postgres/src/interfaces/jdbc/org/postgresql/xa/XAConnectionImpl.java

/*
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* THIS SOFTWARE IS PROVIDED BY EXOFFICE TECHNOLOGIES AND CONTRIBUTORS
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* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
* OF THE POSSIBILITY OF SUCH DAMAGE.
*
* Copyright 1999 (C) Exoffice Technologies Inc. All Rights Reserved.
*
* $Id: XAConnectionImpl.java,v 1.3 2001/11/19 22:33:39 momjian Exp $
*/


package org.postgresql.xa;


import java.sql.Connection;
import java.sql.SQLException;
import java.util.Vector;
import javax.sql.XAConnection;
import javax.sql.PooledConnection;
import javax.sql.ConnectionEvent;
import javax.sql.ConnectionEventListener;
import javax.transaction.RollbackException;
import javax.transaction.xa.XAResource;
import javax.transaction.xa.Xid;
import javax.transaction.xa.XAException;


/*
 * Implements an X/A connection that can be pooled and managed from
 * inside a transaction monitor. This is the XA connection returned
 * to the application server from the {@link XADataSourceImpl} and
 * will be used to obtain {@link ClientConnection} for the
 * application.
 * <p>
 * If the transaction is managed through the JDBC interface, this
 * connection will reference the underlying JDBC connection directly.
 * If this resource is enlisted with a global transaction through
 * the {@link XAResource} interface, it will reference a transactional
 * connection, or {@link TxConnection}. Such a connection may be
 * shared by two or more XA connections enlisted with the same
 * transaction.
 *
 *
 * @author <a href="arkin@exoffice.com">Assaf Arkin</a>
 * @version 1.0
 * @see ClientConnection
 * @see ConnectionEventListener
 * @see TxConnection
 */
public final class XAConnectionImpl
			implements XAConnection, XAResource
{


	/*
	 * This is the underlying JDBC connection represented
	 * by this pooled connection. This variable may initially be null,
	 * in which case {@link #getUnderlying} will return a new
	 * connection and set this variable. This variable is mutually
	 * exclusive with {@link #_txConn} and is always null for
	 * connections inside a transaction.
	 */
	Connection _underlying;


	/*
	 * If this connection is part of a global transaction, this
	 * object identifies the transaction. The transaction's
	 * underlying JDBC connection is exposed through this object and
	 * {@link #_underlying} is null. If this connection is closed,
	 * then the connection has been timedout. Commit/rollback will
	 * always set this variable to null.
	 */
	private TxConnection _txConn;


	/*
	 * The client connection last handed to the application. If the
	 * application calls {@link #getConnection} again, we should hand
	 * out a new client connection and render the previous one closed.
	 */
	// No longer in use, see _clientId
	//private ClientConnection			  _clientConn;


	/*
	 * An event listener can be registered and notified when the
	 * client connection has been closed by the application or a
	 * fatal error rendered it unuseable.
	 */
	private ConnectionEventListener _listener;


	/*
	 * The resource manager is used to share connections within the
	 * same transaction.
	 */
	private XADataSourceImpl _resManager;


	/*
	 * This is an identifier we hand to the client connection when we
	 * create it. When the client connection asks for the underlying
	 * connection, we compare the identifiers. If since that point we
	 * created a new client connection, we regard an old client
	 * connection as discarded and do not hand it the underlying
	 * connection.
	 * <p>
	 * Previously, when a new client connection was created, we used
	 * a reference to the old one to terminate it. This proved to
	 * not work well, since the client connection could never be
	 * finalized.
	 */
	private int _clientId = 1;


	/*
	 * Construct a new XA/pooled connection with the underlying JDBC
	 * connection suitable for this driver only. This is a one to one
	 * mapping between this connection and the underlying connection.
	 * The underlying connection is only provided for pooled
	 * connections. XA connections are suspect of being enlisted with
	 * a global transaction which might already bear an underlying
	 * connection. If not, one will be created later on.
	 */
	XAConnectionImpl( XADataSourceImpl resManager,
					  Connection underlying )
	{
		_underlying = underlying;
		_resManager = resManager;
	}


	public synchronized void close()
	throws SQLException
	{
		// This is our indication that this connection has been
		// closed programmatically.
		if ( _resManager == null )
			throw new SQLException( "This connection has been closed" );

