Add telemetry

src/DiscordTranslationBot/DiscordTranslationBot.csproj

@@ -14,6 +14,11 @@
             <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
         </PackageReference>
         <PackageReference Include="Microsoft.Extensions.Http.Resilience" Version="8.9.1"/>
+        <PackageReference Include="OpenTelemetry.Exporter.OpenTelemetryProtocol" Version="1.9.0"/>
+        <PackageReference Include="OpenTelemetry.Exporter.Prometheus.AspNetCore" Version="1.9.0-beta.2"/>
+        <PackageReference Include="OpenTelemetry.Extensions.Hosting" Version="1.9.0"/>
+        <PackageReference Include="OpenTelemetry.Instrumentation.AspNetCore" Version="1.9.0"/>
+        <PackageReference Include="OpenTelemetry.Instrumentation.Http" Version="1.9.0"/>
         <PackageReference Include="Refit.HttpClientFactory" Version="7.2.1"/>
         <PackageReference Include="Unicode.net" Version="2.0.0"/>
     </ItemGroup>

src/DiscordTranslationBot/Program.cs

@@ -5,22 +5,28 @@
 using DiscordTranslationBot.Extensions;
 using DiscordTranslationBot.Mediator;
 using DiscordTranslationBot.Providers.Translation;
+using DiscordTranslationBot.Telemetry;
 using HealthChecks.UI.Client;
 using Microsoft.AspNetCore.Diagnostics.HealthChecks;
 using DiscordEventListener = DiscordTranslationBot.Discord.DiscordEventListener;
 
 var builder = WebApplication.CreateSlimBuilder(args);
+
+// Logging.
 builder.Logging.AddSimpleConsole(o => o.TimestampFormat = "HH:mm:ss.fff ");
 
-// Set up configuration.
+// Telemetry.
+builder.AddTelemetry();
+
+// Configuration.
 builder
     .Services
     .AddOptions<DiscordOptions>()
     .Bind(builder.Configuration.GetRequiredSection(DiscordOptions.SectionName))
     .ValidateDataAnnotations()
     .ValidateOnStart();
 
-// Set up services.
+// Main services.
 builder
     .Services
     .AddTranslationProviders(builder.Configuration)
@@ -54,6 +60,7 @@
 
 var app = builder.Build();
 
+app.UseTelemetry();
 app.UseRateLimiter();
 
 app

src/DiscordTranslationBot/Telemetry/TelemetryExtensions.cs

@@ -0,0 +1,66 @@
+using Microsoft.Extensions.Options;
+using OpenTelemetry.Exporter;
+using OpenTelemetry.Logs;
+using OpenTelemetry.Metrics;
+using OpenTelemetry.Resources;
+using OpenTelemetry.Trace;
+
+namespace DiscordTranslationBot.Telemetry;
+
+internal static class TelemetryExtensions
+{
+    public static void AddTelemetry(this WebApplicationBuilder builder)
+    {
+        var section = builder.Configuration.GetSection(TelemetryOptions.SectionName);
+        builder.Services.AddOptions<TelemetryOptions>().Bind(section).ValidateDataAnnotations().ValidateOnStart();
+
+        var options = section.Get<TelemetryOptions>();
+        if (options?.Enabled != true)
+        {
+            return;
+        }
+
+        var headers = $"X-Seq-ApiKey={options.ApiKey}";
+
+        builder.Logging.AddOpenTelemetry(
+            o => o.AddOtlpExporter(
+                e =>
+                {
+                    e.Protocol = OtlpExportProtocol.HttpProtobuf;
+                    e.Endpoint = options.LoggingEndpointUrl!;
+                    e.Headers = headers;
+                }));
+
+        builder
+            .Services
+            .AddOpenTelemetry()
+            .ConfigureResource(
+                b => b
+                    .AddService(builder.Environment.ApplicationName)
+                    .AddAttributes(
+                        new Dictionary<string, object> { ["environment"] = builder.Environment.EnvironmentName }))
+            .WithMetrics(b => b.AddAspNetCoreInstrumentation().AddHttpClientInstrumentation().AddPrometheusExporter())
+            .WithTracing(
+                b => b
+                    .AddAspNetCoreInstrumentation()
+                    .AddHttpClientInstrumentation()
+                    .AddOtlpExporter(
+                        e =>
+                        {
+                            e.Protocol = OtlpExportProtocol.HttpProtobuf;
+                            e.Endpoint = options.TracingEndpointUrl!;
+                            e.Headers = headers;
+                        }));
+    }
+
+    public static void UseTelemetry(this WebApplication app)
+    {
+        var options = app.Services.GetRequiredService<IOptions<TelemetryOptions>>();
+        if (!options.Value.Enabled)
+        {
+            return;
+        }
+
+        app.MapPrometheusScrapingEndpoint("/_metrics");
+    }
+}

