/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.tomcat.jdbc.pool;
import java.lang.reflect.Constructor;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Proxy;
import java.sql.Connection;
import java.sql.SQLException;
import java.util.ConcurrentModificationException;
import java.util.Iterator;
import java.util.concurrent.ArrayBlockingQueue;
import java.util.concurrent.BlockingQueue;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.Future;
import java.util.concurrent.LinkedBlockingQueue;
import java.util.concurrent.ThreadPoolExecutor;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.TimeoutException;
import java.util.concurrent.atomic.AtomicBoolean;
import java.util.concurrent.atomic.AtomicInteger;
import org.apache.juli.logging.Log;
import org.apache.juli.logging.LogFactory;
/**
* Implementation of simple connection pool.
* The ConnectionPool uses a {@link PoolProperties} object for storing all the meta information about the connection pool.
* As the underlying implementation, the connection pool uses {@link java.util.concurrent.BlockingQueue} to store active and idle connections.
* A custom implementation of a fair {@link FairBlockingQueue} blocking queue is provided with the connection pool itself.
* @author Filip Hanik
* @version 1.0
*/
public class ConnectionPool {
/**
* Prefix type for JMX registration
*/
public static final String POOL_JMX_TYPE_PREFIX = "tomcat.jdbc:type=";
/**
* Logger
*/
private static final Log log = LogFactory.getLog(ConnectionPool.class);
//===============================================================================
// INSTANCE/QUICK ACCESS VARIABLE
//===============================================================================
/**
* Carries the size of the pool, instead of relying on a queue implementation
* that usually iterates over to get an exact count
*/
private AtomicInteger size = new AtomicInteger(0);
/**
* All the information about the connection pool
* These are the properties the pool got instantiated with
*/
private PoolConfiguration poolProperties;
/**
* Contains all the connections that are in use
* TODO - this shouldn't be a blocking queue, simply a list to hold our objects
*/
private BlockingQueue<PooledConnection> busy;
/**
* Contains all the idle connections
*/
private BlockingQueue<PooledConnection> idle;
/**
* The thread that is responsible for checking abandoned and idle threads
*/
private volatile PoolCleaner poolCleaner;
/**
* Pool closed flag
*/
private volatile boolean closed = false;
/**
* Since newProxyInstance performs the same operation, over and over
* again, it is much more optimized if we simply store the constructor ourselves.
*/
private Constructor<?> proxyClassConstructor;
/**
* Executor service used to cancel Futures
*/
private ThreadPoolExecutor cancellator = new ThreadPoolExecutor(0,1,1000,TimeUnit.MILLISECONDS,new LinkedBlockingQueue<Runnable>());
/**
* reference to the JMX mbean
*/
protected org.apache.tomcat.jdbc.pool.jmx.ConnectionPool jmxPool = null;
/**
* counter to track how many threads are waiting for a connection
*/
private AtomicInteger waitcount = new AtomicInteger(0);
//===============================================================================
// PUBLIC METHODS
//===============================================================================
/**
* Instantiate a connection pool. This will create connections if initialSize is larger than 0.
* The {@link PoolProperties} should not be reused for another connection pool.
* @param prop PoolProperties - all the properties for this connection pool
* @throws SQLException
*/
public ConnectionPool(PoolConfiguration prop) throws SQLException {
//setup quick access variables and pools
init(prop);
}
/**
* Retrieves a Connection future. If a connection is not available, one can block using future.get()
* until a connection has become available.
* If a connection is not retrieved, the Future must be cancelled in order for the connection to be returned
* to the pool.
* @return a Future containing a reference to the connection or the future connection
* @throws SQLException
*/
public Future<Connection> getConnectionAsync() throws SQLException {
try {
PooledConnection pc = borrowConnection(0, null, null);
if (pc!=null) {
return new ConnectionFuture(pc);
}
}catch (SQLException x) {
if (x.getMessage().indexOf("NoWait")<0) {
throw x;
}
}
//we can only retrieve a future if the underlying queue supports it.
if (idle instanceof FairBlockingQueue<?>) {
Future<PooledConnection> pcf = ((FairBlockingQueue<PooledConnection>)idle).pollAsync();
return new ConnectionFuture(pcf);
} else if (idle instanceof MultiLockFairBlockingQueue<?>) {
Future<PooledConnection> pcf = ((MultiLockFairBlockingQueue<PooledConnection>)idle).pollAsync();
return new ConnectionFuture(pcf);
} else {
throw new SQLException("Connection pool is misconfigured, doesn't support async retrieval. Set the 'fair' property to 'true'");
}
}
/**
* Borrows a connection from the pool. If a connection is available (in the idle queue) or the pool has not reached
* {@link PoolProperties#maxActive maxActive} connections a connection is returned immediately.
