.
Your MyHttpClient class has a default constructor which means the resolution is not needed since there are no additional dependencies requiring DI support.
Your code could simply return a new MyHttpClient() instance from the Create() method without the need for DI.
Your MyHttpClient also implements the IMyHttpClient interface, but your factory returns the concrete type. This means you need to either remove the interface as unnecessary or change the return type to be the interface type since the interface is redundant unless it is used.

Thank you all for your answers....
I finally figured out the source of the memory leak.
The problem was that I was referencing "MyService" like this:
myService = ((App)App.Current)
.serviceProvider
.GetRequiredService<IMyService>();
The problem was that the serviceProvider object was a public property on my App. So each time I referenced the provider inside my loop, it was creating the leak.
To get around this, I added an abstract method to each of my pages that implemented MyClass to return the service correctly using DI. This has corrected my memory leak issue....
Thanks all for the help!

I don't think that your timer logic is the cause of the leak.
But in case it is useful to you, here is a clean way to do work periodically, yet if work takes a long time, avoid events "piling up".
Given await/async, no Timer is needed.
(There is an alternative solution that starts/stops a single System.Timers.Timer, but I won't go into that here.)
Replace StartTimer() declaration with the following:
/// <summary> Runs until keepRunning() returns false.
/// Delays by "msecDelay" AFTER finishing the previous loop's non-UI work. </summary>
private void StartTaskLoopWhileKeepRunning(Func<bool> keepRunning, int msecDelay = 250)
{
Task.Run(async () =>
{
while (keepRunning())
{
// Do non-UI work here.
// ... possibly slow work ...
Device.BeginInvokeOnMainThread(() =>
{
// NOTE: This work will run in parallel with the next delay.
// ... Do UI work here. ...
});
// Non-UI thread sleeps for msec.
await Task.Delay(msecDelay);
}
});
}

Why is my WebApplicationFactory hanging for 5 minutes before timing out?

I'm trying to add some integration tests to my existing .net 6.0 project, but keep running into issues
Right now if I run the test, it hits the line await host.RunAsync(CancellationToken.None); in Program.cs and then just hangs forever and seemingly does nothing
Have I misunderstoof something? If not how can I troubleshoot this?
Program.cs
public /*static*/ class Program
{
public static async Task Main(string[] args)
{
var host = BuildWebHost(args);
await host.InitialiseAsync(CancellationToken.None);
await host.SeedAsync(CancellationToken.None);
await host.RunAsync(CancellationToken.None); // hangs here
}
}
Tests.cs
[Fact]
public void Test1Async()
{
using (var application = new WebApplicationFactory<Program>()
.WithWebHostBuilder(builder =>
{
builder.ConfigureServices(services =>
{
// set up servises
});
}))
{
var c = application.CreateClient(); // hangs here
}
}
It does eventually time out and give me this error
Message: 
System.InvalidOperationException : Timed out waiting for the entry point to build the IHost after 00:05:00. This timeout can be modified using the 'DOTNET_HOST_FACTORY_RESOLVER_DEFAULT_TIMEOUT_IN_SECONDS' environment variable.
Stack Trace: 
HostingListener.CreateHost()
<>c__DisplayClass10_0.b__0(String[] args)
DeferredHostBuilder.Build()
WebApplicationFactory1.CreateHost(IHostBuilder builder) DelegatedWebApplicationFactory.CreateHost(IHostBuilder builder) WebApplicationFactory1.ConfigureHostBuilder(IHostBuilder hostBuilder)
WebApplicationFactory1.EnsureServer() WebApplicationFactory1.CreateDefaultClient(DelegatingHandler[] handlers)
WebApplicationFactory1.CreateDefaultClient(Uri baseAddress, DelegatingHandler[] handlers) WebApplicationFactory1.CreateClient(WebApplicationFactoryClientOptions options)
WebApplicationFactory`1.CreateClient()
UnitTest1.Test1Async() line 35

