Hello -
I recently observed in my prod system a case of GenericObjectPool not
respecting its limits. I had a pool of maxActive 10 that ultimately served out
objects to every single thread in my app server, ultimately bringing it down
when the pooled resource stopped responding. I have reproduced a small test
case that shows a pool with max size one that serves out more than one object
when hit by 5 concurrent threads. Hopefully I'm just doing something obviously
wrong. Any thoughts?
Ken
import org.apache.commons.pool.impl.GenericObjectPool;
import org.apache.commons.pool.PoolableObjectFactory;
import java.util.List;
import java.util.ArrayList;
import java.util.Random;
public class MaxActiveExceeded {
public static void main(String[] args) {
Pool pool = new Pool(); //just to instantiate
List<DoSomething> tlist = new ArrayList<DoSomething>();
for(int i = 0; i < 5; i++) {
DoSomething x = new DoSomething("" + i);
tlist.add(x);
}
for(DoSomething x : tlist) {
x.start();
try {
Thread.sleep(100);
} catch(InterruptedException e) {
e.printStackTrace(); //To change body of catch statement use
File | Settings | File Templates.
}
}
}
public static Object testBorrow() {
Object ctx = null;
try {
System.out.println("---Idle " + ImageNowConnectionPool.getNumIdle()
+ " Active " + ImageNowConnectionPool.getNumActive() + " : " +
System.currentTimeMillis());
ctx = Pool.getConnection();
Pool.releaseConnection(ctx);
} catch (Exception e) {
System.out.println("msg " + ctx + " -- " + e.getLocalizedMessage()
+ " : " + System.currentTimeMillis());
}
return ctx;
}
private static class DoSomething extends Thread {
private DoSomething(String name) {
super(name);
}
public void run() {
System.out.println("Thread running " + getName());
Object o = testBorrow();
System.out.println("Thread stopping " + getName() + ", object
returned - " + o);
}
}
private static class Pool {
private static final int MAXACTIVE = 1;
private static final long MAXWAIT = 500;
private static final int MAXIDLE = -1;
private static final int MINIDLE = 0;
private static final boolean TESTONBORROW = false;
private static final boolean TESTWHILEIDLE = false;
private static final boolean TESTONRETURN = false;
private static final long TIMEBETWEENEVICTRUNS = -1;
private static final int NUMTESTSPEREVICTRUN = 2;
private static final long MINEVICTABLEIDLETIME = -1;
private static final GenericObjectPool<Object> POOL = new
GenericObjectPool<Object>(new ObjectFactory(),
MAXACTIVE, GenericObjectPool.WHEN_EXHAUSTED_BLOCK, MAXWAIT,
MAXIDLE, MINIDLE,
TESTONBORROW, TESTONRETURN, TIMEBETWEENEVICTRUNS,
NUMTESTSPEREVICTRUN, MINEVICTABLEIDLETIME,
TESTWHILEIDLE);
public static Object getConnection(){
Object o = null;
try {
System.out.println("pre-borrow " + Thread.currentThread() + ":
Idle" + POOL.getNumIdle() + " Active " + POOL.getNumActive() + " : " +
System.currentTimeMillis());
o = POOL.borrowObject();
System.out.println("post-borrow " + Thread.currentThread() + ":
Idle" + POOL.getNumIdle() + " Active " + POOL.getNumActive() + " : " +
System.currentTimeMillis());
} catch (Exception e) {
System.out.println("****Error trying to borow - " +
Thread.currentThread() + ":" + e.getMessage() );
// System.out.println("borrow exception " +
Thread.currentThread() + ": Idle" + POOL.getNumIdle() + " Active " +
POOL.getNumActive() + " : " + System.currentTimeMillis());
// e.printStackTrace();
}
return o;
}
public static void releaseConnection(Object o){
try {
System.out.println("pre-release " + Thread.currentThread() + ":
Idle" + POOL.getNumIdle() + " Active " + POOL.getNumActive() + " : " +
System.currentTimeMillis());
POOL.returnObject(o);
System.out.println("post-release " + Thread.currentThread() +
": Idle" + POOL.getNumIdle() + " Active " + POOL.getNumActive() + " : " +
System.currentTimeMillis());
} catch (Exception e) {
e.printStackTrace();
}
}
}
private static class ObjectFactory implements PoolableObjectFactory<Object>
{
// returns a new connection to imagenow
public Object makeObject() {
Object retObj = null;
try {
retObj = login();
System.out.println("make obj" + retObj + " : " +
System.currentTimeMillis() + Thread.currentThread());
} catch (Exception e) {
e.printStackTrace();
}
return retObj;
}
public void destroyObject(Object obj) {
System.out.println("destroy obj" + obj + " : " +
System.currentTimeMillis() + Thread.currentThread());
}
public boolean validateObject(Object obj) {
boolean isValid = false;
if(obj == null) {
System.out.println("validation obj is null " +
Thread.currentThread());
} else {
try {
System.out.println("about to validate " +
Thread.currentThread());
Random r = new Random();
Thread.sleep(5000 + r.nextInt(20000));
isValid = true;
System.out.println("validate obj " + obj + " valid = " +
isValid + " : " + System.currentTimeMillis() + Thread.currentThread());
} catch (Exception e) {
e.printStackTrace();
}
}
return isValid;
}
public void activateObject(Object obj) {
System.out.println("activate" + obj + " : " +
System.currentTimeMillis() + Thread.currentThread());
}
public void passivateObject(Object obj) {
System.out.println("passivate" + obj + " : " +
System.currentTimeMillis() + Thread.currentThread());
}
/*-----------------------------------*/
private static Object login() throws Exception {
System.out.println("about to login " + Thread.currentThread());
Random r = new Random();
Thread.sleep(5000 + r.nextInt(20000));
System.out.println("login complete " + Thread.currentThread());
return new Object();
}
}
}
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