* If no connection is available, the pool will attempt to fetch a connection for {@link PoolProperties#maxWait maxWait} milliseconds.
* @return Connection - a java.sql.Connection/javax.sql.PooledConnection reflection proxy, wrapping the underlying object.
* @throws SQLException - if the wait times out or a failure occurs creating a connection
*/
public Connection getConnection() throws SQLException {
//check out a connection
PooledConnection con = borrowConnection(-1,null,null);
return setupConnection(con);
}
/**
* Borrows a connection from the pool. If a connection is available (in the
* idle queue) or the pool has not reached {@link PoolProperties#maxActive
* maxActive} connections a connection is returned immediately. If no
* connection is available, the pool will attempt to fetch a connection for
* {@link PoolProperties#maxWait maxWait} milliseconds.
*
* @return Connection - a java.sql.Connection/javax.sql.PooledConnection
* reflection proxy, wrapping the underlying object.
* @throws SQLException
* - if the wait times out or a failure occurs creating a
* connection
*/
public Connection getConnection(String username, String password) throws SQLException {
// check out a connection
PooledConnection con = borrowConnection(-1, username, password);
return setupConnection(con);
}
/**
* Returns the name of this pool
* @return String - the name of the pool
*/
public String getName() {
return getPoolProperties().getPoolName();
}
/**
* Return the number of threads waiting for a connection
* @return number of threads waiting for a connection
*/
public int getWaitCount() {
return waitcount.get();
}
/**
* Returns the pool properties associated with this connection pool
* @return PoolProperties
*
*/
public PoolConfiguration getPoolProperties() {
return this.poolProperties;
}
/**
* Returns the total size of this pool, this includes both busy and idle connections
* @return int - number of established connections to the database
*/
public int getSize() {
return size.get();
}
/**
* Returns the number of connections that are in use
* @return int - number of established connections that are being used by the application
*/
public int getActive() {
return busy.size();
}
/**
* Returns the number of idle connections
* @return int - number of established connections not being used
*/
public int getIdle() {
return idle.size();
}
/**
* Returns true if {@link #close close} has been called, and the connection pool is unusable
* @return boolean
*/
public boolean isClosed() {
return this.closed;
}
//===============================================================================
// PROTECTED METHODS
//===============================================================================
/**
* configures a pooled connection as a proxy.
* This Proxy implements {@link java.sql.Connection} and {@link javax.sql.PooledConnection} interfaces.
* All calls on {@link java.sql.Connection} methods will be propagated down to the actual JDBC connection except for the
* {@link java.sql.Connection#close()} method.
* @param con a {@link PooledConnection} to wrap in a Proxy
* @return a {@link java.sql.Connection} object wrapping a pooled connection.
* @throws SQLException if an interceptor can't be configured, if the proxy can't be instantiated
*/
protected Connection setupConnection(PooledConnection con) throws SQLException {
//fetch previously cached interceptor proxy - one per connection
JdbcInterceptor handler = con.getHandler();
if (handler==null) {
//build the proxy handler
handler = new ProxyConnection(this,con,getPoolProperties().isUseEquals());
//set up the interceptor chain
PoolProperties.InterceptorDefinition[] proxies = getPoolProperties().getJdbcInterceptorsAsArray();
for (int i=proxies.length-1; i>=0; i--) {
try {
//create a new instance
JdbcInterceptor interceptor = proxies[i].getInterceptorClass().newInstance();
//configure properties
interceptor.setProperties(proxies[i].getProperties());
//setup the chain
interceptor.setNext(handler);
//call reset
interceptor.reset(this, con);
//configure the last one to be held by the connection
handler = interceptor;
}catch(Exception x) {
SQLException sx = new SQLException("Unable to instantiate interceptor chain.");
sx.initCause(x);
throw sx;
}
}
//cache handler for the next iteration
con.setHandler(handler);
} else {
JdbcInterceptor next = handler;
//we have a cached handler, reset it
while (next!=null) {
next.reset(this, con);
next = next.getNext();
}
}
try {
getProxyConstructor(con.getXAConnection() != null);
//create the proxy
//TODO possible optimization, keep track if this connection was returned properly, and don't generate a new facade
Connection connection = (Connection)proxyClassConstructor.newInstance(new Object[] { handler });
//return the connection
return connection;
}catch (Exception x) {
SQLException s = new SQLException();
s.initCause(x);
throw s;
}
}
/**
* Creates and caches a {@link java.lang.reflect.Constructor} used to instantiate the proxy object.