		// The client connection is no longer useable.
		/* Deprecated: see _clientId
		if ( _clientConn != null )
			_clientConn.terminate();
		*/
		_clientId = -1;

		// The underlying connection is closed and this connection
		// is no longer useable. This method can be called any number
		// of times (e.g. we use it in finalizer).	We do not handle
		// transactions, we just kill the connection.
		try
		{
			if ( _underlying != null )
			{
				_underlying.commit();
				_underlying.close();
			}
			else if ( _txConn != null )
			{
				try
				{
					end( _txConn.xid, TMSUCCESS );
				}
				catch ( XAException except )
				{ }
			}
		}
		finally
		{
			_resManager = null;
			_underlying = null;
			_txConn = null;
			_listener = null;
		}
	}


	public XAResource getXAResource()
	{
		// The connection acts as it's own resource manager
		return this;
	}


	public synchronized void addConnectionEventListener( ConnectionEventListener listener )
	{
		if ( listener == null )
			throw new NullPointerException( "XAConnection: Argument 'listener' is null" );
		if ( _listener != null )
			throw new IllegalStateException( "XAConnection: Only one listener supported per connection" );
		_listener = listener;
	}


	public synchronized void removeConnectionEventListener( ConnectionEventListener listener )
	{
		if ( listener == null )
			throw new NullPointerException( "XAConnection: Argument 'listener' is null" );
		if ( _listener == null || _listener != listener )
			throw new IllegalStateException( "XAConnection: Listener never registered with this pooled connection" );
		_listener = null;
	}


	public synchronized java.sql.Connection getConnection()
	throws SQLException
	{
		// If this pooled connection has been closed, throw an exception.
		if ( _resManager == null )
			throw new SQLException( "This connection has been closed" );

		// If getConnection() was called before and the underlying
		// connection was not closed, we take it away from the previous
		// recieved as per the PooledConnection design.
		/* Deprecated: see _clientId
		if ( _clientConn != null )
			_clientConn.terminate();
		*/

		// If we are handling an underlying connection, we commit the
		// old transaction and are ready to work for a new one.
		// If we are part of a global transaction we hope that end/
		// start were called properly, but we're not longer in that
		// transaction.
		if ( _underlying != null )
		{
			try
			{
				_underlying.commit();
			}
			catch ( SQLException except )
			{
				ConnectionEvent event;

				if ( _listener != null )
				{
					event = new ConnectionEvent( this, except );
					_listener.connectionErrorOccurred( event );
				}
			}
		}

		// Create a new ClientConnection which will be returned to the
		// application. The ClientConnection cannot be closed directly
		// and cannot manage it's own transactions.
		/* Deprecated: see _clientId
		_clientConn = new ClientConnection( this );
		return _clientConn;
		*/
		return new ClientConnection( this, ++_clientId );
	}


	/*
	 * Called by {@link ClientConnection} to notify that the application
	 * has attempted to close the connection. After this call, the client
	 * connection is no longer useable and this pooled connection can be
	 * reused. The event listener is notified immediately.
	 *
	 * @param clientId The {@link ClientConnection} identifier
	 */
	synchronized void notifyClose( int clientId )
	{
		ConnectionEvent event;

		// ClientConnection has been closed, we dissociated it from
		// the underlying connection and notify any listener that this
		// pooled connection can be reused.
		/* Deprecated: see clientId
		_clientConn.terminate();
		_clientConn = null;
		*/
		// We have to expect being called by a ClientConnection that we
		// no longer regard as valid. That's acceptable, we just ignore.
		if ( clientId != _clientId )
			return ;

		// If we are handling an underlying connection, we commit the
		// old transaction and are ready to work for a new one.
		// If we are part of a global transaction we hope that end/
		// start were called properly.
		if ( _underlying != null )
		{
			try
			{
				_underlying.commit();
			}
			catch ( SQLException except )
			{
				if ( _listener != null )
				{
					event = new ConnectionEvent( this, except );
					_listener.connectionErrorOccurred( event );
				}
				return ;
			}
		}
		// Notify the listener.
		if ( _listener != null )
		{
			event = new ConnectionEvent( this );
			_listener.connectionClosed( event );
		}
	}


