GenericKeyedObjectPool.borrowObject(Object key) blocked for all threads until
_factory.makeObject(key) is finished
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Key: POOL-132
URL: https://issues.apache.org/jira/browse/POOL-132
Project: Commons Pool
Issue Type: Improvement
Affects Versions: 1.4
Reporter: Michael Mueller
Priority: Minor
If no Object is in the pool the method
GenericKeyedObjectPool.borrowObject(Object key) is blocking until a new Object
(_factory.makeObject(key) ) is created. This will block all other threads even
if they want an Object for a different key or want return an Object.
The GenericObjectPool.borrowObject() have a better implementation where the
_factory.makeObject(key) is called after the synchronized block.
Could this changed like this?
public Object borrowObject(Object key) throws Exception {
long starttime = System.currentTimeMillis();
for(;;) {
ObjectTimestampPair pair = null;
ObjectQueue pool = null;
synchronized (this) {
assertOpen();
pool = (ObjectQueue)(_poolMap.get(key));
if(null == pool) {
pool = new ObjectQueue();
_poolMap.put(key,pool);
_poolList.add(key);
}
// if there are any sleeping, just grab one of those
try {
pair = (ObjectTimestampPair)(pool.queue.removeFirst());
if(null != pair) {
_totalIdle--;
}
} catch(NoSuchElementException e) { /* ignored */
}
// otherwise
if(null == pair) {
// if there is a totalMaxActive and we are at the limit then
// we have to make room
if ((_maxTotal > 0) && (_totalActive + _totalIdle >=
_maxTotal)) {
clearOldest();
}
// check if we can create one
// (note we know that the num sleeping is 0, else we
wouldn't be here)
if ((_maxActive < 0 || pool.activeCount < _maxActive) &&
(_maxTotal < 0 || _totalActive + _totalIdle <
_maxTotal)) {
// allow new object to be created
} else {
// the pool is exhausted
switch(_whenExhaustedAction) {
case WHEN_EXHAUSTED_GROW:
// allow new object to be created
break;
case WHEN_EXHAUSTED_FAIL:
throw new NoSuchElementException();
case WHEN_EXHAUSTED_BLOCK:
try {
if(_maxWait <= 0) {
wait();
} else {
// this code may be executed again
after a notify then continue cycle
// so, need to calculate the amount of
time to wait
final long elapsed =
(System.currentTimeMillis() - starttime);
final long waitTime = _maxWait -
elapsed;
if (waitTime > 0)
{
wait(waitTime);
}
}
} catch(InterruptedException e) {
// ignored
}
if(_maxWait > 0 && ((System.currentTimeMillis()
- starttime) >= _maxWait)) {
throw new NoSuchElementException("Timeout
waiting for idle object");
} else {
continue; // keep looping
}
default:
throw new
IllegalArgumentException("whenExhaustedAction " + _whenExhaustedAction + " not
recognized.");
}
}
}
pool.incrementActiveCount();
}
// create new object when needed
boolean newlyCreated = false;
if(null == pair) {
try {
Object obj = _factory.makeObject();
pair = new ObjectTimestampPair(obj);
newlyCreated = true;
} finally {
if (!newlyCreated) {
// object cannot be created
synchronized (this) {
pool.decrementActiveCount();
}
}
}
}
// Activate. If activate fails, decrement active count and destroy.
// If instance failing activation is new, throw
NoSuchElementException;
// otherwise keep looping
try {
_factory.activateObject(key, pair.value);
} catch (Exception e) {
try {
_factory.destroyObject(key,pair.value);
synchronized (this) {
pool.decrementActiveCount();
}
} catch (Exception e2) {
// swallowed
}
if(newlyCreated) {
throw new NoSuchElementException(
"Could not create a validated object, cause: "
+ e.getMessage());
}
else {
continue; // keep looping
}
}
// Validate. If validation fails, decrement active count and
// destroy. If instance failing validation is new, throw
// NoSuchElementException; otherwise keep looping
boolean invalid = true;
try {
invalid = _testOnBorrow && !_factory.validateObject(key,
pair.value);
} catch (Exception e) {
// swallowed
}
if (invalid) {
try {
_factory.destroyObject(key,pair.value);
synchronized (this) {
pool.decrementActiveCount();
}
} catch (Exception e) {
// swallowed
}
if(newlyCreated) {
throw new NoSuchElementException("Could not create a
validated object");
} // else keep looping
} else {
return pair.value;
}
}
}
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