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Overview
Comment: | Add initial draft of the custom connection pool feature. |
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Downloads: | Tarball | ZIP archive |
Timelines: | family | ancestors | descendants | both | customPool |
Files: | files | file ages | folders |
SHA1: |
44b92245a6037ad146db6b392d7a16b0 |
User & Date: | mistachkin 2013-02-15 08:36:02.107 |
Context
2013-02-16
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00:23 | Add custom connection pool changes to the version history docs. Pursuant to [393d954be0]. check-in: abc8fb3a6f user: mistachkin tags: customPool | |
2013-02-15
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08:36 | Add initial draft of the custom connection pool feature. check-in: 44b92245a6 user: mistachkin tags: customPool | |
2013-02-13
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21:59 | Add doc wording to clarify that the connection pool will not work properly in WPF applications. Pursuant to [393d954be0]. check-in: dabfe38a9e user: mistachkin tags: trunk | |
Changes
Changes to System.Data.SQLite/SQLiteConnection.cs.
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195 196 197 198 199 200 201 | /// <description>Y</description> /// </item> /// <item> /// <description>Pooling</description> /// <description> /// <b>True</b> - Use connection pooling.<br/> /// <b>False</b> - Do not use connection pooling.<br/><br/> | > | | | < | 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 | /// <description>Y</description> /// </item> /// <item> /// <description>Pooling</description> /// <description> /// <b>True</b> - Use connection pooling.<br/> /// <b>False</b> - Do not use connection pooling.<br/><br/> /// <b>WARNING:</b> When using the default connection pool implementation, /// setting this property to True should be avoided by applications that make /// use of COM (either directly or indirectly) due to possible deadlocks that /// can occur during the finalization of some COM objects. /// </description> /// <description>N</description> /// <description>False</description> /// </item> /// <item> /// <description>FailIfMissing</description> /// <description><b>True</b> - Don't create the database if it does not exist, throw an error instead<br/><b>False</b> - Automatically create the database if it does not exist</description> |
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634 635 636 637 638 639 640 641 642 643 644 645 646 647 | { lock (_syncRoot) { _handlers -= value; } } } /////////////////////////////////////////////////////////////////////////////////////////////// #region Backup API Members /// <summary> /// Backs up the database, using the specified database connection as the /// destination. | > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > | 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674 675 676 677 678 679 680 681 682 683 684 685 | { lock (_syncRoot) { _handlers -= value; } } } /////////////////////////////////////////////////////////////////////////////////////////////// /// <summary> /// This property is used to obtain or set the custom connection pool /// implementation to use, if any. Setting this property to null will /// cause the default connection pool implementation to be used. /// </summary> public static ISQLiteConnectionPool ConnectionPool { get { return SQLiteConnectionPool.GetConnectionPool(); } set { SQLiteConnectionPool.SetConnectionPool(value); } } /////////////////////////////////////////////////////////////////////////////////////////////// /// <summary> /// Creates and returns a new managed database connection handle. This /// method is intended to be used by implementations of the /// <see cref="ISQLiteConnectionPool" /> interface only. In theory, it /// could be used by other classes; however, that usage is not supported. /// </summary> /// <param name="nativeHandle"> /// This must be a native database connection handle returned by the /// SQLite core library and it must remain valid and open during the /// entire duration of the calling method. /// </param> /// <returns> /// The new managed database connection handle or null if it cannot be /// created. /// </returns> public static object CreateHandle( IntPtr nativeHandle ) { if (nativeHandle == IntPtr.Zero) return null; return new SQLiteConnectionHandle(nativeHandle); } /////////////////////////////////////////////////////////////////////////////////////////////// #region Backup API Members /// <summary> /// Backs up the database, using the specified database connection as the /// destination. |
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1173 1174 1175 1176 1177 1178 1179 | /// <description>Y</description> /// </item> /// <item> /// <description>Pooling</description> /// <description> /// <b>True</b> - Use connection pooling.<br/> /// <b>False</b> - Do not use connection pooling.<br/><br/> | > | | | < | 1211 1212 1213 1214 1215 1216 1217 1218 1219 1220 1221 1222 1223 1224 1225 1226 1227 1228 | /// <description>Y</description> /// </item> /// <item> /// <description>Pooling</description> /// <description> /// <b>True</b> - Use connection pooling.<br/> /// <b>False</b> - Do not use connection pooling.<br/><br/> /// <b>WARNING:</b> When using the default connection pool implementation, /// setting this property to True should be avoided by applications that /// make use of COM (either directly or indirectly) due to possible /// deadlocks that can occur during the finalization of some COM objects. /// </description> /// <description>N</description> /// <description>False</description> /// </item> /// <item> /// <description>FailIfMissing</description> /// <description><b>True</b> - Don't create the database if it does not exist, throw an error instead<br/><b>False</b> - Automatically create the database if it does not exist</description> |
︙ | ︙ |
Changes to System.Data.SQLite/SQLiteConnectionPool.cs.
