What is Health Check? How to Use It in .NET 9?

Health checks are essential for monitoring the health and availability of your application and its dependencies. They allow automated systems (like Kubernetes, Azure, or AWS) to detect when your app is down or degraded.

Why Use Health Checks?

Modern applications rely on many external systems:

• Databases
• Message queues
• Third-party APIs

If any of these fail, you want your orchestration system to know immediately and respond (like restarting the container or redirecting traffic).

Types of Health Checks

• Liveness probes → Is the app running at all?
• Readiness probes → Is the app ready to serve requests?

Example in .NET 9

Step 1: Add NuGet Package

dotnet add package Microsoft.Extensions.Diagnostics.HealthChecks

Step 2: Configure Health Checks in Program.cs

var builder = WebApplication.CreateBuilder(args);

builder.Services.AddHealthChecks()
    .AddSqlServer(builder.Configuration["ConnectionStrings:DefaultConnection"])
    .AddRedis(builder.Configuration["Redis:ConnectionString"]);

var app = builder.Build();

app.MapHealthChecks("/health");

app.Run();

Step 3: Access the Health Endpoint

Visit https://yourapp.com/health and you’ll see a JSON summary of system status.

Example Output

{
    "status": "Healthy",
    "results": {
        "SqlServer": { "status": "Healthy" },
        "Redis": { "status": "Healthy" }
    }
}

Best Practices

• Separate liveness and readiness checks
• Protect health endpoints (avoid leaking internal details)
• Integrate with your hosting platform’s monitoring tools

Health checks help ensure your .NET 9 apps stay resilient and self-healing in production.