Unify Application Name and UseName. Fixes #1434

docs/content/connection-options.md

@@ -286,8 +286,13 @@ These are the other options that MySqlConnector supports. They are set to sensib
   <tr id="ApplicationName">
     <td>Application Name, ApplicationName</td>
     <td>null</td>
-    <td>Sets the <c>program_name</c> connection attribute passed to MySQL Server. This value may be displayed by diagnostic tools,
-    e.g., as the “Program” column in “Client Connections” in <a href="https://www.mysql.com/products/workbench/">MySQL Workbench</a>.</td>
+    <td><p>Sets the <c>program_name</c> connection attribute passed to MySQL Server. This value may be displayed by diagnostic tools,
+    e.g., as the “Program” column in “Client Connections” in <a href="https://www.mysql.com/products/workbench/">MySQL Workbench</a>.
+    It also sets the connection pool name reported by the <code>pool.name</code> tag associated with connection pool metrics.</p>
+    <p>This connection string option is deprecated and is provided for backwards compatibility. Newer applications should
+    use <a href="/api/MySqlConnector/MySqlDataSourceBuilder/UseName/"><code>MySqlDataSourceBuilder.UseName</code></a> instead.
+    </p></td>
+    </td>
   </tr>
   <tr id="AutoEnlist">
     <td>Auto Enlist, AutoEnlist</td>

docs/content/diagnostics/metrics.md

@@ -41,3 +41,55 @@ Name | Type | Unit | Description
 `db.client.connections.idle.max` | UpDownCounter | `{connection}` | The maximum number of idle open connections allowed; this corresponds to `MaximumPoolSize` in the connection string.
 `db.client.connections.idle.min` | UpDownCounter | `{connection}` | The minimum number of idle open connections allowed; this corresponds to `MinimumPoolSize` in the connection string.
 `db.client.connections.max` | UpDownCounter | `{connection}` | The maximum number of open connections allowed; this corresponds to `MaximumPoolSize` in the connection string.
+
+## Supported Tags
+
+Name | Description
+--- | ---
+`pool.name` | The name of the connection pool (see below).
+`state` | `idle` or `used`; this tag is used with the `db.client.connections.usage` instrument.
+
+## Connection Pool Name
+
+A connection pool name can be specified by one of the following means:
+
+### UseName
+
+The `MySqlDataSourceBuilder.UseName` method can be used to specify a name for the connection pool:
+
+```csharp
+using var dataSource = new MySqlDataSourceBuilder("...connection string...")
+    .UseName("MyPoolName")
+    .Build();
+```
+
+This can also be used with dependency injection:
+
+```csharp
+builder.Services.AddMySqlDataSource(builder.Configuration.GetConnectionString("Default"),
+    x => x.UseName("MyPoolName"));
+```
+
+### Keyed Services
+
+Use the `AddKeyedMySqlDataSource` method to register a `MySqlDataSource` as a [keyed service](https://learn.microsoft.com/en-us/dotnet/core/whats-new/dotnet-8#keyed-di-services).
+If the service key is a string, it will automatically be used as the `MySqlDataSource` name.
+
+```csharp
+builder.Services.AddKeyedMySqlDataSource("MyPoolName",
+    builder.Configuration.GetConnectionString("MyConnectionString"));
+```
+
+### Application Name
+
+Finally, the connection pool name can be specified by setting the `Application Name` connection string option:
+
+```csharp
+using var connection = new MySqlConnection("server=dbserver;...;Application Name=MyPoolName");
+```
+
+If `UseName` is used, it will override the `Application Name` connection string option.
+
+### Default
+
+For metrics, if no pool name is specified, the connection string (without a password) will be used as the pool name.

src/MySqlConnector/Core/ConnectionPool.cs

@@ -501,9 +501,12 @@ private async ValueTask<ServerSession> ConnectSessionAsync(MySqlConnection conne
 		if (!connectionStringBuilder.Pooling)
 			return null;
 