1 2 3 4 5 6 7 8 9 | /******************************************************** * ADO.NET 2.0 Data Provider for SQLite Version 3.X * Written by Robert Simpson (robert@blackcastlesoft.com) * * Released to the public domain, use at your own risk! ********************************************************/ namespace System.Data.SQLite { | | | | > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > | | < | | > > > > | > > > > > > > > | | > > > > > > > > > > > > > > > > > > > > > > | > | > > > > > > > > > > > > | | > > > > > | > | > > > > > > | < > | > | > | > | > | > > > > > > > > > > > > > > > > | > > > > > > > > > > > | > > > > > > > > > | > | > > > > > > > > | > > > | | | | > > | | | | | > > | | | | | > > > > | | | > | > | > > > | > > | > > | > | | | | | | | | > > > > | > > > > > > | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > 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/******************************************************** * ADO.NET 2.0 Data Provider for SQLite Version 3.X * Written by Robert Simpson (robert@blackcastlesoft.com) * * Released to the public domain, use at your own risk! ********************************************************/ namespace System.Data.SQLite { using System; using System.Collections.Generic; using System.Threading; /////////////////////////////////////////////////////////////////////////// #region Public Connection Pool Interface /// <summary> /// This interface represents a custom connection pool implementation /// usable by System.Data.SQLite. /// </summary> public interface ISQLiteConnectionPool { /// <summary> /// Counts the number of pool entries matching the specified file name. /// </summary> /// <param name="fileName"> /// The file name to match or null to match all files. /// </param> /// <param name="counts"> /// The pool entry counts for each matching file. /// </param> /// <param name="openCount"> /// The total number of connections successfully opened from any pool. /// </param> /// <param name="closeCount"> /// The total number of connections successfully closed from any pool. /// </param> /// <param name="totalCount"> /// The total number of pool entries for all matching files. /// </param> void GetCounts(string fileName, ref Dictionary<string, int> counts, ref int openCount, ref int closeCount, ref int totalCount); /// <summary> /// Disposes of all pooled connections associated with the specified /// database file name. /// </summary> /// <param name="fileName"> /// The database file name. /// </param> void ClearPool(string fileName); /// <summary> /// Disposes of all pooled connections. /// </summary> void ClearAllPools(); /// <summary> /// Adds a connection to the pool of those associated with the /// specified database file name. /// </summary> /// <param name="fileName"> /// The database file name. /// </param> /// <param name="handle"> /// The database connection handle. /// </param> /// <param name="version"> /// The connection pool version at the point the database connection /// handle was received from the connection pool. This is also the /// connection pool version that the database connection handle was /// created under. /// </param> void Add(string fileName, object handle, int version); /// <summary> /// Removes a connection from the pool of those associated with the /// specified database file name with the intent of using it to /// interact with the database. /// </summary> /// <param name="fileName"> /// The database file name. /// </param> /// <param name="maxPoolSize"> /// The new maximum size of the connection pool for the specified /// database file name. /// </param> /// <param name="version"> /// The connection pool version associated with the returned database /// connection handle, if any. /// </param> /// <returns> /// The database connection handle associated with the specified /// database file name or null if it cannot be obtained. /// </returns> object Remove(string fileName, int maxPoolSize, out int version); } #endregion /////////////////////////////////////////////////////////////////////////// /// <summary> /// This default method implementations in this class should not be used by /// applications that make use of COM (either directly or indirectly) due to /// possible deadlocks that can occur during finalization of some COM objects. /// </summary> internal static class SQLiteConnectionPool { #region Private Pool Class /// <summary> /// Keeps track of connections made on a specified file. The PoolVersion /// dictates whether old objects get returned to the pool or discarded /// when no longer in use. /// </summary> private sealed class PoolQueue { #region Private Data /// <summary> /// The queue of weak references to the actual database connection /// handles. /// </summary> internal readonly Queue<WeakReference> Queue = new Queue<WeakReference>(); /////////////////////////////////////////////////////////////////// /// <summary> /// This pool version associated with the database connection /// handles in this pool queue. /// </summary> internal int