Bits of .NET

❤️ Is Your App Really Healthy?

App running but database down? Cache not responding? Health checks test dependencies. Perfect for load balancer readiness probes.

📝 Basic Setup

// Program.cs
builder.Services.AddHealthChecks()
    .AddDbContextCheck()
    .AddUrlGroup(new Uri("https://api.example.com"))

var app = builder.Build();
app.MapHealthChecks("/health/ready", new HealthCheckOptions
{
    Predicate = _ => true,
    ResponseWriter = UIResponseWriter.WriteHealthCheckUIResponse
});
app.MapHealthChecks("/health/live", new HealthCheckOptions
{
    Predicate = _ => false  // Just checks if app is running
});

🎯 Custom Health Check

public class DatabaseHealthCheck : IHealthCheck
{
    private readonly AppDbContext _db;
    
    public DatabaseHealthCheck(AppDbContext db) => _db = db;
    
    public async Task CheckHealthAsync(
        HealthCheckContext context,
        CancellationToken cancellationToken)
    {
        try
        {
            await _db.Database.ExecuteSqlRawAsync("SELECT 1", cancellationToken);
            return HealthCheckResult.Healthy("Database is responding");
        }
        catch (Exception ex)
        {
            return HealthCheckResult.Unhealthy("Database failed", ex);
        }
    }
}

// Register
builder.Services.AddHealthChecks()
    .AddCheck("database_check", tags: new[] { "ready" });

✅ Health Check UI

• Install: AspNetCore.HealthChecks.UI
• Provides dashboard at /healthchecks-ui
• Shows history of health status changes
• Can send alerts on failure