/*
* Hibernate Search, full-text search for your domain model
*
* License: GNU Lesser General Public License (LGPL), version 2.1 or later
* See the lgpl.txt file in the root directory or <http://www.gnu.org/licenses/lgpl-2.1.html>.
*/
package org.hibernate.search.backend.jgroups.impl;
import java.util.List;
import org.jgroups.Address;
import org.jgroups.Message;
import org.jgroups.View;
/**
* <p>This {@link NodeSelectorStrategy} picks a single master across all nodes participating
* in the JGroups cluster deterministically: this way all nodes in the group will
* have an agreement on which node is going to be the master.</p>
*
* <p>Advantage: if the master node fails, a new node is elected.</p>
* <p>Limitation: make sure all nodes in the group are having the same application running
* and use the same configuration, or the master might ignore incoming messages.</p>
*
* @author Sanne Grinovero (C) 2012 Red Hat Inc.
*/
public class AutoNodeSelector implements NodeSelectorStrategy {
private final String indexName;
private volatile Address localAddress;
private volatile Address masterAddress;
/**
* @param indexName the name of the index
*/
public AutoNodeSelector(String indexName) {
this.indexName = indexName;
}
@Override
public boolean isIndexOwnerLocal() {
return localAddress == null || localAddress.equals( masterAddress );
}
@Override
public void setLocalAddress(Address address) {
localAddress = address;
}
@Override
public void viewAccepted(View view) {
List<Address> members = view.getMembers();
if ( members.size() == 1 ) {
masterAddress = members.get( 0 );
}
else if ( members.size() == 2 ) {
// pick the non-coordinator
masterAddress = members.get( 1 );
}
else {
// exclude cluster coordinator (the first)
int selectionRange = members.size() - 1;
int selected = Math.abs( indexName.hashCode() % selectionRange ) + 1;
masterAddress = members.get( selected );
}
}
@Override
public Message createMessage(byte[] data) {
return new Message( null, localAddress, data );
}
}