PoolVersion; /////////////////////////////////////////////////////////////////// /// <summary> /// The maximum size of this pool queue. /// </summary> internal int MaxPoolSize; #endregion /////////////////////////////////////////////////////////////////// #region Private Constructors /// <summary> /// Constructs a connection pool queue using the specified version /// and maximum size. Normally, all the database connection /// handles in this pool are associated with a single database file /// name. /// </summary> /// <param name="version"> /// The initial pool version for this connection pool queue. /// </param> /// <param name="maxSize"> /// The initial maximum size for this connection pool queue. /// </param> internal PoolQueue( int version, int maxSize ) { PoolVersion = version; MaxPoolSize = maxSize; } #endregion } #endregion /////////////////////////////////////////////////////////////////////// #region Private Static Data /// <summary> /// This field is used to synchronize access to the private static data /// in this class. /// </summary> private static readonly object _syncRoot = new object(); /////////////////////////////////////////////////////////////////////// /// <summary> /// When this field is non-null, it will be used to provide the /// implementation of all the connection pool methods; otherwise, /// the default method implementations will be used. /// </summary> private static ISQLiteConnectionPool _connectionPool = null; /////////////////////////////////////////////////////////////////////// /// <summary> /// The dictionary of connection pools, based on the normalized file /// name of the SQLite database. /// </summary> private static SortedList<string, PoolQueue> _queueList = new SortedList<string, PoolQueue>(StringComparer.OrdinalIgnoreCase); /////////////////////////////////////////////////////////////////////// /// <summary> /// The default version number new pools will get. /// </summary> private static int _poolVersion = 1; /////////////////////////////////////////////////////////////////////// /// <summary> /// The number of connections successfully opened from any pool. /// This value is incremented by the Remove method. /// </summary> private static int _poolOpened = 0; /////////////////////////////////////////////////////////////////////// /// <summary> /// The number of connections successfully closed from any pool. /// This value is incremented by the Add method. /// </summary> private static int _poolClosed = 0; #endregion /////////////////////////////////////////////////////////////////////// #region ISQLiteConnectionPool Members (Static, Non-Formal) /// <summary> /// Counts the number of pool entries matching the specified file name. /// </summary> /// <param name="fileName"> /// The file name to match or null to match all files. /// </param> /// <param name="counts"> /// The pool entry counts for each matching file. /// </param> /// <param name="openCount"> /// The total number of connections successfully opened from any pool. /// </param> /// <param name="closeCount"> /// The total number of connections successfully closed from any pool. /// </param> /// <param name="totalCount"> /// The total number of pool entries for all matching files. /// </param> internal static void GetCounts( string fileName, ref Dictionary<string, int> counts, ref int openCount, ref int closeCount, ref int totalCount ) { ISQLiteConnectionPool connectionPool = GetConnectionPool(); if (connectionPool != null) { connectionPool.GetCounts( fileName, ref counts, ref openCount, ref closeCount, ref totalCount); } else { lock (_syncRoot) { openCount = _poolOpened; closeCount = _poolClosed; if (counts == null) { counts = new Dictionary<string, int>( StringComparer.OrdinalIgnoreCase); } if (fileName != null) { PoolQueue queue; if (_queueList.TryGetValue(fileName, out queue)) { Queue<WeakReference> poolQueue = queue.Queue; int count = (poolQueue != null) ? poolQueue.Count : 0; counts.Add(fileName, count); totalCount += count; } } else { foreach (KeyValuePair<string, PoolQueue> pair in _queueList) { if (pair.Value == null) continue; Queue<WeakReference> poolQueue = pair.Value.Queue; int count = (poolQueue != null) ? poolQueue.Count : 0; counts.Add(pair.Key, count); totalCount += count; } } } } } /////////////////////////////////////////////////////////////////////// /// <summary> /// Disposes of all pooled connections associated with the specified /// database file name. /// </summary> /// <param name="fileName"> /// The database file name. /// </param> internal static void ClearPool(string fileName) { ISQLiteConnectionPool connectionPool = GetConnectionPool(); if (connectionPool != null) { connectionPool.ClearPool(fileName); } else { lock (_syncRoot) { PoolQueue queue; if (_queueList.TryGetValue(fileName, out queue)) { queue.PoolVersion++; Queue<WeakReference> poolQueue = queue.Queue; if (poolQueue == null) return; while (poolQueue.Count > 0) { WeakReference connection = poolQueue.Dequeue(); if (connection == null) continue; SQLiteConnectionHandle handle = connection.Target