Set ConnectionState to Broken. Fixes #1599

When a socket/network error occurs, mark the connection as 'Broken', not 'Closed'. The user must explicitly Close the MySqlConnection (which will return it to the pool) before re-Opening it.

Author: bgrainger

src/MySqlConnector/Core/ServerSession.cs

@@ -2010,7 +2010,7 @@ internal void SetFailed(Exception exception)
 		lock (m_lock)
 			m_state = State.Failed;
 		if (OwningConnection is not null && OwningConnection.TryGetTarget(out var connection))
-			connection.SetState(ConnectionState.Closed);
+			connection.SetState(ConnectionState.Broken);
 	}
 
 	private void VerifyState(State state)

src/MySqlConnector/MySqlConnection.cs

@@ -510,7 +510,7 @@ private async ValueTask<bool> PingAsync(IOBehavior ioBehavior, CancellationToken
 		{
 		}
 
-		SetState(ConnectionState.Closed);
+		SetState(ConnectionState.Broken);
 		return false;
 	}
 

tests/MySqlConnector.Tests/ConnectionTests.cs

@@ -277,6 +277,72 @@ public void ReplaceActiveReader()
 		connection.Close();
 	}
 
+	[Fact]
+	public async Task KillServerConnectionWhileOpen()
+	{
+		var csb = new MySqlConnectionStringBuilder(m_csb.ConnectionString)
+		{
+			MaximumPoolSize = 5,
+			ConnectionTimeout = 5,
+		};
+
+		List<Task> tasks = [];
+		using var barrier = new Barrier((int) csb.MaximumPoolSize);
+		for (var i = 0; i < csb.MaximumPoolSize - 1; i++)
+		{
+			var threadId = i;
+			tasks.Add(Task.Run(async () =>
+			{
+				using var connection = new MySqlConnection(csb.ConnectionString);
+				await connection.OpenAsync().ConfigureAwait(false);
+
+				barrier.SignalAndWait();
+				//// wait for reset
+				barrier.SignalAndWait();
+
+				switch (threadId % 3)
+				{
+					case 0:
+					{
+						using (var command = connection.CreateCommand())
+						{
+							command.CommandText = "SELECT 1;";
+							var exception = Assert.Throws<MySqlException>(() => command.ExecuteScalar());
+							Assert.Equal("Failed to read the result set.", exception.Message);
+						}
+						break;
+					}
+					case 1:
+					{
+						var ping = await connection.PingAsync().ConfigureAwait(false);
+						Assert.False(ping);
+						break;
+					}
+					case 2:
+					{
+						await Assert.ThrowsAnyAsync<Exception>(async () => await connection.ResetConnectionAsync().ConfigureAwait(false));
+						break;
+					}
+				}
+
+				Assert.Equal(ConnectionState.Broken, connection.State);
+
+				await connection.CloseAsync().ConfigureAwait(false);
+				Assert.Equal(ConnectionState.Closed, connection.State);
+
+				var stopwatch = Stopwatch.StartNew();
+				await connection.OpenAsync().ConfigureAwait(false);
+				Assert.InRange(stopwatch.ElapsedMilliseconds, 0, 1000);
+			}));
+		}
+
+		barrier.SignalAndWait();
+		m_server.Reset();
+		barrier.SignalAndWait();
+
+		await Task.WhenAll(tasks);
+	}
+
 	private static async Task WaitForConditionAsync<T>(T expected, Func<T> getValue)
 	{
 		var sw = Stopwatch.StartNew();

tests/MySqlConnector.Tests/FakeMySqlServer.cs

@@ -21,6 +21,22 @@ public void Start()
 		m_tasks.Add(AcceptConnectionsAsync());
 	}
 
+	public void Reset()
+	{
+		m_cts.Cancel();
+		try
+		{
+			Task.WaitAll(m_tasks.Skip(1).ToArray());
+		}
+		catch (AggregateException)
+		{
+		}
+		m_connections.Clear();
+		m_tasks.Clear();
+		m_cts.Dispose();
+		m_cts = new();
+	}
+
 	public void Stop()
 	{
 		if (m_cts is not null)