fixes

Author: KirillKurdyukov

src/Ydb.Sdk/src/Ado/YdbConnection.cs

@@ -100,6 +100,12 @@ public override async Task OpenAsync(CancellationToken cancellationToken)
         {
             throw e switch
             {
+                Driver.TransportException { Status.StatusCode: StatusCode.Cancelled } or OperationCanceledException =>
+                    throw new YdbException(
+                        $"The connection pool has been exhausted, either raise 'MaxSessionPool' " +
+                        $"(currently {ConnectionStringBuilder.MaxSessionPool}) or 'CreateSessionTimeout' " +
+                        $"(currently {ConnectionStringBuilder.CreateSessionTimeout} seconds) in your connection string."
+                    ),
                 Driver.TransportException transportException => new YdbException(transportException),
                 StatusUnsuccessfulException unsuccessfulException => new YdbException(unsuccessfulException.Status),
                 _ => e

src/Ydb.Sdk/src/Pool/SessionPool.cs

@@ -42,40 +42,29 @@ internal async Task<TSession> GetSession(CancellationToken cancellationToken = d
             throw new YdbException("Session pool is closed");
         }
 
-        try
-        {
-            await _semaphore.WaitAsync(finalCancellationToken);
-            Interlocked.Decrement(ref _waitingCount);
-
-            if (_idleSessions.TryDequeue(out var session) && session.IsActive)
-            {
-                return session;
-            }
+        await _semaphore.WaitAsync(finalCancellationToken);
+        Interlocked.Decrement(ref _waitingCount);
 
-            if (session != null) // not active
-            {
-                Logger.LogDebug("Session[{Id}] isn't active, creating new session", session.SessionId);
-            }
+        if (_idleSessions.TryDequeue(out var session) && session.IsActive)
+        {
+            return session;
+        }
 
-            try
-            {
-                return await CreateSession(finalCancellationToken);
-            }
-            catch (Exception e)
-            {
-                Release();
+        if (session != null) // not active
+        {
+            Logger.LogDebug("Session[{Id}] isn't active, creating new session", session.SessionId);
+        }
 
-                Logger.LogError(e, "Failed to create a session");
-                throw;
-            }
+        try
+        {
+            return await CreateSession(finalCancellationToken);
         }
-        catch (Exception e) when (
-            e is Driver.TransportException { Status.StatusCode: StatusCode.Cancelled } or OperationCanceledException
-        )
+        catch (Exception e)
         {
-            throw new YdbException($"The connection pool has been exhausted, either raise 'MaxSessionPool' " +
-                                   $"(currently {_size}) or 'CreateSessionTimeout' " +
-                                   $"(currently {_createSessionTimeoutMs / 1000} seconds) in your connection string.");
+            Release();
+
+            Logger.LogError(e, "Failed to create a session");
+            throw;
         }
     }
 

src/Ydb.Sdk/tests/Ado/YdbConnectionTests.cs

@@ -212,6 +212,18 @@ public async Task DisableDiscovery_WhenPropertyIsTrue_SimpleWorking()
         await YdbConnection.ClearPool(connection);
     }
 
+    [Fact]
+    public async Task OpenAsync_WhenCancelTokenIsCanceled_ThrowYdbException()
+    {
+        await using var connection = CreateConnection();
+        connection.ConnectionString = ConnectionString;
+        using var cts = new CancellationTokenSource();
+        cts.Cancel();
+        Assert.Equal("The connection pool has been exhausted, either raise 'MaxSessionPool' (currently 10) " +
+                     "or 'CreateSessionTimeout' (currently 5 seconds) in your connection string.",
+            (await Assert.ThrowsAsync<YdbException>(async () => await connection.OpenAsync(cts.Token))).Message);
+    }
+
     private List<Task> GenerateTasks() => Enumerable.Range(0, 100).Select(async i =>
     {
         await using var connection = await CreateOpenConnectionAsync();