// Copyright The OpenTelemetry Authors

// SPDX-License-Identifier: Apache-2.0

using System.Diagnostics.Metrics;

using Examples.AspNetCore;

using OpenTelemetry.Instrumentation.AspNetCore;

using OpenTelemetry.Logs;

using OpenTelemetry.Metrics;

using OpenTelemetry.Resources;

using OpenTelemetry.Trace;

var appBuilder = WebApplication.CreateBuilder(args);

// Note: Switch between OTLP/Console by setting UseTracingExporter in appsettings.json.

var tracingExporter = appBuilder.Configuration.GetValue("UseTracingExporter", defaultValue: "CONSOLE").ToUpperInvariant();

// Note: Switch between Prometheus/OTLP/Console by setting UseMetricsExporter in appsettings.json.

var metricsExporter = appBuilder.Configuration.GetValue("UseMetricsExporter", defaultValue: "CONSOLE").ToUpperInvariant();

// Note: Switch between Console/OTLP by setting UseLogExporter in appsettings.json.

var logExporter = appBuilder.Configuration.GetValue("UseLogExporter", defaultValue: "CONSOLE").ToUpperInvariant();

// Note: Switch between Explicit/Exponential by setting HistogramAggregation in appsettings.json

var histogramAggregation = appBuilder.Configuration.GetValue("HistogramAggregation", defaultValue: "EXPLICIT").ToUpperInvariant();

// Create a service to expose ActivitySource, and Metric Instruments

// for manual instrumentation

appBuilder.Services.AddSingleton<InstrumentationSource>();

// Add HttpClient to the service provider for dependency injection.

appBuilder.Services.AddHttpClient();

// Clear default logging providers used by WebApplication host.

appBuilder.Logging.ClearProviders();

// Configure OpenTelemetry logging, metrics, & tracing with auto-start using the

// AddOpenTelemetry extension from OpenTelemetry.Extensions.Hosting.

appBuilder.Services.AddOpenTelemetry()

.ConfigureResource(r => r

.AddService(

serviceName: appBuilder.Configuration.GetValue("ServiceName", defaultValue: "otel-test"),

serviceVersion: typeof(Program).Assembly.GetName().Version?.ToString() ?? "unknown",

serviceInstanceId: Environment.MachineName))

.WithTracing(builder =>

{

// Tracing

// Ensure the TracerProvider subscribes to any custom ActivitySources.

builder

.AddSource(InstrumentationSource.ActivitySourceName)

.SetSampler(new AlwaysOnSampler())

.AddHttpClientInstrumentation()

.AddAspNetCoreInstrumentation();

// Use IConfiguration binding for AspNetCore instrumentation options.

appBuilder.Services.Configure<AspNetCoreTraceInstrumentationOptions>(appBuilder.Configuration.GetSection("AspNetCoreInstrumentation"));

switch (tracingExporter)

{

case "OTLP":

builder.AddOtlpExporter(otlpOptions =>

{

// Use IConfiguration directly for Otlp exporter endpoint option.

otlpOptions.Endpoint = new Uri(appBuilder.Configuration.GetValue("Otlp:Endpoint", defaultValue: "http://localhost:4317"));

});

break;

default:

builder.AddConsoleExporter();

break;

}

})

.WithMetrics(builder =>

{

// Metrics

// Ensure the MeterProvider subscribes to any custom Meters.

builder

.AddMeter(InstrumentationSource.MeterName)

.SetExemplarFilter(ExemplarFilterType.TraceBased)

.AddRuntimeInstrumentation()

.AddHttpClientInstrumentation()

.AddAspNetCoreInstrumentation();

switch (histogramAggregation)

{

case "EXPONENTIAL":

builder.AddView(instrument =>

{

return instrument.GetType().GetGenericTypeDefinition() == typeof(Histogram<>)

? new Base2ExponentialBucketHistogramConfiguration()

: null;

});

break;

default:

// Explicit bounds histogram is the default.

// No additional configuration necessary.

break;

}

switch (metricsExporter)

{

case "PROMETHEUS":

builder.AddPrometheusExporter();

break;

case "OTLP":

builder.AddOtlpExporter(otlpOptions =>

{

// Use IConfiguration directly for Otlp exporter endpoint option.

otlpOptions.Endpoint = new Uri(appBuilder.Configuration.GetValue("Otlp:Endpoint", defaultValue: "http://localhost:4317"));

});

break;

default:

builder.AddConsoleExporter();

break;

}

})

.WithLogging(builder =>

{

// Note: See appsettings.json Logging:OpenTelemetry section for configuration.

switch (logExporter)

{

case "OTLP":

builder.AddOtlpExporter(otlpOptions =>

{

// Use IConfiguration directly for Otlp exporter endpoint option.

otlpOptions.Endpoint = new Uri(appBuilder.Configuration.GetValue("Otlp:Endpoint", defaultValue: "http://localhost:4317"));

});

break;

default:

builder.AddConsoleExporter();

break;

}

});

appBuilder.Services.AddControllers();

appBuilder.Services.AddEndpointsApiExplorer();

appBuilder.Services.AddSwaggerGen();

var app = appBuilder.Build();

if (app.Environment.IsDevelopment())

{

app.UseSwagger();

app.UseSwaggerUI();

}

app.UseHttpsRedirection();

app.UseAuthorization();

app.MapControllers();

// Configure OpenTelemetry Prometheus AspNetCore middleware scrape endpoint if enabled.

if (metricsExporter.Equals("prometheus", StringComparison.OrdinalIgnoreCase))

{

app.UseOpenTelemetryPrometheusScrapingEndpoint();

}

app.Run();