context: //
  // Mono.Data.TdsClient.TdsConnectionPool.cs
  //
  // Author:
  //   Lluis Sanchez Gual (lluis@ximian.com)
  //   Christian Hergert (christian.hergert@gmail.com)
  //   Gonzalo Paniagua Javier (gonzalo@novell.com)
  //
  // Copyright (C) 2004 Novell, Inc.
  // Copyright (C) 2009 Novell, Inc.
  
  //
  // Permission is hereby granted, free of charge, to any person obtaining
  // a copy of this software and associated documentation files (the
  // "Software"), to deal in the Software without restriction, including
  // without limitation the rights to use, copy, modify, merge, publish,
  // distribute, sublicense, and/or sell copies of the Software, and to
  // permit persons to whom the Software is furnished to do so, subject to
  // the following conditions:
  // 
  // The above copyright notice and this permission notice shall be
  // included in all copies or substantial portions of the Software.
  // 
  // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  // EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  // MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
  // NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
  // LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
  // OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
  // WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  //
  
  using System;
  using System.Collections;
  using System.Text;
  using System.Threading;
  
  namespace Mono.Data.Tds.Protocol 
  {
  	public class TdsConnectionPoolManager
  	{
  		Hashtable pools = Hashtable.Synchronized (new Hashtable ());
  		TdsVersion version;
  		
  		public TdsConnectionPoolManager (TdsVersion version)
  		{
  			this.version = version;
  		}
  		
  		public TdsConnectionPool GetConnectionPool (string connectionString, TdsConnectionInfo info)
  		{
  			TdsConnectionPool pool = (TdsConnectionPool) pools [connectionString];
  			if (pool == null) {
  				pools [connectionString] = new TdsConnectionPool (this, info);
  				pool = (TdsConnectionPool) pools [connectionString];
  			}
  			return pool;
  		}
  
  		public TdsConnectionPool GetConnectionPool (string connectionString)
  		{
  			return (TdsConnectionPool) pools [connectionString];
  		}
  
  		public virtual Tds CreateConnection (TdsConnectionInfo info)
  		{
  			//Console.WriteLine ("CreateConnection: TdsVersion:{0}", version);
  			switch (version)
  			{
  				case TdsVersion.tds42:
  					return new Tds42 (info.DataSource, info.Port, info.PacketSize, info.Timeout);
  				case TdsVersion.tds50:
  					return new Tds50 (info.DataSource, info.Port, info.PacketSize, info.Timeout);
  				case TdsVersion.tds70:
  					return new Tds70 (info.DataSource, info.Port, info.PacketSize, info.Timeout, info.LifeTime);
  				case TdsVersion.tds80:
  					return new Tds80 (info.DataSource, info.Port, info.PacketSize, info.Timeout, info.LifeTime);
  			}
  			throw new NotSupportedException ();
  		}
  
  		public IDictionary GetConnectionPool ()
  		{
  			return pools;
  		}
  	}
  	
  	public class TdsConnectionInfo
  	{
  		[Obsolete ("Use the constructor that receives a lifetime parameter")]
  		public TdsConnectionInfo (string dataSource, int port, int packetSize, int timeout, int minSize, int maxSize)
  			: this (dataSource, port, packetSize, timeout, minSize, maxSize, 0)
  		{
  		}
  
  		public TdsConnectionInfo (string dataSource, int port, int packetSize, int timeout, int minSize, int maxSize, int lifeTime)
  		{
  			DataSource = dataSource;
  			Port = port;
  			PacketSize = packetSize;
  			Timeout = timeout;
  			PoolMinSize = minSize;
  			PoolMaxSize = maxSize;
  			LifeTime = lifeTime;
  		}
  		
  		public string DataSource;
  		public int Port;
  		public int PacketSize;
  		public int Timeout;
  		public int LifeTime;
  		public int PoolMinSize;
  		public int PoolMaxSize;
  
  		public override string ToString ()
  		{
  			StringBuilder sb = new StringBuilder ();
  			sb.AppendFormat ("DataSouce: {0}\n", DataSource);
  			sb.AppendFormat ("Port: {0}\n", Port);
  			sb.AppendFormat ("PacketSize: {0}\n", PacketSize);
  			sb.AppendFormat ("Timeout: {0}\n", Timeout);
  			sb.AppendFormat ("PoolMinSize: {0}\n", PoolMinSize);
  			sb.AppendFormat ("PoolMaxSize: {0}", PoolMaxSize);
  			return sb.ToString ();
  		}
  	}
  
