/*
* JBoss, Home of Professional Open Source.
* Copyright 2008, Red Hat Middleware LLC, and individual contributors
* as indicated by the @author tags. See the copyright.txt file in the
* distribution for a full listing of individual contributors.
*
* This is free software; you can redistribute it and/or modify it
* under the terms of the GNU Lesser General Public License as
* published by the Free Software Foundation; either version 2.1 of
* the License, or (at your option) any later version.
*
* This software 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 GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this software; if not, write to the Free
* Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
* 02110-1301 USA, or see the FSF site: http://www.fsf.org.
*/
package org.jboss.ejb.plugins;
import java.security.AccessController;
import java.util.ArrayList;
import java.util.Timer;
import java.util.TimerTask;
import org.jboss.deployment.DeploymentException;
import org.jboss.ejb.EnterpriseContext;
import org.jboss.logging.Logger;
import org.jboss.metadata.MetaData;
import org.jboss.metadata.XmlLoadable;
import org.jboss.monitor.Monitorable;
import org.jboss.monitor.client.BeanCacheSnapshot;
import org.jboss.util.LRUCachePolicy;
import org.jboss.util.loading.ContextClassLoaderSwitcher;
import org.w3c.dom.Element;
/**
* Least Recently Used cache policy for EnterpriseContexts.
*
* @see AbstractInstanceCache
* @author <a href="mailto:simone.bordet@compaq.com">Simone Bordet</a>
* @author <a href="mailto:bill@jboss.org">Bill Burke</a>
* @version $Revision: 81030 $
*/
public class LRUEnterpriseContextCachePolicy extends LRUCachePolicy
implements XmlLoadable, Monitorable
{
// Constants -----------------------------------------------------
// Attributes ----------------------------------------------------
protected static Logger log = Logger.getLogger(LRUEnterpriseContextCachePolicy.class);
protected static Timer tasksTimer;
static
{
// Don't leak the TCCL to the tasksTimer thread
ContextClassLoaderSwitcher clSwitcher = (ContextClassLoaderSwitcher) AccessController.doPrivileged(ContextClassLoaderSwitcher.INSTANTIATOR);
ContextClassLoaderSwitcher.SwitchContext clSwitchContext = null;
try
{
// Switches the TCCL to this class' classloader
clSwitchContext = clSwitcher.getSwitchContext(LRUEnterpriseContextCachePolicy.class.getClassLoader());
tasksTimer = new Timer(true);
}
finally
{
// Restores the TCCL
if (clSwitchContext != null)
clSwitchContext.reset();
}
log.debug("Cache policy timer started, tasksTimer="+tasksTimer);
}
/** The AbstractInstanceCache that uses this cache policy */
private AbstractInstanceCache m_cache;
/** The period of the resizer's runs */
private long m_resizerPeriod;
/** The period of the overager's runs */
private long m_overagerPeriod;
/** The age after which a bean is automatically passivated */
private long m_maxBeanAge;
/**
* Enlarge cache capacity if there is a cache miss every or less
* this member's value
*/
private long m_minPeriod;
/**
* Shrink cache capacity if there is a cache miss every or more
* this member's value
*/
private long m_maxPeriod;
/**
* The resizer will always try to keep the cache capacity so
* that the cache is this member's value loaded of cached objects
*/
private double m_factor;
/** The overager timer task */
private TimerTask m_overager;
/** The resizer timer task */
private TimerTask m_resizer;
/** Useful for log messages */
private StringBuffer m_buffer = new StringBuffer();
// Static --------------------------------------------------------
// Constructors --------------------------------------------------
/**
* Creates a LRU cache policy object given the instance cache that use
* this policy object.
*/
public LRUEnterpriseContextCachePolicy(AbstractInstanceCache eic)
{
if (eic == null)
throw new IllegalArgumentException
("Instance cache argument cannot be null");
m_cache = eic;
}
// Public --------------------------------------------------------
// Monitorable implementation ------------------------------------
public void sample(Object s)
{
if( m_cache == null )
return;
BeanCacheSnapshot snapshot = (BeanCacheSnapshot)s;
LRUList list = getList();
synchronized (m_cache.getCacheLock())
{
snapshot.m_cacheMinCapacity = list.m_minCapacity;
snapshot.m_cacheMaxCapacity = list.m_maxCapacity;
snapshot.m_cacheCapacity = list.m_capacity;
snapshot.m_cacheSize = list.m_count;
}
}
// Z implementation ----------------------------------------------
public void start()
{
if (m_resizerPeriod > 0)
{
m_resizer = new ResizerTask(m_resizerPeriod);
long delay = (long) (Math.random() * m_resizerPeriod);
tasksTimer.schedule(m_resizer, delay, m_resizerPeriod);
}
if (m_overagerPeriod > 0)
{
m_overager = new OveragerTask(m_overagerPeriod);
long delay = (long) (Math.random() * m_overagerPeriod);
tasksTimer.schedule(m_overager, delay, m_overagerPeriod);
}
}
public void stop()
{
if (m_resizer != null) {m_resizer.cancel();}
if (m_overager != null) {m_overager.cancel();}
super.stop();
}
public void destroy()
{
m_overager = null;
m_resizer = null;
super.destroy();
}
/**
* Reads from the configuration the parameters for this cache policy, that are
* all optionals.
