Add options to configure tracing

src/MySqlConnector/Core/ResultSet.cs

@@ -166,7 +166,7 @@ public async Task ReadResultSetHeaderAsync(IOBehavior ioBehavior)
 						ContainsCommandParameters = true;
 					WarningCount = 0;
 					State = ResultSetState.ReadResultSetHeader;
-					if (DataReader.Activity is { IsAllDataRequested: true })
+					if (DataReader.Activity is { IsAllDataRequested: true } && (Command?.Connection!.MySqlDataSource?.TracingOptions.EnableResultSetHeaderEvent ?? MySqlConnectorTracingOptions.Default.EnableResultSetHeaderEvent))
 						DataReader.Activity.AddEvent(new ActivityEvent("read-result-set-header"));
 					break;
 				}

src/MySqlConnector/MySqlConnection.cs

@@ -1138,6 +1138,8 @@ private async ValueTask<ServerSession> CreateSessionAsync(ConnectionPool? pool,
 
 	internal IPEndPoint? SessionEndPoint => m_session!.IPEndPoint;
 
+	internal MySqlDataSource? MySqlDataSource => m_dataSource;
+
 	internal void SetState(ConnectionState newState)
 	{
 		if (m_connectionState != newState)

src/MySqlConnector/MySqlConnectorTracingOptions.cs

@@ -0,0 +1,11 @@
+namespace MySqlConnector;
+
+internal sealed class MySqlConnectorTracingOptions
+{
+	public bool EnableResultSetHeaderEvent { get; set; }
+
+	public static MySqlConnectorTracingOptions Default { get; } = new()
+	{
+		EnableResultSetHeaderEvent = true,
+	};
+}

src/MySqlConnector/MySqlConnectorTracingOptionsBuilder.cs

@@ -0,0 +1,22 @@
+namespace MySqlConnector;
+
+public sealed class MySqlConnectorTracingOptionsBuilder
+{
+	/// <summary>
+	/// Gets or sets a value indicating whether to enable the "time-to-first-read" event.
+	/// Default is true to preserve existing behavior.
+	/// </summary>
+	public MySqlConnectorTracingOptionsBuilder EnableResultSetHeaderEvent(bool enable = true)
+	{
+		m_enableResultSetHeaderEvent = enable;
+		return this;
+	}
+
+	internal MySqlConnectorTracingOptions Build() =>
+		new()
+		{
+			EnableResultSetHeaderEvent = m_enableResultSetHeaderEvent,
+		};
+
+	private bool m_enableResultSetHeaderEvent = MySqlConnectorTracingOptions.Default.EnableResultSetHeaderEvent;
+}

src/MySqlConnector/MySqlDataSource.cs

@@ -19,12 +19,13 @@ public sealed class MySqlDataSource : DbDataSource
 	/// <param name="connectionString">The connection string for the MySQL Server. This parameter is required.</param>
 	/// <exception cref="ArgumentNullException">Thrown if <paramref name="connectionString"/> is <c>null</c>.</exception>
 	public MySqlDataSource(string connectionString)
-		: this(connectionString ?? throw new ArgumentNullException(nameof(connectionString)), MySqlConnectorLoggingConfiguration.NullConfiguration, null, null, null, null, default, default, default, default)
+		: this(connectionString ?? throw new ArgumentNullException(nameof(connectionString)), MySqlConnectorLoggingConfiguration.NullConfiguration, null, null, null, null, null, default, default, default, default)
 	{
 	}
 
 	internal MySqlDataSource(string connectionString,
 		MySqlConnectorLoggingConfiguration loggingConfiguration,
+		MySqlConnectorTracingOptions? tracingOptions,
 		string? name,
 		Func<X509CertificateCollection, ValueTask>? clientCertificatesCallback,
 		RemoteCertificateValidationCallback? remoteCertificateValidationCallback,
@@ -36,6 +37,7 @@ internal MySqlDataSource(string connectionString,
 	{
 		m_connectionString = connectionString;
 		LoggingConfiguration = loggingConfiguration;
+		TracingOptions = tracingOptions ?? MySqlConnectorTracingOptions.Default;
 		Name = name;
 		m_clientCertificatesCallback = clientCertificatesCallback;
 		m_remoteCertificateValidationCallback = remoteCertificateValidationCallback;
@@ -202,6 +204,8 @@ private async Task RefreshPassword()
 
 	internal MySqlConnectorLoggingConfiguration LoggingConfiguration { get; }
 
+	internal MySqlConnectorTracingOptions TracingOptions { get; }
+
 	internal string? Name { get; }
 
 	private string ProvidePasswordFromField(MySqlProvidePasswordContext context) => m_password!;

src/MySqlConnector/MySqlDataSourceBuilder.cs

@@ -21,6 +21,23 @@ public MySqlDataSourceBuilder(string? connectionString = null)
 		ConnectionStringBuilder = new(connectionString ?? "");
 	}
 