* We cache this, since the creation of a constructor is fairly slow.
* @return constructor used to instantiate the wrapper object
* @throws NoSuchMethodException
*/
public Constructor<?> getProxyConstructor(boolean xa) throws NoSuchMethodException {
//cache the constructor
if (proxyClassConstructor == null ) {
Class<?> proxyClass = xa ?
Proxy.getProxyClass(ConnectionPool.class.getClassLoader(), new Class[] {java.sql.Connection.class,javax.sql.PooledConnection.class, javax.sql.XAConnection.class}) :
Proxy.getProxyClass(ConnectionPool.class.getClassLoader(), new Class[] {java.sql.Connection.class,javax.sql.PooledConnection.class});
proxyClassConstructor = proxyClass.getConstructor(new Class[] { InvocationHandler.class });
}
return proxyClassConstructor;
}
/**
* Closes the pool and all disconnects all idle connections
* Active connections will be closed upon the {@link java.sql.Connection#close close} method is called
* on the underlying connection instead of being returned to the pool
* @param force - true to even close the active connections
*/
protected void close(boolean force) {
//are we already closed
if (this.closed) return;
//prevent other threads from entering
this.closed = true;
//stop background thread
if (poolCleaner!=null) {
poolCleaner.stopRunning();
}
/* release all idle connections */
BlockingQueue<PooledConnection> pool = (idle.size()>0)?idle:(force?busy:idle);
while (pool.size()>0) {
try {
//retrieve the next connection
PooledConnection con = pool.poll(1000, TimeUnit.MILLISECONDS);
//close it and retrieve the next one, if one is available
while (con != null) {
//close the connection
if (pool==idle)
release(con);
else
abandon(con);
con = pool.poll(1000, TimeUnit.MILLISECONDS);
} //while
} catch (InterruptedException ex) {
Thread.interrupted();
}
if (pool.size()==0 && force && pool!=busy) pool = busy;
}
if (this.getPoolProperties().isJmxEnabled()) this.jmxPool = null;
PoolProperties.InterceptorDefinition[] proxies = getPoolProperties().getJdbcInterceptorsAsArray();
for (int i=0; i<proxies.length; i++) {
try {
proxies[i].getInterceptorClass().newInstance().poolClosed(this);
}catch (Exception x) {
log.debug("Unable to inform interceptor of pool closure.",x);
}
}
} //closePool
/**
* Initialize the connection pool - called from the constructor
* @param properties PoolProperties - properties used to initialize the pool with
* @throws SQLException if initialization fails
*/
protected void init(PoolConfiguration properties) throws SQLException {
poolProperties = properties;
//make space for 10 extra in case we flow over a bit
busy = new ArrayBlockingQueue<PooledConnection>(properties.getMaxActive(),false);
//busy = new FairBlockingQueue<PooledConnection>();
//make space for 10 extra in case we flow over a bit
if (properties.isFairQueue()) {
idle = new FairBlockingQueue<PooledConnection>();
//idle = new MultiLockFairBlockingQueue<PooledConnection>();
} else {
idle = new ArrayBlockingQueue<PooledConnection>(properties.getMaxActive(),properties.isFairQueue());
}
//if the evictor thread is supposed to run, start it now
if (properties.isPoolSweeperEnabled()) {
poolCleaner = new PoolCleaner("[Pool-Cleaner]:" + properties.getName(), this, properties.getTimeBetweenEvictionRunsMillis());
poolCleaner.start();
} //end if
//make sure the pool is properly configured
if (properties.getMaxActive()<1) {
log.warn("maxActive is smaller than 1, setting maxActive to: "+PoolProperties.DEFAULT_MAX_ACTIVE);
properties.setMaxActive(PoolProperties.DEFAULT_MAX_ACTIVE);
}
if (properties.getMaxActive()<properties.getInitialSize()) {
log.warn("initialSize is larger than maxActive, setting initialSize to: "+properties.getMaxActive());
properties.setInitialSize(properties.getMaxActive());
}
if (properties.getMinIdle()>properties.getMaxActive()) {
log.warn("minIdle is larger than maxActive, setting minIdle to: "+properties.getMaxActive());
properties.setMinIdle(properties.getMaxActive());
}
if (properties.getMaxIdle()>properties.getMaxActive()) {
log.warn("maxIdle is larger than maxActive, setting maxIdle to: "+properties.getMaxActive());
properties.setMaxIdle(properties.getMaxActive());
}
if (properties.getMaxIdle()<properties.getMinIdle()) {
log.warn("maxIdle is smaller than minIdle, setting maxIdle to: "+properties.getMinIdle());
properties.setMaxIdle(properties.getMinIdle());
}
//create JMX MBean
if (this.getPoolProperties().isJmxEnabled()) createMBean();
//Parse and create an initial set of interceptors. Letting them know the pool has started.
