/*
* JBoss, Home of Professional Open Source
* Copyright 2006, Red Hat Middleware LLC, and individual contributors
* as indicated by the @author tags.
* See the copyright.txt in the distribution for a
* full listing of individual contributors.
* This copyrighted material is made available to anyone wishing to use,
* modify, copy, or redistribute it subject to the terms and conditions
* of the GNU Lesser General Public License, v. 2.1.
* This program is distributed in the hope that it will be useful, but WITHOUT A
* 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,
* v.2.1 along with this distribution; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
* MA 02110-1301, USA.
*
* (C) 2005-2006,
* @author JBoss Inc.
*/
/*
* Copyright (C) 2005,
*
* Arjuna Solutions Limited,
* Newcastle upon Tyne,
* Tyne and Wear,
* UK.
*
* $Id: RecoveryXids.java 2342 2006-03-30 13:06:17Z $
*/
package com.arjuna.ats.internal.jta.recovery.arjunacore;
import com.arjuna.ats.jta.xa.XidImple;
import java.util.*;
import javax.transaction.xa.*;
public class RecoveryXids
{
public RecoveryXids (XAResource xares)
{
_xares = xares;
_lastValidated = System.currentTimeMillis();
}
public boolean equals (Object obj)
{
if (obj instanceof RecoveryXids)
{
try
{
return ((RecoveryXids) obj)._xares.isSameRM(_xares);
}
catch (Exception ex)
{
}
}
return false;
}
/**
* Update our tracking with results of a new recovery scan pass
* @param trans the Xids seen during the new scan.
*/
public final void nextScan (Xid[] trans)
{
long currentTime = System.currentTimeMillis();
// record the new information:
if(trans != null) {
for(Xid xid : trans) {
XidImple xidImple = new XidImple(xid);
if(!_whenFirstSeen.containsKey(xidImple)) {
_whenFirstSeen.put(xidImple, currentTime);
}
_whenLastSeen.put(xidImple, currentTime);
}
}
// garbage collect the stale information:
Set<XidImple> candidates = new HashSet<XidImple>(_whenFirstSeen.keySet());
for(XidImple candidate : candidates) {
if(_whenLastSeen.get(candidate) != currentTime) {
// seen it previously but it's gone now so we can forget it:
_whenFirstSeen.remove(candidate);
_whenLastSeen.remove(candidate);
}
}
// gc note: transient errors in distributed RMs may cause values to disappear in one scan and then reappear later.
// under the current model we'll recover Xids only if they stick around for enough consecutive scans to
// span the safely interval. In the unlikely event that causes problems, we'll need to postpone gc for a given
// interval and take care to include only Xids seen in the most recent scan when returning candidates for recovery.
}
/**
* Return any Xids that should be considered for recovery.
* @return Xids that are old enough to be eligible for recovery.
*/
public final Xid[] toRecover ()
{
List<Xid> oldEnoughXids = new LinkedList<Xid>();
long currentTime = System.currentTimeMillis();
for(Map.Entry<XidImple,Long> entry : _whenFirstSeen.entrySet()) {
if(entry.getValue() + safetyIntervalMillis <= currentTime) {
oldEnoughXids.add(entry.getKey());
}
}
return oldEnoughXids.toArray(new Xid[oldEnoughXids.size()]);
}
public final boolean isSameRM (XAResource xares)
{
try
{
if (xares == null)
return false;
else
return xares.isSameRM(_xares);
}
catch (Exception ex)
{
return false;
}
}
public boolean contains (Xid xid)
{
XidImple xidImple = new XidImple(xid);
return _whenFirstSeen.containsKey(xidImple);
}
public boolean isStale() {
long now = System.currentTimeMillis();
long threshold = _lastValidated+(2*safetyIntervalMillis);
long diff = now - threshold;
boolean result = diff > 0;
return result;
}
/**
* If supplied xids contains any values seen on prev scans, replace the existing
* XAResource with the supplied one and return true. Otherwise, return false.
*
* @param xaResource
* @param xids
* @return
*/
public boolean updateIfEquivalentRM(XAResource xaResource, Xid[] xids)
{
if(xids != null && xids.length > 0) {
for(int i = 0; i < xids.length; i++) {
if(contains(xids[i])) {
_xares = xaResource;
_lastValidated = System.currentTimeMillis();
return true;
}
}
}
// either (or both) passes have an empty Xid set,
// so fallback to isSameRM as we can't use Xid matching
if(isSameRM(xaResource)) {
_xares = xaResource;
_lastValidated = System.currentTimeMillis();
return true;
}
return false;
}
// record when we first saw and most recently saw a given Xid. time in system clock (milliseconds).
// since we don't trust 3rd party hashcode/equals we convert to our own wrapper class.
private final Map<XidImple,Long> _whenFirstSeen = new HashMap<XidImple, Long>();
private final Map<XidImple,Long> _whenLastSeen = new HashMap<XidImple, Long>();
private XAResource _xares;
private long _lastValidated;
private static final int safetyIntervalMillis = 10000; // may eventually want to make this configurable?
}