+	/// <summary>
+	/// Configures OpenTelemetry tracing options.
+	/// </summary>
+	/// <returns>This builder, so that method calls can be chained.</returns>
+	public MySqlDataSourceBuilder ConfigureTracing(Action<MySqlConnectorTracingOptionsBuilder> configureAction)
+	{
+#if NET6_0_OR_GREATER
+		ArgumentNullException.ThrowIfNull(configureAction);
+#else
+		if (configureAction is null)
+			throw new ArgumentNullException(nameof(configureAction));
+#endif
+		m_tracingOptionsBuilderCallbacks ??= [];
+		m_tracingOptionsBuilderCallbacks.Add(configureAction);
+		return this;
+	}
+
 	/// <summary>
 	/// Sets the <see cref="ILoggerFactory"/> that will be used for logging.
 	/// </summary>
@@ -107,8 +124,15 @@ public MySqlDataSourceBuilder UseConnectionOpenedCallback(MySqlConnectionOpenedC
 	public MySqlDataSource Build()
 	{
 		var loggingConfiguration = m_loggerFactory is null ? MySqlConnectorLoggingConfiguration.NullConfiguration : new(m_loggerFactory);
+
+		var tracingOptionsBuilder = new MySqlConnectorTracingOptionsBuilder();
+		foreach (var callback in m_tracingOptionsBuilderCallbacks ?? (IEnumerable<Action<MySqlConnectorTracingOptionsBuilder>>) [])
+			callback.Invoke(tracingOptionsBuilder);
+		var tracingOptions = tracingOptionsBuilder.Build();
+
 		return new(ConnectionStringBuilder.ConnectionString,
 			loggingConfiguration,
+			tracingOptions,
 			m_name,
 			m_clientCertificatesCallback,
 			m_remoteCertificateValidationCallback,
@@ -135,4 +159,5 @@ public MySqlDataSource Build()
 	private TimeSpan m_periodicPasswordProviderSuccessRefreshInterval;
 	private TimeSpan m_periodicPasswordProviderFailureRefreshInterval;
 	private MySqlConnectionOpenedCallback? m_connectionOpenedCallback;
+	private List<Action<MySqlConnectorTracingOptionsBuilder>>? m_tracingOptionsBuilderCallbacks;
 }

tests/IntegrationTests/ActivityTests.cs

@@ -140,6 +140,48 @@ public void SelectTags()
 		AssertTag(activity.Tags, "db.statement", "SELECT 1;");
 	}
 
+	[Theory]
+	[InlineData(true)]
+	[InlineData(false)]
+	public void ReadResultSetHeaderEvent(bool enableEvent)
+	{
+		var dataSourceBuilder = new MySqlDataSourceBuilder(AppConfig.ConnectionString)
+			.ConfigureTracing(o => o.EnableResultSetHeaderEvent(enableEvent));
+		using var dataSource = dataSourceBuilder.Build();
+		using var connection = dataSource.OpenConnection();
+
+		using var parentActivity = new Activity(nameof(ReadResultSetHeaderEvent));
+		parentActivity.Start();
+
+		Activity activity = null;
+		using var listener = new ActivityListener
+		{
+			ShouldListenTo = x => x.Name == "MySqlConnector",
+			Sample = (ref ActivityCreationOptions<ActivityContext> options) =>
+				options.TraceId == parentActivity.TraceId ? ActivitySamplingResult.AllData : ActivitySamplingResult.None,
+			ActivityStopped = x => activity = x,
+		};
+		ActivitySource.AddActivityListener(listener);
+
+		using (var command = new MySqlCommand("SELECT 1;", connection))
+		{
+			command.ExecuteScalar();
+		}
+
+		Assert.NotNull(activity);
+		Assert.Equal(ActivityKind.Client, activity.Kind);
+		Assert.Equal("Execute", activity.OperationName);
+		if (enableEvent)
+		{
+			var activityEvent = Assert.Single(activity.Events);
+			Assert.Equal("read-result-set-header", activityEvent.Name);
+		}
+		else
+		{
+			Assert.Empty(activity.Events);
+		}
+	}
+
 	private void AssertTags(IEnumerable<KeyValuePair<string, string>> tags, MySqlConnectionStringBuilder csb)
 	{
 		AssertTag(tags, "db.system", "mysql");