//These interceptors will not get any connection.
PoolProperties.InterceptorDefinition[] proxies = getPoolProperties().getJdbcInterceptorsAsArray();
for (int i=0; i<proxies.length; i++) {
try {
if (log.isDebugEnabled()) {
log.debug("Creating interceptor instance of class:"+proxies[i].getInterceptorClass());
}
JdbcInterceptor interceptor = proxies[i].getInterceptorClass().newInstance();
interceptor.setProperties(proxies[i].getProperties());
interceptor.poolStarted(this);
}catch (Exception x) {
log.error("Unable to inform interceptor of pool start.",x);
if (jmxPool!=null) jmxPool.notify(org.apache.tomcat.jdbc.pool.jmx.ConnectionPool.NOTIFY_INIT, getStackTrace(x));
close(true);
SQLException ex = new SQLException();
ex.initCause(x);
throw ex;
}
}
//initialize the pool with its initial set of members
PooledConnection[] initialPool = new PooledConnection[poolProperties.getInitialSize()];
try {
for (int i = 0; i < initialPool.length; i++) {
initialPool[i] = this.borrowConnection(0, null, null); //don't wait, should be no contention
} //for
} catch (SQLException x) {
if (jmxPool!=null) jmxPool.notify(org.apache.tomcat.jdbc.pool.jmx.ConnectionPool.NOTIFY_INIT, getStackTrace(x));
close(true);
throw x;
} finally {
//return the members as idle to the pool
for (int i = 0; i < initialPool.length; i++) {
if (initialPool[i] != null) {
try {this.returnConnection(initialPool[i]);}catch(Exception x){/*NOOP*/}
} //end if
} //for
} //catch
closed = false;
}
//===============================================================================
// CONNECTION POOLING IMPL LOGIC
//===============================================================================
/**
* thread safe way to abandon a connection
* signals a connection to be abandoned.
* this will disconnect the connection, and log the stack trace if logAbanded=true
* @param con PooledConnection
*/
protected void abandon(PooledConnection con) {
if (con == null)
return;
try {
con.lock();
String trace = con.getStackTrace();
if (getPoolProperties().isLogAbandoned()) {
log.warn("Connection has been abandoned " + con + ":" + trace);
}
if (jmxPool!=null) {
jmxPool.notify(org.apache.tomcat.jdbc.pool.jmx.ConnectionPool.NOTIFY_ABANDON, trace);
}
//release the connection
release(con);
} finally {
con.unlock();
}
}
/**
* thread safe way to abandon a connection
* signals a connection to be abandoned.
* this will disconnect the connection, and log the stack trace if logAbanded=true
* @param con PooledConnection
*/
protected void suspect(PooledConnection con) {
if (con == null)
return;
if (con.isSuspect())
return;
try {
con.lock();
String trace = con.getStackTrace();
if (getPoolProperties().isLogAbandoned()) {
log.warn("Connection has been marked suspect, possibly abandoned " + con + "["+(System.currentTimeMillis()-con.getTimestamp())+" ms.]:" + trace);
}
if (jmxPool!=null) {
jmxPool.notify(org.apache.tomcat.jdbc.pool.jmx.ConnectionPool.SUSPECT_ABANDONED_NOTIFICATION, trace);
}
con.setSuspect(true);
} finally {
con.unlock();
}
}
/**
* thread safe way to release a connection
* @param con PooledConnection
*/
protected void release(PooledConnection con) {
if (con == null)
return;
try {
con.lock();
if (con.release()) {
//counter only decremented once
size.addAndGet(-1);
con.setHandler(null);
}
} finally {
con.unlock();
}
// we've asynchronously reduced the number of connections
// we could have threads stuck in idle.poll(timeout) that will never be
// notified
if (waitcount.get() > 0) {
idle.offer(create(true));
}
}
/**
* Thread safe way to retrieve a connection from the pool
* @param wait - time to wait, overrides the maxWait from the properties,
* set to -1 if you wish to use maxWait, 0 if you wish no wait time.
