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Fix for the race condition being created when two threads were simultaneously doing refresh #8

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Merged
Sfurti-yb merged 2 commits into from
Dec 11, 2025
Merged

Fix for the race condition being created when two threads were simultaneously doing refresh #8

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730bb9e
Set up a lock before refresh mechanism
Sfurti-yb Nov 25, 2025
8a0cb72
Optimised the code changes
Sfurti-yb Dec 4, 2025
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58 changes: 28 additions & 30 deletions src/Npgsql/NpgsqlConnection.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -168,24 +168,25 @@ internal static NpgsqlConnection FromDataSource(NpgsqlDataSource dataSource)
/// <returns>A task representing the asynchronous operation.</returns>
public override Task OpenAsync(CancellationToken cancellationToken) => Open(async: true, cancellationToken);

static readonly object SetupDataSourceLock = new();
void SetupDataSource()
{
// Fast path: a pool already corresponds to this exact version of the connection string.
if (PoolManager.Pools.TryGetValue(_connectionString, out _dataSource) && !_dataSource.NeedsRefresh())
{
Settings = _dataSource.Settings; // Great, we already have a pool
return;
}

// A pool already corresponds to this version of string but also needs Refresh

if (PoolManager.Pools.TryGetValue(_connectionString, out _dataSource) && _dataSource.NeedsRefresh())
lock (SetupDataSourceLock)
{
_dataSource.Refresh();
Settings = _dataSource.Settings; // Great, we already have a pool
return;
if (PoolManager.Pools.TryGetValue(_connectionString, out _dataSource))
{
if (_dataSource.NeedsRefresh())
{
_dataSource.Refresh();
}
Settings = _dataSource.Settings; // Great, we already have a pool
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return;
}
}


// Connection string hasn't been seen before. Check for empty and parse (slow one-time path).
if (_connectionString == string.Empty)
{
Expand All @@ -204,26 +205,23 @@ void SetupDataSource()
// Note that we remove TargetSessionAttributes to make all connection strings that are otherwise identical point to the same pool.
var canonical = settings.ConnectionStringForMultipleHosts;

if (PoolManager.Pools.TryGetValue(canonical, out _dataSource) && !_dataSource.NeedsRefresh())
lock (SetupDataSourceLock)
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{
// If this is a multi-host data source and the user specified a TargetSessionAttributes, create a wrapper in front of the
// MultiHostDataSource with that TargetSessionAttributes.
if (_dataSource is NpgsqlMultiHostDataSource multiHostDataSource && settings.TargetSessionAttributesParsed.HasValue)
_dataSource = multiHostDataSource.WithTargetSession(settings.TargetSessionAttributesParsed.Value);

// The pool was found, but only under the canonical key - we're using a different version
// for the first time. Map it via our own key for next time.
_dataSource = PoolManager.Pools.GetOrAdd(_connectionString, _dataSource);
return;
}

if (PoolManager.Pools.TryGetValue(canonical, out _dataSource) && _dataSource.NeedsRefresh())
{
_dataSource.Refresh();
// The pool was found, but only under the canonical key - we're using a different version
// for the first time. Map it via our own key for next time.
_dataSource = PoolManager.Pools.GetOrAdd(_connectionString, _dataSource);
return;
if (PoolManager.Pools.TryGetValue(canonical, out _dataSource))
{
if (_dataSource.NeedsRefresh())
{
_dataSource.Refresh();
}
// If this is a multi-host data source and the user specified a TargetSessionAttributes, create a wrapper in front of the
// MultiHostDataSource with that TargetSessionAttributes.
if (_dataSource is NpgsqlMultiHostDataSource multiHostDataSource && settings.TargetSessionAttributesParsed.HasValue)
_dataSource = multiHostDataSource.WithTargetSession(settings.TargetSessionAttributesParsed.Value);
// The pool was found, but only under the canonical key - we're using a different version
// for the first time. Map it via our own key for next time.
_dataSource = PoolManager.Pools.GetOrAdd(_connectionString, _dataSource);
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return;
}
}

// Really unseen, need to create a new pool
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