	/*
	 * Called by {@link ClientConnection} to notify that an error
	 * occured with the underlying connection. If the error is
	 * critical, the underlying connection is closed and the listener
	 * is notified.
	 *
	 * @param clientId The {@link ClientConnection} identifier
	 * @param except The exception raised by the underlying connection
	 */
	synchronized void notifyError( int clientId, SQLException except )
	{
		ConnectionEvent event;

		if ( clientId != _clientId )
			return ;

		// If the connection is not two-phase commit we cannot determine
		// whether the error is critical, we just return. If the connection
		// is two phase commit, but the error is not critical, we return.
		if ( _underlying != null )
		{
			if ( ! ( _underlying instanceof TwoPhaseConnection ) ||
					! ( (TwoPhaseConnection) _underlying ).isCriticalError( except ) )
				return ;
			if ( _txConn.conn == null ||
					! ( _txConn.conn instanceof TwoPhaseConnection ) ||
					! ( (TwoPhaseConnection) _txConn.conn ).isCriticalError( except ) )
				return ;
		}

		// The client connection is no longer useable, the underlying
		// connection (if used) is closed, the TxConnection (if used)
		// is rolledback and this connection dies (but close() may
		// still be called).
		++_clientId;
		if ( _underlying != null )
		{
			try
			{
				_underlying.close();
			}
			catch ( SQLException e2 )
			{
				// Ignore that, we know there's an error.
			}
			_underlying = null;
		}
		else if ( _txConn != null )
		{
			try
			{
				end( _txConn.xid, TMFAIL );
			}
			catch ( XAException e2 )
			{
				// Ignore that, we know there's an error.
			}
			_txConn = null;
		}

		// Notify the listener.
		if ( _listener != null )
		{
			event = new ConnectionEvent( this, except );
			_listener.connectionErrorOccurred( event );
		}
	}


	protected void finalize()
	throws Throwable
	{
		// We are no longer referenced by anyone (including the
		// connection pool). Time to close down.
		close();
	}


	public String toString()
	{
		if ( _underlying != null )
			return "XAConnection: " + _underlying;
		else
			return "XAConnection: unused";
	}


	public synchronized void start( Xid xid, int flags )
	throws XAException
	{
		// General checks.
		if ( xid == null )
			throw new XAException( XAException.XAER_INVAL );
		if ( _txConn != null )
			throw new XAException( XAException.XAER_OUTSIDE );

		synchronized ( _resManager )
		{
			if ( flags == TMNOFLAGS )
			{
				// Starting a new transaction. First, make sure it is
				// not shared with any other connection (need to join
				// for that).
				if ( _resManager.getTxConnection( xid ) != null )
					throw new XAException( XAException.XAER_DUPID );

				// Create a new TxConnection to describe this
				// connection in the context of a transaction and
				// register it with the resource manager so it can
				// be shared.
				try
				{
					_txConn = new TxConnection();
					if ( _underlying != null )
					{
						_txConn.conn = _underlying;
						_underlying = null;
					}
					else
						_txConn.conn = _resManager.newConnection();
					_txConn.xid = xid;
					_txConn.count = 1;
					_txConn.started = System.currentTimeMillis();
					_txConn.timeout = _txConn.started + ( _resManager.getTransactionTimeout() * 1000 );
					_resManager.setTxConnection( xid, _txConn );
				}
				catch ( SQLException except )
				{
					// If error occured at this point, we can only
					// report it as resource manager error.
					if ( _resManager.getLogWriter() != null )
						_resManager.getLogWriter().println( "XAConnection: failed to begin a transaction: " + except );
					throw new XAException( XAException.XAER_RMERR );
				}

				try
				{
					_txConn.conn.setAutoCommit( false );
					try
					{
						if ( _resManager.isolationLevel() != Connection.TRANSACTION_NONE )
							_txConn.conn.setTransactionIsolation( _resManager.isolationLevel() );
					}
					catch ( SQLException e )
					{
						// The underlying driver might not support this
						// isolation level that we use by default.
					}
					if ( _txConn.conn instanceof TwoPhaseConnection )
						( (TwoPhaseConnection) _txConn.conn ).enableSQLTransactions( false );
				}
				catch ( SQLException except )
				{
					// If error occured at this point, we can only
					// report it as resource manager error.
					if ( _resManager.getLogWriter() != null )
						_resManager.getLogWriter().println( "XAConnection: failed to begin a transaction: " + except );
					throw new XAException( XAException.XAER_RMERR );
				}
			}
			else if ( flags == TMJOIN || flags == TMRESUME )
			{
				// We are joining another transaction with an
				// existing TxConnection.
				_txConn = _resManager.getTxConnection( xid );
				if ( _txConn == null )
					throw new XAException( XAException.XAER_INVAL );