* @return PooledConnection
* @throws SQLException
*/
private PooledConnection borrowConnection(int wait, String username, String password) throws SQLException {
if (isClosed()) {
throw new SQLException("Connection pool closed.");
} //end if
//get the current time stamp
long now = System.currentTimeMillis();
//see if there is one available immediately
PooledConnection con = idle.poll();
while (true) {
if (con!=null) {
//configure the connection and return it
PooledConnection result = borrowConnection(now, con, username, password);
//null should never be returned, but was in a previous impl.
if (result!=null) return result;
}
//if we get here, see if we need to create one
//this is not 100% accurate since it doesn't use a shared
//atomic variable - a connection can become idle while we are creating
//a new connection
if (size.get() < getPoolProperties().getMaxActive()) {
//atomic duplicate check
if (size.addAndGet(1) > getPoolProperties().getMaxActive()) {
//if we got here, two threads passed through the first if
size.decrementAndGet();
} else {
//create a connection, we're below the limit
return createConnection(now, con, username, password);
}
} //end if
//calculate wait time for this iteration
long maxWait = wait;
//if the passed in wait time is -1, means we should use the pool property value
if (wait==-1) {
maxWait = (getPoolProperties().getMaxWait()<=0)?Long.MAX_VALUE:getPoolProperties().getMaxWait();
}
long timetowait = Math.max(0, maxWait - (System.currentTimeMillis() - now));
waitcount.incrementAndGet();
try {
//retrieve an existing connection
con = idle.poll(timetowait, TimeUnit.MILLISECONDS);
} catch (InterruptedException ex) {
Thread.interrupted();//clear the flag, and bail out
SQLException sx = new SQLException("Pool wait interrupted.");
sx.initCause(ex);
throw sx;
} finally {
waitcount.decrementAndGet();
}
if (maxWait==0 && con == null) { //no wait, return one if we have one
throw new SQLException("[" + Thread.currentThread().getName()+"] " +
"NoWait: Pool empty. Unable to fetch a connection, none available["+busy.size()+" in use].");
}
//we didn't get a connection, lets see if we timed out
if (con == null) {
if ((System.currentTimeMillis() - now) >= maxWait) {
throw new SQLException("[" + Thread.currentThread().getName()+"] " +
"Timeout: Pool empty. Unable to fetch a connection in " + (maxWait / 1000) +
" seconds, none available[size:"+size.get() +"; busy:"+busy.size()+"; idle:"+idle.size()+"; lastwait:"+timetowait+"].");
} else {
//no timeout, lets try again
continue;
}
}
} //while
}
/**
* Creates a JDBC connection and tries to connect to the database.
* @param now timestamp of when this was called
* @param notUsed Argument not used
* @return a PooledConnection that has been connected
* @throws SQLException
*/
protected PooledConnection createConnection(long now, PooledConnection notUsed, String username, String password) throws SQLException {
//no connections where available we'll create one
PooledConnection con = create(false);
if (username!=null) con.getAttributes().put(con.PROP_USER, username);
if (password!=null) con.getAttributes().put(con.PROP_PASSWORD, password);
boolean error = false;
try {
//connect and validate the connection
con.lock();
con.connect();
if (con.validate(PooledConnection.VALIDATE_INIT)) {
//no need to lock a new one, its not contented
con.setTimestamp(now);
if (getPoolProperties().isLogAbandoned()) {
con.setStackTrace(getThreadDump());
}
if (!busy.offer(con)) {
log.debug("Connection doesn't fit into busy array, connection will not be traceable.");
}
return con;
} else {
//validation failed, make sure we disconnect
//and clean up
error =true;
} //end if
} catch (Exception e) {
error = true;
if (log.isDebugEnabled())
log.debug("Unable to create a new JDBC connection.", e);
if (e instanceof SQLException) {
throw (SQLException)e;
} else {
SQLException ex = new SQLException(e.getMessage());
ex.initCause(e);
throw ex;
}
} finally {
// con can never be null here
if (error ) {
release(con);
}
con.unlock();
}//catch
return null;
}
/**
* Validates and configures a previously idle connection
* @param now - timestamp
* @param con - the connection to validate and configure
* @return con
* @throws SQLException if a validation error happens
*/
protected PooledConnection borrowConnection(long now, PooledConnection con, String username, String password) throws SQLException {
//we have a connection, lets set it up
//flag to see if we need to nullify
boolean setToNull = false;
try {
con.lock();
boolean usercheck = con.checkUser(username, password);
if (con.isReleased()) {
return null;
}
if (!con.isDiscarded() && !con.isInitialized()) {
//attempt to connect
con.connect();
}
if (usercheck) {
if ((!con.isDiscarded()) && con.validate(PooledConnection.VALIDATE_BORROW)) {
//set the timestamp
con.setTimestamp(now);
if (getPoolProperties().isLogAbandoned()) {
//set the stack trace for this pool
con.setStackTrace(getThreadDump());
}
if (!busy.offer(con)) {
log.debug("Connection doesn't fit into busy array, connection will not be traceable.");
}
return con;
}
}
//if we reached here, that means the connection
//is either has another principal, is discarded or validation failed.