+		if (name is not null)
+			connectionStringBuilder.ApplicationName = name;
+
 		// force a new pool to be created, ignoring the cache
 		var connectionSettings = new ConnectionSettings(connectionStringBuilder);
-		var pool = new ConnectionPool(loggingConfiguration, connectionSettings, name);
+		var pool = new ConnectionPool(loggingConfiguration, connectionSettings);
 		pool.StartReaperTask();
 		pool.StartDnsCheckTimer();
 		return pool;
@@ -551,7 +554,7 @@ private async ValueTask<ServerSession> ConnectSessionAsync(MySqlConnection conne
 
 		// create a new pool and attempt to insert it; if someone else beats us to it, just use their value
 		var connectionSettings = new ConnectionSettings(connectionStringBuilder);
-		var newPool = new ConnectionPool(loggingConfiguration!, connectionSettings, name: null);
+		var newPool = new ConnectionPool(loggingConfiguration!, connectionSettings);
 		pool = s_pools.GetOrAdd(normalizedConnectionString, newPool);
 
 		if (pool == newPool)
@@ -591,12 +594,12 @@ static List<ConnectionPool> GetCachedPools()
 		}
 	}
 
-	private ConnectionPool(MySqlConnectorLoggingConfiguration loggingConfiguration, ConnectionSettings cs, string? name)
+	private ConnectionPool(MySqlConnectorLoggingConfiguration loggingConfiguration, ConnectionSettings cs)
 	{
 		m_logger = loggingConfiguration.PoolLogger;
 		m_connectionLogger = loggingConfiguration.ConnectionLogger;
 		ConnectionSettings = cs;
-		Name = name;
+		Name = cs.ApplicationName;
 		SslProtocols = cs.TlsVersions;
 		m_generation = 0;
 		m_cleanSemaphore = new(1);

src/MySqlConnector/Core/ConnectionSettings.cs

@@ -121,7 +121,7 @@ public ConnectionSettings(MySqlConnectionStringBuilder csb)
 		AllowPublicKeyRetrieval = csb.AllowPublicKeyRetrieval;
 		AllowUserVariables = csb.AllowUserVariables;
 		AllowZeroDateTime = csb.AllowZeroDateTime;
-		ApplicationName = csb.ApplicationName;
+		ApplicationName = csb.ApplicationName is { Length: 0 } ? null : csb.ApplicationName;
 		AutoEnlist = csb.AutoEnlist;
 		CancellationTimeout = csb.CancellationTimeout;
 		ConnectionTimeout = ToSigned(csb.ConnectionTimeout);
@@ -216,7 +216,7 @@ private static MySqlGuidFormat GetEffectiveGuidFormat(MySqlGuidFormat guidFormat
 	public bool AllowPublicKeyRetrieval { get; }
 	public bool AllowUserVariables { get; }
 	public bool AllowZeroDateTime { get; }
-	public string ApplicationName { get; }
+	public string? ApplicationName { get; }
 	public bool AutoEnlist { get; }
 	public int CancellationTimeout { get; }
 	public int ConnectionTimeout { get; }

