/**
Copyright (C) SYSTAP, LLC DBA Blazegraph 2006-2016. All rights reserved.
Contact:
SYSTAP, LLC DBA Blazegraph
2501 Calvert ST NW #106
Washington, DC 20008
licenses@blazegraph.com
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; version 2 of the License.
This program 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 General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
/*
* Created on Jun 2, 2010
*/
package com.bigdata.quorum;
import java.rmi.Remote;
import java.util.UUID;
import java.util.concurrent.atomic.AtomicReference;
import org.apache.log4j.Logger;
/**
* Base class for {@link QuorumClient}s.
*
* @author <a href="mailto:thompsonbry@users.sourceforge.net">Bryan Thompson</a>
* @version $Id$
*/
abstract public class AbstractQuorumClient<S extends Remote> implements
QuorumClient<S> {
static protected final transient Logger log = Logger
.getLogger(AbstractQuorumClient.class);
private final AtomicReference<Quorum<?, ?>> quorum = new AtomicReference<Quorum<?, ?>>();
private final String logicalServiceZPath;
@Override
final public String getLogicalServiceZPath() {
return logicalServiceZPath;
}
/**
*
* @param logicalServiceZPath
* the fully qualified logical service identifier (for zookeeper,
* this is the logicalServiceZPath).
*/
protected AbstractQuorumClient(final String logicalServiceZPath) {
if(logicalServiceZPath == null)
throw new IllegalArgumentException();
this.logicalServiceZPath = logicalServiceZPath;
}
/**
* {@inheritDoc}
* <p>
*
* @return The reference from an atomic variable that will be cleared if the
* quorum terminates.
*/
@Override
public Quorum<?,?> getQuorum() {
final Quorum<?,?> tmp = quorum.get();
if (tmp == null)
throw new IllegalStateException();
return tmp;
}
@Override
public void start(final Quorum<?,?> quorum) {
if (quorum == null)
throw new IllegalArgumentException();
if (!this.quorum.compareAndSet(null/* expect */, quorum/* update */)) {
throw new IllegalStateException();
}
}
@Override
public void terminate() {
this.quorum.set(null);
}
/**
* {@inheritDoc}
* <p>
* The default implementation is a NOP.
*/
@Override
public void disconnected() {
}
@Override
public S getLeader(final long token) {
final Quorum<?,?> q = getQuorum();
q.assertQuorum(token);
final UUID leaderId = q.getLeaderId();
if (leaderId == null) {
q.assertQuorum(token);
throw new AssertionError();
}
return getService(leaderId);
}
@Override
abstract public S getService(UUID serviceId);
@Override
public void notify(QuorumEvent e) {
}
}