as SQLiteConnectionHandle; if (handle != null) handle.Dispose(); GC.KeepAlive(handle); } } } } } /////////////////////////////////////////////////////////////////////// /// <summary> /// Disposes of all pooled connections. /// </summary> internal static void ClearAllPools() { ISQLiteConnectionPool connectionPool = GetConnectionPool(); if (connectionPool != null) { connectionPool.ClearAllPools(); } else { lock (_syncRoot) { foreach (KeyValuePair<string, PoolQueue> pair in _queueList) { if (pair.Value == null) continue; Queue<WeakReference> poolQueue = pair.Value.Queue; while (poolQueue.Count > 0) { WeakReference connection = poolQueue.Dequeue(); if (connection == null) continue; SQLiteConnectionHandle handle = connection.Target as SQLiteConnectionHandle; if (handle != null) handle.Dispose(); GC.KeepAlive(handle); } // // NOTE: Keep track of the highest revision so we can // go one higher when we are finished. // if (_poolVersion <= pair.Value.PoolVersion) _poolVersion = pair.Value.PoolVersion + 1; } // // NOTE: All pools are cleared and we have a new highest // version number to force all old version active // items to get discarded instead of going back to // the queue when they are closed. We can get away // with this because we have pumped up the pool // version out of range of all active connections, // so they will all get discarded when they try to // put themselves back into their pools. // _queueList.Clear(); } } } /////////////////////////////////////////////////////////////////////// /// <summary> /// Adds a connection to the pool of those associated with the /// specified database file name. /// </summary> /// <param name="fileName"> /// The database file name. /// </param> /// <param name="handle"> /// The database connection handle. /// </param> /// <param name="version"> /// The connection pool version at the point the database connection /// handle was received from the connection pool. This is also the /// connection pool version that the database connection handle was /// created under. /// </param> internal static void Add( string fileName, SQLiteConnectionHandle handle, int version ) { ISQLiteConnectionPool connectionPool = GetConnectionPool(); if (connectionPool != null) { connectionPool.Add(fileName, handle, version); } else { lock (_syncRoot) { // // NOTE: If the queue does not exist in the pool, then it // must have been cleared sometime after the // connection was created. // PoolQueue queue; if (_queueList.TryGetValue(fileName, out queue) && (version == queue.PoolVersion)) { ResizePool(queue, true); Queue<WeakReference> poolQueue = queue.Queue; if (poolQueue == null) return; poolQueue.Enqueue(new WeakReference(handle, false)); Interlocked.Increment(ref _poolClosed); } else { handle.Close(); } GC.KeepAlive(handle); } } } /////////////////////////////////////////////////////////////////////// /// <summary> /// Removes a connection from the pool of those associated with the /// specified database file name with the intent of using it to /// interact with the database. /// </summary> /// <param name="fileName"> /// The database file name. /// </param> /// <param name="maxPoolSize"> /// The new maximum size of the connection pool for the specified /// database file name. /// </param> /// <param name="version"> /// The connection pool version associated with the returned database /// connection handle, if any. /// </param> /// <returns> /// The database connection handle associated with the specified /// database file name or null if it cannot be obtained. /// </returns> internal static SQLiteConnectionHandle Remove( string fileName, int maxPoolSize, out int version ) { ISQLiteConnectionPool connectionPool = GetConnectionPool(); if (connectionPool != null) { return connectionPool.Remove(fileName, maxPoolSize, out version) as SQLiteConnectionHandle; } else { int localVersion; Queue<WeakReference> poolQueue; // // NOTE: This lock cannot be held while checking the queue for // available connections because other methods of this // class are called from the GC finalizer thread and we // use the WaitForPendingFinalizers method (below). // Holding this lock while calling that method would // therefore result in a deadlock. Instead, this lock // is held only while a temporary copy of the queue is // created, and if necessary, when committing changes // back to that original queue prior to returning from // this method. // lock (_syncRoot) { PoolQueue queue; // // NOTE: Default to the highest pool version. // version = _poolVersion; // // NOTE: If we didn't find a pool for this file, create one // even though it will be empty. We have to do this // here because otherwise calling ClearPool() on the // file will not work for active connections that have // never seen the pool yet. // if (!