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SqliteConnectionPool.cs
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SqliteConnectionPool.cs
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// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading;
namespace Microsoft.Data.Sqlite
{
internal class SqliteConnectionPool
{
private static readonly Random _random = new();
private readonly SqliteConnectionStringBuilder _connectionOptions;
private readonly List<SqliteConnectionInternal> _connections = [];
private readonly Stack<SqliteConnectionInternal> _warmPool = new();
private readonly Stack<SqliteConnectionInternal> _coldPool = new();
private Timer? _pruneTimer;
private State _state = State.Active;
public SqliteConnectionPool(SqliteConnectionStringBuilder connectionOptions)
{
lock (_random)
{
// 2-4 minutes in 10 second intervals
var prunePeriod = TimeSpan.FromSeconds(_random.Next(2 * 6, 4 * 6) * 10);
_pruneTimer = new Timer(PruneCallback, null, prunePeriod, prunePeriod);
}
_connectionOptions = connectionOptions;
}
public int Count
=> _connections.Count;
public void Shutdown()
{
_state = State.Disabled;
_pruneTimer?.Dispose();
_pruneTimer = null;
}
public SqliteConnectionInternal GetConnection()
{
SqliteConnectionInternal? connection = null;
do
{
lock (_connections)
{
if (!TryPop(_warmPool, out connection)
&& !TryPop(_coldPool, out connection)
&& (Count % 2 == 1 || !ReclaimLeakedConnections()))
{
connection = new SqliteConnectionInternal(_connectionOptions, this);
_connections.Add(connection);
}
}
}
while (connection == null);
return connection;
}
private static bool TryPop(Stack<SqliteConnectionInternal> stack, out SqliteConnectionInternal? connection)
{
#if NET5_0_OR_GREATER
return stack.TryPop(out connection);
#else
if (stack.Count > 0)
{
connection = stack.Pop();
return true;
}
connection = null;
return false;
#endif
}
public void Return(SqliteConnectionInternal connection)
{
lock (_connections)
{
connection.Deactivate();
if (_state != State.Disabled
&& connection.CanBePooled)
{
_warmPool.Push(connection);
}
else
{
DisposeConnection(connection);
}
}
}
public void Clear()
{
lock (_connections)
{
foreach (var connection in _connections)
{
connection.DoNotPool();
}
while (TryPop(_warmPool, out var connection))
{
DisposeConnection(connection!);
}
while (TryPop(_coldPool, out var connection))
{
DisposeConnection(connection!);
}
ReclaimLeakedConnections();
}
}
private void PruneCallback(object? _)
{
lock (_connections)
{
while (TryPop(_coldPool, out var connection))
{
DisposeConnection(connection!);
}
while (TryPop(_warmPool, out var connection))
{
_coldPool.Push(connection!);
}
}
}
private void DisposeConnection(SqliteConnectionInternal connection)
{
lock (_connections)
{
_connections.Remove(connection);
}
connection.Dispose();
}
private bool ReclaimLeakedConnections()
{
var leakedConnectionsFound = false;
List<SqliteConnectionInternal> leakedConnections;
lock (_connections)
{
leakedConnections = _connections.Where(c => c.Leaked).ToList();
}
foreach (var connection in leakedConnections)
{
leakedConnectionsFound = true;
Return(connection);
}
return leakedConnectionsFound;
}
private enum State
{
Active,
Disabled
}
}
}