//we will make one more attempt
//in order to guarantee that the thread that just acquired
//the connection shouldn't have to poll again.
try {
con.reconnect();
if (con.validate(PooledConnection.VALIDATE_INIT)) {
//set the timestamp
con.setTimestamp(now);
if (getPoolProperties().isLogAbandoned()) {
//set the stack trace for this pool
con.setStackTrace(getThreadDump());
}
if (!busy.offer(con)) {
log.debug("Connection doesn't fit into busy array, connection will not be traceable.");
}
return con;
} else {
//validation failed.
release(con);
setToNull = true;
throw new SQLException("Failed to validate a newly established connection.");
}
} catch (Exception x) {
release(con);
setToNull = true;
if (x instanceof SQLException) {
throw (SQLException)x;
} else {
SQLException ex = new SQLException(x.getMessage());
ex.initCause(x);
throw ex;
}
}
} finally {
con.unlock();
if (setToNull) {
con = null;
}
}
}
/**
* Determines if a connection should be closed upon return to the pool.
* @param con - the connection
* @param action - the validation action that should be performed
* @return true if the connection should be closed
*/
protected boolean shouldClose(PooledConnection con, int action) {
if (con.isDiscarded()) return true;
if (isClosed()) return true;
if (!con.validate(action)) return true;
if (getPoolProperties().getMaxAge()>0 ) {
return (System.currentTimeMillis()-con.getLastConnected()) > getPoolProperties().getMaxAge();
} else {
return false;
}
}
/**
* Returns a connection to the pool
* If the pool is closed, the connection will be released
* If the connection is not part of the busy queue, it will be released.
* If {@link PoolProperties#testOnReturn} is set to true it will be validated
* @param con PooledConnection to be returned to the pool
*/
protected void returnConnection(PooledConnection con) {
if (isClosed()) {
//if the connection pool is closed
//close the connection instead of returning it
release(con);
return;
} //end if
if (con != null) {
try {
con.lock();
if (busy.remove(con)) {
if (!shouldClose(con,PooledConnection.VALIDATE_RETURN)) {
con.setStackTrace(null);
con.setTimestamp(System.currentTimeMillis());
if (((idle.size()>=poolProperties.getMaxIdle()) && !poolProperties.isPoolSweeperEnabled()) || (!idle.offer(con))) {
if (log.isDebugEnabled()) {
log.debug("Connection ["+con+"] will be closed and not returned to the pool, idle["+idle.size()+"]>=maxIdle["+poolProperties.getMaxIdle()+"] idle.offer failed.");
}
release(con);
}
} else {
if (log.isDebugEnabled()) {
log.debug("Connection ["+con+"] will be closed and not returned to the pool.");
}
release(con);
} //end if
} else {
if (log.isDebugEnabled()) {
log.debug("Connection ["+con+"] will be closed and not returned to the pool, busy.remove failed.");
}
release(con);
}
} finally {
con.unlock();
}
} //end if
} //checkIn
/**
* Determines if a connection should be abandoned based on
* {@link PoolProperties#abandonWhenPercentageFull} setting.