* FIXME 20010626 marcf:
* Simone seriously arent' all the options overkill? give it another 6 month .
* Remember you are exposing the guts of this to the end user, also provide defaults
* so that if an entry is not specified you can still work and it looks _much_ better in
* the configuration files.
*
*/
public void importXml(Element element) throws DeploymentException
{
String min = MetaData.getElementContent(MetaData.getOptionalChild(element, "min-capacity"));
String max = MetaData.getElementContent(MetaData.getOptionalChild(element, "max-capacity"));
String op = MetaData.getElementContent(MetaData.getOptionalChild(element, "overager-period"));
String rp = MetaData.getElementContent(MetaData.getOptionalChild(element, "resizer-period"));
String ma = MetaData.getElementContent(MetaData.getOptionalChild(element, "max-bean-age"));
String map = MetaData.getElementContent(MetaData.getOptionalChild(element, "max-cache-miss-period"));
String mip = MetaData.getElementContent(MetaData.getOptionalChild(element, "min-cache-miss-period"));
String fa = MetaData.getElementContent(MetaData.getOptionalChild(element, "cache-load-factor"));
try
{
if (min != null)
{
int s = Integer.parseInt(min);
if (s <= 0)
{
throw new DeploymentException("Min cache capacity can't be <= 0");
}
m_minCapacity = s;
}
if (max != null)
{
int s = Integer.parseInt(max);
if (s <= 0)
{
throw new DeploymentException("Max cache capacity can't be <= 0");
}
m_maxCapacity = s;
}
if (op != null)
{
int p = Integer.parseInt(op);
if (p <= 0) {throw new DeploymentException("Overager period can't be <= 0");}
m_overagerPeriod = p * 1000;
}
if (rp != null)
{
int p = Integer.parseInt(rp);
if (p <= 0) {throw new DeploymentException("Resizer period can't be <= 0");}
m_resizerPeriod = p * 1000;
}
if (ma != null)
{
int a = Integer.parseInt(ma);
if (a <= 0) {throw new DeploymentException("Max bean age can't be <= 0");}
m_maxBeanAge = a * 1000;
}
if (map != null)
{
int p = Integer.parseInt(map);
if (p <= 0) {throw new DeploymentException("Max cache miss period can't be <= 0");}
m_maxPeriod = p * 1000;
}
if (mip != null)
{
int p = Integer.parseInt(mip);
if (p <= 0) {throw new DeploymentException("Min cache miss period can't be <= 0");}
m_minPeriod = p * 1000;
}
if (fa != null)
{
double f = Double.parseDouble(fa);
if (f <= 0.0) {throw new DeploymentException("Cache load factor can't be <= 0");}
m_factor = f;
}
}
catch (NumberFormatException x)
{
throw new DeploymentException("Can't parse policy configuration", x);
}
}
// Y overrides ---------------------------------------------------
/**
* Flush is overriden here because in this policy impl
* flush might not actually remove all the instances from the cache.
* Those instances that are in use (associated with a transaction) should not
* be removed from the cache. So, the iteration is done not until the cache is empty
* but until we tried to age-out every instance in the cache.
*/
public void flush()
{
int i = size();
LRUCacheEntry entry = null;
while (i-- > 0 && (entry = m_list.m_tail) != null)
{
ageOut(entry);
}
}
// Package protected ---------------------------------------------
// Protected -----------------------------------------------------
protected LRUList createList()
{
return new ContextLRUList();
}
protected void ageOut(LRUCacheEntry entry)
{
if( m_cache == null )
return;
if (entry == null)
{
throw new IllegalArgumentException
("Cannot remove a null cache entry");
}
if( log.isTraceEnabled() )
{
m_buffer.setLength(0);
m_buffer.append("Aging out from cache bean ");
m_buffer.append(m_cache.getContainer().getBeanMetaData().getEjbName());
m_buffer.append("with id = ");
m_buffer.append(entry.m_key);
m_buffer.append("; cache size = ");
m_buffer.append(getList().m_count);
log.trace(m_buffer.toString());
}
// This will schedule the passivation
m_cache.release((EnterpriseContext)entry.m_object);
}
protected void cacheMiss()
{
LRUList list = getList();
++list.m_cacheMiss;
}
// Private -------------------------------------------------------
private LRUList getList()
{
return m_list;
}
// Inner classes -------------------------------------------------
/**
* This TimerTask resizes the cache capacity using the cache miss frequency
* algorithm, that is the more cache misses we have, the more the cache size
* is enlarged, and viceversa. <p>
* Of course, the maximum and minimum capacity are the bounds that this
* resizer never passes.
