Description:
If multiple MySqlConnection objects are opened at the same time (on different threads), the application may crash with an ArgumentException or InvalidOperationException when MySqlPoolManager.GetPoolAsync tries to modify the shared 'Pools' object concurrently from different threads.
Example exceptions:
❯ dotnet run
Unhandled exception. System.AggregateException: One or more errors occurred. (An item with the same key has already been added. Key: server=localhost;user id=root;password=pass) (Operations that change non-concurrent collections must have exclusive access. A concurrent update was performed on this collection and corrupted its state. The collection's state is no longer correct.) (Operations that change non-concurrent collections must have exclusive access. A concurrent update was performed on this collection and corrupted its state. The collection's state is no longer correct.) (Operations that change non-concurrent collections must have exclusive access. A concurrent update was performed on this collection and corrupted its state. The collection's state is no longer correct.)
---> System.ArgumentException: An item with the same key has already been added. Key: server=localhost;user id=root;password=pass
at System.Collections.Generic.Dictionary`2.TryInsert(TKey key, TValue value, InsertionBehavior behavior)
at System.Collections.Generic.Dictionary`2.Add(TKey key, TValue value)
at MySql.Data.MySqlClient.MySqlPoolManager.GetPoolAsync(MySqlConnectionStringBuilder settings, Boolean execAsync, CancellationToken cancellationToken)
at MySql.Data.MySqlClient.MySqlConnection.OpenAsync(Boolean execAsync, CancellationToken cancellationToken)
at MySql.Data.MySqlClient.MySqlConnection.Open()
at z.Program.<>c__DisplayClass1_0.<Main>b__0() in C:\Test\Program.cs:line 43
at System.Threading.ExecutionContext.RunFromThreadPoolDispatchLoop(Thread threadPoolThread, ExecutionContext executionContext, ContextCallback callback, Object state)
--- End of stack trace from previous location ---
at System.Threading.ExecutionContext.RunFromThreadPoolDispatchLoop(Thread threadPoolThread, ExecutionContext executionContext, ContextCallback callback, Object state)
at System.Threading.Tasks.Task.ExecuteWithThreadLocal(Task& currentTaskSlot, Thread threadPoolThread)
--- End of inner exception stack trace ---
at System.Threading.Tasks.Task.WaitAllCore(Task[] tasks, Int32 millisecondsTimeout, CancellationToken cancellationToken)
at System.Threading.Tasks.Task.WaitAll(Task[] tasks)
at z.Program.Main(String[] args) in C:\Test\Program.cs:line 47
---> (Inner Exception #1) System.InvalidOperationException: Operations that change non-concurrent collections must have exclusive access. A concurrent update was performed on this collection and corrupted its state. The collection's state is no longer correct.
at System.Collections.Generic.Dictionary`2.TryInsert(TKey key, TValue value, InsertionBehavior behavior)
at System.Collections.Generic.Dictionary`2.Add(TKey key, TValue value)
at MySql.Data.MySqlClient.MySqlPoolManager.GetPoolAsync(MySqlConnectionStringBuilder settings, Boolean execAsync, CancellationToken cancellationToken)
at MySql.Data.MySqlClient.MySqlConnection.OpenAsync(Boolean execAsync, CancellationToken cancellationToken)
at MySql.Data.MySqlClient.MySqlConnection.Open()
at z.Program.<>c__DisplayClass1_0.<Main>b__0() in C:\Test\Program.cs:line 43
at System.Threading.ExecutionContext.RunFromThreadPoolDispatchLoop(Thread threadPoolThread, ExecutionContext executionContext, ContextCallback callback, Object state)
--- End of stack trace from previous location ---
at System.Threading.ExecutionContext.RunFromThreadPoolDispatchLoop(Thread threadPoolThread, ExecutionContext executionContext, ContextCallback callback, Object state)
at System.Threading.Tasks.Task.ExecuteWithThreadLocal(Task& currentTaskSlot, Thread threadPoolThread)<---
---> (Inner Exception #2) System.InvalidOperationException: Operations that change non-concurrent collections must have exclusive access. A concurrent update was performed on this collection and corrupted its state. The collection's state is no longer correct.
at System.Collections.Generic.Dictionary`2.TryInsert(TKey key, TValue value, InsertionBehavior behavior)
at System.Collections.Generic.Dictionary`2.Add(TKey key, TValue value)
at MySql.Data.MySqlClient.MySqlPoolManager.GetPoolAsync(MySqlConnectionStringBuilder settings, Boolean execAsync, CancellationToken cancellationToken)
at MySql.Data.MySqlClient.MySqlConnection.OpenAsync(Boolean execAsync, CancellationToken cancellationToken)
at MySql.Data.MySqlClient.MySqlConnection.Open()
at z.Program.<>c__DisplayClass1_0.<Main>b__0() in C:\Test\Program.cs:line 43
at System.Threading.ExecutionContext.RunFromThreadPoolDispatchLoop(Thread threadPoolThread, ExecutionContext executionContext, ContextCallback callback, Object state)
--- End of stack trace from previous location ---
at System.Threading.ExecutionContext.RunFromThreadPoolDispatchLoop(Thread threadPoolThread, ExecutionContext executionContext, ContextCallback callback, Object state)
at System.Threading.Tasks.Task.ExecuteWithThreadLocal(Task& currentTaskSlot, Thread threadPoolThread)<---
---> (Inner Exception #3) System.InvalidOperationException: Operations that change non-concurrent collections must have exclusive access. A concurrent update was performed on this collection and corrupted its state. The collection's state is no longer correct.
