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JDBC Driver for the Firebird RDBMS
/*
* Firebird Open Source J2ee connector - jdbc driver
*
* Distributable under LGPL license.
* You may obtain a copy of the License at http://www.gnu.org/copyleft/lgpl.html
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* LGPL License for more details.
*
* This file was created by members of the firebird development team.
* All individual contributions remain the Copyright (C) of those
* individuals. Contributors to this file are either listed here or
* can be obtained from a CVS history command.
*
* All rights reserved.
*/
package org.firebirdsql.pool;
import java.sql.SQLException;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Iterator;
import org.firebirdsql.jdbc.FBSQLException;
import org.firebirdsql.logging.Logger;
import org.firebirdsql.util.SQLExceptionChainBuilder;
/**
* Implementation of free connection queue.
*
* @author Roman Rokytskyy
*/
class PooledConnectionQueue {
private static final boolean LOG_DEBUG_INFO = PoolDebugConfiguration.LOG_DEBUG_INFO;
private static final boolean SHOW_STACK_ON_BLOCK = PoolDebugConfiguration.SHOW_TRACE;
private static final boolean SHOW_STACK_ON_ALLOCATION = PoolDebugConfiguration.SHOW_TRACE;
private PooledConnectionManager connectionManager;
private Logger logger;
private ConnectionPoolConfiguration configuration;
private Object key;
private String queueName;
private int blockingTimeout;
private int size;
private BlockingStack stack = new BlockingStack();
private boolean blocked;
private Object takeMutex = new Object();
private IdleRemover idleRemover;
private int totalConnections;
private HashSet workingConnections = new HashSet();
private HashSet workingConnectionsToClose = new HashSet();
private HashMap connectionIdleTime = new HashMap();
/**
* Create instance of this queue.
*
* @param connectionManager instance of {@link PooledConnectionManager}.
* @param logger instance of {@link Logger}.
* @param configuration instance of {@link Configuration}.
* @param queueName name of this queue.
*/
private PooledConnectionQueue(PooledConnectionManager connectionManager,
Logger logger, ConnectionPoolConfiguration configuration,
String queueName)
{
this.connectionManager = connectionManager;
this.logger = logger;
this.configuration = configuration;
this.queueName = queueName;
this.blockingTimeout = configuration.getBlockingTimeout();
}
/**
* Create instance of this queue for the specified user name and password.
*
* @param connectionManager instance of {@link PooledConnectionManager}.
* @param logger instance of {@link Logger}.
* @param configuration instance of {@link ConnectionPoolConfiguration}.
* @param queueName name of this queue.
* @param key Key used for this instance
*/
public PooledConnectionQueue(PooledConnectionManager connectionManager,
Logger logger, ConnectionPoolConfiguration configuration,
String queueName, Object key)
{
this(connectionManager, logger, configuration, queueName);
this.key = key;
}
/**
* Get logger for this instance. By default all log messages belong to
* this class. Subclasses can override this behavior.
*
* @return instance of {@link Logger}.
*/
protected Logger getLogger() {
return logger;
}
private ConnectionPoolConfiguration getConfiguration() {
return configuration;
}
/**
* Get size of this queue. This method can be used to check how many
* free connections is left.
*
* @return size of this queue.
*/
public int size() {
return size;
}
/**
* Get total number of physical connections opened to the database.
*
* @return total number of physical connections opened to the
* database.
*/
public int totalSize() {
return totalConnections;
}
/**
* Get number of working connections.
*
* @return number for working connections.
*/
public int workingSize() {
return workingConnections.size();
}
/**
* Start this queue.
*
* @throws SQLException if initial number of connections
* could not be created.
*/
public void start() throws SQLException {
for (int i = 0; i < getConfiguration().getMinPoolSize(); i++) {
try {
addConnection(stack);
} catch (InterruptedException iex) {
throw new SQLException("Could not start connection queue.");
}
}
idleRemover = new IdleRemover();
Thread t = new Thread(idleRemover, "Pool " + queueName + " idleRemover");
t.setDaemon(true);
t.start();
}
/**
* Restart this queue.
*/
public synchronized void restart()
{
// flag working connections for deallocation when returned to the queue.
workingConnectionsToClose.addAll(workingConnections);
// close all free connections
while (size() > 0)
try {
PooledObject connection = take();
if (connection.isValid()) {
connection.deallocate();
physicalConnectionDeallocated(connection);
}
} catch (SQLException ex) {
if (getLogger() != null)
getLogger().warn("Could not close connection.", ex);
}
//Create enough connections to restore the queue to MinPoolSize.
while (totalSize() < getConfiguration().getMinPoolSize())
try {
addConnection(stack);
}
catch (Exception e)
{
if (getLogger() != null)
getLogger().warn("Could not add connection.", e);
}
}
/**
* Shutdown this queue.
