DelegateHealthCheck /8

[Rick-Anderson]

Fixes #31143

Error CS0122 'DelegateHealthCheck' is inaccessible due to its protection level
cc @francedot @JuergenGutsch @JoshKeegan @tdykstra @viktorpeacock

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aspnetcore/host-and-deploy/health-checks.md	Health checks in ASP.NET Core

[Rick-Anderson]

Error CS0122 'DelegateHealthCheck' is inaccessible due to its protection level
cc @francedot @JuergenGutsch

[JuergenGutsch]

https://github.com/dotnet/aspnetcore/blob/main/src/HealthChecks/HealthChecks/src/DelegateHealthCheck.cs
The DelegateHealthCheck is an internal class

[francedot]

Good catch. Instead of DelegateHealthCheck, you should be able to pass on a custom implementation of IHealthCheck as instance. The aspnetcore docs should therefore include the following to instruct how to use the new Periodic HealthChecks:

// PeriodicHealthCheck.cs or any other implementation
public class PeriodicHealthCheck : IHealthCheck
{
    private readonly Func<CancellationToken, Task<HealthCheckResult>> _check;

    public PeriodicHealthCheck (Func<CancellationToken, Task<HealthCheckResult>> check)
    {
        _check = check ?? throw new ArgumentNullException(nameof(check));
    }

    public Task<HealthCheckResult> CheckHealthAsync(HealthCheckContext context, CancellationToken cancellationToken = default) => _check(cancellationToken);

}

// Startup.cs or Program.cs
builder.Services.AddHealthChecks()
   .Add(new HealthCheckRegistration(
               name: "SampleHealthCheck1",
               instance: new PeriodicHealthCheck(_ => Task.FromResult(HealthCheckResult.Healthy(HealthyMessage))),
               failureStatus: null,
               tags: null,
               timeout: default)
          {
               Delay = TimeSpan.FromSeconds(40),
               Period = TimeSpan.FromSeconds(30)
          });

[JuergenGutsch]

The best way to add a delegate as a health check is to just use AddCheck or AddAsyncCheck defined in the HealthChecksBuilderDelegateExtensions:

    public static void MapHealthChecksComplete2(string[] args)
    {
        // <snippet_MapHealthChecksComplete2>
        var builder = WebApplication.CreateBuilder(args);

        builder.Services.AddHealthChecks()
           .AddAsyncCheck(name: "SampleHealthCheck1",
               check: _ => Task.FromResult(HealthCheckResult.Healthy("HealthyMessage")),
               tags: null,
               timeout: default);

        var app = builder.Build();

        app.MapHealthChecks("/healthz");

        app.Run();
        // </snippet_MapHealthChecksComplete2>
    }

[JuergenGutsch]

Can I push directly into the hc2 branch? If not the method shown above should work

[JuergenGutsch]

What @francedot proposed:

 public static void MapHealthChecksComplete2(string[] args)
 {
     // <snippet_MapHealthChecksComplete2>
     var builder = WebApplication.CreateBuilder(args);

     builder.Services.AddHealthChecks()
        .Add(new HealthCheckRegistration(
            name: "SampleHealthCheck1",
            instance: new SampleHealthCheck(),
            failureStatus: null,
            tags: null,
            timeout: default)
{
    Delay = TimeSpan.FromSeconds(40),
    Period = TimeSpan.FromSeconds(30)
});

     var app = builder.Build();

     app.MapHealthChecks("/healthz");

     app.Run();
     // </snippet_MapHealthChecksComplete2>
 }

[JuergenGutsch]

The best way to add a delegate as a health check is to just use AddCheck or AddAsyncCheck defined in the HealthChecksBuilderDelegateExtensions:

    public static void MapHealthChecksComplete2(string[] args)
    {
        // <snippet_MapHealthChecksComplete2>
        var builder = WebApplication.CreateBuilder(args);

        builder.Services.AddHealthChecks()
           .AddAsyncCheck(name: "SampleHealthCheck1",
               check: _ => Task.FromResult(HealthCheckResult.Healthy("HealthyMessage")),
               tags: null,
               timeout: default);

        var app = builder.Build();

        app.MapHealthChecks("/healthz");

        app.Run();
        // </snippet_MapHealthChecksComplete2>
    }

[JuergenGutsch]

Can I push directly into the hc2 branch? If not the method shown above should work

[Rick-Anderson]

Can I push directly into the hc2 branch? If not the method shown above should work

Try it, I don't think you have permission.

[Rick-Anderson]

@JuergenGutsch @francedot that fixed it, THANKS.

[Rick-Anderson]

@francedot @JuergenGutsch please review.

Public review of the doc build:

• download the HTML files
• unzip
• view HTML file in a browser.
• For links outside the doc, remove the review. from URL.

[JuergenGutsch]

@Rick-Anderson
I'm not sure if this sentence makes sense anymore since the DelegateHealthCheck isn't used directly:

The DelegateHealthCheck class enables setting Delay and Period on each health check individually.

I would propose something like this:

You can set Delay and Period on each HealthCheckRegistration individually.

[Rick-Anderson]

uld propose something like this:

You can set Delay and Period on each HealthCheckRegistration individually.

Much better.