Add 'db.client.connections.timeouts' counter. Fixes #1392

Author: bgrainger

docs/content/diagnostics/metrics.md

@@ -34,6 +34,7 @@ Name | Type | Unit | Description
 --- | --- | --- | ---
 `db.client.connections.usage` | UpDownCounter | `{connection}` | The number of connections that are currently in the state described by the state tag.
 `db.client.connections.pending_requests` | UpDownCounter | `{request}` | The number of pending requests for an open connection, cumulative for the entire pool.
+`db.client.connections.timeouts` | Counter | `{timeout}` | The number of connection timeouts that have occurred trying to obtain a connection from the pool.
 `db.client.connections.create_time` | Histogram | `s` | The time it took to create a new connection.
 `db.client.connections.use_time` | Histogram | `s` | The time between borrowing a connection and returning it to the pool.
 `db.client.connections.wait_time` | Histogram | `s` | The time it took to obtain an open connection from the pool.

src/MySqlConnector/Core/MetricsReporter.cs

@@ -9,6 +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 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);
@@ -48,6 +49,8 @@ static IEnumerable<Measurement<int>> GetMinimumConnections() =>
 			unit: "{connection}", description: "The number of connections that are currently in the state described by the state tag.");
 	private static readonly UpDownCounter<int> s_pendingRequestsCounter = ActivitySourceHelper.Meter.CreateUpDownCounter<int>("db.client.connections.pending_requests",
 			unit: "{request}", description: "The number of pending requests for an open connection, cumulative for the entire pool.");
+	private static readonly Counter<int> s_connectionTimeouts = ActivitySourceHelper.Meter.CreateCounter<int>("db.client.connections.timeouts",
+            unit: "{timeout}", description: "The number of connection timeouts that have occurred trying to obtain a connection from the pool.");
 	private static readonly Histogram<double> s_createTimeHistory = ActivitySourceHelper.Meter.CreateHistogram<double>("db.client.connections.create_time",
 			unit: "s", description: "The time it took to create a new connection.");
 	private static readonly Histogram<double> s_useTimeHistory = ActivitySourceHelper.Meter.CreateHistogram<double>("db.client.connections.use_time",

src/MySqlConnector/MySqlConnection.cs

@@ -941,13 +941,20 @@ private async ValueTask<ServerSession> CreateSessionAsync(ConnectionPool? pool,
 		}
 		catch (OperationCanceledException) when (timeoutSource?.IsCancellationRequested is true)
 		{
+			MetricsReporter.AddTimeout(pool, connectionSettings);
 			var messageSuffix = (pool?.IsEmpty is true) ? " All pooled connections are in use." : "";
 			throw new MySqlException(MySqlErrorCode.UnableToConnectToHost, "Connect Timeout expired." + messageSuffix);
 		}
 		catch (MySqlException ex) when ((timeoutSource?.IsCancellationRequested is true) || (ex.ErrorCode == MySqlErrorCode.CommandTimeoutExpired))
 		{
+			MetricsReporter.AddTimeout(pool, connectionSettings);
 			throw new MySqlException(MySqlErrorCode.UnableToConnectToHost, "Connect Timeout expired.", ex);
 		}
+		catch (MySqlException ex) when (ex.ErrorCode == MySqlErrorCode.UnableToConnectToHost && ex.Message == "Connect Timeout expired.")
+		{
+			MetricsReporter.AddTimeout(pool, connectionSettings);
+			throw;
+		}
 		finally
 		{
 			MetricsReporter.RemovePendingRequest(pool);

tests/MySqlConnector.Tests/Metrics/ConnectTimeoutTests.cs

@@ -0,0 +1,50 @@
+namespace MySqlConnector.Tests.Metrics;
+
+public class ConnectTimeoutTests : MetricsTestsBase
+{
+	[Fact(Skip = MetricsSkip)]
+	public async Task ConnectTimeout()
+	{
+		var csb = CreateConnectionStringBuilder();
+		csb.ConnectionTimeout = 1;
+		csb.Server = "www.example.com";
+		PoolName = csb.GetConnectionString(includePassword: false);
+
+		using var connection = new MySqlConnection(csb.ConnectionString);
+		await Assert.ThrowsAsync<MySqlException>(connection.OpenAsync);
+
+		AssertMeasurement("db.client.connections.timeouts", 1);
+	}
+
+	[Fact(Skip = MetricsSkip)]
+	public async Task DataSourceConnectTimeout()
+	{
+		var csb = CreateConnectionStringBuilder();
+		csb.ConnectionTimeout = 1;
+		csb.Server = "www.example.com";
+
+		PoolName = "timeout";
+		using var dataSource = new MySqlDataSourceBuilder(csb.ConnectionString)
+			.UseName(PoolName)
+			.Build();
+
+		await Assert.ThrowsAsync<MySqlException>(async () => await dataSource.OpenConnectionAsync());
+
+		AssertMeasurement("db.client.connections.timeouts", 1);
+	}
+
+	[Fact(Skip = MetricsSkip)]
+	public async Task NoPoolConnectTimeout()
+	{
+		var csb = CreateConnectionStringBuilder();
+		csb.ConnectionTimeout = 1;
+		csb.Server = "www.example.com";
+		csb.Pooling = false;
+		PoolName = csb.GetConnectionString(includePassword: false);
+
+		using var connection = new MySqlConnection(csb.ConnectionString);
+		await Assert.ThrowsAsync<MySqlException>(connection.OpenAsync);
+
+		AssertMeasurement("db.client.connections.timeouts", 1);
+	}
+}