*/
protected class ResizerTask extends TimerTask
{
private String m_message;
private StringBuffer m_buffer;
private long resizerPeriod;
protected ResizerTask(long resizerPeriod)
{
this.resizerPeriod = resizerPeriod;
m_message = "Resized cache for bean " +
m_cache.getContainer().getBeanMetaData().getEjbName() +
": old capacity = ";
m_buffer = new StringBuffer();
}
public void run()
{
// For now implemented as a Cache Miss Frequency algorithm
if( m_cache == null )
{
cancel();
return;
}
LRUList list = getList();
// Sync with the cache, since it is accessed also by another thread
synchronized (m_cache.getCacheLock())
{
int period = list.m_cacheMiss == 0 ? Integer.MAX_VALUE : (int)(resizerPeriod / list.m_cacheMiss);
int cap = list.m_capacity;
if (period <= m_minPeriod && cap < list.m_maxCapacity)
{
// Enlarge cache capacity: if period == m_minPeriod then
// the capacity is increased of the (1-m_factor)*100 %.
double factor = 1.0 + ((double)m_minPeriod / period) * (1.0 - m_factor);
int newCap = (int)(cap * factor);
list.m_capacity = newCap < list.m_maxCapacity ? newCap : list.m_maxCapacity;
log(cap, list.m_capacity);
}
else if (period >= m_maxPeriod &&
cap > list.m_minCapacity &&
list.m_count < (cap * m_factor))
{
// Shrink cache capacity
int newCap = (int)(list.m_count / m_factor);
list.m_capacity = newCap > list.m_minCapacity ? newCap : list.m_minCapacity;
log(cap, list.m_capacity);
}
list.m_cacheMiss = 0;
}
}
private void log(int oldCapacity, int newCapacity)
{
if( log.isTraceEnabled() )
{
m_buffer.setLength(0);
m_buffer.append(m_message);
m_buffer.append(oldCapacity);
m_buffer.append(", new capacity = ");
m_buffer.append(newCapacity);
log.trace(m_buffer.toString());
}
}
}
/**
* This TimerTask passivates cached beans that have not been called for a while.
*/
protected class OveragerTask extends TimerTask
{
private String m_message;
private StringBuffer m_buffer;
protected OveragerTask(long period)
{
m_message = getTaskLogMessage() + " " +
m_cache.getContainer().getBeanMetaData().getEjbName() +
" with id = ";
m_buffer = new StringBuffer();
}
public void run()
{
if( m_cache == null )
{
cancel();
return;
}
LRUList list = getList();
long now = System.currentTimeMillis();
ArrayList passivateEntries = null;
synchronized (m_cache.getCacheLock())
{
for (LRUCacheEntry entry = list.m_tail; entry != null; entry = entry.m_prev)
{
if (now - entry.m_time >= getMaxAge())
{
// Attempt to remove this entry from cache
if (passivateEntries == null) passivateEntries = new ArrayList();
passivateEntries.add(entry);
}
else
{
break;
}
}
}
// We need to do this outside of cache lock because of deadlock possibilities
// with EntityInstanceInterceptor and Stateful. This is because tryToPassivate
// calls lock.synch and other interceptor call lock.synch and after call a cache method that locks
if (passivateEntries != null)
{
for (int i = 0; i < passivateEntries.size(); i++)
{
LRUCacheEntry entry = (LRUCacheEntry) passivateEntries.get(i);
try
{
m_cache.tryToPassivate((EnterpriseContext) entry.m_object);
}
catch (Throwable t)
{
log.debug("Ignored error while trying to passivate ctx", t);
}
}
}
}
private void log(Object key, int count)
{
if( log.isTraceEnabled() )
{
m_buffer.setLength(0);
m_buffer.append(m_message);
m_buffer.append(key);
m_buffer.append(" - Cache size = ");
m_buffer.append(count);
log.trace(m_buffer.toString());
}
}
protected String getTaskLogMessage()
{
return "Scheduling for passivation overaged bean";
}
protected String getJMSTaskType()
{
return "OVERAGER";
}
protected long getMaxAge()
{
return m_maxBeanAge;
}
}
/**
* Subclass that logs list activity events.
*/
protected class ContextLRUList extends LRUList
{
boolean trace = log.isTraceEnabled();
protected void entryPromotion(LRUCacheEntry entry)
{
if (trace)
log.trace("entryPromotion, entry="+entry);
// The cache is full, temporarily increase it
if (m_count == m_capacity && m_capacity >= m_maxCapacity)
{
++m_capacity;
log.warn("Cache has reached maximum capacity for container " +
m_cache.getContainer().getJmxName() +
" - probably because all instances are in use. " +
"Temporarily increasing the size to " + m_capacity);
}
}
protected void entryAdded(LRUCacheEntry entry)
{
if (trace)
log.trace("entryAdded, entry="+entry);
}
protected void entryRemoved(LRUCacheEntry entry)
{
if (trace)
log.trace("entryRemoved, entry="+entry);
}
protected void capacityChanged(int oldCapacity)
{
if (trace)
log.trace("capacityChanged, oldCapacity="+oldCapacity);
}
}
}