*/
public void shutdown() {
try {
// close all working connections.
Iterator iter = workingConnections.iterator();
while (iter.hasNext()) {
PooledObject item = (PooledObject)iter.next();
if (item.isValid())
item.deallocate();
}
// close all free connections
while (size() > 0)
try {
PooledObject item = (PooledObject)take();
if (item.isValid())
item.deallocate();
} catch (SQLException ex) {
if (getLogger() != null)
getLogger().warn("Could not close connection.", ex);
}
totalConnections = 0;
workingConnections.clear();
workingConnectionsToClose.clear();
} finally {
if (idleRemover != null)
idleRemover.stop();
idleRemover = null;
}
}
/**
* Check if {@link #take()} method can keep blocking.
*
* @param startTime time when the method was entered.
*
* @return true if method can keep blocking.
*/
private boolean keepBlocking(long startTime) {
return System.currentTimeMillis() - startTime < blockingTimeout;
}
/**
* Destroy connection and restore the balance of connections in the pool.
*
* @param connection connection to destroy
*/
public void destroyConnection(PooledObject connection) {
connection.deallocate();
totalConnections--;
}
/**
* Notify queue that a physical connection was deallocated.
*
* @param connection connection that was deallocated.
*/
public synchronized void physicalConnectionDeallocated(PooledObject connection) {
totalConnections--;
connectionIdleTime.remove(connection);
workingConnections.remove(connection);
}
/**
* Put connection to this queue.
*
* @param connection free pooled connection.
*
* @throws SQLException if connection cannot be added to this
* queue.
*/
public void put(PooledObject connection) throws SQLException {
try {
if (blocked && getLogger() != null)
getLogger().warn("Pool " + queueName + " will be unblocked");
if (getConfiguration().isPooling()) {
if (workingConnectionsToClose.remove(connection)) {
connection.deallocate();
physicalConnectionDeallocated(connection);
addConnection(stack);
}
else {
stack.push(connection);
connection.setInPool(true);
// save timestamp when connection was returned to queue
connectionIdleTime.put(
connection, new Long(System.currentTimeMillis()));
size++;
}
} else {
connectionIdleTime.remove(connection);
}
blocked = false;
workingConnections.remove(connection);
// deallocate connection if pooling is not enabled.
if (!getConfiguration().isPooling())
destroyConnection(connection);
if (LOG_DEBUG_INFO && getLogger() != null)
getLogger().debug("Thread "
+ Thread.currentThread().getName()
+ " released connection.");
} catch (InterruptedException iex) {
if (getLogger() != null)
getLogger().warn("Thread "
+ Thread.currentThread().getName()
+ " was interrupted.",
iex);
connection.deallocate();
}
}
/**
* Take pooled connection from this queue. This method will block
* until free and valid connection is available.
*
* @return free instance of {@link FBPooledConnection}.
*
* @throws SQLException if no free connection was available and
* waiting thread was interruped while waiting for a new free
* connection.
*/
public PooledObject take() throws SQLException {
long startTime = System.currentTimeMillis();
if (LOG_DEBUG_INFO && getLogger() != null)
getLogger().debug(
"Thread "
+ Thread.currentThread().getName()
+ " wants to take connection.");
PooledObject result = null;
// TODO Pending exceptions are only thrown on timeout, is that correct?
SQLExceptionChainBuilder pendingExceptions = new SQLExceptionChainBuilder();
try {
synchronized(takeMutex) {
if (stack.isEmpty()) {
while (result == null) {
if (!keepBlocking(startTime)) {
String message = "Could not obtain connection during " +
"blocking timeout (" + blockingTimeout + " ms)";
FBSQLException ex = new FBSQLException(message, FBSQLException.SQL_STATE_CONNECTION_FAILURE);
if (pendingExceptions.hasException()) {
ex.setNextException(pendingExceptions.getException());
}
throw ex;
};
boolean connectionAdded = false;
try {
connectionAdded = addConnection(stack);
} catch (SQLException sqlex) {
if (getLogger() != null)
getLogger().warn(
"Could not create connection."
