Program.cs

using Microsoft.EntityFrameworkCore;
using Microsoft.FeatureManagement;
using OpenTelemetry.Metrics;
using WebAPI.Controllers;
using WebAPI.Persistence;

var builder = WebApplication.CreateBuilder(args);

// Add services to the container.
builder.Services.AddControllers();
builder.Services.AddEndpointsApiExplorer();
builder.Services.AddSwaggerGen();
builder.Services.AddHealthChecks()
    .AddCheck<HealthCheckDb>("Database Health Check");

builder.Services.AddDbContext<TodoDbContext>(opt =>
{
    opt.UseNpgsql($"User ID={Environment.GetEnvironmentVariable("POSTGRES_USER")};" +
                  $"Password={Environment.GetEnvironmentVariable("POSTGRES_PASSWORD")};" +
                  $"Host=postgres;" +
                  $"Port=5432;" +
                  $"Database={Environment.GetEnvironmentVariable("POSTGRES_DB")};" +
                  $"Pooling=true;" +
                  $"Minimum Pool Size=0;" +
                  $"Maximum Pool Size=100;" +
                  $"Connection Lifetime=0;");
});

builder.Services.AddFeatureManagement();
builder.Services.AddOpenTelemetry()
    .WithMetrics(telemetryBuilder =>
    {
        telemetryBuilder.AddPrometheusExporter();
        telemetryBuilder.AddMeter("Microsoft.AspNetCore.Hosting", "Microsoft.AspNetCore.Server.Kestrel");
        telemetryBuilder.AddView("http.server.request.duration",
            new ExplicitBucketHistogramConfiguration
            {
                Boundaries = [0, 0.005, 0.01, 0.025, 0.05, 0.075, 0.1, 0.25, 0.5, 0.75, 1, 2.5, 5, 7.5, 10]
            });
    });

var app = builder.Build();

//Ensure DB is created
using (var scope = app.Services.CreateScope())
{
    var dbContext = scope.ServiceProvider.GetRequiredService<TodoDbContext>();
    dbContext.Database.Migrate();
}

// Configure the HTTP request pipeline.
app.UseSwagger();
app.UseSwaggerUI();

app.UseAuthorization();

app.MapControllers();

app.MapHealthChecks("/health");

app.MapPrometheusScrapingEndpoint();

app.Run();