  	public class TdsConnectionPool
  	{
  		TdsConnectionInfo info;
  		bool no_pooling;
  		TdsConnectionPoolManager manager;
  		Queue available;
  		ArrayList conns;
  		
  		public TdsConnectionPool (TdsConnectionPoolManager manager, TdsConnectionInfo info)
  		{
  			this.info = info;
  			this.manager = manager;
  			conns = new ArrayList (info.PoolMaxSize);
  			available = new Queue (info.PoolMaxSize);
  			InitializePool ();
  		}
  
  		void InitializePool ()
  		{
  			/* conns.Count might not be 0 when we are resetting the connection pool */
  			for (int i = conns.Count; i < info.PoolMinSize; i++) {
  				try {
  					Tds t = manager.CreateConnection (info);
  					conns.Add (t);
  					available.Enqueue (t);
  				} catch {
  					// Ignore. GetConnection will throw again.
  				}
  			}
  		}
  
  		public bool Pooling {
  			get { return !no_pooling; }
  			set { no_pooling = !value; }
  		}
  
  		#region Methods
  
  		int in_progress;
  		public Tds GetConnection ()
  		{
  			if (no_pooling)
  				return manager.CreateConnection (info);
  
  			Tds result = null;
  			bool create_new;
  			int retries = info.PoolMaxSize * 2;
  retry:
  			while (result == null) {
  				create_new = false;
  				lock (available) {
  					if (available.Count > 0) {
  						result = (Tds) available.Dequeue ();
  						break; // .. and do the reset out of the loop
  					}
  					Monitor.Enter (conns);
  					try {
  						if (conns.Count >= info.PoolMaxSize - in_progress) {
  							Monitor.Exit (conns);
  							bool got_lock = Monitor.Wait (available, info.Timeout * 1000);
  							if (!got_lock) {
  								throw new InvalidOperationException (
  									"Timeout expired. The timeout period elapsed before a " +
  									"connection could be obtained. A possible explanation " +
  									"is that all the connections in the pool are in use, " +
  									"and the maximum pool size is reached.");
  							} else if (available.Count > 0) {
  								result = (Tds) available.Dequeue ();
  								break; // .. and do the reset out of the loop
  							}
  							continue;
  						} else {
  							create_new = true;
  							in_progress++;
  						}
  					} finally {
  						Monitor.Exit (conns); // Exiting if not owned is ok < 2.x
  					}
  				}
  				if (create_new) {
  					try {
  						result = manager.CreateConnection (info);
  						lock (conns)
  							conns.Add (result);
  						return result;
  					} finally {
  						lock (available)
  							in_progress--;
  					}
  				}
  			}
  
  			bool remove_cnc = true;
  			Exception exc = null;
  			try {
  				remove_cnc = (!result.IsConnected || !result.Reset ());
  			} catch (Exception e) {
  				remove_cnc = true;
  				exc = e;
  			}
  			if (remove_cnc) {
  				lock (conns)
  					conns.Remove (result);
  				result.Disconnect ();
  				retries--;
  				if (retries == 0)
  					throw exc;
  				result = null;
  				goto retry;
  			}
  			return result;
  		}
  
  		public void ReleaseConnection (Tds connection)
  		{
  			if (connection == null)
  				return;
  			if (no_pooling) {
  				connection.Disconnect ();
  				return;
  			}
  
  			if (connection.poolStatus == 2 || connection.Expired) {
  				lock (conns)
  					conns.Remove (connection);
  				connection.Disconnect ();
  				connection = null;
  			}
  			lock (available) {
  				if (connection != null) // connection is still open
   					available.Enqueue (connection);
  				// We pulse even if we don't queue, because null means that there's a slot
  				// available in 'conns'
   				Monitor.Pulse (available);
  			}
  		}
  
  		public void ResetConnectionPool ()
  		{
  			lock (available) {
  				lock (conns) {
  					Tds tds;
  					int i;
  					for (i = conns.Count - 1; i >= 0; i--) {
  
gt: 						tds = (Tds) conns [i];