				// Update the number of XAConnections sharing this
				// transaction connection.
				if ( flags == TMJOIN && _txConn.count == 0 )
					throw new XAException( XAException.XAER_PROTO );
				++_txConn.count;

				// If we already have an underlying connection (as we can
				// expect to), we should release that underlying connection
				// and make it available to the resource manager.
				if ( _underlying != null )
				{
					_resManager.releaseConnection( _underlying );
					_underlying = null;
				}
			}
			else
				// No other flags supported in start().
				throw new XAException( XAException.XAER_INVAL );
		}
	}


	public synchronized void end( Xid xid, int flags )
	throws XAException
	{
		// General checks.
		if ( xid == null )
			throw new XAException( XAException.XAER_INVAL );
		// Note: we could get end with success or failure even it
		// we were previously excluded from the transaction.
		if ( _txConn == null && flags == TMSUSPEND )
			throw new XAException( XAException.XAER_NOTA );

		synchronized ( _resManager )
		{
			if ( flags == TMSUCCESS || flags == TMFAIL)
			{
				// We are now leaving a transaction we started or
				// joined before. We can expect any of prepare/
				// commit/rollback to be called next, so TxConnection
				// is still valid.

				// If we were suspended from the transaction, we'll
				// join it for the duration of this operation.
				// Make sure the reference count reaches zero by the
				// time we get to prepare.
				if ( _txConn == null )
				{
					_txConn = _resManager.getTxConnection( xid );
					if ( _txConn == null )
						throw new XAException( XAException.XAER_NOTA );
				}
				else
				{
					if ( _txConn.xid != null && ! _txConn.xid.equals( xid ) )
						throw new XAException( XAException.XAER_NOTA );
					--_txConn.count;
				}

				// If transaction failed, we can rollback the
				// transaction and release the underlying connection.
				// We can expect all other resources to recieved the
				// same end notification. We don't expect forget to happen.
				if ( flags == TMFAIL && _txConn.conn != null )
				{
					try
					{
						if ( _txConn.conn instanceof TwoPhaseConnection )
							( (TwoPhaseConnection) _txConn.conn ).enableSQLTransactions( true );
						_txConn.conn.rollback();
						_resManager.releaseConnection( _txConn.conn );
					}
					catch ( SQLException except )
					{
						// There is a problem with the underlying
						// connection, but it was not added to the poll.
					}
					_resManager.setTxConnection( _txConn.xid, null );
					_txConn.conn = null;
					_txConn.xid = null;
				}

				if ( flags == TMSUCCESS)
				{
					// We should be looking for a new transaction.
					// Next thing we might be participating in a new
					// transaction while the current one is being
					// rolled back.
					_txConn = null;
				}
			}
			else if ( flags == TMSUSPEND )
			{
				// We no longer take part in this transaction.
				// Possibly we'll be asked to resume later on, but
				// right now we have to forget about the transaction
				// and the underlying connection.
				--_txConn.count;
				_txConn = null;
			}
			else
				// No other flags supported in end().
				throw new XAException( XAException.XAER_INVAL );
		}
	}


	public synchronized void forget( Xid xid )
	throws XAException
	{
		TxConnection txConn;

		// General checks.
		if ( xid == null )
			throw new XAException( XAException.XAER_INVAL );
		synchronized ( _resManager )
		{
			// We have to forget about the transaction, meaning the
			// transaction no longer exists for this or any other
			// connection. We might be called multiple times.
			txConn = _resManager.setTxConnection( xid, null );
			if ( _txConn == txConn )
				_txConn = null;
			if ( txConn != null )
			{
				if ( txConn.conn != null )
				{
					_resManager.releaseConnection( txConn.conn );
					txConn.conn = null;
				}
				txConn.xid = null;
			}
		}
	}


	public synchronized int prepare( Xid xid )
	throws XAException
	{
		TxConnection txConn;

