Author: sandymac
Date: Sat Mar 25 23:13:22 2006
New Revision: 388880
URL: http://svn.apache.org/viewcvs?rev=388880&view=rev
Log:
Detect when making new objects is relatively slow or expensive.
When it is, try to anticipate demand and create idle objects
while allowing concurrent pool access. The idea came from a
discussion with Peter Steijn on ways to reduce pool latency.
Modified:
jakarta/commons/proper/pool/trunk/src/java/org/apache/commons/pool/composite/CompositeObjectPool.java
jakarta/commons/proper/pool/trunk/src/java/org/apache/commons/pool/composite/GrowManager.java
Modified:
jakarta/commons/proper/pool/trunk/src/java/org/apache/commons/pool/composite/CompositeObjectPool.java
URL:
http://svn.apache.org/viewcvs/jakarta/commons/proper/pool/trunk/src/java/org/apache/commons/pool/composite/CompositeObjectPool.java?rev=388880&r1=388879&r2=388880&view=diff
==============================================================================
---
jakarta/commons/proper/pool/trunk/src/java/org/apache/commons/pool/composite/CompositeObjectPool.java
(original)
+++
jakarta/commons/proper/pool/trunk/src/java/org/apache/commons/pool/composite/CompositeObjectPool.java
Sat Mar 25 23:13:22 2006
@@ -179,10 +179,10 @@
*/
public void addObject() throws Exception {
assertOpen();
+ final Object obj = factory.makeObject();
+ factory.passivateObject(obj);
synchronized (pool) {
- final Object obj = factory.makeObject();
- factory.passivateObject(obj);
- // if the pool is closed, discard returned objects
+ // if the pool was closed between the asserOpen and the
synchronize then discard returned objects
if (isOpen()) {
manager.returnToPool(obj);
} else {
Modified:
jakarta/commons/proper/pool/trunk/src/java/org/apache/commons/pool/composite/GrowManager.java
URL:
http://svn.apache.org/viewcvs/jakarta/commons/proper/pool/trunk/src/java/org/apache/commons/pool/composite/GrowManager.java?rev=388880&r1=388879&r2=388880&view=diff
==============================================================================
---
jakarta/commons/proper/pool/trunk/src/java/org/apache/commons/pool/composite/GrowManager.java
(original)
+++
jakarta/commons/proper/pool/trunk/src/java/org/apache/commons/pool/composite/GrowManager.java
Sat Mar 25 23:13:22 2006
@@ -19,6 +19,8 @@
import org.apache.commons.pool.PoolableObjectFactory;
import java.io.Serializable;
+import java.util.TimerTask;
+import java.util.Timer;
/**
* Grows the pool automatically when it is exhausted.
@@ -33,6 +35,11 @@
final class GrowManager extends AbstractManager implements Serializable {
private static final long serialVersionUID = 1225746308358794900L;
+ private static final Timer PREFILL_TIMER =
CompositeObjectPool.COMPOSITE_TIMER;
+
+ private final Object avgLock = new Object();
+ private long activateAvg = 0;
+ private long makeAvg = 0;
/**
* Retreives the next object from the pool, creating new objects if the
pool has been exhausted.
@@ -43,6 +50,8 @@
public Object nextFromPool() throws Exception {
assert Thread.holdsLock(objectPool.getPool());
Object obj = null;
+
+ final long startActivateTime = System.currentTimeMillis();
// Drain until good or empty
while (objectPool.getLender().size() > 0 && obj == null) {
obj = objectPool.getLender().borrow();
@@ -65,10 +74,15 @@
}
}
}
-
- if (obj == null) {
+ if (obj != null) {
+ updateActivateTimings(startActivateTime,
System.currentTimeMillis());
+ } else {
+ final long startMakeTime = System.currentTimeMillis();
obj = objectPool.getFactory().makeObject();
+ updateMakeTimings(startMakeTime, System.currentTimeMillis());
}
+
+ schedulePrefill();
return obj;
}
@@ -93,7 +107,74 @@
return obj;
}
+ /**
+ * Update the moving average of how long it takes to activate and validate
idle objects.
+ * @param start start of activation and validation
+ * @param end end of activation and validation
+ */
+ private void updateActivateTimings(final long start, final long end) {
+ final long elapsed = end - start;
+ if (elapsed > 0L) {
+ synchronized (avgLock) {
+ activateAvg = (activateAvg * 9L + elapsed) / 10L;
+ }
+ }
+ }
+
+ /**
+ * Update the moving average of how long it takes to make a new objects.
+ * @param start start of makeObject
+ * @param end end of makeObject
+ */
+ private void updateMakeTimings(final long start, final long end) {
+ final long elapsed = end - start;
+ if (elapsed > 0L) {
+ synchronized (avgLock) {
+ makeAvg = (makeAvg * 9L + elapsed) / 10L;
+ }
+ }
+ }
+
+ /**
+ * Does [EMAIL PROTECTED] PoolableObjectFactory#makeObject} take a
relativly long time compared to
+ * [EMAIL PROTECTED] PoolableObjectFactory#activateObject} and [EMAIL
PROTECTED] PoolableObjectFactory#validateObject}.
+ * @return <code>true</code> if [EMAIL PROTECTED]
PoolableObjectFactory#makeObject} takes a long time.
+ */
+ private boolean isMakeObjectExpensive() {
+ synchronized (avgLock) {
+ // XXX: This is a guess at an optimal balance.
+ // Considering makeObject to be expensive if it takes 3 times
longer than activation takes.
+ // That is based on a benchmark by Peter Steijn for database
connection pooling.
+ return activateAvg > 0L && activateAvg * 3L < makeAvg;
+ }
+ }
+
+ /**
+ * Schedule a <code>PrefillTask</code> if the idle object pool is empty
+ * and <code>makeObject</code> is relatively expensive.
+ */
+ private void schedulePrefill() {
+ if (objectPool.getLender().size() == 0 && isMakeObjectExpensive()) {
+ PREFILL_TIMER.schedule(new PrefillTask(), 0L);
+ }
+ }
+
public String toString() {
- return "GrowManager{}";
+ return "GrowManager{makeObjectExpensive=" + isMakeObjectExpensive() +
"}";
+ }
+
+ /**
+ * A <code>TimerTask</code> that will add another object if the pool is
empty.
+ */
+ private class PrefillTask extends TimerTask {
+ public void run() {
+ try {
+ if (objectPool.getNumIdle() == 0) {
+ objectPool.addObject();
+ }
+ } catch (Exception e) {
+ // swallowed
+ }
+ }
}
}
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