//$Id: UpdateTimestampsCache.java 10811 2006-11-15 14:44:34Z [email protected] $
package org.hibernate.cache;
import java.io.Serializable;
import java.util.Iterator;
import java.util.Properties;
import java.util.Set;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.hibernate.HibernateException;
import org.hibernate.cfg.Settings;
/**
* Tracks the timestamps of the most recent updates to particular tables. It is
* important that the cache timeout of the underlying cache implementation be set
* to a higher value than the timeouts of any of the query caches. In fact, we
* recommend that the the underlying cache not be configured for expiry at all.
* Note, in particular, that an LRU cache expiry policy is never appropriate.
*
* @author Gavin King
* @author Mikheil Kapanadze
*/
public class UpdateTimestampsCache {
public static final String REGION_NAME = UpdateTimestampsCache.class.getName();
private static final Log log = LogFactory.getLog(UpdateTimestampsCache.class);
private Cache updateTimestamps;
private final String regionName;
public void clear() throws CacheException {
updateTimestamps.clear();
}
public UpdateTimestampsCache(Settings settings, Properties props) throws HibernateException {
String prefix = settings.getCacheRegionPrefix();
regionName = prefix == null ? REGION_NAME : prefix + '.' + REGION_NAME;
log.info( "starting update timestamps cache at region: " + regionName );
this.updateTimestamps = settings.getCacheProvider().buildCache( regionName, props );
}
public synchronized void preinvalidate(Serializable[] spaces) throws CacheException {
//TODO: to handle concurrent writes correctly, this should return a Lock to the client
Long ts = new Long( updateTimestamps.nextTimestamp() + updateTimestamps.getTimeout() );
for ( int i=0; i<spaces.length; i++ ) {
if ( log.isDebugEnabled() ) {
log.debug( "Pre-invalidating space [" + spaces[i] + "]" );
}
//put() has nowait semantics, is this really appropriate?
//note that it needs to be async replication, never local or sync
updateTimestamps.put( spaces[i], ts );
}
//TODO: return new Lock(ts);
}
public synchronized void invalidate(Serializable[] spaces) throws CacheException {
//TODO: to handle concurrent writes correctly, the client should pass in a Lock
Long ts = new Long( updateTimestamps.nextTimestamp() );
//TODO: if lock.getTimestamp().equals(ts)
for ( int i=0; i<spaces.length; i++ ) {
if ( log.isDebugEnabled() ) {
log.debug( "Invalidating space [" + spaces[i] + "], timestamp: " + ts);
}
//put() has nowait semantics, is this really appropriate?
//note that it needs to be async replication, never local or sync
updateTimestamps.put( spaces[i], ts );
}
}
public synchronized boolean isUpToDate(Set spaces, Long timestamp) throws HibernateException {
Iterator iter = spaces.iterator();
while ( iter.hasNext() ) {
Serializable space = (Serializable) iter.next();
Long lastUpdate = (Long) updateTimestamps.get(space);
if ( lastUpdate==null ) {
//the last update timestamp was lost from the cache
//(or there were no updates since startup!)
//updateTimestamps.put( space, new Long( updateTimestamps.nextTimestamp() ) );
//result = false; // safer
}
else {
if ( log.isDebugEnabled() ) {
log.debug("[" + space + "] last update timestamp: " + lastUpdate + ", result set timestamp: " + timestamp );
}
if ( lastUpdate.longValue() >= timestamp.longValue() ) {
return false;
}
}
}
return true;
}
public void destroy() {
try {
updateTimestamps.destroy();
}
catch (Exception e) {
log.warn("could not destroy UpdateTimestamps cache", e);
}
}
public Cache getCache() {
return updateTimestamps;
}
public String getRegionName() {
return regionName;
}
public String toString() {
return "UpdateTimestampeCache";
}
}
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