Even though you didn't share the code for BuildWebHost() method I assume it is something like this public static IWebHostBuilder BuildWebHost(string[] args).
If so then simply rename this method to CreateWebHostBuilder. Name of the method is important because WebApplicationFactory internally is looking for it.
Straight from the summary on the constructor:
/// The <see cref="WebApplicationFactory{TEntryPoint}"/> will find the entry point class of <typeparamref name="TEntryPoint"/>
/// assembly and initialize the application by calling <c>IWebHostBuilder CreateWebHostBuilder(string [] args)</c>
/// on <typeparamref name="TEntryPoint"/>.
Source: https://github.com/dotnet/aspnetcore/blob/main/src/Mvc/Mvc.Testing/src/WebApplicationFactory.cs#L24

how to make a c# program run in background and at startup [duplicate]

I have console application and would like to run it as Windows service. VS2010 has project template which allow to attach console project and build Windows service.
I would like to not add separated service project and if possible integrate service code into console application to keep console application as one project which could run as console application or as windows service if run for example from command line using switches.
Maybe someone could suggest class library or code snippet which could quickly and easily transform c# console application to service?

I usually use the following techinque to run the same app as a console application or as a service:
using System.ServiceProcess
public static class Program
{
#region Nested classes to support running as service
public const string ServiceName = "MyService";
public class Service : ServiceBase
{
public Service()
{
ServiceName = Program.ServiceName;
}
protected override void OnStart(string[] args)
{
Program.Start(args);
}
protected override void OnStop()
{
Program.Stop();
}
}
#endregion
static void Main(string[] args)
{
if (!Environment.UserInteractive)
// running as service
using (var service = new Service())
ServiceBase.Run(service);
else
{
// running as console app
Start(args);
Console.WriteLine("Press any key to stop...");
Console.ReadKey(true);
Stop();
}
}
private static void Start(string[] args)
{
// onstart code here
}
private static void Stop()
{
// onstop code here
}
}
Environment.UserInteractive is normally true for console app and false for a service. Techically, it is possible to run a service in user-interactive mode, so you could check a command-line switch instead.

I've had great success with TopShelf.
TopShelf is a Nuget package designed to make it easy to create .NET Windows apps that can run as console apps or as Windows Services. You can quickly hook up events such as your service Start and Stop events, configure using code e.g. to set the account it runs as, configure dependencies on other services, and configure how it recovers from errors.
From the Package Manager Console (Nuget):
Install-Package Topshelf
Refer to the code samples to get started.
Example:
HostFactory.Run(x =>
{
x.Service<TownCrier>(s =>
{
s.ConstructUsing(name=> new TownCrier());
s.WhenStarted(tc => tc.Start());
s.WhenStopped(tc => tc.Stop());
});
x.RunAsLocalSystem();
x.SetDescription("Sample Topshelf Host");
x.SetDisplayName("Stuff");
x.SetServiceName("stuff");
});
TopShelf also takes care of service installation, which can save a lot of time and removes boilerplate code from your solution. To install your .exe as a service you just execute the following from the command prompt:
myservice.exe install -servicename "MyService" -displayname "My Service" -description "This is my service."
You don't need to hook up a ServiceInstaller and all that - TopShelf does it all for you.