+ sqlex.getMessage());
// could not add connection... bad luck
// let's wait more
if (!pendingExceptions.hasException()) {
pendingExceptions.append(sqlex);
} else if (pendingExceptions.getException().getErrorCode() != sqlex.getErrorCode()) {
pendingExceptions.append(sqlex);
}
}
if (!connectionAdded) {
String message =
"Pool "
+ queueName
+ " is empty and will block here."
+ " Thread "
+ Thread.currentThread().getName();
if (SHOW_STACK_ON_BLOCK) {
if (getLogger() != null)
getLogger().warn(message, new Exception());
} else {
if (getLogger() != null)
getLogger().warn(message);
}
blocked = true;
}
result = (PooledObject) stack.pop(
getConfiguration().getRetryInterval());
if (result == null && getLogger() != null)
getLogger().warn("No connection in pool. Thread " +
Thread.currentThread().getName());
else
if (result != null && !connectionAdded && getLogger() != null)
getLogger().info("Obtained connection. Thread " +
Thread.currentThread().getName());
}
} else {
result = (PooledObject)stack.pop();
}
}
} catch (InterruptedException iex) {
throw new SQLException(
"No free connection was available and "
+ "waiting thread was interrupted.");
}
size--;
workingConnections.add(result);
if (LOG_DEBUG_INFO && getLogger() != null) {
if (SHOW_STACK_ON_ALLOCATION)
getLogger().debug(
"Thread "+ Thread.currentThread().getName() +
" got connection.", new Exception());
else
getLogger().debug(
"Thread "+ Thread.currentThread().getName() +
" got connection.");
}
result.setInPool(false);
return result;
}
/**
* Open new connection to database.
*
* @return true if new physical connection was created,
* otherwise false.
*
* @throws SQLException if new connection cannot be opened.
* @throws InterruptedException if thread was interrupted.
*/
private boolean addConnection(BlockingStack queue)
throws SQLException, InterruptedException {
synchronized (this) {
if (LOG_DEBUG_INFO && getLogger() != null)
getLogger().debug(
"Trying to create connection, total connections "
+ totalConnections
+ ", max allowed "
+ getConfiguration().getMaxPoolSize());
boolean maximumCapacityReached =
getConfiguration().getMaxPoolSize() <= totalConnections &&
getConfiguration().getMaxPoolSize() != 0 &&
getConfiguration().isPooling();
if (maximumCapacityReached) {
if (LOG_DEBUG_INFO && getLogger() != null)
getLogger().debug("Was not able to add more connections.");
return false;
}
Object pooledConnection = connectionManager.allocateConnection(key);
if (LOG_DEBUG_INFO && getLogger() != null)
getLogger().debug(
"Thread "
+ Thread.currentThread().getName()
+ " created connection.");
queue.push(pooledConnection);
size++;
totalConnections++;
return true;
}
}
/**
* Release first connection in the queue if it was idle longer than idle
* timeout interval.
*
* @return true if method removed idle connection, otherwise
* false
*
* @throws SQLException if exception happened when releasing the connection.
*/
private boolean releaseNextIdleConnection() throws SQLException {
synchronized(takeMutex) {
if (totalSize() <= getConfiguration().getMinPoolSize())
return false;
PooledObject candidate = (PooledObject)stack.peek();
if (candidate == null)
return false;
Long lastUsageTime = (Long)connectionIdleTime.get(candidate);
if (lastUsageTime == null)
return false;
long idleTime = System.currentTimeMillis() - lastUsageTime.longValue();
if (idleTime < getConfiguration().getMaxIdleTime())
return false;
try {
take().deallocate();
} finally {
workingConnections.remove(candidate);
connectionIdleTime.remove(candidate);
totalConnections--;
}
return true;
}
}
/**
* Implementation of {@link Runnable} interface responsible for removing
* idle connections.
*/
private class IdleRemover implements Runnable {
private boolean running;
public IdleRemover() {
running = true;
}
public void stop() {
running = false;
}
public void run() {
while (running) {
try {
while(releaseNextIdleConnection()) {
// do nothing, we already released connection
// next one, please :)
}
} catch(SQLException ex) {
// do nothing, we hardly can handle this situation
}
try {
int idleTimeout = getConfiguration().getMaxIdleTime();
int maxConnections = getConfiguration().getMaxPoolSize();
if (maxConnections < 1)
maxConnections = 1;
Thread.sleep(idleTimeout / maxConnections);
} catch(InterruptedException ex) {
// do nothing
}
}
}
}
}
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