src/MySqlConnector/Core/MetricsReporter.cs

@@ -9,7 +9,7 @@ internal static class MetricsReporter
 	public static void RemoveIdle(ConnectionPool pool) => s_connectionsUsageCounter.Add(-1, pool.IdleStateTagList);
 	public static void AddUsed(ConnectionPool pool) => s_connectionsUsageCounter.Add(1, pool.UsedStateTagList);
 	public static void RemoveUsed(ConnectionPool pool) => s_connectionsUsageCounter.Add(-1, pool.UsedStateTagList);
-	public static void AddTimeout(ConnectionPool? pool, ConnectionSettings connectionSettings) => s_connectionTimeouts.Add(1, new KeyValuePair<string, object?>("pool.name", pool?.Name ?? connectionSettings.ConnectionStringBuilder.GetConnectionString(includePassword: false)));
+	public static void AddTimeout(ConnectionPool? pool, ConnectionSettings connectionSettings) => s_connectionTimeouts.Add(1, new KeyValuePair<string, object?>("pool.name", pool?.Name ?? connectionSettings.ApplicationName ?? connectionSettings.ConnectionStringBuilder.GetConnectionString(includePassword: false)));
 	public static void RecordCreateTime(ConnectionPool pool, double seconds) => s_createTimeHistory.Record(seconds, pool.PoolNameTagList);
 	public static void RecordUseTime(ConnectionPool pool, double seconds) => s_useTimeHistory.Record(seconds, pool.PoolNameTagList);
 	public static void RecordWaitTime(ConnectionPool pool, double seconds) => s_waitTimeHistory.Record(seconds, pool.PoolNameTagList);

src/MySqlConnector/Core/ServerSession.cs

@@ -1777,7 +1777,7 @@ private void VerifyState(State state1, State state2, State state3, State state4,
 
 	internal SslProtocols SslProtocol => m_sslStream?.SslProtocol ?? SslProtocols.None;
 
-	private byte[] CreateConnectionAttributes(string programName)
+	private byte[] CreateConnectionAttributes(string? programName)
 	{
 		Log.CreatingConnectionAttributes(m_logger, Id);
 		var attributesWriter = new ByteBufferWriter();
@@ -1815,7 +1815,7 @@ private byte[] CreateConnectionAttributes(string programName)
 #endif
 		attributesWriter.WriteLengthEncodedString("_pid");
 		attributesWriter.WriteLengthEncodedString(processId.ToString(CultureInfo.InvariantCulture));
-		if (programName.Length != 0)
+		if (!string.IsNullOrEmpty(programName))
 		{
 			attributesWriter.WriteLengthEncodedString("program_name");
 			attributesWriter.WriteLengthEncodedString(programName!);

src/MySqlConnector/MySqlDataSourceBuilder.cs

@@ -36,6 +36,9 @@ public MySqlDataSourceBuilder UseLoggerFactory(ILoggerFactory? loggerFactory)
 	/// </summary>
 	/// <param name="name">The data source name.</param>
 	/// <returns>This builder, so that method calls can be chained.</returns>
+	/// <remarks>The connection pool name is used to set the <c>program_name</c> connection attribute
+	/// (which is visible to some diagnostic tools) and the <c>pool.name</c> tag supplied with
+	/// <a href="https://mysqlconnector.net/diagnostics/metrics/">connection pool metrics</a>.</remarks>
 	public MySqlDataSourceBuilder UseName(string? name)
 	{
 		m_name = name;

tests/MySqlConnector.Tests/Metrics/IConnectionCreator.cs

@@ -17,7 +17,7 @@ public DataSourceConnectionCreator(bool usePooling, string? poolName, string? ap
 		m_dataSource = new MySqlDataSourceBuilder(connectionStringBuilder.ConnectionString)
 			.UseName(poolName)
 			.Build();
-        PoolName = poolName ?? connectionStringBuilder!.GetConnectionString(includePassword: false);
+        PoolName = poolName ?? applicationName ?? connectionStringBuilder!.GetConnectionString(includePassword: false);
     }
 
     public MySqlConnection OpenConnection() => m_dataSource!.OpenConnection();
@@ -34,7 +34,7 @@ public PlainConnectionCreator(bool usePooling, string? applicationName, MySqlCon
 		connectionStringBuilder.Pooling = usePooling;
 		connectionStringBuilder.ApplicationName = applicationName;
 		m_connectionString = connectionStringBuilder.ConnectionString;
-		PoolName = connectionStringBuilder.GetConnectionString(includePassword: false);
+		PoolName = applicationName ?? connectionStringBuilder.GetConnectionString(includePassword: false);
     }
 
 	public MySqlConnection OpenConnection()