So here's the complete walkthrough:
Create new Console Application project (e.g. MyService)
Add two library references: System.ServiceProcess and System.Configuration.Install
Add the three files printed below
Build the project and run "InstallUtil.exe c:\path\to\MyService.exe"
Now you should see MyService on the service list (run services.msc)
*InstallUtil.exe can be usually found here: C:\windows\Microsoft.NET\Framework\v4.0.30319\InstallUtil.ex‌​e
Program.cs
using System;
using System.IO;
using System.ServiceProcess;
namespace MyService
{
class Program
{
public const string ServiceName = "MyService";
static void Main(string[] args)
{
if (Environment.UserInteractive)
{
// running as console app
Start(args);
Console.WriteLine("Press any key to stop...");
Console.ReadKey(true);
Stop();
}
else
{
// running as service
using (var service = new Service())
{
ServiceBase.Run(service);
}
}
}
public static void Start(string[] args)
{
File.AppendAllText(#"c:\temp\MyService.txt", String.Format("{0} started{1}", DateTime.Now, Environment.NewLine));
}
public static void Stop()
{
File.AppendAllText(#"c:\temp\MyService.txt", String.Format("{0} stopped{1}", DateTime.Now, Environment.NewLine));
}
}
}
MyService.cs
using System.ServiceProcess;
namespace MyService
{
class Service : ServiceBase
{
public Service()
{
ServiceName = Program.ServiceName;
}
protected override void OnStart(string[] args)
{
Program.Start(args);
}
protected override void OnStop()
{
Program.Stop();
}
}
}
MyServiceInstaller.cs
using System.ComponentModel;
using System.Configuration.Install;
using System.ServiceProcess;
namespace MyService
{
[RunInstaller(true)]
public class MyServiceInstaller : Installer
{
public MyServiceInstaller()
{
var spi = new ServiceProcessInstaller();
var si = new ServiceInstaller();
spi.Account = ServiceAccount.LocalSystem;
spi.Username = null;
spi.Password = null;
si.DisplayName = Program.ServiceName;
si.ServiceName = Program.ServiceName;
si.StartType = ServiceStartMode.Automatic;
Installers.Add(spi);
Installers.Add(si);
}
}
}

Here is a newer way of how to turn a Console Application to a Windows Service as a Worker Service based on the latest .NET 6.
In Visual Studio 2022 you have out of the box Worker Service as a project template.
This gives you a main method and a Worker.cs on which you need a few more lines
Worker.cs on which I've added the StartAsync and StopAsync overrides to chose what my service does at start/stop.
namespace WorkerService
{
public class Worker : BackgroundService
{
private readonly ILogger<Worker> _logger;
public Worker(ILogger<Worker> logger)
{
_logger = logger;
}
protected override async Task ExecuteAsync(CancellationToken stoppingToken)
{
//do some operation
}
public override Task StartAsync(CancellationToken cancellationToken)
{
return base.StartAsync(cancellationToken);
}
public override Task StopAsync(CancellationToken cancellationToken)
{
return base.StopAsync(cancellationToken);
}
}
}
and Program.cs on which you will need to add .UseWindowsService()
using WorkerService;
IHost host = Host.CreateDefaultBuilder(args)
.ConfigureServices(services =>
{
services.AddHostedService<Worker>();
})
.UseWindowsService()
.Build();
await host.RunAsync();
And you will need to install the following NuGet for this method
Install-Package Microsoft.Extensions.Hosting.WindowsServices
Old answer -> .NET Core 3.1
If you create a Worker Service from Visual Studio 2019 it will give you almost everything you need for creating a Windows Service out of the box, which is also what you need to change to the console application in order to convert it to a Windows Service.
Here are the changes you need to do:
Install the following NuGet packages
Install-Package Microsoft.Extensions.Hosting.WindowsServices -Version 3.1.0
Install-Package Microsoft.Extensions.Configuration.Abstractions -Version 3.1.0
Change Program.cs to have an implementation like below:
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;
namespace ConsoleApp
{
class Program
{
public static void Main(string[] args)
{
CreateHostBuilder(args).UseWindowsService().Build().Run();
}
private static IHostBuilder CreateHostBuilder(string[] args) =>
Host.CreateDefaultBuilder(args)
.ConfigureServices((hostContext, services) =>
{
services.AddHostedService<Worker>();
});
}
}
and add Worker.cs where you will put the code which will be run by the service operations:
using Microsoft.Extensions.Hosting;
using System.Threading;
using System.Threading.Tasks;
namespace ConsoleApp
{
public class Worker : BackgroundService
{
protected override async Task ExecuteAsync(CancellationToken stoppingToken)
{
//do some operation
}
public override Task StartAsync(CancellationToken cancellationToken)
{
return base.StartAsync(cancellationToken);
}
public override Task StopAsync(CancellationToken cancellationToken)
{
return base.StopAsync(cancellationToken);
}
}
}
Installing the app as a Windows Service
When everything is ready, and the application has built successfully, you can use sc.exe to install your console application exe as a Windows Service with the following command:
sc.exe create DemoService binpath= "path/to/your/file.exe"