at System.Collections.Generic.Dictionary`2.TryInsert(TKey key, TValue value, InsertionBehavior behavior)
at System.Collections.Generic.Dictionary`2.Add(TKey key, TValue value)
at MySql.Data.MySqlClient.MySqlPoolManager.GetPoolAsync(MySqlConnectionStringBuilder settings, Boolean execAsync, CancellationToken cancellationToken)
at MySql.Data.MySqlClient.MySqlConnection.OpenAsync(Boolean execAsync, CancellationToken cancellationToken)
at MySql.Data.MySqlClient.MySqlConnection.Open()
at z.Program.<>c__DisplayClass1_0.<Main>b__0() in C:\Test\Program.cs:line 43
at System.Threading.ExecutionContext.RunFromThreadPoolDispatchLoop(Thread threadPoolThread, ExecutionContext executionContext, ContextCallback callback, Object state)
--- End of stack trace from previous location ---
at System.Threading.ExecutionContext.RunFromThreadPoolDispatchLoop(Thread threadPoolThread, ExecutionContext executionContext, ContextCallback callback, Object state)
at System.Threading.Tasks.Task.ExecuteWithThreadLocal(Task& currentTaskSlot, Thread threadPoolThread)<---
How to repeat:
Run the following C# program. (If necessary, increase the number of iterations to trigger the bug.)
var connectionString = "server=localhost;user id=root;password=pass";
var tasks = new List<Task>();
for (int i = 0; i < 5; i++)
{
tasks.Add(Task.Run(() =>
{
using (var connection = new MySqlConnection(connectionString))
{
connection.Open();
}
}));
}
Task.WaitAll(tasks.ToArray());
Suggested fix:
Change GetPoolAsync to use a shared static SemaphoreSlim object (and wait on that), instead of creating a local variable.
Description: If multiple MySqlConnection objects are opened at the same time (on different threads), the application may crash with an ArgumentException or InvalidOperationException when MySqlPoolManager.GetPoolAsync tries to modify the shared 'Pools' object concurrently from different threads. Example exceptions: ❯ dotnet run Unhandled exception. System.AggregateException: One or more errors occurred. (An item with the same key has already been added. Key: server=localhost;user id=root;password=pass) (Operations that change non-concurrent collections must have exclusive access. A concurrent update was performed on this collection and corrupted its state. The collection's state is no longer correct.) (Operations that change non-concurrent collections must have exclusive access. A concurrent update was performed on this collection and corrupted its state. The collection's state is no longer correct.) (Operations that change non-concurrent collections must have exclusive access. A concurrent update was performed on this collection and corrupted its state. The collection's state is no longer correct.) ---> System.ArgumentException: An item with the same key has already been added. Key: server=localhost;user id=root;password=pass at System.Collections.Generic.Dictionary`2.TryInsert(TKey key, TValue value, InsertionBehavior behavior) at System.Collections.Generic.Dictionary`2.Add(TKey key, TValue value) at MySql.Data.MySqlClient.MySqlPoolManager.GetPoolAsync(MySqlConnectionStringBuilder settings, Boolean execAsync, CancellationToken cancellationToken) at MySql.Data.MySqlClient.MySqlConnection.OpenAsync(Boolean execAsync, CancellationToken cancellationToken) at MySql.Data.MySqlClient.MySqlConnection.Open() at z.Program.<>c__DisplayClass1_0.<Main>b__0() in C:\Test\Program.cs:line 43 at System.Threading.ExecutionContext.RunFromThreadPoolDispatchLoop(Thread threadPoolThread, ExecutionContext executionContext, ContextCallback callback, Object state) --- End of stack trace from previous location --- at System.Threading.ExecutionContext.RunFromThreadPoolDispatchLoop(Thread threadPoolThread, ExecutionContext executionContext, ContextCallback callback, Object state) at System.Threading.Tasks.Task.ExecuteWithThreadLocal(Task& currentTaskSlot, Thread threadPoolThread) --- End of inner exception stack trace --- at System.Threading.Tasks.Task.WaitAllCore(Task[] tasks, Int32 millisecondsTimeout, CancellationToken cancellationToken) at System.Threading.Tasks.Task.WaitAll(Task[] tasks) at z.Program.Main(String[] args) in C:\Test\Program.cs:line 47 ---> (Inner Exception #1) System.InvalidOperationException: Operations that change non-concurrent collections must have exclusive access. A concurrent update was performed on this collection and corrupted its state. The collection's state is no longer correct. at System.Collections.Generic.Dictionary`2.TryInsert(TKey key, TValue value, InsertionBehavior behavior) at System.Collections.Generic.Dictionary`2.Add(TKey key, TValue value) at MySql.Data.MySqlClient.MySqlPoolManager.GetPoolAsync(MySqlConnectionStringBuilder settings, Boolean execAsync, CancellationToken cancellationToken) at MySql.Data.MySqlClient.MySqlConnection.OpenAsync(Boolean execAsync, CancellationToken cancellationToken) at MySql.Data.MySqlClient.MySqlConnection.Open() at z.Program.