Aspire Health Check Bug

This repository showcases a bug in .NET Aspire.

Steps to reproduce this bug

1. Create a new project using the template .NET Aspire Starter App
2. In the Web project create a new class called ApiServiceHealthCheck
3. Copy the following code into ApiServiceHealthCheck.cs file:

public class ApiServiceHealthCheck(HttpClient httpClient) : IHealthCheck
{
    public async Task<HealthCheckResult> CheckHealthAsync(HealthCheckContext context, CancellationToken cancellationToken = default)
    {
        var response = await httpClient.GetAsync("http://apiservice/health", cancellationToken).ConfigureAwait(false);

        return response.IsSuccessStatusCode ? HealthCheckResult.Healthy() : HealthCheckResult.Unhealthy();
    }
}

4. In the Web project open Program.cs file and add the following code builder.Services.AddHealthChecks().AddCheck<ApiServiceHealthCheck>("apiservice"); just before var app = builder.Build();
5. In the AppHost project ensure that both projects (apiservice and webfrontend) have .WithHttpHealthCheck("/health", 200, "http")
6. Run the AppHost project, open the dashboard and click on Traces tab
7. You should now see a health check spam

A possible way to fix this bug

1. In the ServiceDefaults project open Extensions.cs file and edit AddHttpClientInstrumentation() method found inside .WithTracing(tracing => ... omitted for abbreviation ...) in ConfigureOpenTelemetry method:

.AddHttpClientInstrumentation(options =>
{
    options.FilterHttpRequestMessage = (request) =>
    {
        return !request.RequestUri?.PathAndQuery.Contains("/health") ?? true;
    };
})

2. Run the AppHost project, open the dashboard and click on Traces tab
3. You should no longer see any health check spam

To consider: In theory there could be a request that gets filtered out but has nothing to do with a health check.