		// General checks.
		if ( xid == null )
			throw new XAException( XAException.XAER_INVAL );

		synchronized ( _resManager )
		{
			// Technically, prepare may be called for any connection,
			// not just this one.
			txConn = _resManager.getTxConnection( xid );
			if ( txConn == null )
				throw new XAException( XAException.XAER_NOTA );

			// This is an error and should never happen. All other
			// parties in the transaction should have left it before.
			if ( txConn.count > 0 )
				throw new XAException( XAException.XAER_PROTO );

			// If the transaction failed, we have to force a rollback.
			// We track the case of failure due to a timeout.
			if ( txConn.timedOut )
				throw new XAException( XAException.XA_RBTIMEOUT );
			if ( txConn.conn == null )
				throw new XAException( XAException.XA_RBROLLBACK );

			// Since there is no preparation mechanism in a generic
			// JDBC driver, we only test for read-only transaction
			// but do not commit at this point.
			try
			{
				txConn.prepared = true;
				if ( txConn.conn instanceof TwoPhaseConnection )
				{
					// For 2pc connection we ask it to prepare and determine
					// whether it's commiting or read-only. If a rollback
					// exception happens, we report it.
					try
					{
						if ( ( (TwoPhaseConnection) txConn.conn ).prepare() )
							return XA_OK;
						else
						{
							txConn.readOnly = true;
							return XA_RDONLY;
						}
					}
					catch ( SQLException except )
					{
						throw new XAException( XAException.XA_RBROLLBACK );
					}
				}
				else
				{
					// For standard connection we cannot prepare, we can
					// only guess if it's read only.
					if ( txConn.conn.isReadOnly() )
					{
						txConn.readOnly = true;
						return XA_RDONLY;
					}
					return XA_OK;
				}
			}
			catch ( SQLException except )
			{
				try
				{
					// Fatal error in the connection, kill it.
					txConn.conn.close();
				}
				catch ( SQLException e )
				{ }
				txConn.conn = null;
				if ( _resManager.getLogWriter() != null )
					_resManager.getLogWriter().println( "XAConnection: failed to commit a transaction: " + except );
				// If we cannot commit the transaction, force a rollback.
				throw new XAException( XAException.XA_RBROLLBACK );
			}
		}
	}


	public Xid[] recover( int flags )
	throws XAException
	{
		synchronized ( _resManager )
		{
			return _resManager.getTxRecover();
		}
	}


	public synchronized void commit( Xid xid, boolean onePhase )
	throws XAException
	{
		TxConnection txConn;

		// General checks.
		if ( xid == null )
			throw new XAException( XAException.XAER_INVAL );

		synchronized ( _resManager )
		{
			// Technically, commit may be called for any connection,
			// not just this one.
			txConn = _resManager.getTxConnection( xid );
			if ( txConn == null )
				throw new XAException( XAException.XAER_NOTA );

			// If the transaction failed, we have to force
			// a rollback.
			if ( txConn.conn == null )
				throw new XAException( XAException.XA_RBROLLBACK );

			// If connection has been prepared and is read-only,
			// nothing to do at this stage.
			if ( txConn.readOnly )
				return ;

			// This must be a one-phase commite, or the connection
			// should have been prepared before.
			if ( onePhase || txConn.prepared )
			{
				try
				{
					// Prevent multiple commit attempts.
					txConn.readOnly = true;
					if ( txConn.conn instanceof TwoPhaseConnection )
						( (TwoPhaseConnection) txConn.conn ).enableSQLTransactions( true );
					txConn.conn.commit();
				}
				catch ( SQLException except )
				{
					try
					{
						// Unknown error in the connection, better kill it.
						txConn.conn.close();
					}
					catch ( SQLException e )
					{ }
					txConn.conn = null;
					if ( _resManager.getLogWriter() != null )
						_resManager.getLogWriter().println( "XAConnection: failed to commit a transaction: " + except );
					// If we cannot commit the transaction, a heuristic tollback.
					throw new XAException( XAException.XA_HEURRB );
				}
			}
			else
			{
				// 2pc we should have prepared before.
				if ( ! txConn.prepared )
					throw new XAException( XAException.XAER_PROTO );
			}
		}
	}


	public synchronized void rollback( Xid xid )
	throws XAException
	{
		TxConnection txConn;