src/DiscordTranslationBot/Telemetry/TelemetryOptions.cs

@@ -0,0 +1,58 @@
+using System.ComponentModel.DataAnnotations;
+
+namespace DiscordTranslationBot.Telemetry;
+
+public sealed class TelemetryOptions : IValidatableObject
+{
+    /// <summary>
+    /// Configuration section name for <see cref="TelemetryOptions" />.
+    /// </summary>
+    public const string SectionName = "Telemetry";
+
+    /// <summary>
+    /// Flag indicating whether telemetry is enabled.
+    /// </summary>
+    public bool Enabled { get; init; }
+
+    /// <summary>
+    /// The API key for Seq used by <see cref="LoggingEndpointUrl" /> and <see cref="TracingEndpointUrl" />.
+    /// </summary>
+    public string? ApiKey { get; init; }
+
+    /// <summary>
+    /// The URL for logging endpoint.
+    /// </summary>
+    public Uri? LoggingEndpointUrl { get; init; }
+
+    /// <summary>
+    /// The URL for tracing endpoint.
+    /// </summary>
+    public Uri? TracingEndpointUrl { get; init; }
+
+    public IEnumerable<ValidationResult> Validate(ValidationContext validationContext)
+    {
+        if (Enabled)
+        {
+            if (string.IsNullOrWhiteSpace(ApiKey))
+            {
+                yield return new ValidationResult(
+                    $"{nameof(TelemetryOptions)}.{nameof(ApiKey)} is required.",
+                    [nameof(ApiKey)]);
+            }
+
+            if (LoggingEndpointUrl?.IsAbsoluteUri != true)
+            {
+                yield return new ValidationResult(
+                    $"{nameof(TelemetryOptions)}.{nameof(LoggingEndpointUrl)} is must be an absolute URI.",
+                    [nameof(LoggingEndpointUrl)]);
+            }
+
+            if (TracingEndpointUrl?.IsAbsoluteUri != true)
+            {
+                yield return new ValidationResult(
+                    $"{nameof(TelemetryOptions)}.{nameof(TracingEndpointUrl)} is must be an absolute URI.",
+                    [nameof(TracingEndpointUrl)]);
+            }
+        }
+    }
+}

tests/DiscordTranslationBot.Tests.Unit/Telemetry/TelemetryOptionsTests.cs

@@ -0,0 +1,68 @@
+using DiscordTranslationBot.Extensions;
+using DiscordTranslationBot.Telemetry;
+
+namespace DiscordTranslationBot.Tests.Unit.Telemetry;
+
+public sealed class TelemetryOptionsTests
+{
+    [Theory]
+    [InlineData(false)]
+    [InlineData(true)]
+    public void Valid_Options_ValidatesWithoutErrors(bool enabled)
+    {
+        // Arrange
+        var options = enabled
+            ? new TelemetryOptions
+            {
+                Enabled = true,
+                ApiKey = "apikey",
+                LoggingEndpointUrl = new Uri("http://localhost:1234"),
+                TracingEndpointUrl = new Uri("http://localhost:1234")
+            }
+            : new TelemetryOptions();
+
+        // Act
+        var isValid = options.TryValidate(out var validationResults);
+
+        // Assert
+        isValid.Should().BeTrue();
+        validationResults.Should().BeEmpty();
+    }
+
+    [Theory]
+    [InlineData(null)]
+    [InlineData("")]
+    [InlineData(" ")]
+    public void Invalid_Options_HasValidationErrors(string? stringValue)
+    {
+        // Arrange
+        var options = new TelemetryOptions
+        {
+            Enabled = true,
+            ApiKey = stringValue,
+            LoggingEndpointUrl = null,
+            TracingEndpointUrl = null
+        };
+
+        // Act
+        var isValid = options.TryValidate(out var validationResults);
+
+        // Assert
+        isValid.Should().BeFalse();
+
+        validationResults
+            .Should()
+            .HaveCount(3)
+            .And
+            .ContainSingle(
+                x => x.ErrorMessage!.Contains($"{nameof(TelemetryOptions)}.{nameof(TelemetryOptions.ApiKey)}"))
+            .And
+            .ContainSingle(
+                x => x.ErrorMessage!.Contains(
+                    $"{nameof(TelemetryOptions)}.{nameof(TelemetryOptions.LoggingEndpointUrl)}"))
+            .And
+            .ContainSingle(
+                x => x.ErrorMessage!.Contains(
+                    $"{nameof(TelemetryOptions)}.{nameof(TelemetryOptions.TracingEndpointUrl)}"));
+    }
+}