Firstly I embed the console application solution into the windows service solution and reference it.
Then I make the console application Program class public
/// <summary>
/// Hybrid service/console application
/// </summary>
public class Program
{
}
I then create two functions within the console application
/// <summary>
/// Used to start as a service
/// </summary>
public void Start()
{
Main();
}
/// <summary>
/// Used to stop the service
/// </summary>
public void Stop()
{
if (Application.MessageLoop)
Application.Exit(); //windows app
else
Environment.Exit(1); //console app
}
Then within the windows service itself I instantiate the Program and call the Start and Stop functions added within the OnStart and OnStop. See below
class WinService : ServiceBase
{
readonly Program _application = new Program();
/// <summary>
/// The main entry point for the application.
/// </summary>
static void Main()
{
ServiceBase[] servicesToRun = { new WinService() };
Run(servicesToRun);
}
/// <summary>
/// Set things in motion so your service can do its work.
/// </summary>
protected override void OnStart(string[] args)
{
Thread thread = new Thread(() => _application.Start());
thread.Start();
}
/// <summary>
/// Stop this service.
/// </summary>
protected override void OnStop()
{
Thread thread = new Thread(() => _application.Stop());
thread.Start();
}
}
This approach can also be used for a windows application / windows service hybrid

I hear your point at wanting one assembly to stop repeated code but, It would be simplest and reduce code repetition and make it easier to reuse your code in other ways in future if...... you to break it into 3 assemblies.
One library assembly that does all the work.
Then have two very very slim/simple projects:
one which is the commandline
one which is the windows service.

You can use
reg add HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run /v ServiceName /d "c:\path\to\service\file\exe"
And it will appear int the service list. I do not know, whether that works correctly though. A service usually has to listen to several events.
There are several service wrapper though, that can run any application as a real service. For Example Microsofts SrvAny from the Win2003 Resource Kit

Maybe you should define what you need, as far as I know, you can't run your app as Console or Service with command line, at the same time. Remember that the service is installed and you have to start it in Services Manager, you can create a new application wich starts the service or starts a new process running your console app. But as you wrote
"keep console application as one project"
Once, I was in your position, turning a console application into a service. First you need the template, in case you are working with VS Express Edition. Here is a link where you can have your first steps: C# Windows Service, this was very helpful for me. Then using that template, add your code to the desired events of the service.
To improve you service, there's another thing you can do, but this is not quick and/or easily, is using appdomains, and creating dlls to load/unload. In one you can start a new process with the console app, and in another dll you can just put the functionality the service has to do.
Good luck.

You need to seperate the functionality into a class or classes and launch that via one of two stubs. The console stub or service stub.
As its plain to see, when running windows, the myriad services that make up the infrastructure do not (and can't directly) present console windows to the user. The service needs to communicate with the user in a non graphical way: via the SCM; in the event log, to some log file etc. The service will also need to communicate with windows via the SCM, otherwise it will get shutdown.
It would obviously be acceptable to have some console app that can communicate with the service but the service needs to run independently without a requirement for GUI interaction.
The Console stub can very useful for debugging service behaviour but should not be used in a "productionized" environment which, after all, is the purpose of creating a service.
I haven't read it fully but this article seems to pint in the right direction.