		// General checks.
		if ( xid == null )
			throw new XAException( XAException.XAER_INVAL );

		synchronized ( _resManager )
		{
			// Technically, rollback may be called for any connection,
			// not just this one.
			txConn = _resManager.getTxConnection( xid );
			if ( txConn == null )
				throw new XAException( XAException.XAER_NOTA );

			// If connection has been prepared and is read-only,
			// nothing to do at this stage. If connection has
			// been terminated any other way, nothing to do
			// either.
			if ( txConn.readOnly || txConn.conn == null )
				return ;

			try
			{
				txConn.prepared = false;
				if ( txConn.conn instanceof TwoPhaseConnection )
					( (TwoPhaseConnection) txConn.conn ).enableSQLTransactions( true );
				txConn.conn.rollback();
			}
			catch ( SQLException except )
			{
				try
				{
					// Unknown error in the connection, better kill it.
					txConn.conn.close();
				}
				catch ( SQLException e )
				{ }
				txConn.conn = null;
				if ( _resManager.getLogWriter() != null )
					_resManager.getLogWriter().println( "XAConnection: failed to rollback a transaction: " + except );
				// If we cannot commit the transaction, a heuristic tollback.
				throw new XAException( XAException.XA_RBROLLBACK );
			}
			finally
			{
				forget( xid );
			}
		}
	}


	public synchronized boolean isSameRM( XAResource xaRes )
	throws XAException
	{
		// Two resource managers are equal if they produce equivalent
		// connection (i.e. same database, same user). If the two are
		// equivalent they would share a transaction by joining.
		if ( xaRes == null || ! ( xaRes instanceof XAConnectionImpl ) )
			return false;
		if ( _resManager.equals( ( (XAConnectionImpl) xaRes )._resManager ) )
			return true;
		return false;
	}


	public synchronized boolean setTransactionTimeout( int seconds )
	throws XAException
	{
		if ( seconds < 0 )
			throw new XAException( XAException.XAER_INVAL );
		// Zero resets to the default for all transactions.
		if ( seconds == 0 )
			seconds = _resManager.getTransactionTimeout();
		// If a transaction has started, change it's timeout to the new value.
		if ( _txConn != null )
		{
			_txConn.timeout = _txConn.started + ( seconds * 1000 );
			return true;
		}
		return false;
	}


	public int getTransactionTimeout()
	{
		long timeout;

		if ( _txConn == null )
			return 0;
		return (int) ( _txConn.timeout - _txConn.started ) / 1000;
	}


	/*
	 * Returns true if this connection is inside a global transaction.
	 * If the connection is inside a global transaction it will not
	 * allow commit/rollback directly from the {@link
	 * java.sql.Connection} interface.
	 */
	boolean insideGlobalTx()
	{
		return ( _txConn != null );
	}

	/*
	 * Called to obtain the underlying connections. If this connection
	 * is part of a transaction, the transction's underlying connection
	 * is returned, or an exception is thrown if the connection was
	 * terminated due to timeout. If this connection is not part of a
	 * transaction, a non-transactional connection is returned.
	 *
	 * @param clientId The {@link ClientConnection} identifier
	 */
	Connection getUnderlying( int clientId )
	throws SQLException
	{
		// If we were notified of the client closing, or have been
		// requested to have a new client connection since then,
		// the client id will not match to that of the caller.
		// We use that to decide that the caller has been closed.
		if ( clientId != _clientId )
			throw new SQLException( "This application connection has been closed" );

		if ( _txConn != null )
		{
			if ( _txConn.timedOut )
				throw new SQLException( "The transaction has timed out and has been rolledback and closed" );
			if ( _txConn.conn == null )
				throw new SQLException( "The transaction has been terminated and this connection has been closed" );
			return _txConn.conn;
		}
		if ( _underlying == null )
		{
			_underlying = _resManager.newConnection();
			_underlying.setAutoCommit( true );
		}
		return _underlying;
	}


}