* @return true if the connection should be abandoned
*/
protected boolean shouldAbandon() {
if (poolProperties.getAbandonWhenPercentageFull()==0) return true;
float used = busy.size();
float max = poolProperties.getMaxActive();
float perc = poolProperties.getAbandonWhenPercentageFull();
return (used/max*100f)>=perc;
}
/**
* Iterates through all the busy connections and checks for connections that have timed out
*/
public void checkAbandoned() {
try {
if (busy.size()==0) return;
Iterator<PooledConnection> locked = busy.iterator();
int sto = getPoolProperties().getSuspectTimeout();
while (locked.hasNext()) {
PooledConnection con = locked.next();
boolean setToNull = false;
try {
con.lock();
//the con has been returned to the pool
//ignore it
if (idle.contains(con))
continue;
long time = con.getTimestamp();
long now = System.currentTimeMillis();
if (shouldAbandon() && (now - time) > con.getAbandonTimeout()) {
busy.remove(con);
abandon(con);
setToNull = true;
} else if (sto > 0 && (now - time) > (sto*1000)) {
suspect(con);
} else {
//do nothing
} //end if
} finally {
con.unlock();
if (setToNull)
con = null;
}
} //while
} catch (ConcurrentModificationException e) {
log.debug("checkAbandoned failed." ,e);
} catch (Exception e) {
log.warn("checkAbandoned failed, it will be retried.",e);
}
}
/**
* Iterates through the idle connections and resizes the idle pool based on parameters
* {@link PoolProperties#maxIdle}, {@link PoolProperties#minIdle}, {@link PoolProperties#minEvictableIdleTimeMillis}
*/
public void checkIdle() {
try {
if (idle.size()==0) return;
long now = System.currentTimeMillis();
Iterator<PooledConnection> unlocked = idle.iterator();
while ( (idle.size()>=getPoolProperties().getMinIdle()) && unlocked.hasNext()) {
PooledConnection con = unlocked.next();
boolean setToNull = false;
try {
con.lock();
//the con been taken out, we can't clean it up
if (busy.contains(con))
continue;
long time = con.getTimestamp();
if ((con.getReleaseTime()>0) && ((now - time) > con.getReleaseTime()) && (getSize()>getPoolProperties().getMinIdle())) {
release(con);
idle.remove(con);
setToNull = true;
} else {
//do nothing
} //end if
} finally {
con.unlock();
if (setToNull)
con = null;
}
} //while
} catch (ConcurrentModificationException e) {
log.debug("checkIdle failed." ,e);
} catch (Exception e) {
log.warn("checkIdle failed, it will be retried.",e);
}
}
/**
* Forces a validation of all idle connections if {@link PoolProperties#testWhileIdle} is set.
*/
public void testAllIdle() {
try {
if (idle.size()==0) return;
Iterator<PooledConnection> unlocked = idle.iterator();
while (unlocked.hasNext()) {
PooledConnection con = unlocked.next();
try {
con.lock();
//the con been taken out, we can't clean it up
if (busy.contains(con))
continue;
if (!con.validate(PooledConnection.VALIDATE_IDLE)) {
idle.remove(con);
release(con);
}
} finally {
con.unlock();
}
} //while
} catch (ConcurrentModificationException e) {
log.debug("testAllIdle failed." ,e);
} catch (Exception e) {
log.warn("testAllIdle failed, it will be retried.",e);
}
}
/**
* Creates a stack trace representing the existing thread's current state.
* @return a string object representing the current state.
* TODO investigate if we simply should store {@link java.lang.Thread#getStackTrace()} elements
*/
protected static String getThreadDump() {
Exception x = new Exception();
x.fillInStackTrace();
return getStackTrace(x);
}
/**
* Convert an exception into a String
* @param x - the throwable
* @return a string representing the stack trace
*/
public static String getStackTrace(Throwable x) {
if (x == null) {
return null;
} else {
java.io.ByteArrayOutputStream bout = new java.io.ByteArrayOutputStream();
java.io.PrintStream writer = new java.io.PrintStream(bout);
x.printStackTrace(writer);
String result = bout.toString();
return (x.getMessage()!=null && x.getMessage().length()>0)? x.getMessage()+";"+result:result;
} //end if
}
/**
* Create a new pooled connection object. Not connected nor validated.
* @return a pooled connection object
*/
protected PooledConnection create(boolean incrementCounter) {
if (incrementCounter) size.incrementAndGet();
PooledConnection con = new PooledConnection(getPoolProperties(), this);
return con;
}
/**
* Hook to perform final actions on a pooled connection object once it has been disconnected and will be discarded
* @param con
*/
protected void finalize(PooledConnection con) {
JdbcInterceptor handler = con.getHandler();
while (handler!=null) {
handler.reset(null, null);
handler=handler.getNext();
}
}
/**
* Hook to perform final actions on a pooled connection object once it has been disconnected and will be discarded
* @param con
*/
protected void disconnectEvent(PooledConnection con, boolean finalizing) {
JdbcInterceptor handler = con.getHandler();
while (handler!=null) {
handler.disconnected(this, con, finalizing);
handler=handler.getNext();
}
}
/**
* Return the object that is potentially registered in JMX for notifications
* @return the object implementing the {@link org.apache.tomcat.jdbc.pool.jmx.ConnectionPoolMBean} interface
*/
public org.apache.tomcat.jdbc.pool.jmx.ConnectionPool getJmxPool() {
return jmxPool;
}
/**
* Create MBean object that can be registered.