I use a service class that follows the standard pattern prescribed by ServiceBase, and tack on helpers to easy F5 debugging. This keeps service data defined within the service, making them easy to find and their lifetimes easy to manage.
I normally create a Windows application with the structure below. I don't create a console application; that way I don't get a big black box popping in my face every time I run the app. I stay in in the debugger where all the action is. I use Debug.WriteLine so that the messages go to the output window, which docks nicely and stays visible after the app terminates.
I usually don't bother add debug code for stopping; I just use the debugger instead. If I do need to debug stopping, I make the project a console app, add a Stop forwarder method, and call it after a call to Console.ReadKey.
public class Service : ServiceBase
{
protected override void OnStart(string[] args)
{
// Start logic here.
}
protected override void OnStop()
{
// Stop logic here.
}
static void Main(string[] args)
{
using (var service = new Service()) {
if (Environment.UserInteractive) {
service.Start();
Thread.Sleep(Timeout.Infinite);
} else
Run(service);
}
}
public void Start() => OnStart(null);
}

How to implement a triggerless .NET Core Console App as a continuous Azure WebJob?

All the code samples I've seen so far for Azure WebJobs rely on some kind of trigger (e.g. TimerTrigger or QueueTrigger).
I am looking specifically at WebJobs SDK 3.x, by the way.
So. For a triggerless WebJob (Windows Service-alike one), am I expected to use NoAutomaticTrigger and find a way to kickoff my "main" code manually?
Or should I resort to implementing and registering a class that implements the IHostedService interface?
So far that's the approach I'm taking but it feels more of a hack than a recommended way.
I have not even tried to deploy this code and only ran it on my local machine, so I am afraid that the publishing process will confirm my code is not suitable for Azure WebJobs in its current form.
EntryPoint.cs
This is how the application is being bootstrap when the process is starting.
using Microsoft.Azure.ServiceBus;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;
namespace AbcCorp.Jobs
{
public static class Program
{
static async Task Main(string[] args)
{
var config = new ConfigurationBuilder()
.SetBasePath(Directory.GetCurrentDirectory())
.AddJsonFile("appsettings.json", optional: false, reloadOnChange: true)
.AddJsonFile($"appsettings.{Environment.GetEnvironmentVariable("ASPNETCORE_ENVIRONMENT")}.json", false)
.Build();
var hostBuilder = new HostBuilder()
.ConfigureWebJobs(builder => { builder.AddAzureStorageCoreServices(); })
.ConfigureServices(serviceCollection =>
{
ConfigureServices(serviceCollection, config);
serviceCollection.AddHostedService<ConsoleApplication>();
});
using (var host = hostBuilder.Build())
await host.RunAsync();
}
private static IServiceCollection ConfigureServices(IServiceCollection services, IConfigurationRoot configuration)
{
services.AddTransient<ConsoleApplication>();
// ... more DI registrations
return services;
}
}
}
ConsoleApplication.cs
This would normally be implemented as a function with a trigger.
The thing is, I want this code to only run once on the process startup.
It will start listening on the service bus events using the regular Microsoft.Azure.ServiceBus SDK package.
using System.Threading;
using System.Threading.Tasks;
using Microsoft.Extensions.Hosting;
using AbcCorp.Internal.Microsoft.Azure.ServiceBus;
using AbcCorp.Api.Messaging;
namespace AbcCorp.Jobs
{
public sealed class ConsoleApplication: IHostedService
{
private readonly IReceiver<SubmissionNotification> _messageReceiver;
private readonly MessageHandler _messageHandler;
public ConsoleApplication(IReceiver<SubmissionNotification> messageReceiver, MessageHandler messageHandler)
{
_messageReceiver = messageReceiver;
_messageHandler = messageHandler;
}
public Task StartAsync(CancellationToken cancellationToken)
{
_messageReceiver.StartListening(_messageHandler.HandleMessage, _messageHandler.HandleException);
return Task.Delay(Timeout.Infinite);
}
public Task StopAsync(CancellationToken cancellationToken)
{
_messageReceiver.Dispose();
return Task.CompletedTask;
}
}
}

