How do I implement .NET Core Health Checks on a Hosted Service?

Question

The question is just as asked on the title. It is simple to perform a check for the database operations, queries, commands and event store but I am clueless as to how/what is the best way to perform a health check on a hostedservice. Could anyone advice?

Does [this](https://learn.microsoft.com/en-us/aspnet/core/host-and-deploy/health-checks?view=aspnetcore-3.1) answer your question ? You need to configure specific endpoint in your application which then can be used for performing healthcheck probes by kubernetes. — mario, Feb 28 '20 at 11:46
@mario Nope! haha, i wish it was tho, I specifically want a HostedService to be checked for its health, i.e. its memory usage (if possible) or at least whether if it is still functioning properly or not. — Nicholas, Feb 29 '20 at 17:35
@ Nicholas, so unfortunatelly I won't be able to help you this time. ;) I couldn't find anything about performing health checks specifically on a hosted service either. Good luck! — mario, Feb 29 '20 at 18:06

score 7 · Accepted Answer · answered Apr 01 '20 at 14:44

Additionally from Simon B, this official Microsoft documentation has drafted out a complete guide to writing a health check structure for your Hosted services.

You need 3 elements:

The HealthCheck class for your hosted service
The HealthCheck Provider DI, along with the HealthCheck class' DI.
A HealthCheck publisher

score 6 · Answer 2 · answered Mar 03 '20 at 12:27

The IHostedService interface (and BackgroundService base implementation) has overridable methods StartAsync() and StopAsync(). In our background service we have:

public override Task StopAsync(CancellationToken cancellationToken)
{
      _logger.LogWarning("Background service stopping");
      return Task.CompletedTask;
}

You could use this to run whatever you want to notify in some way when your HostedService starts or stops.

If you need to have a way of polling the service, you could perhaps inject a singleton that has a simple status within it, that is set by these methods. Then, a health check controller on your API / website could also have that injected and read the status of the singleton. Something like this:

    public interface IHostedServiceStatus
    {
        bool IsHostedServiceRunning { get; set; }
    }

    public class HostedServiceStatus : IHostedServiceStatus
    {
        public bool IsHostedServiceRunning { get; set; }
    }

Set that up as a singleton, inject into your HostedService and set IsHostedServiceRunning on the StartAsync() and StopAsync() methods appropriately. Then also inject into your health check controller and read IsHostedServiceRunning.

Apologies simon, give me some time on this. Will follow ur guide and respond when i can! — Nicholas, Mar 22 '20 at 21:25

score 0 · Answer 3 · answered Aug 21 '23 at 12:53

Another option is to use the ExecuteTask property of the BackgroundService class:

/// <summary>
/// Gets the Task that executes the background operation.
/// </summary>
/// <remarks>
/// Will return <see langword="null"/> if the background operation hasn't started.
/// </remarks>
public virtual Task? ExecuteTask => _executeTask;

Using this you can derive the status of the background service as follows:

@if (service.ExecuteTask == null)
{
    // Status = "Loading"
}
else
{
    if(!service.ExecuteTask.IsCompleted)
    {
        // Status = "Running"
    }
    else
    {
        // Status = "Stopped"
    }
}

Alternatively you could even use the task's TaskStatus

How do I implement .NET Core Health Checks on a Hosted Service?

3 Answers3

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