*/
protected void createMBean() {
try {
jmxPool = new org.apache.tomcat.jdbc.pool.jmx.ConnectionPool(this);
} catch (Exception x) {
log.warn("Unable to start JMX integration for connection pool. Instance["+getName()+"] can't be monitored.",x);
}
}
/**
* Tread safe wrapper around a future for the regular queue
* This one retrieves the pooled connection object
* and performs the initialization according to
* interceptors and validation rules.
* This class is thread safe and is cancellable
* @author fhanik
*
*/
protected class ConnectionFuture implements Future<Connection>, Runnable {
Future<PooledConnection> pcFuture = null;
AtomicBoolean configured = new AtomicBoolean(false);
CountDownLatch latch = new CountDownLatch(1);
Connection result = null;
SQLException cause = null;
AtomicBoolean cancelled = new AtomicBoolean(false);
volatile PooledConnection pc = null;
public ConnectionFuture(Future<PooledConnection> pcf) {
this.pcFuture = pcf;
}
public ConnectionFuture(PooledConnection pc) throws SQLException {
this.pc = pc;
result = ConnectionPool.this.setupConnection(pc);
configured.set(true);
}
/**
* {@inheritDoc}
*/
public boolean cancel(boolean mayInterruptIfRunning) {
if (pc!=null) {
return false;
} else if ((!cancelled.get()) && cancelled.compareAndSet(false, true)) {
//cancel by retrieving the connection and returning it to the pool
ConnectionPool.this.cancellator.execute(this);
}
return true;
}
/**
* {@inheritDoc}
*/
public Connection get() throws InterruptedException, ExecutionException {
try {
return get(Long.MAX_VALUE, TimeUnit.MILLISECONDS);
}catch (TimeoutException x) {
throw new ExecutionException(x);
}
}
/**
* {@inheritDoc}
*/
public Connection get(long timeout, TimeUnit unit) throws InterruptedException, ExecutionException, TimeoutException {
PooledConnection pc = this.pc!=null?this.pc:pcFuture.get(timeout,unit);
if (pc!=null) {
if (result!=null) return result;
if (configured.compareAndSet(false, true)) {
try {
pc = borrowConnection(System.currentTimeMillis(),pc, null, null);
result = ConnectionPool.this.setupConnection(pc);
} catch (SQLException x) {
cause = x;
} finally {
latch.countDown();
}
} else {
//if we reach here, another thread is configuring the actual connection
latch.await(timeout,unit); //this shouldn't block for long
}
if (result==null) throw new ExecutionException(cause);
return result;
} else {
return null;
}
}
/**
* {@inheritDoc}
*/
public boolean isCancelled() {
return pc==null && (pcFuture.isCancelled() || cancelled.get());
}
/**
* {@inheritDoc}
*/
public boolean isDone() {
return pc!=null || pcFuture.isDone();
}
/**
* run method to be executed when cancelled by an executor
*/
public void run() {
try {
Connection con = get(); //complete this future
con.close(); //return to the pool
}catch (ExecutionException ex) {
//we can ignore this
}catch (Exception x) {
ConnectionPool.log.error("Unable to cancel ConnectionFuture.",x);
}
}
}
protected class PoolCleaner extends Thread {
protected ConnectionPool pool;
protected long sleepTime;
protected volatile boolean run = true;
PoolCleaner(String name, ConnectionPool pool, long sleepTime) {
super(name);
this.setDaemon(true);
this.pool = pool;
this.sleepTime = sleepTime;
if (sleepTime <= 0) {
log.warn("Database connection pool evicter thread interval is set to 0, defaulting to 30 seconds");
this.sleepTime = 1000 * 30;
} else if (sleepTime < 1000) {
log.warn("Database connection pool evicter thread interval is set to lower than 1 second.");
}
}
@Override
public void run() {
while (run) {
try {
sleep(sleepTime);
} catch (InterruptedException e) {
// ignore it
Thread.interrupted();
continue;
} //catch
if (pool.isClosed()) {
if (pool.getSize() <= 0) {
run = false;
}
} else {
try {
if (pool.getPoolProperties().isRemoveAbandoned())
pool.checkAbandoned();
if (pool.getPoolProperties().getMinIdle()<pool.idle.size())
pool.checkIdle();
if (pool.getPoolProperties().isTestWhileIdle())
pool.testAllIdle();
} catch (Exception x) {
log.error("", x);
} //catch
} //end if
} //while
} //run
public void stopRunning() {
run = false;
interrupt();
}
}
}