So you want a console application to run in a WebJob and listen to messages. You don't really care about WebJob magic like triggers, it's just a place to run your console app. I've done the exact same thing before.
I found the IHostedService abstraction to be very helpful, but I didn't like their SDK. I found it bloated and hard to use. I didn't want to take a large dependency in order use a large array of special magic Azure stuff, when all I wanted to do was run a console application in a WebJob for now, and maybe move it elsewhere later.
So I ended just deleting that dependency, stealing the Shutdown code from the SDK and writing my own Service Host. The result is on my Github Repo azure-webjob-host. Feel free to use it or raid it for ideas. I don't know, maybe if I did it again I'd have another attempt at getting the SDK to work, but I present this is a bit of an alternative to the SDK.
Basically I wrote an IServiceHost not too different from yours (except that StartAsync exited when stuff started instead of just hanging). Then I wrote my own service host, which is basically just a loop:
await _service.StartAsync(cancellationToken);
while (!token.IsCancellationRequested){await Task.Delay(1000);}
await _service.StopAsync(default);
Then I stole the WebJobsShutdownWatcher code from their repo.
Then I created an IServiceHost that started my message handler. (I was using Rabbit, which has nothing to do with triggers or azure stuff)
public class MessagingService : IHostedService, IDisposable
{
public MessagingService(ConnectionSettings connectionSettings,
AppSubscriberSettings subscriberSettings,
MessageHandlerTypeMapping[] messageHandlerTypeMappings,
ILogger<MessagingService> logger)
{
....
}
public async Task StartAsync(CancellationToken cancellationToken)
{
cancellationToken.ThrowIfCancellationRequested();
await Task.WhenAll(subscribers.Value.Select(s => s.StartSubscriptionAsync()));
}
public async Task StopAsync(CancellationToken cancellationToken)
{
...
}
public void Dispose()
{
...
}
}
Then I put that all together into something like this:
IHostedService myService = new MyService();
using (var host = new ServiceHostBuilder().HostService(myService))
{
await host.RunAsync(default);
}

I have some workers attached to service bus topics and what we do is the following (ServiceBusClient is a custom Class that contains our Subscription Client):
public override Task StartAsync(CancellationToken cancellationToken)
{
_serviceBusClient.RegisterOnMessageHandlerAndReceiveMessages(MessageReceivedAsync);
_logger.LogDebug($"Started successfully the Import Client. Listening for messages...");
return base.StartAsync(cancellationToken);
}
public void RegisterOnMessageHandlerAndReceiveMessages(Func<Message, CancellationToken, Task> ProcessMessagesAsync)
{
// Configure the message handler options in terms of exception handling, number of concurrent messages to deliver, etc.
var messageHandlerOptions = new MessageHandlerOptions(ExceptionReceivedHandler)
{
// Maximum number of concurrent calls to the callback ProcessMessagesAsync(), set to 1 for simplicity.
// Set it according to how many messages the application wants to process in parallel.
MaxConcurrentCalls = 1,
// Indicates whether MessagePump should automatically complete the messages after returning from User Callback.
// False below indicates the Complete will be handled by the User Callback as in `ProcessMessagesAsync` below.
AutoComplete = false
};
// Register the function that processes messages.
SubscriptionClient.RegisterMessageHandler(ProcessMessagesAsync, messageHandlerOptions);
}
And then you can use DI to instantiate your service bus client and inject on the constructor of your Worker class.
Here i have the initialization of the singleton instance of my custom class Service Bus Client
services.AddSingleton<IServiceBusClient, ServiceBusClient>((p) =>
{
var diagnostics = p.GetService<EventHandling>();
var sbc = new ServiceBusClient(
programOptions.Endpoint,
programOptions.TopicName,
programOptions.Subscriber,
programOptions.SubscriberKey);
sbc.Exception += exception => diagnostics.HandleException(exception);
return sbc;
});
Then on this custom class, i initialize my subscription client
public ServiceBusClient(
string endpoint,
string topicName,
string subscriberName,
string subscriberKey, ReceiveMode mode = ReceiveMode.PeekLock)
{
var connBuilder = new ServiceBusConnectionStringBuilder(endpoint, topicName, subscriberName, subscriberKey);
var connectionString = connBuilder.GetNamespaceConnectionString();
ConnectionString = connectionString;
TopicName = topicName;
SubscriptionName = topicName;
SubscriptionClient = new SubscriptionClient(connectionString, topicName, subscriberName, mode);
}

You can check #george chen's answer from this post How to create service bus trigger webjob?
where instead of creating a receiver and registering a message handler, you can use the in built queue trigger and and write your message handler logic inside it.