<>c__DisplayClass1_0.<Main>b__0() in C:\Test\Program.cs:line 43 at System.Threading.ExecutionContext.RunFromThreadPoolDispatchLoop(Thread threadPoolThread, ExecutionContext executionContext, ContextCallback callback, Object state) --- End of stack trace from previous location --- at System.Threading.ExecutionContext.RunFromThreadPoolDispatchLoop(Thread threadPoolThread, ExecutionContext executionContext, ContextCallback callback, Object state) at System.Threading.Tasks.Task.ExecuteWithThreadLocal(Task& currentTaskSlot, Thread threadPoolThread)<--- ---> (Inner Exception #2) System.InvalidOperationException: Operations that change non-concurrent collections must have exclusive access. A concurrent update was performed on this collection and corrupted its state. The collection's state is no longer correct. at System.Collections.Generic.Dictionary`2.TryInsert(TKey key, TValue value, InsertionBehavior behavior) at System.Collections.Generic.Dictionary`2.Add(TKey key, TValue value) at MySql.Data.MySqlClient.MySqlPoolManager.GetPoolAsync(MySqlConnectionStringBuilder settings, Boolean execAsync, CancellationToken cancellationToken) at MySql.Data.MySqlClient.MySqlConnection.OpenAsync(Boolean execAsync, CancellationToken cancellationToken) at MySql.Data.MySqlClient.MySqlConnection.Open() at z.Program.<>c__DisplayClass1_0.<Main>b__0() in C:\Test\Program.cs:line 43 at System.Threading.ExecutionContext.RunFromThreadPoolDispatchLoop(Thread threadPoolThread, ExecutionContext executionContext, ContextCallback callback, Object state) --- End of stack trace from previous location --- at System.Threading.ExecutionContext.RunFromThreadPoolDispatchLoop(Thread threadPoolThread, ExecutionContext executionContext, ContextCallback callback, Object state) at System.Threading.Tasks.Task.ExecuteWithThreadLocal(Task& currentTaskSlot, Thread threadPoolThread)<--- ---> (Inner Exception #3) System.InvalidOperationException: Operations that change non-concurrent collections must have exclusive access. A concurrent update was performed on this collection and corrupted its state. The collection's state is no longer correct. at System.Collections.Generic.Dictionary`2.TryInsert(TKey key, TValue value, InsertionBehavior behavior) at System.Collections.Generic.Dictionary`2.Add(TKey key, TValue value) at MySql.Data.MySqlClient.MySqlPoolManager.GetPoolAsync(MySqlConnectionStringBuilder settings, Boolean execAsync, CancellationToken cancellationToken) at MySql.Data.MySqlClient.MySqlConnection.OpenAsync(Boolean execAsync, CancellationToken cancellationToken) at MySql.Data.MySqlClient.MySqlConnection.Open() at z.Program.<>c__DisplayClass1_0.<Main>b__0() in C:\Test\Program.cs:line 43 at System.Threading.ExecutionContext.RunFromThreadPoolDispatchLoop(Thread threadPoolThread, ExecutionContext executionContext, ContextCallback callback, Object state) --- End of stack trace from previous location --- at System.Threading.ExecutionContext.RunFromThreadPoolDispatchLoop(Thread threadPoolThread, ExecutionContext executionContext, ContextCallback callback, Object state) at System.Threading.Tasks.Task.ExecuteWithThreadLocal(Task& currentTaskSlot, Thread threadPoolThread)<--- How to repeat: Run the following C# program. (If necessary, increase the number of iterations to trigger the bug.) var connectionString = "server=localhost;user id=root;password=pass"; var tasks = new List<Task>(); for (int i = 0; i < 5; i++) { tasks.Add(Task.Run(() => { using (var connection = new MySqlConnection(connectionString)) { connection.Open(); } })); } Task.WaitAll(tasks.ToArray()); Suggested fix: Change GetPoolAsync to use a shared static SemaphoreSlim object (and wait on that), instead of creating a local variable.