_queueList.TryGetValue(fileName, out queue)) { queue = new PoolQueue(_poolVersion, maxPoolSize); _queueList.Add(fileName, queue); return null; } // // NOTE: We found a pool for this file, so use its version // number. // version = localVersion = queue.PoolVersion; queue.MaxPoolSize = maxPoolSize; // // NOTE: Now, resize the pool to the new maximum size, if // necessary. // ResizePool(queue, false); // // NOTE: Try and get a pooled connection from the queue. // poolQueue = queue.Queue; if (poolQueue == null) return null; // // NOTE: Temporarily tranfer the queue for this file into // a local variable. The queue for this file will // be modified and then committed back to the real // pool list (below) prior to returning from this // method. // _queueList.Remove(fileName); poolQueue = new Queue<WeakReference>(poolQueue); } try { while (poolQueue.Count > 0) { WeakReference connection = poolQueue.Dequeue(); if (connection == null) continue; SQLiteConnectionHandle handle = connection.Target as SQLiteConnectionHandle; if (handle == null) continue; // // BUGFIX: For ticket [996d13cd87], step #1. After // this point, make sure that the finalizer for // the connection handle just obtained from the // queue cannot START running (i.e. it may // still be pending but it will no longer start // after this point). // GC.SuppressFinalize(handle); try { // // BUGFIX: For ticket [996d13cd87], step #2. Now, // we must wait for all pending finalizers // which have STARTED running and have not // yet COMPLETED. This must be done just // in case the finalizer for the connection // handle just obtained from the queue has // STARTED running at some point before // SuppressFinalize was called on it. // // After this point, checking properties of // the connection handle (e.g. IsClosed) // should work reliably without having to // worry that they will (due to the // finalizer) change out from under us. // GC.WaitForPendingFinalizers(); // // BUGFIX: For ticket [996d13cd87], step #3. Next, // verify that the connection handle is // actually valid and [still?] not closed // prior to actually returning it to our // caller. // if (!handle.IsInvalid && !handle.IsClosed) { Interlocked.Increment(ref _poolOpened); return handle; } } finally { // // BUGFIX: For ticket [996d13cd87], step #4. Next, // we must re-register the connection // handle for finalization now that we have // a strong reference to it (i.e. the // finalizer will not run at least until // the connection is subsequently closed). // GC.ReRegisterForFinalize(handle); } GC.KeepAlive(handle); } } finally { // // BUGFIX: For ticket [996d13cd87], step #5. Finally, // commit any changes to the pool/queue for this // database file. // lock (_syncRoot) { // // NOTE: We must check [again] if a pool exists for // this file because one may have been added // while the search for an available connection // was in progress (above). // PoolQueue queue; Queue<WeakReference> newPoolQueue; bool addPool; if (_queueList.TryGetValue(fileName, out queue)) { addPool = false; } else { addPool = true; queue = new PoolQueue(localVersion, maxPoolSize); } newPoolQueue = queue.Queue; while (poolQueue.Count > 0) newPoolQueue.Enqueue(poolQueue.Dequeue()); ResizePool(queue, false); if (addPool) _queueList.Add(fileName, queue); } } return null; } } #endregion /////////////////////////////////////////////////////////////////////// #region Private Helper Methods /// <summary> /// This method is used to obtain a reference to the custom connection /// pool implementation currently in use, if any. /// </summary> /// <returns> /// The custom connection pool implementation or null if the default /// connection pool implementation should be used. /// </returns> internal static ISQLiteConnectionPool GetConnectionPool() { lock (_syncRoot) { return _connectionPool; } } /////////////////////////////////////////////////////////////////////// /// <summary> /// This method is used to set the reference to the custom connection /// pool implementation to use, if any. /// </summary> /// <param name="connectionPool"> /// The custom connection pool implementation to use or null if the /// default connection pool implementation should be used. /// </param> internal static void SetConnectionPool( ISQLiteConnectionPool connectionPool ) { lock (_syncRoot) { _connectionPool = connectionPool; } } /////////////////////////////////////////////////////////////////////// /// <summary> /// We do not have to thread-lock anything in this function, because it /// is only called by other functions above which already take the lock. /// </summary> /// <param name="queue"> /// The pool queue to resize. /// </param> /// <param name="add"> /// If a function intends to add to the pool, this is true, which /// forces the resize to take one more than it needs from the pool. /// </param> private static void ResizePool( PoolQueue queue, bool add ) { int target = queue.MaxPoolSize; if (add && target > 0) target--; Queue<WeakReference> poolQueue = queue.Queue; if (poolQueue == null) return; while (poolQueue.Count > target) { WeakReference connection = poolQueue.Dequeue(); if (connection == null) continue; SQLiteConnectionHandle handle = connection.Target as SQLiteConnectionHandle; if (handle != null) handle.Dispose(); GC.KeepAlive(handle); } } #endregion } } |