How to run multiple BackgroundService parallel in .net core 3.0?

How is it possible to run multiple IHostedServices in parallel?
I use the WorkerService in .Net Core 3.0 and want both services to run parallel. Currently the second service is waiting for the first one to finish. Both services should run endlessly.
public static IHostBuilder CreateHostBuilder(string[] args)
{
return Host.CreateDefaultBuilder(args)
.ConfigureServices((hostContext, services) =>
{
services.AddHostedService<ServiceA>();
services.AddHostedService<ServiceB>();
});
}
A service looks like this:
public class ServiceA : BackgroundService
{
protected override async Task ExecuteAsync(CancellationToken stoppingToken)
{
do
{
Console.WriteLine("Sample");
await Task.Delay(5000, stoppingToken);
} while (!stoppingToken.IsCancellationRequested);
}
}
// edit:
Very reluctantly I would use a Task.Run(() => method()); method like this. But of course this way always works:
public class ServiceA : BackgroundService
{
public override Task StartAsync(CancellationToken cancellationToken)
{
Task.Factory.StartNew(() => ExecuteAsync(cancellationToken), cancellationToken);
return Task.CompletedTask;
}
}

I asked myself a similar question and made some search but couldn't find a good answer.
I solved the issue running every background service in Task.Run with a cancellation token from BackgroundService.ExecuteAsync()
I have 2 services like you.
public class BackgroundService1: BackgroundService
{
public BackgroundService1()
{
}
protected override Task ExecuteAsync(CancellationToken stoppingToken)
{
Task.Run(async () =>
{
await DoWork(stoppingToken);
}, stoppingToken);
return Task.CompletedTask;
}
}
//Second service is just like the first one:
public class BackgroundService2: BackgroundService
{
public BackgroundService2()
{
}
protected override Task ExecuteAsync(CancellationToken stoppingToken)
{
Task.Run(async () =>
{
await DoWork(stoppingToken);
}, stoppingToken);
return Task.CompletedTask;
}
}
and register them in Program.cs
public static IHostBuilder CreateHostBuilder(string[] args) =>
Host.CreateDefaultBuilder(args)
.ConfigureServices((hostContext, services) =>
{
services.AddHostedService<BackgroundService1>();
services.AddHostedService<BackgroundService2>();
})
.UseWindowsService()

I've had the same kind of issue: Multiple service that do different work at different frequencies.
When looking into it, BackgroundService seems to be designed for sequential execution (an infinite loop based service's worst enemy).
After getting a hint from this thread, I found the solution that works for my case using Microsoft's Timer Service example.
The base TimerService implements IHostedService and IAsyncDisposable:
StartAsync() starts the timer on the DoWork()
DoWork() is your overridable main work procedure.
StopAsync() stops the timer gracefully.
DisposeAsync() cleans up.
I've tested by deriving multiple TimerServices with different execution frequencies and adding them with services.AddHostedService<>();.
They all start and run at the same time, do their bit on clock.
/!\ It is not Task based as it uses timer events. Just pointing this out because I've already had quite a difficult troubleshooting experience the one time I mixed time-based events and Tasks /!\

No need to manually create a task. The default StartAsync calls ExecuteAsync and returns that task to be awaited somewhere else.
https://github.com/aspnet/Hosting/blob/master/src/Microsoft.Extensions.Hosting.Abstractions/BackgroundService.cs#L30
So, you can do return base.StartAsync(cancellationToken) before returning Task.Completed in StartAsync.